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Background —A recent study has shown that the implantable atrial defibrillator can restore sinus rhythm in patients with recurrent atrial fibrillation when therapy was delivered under physician observation. The objective of this study was to evaluate the safety and efficacy of ambulatory use of the implantable atrial defibrillator. Methods and Results —An atrial defibrillator was implanted in 105 patients (75 men; mean age, 59±12 years) with recurrent, symptomatic, drug-refractory atrial fibrillation. After successful 3-month testing, patients could transition to ambulatory delivery of shock therapy. Patients completed questionnaires regarding shock therapy discomfort and therapy satisfaction using a 10-point visual-analog scale (1 represented “not at all,” 10 represented “extremely”) after each treated episode of atrial fibrillation. During a mean follow-up of 11.7 months, 48 of 105 patients satisfied criteria for transition and received therapy for 275 episodes of atrial fibrillation. Overall shock therapy efficacy was 90% with 1.6±1.2 shocks delivered per episode (median, 1). Patients rated shock discomfort as 5.2±2.4 for successful therapy and 4.2±2.2 for unsuccessful therapy ( P >0.05). The satisfaction score was higher for successful versus unsuccessful therapy (3.4±3.3 versus 8.7±1.3, P Conclusions —Ambulatory use of an implantable atrial defibrillator can safely and successfully convert most episodes of atrial fibrillation, often requiring only a single shock. Successful therapy is associated with high satisfaction and only moderate discomfort.

The publication of major studies dealing with the natural history of bradyarrhythmias and tachyarrhythmias and major advances in the technology of pacemakers and implantable cardioverter-defibrillators (ICDs) has mandated this revision of the 1991 ACC/AHA Guidelines for Implantation of Pacemakers and Antiarrhythmia Devices. This executive summary appears in the April 7, 1998 issue of Circulation. The full text of the guidelines, including the ACC/AHA Class I, II, and III recommendations, is published in the April 1998 issue of the Journal of the American College of Cardiology. Reprints of both the executive summary and the full text are available from both organizations. Following extensive review of the medical literature and related documents previously published by the American College of Cardiology, the American Heart Association, and the North American Society for Pacing and Electrophysiology, the writing committee developed recommendations that are evidence based whenever possible. Evidence supporting current recommendations is ranked as level A if the data were derived from multiple randomized clinical trials involving a large number of individuals. Evidence was ranked as level B when data were derived from a limited number of trials involving comparatively small numbers of patients or from well-designed data analysis of nonrandomized studies or observational data registries. Evidence was ranked as level C when consensus of expert opinion was the primary source of recommendation. The committee emphasizes that for certain conditions for which no other therapies are available, the indications for device therapies are based on years of clinical experience as well as expert consensus and are thus well supported, even though the evidence was ranked as level C. These guidelines include expanded sections on selection of pacemakers and ICDs, optimization of technology, cost, and follow-up of implanted devices. The follow-up sections are relatively brief because in many instances the type and frequency of follow-up examinations …

Background The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation. Methods and Results The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively ( P =.97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were −0.26±1.58 and −1.86±1.93 mm for the 130- and 200-J shocks, respectively ( P Conclusions We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

The automatic implantable cardioverter defibrillator (AICD) is now used commonly in the management of malignant ventricular arrhythmias. Its use may obviate the need for antiarrhythmic drugs or endocardial resection. We reviewed our continuing experience with the AICD to determine its safety and efficacy. Since June 1987, 102 patients (mean age: 63 years) who survived out-of-hospital ventricular fibrillation or hemodynamically unstable ventricular tachycardia not associated with acute myocardial infarction underwent implantation of an AICD. There were three operative deaths and nine complications. Eighty-nine patients are alive. No patient has experienced sudden cardiac death. Forty-two patients (43%) have had 1 or more AICD discharges associated with symptoms of cardiac arrest. During AICD implantation, it appears preferable to configure lead placement by individual patient characteristics rather than by a rigid protocol. The relative safety and efficacy of the AICD support its use as an alternative to toxic medications or more dangerous endocardial resection in suboptimal candidates.

