Adaptive mechanisms of left ventricular diastolic function to the physiologic load of pregnancy

Background Pregnancy is associated with marked alteration in cardiovascular hemodynamics. Recent reports have characterized the effects on cardiac systolic function. Little has been written on the influences of loading conditions on Doppler measures of diastolic function during pregnancy. Hypothesis: Stage of pregnancy has an impact on Doppler indices of diastolic function independent of loading conditions, systolic function, and heart rate. Method: Thirty healthy women were prospectively evaluated by serial echocardiography and Doppler examinations at six time periods: 10-12, 18-20, 28-30, 36-38 weeks gestation, 2-4 and 12-14 weeks postpartum. The related effects on indices of diastolic function and its interaction with load, heart rate, mass, and systolic function were determined. Results: Compared with the nonpregnant state, early (E) velocity increased (0.7 +/- 0.1-0.9 +/- 0.1 m/s, p = 0.0001), peaking at 18 weeks and returning to normal levels during late pregnancy. Atrial phase (A) velocity peaked at 18 weeks (0.48 +/- 0.12-0.60 +/- 0.13 m/s, p = 0.0001), remaining high throughout the rest of pregnancy. Consequently, the E/A ratio fell significantly during late pregnancy, from 1.9 +/- 0.4 to 1.4 +/- 0.3 (p = 0.02). In addition, mean acceleration was significantly increased in early pregnancy with a peak at 18 weeks (7.4 +/- 1.3 m/s(2)), returning to nonpregnant level at term (5.7 +/- 1.4 m/s(2), p = 0.0001). Generalized estimating equation using multivariate regression analysis demonstrated that rising heart rate and stroke volume index had an independent effect on A velocity, and that contractility and preload had an independent effect on E velocity. Pregnancy itself had an independent influence on early filling, not explained by the other parameters. Conclusions: During normal pregnancy, there is a reversible shift in transmitral flow velocities from early to late filling with a decrease in acceleration, consistent with an increase in ventricular compliance. Changes in heart rate, preload, and contractility, as well as stage of pregnancy influence this alteration.