Cardiac size and performance during pregnancy estimated with echocardiography

Abstract

Echocardiography was performed In 55 women In the following groups: Group I, 15 normal nonpregnant control subjects; Group II, 13 normal women In the 13th to 23rd weeks of gestation; Group III, 15 normal women In the 24th to 32nd weeks of gestation; and Group IV, 12 women at term pregnancy. The heart rate was 20 percent greater In pregnant women than In normal control subjects, and left ventricular dimensions and volumes were significantly larger during gestation. The right ventricular dimension was significantly increased in women in Group III ( P < 0.001). Stroke volume increased by 32 percent in the 13th to 23rd weeks (Group II, P < 0.005) and remained Increased later (Group III). There was a parallel rise in ejection fraction. Cardiac output, 3.93 ± 0.53 (mean ± 1 standard deviation) liters/ min in normal nonpregnant women, increased to 6.05 ± 1.58 in the second trimester ( P < 0.001) and to 6.15 ± 1.5 liters/min later in gestation ( P < 0.001). When women at term pregnancy were studied in the left lateral position they had a higher cardiac output (5.88 ± 1.69 liters/min) ( P < 3.001) than normal control subjects (Group I), but when they were studied supine their cardiac output was almost as low as that in Group I although they had a higher heart rate. The velocity of circumferential shortening and posterior wall slope both increased to a significant extent in all pregnant women. In Group III, the velocity of circumferential shortening increased to 1.35 ± 0.19 circumferences/sec compared with 1.13 ± 0.12 circumferences/sec in control subjects ( P < 0.005), and the slope of posterior wall motion increased to 61.1 ± 8.7 mm/sec compared with 50.5 ± 4.9 in control subjects. Cardiac output increased early in pregnancy because of an increase in both stroke volume and heart rate. Enhanced myocardial contractility may have contributed to the observed increase.