WO2007075732A2

WO2007075732A2 - Multifunctional temporary intra or extra-cardia pacemaker without fluoroscopy guidance for operation

Info

Publication number: WO2007075732A2
Application number: PCT/US2006/048507
Authority: WO
Inventors: Shou-Nian Fan
Original assignee: Shou-Nian Fan
Priority date: 2005-12-22
Filing date: 2006-12-20
Publication date: 2007-07-05
Also published as: WO2007075732A3

Abstract

A new type pacemaker with multifunctional pacing modes that can be used for temporary intra- or extra- single/dual chamber cardiac pacing is described. A LCD screen is integrated in this portable device to provide a real time electrocardiograph (ECG) monitoring. This device displays intra-chamber ECG that could guide physician to catheterize the heart without X-ray machine/fluoroscopy or other guiding equipment. It also can be used as an independent long-term surface ECG monitor. This device was built for the purposes of cost-effectiveness, safety, reliability and user friendliness. It is equipped with a clear-cut circuit design, a unique three level switching system for managing electrophysiological stimulation, interface of person/machine dialog, and cardiac signal recording. This multifunctional apparatus designed for multipurpose of clinical diagnosis and treatment fulfills and extends the clinical utilities of temporary cardiac pacing.

Description

Title: Multifunctional Temporary Intra or Extra-cardia Pacemaker without Fluoroscopy Guidance for Operation

DESCRIPTION

BACKGROUND

1. Field of the Invention

This invention is in the field of temporary pacemaker. This invention propels the temporary pacemaker to a higher level by eliminating the need of X-ray machine or other equipment's guidance in inserting leads to heart ventricle or atrium. This novel device combines single-chamber and dual-chamber capacities. Additionally, this novel and useful device has additional benefit of cost-effectiveness (less expensive than current models), better safety, more reliability and more user friendliness.

2. State of the Art

1) History of Pacemakers

Pacemakers are prescribed for people of all ages whose hearts beat too slowly. Pacemakers detect the slow heart rate and send electrical impulses to the heart to stimulate the heart muscle to beat faster. Well over 2 million pacemakers have been implanted worldwide since 1960.

The Early Years

Early External Pacemakers - The first pacemakers of the 1950s were not totally implanted in the body. One end of a small wire, called a "lead," was implanted into the heart. The other end of the lead was connected to an external pacemaker that was AC powered. One serious drawback—patients could go only as far as their extension cord and a power failure was a constant concern.

First Battery-Powered External Pacemaker - In 1957 the world's first transistorized, battery-powered, wearable pacemaker was developed. This gave patients mobility and eliminated concerns about a power failure.

196O's

First Human Implant of a Totally Implantable Pacemaker - The first human implant of a totally implantable pacemaker was in 1960. Its battery life was approximately 12-18 months.

Advances in Pacing Leads - In the mid-1960s, "transvenous leads," leads that could be inserted through a vein leading to the heart, replaced earlier leads that were attached to the outer surface of the heart. Pacemaker and lead implants could now be done without opening the chest cavity or using general anesthesia.

World's First "Demand" Pacemaker - "Demand" pacemakers, introduced in the mid- 1960s, sense when the heart is beating on its own and provide pacing only when necessary. Earlier pacemakers continuously paced the heart at a set "fixed" rate. All new pacemakers today are "demand" models.

1970's

Further Advances in the 1970s - New lead designs were developed to replace earlier "smooth tip" leads. Still used today, these new "tined" (pronged) leads and "active fixation" (screw-in type) leads provide a more secure attachment to the heart tissue and help prevent the lead from slipping out of place.

Extended Battery Life and New Casing - The introduction of a lithium iodine battery in 1975 greatly extended the pacemaker battery life (10+ years for some models) and replaced the mercury-zinc battery. Titanium casing was developed to enclose the battery and circuitry. Epoxy resin with silicone rubber previously encased the inner components. The new titanium casing (along with special filters) helps shield the components and greatly reduces outside electromagnetic interference. Patients with these newly designed pacemakers could now safely use microwave ovens and other appliances and equipment found in the home and office.

First Programmable Pacemakers - With the introduction of programmable pacemakers in the mid-1970s, pacemaker settings could be programmed using radio-frequency signals. This eliminated the need for surgery when/if any pacemaker programming adjustments were necessary.

First Dual-chamber Pacing - The first programmable pacemaker that could sense and pace the upper (atrium) and lower (ventricle) chambers of the heart was introduced in the late 1970s. Using two leads, dual-chamber pacemakers maintain synchronized timing between the upper and lower chambers of the heart to ensure efficient blood flow.

1980^fs

First Steroid-Eluting Lead - In the early 1980s, leads were made available that emit a steroid drug from the tip of the electrode. This drug suppresses inflammation of the heart wall.

Rate Responsive Pacing - Pacemakers with a "rate responsive" feature became available in the mid-1980s. A tiny crystal sensor inside the pacemaker detects body movement and its signals adjust the pacemaker rate up or down according to the wearer's activity.

1990's

Sophisticated Devices - In the 1990s, pacemakers operate like micro-computers, are smaller than earlier devices (1/2 the size), and can last much longer. With the recent introduction of "mode switching," devices can recognize an abnormally fast heart rate in the upper chamber of the heart and react by automatically changing the therapy the pacemaker delivers. This feature allows the pacemaker to deliver the most appropriate pacing therapy.

Adjusting to each person's activity. In the late 1990's, pacemakers can mimic the heart's natural rhythm even more closely by adjusting the rhythm according to a person's activity level.

More Useful Information. Pacemakers can now collect information and store it until the next clinic visit. Some pacemakers also make follow-up easier by storing patient data directly into the memory of the pacemaker (such as name, diagnosis, doctor).

2) History of Temporary Pacemakers

Transcutaneous External Cardiac Pacing

The concept of transcutaneous external cardiac pacing (TEP) has been present for over 200 years. However, transcutaneous pacing was not made practical until Zoll's work in the early 1950s. Technological improvements during the late 1980s made TEPs more comfortable and less cumbersome than early models. In subsequent studies, external pacing was found useful as a temporizing measure in patients with symptomatic bradycardia and a pulse but of little benefit in pulseless situations. They also may be of some benefit for overdrive pacing in treatment of certain tachycardias. American Heart Association Advanced Cardiac Life Support (AHA ACLS) guidelines recommend TEP as a temporizing measure for symptomatic bradycardia and as a consideration for asystole.

