Michel Bertholet

Clinical Experience with Implantable Devices for Control of Tachyarrhythmias

Pacing is becoming an accepted form of treatment for reentry tachycardias. The different pacing modalities available and experience with a patient‐activated antitachycardia pacemaker are presented in this paper. This system has bidirectional communication between pacemaker and pacemaker‐activator and between pacemaker and prescription formulator (which is a sophisticated portable stimulator used for non‐invasive electrophysiological evaluation of the system). This pacemaker was implanted in 18 patients with drug‐resistant tachycardias. Six patients had ventricular tachycardia, 3 had A‐V nodal reentrant tachycardia, 4 had the concealed accessory pathway, and 5 had the WPW syndrome. In the 3 months before implantation the mean number of admissions for termination of tachycardia was 2.1 per patient‐month. During a follow‐up period of 3–26 months only 6 patients were admitted once for termination of tachycardia (0.02 admissions per patient‐month). The reasons for admission of these 6 patients were: defective pacemaker activator in 2 patients, inadequate control of tachycardia in 2 patients, inappropriate use of the device in 1, and inadequate intake of medication in 1. All these problems were solved easily. Eight pacemaker activators required reprogramming, which was done in 5 patients on an out‐patient basis. The interval scanning mode was used in 9 patients. Nine patients required more than 2 stimuli for reproducible termination. A step‐wise increase in number of stimuli was used in 5 patients.

A versatile pacemaker system for termination of tachycardia

Abstract Externally activated pacemaker systems were implanted in 13 patients to control their drug-resistant tachycardias. Four patients had ventricular tachycardia, 2 had atrioventricular nodal reentrant tachycardia, 3 had tachycardias due to a left-sided concealed accessory pathway and 4 had Wolff-Parkinson-White syndrome. Nine patients were paced from the right ventricle, 2 from the right atrium and 2 from the coronary sinus. The pacing system consisted of an implantable pacemaker, an external pacemaker activator and a prescription formulator. The pacemaker can signal sensing by way of radiofrequency signals to the pacemaker activator or prescription formulator. Either 1 of the latter 2 devices then determines whether the sensed rhythm fulfills the tachycardia detection criteria and, if so, controls the delivery of the selected stimulation treatment by the pacemaker. With this bidirectional radiofrequency coupling, tachycardias were noninvasively initiated by the prescription formulator after implantation and at follow-up visits to test and eventually reprogram the pacemaker activator. During a follow-up of 116 patient-months, 624 episodes of tachycardia were effectively terminated by the patients. Incidental failure to terminate occurred in 3 patients because of a defective activator, changes in the electrophysiologic substrate and inappropriate use of the device. These problems were solved by reprogramming, replacement of the activator and education of the patient. Hospital admissions for termination of tachycardia decreased from an average of 2.6 per patient-month (in the 3 months before implantation) to 0.03 per patient-month after implantation (follow-up 4 to 16 months). It is concluded that (1) this programmable externally activated pacemaker system effectively manages drug-resistant tachycardia; (2) this system has the advantage of easy testing, multiple pacing modes and ready reprogrammability; and (3) the marked reduction in hospital admissions makes the system cost-effective.

5-HT2-RECEPTOR BLOCKADE IN THE TREATMENT OF HEART FAILURE: A Preliminary Study

Ketanserin (R 41 468), a quinazoline derivative, has been shown to be a selective blocker of 5-HT2 receptors. The drug was administered intravenously (10 mg given over a 3 min period) to 8 patients with severe cardiac failure already treated with digitalis, diuretics, and, in 4 cases, vasodilators. R 41 468 produced a significant fall in right-atrial, pulmonary-artery, pulmonary-wedge, and systemic arterial pressures. Systemic dynamic and total pulmonary vascular resistances were also reduced. Cardiac and stroke-work indices both increased, Heart rate remained unchanged. The platelet aggregation index, assessed in 2 patients, was initially low and was nearly normal 15 min after administration of a single dose of R 41 468.

