Evaluation of transient heart murmur resembling pulmonary artery stenosis in term infants by Doppler and M-mode echocardiography.

Four term infants with transient murmurs resembling that of pulmonary artery stenosis were examined. A grade 3/6 systolic ejection murmur was transmitted clearly to the entire precordium and the back. This murmur was first detected 7 days after birth in 1 infant and at a 1-month medical check in the other 3. The murmur continued for 7 to 22 weeks, with an average of 12 weeks. It gradually localized in the region of the left sternal border, and eventually disappeared. At the first medical examination, peak velocities of over 2.0 m/s, in the left or right pulmonary artery, were detected by a pulsed Doppler. The diameter of the right pulmonary artery was small (mean, 58 +/- 8%; range, 46 to 64% of predicted normal). When the heart murmur disappeared, the diameter of the right pulmonary artery (mean, 97 +/- 28%; range, 70 to 126%) had increased significantly (p < 0.05). Peak velocities in the right pulmonary arteries had decreased significantly (2.22 +/- 0.37 m/s vs 1.13 +/- 0.10 m/s, p < 0.01). We suggest that hypoplasia of pulmonary artery branches, in relation to the main trunk, is the main cause of the murmur resembling pulmonary artery stenosis.