Volume overload modulates effects of cardiac resynchronization therapy independently of myocardial reperfusion: results of the RESYNC study

OBJECTIVES: Cardiac resynchronization therapy (CRT) may induce significant changes in regional wall motion and perfusion. However, the link between these variables in patients with heart failure has not been investigated. METHODS: Thirty-six patients with idiopathic (n = 22) or ischemic (n = 14) cardiomyopathy (mean age 70 +/- 8 years, 24 male) were studied by echocardiography and gated single-photon emission computed tomography (SPECT) before and within 2 months after CRT. RESULTS: New York Heart Association class improved in all but four patients. The perfusion analysis indicated that, in all but three patients, there was a significant improvement of tracer uptake. Baseline end-diastolic volume index obtained by gated SPECT modulated increase of ejection fraction (P < 0.001), reduction of end-systolic volume index (P < 0.01) and improvement of motion (P < 0.001), as well as of left ventricular wall thickening (P < 0.002). Finally, despite CRT inducing significant reperfusion independently of volume overload (P < 0.05), extension of perfusion defect correlated with global improvement in the follow-up (P < 0.05). CONCLUSIONS: Volume overload may identify responders to resynchronization therapy. CRT induced a significant 'reperfusion' both in ischemic and idiopathic cardiomyopathies, even if this is not sufficient to improve left ventricular function in patients with more severe volume overload. Finally, simultaneous evaluation of volume overload and perfusion defects may result useful in identifying CRT responders.