Early history

In 1791, Galvani reported that electrical current applied across the heart of a dead frog resulted in myocardial contraction. Building on this principal, Duchenne (1872) successfully resuscitated a child who had drowned, by attaching one electrode to a leg while rhythmically tapping the precordium with another electrode. Gould (1929) also reported successful resuscitation of a cardiac arrest patient using a self-designed transthoracic pacemaker. Hyman was the first to coin the term "artificial cardiac pacemaker." In 1932, he published the design of an external pulse generator for use in animals.

In 1952, ZoIl reported the successful use of subcutaneous (simultaneous precordial and transesophageal) needle electrodes in pacing 2 patients with ventricular standstill secondary to Morgagni-Stokes-Adams syndrome. He later reported the development and successful use of the first true transcutaneous pacemaker and monitor. This device used a pair of 3-centimeter metal electrodes secured to the chest wall and delivered 2- millisecond (msec), 120-volt, alternating current impulses.

Effect of transvenous pacemakers ' development

The introduction of permanent implantable transvenous pacemakers by Chardack, Furman, Senning, Elmqvist, Thevenet, Lillehei, and others in the late 1950s superseded the use of the more painful and cumbersome external models.

In 1981, ZoIl patented and introduced a transcutaneous external pacemaker with a longer pulse duration (40 msec) and a larger electrode surface area (80 cm²). This reduced the current requirement for capture and increased comfort for the patient. Additionally, this model could be applied much more rapidly than earlier TEPs, paving the way for renewed interest in TEPs. In 1982, the FDA approved use of the ZoIl TEP for patients with heart rates less than 40 beats per minute and asystole. The current AHA ACLS guidelines included the use of TEPs for symptomatic bradycardias.

Application

Application of the external pacemaker is simple. Electrodes/pads and monitor leads, if necessary, are placed on the patient. About 2-3 cm of space should be left if separate defibrillation pads are required, and the second pad should be placed posteriorly, just below the left scapula. The desired heart rate is chosen and the current is set to zero milliamperes (mA). The TEP is then turned on and the current is increased as tolerated until capture is achieved.

Pulse duration

Pulse duration is the time of impulse stimulation. Early TEPs used short (1-2 msec) duration impulses. Such impulses resembled the action potential and preferentially stimulated skeletal muscle. In contrast, cardiac muscle action potentials are much longer, requiring 20-40 msec to reach maximum. ZoIl^' found that increasing the duration from 1 to 4 msec resulted in a 3 -fold reduction in threshold (the current requirement for stimulation). Increasing the current from 4 to 40 msec further halves the threshold. Longer durations produced no further advantage. Current TEPs deliver 40 (ZoIl) or 20 (all others) msec pulses.

Current

External pacing in dogs requires 30-100 times greater than internal transvenous pacing. Human studies have shown that the average current necessary for external pacing is about 65-100 mA in unstable bradycardias and about 50-70 mA in hemodynamically stable patients and volunteers. At this current, more than 90% of patients tolerated pacing for 15 or more minutes. Animal studies have found that stimulation up to 10-20% over the threshold stimulates only the ventricles. Higher amounts are needed to stimulate the atria.

Using a longer pulse duration and larger electrodes permits patients to tolerate higher applied current. One hundred milliamperes of current applied over an average (50-ohm resistance) chest for 20 msec will deliver 0.1 Joules. This is well below the 1-2 Joules required to cause an uncomfortable tingling sensation in the skin. The force of skeletal muscle contraction, not the electric current, determines TEP discomfort. Current TEPs are capable of delivering up to 140-200 mA tolerably.

Electrodes Pain is a function of the current delivered per unit of area. Pain sensation is minimized by electrodes with a surface area of at least 5 cm . The amount of pain for a current of a given strength reaches a plateau once the electrode surface area exceeds 10 cm². Most commercially available electrodes are 80-100 cm². TEPs generally perform best with their own pads, but different combinations may be helpful. No study has evaluated the effects of body habitus or gender on tolerance of TEPs.

Monitor

Determination of electrical capture and pulse generation can be difficult when skeletal muscle is stimulated. In the 1950s, ZoIl developed a TEP with an ECG monitor that allowed for identification of electrical capture. Blanking protection, currently only available in ZoIl models, changes high output pacing stimulus to a smaller ECG waveform, preventing overdriving of the ECG. If blanking protection is not present, a second monitor or clinical palpation of the pulse is needed to determine capture.

Synchronous/asynchronous modes

In the fixed rate (asynchronous) mode, the TEP delivers an electrical stimulus at preset intervals, independent of intrinsic cardiac activity. In theory, this could induce arrhythmias if stimulation occurs during the vulnerable period of the cardiac cycle. Early models only had fixed-rate capabilities. Most current models have fixed rate and synchronous pacing. Synchronous pacing is a demand mode in which the pacer fires only when no complex is sensed for a predetermined amount of time. Pacing generally should be started in the synchronous mode.

Varghese reported that external pacing simultaneously stimulated all 4 heart chambers in dogs. Madsen, however, echocardiographically demonstrated in humans that atrial stimulation was retrograde without opening the mitral valve.

Studies have shown no difference in hemodynamics between transcutaneous and transvenous pacemakers, using comparable rates in complete heart block and cardiac arrest. The atrial-pacing threshold in humans is generally much higher than that for the ventricles; thus, current needed to stimulate all 4 chambers is not tolerated, even by sedated patients. This results in loss of the "atrial kick" and a reduction in cardiac output. Talit studied healthy volunteers and found, via Doppler measurements, that both stroke volume and cardiac output were reduced even when pacing at a rate 15-30% higher than the sinus baseline. Thus, external pacing must be used cautiously in patients with sinus bradycardia to ensure blood pressure is preserved.

