Excitation-Contraction Coupling Time is More Sensitive in Evaluating Cardiac Systolic Function

Background： Pressure overload-induced myocardial hypertrophy is a key step leading to heart failure. Previous cellular and animal studies demonstrated that deteriorated excitation-contraction coupling occurs as early as the compensated stage of hypertrophy before the global decrease in left ventricular ejection fraction （LVEF）. This study was to evaluate the cardiac electromechanical coupling time in evaluating cardiac systolic function in the early stage of heart failure. Methods： Twenty-six patients with Stage B heart failure （SBHF） and 31 healthy controls （CONs） were enrolled in this study. M-mode echocardiography was performed to measure LVEF. Tissue Doppler imaging （TDI） combined with electrocardiography （ECG） was used to measure cardiac electromechanical coupling time. Results： There was no significant difference in LVEF between SBHF patients and CONs （64.23 ± 8.91% vs. 64.52 ± 5.90%; P= 0.886）. However, all four electromechanical coupling time courses （Qsb： onset of Q wave on ECG to beginning of S wave on TDI, Qst： onset of Q wave on ECG to top of S wave on TDI, Rsb： top of R wave on ECG to beginning orS wave on TDI, and Rst： top of R wave on ECG to top orS wave on TDI） of SBHF patients were significantly longer than those of CONs （Qsb： 119.19 ± 35.68 ms vs. 80.30 ± 14.81 ms, P 〈 0.001 ; Qst： 165.42 ± 60.93 ms vs. 129.04 ± 16.97 ms, P = 0.006; Rsb： 82.43 ± 33.66 ms vs. 48.30 ± 15.18 ms, P 〈 0.001; and Rst： 122.37 ± 36.66 ins vs. 93.25 ± 16.72 ms, P = 0.001 ）, and the Qsb, Rsb, and Rst time showed a significantly higher sensitivity than LVEF （Rst： P =0.032; Rsb： P = 0.003; and Qsb： P = 0.004）. Conclusions： The cardiac electromechanical coupling time is more sensitive than LVEF in evaluating cardiac systolic function.