The importance of nuclear cardiology in prediction and measure of effectiveness of cardiac resynchronization therapy

Objectives Our aim was to investigate the diagnostic importance of different nuclear cardiology methods in predicting and/or measuring the effectiveness of cardiac resynchronization therapy (CRT) in severe heart failure.

Methods 15 patients (pts) with severe heart failure (HF) - EF<30%, QRS>120 ms - in NYHA III-IV. clinical stage underwent nuclear cardiology procedures. In 11 pts ischemic heart disease (IHD), in 4 pts only hypertension - without IHD - was responsible for HF. Before CRT gated myocardial perfusion scintigraphy (GMPS) was performed in every case to distinguish the viable and necrotic myocardium and to measure functional parameters as well. Before and 6 months after CRT all 15 pts had planar and SPECT MUGA (multiple gated acquisitions) to analize the left ventricular (LV) and right ventricular (RV) function, phase angle (phase histogram) and synchrony (S).

Results GMPS showed small necrosis only in 2 cases (2/15), while intraventricular dyssynchrony, wide phase angle was detected in every case. (On phase angle a separete peak appeared in the place of necrotic myocardium.) Before CRT planar and SPECT MUGA showed low LVEF (10-28%) in every case (15/15), moreover in 3/15 cases RVEF was decreased as well (20-38%). Inter and/or intraventricular mechanical dyssinchrony, wide phase angle was detected in every case, too. After CRT the clinical stage and LVEF improved significantly in every case. Unexpectedly RVEF decreased in 1 case but improved in 2 cases. We experienced significant S improvement in 13/15 cases and in the same 13/15 cases the phase angle shortened.

Conclusions GMPS can predict the effectiveness of CRT distinguishing the necrotic (responsible for "nonresponder to CRT") and viable but dyssynchronic myocardium ("responder to CRT"). Planar and SPECT MUGA proved to be excellent methods to measure the response to CRT