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Therapeutics

Atrial pacing was better than ventricular pacing for the sick-sinus syndrome

ACP J Club. 1998 May-June;128:62. doi:10.7326/ACPJC-1998-128-3-062


Source Citation

Andersen HR, Nielsen JC, Thomsen PE, et al. Long-term follow-up of patients from a randomised trial of atrial versus ventricular pacing for sick-sinus syndrome. Lancet. 1997 Oct 25;350:1210-6.


Abstract

Objective

To compare the long-term effectiveness of atrial pacing and ventricular pacing for patients with the sick-sinus syndrome.

Design

Randomized controlled trial with mean follow-up of 5.5 years.

Setting

A university-based hospital in Aarhus, Denmark.

Patients

225 patients (mean age 76 y, 63% women) referred for their first pacemaker between May 1988 and December 1991 {who had symptomatic bradycardia < 50 beats/min or QRS pauses > 2 seconds. Exclusion criteria were age < 50 years; grade 1, 2, or 3 atrioventricular block; chronic atrial fibrillation (AF), AF > 50% of the time, AF with RR interval > 3 seconds, or AF with QRS rate < 40 beats/min; bifascicular bundle-branch block; hypertension; cancer; cerebral disease; stroke within the past 3 months; planned surgery; and Wenckebach block < 100 beats/min}*.

Intervention

Patients were stratified by age and allocated to single-chamber atrial (n = 110) or ventricular pacing (n = 115).

Main outcome measures

Outcomes included mortality (all-cause, cardiovascular), AF, heart failure, and freedom from thromboembolic events and chronic AF.

Main results

Analysis was by intention-to-treat. Compared with those who received ventricular pacing, patients who received atrial pacing had lower all-cause mortality (P = 0.05)†, lower cardiovascular mortality (P = 0.007)† (Table), and less severe heart failure (P < 0.05)†. Fewer patients who received atrial pacing had AF (relative risk [RR] 0.54, 95% CI 0.33 to 0.89, P = 0.01)† and more patients who received atrial pacing were free from thromboembolic events (RR 0.47, CI 0.24 to 0.92, P = 0.02)† and chronic AF (RR 0.35, CI 0.16 to 0.76, P = 0.004)† than those who received ventricular pacing.

Conclusions

Patients with the sick-sinus syndrome who received atrial pacing had lower all-cause and cardiovascular mortality and less severe heart failure than those who received ventricular pacing. More patients who received atrial pacing were free from thromboembolic events and chronic atrial fibrillation.

Sources of funding: Danish Heart Foundation and Sygekassernes Helsefond.

For article reprint: Dr. H.R. Andersen, Department of Cardiology, Skejby Sygehus, Aarhus University Hospital, 8200 Aarhus N, Denmark. FAX 45-8942-1109.

*Andersen HR, Thuesen L, Bagger JP, Vesterlund T, Thomsen PE. Lancet. 1994;344:1523-8.

†Based on survival analysis.


Table. Atrial pacing vs ventricular pacing for the sick-sinus syndrome†

Mortality Atrial pacing EER Ventricular CER RRR (95% CI) ARR |EER-CER| NNT (CI)
All-cause 35.5% 49.6% 28.5% (2.7 to 47.9) 14.1% 7 (4 to 84)
Cardiovascular 17.3% 33.9% 49.1% (18.5 to 68.6) 16.6% 6 (4 to 19)

†Abbreviations defined in Glossary; RRR, ARR, NNT, and CI calculated from data in article, based on final proportions.


Commentary

Providing further follow-up on their previous study (1), Andersen and colleagues report reduced mortality and morbidity associated with atrial pacing compared with ventricular pacing.

The sick-sinus syndrome is a cause of paroxysmal AF. Electrical stabilization of the atria and avoidance of retrograde ventriculoatrial conduction probably explain the reduction in AF. This reduction, in turn, leads to less heart failure and thromboembolism. The reduction in heart failure could reflect preserved atrioventricular synchrony and atrial systole because atrial systole may account for 20% to 30% of stroke volume in elderly patients and in patients with diastolic dysfunction. The benefits of reducing heart failure are apparent in this study and are particularly important for elderly patients who often have cardiovascular comorbid conditions.

A hypercoagulable state may be related to intra-atrial stasis consequent on ventricular pacing and the association with AF per se; the avoidance of this by using atrial pacing reduces thromboembolic risk (2).

The study by Andersen and colleagues firmly establishes the role of atrial pacing in patients with the sick-sinus syndrome, and such patients referred for pacemakers should receive the procedure. Some may argue that only 20% of the patients screened were randomized and thus question the generalizability of the results. Nevertheless, the selection of appropriate patients with the sick-sinus syndrome was based on stringent inclusion criteria. The future role of the atrial defibrillator in reducing paroxysmal AF and atrioventricular nodal modification may result in less AF but is less likely to confer the other benefits of pacemaker therapy.

Gregory Y.H. Lip, MD
University Department of Medicine City HospitalBirmingham, England, UK


References

1. Andersen HR, Thuesen L, Bagger JP, Vesterlund T, Thomsen PE. Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome. Lancet. 1994;344:1523-8.

2. Gibbs C, Blann AD, Lip GY. Thromboembolic risk and pacemakers. Lancet. 1997;350:1780-1.