Minimizing discomfort

Skeletal muscle contraction can be uncomfortable and is often the limiting factor in TEP use. Placing electrodes over areas of least skeletal muscle can minimize discomfort. Placement is generally best in the midline chest and just below the left scapula. The physician also should use the lowest effective current. Sedation should be considered if these measures are inadequate. Ultrasound has also been reported to assist in determining the lowest rate of capture.

Asystole

Most hospital and prehospital studies report no long-term survivors from asystole using external pacing. Small studies reported a 4% and 8% survival rate when TEP was initiated early in cardiac arrest. Survival rates ranging from 7-100% have been reported, albeit in studies with few subjects using TEPs early in bradyasystolic arrest. Many of these studies do not describe what other ACLS modalities were used. No pediatric patients in asystole have been reported to survive with external pacing.

Unstable/symptomatic bradycardias

Hemodynamically unstable bradycardias have 50-100% survival-to-discharge rates reported in prehospital and hospital settings. Two neonates with AV block who survived with the assistance of immediate external pacing have been reported.

Tachyarrhythmias Single and multiple beat pacing stimulation have been described as a useful treatment of tachycardias. The objective is to place a ventricular extrasystole during the vulnerable period of the cardiac cycle. More than 150 cases of successful overdrive pacing for tachycardias using TEPs have been noted. Overall termination rates for ventricular tachycardia reportedly have been between 57 and 95%; however, acceleration occurred in 4-26% of the reported attempts. Fisher reported termination in 57% and acceleration in 0.5% using single beat capture compared with 94% termination and 3.6% acceleration in 3.6% using multiple beat rapid burst attempts.

Transesophageal Pacing

Transesophageal pacing is a process in which an esophageal pacing lead is inserted via the nostrils into the esophagis, as in the insertion of a nasogastric tube. The proximity of the esophagus to the atria makes it an ideal location for the recording of electrical activity from the atrium and for Transesophageal pacing. The optimal Transesophageal pacing site is determined by using the unipolar esophago-atrial electrogram. Pacing is performed with a programmed stimulator capable of delivering currents of up to 12-18 mM with a pulse -width of 8-10 msec. The entire procedure generally lasts less than 10 minutes.

Atrial flutter and many types of supraventricular tachyarrhythmias (SVT) are examples of tachyarrhythmias which occur as a result of reentry. Transesophageal pacing can be used to terminate such tachyarrhythmias by interrupting the reentrant pathways. Studies have demonstrated that successful termination of reentrant SVT can be accomplished using Transesophageal pacing in the majority of cases. In most cases, Transesophageal pacing can successfully convert atrial flutter into sinus rhythm (ref. 27).

3) Inventor's Pacemaker History

In 1979, Dr. Shounian Fan, the inventor of this novel device pioneered applying transesophageal pacing technique to terminate PSVT by using our own designed catheter leads and stimulator (ref. 1, 2). In 1983, we discovered that by increasing the stimulating pulse width to 10 ms, it could reduce the pacing voltage significantly. This methodology improvement resulted reduction of the discomfort in esophagus following pacing treatment (ref. 3, 4, 5, 6). In 1984, we independently designed and built a CT-I model programmed cardiac stimulator based on CMOS circuits for transesophageal cardiac pacing study. By using this stimulator, we speed up our noninvasive esophageal cardiac pacing research on the cardio-electrical physiological basis of PSVT and the mechanism to terminate PSVT (ref. 5, 6, 7). In 1985, we studied the bandwidth components and frequency spectrum of esophageal ECG, and the methodology to record esophageal ECG (ref. 4). Moreover, the inventor independently designed and built a cardio conversion device and electrical lead system for transesophageal low-energy pacing in 1989, and completed animal experiment and clinical application for PSVT, atrial flutter (AF) and atrial fibrillation (Af) cordioconversion (ref. 8, 9).

Based on our own research and clinical experience, we have innovatively developed several lines of electronic products to fulfill the needs of clinical diagnosis and treatment of cardiac arrhythmia (ref. 9, 10, 12). Since 1987, the inventor has built several models of portable devices to treat tachycardia by means of transesophageal atrial pacing with fixed high frequency pulses to terminate PSVT. The clinical trial has shown very satisfactory results (ref. 9, 10, 12). Two of the devices FYC-II and FYC-III model stimulators obtained Chinese National Patent (ZLOO 109923.x) in 2004.

In 1990, the inventor developed electrocardiophysiological signal and stimulating pulse-switching device, which can be connected to a multi-lead and multi-channel physiological recorder. In 1992, the inventor built a limiting amplitude device for electrocardiophysiological and ECG signal recoding during intra-/extra-cardiac stimulation (ref. 11, 13). This device greatly improved ECG recording quality and met the clinical demands on high quality ECG for diagnosis purpose. In 1997, the inventor made a portable cardiac programmed stimulator with a pull down menu on LCD screen. This new device totally differed from the conventional cardiac programmed stimulator. It was a portable, multifunctional and easy to use programmed stimulator for both clinicians and electro-cardiophysiologists. This device was issued a Chinese National Patent (ZLOOl 13102.7).

During 1998-2000, the inventor developed MCS desktop model multi-functional cardiac programmed stimulator, which can be used for both intra- and extra cardiac (transesophageal) stimulation and obtained the Chinese National Patent (ZLOOl 13102.8). During 2001-2002, we independently developed a palm-size ECG monitoring device, and fixed frequency cardiac pacing device with LCD monitoring system. Both devices have been applied in clinics successfully.

4) Current Status of Temporary Pacemaker

At present, Medtronic Inc. USA produces the most advanced temporary cardiac pacemaker (pulse generator) and occupies the largest market share in the world. The two most current models Medtronic Inc. manufactured are 1). Single-Chamber Model 5348 External (Temporary) Pulse Generator with VOO/VOO and VWAAl pacing functional modes, and 2). Dual-Chamber Model 5388 External (Temporary) Pulse Generator with AOO/VOO, AAI/ VVI, DOO, DVI, DDI and DDD pacing functional modes.

