Description: Aims Prognostic benefit from CRT compared with controls is well established. Symptomatic response rates, however, are controversial and have never been systematically evaluated with standard subtraction of control rates to establish the incremental symptomatic response effect of CRT pacing. Methods and results First, we identified 150 consecutive CRT papers and assessed researchers' perceptions of the symptomatic response to CRT. The mean quoted response rate was 66%. Only 26 studies acknowledged the existence of response without the device. Secondly, we examined actual symptomatic response rates in the randomized trials (CARE-HF, COMPANION, CONTAK-CD, MIRACLE, MIRACLE-ICD, MIRACLE-ICD II, MUSTIC, and REVERSE) totalling 3904 patients. The NYHA status improved in 51% of those randomized to CRT vs. 35% of controls (incremental effect 16%). This incremental improvement was significantly greater in open studies (with no device for controls) than in blinded studies (control arm receiving a device but no CRT, such as a defibrillator or a CRT programmed off), 20% vs. 13%, P 〈 0.001. Conclusions Quoting CRT responder rates in isolation without recognizing spontaneous ‘response’ is common but unwise. The incremental symptomatic response rate from CRT pacing is ~16%, much lower than widely reported. This value is similar to that for drugs in heart failure and should not be considered disappointing: they both exert powerful prognostic benefits. For scientific purposes, e.g. to explore potential improvements, symptomatic benefit from CRT should be quantified, like all other effects, by comparison with a control.

Description: Aims For patients with refractory atrial fibrillation (AF) undergoing atrioventricular nodal ablation (AVNA), initial single-chamber right ventricular (RV)-only pacing is standard. Given the deleterious effects of chronic RV-only pacing, the impact of an initial biventricular (BiV) pacing strategy post-ablation is of interest. Methods and results We conducted a meta-analysis to determine the effect of BiV vs. RV-only pacing in patients undergoing AVNA for refractory atrial fibrillation. A search of multiple electronic databases identified 921 reports, which included four randomized controlled trials ( n = 534). Mean New York Heart Association (NYHA) class was 2.3 and mean left ventricular ejection fraction (LVEF) was 44%. When compared with RV-only pacing, BiV pacing was not associated with reduced mortality [risk ratio 0.85, 95% confidence interval (CI) 0.40–1.82, P = 0.68]. In three studies comprised of patients with left ventricular systolic dysfunction (mean EF 41 ± 3%), BiV pacing demonstrated a non-significant reduction in cardiac mortality (risk ratio 0.59, 95% CI 0.25–1.39; P = 0.23). Compared with RV-only pacing, BiV pacing was associated with significant improvement in symptoms [Minnesota Living with Heart Failure Questionnaire (MLWHFQ) 2.72 points fewer, 95% CI 1.45–3.99] and increased LVEF (+2.6%, 95% CI 1.69–3.44), but no significant change in 6 min walk distance (6MWD) (5.02 ms more, 95% CI –1.56 to 11.59; P = 0.13). Conclusions In patients with refractory AF undergoing AVNA, BiV pacing was not associated with significantly improved survival when compared with RV-only pacing. A modest, but significant improvement in structural and functional response to BiV pacing was observed.