Clinical characteristics of patients intolerant to VVIR pacing

The incidence and clinical predictors of the development of intolerance to VVIR pacing have not been extensively studied in prospective long-term randomized trials comparing different pacing modes. The frequency and clinical factors predicting intolerance to ventricular pacing are controversial. The Pacemaker Selection in the Elderly (PASE) Trial enrolled 407 patients aged >/=65 years in a 30-month, single-blind, randomized, controlled comparison of quality of life and clinical outcomes with ventricular pacing and dual-chamber pacing in patients undergoing dual-chamber pacemaker implantation for standard clinically accepted indications. We reviewed the clinical, hemodynamic, and electrophysiologic variables at the time of pacemaker implantation in 204 patients enrolled in the PASE trial and randomized to the VVIR mode, some of whom subsequently required crossover (reprogramming) to DDDR pacing. During a median follow-up of 555 days, 53 patients (26%) crossed over from VVIR to DDDR pacing. A decrease in systolic blood pressure during ventricular pacing at the time of pacemaker implantation (p = 0.001), use of beta blockers at the time of randomization (p = 0.01), and nonischemic cardiomyopathy (p = 0.04) were the only variables that predicted crossover in the Cox multivariate regression model. After reprogramming to the dual-chamber mode, patients showed improvement in all aspects of quality of life, with significant improvements in physical and emotional role. The high incidence of crossover from VVIR to DDDR pacing along with significant improvements in quality of life after crossover to DDDR pacing strongly favors dual-chamber pacing compared with single-chamber ventricular pacing in elderly patients requiring permanent pacing.

Catheter ablation of the slow AV nodal pathway in AV nodal re-entry tachycardia

AV node re-entry tachycardia has been managed with medical therapy to suppress AV node conduction. Radiofrequency ablation of the slow AV nodal pathway can eliminate recurrent spontaneous AVNRT, while preserving AV node conduction intact.

Accurate bedside technique for differentiating wide-QRS complex tachycardias

Patients undergoing open-heart surgery routinely receive temporary atrial pacing wires. The authors present a case report involving the use of these wires to differentiate the origin of a wide-QRS complex tachycardia. The technique, described in detail, should be utilized when appropriate.

A randomized comparative study of the electrophysiological and electrocardiographic effects of isradipine vs verapamil

Isradipine is a new dihydropyridine calcium antagonist reported to have minimal effects on cardiac electrophysiology. Of 19 patients with normal cardiac electrophysiological profiles, 11 received isradipine intravenously at doses of 0.0010, 0.0020, 0.0040 and 0.0080 mg.kg-1 (0.0150 mg.kg-1 total dose), and eight received verapamil intravenously at 0.0125, 0.0250, 0.0500 and 0.1000 mg.kg-1 (0.1875 mg.kg-1 total dose). One patient experienced hypotension several minutes after receiving the third isradipine dose. With isradipine, systolic blood pressure (BP) decreased from 154 +/- 24 to 151 +/- 22, 143 +/- 25, 133 +/- 19 and 124 +/- 17 mmHg, respectively. Diastolic BP decreased from 83 +/- 10 (baseline) to 80 +/- 12, 76 +/- 10, 74 +/- 7 and 68 +/- 9 mmHg, respectively. With verapamil, systolic BP changed from 132 +/- 20 (baseline) to 135 +/- 29, 132 +/- 24, 130 +/- 25 and 115 +/- 17 mmHg, respectively, and diastolic BP changed from 80 +/- 14 to 84 +/- 14, 81 +/- 9, 78 +/- 6 and 73 +/- 5 mmHg, respectively. Isradipine had no significant effect on the PR, QRS, QT and QTc intervals, nor were there changes in the atrial-His (AH) and His-ventricle (HV) intervals, atrioventricular nodal effective refractory period. Wenckebach cycle length or sinus node recovery time. Similarly, verapamil at the doses studied did not significantly affect PR, QRS, QT, QTc, AH or HV intervals. However, with verapamil, the Wenckebach cycle length changed significantly from 394 +/- 82 (baseline) to 448 +/- 93 ms. Despite the significant fall in BP with isradipine, heart rate did not change significantly. These results support the electrophysiological neutrality of isradipine on the cardiac conduction system.