Other companies made similar external pulse generators but the quality and market share are not as dominant as the Medtronic Inc. products. All the current conventional external pulse generators only designed for intra-cardiac pacing, and required additional equipments (X-ray machine or fluoroscopy for inserting catheter and equipment to monitor ECG) to complete the cardiac pacing needs. Further, it only applied to conditions that require emergent cardiac pacing before implantable cardiac pacemaker was placed. In addition, these newer model's external pulse generators are expensive.

SUMMARY OF THE INVENTION It is an object of the invention to integrate a LCD screen into the temporary cardiac pacing device for real time ECG recording. This LCD display has a great value in clinical practice. During ECG display, the LCD screen has functions of ECG freezing, scan speed and gain adjustment, and heart rate display. In addition, this LCD screen also serves as an interface to set pacing mode and parameters via a person to computer dialog box on the screen. For instance, setting, adjusting, and confirming important parameters (such as; pacing mode, pacing site, pacing frequency, pulse width, PA-PV intervals) can be accomplished on the LCD display. With this integrated LCD design, clinicians can perform cardiac catheter lead insertion at the bedside under the guidance of intra-chamber ECG. This procedure can be carried out even without X-ray machine or fluoroscopy. This novel clinical utility may extend the application of temporary cardiac pacemaker in clinics, and raise the market potential of this pacing technique and its related equipment.

It is a further object of the invention to be combined with multi-functional pacing modes for clinical intra- and extra-cardiac pacing needs. The integrated LCD screen can be used for choosing pacing function and setting pacing parameters. After choosing pacing function and setting parameters, the LCD screen can be used to monitor real time ECG and guide the insertion of pacing leads in position. Further, the LCD display can be used to monitor pacing ECG. If our device is not used for temporary cardiac pacing, it can be used as a portable, mobile independent ECG monitor system.

It is a further object of the invention to integrate the extra-cardiac (transesophageal) pacing function into a temporary cardiac pacing device. Our device provides an option, a non-invasive pacing technique for clinicians. Since we are the pioneers to apply this technique in China, we have applied the transesophageal cardiac pacing in many clinical fields, such as cardiology, interventional cardiology, cardiovascular surgery, OBGYN, operating room, emergency room, and emergency rescue for total about 400 cases. The results show that the transesophageal cardiac pacing is a reliable, safe and has less side-effect procedure to terminate selected cardiac arrhythmia.

It is a further object of the invention to integrate the LCD screen into our device, we also added a port for recording surface ECG. Thus, our device is capable of recording both intra-chamber ECG (within the heart), and body surface ECG. Signal source selection can be completed on the LCD display manually. This function provides option to monitor the heart and increases the chance to obtain high quality ECG recording.

It is a further object of the invention to build a multi-level switching system to manage electrical traffic generated by stimulating pulse delivery and intra-cardiac (or esophageal) ECG signal sensing. This unique switching system was consisted of computer software-controlled three level ON/OFF circuits that were located at different positions of ECG amplifiers. At different temporal phase, this switch system produced different ON/OFF state to prevent amplifier damage due to large tissue after potential generated by wide pulses during transesophageal cardiac pacing. This switch system guaranteed the normal working condition and the functional integration of the amplifiers during transesophageal temporary cardiac pacing.

It is a further object of the invention to design and build in a mechanism that sensing both intra-/extra (esophageal)-cardiac ECG signals and body surface ECG signals while this device is working under single chamber pacing mode. The ECG signal source can be chosen via a function bar under pacing parameters on LCD screen. This unique function assures TTL (negative) signal stability during signal sensing, especially, this function offers more advantage during transesophageal temporary cardiac pacing. While there is a poor esophageal signal sensing, the operator can switch to intra-cardiac ECG sensing to get better ECG signal recording.

It is a further object of the invention to provide several interfaces for user to choose from; such as: sense position, LCD display position, body surface ECG amplifying and connectors and so on. Our device provides the hardware support for multipurpose use of pacing technology in clinics.

It is a further object of the invention to provide a new methodology in designing temporary cardiac pacemaker. For example, we integrated the LCD screen with our device, we can monitor the intra-chamber ECG at a real time basis, that allows physicians to insert the catheter leads into the heart chambers at the bedside without an X-ray machine. During the temporary cardiac pacing, LCD screen can be set to receive the electrical cardiac signals from the body surface to monitor the pacing condition.

It is a further object of the invention to design both in structure and electrical circuits a novel, flexible and straight-forwarded model, to package multi-functional utilities within a portable device. All of the above can lower the production cost, and easily add on more extra functions and upgrade our design.

Our innovative device solved the following problems of current temporary pacemakers. The conventional cardiac pacemakers (both the temporary and permanent) receive signals and send stimulating pulses within the heart chamber. Thus, the electrical signals generated from the myocardia have large amplitude values and small impedance (only ~80-500 Ω). The stimulating pulses sending to the myocarda have low altitude values (0.5-2 V) and small width of the pulses (0.5-1 ms). Therefore, the design for amplifying ECG signals and managing the signal/pulse switching system are easy. Our invention added a transesophageal pacing function (extra-cardiac pacing) that shares the same channel of ECG amplifier with intra-cardiac pacing. This made the amplifier design very challenging since the esophageal ECG signals have very small amplitude values (<1 mV), and large unstable impedance (about ~200 K-IM Ω). In addition, the esophageal ECG signals are interfered by many other factors. The stimulating pulses for the transesophageal pacing have high pulse amplitude values (18-50 V), and wide width of pulses (9-12 ms), further, the after potential produced by the heart following the stimulation is larger and last longer. These factors increase degree of difficulty to design the amplifier. After many modeling test in the laboratory and in clinics, we independently designed computer software and related hardware controlled circuits that consisted with three levels OFF/ON switching systems to solve the above-mentioned problem. Our design is able to avoid the obstruction of electrical trafficking within the amplifier and safe guard the ECG signal sensing and recording during transesophageal cardiac pacing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE l. PACE 2006 Hardware Structure

FIGURE 2. CPUl Data Acquisition and Display Flow Chart

FIGURE 3. CPU1&2 Communications Flow Chart

FIGURE 4. Models: PACE2006 and PACE140 Portable Temporary Pacemakers

DETAILED DESCRIPTION OF THE INVENTION

In 1992, We invented Fyc-I/II/III device to treat paroxysmal supraventricular tachycardia (PSVT) by using overdrive suppression via transesophageal atrial pacing. In 1999, based on the clinical need, we creatively developed a non-invasive (transesophageal) prototype device that performed all the pacing functions of the invasive temporary cardiac pacing. It has been successfully applied in clinics. In 2001, we found that physicians relied on X- ray machine to install temporary cardiac pacemaker in clinics, we invented a temporary pacing device with ECG monitoring function, that could indicate the catheter lead position (by ECG signal originated from the atrium or ventricle), this could be applied for bedside catheterization without X-ray machine during emergency. We built a prototype device and successfully used in clinics.

