Purpose: Dispersion in the contraction of the normally coordinate ventricular system, referred to as left ventricular (LV) dyssynchrony, is constantly observed at different grades of severity after myocardial infarction (MI). We aimed to investigate the prognostic value of early dyssynchrony in adverse cardiac events after MI in a rat model using the quantified gated single photon emission tomography (SPECT; QGS) software.
Procedures: After thoracotomy, the left coronary arteries of 16 rats were occluded and reperfused. SPECT was performed with [99m Tc]methoxyisobutylisonitrile 3 days, 1 week, 2 weeks, 4 weeks, and 8 weeks after MI. The phase analysis parameters including mean phase standard deviation (PSD), bandwidth (BW), entropy, and LV function were analyzed by the QGS software. A receiver operating characteristic curve was used to explore the predictors for cardiac death and severe cardiac failure (ejection fraction [EF] < 35 %). A Kaplan-Meier event-free survival analysis, univariate, and multivariate Cox proportional hazards regression analyses were conducted.
Results: Four rats had died, whereas another four rats presented with severe heart failure. LV end-diastolic volume was increased during follow-up, but no significant changes were noted in the other parameters. The prognosis of rats with lower EF and higher end-diastolic and end-systolic volumes (ESV), PSD, BW, and entropy at 3 days after MI was poor. Adverse cardiac events were associated with lower EF (relative risk [RR] 13.1, 95 % confidence Interval [CI]: 2.1-259.9, P = 0.003), higher ESV (RR 6.4, CI 1.4-45.9, P = 0.01), and higher entropy (RR 4.3, 95 % CI: 1.0-21.8, P = 0.04) by univariate analysis. Multivariate analysis showed that lower EF was the most powerful independent predictor of adverse cardiac events (RR 16.0, CI 1.1-429.2, P = 0.03).
Conclusions: Severe early dyssynchrony evaluated by QGS after MI could predict cardiac events in the rat model in the same way as other cardiac function parameters including EF and ESV. The early assessment of dyssynchrony after MI may provide helpful information for the prediction of cardiac events in the future.
Keywords: Acute myocardial infarction; Dyssynchrony; Phase analysis.