Electrocardiographic identification of Para-Hisian right ventricular pacing predicts response to cardiac resynchronization therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves outcomes in patients with heart failure and electrical dyssynchrony; however, electrocardiographic markers identifying a favorable right ventricular (RV) pacing configuration have not been well established. OBJECTIVE: To evaluate whether an electrocardiography (ECG)-defined classification of RV pacing is associated with electrical and echocardiographic response to CRT. METHODS: We retrospectively studied 33 consecutive patients who underwent CRT-pacing. RV pacing configuration was classified using predefined ECG criteria consisting of an R wave in lead I, a lead III/II R-wave ratio < 1 or inferior lead discordance, positive polarity in lead aVL, and absence of His bundle capture. Patients fulfilling all criteria were classified as the ECG-defined para-Hisian pacing (PHP) group (n = 7), and the remaining patients comprised the non-PHP group (n = 26). Electrocardiographic and echocardiographic parameters were compared at baseline and after 6 months of follow-up. RESULTS: At 6 months, patients in the PHP group demonstrated significantly narrower QRS duration than those in the non-PHP group (123.4 ± 11.4 ms vs. 151.9 ± 20.2 ms, P < 0.01). The PHP group also exhibited greater reductions in left ventricular end-systolic volume (-34.8 ± 13.1% vs. -3.3 ± 31.3%, P < 0.05) and greater improvement in left ventricular ejection fraction (12.6 ± 8.7% vs. 4.0 ± 10.2%, P < 0.05). Heart failure hospitalization rates were similar between groups. CONCLUSIONS: An ECG-defined para-Hisian RV pacing configuration was associated with greater electrical resynchronization and improved left ventricular reverse remodeling following CRT. These findings suggest that ECG characteristics of RV pacing may help identify a favorable pacing configuration and warrant validation in larger prospective studies.