Programmable extrastimulus pacing for long-term management of supraventricular and ventricular tachycardias: clinical experience in 16 patients

Sixteen patients with recurrent, drug-resistant supraventricular (13 patients) or ventricular (3 patients) tachycardia were treated chronically by programmable extrastimulus pacing; either a fully automatic device (Telectronics PASAR 4151: eight patients with supraventricular tachycardia) or a patient--activated device (Medtronic Interactive Tachy System) was used. During a follow-up period of 5 to 30 months, five of the subjects treated with the fully automatic device showed successful results, one had recurrent tachycardia, and two had their units explanted for system-related problems. The patients treated with the externally activated device were, on the whole, very well controlled. This mode of treatment, if applied in well-selected cases, is promising; it seems safe and considerably reduces the number of hospital admissions.

Artificial Circus Movement Tachycardias: Incidence, Mechanisms, and Prevention

In a group of 45 patients treated with Medtronic 7000 and 7100 pulse generators for sick sinus syndrome or second or third degree atrioventricular block, an atrial synchronous mode of pacing was programmed in 34 cases and spontaneously occurring artificial circus movement tachycardios (ACMTs) were observed in nine. An analysis of conditions of occurrence, triggering mechanisms and patterns of ACMT, is presented. Various modalilies of prevention are discussed. They resulted in suppression of ACMT in five patients and decrease of incidence in a sixth; the three remaining subjects were managed by definitive reprogramming in the DVI mode. Our conclusion is that correct prevention of ACMT requires the use of dual chamber pulse generators with programmable atrial refractory periods. For patients in whom a unit has already been implanted, careful observation of the triggering mechanism and pattern of ACMT may help in determining the most suitable way to prevent and suppress the arrhythmia.

Prognostic significance of electrocardiographic findings in angina at rest. Therapeutic implications.

Ninety-five patients with angina at rest were observed in the coronary care unit. Eighty-one per cent presented concomitantly or had previously presented some other manifestations of coronary artery disease. These patients were divided into two subgroups. In subgroup 1 (40 patients), episodes of non-exertional angina were associated with a pattern of hyperacute subepicardial injury and, frequently, with ventricular arrhythmias. In subgroup 2 (55 patients), the episodes of angina at rest were attended by horizontal ST depression, isolated T wave inversion, or trivial ST-T changes. Coronary angiographic findings were similar in both subgroups. Symptoms regressed in only 9% of patients in subgroup 1 while they were receiving beta-receptor antagonists, whereas amiodarone alone or amiodarone with nifedipine was successful in 58%. Of these patients, 25% developed a myocardial infarction shortly after admission. In subgroup 2 patients, beta-blockers were successful in 61%. Amiodarone isolated or associated with nifedipine was successful in 55% of the patients in whom it was tried. Only 5% of patients in this subgroup developed a myocardial infarction during their hospital stay. It is concluded that: (1) observation of the electrocardiogram during spontaneous angina in patients with known atherosclerotic coronary heart disease may be of prognostic significance and may influence therapeutic decision. (2) Amiodarone by virtue of its anginal and antiarrhythmic properties may be particularly useful in the treatment of non-exertional angina.

PACING METHODS FOR THE TREATMENT OF RECURRENT PAROXYSMAL VENTRICULAR TACHYCARDIA

The clinician is sometimes confronted with the difficult problem of a patient with recurrent attacks of paroxysmal ventricular tachycardia refractory to drug prevention. He may then refer his patient to the surgeon or else envisage implantation of an appropriate pacemaker. In the recent past, numerous publications describing various pacing modalities capable of effecting termination of supraventricular tachycardia have appeared in the literature.’-5 These techniques have only rarely been used for the treatment of ventricular tachycardia. The excellent review by Camm and Ward has thoroughly covered this p r ~ b l e m . ~ The present paper is concerned with ventricular pacing for the interruption (and not the prevention) of recurrent paroxysmal ventricular tachycardia.