Aims: The current study sought to assess if pre-implantation lateral-to-septal delay (LSD) > or =60 ms assessed by spectral pulsed-wave myocardial tissue Doppler imaging (PW-TDI) could predict successful long-term outcome after cardiac resynchronization therapy (CRT).
Methods and results: Sixty patients (72% males, mean age 59 +/- 10 years) who were referred for CRT according to the ACC/ESC guidelines were enrolled in the study. All patients underwent spectral PW-TDI before and 1 year after CRT. Two left ventricular (LV) dyssynchrony time intervals, T(O) and T(P) (time to onset and peak of LV myocardial velocity, respectively), LSD were recorded. Left ventricular dyssynchrony was defined as LSD > or =60 ms. Clinical response was defined as an improvement in >1 NYHA class plus improvement in 6-min walk distance (6MWD) > or =25%, echocardiographic response was defined as a > or =15% reduction in LV end-systolic volume (LV-ESV). One year after CRT, 50 patients (83%) were clinical responders and 47 patients (78%) were echocardiographic responders. Both T(O) and T(P) LV dyssynchrony indices failed to predict echocardiographic CRT outcome. In addition, there were no significant differences between 'synchronous' and 'dyssynchronous' patient populations at baseline or follow-up in either clinical (NYHA class and 6MWD) or echocardiographic (LV ejection fraction, LV end-diastolic, and end-systolic) variables.
Conclusion: The great majority of patients referred for CRT benefit clinically from it. However, spectral PW-TDI failed to predict CRT outcome. When PW-TDI dyssynchrony was applied for selection of proper CRT patients, up to 80-86% of the patients with synchronous LSD that had proven clinical and echocardiographic benefit from CRT would have been denied CRT.