Started from 2002, we innovatively developed a portable temporary cardiac pacing device with multifunctional pacing modes (AOO/ VOO, AAI/VVI, VAT and DVI), and intra-cardiac chamber or transesophageal pacing functions, also integrated with ECG monitoring on a built in LCD screen. We finished the prototype device in March 2005 and successfully tested in clinics.

The present invention extended the application of available technology of temporary cardiac pacing. Our invention provides novel designs in structure and creates a unique multifunctional temporary cardiac pacing device described in details as the follows:

(1). Our invention differs from the currently available temporary cardiac pacemaker or pulse generators. In structure design, we innovatively integrated a LCD screen into our portable pacing device that displays a single channel ECG signal. In circuit design, we applied a dual channel preamplifier system to better handle the electrical signal trafficking. During single chamber temporary cardiac pacing, one channel is able to receive intra-cardiac chamber ECG signal, and another channel received surface ECG signal simultaneously. Under dual chamber temporary cardiac pacing (less used in clinics), the dual channel preamplifier system can be used for dual chamber ECG signal sensing and displaying. Especially, during single chamber temporary cardiac pacing (commonly used in clinics), our device provides two forms of sensing mechanisms (can be selected manually); sensing via intra-cardiac chamber lead, or via body surface leads (under WI mode). This unique function assures the reliability of sense signal input, such dual sensing mechanism has not been reported previously in the temporary cardiac pacing device.

We also innovatively built a manual switch for choosing the ECG signal input source (Intra- or extra-cardiac) for displaying on LCD screen. This unique function allows clinicians to insert catheter into the heart without X-ray equipment. Under intra-cardiac ECG mode, operator can insert the heart catheter into cardiac chamber by watching the shape of ECG (signals from atrium or ventricle shown different shape) on the LCD screen. After the intra-chamber leads are in the desire place and started pacing function, LCD ECG signal can be switched to surface ECG recording for long term monitoring.

It is worthwhile to mention that our device can be used as a small, mobile and portable ECG monitoring device while the temporary cardiac pacing function is not in use. There are two methods for ECG signal input; A. ECG leads (1-1.5 m in length) connected with the patient's body surface for long term monitoring; B. On the back of our device, there is three lead buttons, in emergency, physicians can just put the device on the left chest (near the apex area of the heart) to view ECG information on the LCD screen without extra-ECG leads.

(2). We creatively incorporated non-invasive transesophageal cardiac pacing function into our device. This expands our device function in applying the noninvasive temporary cardiac pacing technology in clinics, and this is an important new feature and uniqueness of our device over the current conventional temporary cardiac pacemaker. We invented a low cost and energy saving switching power supply system with CMPS time base circuit, which provides 0- 10 V to intra-cardiac pacing, and 0-50 V for extra-cardiac pacing (transesophageal). In our prototype, the power switch is controlled manually on the surface board for intra-/extra-cardiac pacing section. We have used temporary intra-cardiac pacing in clinics under VOO/ AOO, VVI/ AAI₅ VAT and DVI stimulating modes in our device. The clinical results were very satisfactory. Since other temporary cardiac pacemakers or pulse generators can produce same stimulating function and there are abundant literatures to deal with the intra- cardiac pacing. We will not discuss the intra-cardiac pacing in further details; instead, we will emphasize the extra-cardiac pacing and its application with our device.

In clinical practice, paroxysmal supraventricular tachycardia (PSVT) is a common emergent condition. It is an emergent condition in clinics due to PSVT impact on circulation. The physician can rapidly inserted a catheter with pacing lead near the tip end into the esophagus, through the catheter lead, clinicians can monitor the esophageal ECG and send stimulating pulses for treatment via this esophageal catheter. When ECG shows P wave >R wave (A wave >V wave), the larger the P:R ratio; the better indicative the lead by the left atrium level, and the lower pacing threshold for the stimulating pulses, the operator can use AOO mode to generate an overdrive suppression rate, generally, only, needs 2-5 sec to terminate PSVT episode. The whole process from initiating PSVT to terminate by transesophageal cardiac pacing and reverted to normal sinus rhythm can be displayed on the built in LCD screen. This temporary extra-cardiac pacing function (transesophageal) has great clinical application potentials due to it is easy to use, safe, reliable, and quick to obtain treatment effects. Our portable device can be a useful tool for many clinical settings.

Another application of transesophageal cardiac pacing technique is to protect patients from life-threatening arrhythmia during surgical procedure. To prevent the slow heart rate (bradycardia) caused life-threatening events during anesthesia and surgical procedure, an esophageal pacing lead can be inserted in bradycardia patients who have sinus-atrium transduction block (S-AB), but no atrium- ventricle transduction block (A-VB) prior anesthesia. Esophageal ECG can be monitored on the LCD screen. In case the bradycardia occurs, the operator can use AOO or AAI pacing modes to prevent the risk of bradycardia. Our device also can be used as an independent and portable ECG monitoring system, it is important equipments for ambulance, rescue helicopter, emergency room and doctor's office for emergence pacing needs.

