Long-Term Follow-Up of Patients Treated with Automatic Scanning Antitachycardia Pacemaker

The long-term efficacy of an automatic antitachycardia pacemaker was evaluated in 13 patients with supraventricular tachycardia and in two patients with ventricular tachycardia. Patients were followed for 4–53 months (median 16). The concertina scanning mode with 2–7 extrastimuli proved to be effective in all patients but one. During follow-up, two patients had to be reoperated due to sensing problems. Atrial flutter was induced during scanning in one patient, termination mode was triggered by sinus tachycardia in one patient despite beta blocker therapy, and in one patient after cessation of beta blocker treatment. The pacemaker did not induce any serious arrhythmias and no sudden deaths occurred. Seven patients were given beta blockers, one patient with ventricular tachycardia was additionally administered amiodarone. In conclusion, the PASAR 4171 (Telectronics, Englewood, CO, USA) automatic scanning pacemaker is an alternative or adjunctive means to chronic antiarrhythmic drug therapy in patients with supraventricular tachycardia, but further versatility with regard to sensitivity, refractory period, and tachycardia recognition is required to eliminate the shortcomings observed, including the need for additional beta blocker therapy.     

Clinical Experience with a New Software-Based Antitachycardia Pacemaker for Recurrent Supraventricular and Ventricular Tachycardias

The Intermedics Intertach 262-12 tachycardia reversion pulse generator was implanted in 14 patients (six male, eight female, mean age at implantation 45 +/- 16 years) with recurrent symptomatic tachycardias. Six patients had atrioventricular (AV) nodal reentrant tachycardia, three patients had orthodromic tachycardia with Wolff-Parkinson-White syndrome, two had circus movement tachycardia via a concealed bypass tract, two had ventricular tachycardia, one patient had atrial flutter. Mean duration of symptoms before implantation was 8 +/- 4 years and mean number of antiarrhythmic drug trials was 3.5 +/- 1. The primary tachycardia response made consisted of autodecremental pacing in one patient, burst pacing in two patients, and adaptive scanning of the initial delay or burst cycle length in eleven patients. The secondary tachycardia response mode consisted of autodecremental pacing in four patients, burst pacing in three patients and burst scanning in four patients. Tachycardia response was automatic in all but one patient with ventricular tachycardia. During a follow-up period of 30.5 +/- 10.6 months, one patient with ventricular tachycardia died from a nonarrhythmic cause. Reinterventions were necessary due to electrode fracture in one patient and due to pacemaker software defect in another one. Two patients underwent surgical cure of their arrhythmia: one patient with atrial flutter and one patient with AV nodal reentry tachycardia, 24 months and 11 months postpacemaker implantation, respectively. Four patients required digitalis to prevent pacing induced atrial fibrillation. Other proarrhythmic effects were not encountered. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions. It provided a valuable adjunctive therapy in these selected patients.     

Clinical Experience with the Intertach 262-12 Pulse Generator in Patients with Recurrent Supraventricular and Ventricular Tachycardia

FROMER, M., ET AL.: Clinical Experience with the Intertach 262-12 Pulse Generator in Patients with Recurrent Supraventricular and Ventricular Tachycardia. An antitachycardia pulse generator, the Intermedics Intertach 262-12 was implanted in 16 patients (14 patients with supraventricular tachycardia of various origins and two patients with recurrent ventricular tachycardia), who were not responsive to various antiarrhythmic drug regimens. The follow-up was from 6–49 months (mean 30.9 ± 13.8). Five patients had a follow-up of over 3 years. The device was used in all patients. One patient with ventricular tachycardia died from a nonarrhythmic cause. Loss of responsiveness to burst pacing was observed in 1/14 patients with supraventricular tachycardia and nontolerance of antitachycardia pacing in one patient. Overall clinical success of pacing was observed in 13/16 patients = 81%. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions.     

Comparative Effectiveness of Pacing Techniques for Termination of Well-Tolerated Sustained Ventricular Tachycardia

