Contraction-relaxation coupling and impaired left ventricular performance in coronary surgery patients

Background Dependence of left ventricular (LV) relaxation on cardiac systol ic load is a function of myocardial contractility. The authors hypothesized that, if a tight coupling would exist between LV contraction and relaxatio n, the changes in relaxation rate with an increase in cardiac systolic load would be related to the changes in LV contraction. Methods: Coronary surgery patients (n= 120) with preoperative ejection frac tion > 40% were included, High-fidelity LV pressure tracings (n = 120) and transgastric transesophageal echocardiographic data (n = 40) were obtained. Hearts were paced at a fixed rate of 90 beats/min. Effects on contraction were evaluated by analysis of changes in dP/dt(max) and stroke area. Effect s on relaxation were assessed by analysis of R (slope of the relation betwe en tau and end-systolic pressure). Correlations were calculated with linear regression analysis using Pearson's coefficient r, Results: Baseline LV end-diastolic pressure was 10 +/- 3 mmHg (mean +/- SD) , During leg raising, systolic LV pressure increased from 93 +/- 9 to 107 /- 11 mmHg. The change in dP/dt(max) was variable and ranged from -181 to 254 mmHg/s. A similar variability was observed with the changes in stroke a rea, which ranged from -2.0 to +5.5 cm(2). Changes in dP/dt(max) and in str oke area were closely related to individual R values (r = 0.87, P < 0.001; and r = 0.81, P < 0.001, respectively) and to corresponding changes in LV e nd-diastolic pressure (r = 0.81, P < 0.001; and r = 0.74, P < 0.001, respec tively). Conclusions: A tight coupling was observed between contraction and relaxati on, Leg raising identified patients who developed a load-dependent impairme nt of LV performance and increased load dependence of LV relaxation.