Aim: Clinical experience shows that about 2 out of 3 patients with indication to resynchronization therapy (CRT) may have improvements in NYHA class, echocardiographic parameters and survival. However, specific clinical or technical parameters that identify responder patients have not yet been found. Aim of the present study was to assess the efficacy of CRT and to estimate the predictive value of specific echocardiographic parameters.
Methods: All patients who underwent CRT from January 2004 till June 2009, at our Institution, were clinically examined and evaluated by echo and ECG before implant. Between January and February 2010, among a population of 55 patients (41 M, 14F, mean age 66.3±5.9), 42 patients (33 M) were considered in the final multiparametric analysis. Of the 13 excluded patients, 6 died, 2 underwent cardiac transplantation and 5 were lost to follow-up. Basal characteristics of the study population were: ischemic etiology in 15 out of 42 patients, back-up defibrillation in 39 patients. The mean follow-up period was 26.2±13.0 months. Patients had been classified as CRT responders if they showed an inverse left ventricle (LV) remodeling, defined as a 10% reduction of end-diastolic diameter (LVEDD) compared to the basal measure.
Results: Echo parameters significantly improved after CRT: LVEDD was significantly (P<0.05) reduced (basal vs. CRT: 76±7 mm vs. 64±10 mm, P=0.00004); basal ejection fraction (EF) was 21±5% vs. 37±14% after CRT (P=0.00001); mitral regurgitation (MR) (grading from 1 to 4) was 2.8±0.6 vs. 2.3±0.9 (P=0.00998); QRS duration was 157±25 ms vs. 135±23 ms (P=0.00036), and NYHA class 2.6±0.5 vs. 2.1±0.4, P=0.00006). Only a positive trend of the E/A ratio was observed (P=0.088). Among 42 patients, 24 (57%) had an inverse LV remodeling and were defined as CRT responders. By comparing responder with no-responder patients, the basal values of echo parameters like EF, LVEDD, MR, QRS, NYHA class were similar in the two groups; while E/A was statistically different between the two groups (P=0.02), being less severe in responder patients.
Conclusion: Our experience confirms that about 2 out of 3 patients are responder to CRT and their clinical improvements remain stable in a long term follow-up. Patients with a less severe E/A ratio are more likely to improve their clinical condition as shown by the reverse remodeling measured through the LVEDD.