The automatic implantable cardioverter-defibrillator: efficacy, complications and survival in patients with malignant ventricular arrhythmias.

Ninety-four patients underwent surgery for automatic implantable cardioverter-defibrillator implantation. Ninety patients were discharged from the hospital with the device and were followed up for a mean period of 17 +/- 10 months. Forty-six patients experienced at least one discharge of the device under circumstances consistent with a malignant ventricular arrhythmia. One sudden death occurred. Complications included perioperative death (3 patients), post-operative ventricular tachycardia (12 patients) and atrial fibrillation (8 patients), perioperative myocardial infarction (1 patient) and device discharges for sinus tachycardia and supraventricular arrhythmias (17 patients). Six and 12 month survival rates by life table analysis were 98.7 and 95.4%, respectively. Thus, the automatic implantable cardioverter-defibrillator is a highly effective and relatively low risk treatment modality for patients with refractory life-threatening ventricular arrhythmias.

Permanent radiofrequency ventricular pacing for management of drug-resistant ventricular tachycardia.

Three patients with frequent episodes of symptomatic, sustained ventricular tachycardia that often required physician intervention were treated with a permanent patient-activated radiofrequency ventricular pacemaker for self-termination of ventricular tachycarida. Before pacemaker implantation, electrophysiologic testing revealed the tachycardia to be resistant to all approved and several investigational antiarrhythmic drugs. In all three patients, ventricular tachycardia was reliably and reproducibly terminated with brief bursts of rapid right ventricular apical pacing over several hundred trials. No patient had rapid ventricular pacing-induced acceleration of ventricular tachycardia or pacing-induced ventricular fibrillation. Since the implantation of a radiofrequency ventricular pacemaker an average of 13.7 months ago, all episodes of ventricular tachycardia (average 43/patient) have been terminated successfully by radiofrequency pacing, and no patient has required hospitalization for an arrhythmia-related problem.

Clinical and hemodynamic comparison of VVI versus DDD pacing in patients with DDD pacemakers.

To identify better those subgroups of pacemaker recipients who will benefit from dual chamber pacing, 19 patients with DDD pacemakers that were physiologically paced were entered into a blinded, randomized protocol comparing long-term VVI versus DDD pacing. Patients were evaluated in each of the pacing modes for exercise performance, cardiac chamber size, cardiac output, functional status and health perception. Eight patients (42%) insisted on early crossover, from VVI to DDD pacing, after only 1.8 +/- 1.4 weeks because of symptoms consistent with pacemaker syndrome. Overall, 12 patients preferred DDD pacing and no patient preferred VVI pacing (p = 0.001). Percent fractional shortening (30 +/- 8 vs 24 +/- 6%, p = 0.009) and cardiac output (6.3 +/- 2.6 vs 4.4 +/- 2.2 liters/min, p = 0.0001) where significantly greater in the DDD mode. Exercise duration was greater during DDD compared with VVI pacing (11.3 +/- 3.7 vs 10.1 +/- 3.7 minutes, p = 0.006). However, it was only in the crossover subgroup that DDD pacing resulted in significant improvement in exercise performance and health perception compared with VVI pacing. This subgroup of patients was characterized by an intrinsic sinus rate of less than 60 beats/min (4/8 vs 0/11, p = 0.006), ventriculoatrial (VA) conduction (4/8 vs 1/11, p = 0.048), greater increase in exercise peak systolic blood pressure from VVI to DDD mode (21 +/- 12 vs 4 +/- 13 mm Hg, p = 0.02) and greater improvement in exercise capacity from VVI to DDD pacing (2.2 +/- 1.2 vs 0.6 +/- 1.4 minutes, p = 0.03) compared with the other 11 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler ultrasound measurement of cardiac output in patients with physiologic pacemakers. Effects of left ventricular function and retrograde ventriculoatrial conduction.

Dual-chamber cardiac pacing (DDD) offers obvious theoretical advantages over traditional ventricular demand (VVI) pacing. Nevertheless, no widely agreed upon criteria exist for the selection of patients for physiologic DDD pacemakers compared with the simpler VVI systems. Accordingly, a non-invasive method for measuring cardiac output (Doppler ultrasound) was used to identify candidates for pacing who would derive the greatest hemodynamic benefit from DDD vs VVI pacing. Among 29 patients studied at rest during VVI-mode pacing, the average cardiac output by Doppler ultrasound was 4.3 +/- 0.3 liters/min (mean +/- standard error of the mean). In the DDD mode, the average cardiac output was 5.0 +/- 0.3 liters/min (p less than 0.001). Baseline left ventricular ejection fraction did not identify a group that improved more with DDD pacing. Patients who showed either retrograde ventriculoatrial conduction or described symptoms consistent with the "pacemaker syndrome" during VVI pacing, however, showed greater increases in cardiac output during DDD pacing. In these patients, the mean improvement in cardiac output was 30.4 +/- 8.6% with DDD vs VVI pacing, as opposed to an average increase of only 14.4 +/- 3.4% in the remaining 20 patients (p = 0.02). Thus, Doppler ultrasound can be used to quantitate the change in cardiac output at rest that occurs with DDD vs VVI pacing. The change is independent of the level of left ventricular function but is substantially higher when there is evidence of ventriculoatrial conduction or the pacemaker syndrome.

