Right ventricular (RV) pacing is used in patients presenting with high degree atrioventricular block, both to relieve symptoms related to bradycardia and improve prognosis. The majority of these patients are elderly and many of them will have a degree of co-existing left ventricular dysfunction which may be exacerbated by the electrical and mechanical dyssynchrony that occurs with RV pacing. The large cardiac-resynchronization (CRT) pacing studies performed to date have systematically excluded patients with indications for standard bradycardia pacing devices so as to concentrate solely on the benefits derived from cardiac resynchronisation, and consequently there is a paucity of data regarding this group.
In this large multi-centre randomised controlled trial 691 patients were enrolled who had indications for pacing for high degree AV block and also had NYHA class I, II, or III heart failure, and a left ventricular ejection fraction of 50% or less (mean 40%). Patients received a CRT device (+/-cardioverter-defibrillator) and were randomly assigned to standard right ventricular pacing or biventricular pacing. The primary outcome was the time to death from any cause, an urgent care visit for heart failure that required intravenous therapy, or a 15% or more increase in the left ventricular end-systolic volume (LVESV) index. Patients were followed up for an average of 37 months and the outcome favoured biventricular pacing. The primary outcome occurred in 190 of 342 patients (55.6%) in the right-ventricular-pacing group, as compared with 160 of 349 (45.8%) in the biventricular-pacing group (HR, 0.74; 95% CI, 0.60 to 0.90) although it should be noted this was primarily driven by a change in LVESV index rather than a true clinical end-point. Results were similar in the pacemaker and ICD groups and left ventricular lead-related complications occurred in 6.4% of patients.
In this large industry-sponsored trial, biventricular pacing was superior to conventional right ventricular pacing in patients with high degree atrioventricular block and co-existing left ventricular systolic dysfunction.
- Curtis AB, Worley SJ, Adamson PB, Chung ES, Niazi I, Sherfesee L, Shinn T and Sutton MS. Biventricular pacing for atrioventricular block and systolic dysfunction. N Engl J Med. 2013 Apr 25;368(17):1585-93.