Ventricular tachycardias can be terminated by a variety of pacemaker techniques, including rapid and slow stimulation. Fast tachycardias are typically poorly tolerated, and require prompt intervention, usually with rapid pacing. Termination of ventricular tachycardia by slow or single capture pacemaker stimulation techniques is attractive, because of its presumed safety and the possibility of using simple implantable pacers. To identify factors favoring termination, single capture stimulation was used in 390 episodes of ventricular tachycardia in 21 patients, 16 with coronary artery disease, able to tolerate ventricular tachycardia forseveral minutes. Single capture stimulation terminated 223 episodes (57%) in 18 patients, and two were accelerated. Of 157 episodes exposed to 2–3 programmed extrastimuli or rapid pacing 149 (94%) were terminated and 7 were accelerated. Direct current cardioversion was needed in 12 episodes. Without medications, only two patients tolerated VT. Only one patient had reliable termination with single capture stimulation over several days. Systolic blood pressure was similar in episodes terminated and not terminated by single capture stimulation, but the ventricular rate was significantly lower in episodes terminated, 116 ± 19 vs. 133 ±24 (p<0.001). Termination of ventricular tachycardia was not affected by QRS morphology. Single capture termination of ventricular tachycardia is largely unpredictable, with limited reproducibility over a period of time. Although comparatively safe, single capture techniques are not likely toprove useful in the long-term treatment of many patients with recurrent ventricular tachycardia.     

Termination of Ventricular Tachycardia by Programmed Extrastimuli from an Externally-Activated Permanent Pacemaker

Two patients with hemodynamically well-tolerated recurrent ventricular tachycardia, drug resistant and previously requiring numerous external electrical cardioversions, had a permanent pacemaker implanted which could be programmed to deliver extrastimuli to convert the ventricular tachycardia to normal sinus rhythm. The patient- or physician-activated device can be programmed to induce or terminate ventricular tachycardia with extrastimuli delivered at the predetermined intervals which consistently induced or terminated the arrhythmia in the electrophysiology laboratory, allowing repeated evaluation of drug regimens. The pacemaker has reliably, painlessly, and consistently induced and terminated repeated episodes of ventricular tachycardia. This programmable pacemaker offers an alternative therapy for patients with hemodynamically well-tolerated refractory ventricular tachycardia.     

Implantable Pacers for Tachycardia Termination: Stimulation Techniques and Long-Term Efficacy

The long-term efficacy of pacing for termination o/supraventricular tachycardia (SVT) and ventricular tachycardia (VT) was reviewed. Increasingly complex and sophisticated antitachycardia pacing stimulation patterns have evolved, and are outlined. Although excellent results are reported with simple patterns, it may be that the more complex algorithms increase the percentage o/tachycardia patients who may be candidates for implantation of a device. In the papers reviewed, there were 460 patients, 268 with SVT, and 192 with VT. Results were judged to be good-excellent in 96.5% of both VT and SVT groups.     

Automatic scanning extrastimulus pacemaker to treat ventricular tachycardia

Many investigators have reported the use of various permanent pacemaking modes in the long-term management of patients with recurrent ventricular tachycardia. The three general types of antitachycardic pacemakers are: (1) underdrive; (2) burst; and (3) scanning pacemakers. Such devices have been activated externally or have had automatic activation. Each antitachycardic pacemaking modality has known technical and physiologic limitations. A serious limitation of dual-demand underdrive pacemakers is that they are usually successful only for tachycardias with a rate below 160 bpm because a random stimulus is needed for conversion. Therefore, this modality is seldom useful in patients with symptomatic sustained ventricular tachycardia in which rates are generally greater than 160 bpm and/or hemodynamic compromise occurs rapidly. Although others have reported the successful use of burst pacemakers in the control of ventricular tachycardia, this technique may cause acceleration of ventricular tachycardia and induction of ventricular fibrillation. Programmable automatic scanning pacemakers have been used successfully to treat paroxysmal supraventricular tachycardia and have been used recently in combination with antiarrhythmic agents to control ventricular tachycardia. This report outlines the use of an automatic scanning pacemaker alone for the treatment of symptomatic ventricular tachycardia in a patient who was unable to tolerate conventional antiarrhythmic medications.     

Clinical Evaluation of an Adaptive Tachycardia Intervention Pacemaker with Automatic Cycle Length Adjustment

An external version of a new pacemaker designed for automatic tachycardia termination is described. In response to a tachycardia, defined as four successive beats occurring at a rate faster than a variable preset value, a number of stimuli (1-15) are generated. The initial coupling interval and subsequent pacing cycle intervals (where applicable) are always the same. Failure to terminate tachycardia results in the reduction of the pacing cycle length by 6 ms before termination of tachycardia is re-attempted. Pacing cycle length reduction may be repeated up to 16 times. If all coupling intervals of a single extrastimulus fail to achieve tachycardia termination, a second stimulus is scanned with the first through the same range of decrements. Additional stimuli, to a total of 15, could be used. A memory function is incorporated to retain and re-use a successful sequence. The pacemaker was evaluated in 16 patients with recurrent "supraventricular" (atrioventricular and intra A-V nodal) tachycardia, using right ventricular pacing. Termination was successful in all patients. More than two stimuli were necessary in only two patients, one of whom required five, and the other six stimuli. No unwanted arrhythmias were induced.     

