SPECT-based evaluation of the relationship between acute change in left ventricular synchrony after cardiac resynchronization therapy and patient outcome

Objectives We used phase analysis of gated single photon emission computed tomography (GSPECT) to determine the relationship between acute change in left ventricular (LV) synchrony after cardiac resynchronization therapy (CRT) and long term outcomes using a novel, single-injection protocol designed to minimize radiation exposure from serial imaging.

Methods In 44 CRT patients, the device was left inactive at implantation. Following a single injection of Tc-99m sestamibi, GSPECT was acquired before and 30 minutes after CRT activation. Left ventricular (LV) dyssynchrony parameters [histogram bandwidth (HBW) and phase standard deviation (PSD)] before and after CRT were compared to determine acute change in LV synchrony. Z scores calculated from prospectively derived repeatability data were used to define significant change in synchrony (z <-1.28 or z >1.28 for either HBW or PSD). Primary outcome was a composite of death, heart failure hospitalizations, defibrillator shocks, and CRT deactivation due to symptoms.

Results 18 (41%) patients had an improvement, 11 (25%) no change, and 15 (34%) had deterioration in LV synchrony acutely after CRT. Over the follow-up of 9.6 ± 7 months, 13 (31%) patients met the endpoint. Patients who had an acute deterioration in synchrony had a significantly higher event rate (57%) than patients who had acute improvement or no change in synchrony (18%). Event free survival was significantly worse in patients who had an acute deterioration in synchrony [Hazard ratio 4.6 (1.3-16.0) p = .003].

Conclusions Phase analysis of SPECT using a single injection of radiotracer can be used to assess changes in LV synchrony after CRT, which is related to patient outcome