(3). In order to fulfill the functional condition of both intra-cardiac and extra- cardiac pacing (transesophageal), and to maintain our device to a portable size with low cost, we designed a common channel for the preamplifiers that manage the signal source from intra-cardiac, extra-cardiac (esophageal) or body surface. Thus, there were many difficulties in designing of the preamplifier and the integrated electrical circuits. The electrical signals generated from the intra- cardiac have small input impedance (only -80-500 Ω) and large amplitude values (~2-4 mV); however, the esophageal ECG signals have large input impedance (~30~200 KΩ and higher) and very small amplitude values (<1 mV). The interference of esophageal ECG is larger than that intra-cardiac. Therefore, the pacing voltage threshold is about 10-20 times higher in the esophagus than intra-cardiac. Further, the pulse width for transesophageal cardiac pacing is about 10 times wider than that intra-cardiac. Since the distance of pacing lead in the esophagus to the heart is longer, transesophageal cardiac pacing causes a larger distributed electrical capacitance, larger after potential and longer stimulating duration than intra-cardiac pacing. All these factors greatly affect the normal working condition of the preamplifiers. Moreover, the more important problems are the input port of the preamplifier directly facing 1) bioelectrical signal sensing from the heart and 2) stimulating pulses delivering to the heart. While the stimulating pulses are delivered to the heart, the heart electrical signals from the stimulating pulses are also directly imported into the input port of preamplifiers. It is a problem that causes pre-amplifiers malfunction and cannot be tolerated.

To solve the aforementioned problems, we did the folio wings: (1). Using Intra-cardiac/OFF/Extra-cardiac switch on the face board to change the input impedance manually; 400-500 KΩ for intra-cardiac chamber, and 1.5- 2.2 MΩ for extra-cardiac (transesophageal) pacing.

(2). Using Intra-cardiac/OFF/Extra-cardiac switch on the face board to change the gain of preamplifier; 40 times for intra-cardiac chamber, and 120 times for extra-cardiac (transesophageal).

(3). Using microprocessor to control the temporary intra-/extra-cardiac pacing condition, and change the band width frequency of the amplifier; 40-400 Hz for intra-cardiac chamber, and 30-200 Hz for extra-cardiac (transesophageal). (4). When our temporary cardiac pacing device is working under either intra- or extra-cardiac pacing (transesophageal) condition, the preamplifier port is responsible for ECG signal sensing and stimulating pulse delivery, in addition, this port also is connected to bioelectric load from patient (ref. Diagram 1 for detail). Therefore, the input port of preamplifier receives bioelectric signals from patient and signals of stimulating pulses via the pacing leads simultaneously. How to avoid the signals of stimulating pulses to reach the input port of preamplifier is critical for our device. After many laboratory tests and clinical trials, we independently designed- computer-controlled circuits that consisted of a three level OFF/ON switching system to make instantaneous short/open circuit. The first level switch is located in the front port of the preamplifiers (ref. Diagram 1 for detail). We use a field effect transistor that is consisted of three electrodes (Grid, Drain and Source) to build a switching system. During stimulating pulse delivery, the field effect transistor forms a high resistant shut- off condition to both the drain and source electrode at the front port of preamplifiers for the following duration: 10 ms prior to stimulating pulse delivery; plus the pulse duration and 50 ms post the pulse delivery (For instance, if the stimulating pulse is 10 ms, the total shut off duration=70 ms. When there are no stimulating pulses, the grid electrode is at a high electrical level and the drain and source electrode are at a low impedance state (~18 Ω). This allows bioelectrical signal passing. The second level switch is placed behind the emitter follower; a high fidelity analogue switch chip made by Maxim Co. USA carries out the switch function. During stimulating pulse delivery, the analogue switch chip not only forms high resistant state at the pre- and post-amplifying, but also short-circuits the input port of amplifier located behind the switch to the ground. The duration of the shut-off is the same as the first switch level (if the stimulating pulse is 10 ms, total duration=70 ms). The third level switch is placed at the most end of exporting port of ECG amplifier, before formation of TTL electrical level of the signal sensing circuit, and there is a coupling capacitance between the third level switching systems (ref. Diagram 1 for detail). During stimulating pulse delivery, the switch circuits simultaneously grounds the two electrodes of coupling capacitance instantaneously via the drain and source electrodes of two field effect transistors. When there is no stimulating pulse delivery, the switch circuit will form a high resistant state to the ground at the two electrodes of coupling capacitance. The third level switch system is similar to the first level switch system also relies on the field effect transistor to complete the switching function by controlling the drain and source electrode. Yet, the temporal phase of the third level switch is a bit different from the first and second level switching system, its post pulse duration is 60 ms instead 50 ms in the first and second level switching systems (for example, if the stimulating ^• pulse is 10 ms, the third level shut-off duration=80 ms). Furthermore, the third level switching system is to form a short circuit to the ground at the two electrodes of the coupling capacitance, which is different from first and second level switching systems.

In the aforementioned three level switching systems, the ON/OFF condition for stimulating pulses and bioelectrical signals are controlled by a negative TTL electrical level that has a pulse width wider than the pacing pulse width. The corresponding control electrical circuits and microprocessor#2 (CPU 2) provide the negative TTL electrical level that is exported from CTRLl and CTRL2 port of the CPU2. Each control signal exporting is 10 ms prior the synchronized stimulating pulse exporting. After stimulating signal delivery, the control signals exported from CTRLl and CTRL2 ports have 40 ms and 60 ms delay respectively. Results from our laboratory testing and clinical trials proved that our switch controlling procedures prevent the destructive effect of stimulating pulse delivery on the functional integration of preamplifiers, and avoid the sensing error caused by over-sized stimulating pulses and after potential generated by human body following receiving the stimulating pulse delivery.

References

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8. Fan S.N. et al. Transesophageal low-energy cardioconversion in an animal model of life-threatening tachycardia arrhythmias. Circulation. 80:1354-1359, 1989. 9. Fan S.N. et al. Terminating atrial fibrillation with transesophageal Low energy cardioconvesion in an animal model. Tienjing Medicine. June, 1990.

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US Patent number: Issued date: Inventers: Class#:

6615073 Sep., 2003 Panescu et al. 600/609

6141589 Oct., 2000 Duhay et al. 607/10

5766244 Jun., 1998 Alferness et al. 607/4

5626621 May, 1997 Skoglund et al. 607/10

5304209 Apr., 1994 Adams et al. 128/4.19

5123419 Jun., 1992 Platt et al. 128/697

5088490 Feb., 1992 Pagliolo et al. 128/419

5050600 Sep., 1991 Parks et al. 607/10

4577633 Mar., 1986 Berkovits et al. 607/15

4401119 Aug., 1983 Herpers 128/149

4142533 Mar., 1979 Brownlee et al. 607/27 EXAMPLES

1) Prototype Models

The prototype models are shown in Figure 4, Pace2006 and Pace 140.