Long-Term Antitachycardia Pacing Experience for Supraventricular Tachycardia

A pacemaker was used to control drug-resistant reentrant supraventricular tachycardia (SVT) in 40 patients. An antitachycardia pacemaker was implanted in 37 for SVT; in one for ventricular tachycardia that could also be used to terminate SVT; in one SVT could be terminated with an activity rate variable pacemaker; and in one a DDD pacemaker was used for prevention and termination of SVT. Twenty patients had AV nodal reentrant tachycardias, eight had tachycardias due to a concealed accessory pathway, eight had a Wolff-Parkinson-White syndrome, three had reentrant atrial tachycardias, and one had atrial flutter. Twenty-two patients were paced from the right atrium, five from the coronary sinus, ten from the right ventricle, and three had a DDD pacemaker. During a total follow-up period of 1,503 (mean 38) months an estimated 16,240 episodes of tachycardia were terminated promptly at home, 58 required several attempts, 57 episodes lasted longer than 30 minutes but did not require medical attention, and 11 required hospital admission. Hospital admission for SVT decreased from one per patient-month (in the 3 months before implantation) to 1 per 137 patient-months after implantation. Additional reentrant tachycardias occurred in 13 patients. Antiarrhythmic drug therapy in combination with a conservative antitachycardia pacing mode was required in four patients paced from the atrium to avoid pacing induced atrial fibrillation. Antiarrhythmic drug therapy was used in 42% of patients to help control SVT. Conclusions: (1) Drug-resistant SVTs can be safely and effectively managed on the long-term with antitachycardia pacemakers. (2) Rapid termination of SVT improved the quality-of-life significantly by avoiding prolonged episodes of tachycardia and repetitive hospital admissions.     

Frequent Attacks of Supraventricular Tachycardia in a Patient Treated with an Automatic Scanning Pacemaker (PASAR): Holter Documentation of 554 Episodes

A 68-year-old woman suffering from frequent attacks of supraventricular tachycardia received an implantable, automatic scanning pacemaker for tachycardia termination (PASAR). Electrophysiological study had shown the mechanism to be atrioventricular reentry with retrograde conduction through a concealed bypass tract. During 1 year of follow-up, a total of twenty-one 24-hour Holter recordings documented 554 episodes of tachycardia. In spite of marked fluctuation in tachycardia rate from 135 to 195 bpm and a considerable variation in diurnal pattern of onset of episodes, a clinical improvement resulted. Previous episodes of tachycardia had been isolated and of longer duration. Following implantation, an unexpected observation was made of numerous episodes of supraventricular tachycardia confined to periods lasting up to several hours. This pattern seemed to result from the efficacy of tachycardia termination combined with a continued presence of factors responsible for initiation of tachycardia.     

Tachycardias Initiated by Automatic Antitachycardia Pacemakers

Available automatic tachycardia-terminating pacemaker cannot distinguish between physiological and pathological tachycardia and, consequently, electrical stimulation during sinus tachycardia can occur. In order to evaluate whether this might be an arrhythmogenic problem or not the cardiac response in eight patients having paroxysmal supraventricular tachycardia treated with tachycardia-terminating pacemakers was studied during exercise. After tachycardia recognition, the implanted pulse generator automatically emits single or double critically timed premature stimuli for termination of the arrhythmia. Post-implantation examination revealed successful tachycardia termination by the pacemaker at rest, without the addition of any antiarrhythmic drugs, in all eight patients. During exercise tests, the sinus rate in seven patients exceeded the programmed tachycardia trigger rate resulting in triggered pacemaker stimulation. The native supraventricular tachycardia was initialed in four cases. In one of these patients, two short episodes of probable ventricular tachycardia were also recorded. This study demonstrates the clinical value of post-implantation assessments with exercise tests concerning the problem of pacemaker-initiated tachyarrhythmias. Tachycardia-terminating devices can induce tachycardias, and individual precautions must be taken in order to prevent or minimize the risk of pacemaker reversion of sinus rhythm to paroxysmal tachycardia or hazardous arrhythmias.     

