Effect of Cardiac Resynchronization Therapy on Left Ventricular Diastolic Function: Implications for Clinical Outcome

Background: The definition of response to cardiac resynchronization therapy (CRT) remains controversial, with variable rates of response depending on the criteria used. Our aim was to analyze the impact of CRT on diastolic function in different degrees of response, particularly in patients with positive clinical but no echocardiographic response. Methods and Results: In 250 CRT patients clinical evaluation and echocardiography were performed before and after CRT. Absolute response to CRT was defined as a reduction in left ventricular (LV) end-systolic volume of >= 15% at 1-year follow-up. Additionally, patients were classified into 4 subgroups according to their amount of response: extensive reverse remodeling (RR), slight RR, clinical response without RR, and neither clinical response nor RR. An improvement in estimates of LV filling pressure and a decrease in left atrial dimensions were observed only in responders to CRT. Patients with clinical but no echocardiographic response had significant improvement in E-wave and deceleration time and nonsignificant improvement in other parameters. Conclusions: LV diastolic function improves with CRT. Clinical responders without echocardiographic response show improvement in parameters of diastolic function. That suggests that clinical-only response to CRT is secondary to a real effect of the therapy, rather than a placebo effect.