Experience with a third-generation implantable cardioverter-defibrillator

A Medtronic 7216A pacemaker cardioverter-defibrillator was implanted in 16 patients (mean age 56 years) with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and organic heart disease with a mean left ventricular ejection fraction of 33%. Endocardial and epicardial defibrillation shock efficacy was evaluated before or at implant using 1 to 3 shock patterns, i.e., monophasic single, sequential or simultaneous shocks with dual and triple electrode configurations. Endocardial leads used a common right ventricular cathode and dual anodes, whereas epicardial leads used 2 or 3 helical coil patches. VT termination was evaluated using pacing or shock therapy, or both, whereas only shocks were used in VF. Programmable bradycardia pacing, individual zones for VT and VF detection and individualized pacing and shock therapy for VT and VF were used. Monophasic shocks had epicardial defibrillation thresholds ranging from 3 to 18 (mean 10) J and were comparable for sequential and simultaneous shocks (p greater than 0.2). VT detection rates ranged from 340 to 470 ms and VF detection rates from 270 to 330 ms. VT or VF induction, or both, was performed noninvasively in 13 patients after implant and was reproducibly terminated by rapid pacing alone (5 patients), low-energy shocks (2 patients), high-energy shocks (3 patients) and combined therapy (3 patients). Intermediate or high-energy shocks terminated all induced VF episodes. During follow-up (2 to 12 months), there have been 2 noncardiac deaths. Electrical therapy was delivered in 7 patients, for VT (3 patients), VT and VF (3 patients) and indeterminate tachyarrhythmia (1 patient). All VT/VF episodes were successfully terminated, with 78 of 96 (81%) spontaneous VT episodes terminated by pacing. Follow-up reprogramming was required in 5 patients. It is concluded that successful application of individualized electrical therapy prescriptions in patients with VT/VF is feasible. Pacing therapies, which are effective for induced VT, can be reliably used for effective long-term spontaneous VT termination in conjunction with shock therapy and can permit reduced patient exposure to shock therapy. Thus, a programmable hybrid pacemaker cardioverter-defibrillator system provides nonthoracotomy implantation, effective VT/VF termination, demand ventricular pacing and noninvasive modes for arrhythmia induction, event monitoring and clinical trouble-shooting.

Management of complications associated with a first-generation endocardial defibrillation lead system for implantable cardioverter-defibrillators

An automatic cardioverter-defibrillator could be implanted using an endocardial defibrillation lead system (consisting of a tripolar defibrillation electrode catheter in conjunction with an epicostal patch electrode) in 9 of 10 patients with sustained ventricular tachycardia or ventricular fibrillation. Six lead system complications were observed during a follow-up period of 51 +/- 36 weeks. Three catheter electrode conductor fractures occurred and manifested as oversensing and subsequent delivery of inappropriate shocks (1 patient), inability to defibrillate during electrophysiologic testing 3 months after implant (1 patient) and sudden cardiac death (1 patient). Asymptomatic patch electrode conductor fractures were detected on a routine chest roentgenogram in 2 patients. Endocardial defibrillation threshold testing performed at the time of implantation resulted in malfunction of a previously implanted permanent pacemaker pulse generator in 1 patient. Catheter and patch electrode replacement procedures were performed in 3 consenting patients under local anesthesia. Endocardial defibrillation thresholds after lead replacement were comparable to those obtained at time of initial implant. Serial clinical, roentgenographic and electrophysiologic evaluation should be included in follow-up procedures for endocardial defibrillation lead systems. Monitoring for deleterious effects of endocardial defibrillation threshold testing on previously implanted pacemaker systems should be performed at the time of implant and during follow-up. Improved lead designs are necessary for long-term use of endocardial defibrillation electrodes, but replacement procedures are feasible without thoracotomy.