Atrial Antitachycardia Pacing in Patients with Supraventricular Tachycardia: Clinical Experience with the Intertach Pacemaker

MCCOMB, J.M., ET AL.: Atrial Antitachycardia Pacing in Patients with Supraventricular Tachycardia: Clinical Experience with the Intertach Pacemaker. During a 3-year period, 22 patients with recurrent supraventricular tachycardia have been treated with antitachycardia pacemakers [Intermedics Intertach, 262–12, n = 17, and Intertach II, 262–16, n = 5). Eighty-two percent were female, the mean age was 44 ± 14 years; 86% had atrioventricular node reentrant tachycardia. Symptoms had occurred over 11.8 ± 7.1 years, with 3.6 hospital admissions per patient, despite 4.7 ± 2.1 antiarrhythmic drugs. Following pacemaker implantation, during a follow-up of 14.8 ± 11.5 months, only two patients have been readmitted to a hospital because of supraventricular tachycardia (mean 0.1 per patient). One patient is taking an antiarrhythmic agent, and four are taking beta adrenergic blocking agents. Thus, 23% are taking cardioactive drugs (it was anticipated that two patients would continue on drugs after pacemaker implantation). There have been no serious complications. Atrial antitachycardia is thus an effective therapy in carefully selected patients with recurrent supraventricular tachycardia, reducing hospital admissions for supraventricular tachycardia and reducing the need for antiarrhythmic drugs.     

Electrophysiologic Characterization of Surgically Induced His Bundle Rhythm in Man

Seven patients who had His bundle section and permanent ventricular pacemaker insertion for intractable recurrent supraventricular tachycardia underwent electrophysiologic studies 4–6 months postoperatively. The permanent pacemaker was inhibited to assess the His bundle recovery time (HBRT) and spontaneous His bundle rate (SHBR) (tenth postinhibition cycle). In addition, in five of the seven patients, the HBRT and SHBR was also assessed during mild supine exercise and after administration of intravenous atropine followed by lidocaine. There was no significant difference in HBRT or SHBR before exercise (2695 ± 1056 ms; 1435 ± 75 ms), during mild supine exercise (2220 ± 1564 ms; 1379 ± 42 ms), or after atropine (2152 ± 544 ms; 1379 ± 117 ms) or lidocaine (3943 ± 3198; 1487 ± 139 ms, respectively). Only one patient showed consistent lengthening of both HBRT and SHBR after lidocaine. On a separate day, programmed ventricular extrasiimuli were induced during ventricular overdrive pacing. In three of the seven patients, programmed ventricular extrastimuli resulted in typical bundle branch reentrant depolarizations. Four of the seven patients underwent maximal exercise treadmill testing. In none of these four patients did the His bundle rate exceed that of the implanted pacemaker. We conclude that prolonged pauses often follow pacemaker inhibition in these patients; therefore, careful follow-up of pacemaker function is required. Surgically induced His bundle rhythms in man are characterized by spontaneous rates of 38.7 to 45,5 beats/min and do not increase their rate after vagolysis or during mild exercise. In addition, the atrioventricular node is not required for bundle branch reentry in man.     

Externally Activated Antitachycardia Pacemaker With Noninvasive Electrophysiologic Re-testing Capability

An Omni Orthocor 234A special device pacemaker was implanted in nine patients for treatment of drug-resistant supraventricular tachycardia (three patients) or ventricular tachycardia (six patients). This device is activated using a special external unit, which delivers from six to 15 stimuli at preselected coupling intervals ranging from 195 to 500 ms. Serial noninvasive electrophysiology studies were performed either in the hospital or on an outpatient basis using the triggered mode, which can respond to programmed chest wall stimulation. Three patients with reciprocating supraventricular tachycardia were treated effectively by this device during an average follow-up of 2.2 years. Of the six patients with stable ventricular tachycardia amenable to pacemaker termination, only four remained successful during an average follow-up of 1.9 years. Such devices may find important use in serial noninvasive electrophysiologic testing during long-term clinical follow-up. The present form of this device is inadequate for widespread application, but may be useful for highly selected individuals.     

Limitations to Activation of the Antitachycardia Burst Pacing Function of the Symbios 7008 Pacemaker in the Universal (DDD) Mode

The Symbios 7008 antitachycardia pacemaker was implanted in five patients for control of supraventricular tachycardia. Shortly after implantation in the first two patients, it was noted that the burst pacing sequence was not automatically activated by tachycardia when the pacemaker was in the DDD mode. Data from these two and the subsequent three patients were evaluated to explain this observation. The problem was primarily related to the operation of the device during the postventricular atrial refractory period. In all patients, the atrial electrogram encroached upon the programmed postventricular atrial refractory period because VA conduction during SVT was less than the lowest programmable interval (155 ms). Atrial events occurring during this interval will not trigger the tachycardia termination sequence. In all five patients, the size of the atrial electrogram decreased substantially (48 +/- 10%; mean +/- SD) during supraventricular tachycardia compared to sinus rhythm. In at least two of the five patients, decreased atrial size during supraventricular tachycardia may also have resulted in intermittent failure of atrial sensing during tachycardia, even at the most sensitive setting (0.6 mV). The latter may remain a problem even if the technical fault in SVT detection in the DDD mode were corrected. Two related problems were noted in the DDD mode: ventricular events during rapid SVT do not reset the low rate interval, resulting in random low rate pacing; and, automatic prolongation of atrial refractory period by two successive ventricular events without an intervening atrial sensed event compounds problems of atrial sensing. All of these problems were easily circumvented in all patients by noninvasive reprogramming to the DVI mode in which supraventricular tachycardia detection is based on ventricular sensing. These findings have implications for the future design of such devices.     

