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Left Ventricular Versus Simultaneous Biventricular Pacing in Patients With Heart Failure and a QRS Complex ≥120 Milliseconds
Study Questions:
Does isolated left ventricular (LV) pacing provide improved exercise tolerance and LV remodeling, as compared with biventricular (BiV) pacing in patients with systolic heart failure?
Methods:
This was a multicenter, randomized, double-blind crossover study of BiV pacing versus LV pacing (6 months for each pacing modality) in patients with an LV ejection fraction ≤35% and QRS ≥120 ms. All patients underwent electrocardiograms (ECGs) with atrioventricular optimizations, echocardiograms, and a maximal and submaximal exercise test. The primary outcome of interest was the duration at submaximal exercise, defined as the number of minutes spent at 75% of peak VO2 in the LV versus BiV pacing groups. An increase ≥20% baseline was considered a “clinical response.” Secondary outcomes included changes in LV remodeling, New York Heart Association (NYHA) class, and quality-of-life metrics.
Results:
The mean ± standard deviation patient (n = 121) age was 60.9 ± 8.8 years, 25% were female, and 67% were NYHA class III-IV. At baseline, the mean LVEF was 24 ± 6%, the QRS duration was 155 ± 23 ms, and 69% and 4% had a typical left bundle branch block and right bundle branch block morphology, respectively, on ECG. After 6 months of therapy, 48% and 55% of LV pacing and BiV pacing patients, respectively, achieved a ≥20% increase in submaximal exercise duration (p = 0.16). Favorable reverse remodeling (≥15% reduction in LV end-systolic volume) was found in 47% and 55% of LV and BiV pacing, respectively (p = 0.088). Of the 51 (42%) nonresponders to LV pacing, 16 (31%) responded to BiV pacing based on exercise duration. Of the 44 (45%) nonresponders to BiV pacing, nine (21%), responded to LV pacing. Rates of adverse events did not differ. No differences in quality of life or NYHA class based on pacing modality were noted.
Conclusions:
The authors concluded that while LV pacing is not superior to BiV pacing, nonresponders following BiV therapy may respond to LV pacing.
Perspective:
Isolated RV apical pacing has been shown to negatively impact LV function. It is also hypothesized that the RV pacing component to BiV resynchronization could be deleterious in patients with HF. In this very nicely designed trial, LV and BiV pacing appear to offer similar outcomes overall. However, 20% of BiV nonresponders improved clinically after LV pacing. Thus, while overall cohort outcomes were similar, some patients may ‘prefer’ LV pacing (and vice versa). This may be related to alterations in electrical contraction or diastology during LV versus BiV pacing. Longer-term follow-up and rehospitalization and mortality data would be of interest on further study. It would also be of interest to know if LV pacing leads to longer device life and, therefore, fewer device replacements.
Keywords: Exercise Tolerance, Follow-Up Studies, Cross-Over Studies, Electrocardiography, New York, Heart Failure, Systolic, Carcinogens, Cardiac Resynchronization Therapy, Cardiac Pacing, Artificial, Quality of Life, Immunodeficiency Virus, Bovine, Ventricular Remodeling, Bundle-Branch Block, Echocardiography, Exercise Test
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