Cardiac resynchronization therapy--clinical and echocardiographic characteristics of responders and exceptional responders

Abstract

Cardiac resynchronization therapy (CRT) is a novel treatment for systolic heart failure and in successful cases reverse remodeling occurs with reduction of left ventricular (LV) dimensions and volumes. The term "responders" applies to all patients who improve in functional class and quality of life; however, some responders show exceptional improvement, including normalization of clinical and echocardiographic parameters (exceptional or super-responders).

Objective: The purpose of our study was to analyze responders (R) and super-responders (SR).

Methods: 36 patients were referred for CRT due to depressed left ventricular function (mean ejection fraction 26 +/- 6.9%) and QRS duration (QRSd) of 175 +/- 29.9 ms. All patients underwent complete 2D, Doppler, and tissue Doppler (TDI) echocardiography before and after CRT (performed 3-6 months after CRT implantation) and measurement of pro-BNP. Twelve were non-responders (nR--Group I). Of the 24 patients showing improvement in NYHA functional class (responders), 11 were classified as super-responders with ejection fraction > or =40% (Group II--13 patients [R] and Group III--11 patients [SR]).

Results: There were no differences between the three groups in QRSd or the following baseline echocardiographic parameters: LV dimensions and volumes, ejection fraction, TDI velocities and dyssynchrony parameters. The exception was left atrial (LA) dimensions (greater in group I) and mitral inflow, with a predominant restrictive pattern in Group I. Baseline maximum VO2 was lower in Group I compared to Group III (13 vs. 21 mm/kg/min, p < 0.0001). We compared the three groups during a mean follow-up of 15 +/- 8 months. Group II showed slight improvement of left ventricular function without statistical significance, only pro-BNP showing a significant reduction (p = 0.04). Comparing Groups I and III, there were differences in the super-responder group for pro-BNP and echocardiographic LV dimensions, volumes and ejection fraction, LA dimensions, pulmonary artery pressure and TDI velocities, with normalization of septal systolic velocity: Group III--5.13 cm/s vs. Group I--2.95 cm/s, p = 0.001.

Conclusion: The degree of improvement in CRT patients is difficult to predict by baseline echocardiography and QRSd, only a restrictive mitral inflow pattern appearing to be a determining factor. Remodeling in super-responders is probably due to a structural process, with a trend towards normalization of ejection fraction and other systolic parameters.