Argon laser ablation of malignant ventricular tachycardia associated with coronary artery disease

The long-term clinical efficacy and safety of intraoperative mapping-guided argon laser ablation alone or in conjunction with standard surgical methods were assessed in 20 consecutive patients with refractory sustained ventricular tachycardia (VT) or ventricular fibrillation. A 15-W argon ion gas laser was used and pulsed laser energy was delivered through a fiberoptic catheter delivery system. Pre- and intraoperative mapping was used to localize the arrhythmogenic tissue. Postoperative clinical, ambulatory electrocardiographic and electrophysiologic evaluations were performed before discharge and at 1 year of follow-up. Thirty-eight VT morphologies were mapped and ablated with laser energy alone (82%), combined laser ablation and mechanical resection (13%) or mechanical resection alone (5%). Concomitant coronary artery bypass surgery was performed in 15 patients and in 1 patient it was performed with mitral value replacement. Postoperative 30-day mortality was 5%. One patient (5%) required postoperative antiarrhythmic drug therapy, and all survivors had suppression of inducible sustained VT at discharge. Mean left ventricular ejection fraction increased from 34 +/- 12% preoperatively to 41 +/- 13% postoperatively (p = 0.001). Efficacy rates for ablation of VT sites associated with anterior myocardial infarction and inferior or posterior myocardial infarction were comparable (100 vs 96%, respectively, p greater than 0.2). At 1-year follow-up no sudden deaths had occurred and total survival rate was 90%. Intraoperative pulsed argon laser ablation alone or in conjunction with standard surgical techniques improves the efficacy of surgical ablation procedures for VT or ventricular fibrillation and reduces the need for additional postoperative antiarrhythmic drug or device therapy.

Initial clinical experience with endocardial defibrillation using an implantable cardioverter/defibrillator with a triple-electrode system

We evaluated the early clinical performance of an implantable cardioverter/defibrillator with a nonepicardial lead system in patients with refractory ventricular tachycardia or ventricular fibrillation. Ten patients, mean age 67 years, mean left ventricular ejection fraction 35%, refractory to 5 +/- 2 antiarrhythmic drugs and with a history of prior cardiac surgery (7 patients), severe lung disease (2 patients), or renal failure (1 patient) underwent device and lead system implant. A tripolar electrode catheter with one sensing electrode and two defibrillating electrodes was placed in the right ventricular apex and a left thoracic submuscular patch electrode was used in an epicostal location. Defibrillation energy threshold was determined using dual- or triple-electrode configurations. Optimal patch electrode location was determined after temporary use of a cutaneous patch electrode prior to cardioverter/defibrillator implant. Electrophysiologic studies were performed before discharge and after 2 to 3 months to assess device function. Percutaneous insertion and placement of the electrode catheter was achieved in all patients. Defibrillation energy threshold testing was done using 1 to 4 (mean, 2.7) electrode configurations per patient and required 6 to 21 (mean, 13) ventricular fibrillation inductions and 8 to 56 (mean, 22) shocks per patient. In all patients, lowest reliable defibrillation energy threshold was obtained with a triple-electrode configuration (right ventricular common cathode with right atrial and thoracic patch as dual anodes) and bidirectional shocks (mean, 18 +/- 5 J). Optimal patch electrode position could be determined in 9 of 10 patients, and these 9 patients had cardioverter/defibrillator implant. Ventricular fibrillation termination with the first delivered shock at electrophysiologic study was documented in all patients. There was no perioperative mortality in device-implanted patients. Postoperative electrophysiologic studies before discharge (9 patients) and at 3 months (8 patients) continued to demonstrate successful defibrillation by the first device shock. During follow-up (range, 2 to 10 months; mean, 6 +/- 3 months), spontaneous device discharges occurred in 4 patients with inappropriate shocks due to electrode catheter fracture being documented in 1 patient. Antiarrhythmic drug therapy was withdrawn in 6 patients and reduced in 3 patients. We conclude, based on our preliminary experience, that an implantable cardioverter/defibrillator can be successfully used with a nonepicardial lead system for endocardial defibrillation in many patients. This lead system can be used with currently available pulse generators and should be considered at cardioverter/defibrillator implantation. It can be anticipated to reduce patient risk and hospital costs associated with this procedure.