We have our prototype device completed on March, 2005, the basic function and parameters are as the follows:

1. The pacing modes for intra-cardiac pacing: AOO/VOO, AAWVI, VAT, DVI.

2. The pacing modes for extra-cardiac pacing (transesophageal): AOO/VOO, AAI/VVI, VAT, DVI.

3. LCD ECG display functions: display intra-cardiac ECG including atrial ECG and ventricular ECG, display intra-esophageal ECG (esophageal ECG), display body surface ECG.

4. Emergent intra-cardiac chamber pacing function: pacing frequency= 70 ppm,

5. Sense signal source selection function; including intra-cardiac chamber signals, transesophageal signals, and body surface signals.

6. ECG signal source display selection function; intra-cardiac chamber ECG, transesophageal ECG, and body surface ECG.

We named the prototype PACE 2006. The testing instrument is Fluck 123 digital oscilloscope and Fluck 17 universal meter (Fluck Co. USA). The main pacing parameters are the following: (1). AOO/VOO mode:

Frequency: 30 ppm <FSlSl<600 ppm, default value 75 ppm, error<5%; Voltage: Intra-cardiac: 0-10 V continuing adjustable, error <5%; Extra-cardiac: 0-50 V continuing adjustable, error <5%;

Pulse width: Intra-cardiac: 0.5, 1.0, 1.5, 2.0 ms, default value 1.0 ms, error<5%; Extra-cardiac: 10-40 ms continuing adjustable, error <5%; (2). AAI/VVI mode:

Frequency: 30 ppm <FS1S1<15O ppm, default value 75 ppm, error<5%;

Voltage: Intra-cardiac: 0-10 V continuing adjustable, error <5%;

Extra-cardiac: 0-50 V continuing adjustable, error <5%; Pulse width: Intra-cardiac: 0.5, 1.0, 1.5, 2.0 ms, default value 1.0 ms, error<5%;

Extra-cardiac: 10-40 ms continuing adjustable, error <5%; There is 200 ms artificial refractory period after each pulse delivery.

(3). VAT mode:

Frequency: 30 ppm <FS1S1≤15O ppm, default value 75 ppm, error<5%; Voltage: Intra-cardiac: 0-10 V continuing adjustable, error <5%;

(4). DVI mode:

Frequency: 30 ppm <FS1S1<15O ppm, default value 75 ppm, error<5%; Voltage: Intra-cardiac: 0-10 V continuing adjustable, error <5%;

Extra-cardiac: 0-50 V continuing adjustable, error <5%;

A-V interval: 0 ms≤PA-V<400 iris, default value 160 ms, error<5%; Pulse width: Intra-cardiac: 0.5, 1.0, 1.5, 2.0 ms, default value 1.0 ms, error<5%;

Extra-cardiac: 10-40 ms continuing adjustable, error <5%; There is 200 ms artificial refractory period after Pl delivery.

(5). Emergent pacing function: AOO/VOO modes, fixed frequency FS IS 1=75 ppm, Pulse width: 1.0 ms, both error<5%;

(6). Heart rate calculation range: 15-255 bpm, error<5%; if <15 bpm, the device will read as zero. 2) Clinical Effectiveness Examples

The prototype device has been applied to 111 clinical cases. Under the different temporary cardiac pacing functions, we applied intra-cardiac pacing mode VVI for 12 patients, AOO for 11 patients, VAT for 2 patients, DVI for one patient. In addition, extra- cardiac pacing (transesophageal) was used in the operating rooms terminating 72 PSVT patients under AOO mode with overdrive suppression, and AAI mode for 13 patients. All the catheter lead insertions were accomplished under the guidance of ECG on the LCD screen display.

Time of usage: Oct. 1 2005 to Dec. 1 2005 Equipment used: PACE140 / PACE2006

Materials and Methods

1. Research Objective

12 patients aged 35 to 74 (8 male, 4 female) were studied. There were 2 patients with AMI complicating third degree AV block, 2 viral myocarditis complicating third degree AV block, 2 sick sinus syndromes, 2 cardiac arrests, and 4 cases with severe bradycardia received protective temporary pacing before performing surgical operation.

2. Equipments

1) PACE 140 multi-functional temporary pacemaker (abbr. PACE 140) developed by the inventor provided several pacing modes such as AOO/VOO, AAI₅VVI, VAT and DVI. It Different from traditional temporary cardiac pacemakers, PACE 140 had an accessional LCD for displaying intracardiac electrograph or surface ECG. Additionally, manual operation, intra-cardiac or extra-cadiac sense could be chosen arbitrarily. PACE 140 can be used as a portable monitor for cardiac arrhythmia.

3. Procedure

Percutaneous transvenous introducer techniques were used to enter the left or right subclavian veins. The electrode was passed from subclavian vein into the proper intracardiac sites and connected to PACE 140 under the guidance of intracardiac electrograph shown in LCD without fluoroscopy. The pattern of intrinsic atrial excitation was recognized when the electrode tip reached the right atrial cavity. Further advancement of the electrode resulted in a ventricular intra-cavity electrograph pattern. When the ventricular pacing and sensing thresholds were satisfactory, the electrode's position or orientation should be better. For AOO, AAI, VAT, or DVI pacing, the optimal position of the electrodes in right atrium showed that the amplitude of A wave was much wider than that of V wave. A wave was noticeable while V wave was not. In contrast, for VOO, VVI, VAT or DVI pacing, the optimal position of the electrode was that the amplitude of V wave should be distinctly wider than that of A wave, the amplitude of V wave was noticeable while A wave indistinct.

Results

1. The target sites of pacing electrode-tip were as the follows: (a) Single-chamber pacing: The sites were the top or in the outflow tract of the right ventricle (2 cases) and of the right auricle (2 cases), (b) Dual-chamber pacing. The sites were the top or the outflow tract of the right ventricle and the right auricle (2 cases). However, in two cases, one electrode-tip located in the top or the efferent tract of the right ventricle, the other floated

on the wall of the right atrium.

