Prevalence, circumstances, mechanisms, and risk stratification of sudden cardiac death in unipolar single-chamber ventricular pacing.

Abstract

BACKGROUND Permanent cardiac pacing is well established for the improvement of prognosis and quality of life in patients with severe bradycardia. However, sudden cardiac death still remains an unresolved problem, as it occurs in approximately 20-30% of paced patients. This 2-year follow-up study was directed at prospectively assessing prevalence, circumstances, and mechanisms of sudden death in 2,021 permanently paced patients. METHODS AND RESULTS During the observation period, 220 patients (11%) died (mean pacing interval, 50.5 +/- 7 months). Lethal cerebrovascular events in 66 of 220 patients (30%) and sudden death in 49 of 220 patients (23%) were the two most frequently reported modes of death. Nonsudden (first year, 20%; subsequent years, 6.9%; p less than 0.01) and sudden death mortality rate (4% versus 1.8%, p less than 0.05) were highest during the first year. Mortality was unrelated to the patient's activity status at the time of death. Sudden cardiac death occurred more often in male patients (increased risk, 1.7 versus female patients; p less than 0.001) and patients younger than 60 years of age (5.2 versus patients older than 60 years, p less than 0.001). Patients with severe bradycardia (sudden death rate, 28%), severe atrioventricular block (25%), or atrial fibrillation with low ventricular rate (25%) before pacemaker implantation were more likely to suffer from sudden cardiac death than patients with previous syncopal attacks (sudden death rate, 15%) or sick sinus syndrome (17%). The highest incidence of sudden death was observed in patients with bifascicular and trifascicular bundle branch block. In this group, 35% of patients died suddenly during the follow-up period compared with 18% of patients without bundle branch block. In a subsequent study in 90 consecutive patients with various types of bundle branch block, undersensing of up to 13% of ectopic ventricular beats occurred in patients with bifascicular block. Pacing-induced tachyarrhythmias and ventricular fibrillation were documented in 10% of undersensed ectopic ventricular beats as well as in the setting of atrial fibrillation associated with ventricular arrhythmias. CONCLUSIONS Young age, male sex, and a severely diseased heart indicated by the presence of bifascicular and trifascicular bundle branch block are the strongest predictive clinical parameters for sudden cardiac death, especially in the first year after pacemaker implantation.

Proarrhythmic Effect of Pacemaker Stimulation in Patients With Implanted Cardioverter-Defibrillators

“…Because of the similarity of QRS morphologies, it would otherwise have to be assumed that the VTs originated exclusively from the localization of the electrode tip. Other published ECGs, including our own example, however, cannot prove without a doubt that the tachycardia was mediated by the stimulated impulse, because VTs with the same morphology had also occurred in the absence of a preceding pacemaker stimulation (Figure 1 of Callans et al, 9 Figures 1 and 2 of Goldman et al, 6 Figures 5 and 6 of Zehender et al 8 ).…”

“…8 Several pacemaker recipients have structural heart disease, and PITs may occur that lead to lethal tachyarrhythmias in these patients. Therefore, with the results of the MADIT II study in mind, we recommend that for patients with paroxysmal bradycardia and structural heart disease with depressed left ventricular function, the indication for the implantation of an ICD instead of a pacemaker should be discussed.…”

Task Force on Sudden Cardiac Death of the European Society of Cardiology

“…Roelandt et al [71] found a bradyarrhythmia ending in asystole in 2 of 10 instances of SCD during ambulatory ECG recording, while Kempf and Josephson [72] found a bradyarrhythmia in 7 of 27 patients experiencing SCD during long-term ECG recording. Although the presence of a bifascicular and trifascicular bundle branch block is strongly predictive of SCD [73] , the mechanism of death may not be bradycardia since the conduction system disease may merely reflect more extensive myocardial damage, thus increasing the chance of a tachyarrhythmia. In 2021 patients with permanent pacemaker implantation, 220 patients (11%) died over a mean pacing interval of 50·5 7 months.…”

“…The mechanism of SCD is still unclear, but may be due to bradycardia dependant prolongation of repolarization and refractoriness, mainly in the first 24 h after the procedure, particularly in those patients where the duration of repolarization is already prolonged [73,492] . Recommendations for dealing with this problem include pacing at relatively high rates and continuous ECG monitoring during the vulnerable period of the first 24 h after the procedure.…”

“…Zehender et al reported 23% incidence of SCD in paced patients [73] . The SCD rate was three times higher during the first year following pacemaker implantation than in subsequent years.…”