Alan X. Zhu

Comparison of automatic and patient-activated arrhythmia recordings by implantable loop recorders in the evaluation of syncope

The implantable loop recorder (ILR) has become an important tool for evaluating patients with recurrent syncope. Second generation ILRs have the ability to record events either automatically (auto activated) or by manual activation (patient activated). In an attempt to evaluate the relative utility of the auto-activation feature, this study stratified ILR events based on a grading system designed to classify detected arrhythmias in terms of the likelihood that they provide a diagnostic basis for syncope. Data from 50 patients (27 men, mean age 64 ± 22 years) who underwent ILR implantation for investigation of recurrent syncope were assessed. The arrhythmia syncope grading system used 5 levels, ranging from grade 0 (rhythm recorded during syncope) to grade IV (rhythm unlikely to provide a diagnostic basis for syncope). Thirty-six patients (72%) demonstrated ≥1 auto-activated or patient-activated recording during a follow-up of 14.3 ± 7.9 months. Of the total of 529 recordings, 223 (194 after auto activation [86.9%]) from 30 patients showed a rhythm abnormality. Auto activation was more effective for documenting arrhythmias that were recorded during syncope or those with highest probability of providing a syncope diagnosis (grade 0 or I arrhythmias: auto activated, 19 patients, patient activated, 3 patients). Times from ILR implantation to first grade 0 and grade I arrhythmias were 13.4 and 7.8 months, respectively. The ILR auto-activation feature proved effective in providing a high probability basis for syncope (196 arrhythmia recordings [87.1%] in 27 patients) and enhanced the diagnostic effectiveness of the device compared with patient activation alone (29 arrhythmia recordings [12.9%] in 6 patients).

Biventricular implantable cardioverter defibrillators improve survival compared with biventricular pacing alone in patients with severe left ventricular dysfunction.

Introduction: Biventricular cardiac pacemakers provide important hemodynamic benefit in selected patients with heart failure and severe left ventricular (LV) dysfunction. Nevertheless, these patients remain at high mortality risk. To address this issue, we examined mortality outcome in patients with heart failure treated with biventricular pacemakers alone and those treated with biventricular implantable cardioverter defibrillators (ICDs).

Efficacy of biphasic waveform cardioversion for atrial fibrillation and atrial flutter compared with conventional monophasic waveforms

B on extensive experience with implantable cardioverter-defibrillators and automatic external defibrillators, the utility of biphasic transthoracic shock has been demonstrated in the setting of lifethreatening ventricular tachyarrhythmias. These observations have led to the application of biphasic waveforms during elective transthoracic cardioversion for atrial fibrillation (AF). The present report compares cardioversion outcomes in 2 sequential groups of patients with AF undergoing transthoracic cardioversion. It was undertaken in an attempt to ascertain the extent to which biphasic waveform technique enhances transthoracic AF cardioversion success rates. • • • Records of 145 patients were reviewed. The patients were referred to our center for elective transthoracic cardioversion between January 1999 and September 2001, and had undergone this procedure in the electrophysiologic laboratory. Patients with atrial flutter (20 patients, 14%) were also included because of the similarity of the arrhythmia and the treatment required. Demographic and clinical data—including arrhythmia type and duration, underlying disease, and concomitant medications—were documented, along with echocardiographic data including left atrial diameter and left ventricular ejection fraction. Procedural data—including the number of cardioversion attempts made, energy levels used, and anesthetic employed— were documented. Similarly, complications were recorded, particularly skin irritation. A successful cardioversion procedure was defined as restoration of sinus rhythm for 1 cycle after energy application. Recurrence of the arrhythmia 2 hours after a successful cardioversion (i.e., before the patient left the observation unit) was deemed an “early recurrence.” The statistical significance of the efficacy of biphasic waveform cardioversion compared with monophasic waveform shock cardioversion was evaluated using chi-square and Fisher’s exact tests. A p value of 0.05 was considered statistically significant. Data were obtained in 145 sequential patients who underwent elective electrical cardioversion for AF or atrial flutter. Eighty-two patients (mean age 67 15 years) received biphasic waveform cardioversion, and the remaining 63 patients (mean age 66 14 years) underwent cardioversion with a monophasic waveform device. The ratio of men to women was 1.8:1 and 2:1 for the biphasic and monophasic waveform cardioversion study groups, respectively. The presenting arrhythmia was AF in 70 patients (85%) in the biphasic group and in 55 patients (87%) in the monophasic group. Atrial flutter was present in 12 patients (15%) in the biphasic group and in 8 patients (13%) in the monophasic group. The mean duration of patients’ treatment for the arrhythmia event was 36 56 and 60 106 days (p NS) for the biphasic and monophasic groups, respectively. Baseline clinical characteristics for patients in each treatment group are listed in Table 1. Underlying disease processes (i.e., cardiomyopathy, coronary artery disease, valvular heart disease, lung disease, and other structural heart disease) were found to be similarly prevalent in both treatment groups. Patients in the monophasic waveform group tended to use more digoxin, amiodarone, and other antiarrhythmic medications compared with biphasic group patients. The frequencies of usage of blockers, calcium channel blockers, and angiotensin-converting enzyme inhibitors were similar in both groups. The mean left atrial diameter was 46 10 mm in the biphasic group and 45 12 mm in the monophasic waveform group. Mean left ventricular ejection fraction was similar for the biphasic and monophasic groups (49 13% and 49 15%, respectively). Procedure success rate was 99% (81 patients) in the biphasic waveform cardioversion group compared with 81% (51 patients) in the group treated with monophasic waveform (p 0.001). The mean energy required for procedural success was 126 46 J and 228 83 J for the biphasic and monophasic waveform groups, respectively (p 0.001). The mean number of attempts before achieving procedural success was 1.3 0.8 for the biphasic cardioversion group and 1.2 0.4 for the monophasic cardioversion group. The treated arrhythmia recurred in 10 biphasic group patients (12%) and in 6 monophasic group patients (12%). All recurrences were in patients with AF. Skin irritation was not observed in any of the patients who received biphasic waveform shock, whereas 2 patients (3%) who received monophasic waveform shock required topical treatment for irritation at patch sites. • • • From the Cardiac Arrhythmia Center, Cardiovascular Division, Department of Medicine, Minneapolis, Minnesota. Dr. Ermis is supported in part by a grant from the Midwest Arrhythmia Research Foundation, Minneapolis, Minnesota. Dr. Benditt’s address is: Cardiac Arrhythmia Center, MMC 508, 420 Delaware Street, Minneapolis, Minnesota 55455. Manuscript received April 9, 2002; revised manuscript received and accepted June 7, 2002.

Improved survival of cardiac transplantation candidates with implantable cardioverter defibrillator therapy: role of beta-blocker or amiodarone treatment.

Introduction: Survival in patients awaiting cardiac transplantation is poor due to the severity of left ventricular dysfunction and the susceptibility to ventricular arrhythmia. The potential role of implantable cardioverter defibrillators (ICDs) in this group of patients has been the subject of increasing interest. The aims of this study were to ascertain whether ICDs improve the survival rate of patients on the waiting list for cardiac transplantation and whether any improvement is independent of concomitant beta‐blocker or amiodarone therapy.