QRS Area Before and After Upgrading to Cardiac Resynchronization Therapy Is Not Sufficient to Predict Outcome

QRS area reflects ventricular electrical dyssynchrony and is a stronger predictor of cardiac resynchronization therapy (CRT) outcome than QRS duration/morphology. Data on QRS area in patients upgraded from right ventricular pacing to CRT are scarce. We investigated whether QRS area and the difference with biventricular paced QRS area (ΔQRS) in CRT-upgraded patients are associated with clinical outcome and echocardiographic response. This retrospective multicenter study included patients upgraded to CRT. Median values were used as a cut-off for (Δ)QRS area. The primary composite outcome was all-cause mortality, heart transplantation or left ventricular assist device. Secondary outcomes were heart failure hospitalization (HFH) and ≥15% reduction in left ventricular end-systolic volume. A total of 303 patients were included (age 69 ± 11 years, 75% male, 50% ischemic cardiomyopathy). Median LVEF was 26% [25-34]; baseline QRS area was 132 µVs [97-162], which reduced to 90 µVs [61-122] with CRT (p < 0.001), with a ∆QRS area of 35 µVs [1-74]. The primary outcome occurred in 34.3% during 47 ± 29 months of follow-up without differences between a small or large baseline and ∆QRS area (p = 0.856; p = 0.968). HFH occurred in 9.2% and patients with large ∆QRS area had fewer HFHs (6.7% versus 15.4%, p = 0.012). Baseline QRS area of >132 µVs was not associated with HFH (p = 0.832), but was a determinant of better echocardiographic response (OR 2.23, 95% CI 1.10-4.50, p = 0.026). ∆QRS area of >35 µVs was not associated with echocardiographic response (p = 0.203). To conclude, (∆)QRS area was not associated with the primary outcome in this small cohort of CRT-upgraded patients. However, baseline QRS area of >132 µVs was associated with echocardiographic response and ∆QRS area of >35 µVs with fewer HFHs.