2. VVI mode were used for 2 patients (Figure 1), AAI for 6 (Figure 2), VAT for 2 (Figure 3), DVI for 2 (Figure4). If both the pacing and sense function were good, then fix the sheath and the electrode-end would be fixed.

3. Parameters of the pacemaker: 50 ~ 60 ( 57±7.5 ) ppm pacing frequency.

1.5 - 4 ( 2.8±1.2 ) V pacing voltage. The intra-cardiac electrode-tip's sense:

20~100(82±15) rate of A/V for the atrial sense. 65-100 (91±14) rate of V/A for the ventricular sense. In 2 cases of VVI pacing, we used the sense method of surface ECG R wave that lasted for 3 hours, and the VVI pacing functions worked well. In other 2 cases, AAI pacing functions were also performed successfully after taken trans-esophageal signal sense.

4. Complications

All cases were successfully paced and are free from any complications such as pneumothorax, haemothorax, cardiac perforation, infection and severe arrhythmias, etc.

Conclusion

Fluoroscopy is unquestionably the best method for assisting the operator to direct the pacing catheter through the venous system to cadiac cavities. However, pacing catheter placement also can be achieved by monitoring the electrograph derived from the pacing catheter's distal electrode. The electrograph is monitored as the pacing catheter is advanced. The pattern of intrinsic atrial excitation is recognized when the catheter tip reaches the right atrial cavity. Further advancement of the catheter results in a ventricular intracavity electrograph pattern. PACE 140 with multi-mode pacemaker and LCD is suitable not only for the catheter-tip approaching the target sites without fluoroscopy, but also for the different situation in which the patients have different needs of pacing modes. Using this device we have successfully performed AAI (6 cases), VVI (2 cases) .We also performed dual-chamber pacing including VAT (2 cases) or DVI pacing (2 cases) for the emergency treatment of third degree AV block. Performed dual-chamber pacing, the 4 patients have had a significant symptomatic relief and considerable hemodynamic improvements. PACE140 has the integrated structure combined various pacing modes and electrogram monitoring.

PACE 140 has the optional sense technique, by which the intracardiac electrograms or surface/esophageal electrical signals can be sensed selectively. If electrode displaced during temporary VVI pacing, the pacing would be immediately recovered by R wave sense. In the situation of AAI pacing, a bipolar electrode is put into esophagus and connected to surface ECG. The biggest amplitude of A wave can be acquired by esophageal electrogram. Therefore, the problem of electrode displace should be solved by extra-cardic or esophageal A wave sense.

To the best of our knowledge, the production and application of our multifunctional pacemaker is the first reported in the world. It not only has the ordinary pacing modes, but also has VAT and DVI ones. This would broaden the clinical application scope of temporary cardiac pacing techniques.

Claims

Claims:

1. A portable inexpensive and safe temporary pacemaker, including a) amplifier for ECG display, b) Inside heart amplifier, c) efficient direct current voltage increase equipment, d) pulse amplifier inside and outside heart (through esophagus), e) catheter location choice device, f) display location choice device, and g) LCD screen which displays ECG.

2. The pacemaker in claim 1 which displays ECG chart on its LCD screen.

3. The pacemaker in claim 1 which has amplifier for heart signals displayed on LDC, and has TTL circuit with ES[T (interval signal) and computer program and CPU controlling the whole device.

4. The pacemaker in claim 1 which can display ECG and pulsing effect on its LCD and pulse through its pulse amplifier inside and outside heart (through esophagus) at the same time.

5. The pacemaker in claim 1 where LCD screen for ECG display from intra-cardiac chamber or body surface leads;

6. The pacemaker in claim 1 where catheter insertion into the heart without the need of X-ray machine or Fluoroscopy or other guiding equipment.

7. The pacemaker in claim 1 can also be used as a portable mobile ECG monitor for real time ECG display. The ECG charts can be saved into its memory.

8. The pacemaker in claim 1 combines single-chamber and dual-chamber function into one model.

9. The pacemaker in claim 1 has non-invasive trans-esophageal cardiac pacing function.

10. The pacemaker in claim 1 combines intra-cardiac and extra-cardiac pacing function into one model.

11. The pacemaker in claim 1 can be used for any cause induced sudden cardiac arrest, apparent bradycardia, any sudden cardiac events with >=2.5 sec interval no QRS waves.

12. The pacemaker in claim 1 can be used to treat sick sinus syndrome (SSS) and cardiac emergency due to sinus-atrium IF and IIP transduction block triggered bradycardia.

13. The pacemaker in claim 1 can be used for emergent pacing to treat bradycardia accompanied with atrium-ventricle IF and III⁰ transduction block caused by acute myocardial infarction, acute myocarditis, or digitoxin overdose intoxication and etc..

14. The pacemaker in claim 1 can be used for Temporary and alternative measure before installation of implantable cardiac pacemaker in the patients.

15. The pacemaker in claim 1 can be used for Intra-cardiac chamber pacing to terminate paroxysmal atrial flutter (AF) and fibrillation (Af), paroxysmal atrial tachycardia (PAT), paroxysmal ventricular tachycardia (PVT), paroxysmal supraventricular tachycardia (PSVT) and other tachycardia arrhythmia.

16. The pacemaker in claim 1 can be used for Transesophageal atrial pacing (noninvasive) to terminate PAT, PSVT and type I paroxysmal atrial flutter.

17. Using the feature of dual chamber pacing with our device includes an adjustable PA- Pv interval range from 0 to 400 ms (by means of a dialog box function on the LCD display), the pacemaker in claim 1 can be used to treat patients with heart failure, idiopathic myocarditis, and myocarditis with wide QRS waves, and to reduce pressure difference across the A-V valves in some patients.

18. Using features of A wave and V wave recorded by the bipolar filtered esophageal ECG on the LCD monitor, the pacemaker in claim 1 can be used for diagnosis and differentiation of cardiac arrhythmias, and this is the best way to obtain P wave in clinics by a non-invasive procedure (transesophageal).