M-mode echocardiographic evaluation of fetal and infant hearts: Longitudinal follow-up study from intrauterine life to year one

OBJECTIVE: Our purpose was to evaluate cardiac variables, including right and left end-diastolic and end-systolic dimensions by use of M-mode echocardiography during fetal, neonatal (transitional),and infancy periods to understand hemodynamic adaptation during these periods. STUDY DESIGN: Fifty-three fetuses were enrolled in this study. Echocardiography evaluations were started as early as the sixteenth week of gestation and were repeated every 4 to 6 weeks until term, on postnatal days 1 and 2, and at 6 weeks, 6 months, and 12 months of age. End-diastolic and end-systolic measurements were made according to published standards. Mean and SEM for each of the end-diastolic and end-systolic measurements were calculated for each of 11 study periods. Data were analyzed by one-way analysis of variance, corrected for repeated measures, and in the case of right and left ventricular differences paired t tests were used for significance. RESULTS: Left ventricular end-diastolic and end-systolic correlated positively with advancing age (R(2) = 0.93, p < 0.0001), right ventricular end-diastolic also correlated with advancing age (R(2) = 0.361, p < 0.05), and right ventricular end-diastolic was significantly larger than left ventricular end-diastolic in utero (p < 0.01), whereas the opposite was true after birth (p < 0.0001). Heart rate significantly decreased with advancing age (p < 0.001), whereas ejection fraction for either the right or the left ventricle did not change significantly with advancing age. CONCLUSION: This suggests that under basal conditions the ventricles can meet the increased demands in cardiac output by increasing ventricular dimensions without having to increase contractility reserve.