Thirty-one large dogs were treated with diltiazem or placebo after a 15-minute period of cardiac arrest and cardiopulmonary resuscitation to examine the influence of diltiazem treatment on the resulting ECG rhythm, hemodynamics, and extent of myocardial and cerebral injury after cardiac resuscitation. Diltiazem had no adverse effects on resuscitation or the rhythm and blood pressure immediately after defibrillation. There were no differences in the total number of shocks required to obtain pulse, the type of rhythm achieved, the occurrence of heart block, or resuscitation rates between treatment groups. By 30 minutes after resuscitation, cardiac output was higher in the dogs that received diltiazem: 4.1 ± 1.4 L/min at one hour in the diltiazem group v 2.4 ± 1.5 L/min in the placebo group (P

The publication of major studies dealing with the natural history of bradyarrhythmias and tachyarrhythmias and major advances in the technology of pacemakers and implantable cardioverter-defibrillators (ICDs) has mandated this revision of the 1991 ACC/AHA Guidelines for Implantation of Pacemakers and Antiarrhythmia Devices. This executive summary appears in the April 7, 1998 issue of Circulation. The full text of the guidelines, including the ACC/AHA Class I, II, and III recommendations, is published in the April 1998 issue of the Journal of the American College of Cardiology. Reprints of both the executive summary and the full text are available from both organizations. Following extensive review of the medical literature and related documents previously published by the American College of Cardiology, the American Heart Association, and the North American Society for Pacing and Electrophysiology, the writing committee developed recommendations that are evidence based whenever possible. Evidence supporting current recommendations is ranked as level A if the data were derived from multiple randomized clinical trials involving a large number of individuals. Evidence was ranked as level B when data were derived from a limited number of trials involving comparatively small numbers of patients or from well-designed data analysis of nonrandomized studies or observational data registries. Evidence was ranked as level C when consensus of expert opinion was the primary source of recommendation. The committee emphasizes that for certain conditions for which no other therapies are available, the indications for device therapies are based on years of clinical experience as well as expert consensus and are thus well supported, even though the evidence was ranked as level C. These guidelines include expanded sections on selection of pacemakers and ICDs, optimization of technology, cost, and follow-up of implanted devices. The follow-up sections are relatively brief because in many instances the type and frequency of follow-up examinations …

Medical management of life-threatening ventricular arrhythmias is difficult because of the toxicity and limited efficacy of antiarrhythmic drugs. The automatic implantable cardioverter defibrillator (AICD) offers protection against malignant ventricular arrhythmias and allows some patients to be managed without antiarrhythmic drugs. We reviewed our experience with the AICD to determine its safety and efficacy. Since June 1987, 24 patients (mean age 63 years) who survived out-of-hospital ventricular fibrillation or hemodynamically unstable ventricular tachycardia not associated with acute myocardial infarction had implantation of an AICD. None had inducible monomorphic ventricular tachycardia associated with ventricular aneurysm. Twenty-three had abnormal left ventricular function (mean ejection fraction 0.32). There were no operative deaths and three complications. At last follow-up (mean 8.9 months) 23 patients were alive. Eight patients had one or more AICD discharges associated with symptomatic or monitored cardiac arrest. AICD implantation can be performed with low risk and appears to be an effective alternative to antiarrhythmic therapy with toxic drugs.

Serious ventricular arrhythmias accompany spontaneous coronary spasm in up to 50% of episodes in susceptible patients, 1–4 and sudden death in patients with documented variant angina pectoris is not rare. 3,5 There are, however, few reports of patients presenting with ventricular fibrillation in whom the cause of the arrhythmia has been shown to be coronary spasm. Over a 5-year period in Seattle, 6 patients were resuscitated from out of hospital cardiac arrest due to ventricular fibrillation and were later shown to have coronary artery spasm. The evidence in these patients supports the contention that coronary spasm initiated ventricular fibrillation and suggests that this mechanism may be an important cause of the sudden cardiac death syndrome.