Permanent programmable pacemakers in the management of recurrent tachycardias.

Patient reports are presented to indicate the application of standard implanted programmable pacemakers with endocardial electrodes for long-term overdrive suppression of recurrent ventricular tachycardia, and their adaptability to non-invasively induced burts of rapid ventricular pacing to cardiovert that arrhythmia. In carefully preselected patients with bradycardia-tachycardia syndrome, this type of programmable pacemaker may also be used to convert paroxysmal supraventricular tachycardia by short bursts of rapid ventricular pacing. In addition, the advantage of non-invasively instituting overdrive suppression with programmable pacemakers to control recurrent ventricular tachycardia appearing in patients being chronically paced for complete heart block is illustrated.     

Long-Term Therapy of Antitachycardia Pacing for Supraventricular Tachycardia

Long-term antitachycardia pacing therapy with the InterTach 262-12 and 262-16 was evaluated in 32 consecutive patients (mean age 50 +/- 13 years) with recurrent, drug refractory supraventricular tachycardia. AV nodal reentrant tachycardia was present in 20 patients, Wolff-Parkinson-White syndrome in ten patients, and a reentrant tachycardia due to Mahaim fibers in one patient. During follow-up of 39 +/- 17 months, 250 persistent tachycardia episodes occurred in 22 patients. By adjusting detection and termination mode, recurrent supraventricular tachycardia could be controlled in 19 of 32 patients (60%) by antitachycardia pacing alone. Concomitant antiarrhythmic drug therapy was required in ten of 32 patients (30%). During follow-up antitachycardia pacing became ineffective in three patients (10%). Thus, chronic antitachycardia pacing proved to be safe and effective in selected patients with drug refractory supraventricular tachycardia and could significantly improve quality of life by rapid termination of recurrent supraventricular tachycardia episodes.     

Termination Of Sustained Tachycardia By External Noninvasive Pacing

Invasive cardiac pacing has proved useful in the induction and termination of reentrant sustained tachycardias. In one of our two cases, programmed ventricular extra-stimulation was used to induce sustained ventricular tachycardia from the endocardial surface of the right ventricle. Induced ventricular tachycardia was terminated by burst ventricular pacing with an external cardiac pacemaker. In our second patient, external pacing was effective at inducing and terminating sustained supraventricular tachycardia. These patients illustrate that the principles of terminating sustained reentrant tachycardia with invasive pacing may also apply to noninvasive external pacing. The usefulness of this approach in treating reentrant tachycardias needs further evaluation.     

''Long-Term Results of Antitachycardia Pacing in Patients with Supraventricular Tachycardia

Between 1979 and 1984 the Cybertach-60, (Intermedics, Inc. Model 262-01), a programmable, automatic antitachycardia pacemaker was implanted in 11 patients who had drug-refractory supraventricular tachycardia (SVT). The patients have been followed for a total of 64-108 (mean 84 months). All patients were symptomatic and had failed two or more drugs and six patients had required prior DC cardioversion. The mechanism of supraventricular tachycardia was atrioventricular (AV) nodal reentry in six patients, AV reentry in four patients, and atrial tachycardia in one patient. Preoperatively all patients had reliable termination of the tachycardia without induction of atrial fibrillation by pacing methods available to Cybertach-60. Postimplant, Cybertach-60 reliably terminated all episodes of tachycardia without ancillary drug therapy. Nevertheless, at long-term follow-up antitachycardia pacing was effective and safe in the minority (36%), with only four patients out of eleven still using a pacemaker for supraventricular tachycardia. One of these four patients required additional drug therapy. In one of the patients, the Cybertach-60 was replaced after 78 months by a more advanced device, (Intertach, Intermedics, Inc.) because of a depleted Cybertach-60 battery. In seven patients who no longer use antitachycardia pacing for termination of tachycardia, one patient developed atrial fibrillation during tachycardia termination (at 58 months postimplant). Three patients experienced induction of tachycardia or atrial fibrillation by the pacemaker due to undersensing of sinus P waves (at 36, 48, and 51 months).(ABSTRACT TRUNCATED AT 250 WORDS)