Effects of coronary bypass grafting on resting left ventricular contraction in patients studied 1 to 2 years after operation.

Left ventricular contraction was evaluated with angiography in 51 patients 1 to 2 years after coronary arterial bypass surgery. The left ventricle was classified into five segments, and segmental ventricular wall motion was analyzed with subjective and objective methods. With subjective analysis, 25 percent of asynergic segments showed improvement, 72 percent no change and 3 percent deterioration in contraction. There was a 5 percent incidence rate of new wall motion abnormalities in segments that were judged normal from the preoperative ventriculogram. Objective analysis revealed significant improvement in contraction of asynergic segments in each of the five left ventricular segments analyzed. Thus, 1 to 2 years after coronary bypass surgery, there was a significant reduction in left ventricular segmental wall motion abnormalities, and the incidence of deterioration in contraction was small.

The effect of antithrombotic therapy on patency rates of saphenous vein coronary artery bypass grafts.

In an attempt to improve upon the reported long-term patency rates of 65% to 85% for saphenous vein coronary artery bypass grafts (CABG), a prospective randomized trial comparing warfarin, aspirin, and placebo treatment in post-CABG patients was carried out. From an initial group of 216 patients, 161 patients remained in the study, and vein graft patency was determined in 111 patients (220 grafts) from 1 to 47 months postoperatively. There was a trend toward better cumulative graft patency in patients given warfarin, but the results did not achieve statistical significance. Improved results with warfarin were most marked among patients who were restudied within 24 months of CABG operation, in most instances because of the development of recurrent angina pectoris. There were four major bleeding complications of warfarin therapy, including one death, over 2,108 patient-months. Since most of the occlusive changes in vein grafts appear in the first 6 to 12 months, any effect of antithrombotic therapy will be most evident in the early postoperative period, with greatly reduced impact with long-term administration. Results of this study suggest that short-term antithrombotic therapy deserves further assessment in prevention of vein graft occlusion in the first year or two following a CABG operation. This potential benefit must be evaluated in the context of the recognized bleeding complications of warfarin therapy.

Pacemaker leads.

Present day pacemaker leads are far superior in every respect to those of the past. Modification of fixation characteristics has reduced displacement rates to 1% or less in most centers. Fracture of multifilar leads is a rarity. Biodegradation of polyurethane insulation appears to be an isolated problem specific to individual lead models and may be related to physical stresses incurred during manufacture or lead insertion. Recent evidence has incriminated an interaction of polyurethane with silver which arises from the drawn braised strand conductor substrate of those leads in which this problem has been noted. This may explain why the problem has been restricted to specific lead models of one manufacturer to date. Lack of uniformity of lead terminal size between manufacturers and even within the same manufacturer's product line continues to baffle this observer. Although past problems of lead displacement have been markedly reduced, the difficulty of removing chronic leads which have become septic appears to have worsened. Modification of existing leads to ensure that the interface between electrode tip and proximal shaft is unidiametric is essential.

Pacemakers and store security devices.

The ever-increasing complexity of medical device therapy and installation of public electronic security systems demands vigilance in discerning interactions that may be harmful to patients during typical activities of daily living. Premature pacemaker stimulation, isolated skipped beats, or reversion to backup asynchronous pacing have been observed during in vitro and in vivo testing. To date, no deaths and only minor inconvenience have been reported during extreme exposure of patients with pacemakers when they have come directly in contact with or in close apposition to electronic security systems. Patients with any type of implanted electronic medical system should be forewarned: "Don't lean, don't linger" near any potential source of electromagnetic interference. Changing technologies in implantable electronic medical systems as well as societal sources of electromagnetic interference require continued awareness on the part of physicians and patients alike, with care being taken to distinguish largely theoretical hazards from those that constitute meaningful dangers to patients with implanted cardiac arrhythmia devices.

The cardiac pacemaker: functions, falterings, and fate.

No pacemaker problem is predictable enough to plan for, with the possible exception of battery failure, so follow-up surveillance is essential. Pacemaker malfunctions are generally either actual device malfunctions or adverse interactions between the pacer and the patient's body. Depletion of the power source is the most common event.

Programmable pacemakers: technical features and clinical applications.

With each new generation of pacing systems, there appears to be a renewed interest in providing the physician with something else to program. Many of the aforementioned parameters that have been programmable options in single-chamber devices are now selectively available in two-channel units. A growing interest in telemetry that offers the physician a means of electronic dialogue with the pulse generator to assess existing parameters, battery voltage, and hermeticity, and provides transmission of such data as an intracavitary ECG, arrhythmia monitoring, and historical data on the patient are variations of programmability soon to be increasingly available. A major responsibility is arising for the physician who reprograms an implanted pacemaker system to maintain accurate records and ensure that the patient and other physicians are aware of any new adjustments. Failure to do so risks needless removal of otherwise properly functioning devices by other physicians with whom the patient may interact. Thus, while programmability has widened the horizons for noninvasive adjustment of existing pacemaker performance, it has also markedly complicated the record-keeping responsibilities of the monitoring physician.