Utility of Equilibrium Radionuclide Angiogram–Derived Measures of Dyssynchrony to Predict Outcomes in Heart Failure Patients Undergoing Cardiac Resynchronization Therapy

Abstract

We evaluated a novel scintigraphic method using new parameters of mechanical left ventricular (LV) dyssynchrony and correlated it with clinical outcomes in heart failure patients with reduced ejection fraction receiving cardiac resynchronization therapy (CRT). METHODS: Sixty-six advanced heart failure patients referred for CRT with an LV ejection fraction (EF) of < 35% and QRS ≥ 120 ms were studied. We performed equilibrium radionuclide angiography (ERNA) before and 6 mo after CRT. We assessed ventricular dyssynchrony with parameters derived from the first harmonic phase (Ø) analysis of the ERNA time-activity curve and evaluated change in these parameters after 6 mo of CRT. These parameters include novel indices of synchrony (S), a measure of intraventricular contraction order, and entropy (E), a measure of intraventricular contraction disorder, and interventricular synchrony (IVS), a measure of synchronous biventricular function. RESULTS: Forty-seven (71%) patients improved clinically (responders) at 6 mo after CRT whereas 19 (28.8%) showed no change in New York Heart Association class or worsened (nonresponders). The post-CRT changes in QRS duration (P = 0.006), echocardiographic (P = 0.03) and ERNA LVEF (P = 0.0007), LVS (P = 0.004), LVE (P = 0.006), LV standard deviation of ventricular phase (LVSDØ) (P = 0.004), and IVS (P = 0.05) were significantly different between responders and nonresponders. Sixty-two percent of responders had either an LVS < 0.84 or an IVS ≥ 18.8° as opposed to only 16% of nonresponders (P = 0.001). Twenty-nine of 32 (91%) patients with either of these measures responded to CRT (P < 0.01). CONCLUSION: LVS and IVS are novel measures of LV dyssynchrony derived from ERNA planar analysis. A baseline value of LVS < 0.84 or IVS ≥ 18.8° predicts a positive response to CRT.