Fetal cardiac hypertrophy and cardiac function in diabetic pregnancies

Our purpose was to evaluate the relationship between fetal cardiac wall hypertrophy and ventricular function in fetuses of metabolically controlled, insulin-requiring diabetics.

M-mode directed fetal echocardiography included measurements of left and right ventricular free wall and interventricular septal thickness and ventricular diastolic and systolic dimensions. Fetal measurements included biparietal diameter, estimation of fetal weight, and cardiac area/thoracic area. Cardiac size is expressed as a ratio of wall thickness/biparietal diameter, and function is expressed as ventricular shortening fraction (Ventricular diastolic dimension-Ventricular systolic dimension/Ventricular diastolic dimension). Fetuses of diabetics at 20 to 24, 28 to 31, and 32 to 36 weeks' gestation were compared with normal fetuses of nondiabetic mothers at similar gestational ages, which were used as a control group.

Study and control groups were comparable in mean gestational age (22 vs 20, 29 vs 29, 35 vs 34 weeks) in each of groups 1, 2, and 3. All fetuses tested fell within these groups. Estimated fetal weight, cardiac area/thoracic area, right ventricular wall thickness/biparietal diameter, and interventricular septal thickness/biparietal diameter were greater in the study group between 32 and 36 weeks: 3227 +/- 430 versus 2235 +/- 176 gm (p < 0.05), 0.32 versus 0.29, (p < 0.05), 0.53 +/- 0.05 versus 0.44 +/- 0.05 mm (p < 0.05), and 0.50 +/- 0.3 versus 0.46 +/- 0.5 mm (p < 0.05), respectively. Right ventricular shortening fraction/left ventricular shortening fraction was significantly different from controls in this group (1.30 vs 0.89, p < 0.05). This change was a function of altered right ventricular shortening fraction in late diabetic pregnancy. Right ventricular shortening fraction in the study groups was 0.39, 0.36, and 0.52, respectively, versus 0.36, 0.41, and 0.33 in controls. Left ventricular shortening fraction in the group at 32 to 36 weeks and in controls in three groups was 0.42, 0.39, 0.40 and 0.44, 0.37.

These findings reveal an increase in right ventricular shortening fraction associated with global cardiac enlargement. Myocardial hypertrophy involving right ventricular wall thickness and interventricular septal thickness in metabolically stable insulin-requiring diabetics revealed hypercontractility of the right ventricle.