Notched QRS complex in lateral leads as a novel predictor of response to cardiac resynchronization therapy

Notched QRS (nQRS) may be an indicator of ventricular delay. There are very few studies investigating the value of nQRS. The aim of the study was to identify the predictive value of nQRS for response to cardiac resynchronization therapy (CRT).

Eighty-two patients with heart failure (HF) and widened QRS (≥120 ms) were implanted with a CRT device. nQRS was defined as presence of ≥2 R waves, or ≥1 notch in the R wave or S wave in ≥2 contiguous leads. Response to CRT was defined as percentage of left ventricular end-systolic volume (LVESV) reduction after 6 months CRT (ΔLVESV%) ≥15%.

nQRS was presented in 62 (76%) patients, 16 of whom had nQRS in anterior leads, 47 in inferior leads, and 42 in lateral leads. The rate of CRT response (65% vs 50%, P = 0.29) and ΔLVESV% (21.7 ± 31.7% vs 7.9 ± 25.4%, P = 0.09) were not different between patients with and without nQRS. But the rate of CRT response was higher in patients with nQRS in lateral leads (nQRS-L) than in those without nQRS-L (76% vs 45%, P = 0.006). ΔLVESV% was greater in patients with nQRS-L than in those without nQRS-L (25.2 ± 34.3% vs 10.1 ± 24.5%, P = 0.004). After adjusting for potential confounders including QRS duration, presence of nQRS-L still predicted positive CRT response (OR = 4.04, P = 0.009).

nQRS-L may be a novel predictor of response to CRT in patients with HF and widened QRS. Large-scale studies are needed to confirm this prognostic value of nQRS-L.