Effect of left ventricular endocardial activation pattern on echocardiographic and clinical response to cardiac resynchronization therapy

Objective: To explore the left ventricular (LV) electrical activation pattern in heart failure (HF) and its implication to cardiac resynchronization therapy (CRT). Design and setting: Observational study at the University Teaching Hospital. Patients: 23 optimally treated patients with HF with New York Heart Association class III, QRS duration > 120 ms and LV ejection fraction < 35%. Interventions: The LV endocardial activation pattern and total activation time (Tat) was determined by non-contact mapping and the LV mechanical dys-synchrony was determined by standard deviation (Ts-SD) and maximal difference (Ts-diff) of time to peak systolic contraction (Ts)among 12 LV segments using tissue Doppler imaging before receiving CRT. Main outcome measures: Correlation between electrical and mechanical dys-synchrony; volumetric responder to CRT at 3 months; HF hospitalisation or death by Kaplan-Meier analysis. Results: Homogenous (type I, n = 8) and presence of conduction block (type II, n = 15) patterns were identified. Significant correlation between Tat and Ts-SD/Ts-diff was noted only in type II (r = 0.73/0.56, p = 0.002/0.03). Ts-SD and Ts-diff in type II were significantly longer than type I. 12 patients in type II and 2 in type I were CRT responders (p = 0.01). After 487 ( 447) days, patients with type II pattern had significantly lower risk of HF hospitalisation or death than those with type I (log rank chi(2) = 5.25; p = 0.02). Conclusion: Patients with type II LV endocardial activation pattern had a more favourable echocardiographic and clinical response to CRT than those with type I pattern.