The time necessary for aortic diastolic pressure to decrease to 50 percent of an initially selected value after dissipation of the dicrotic notch (T 1 2) was determined in newborn infants with and without pulmonary hypertension. The mean T 1 2 was 671 ± 167 msec in seven infants with clinical evidence of pulmonary hypertension and documented right to left ductus arteriosus shunting; 849 ± 243 msec in nine infants with clinical evidence of pulmonary hypertension but no documented right to left ductus arteriosus shunting; and 457 ± 66 msec in eight infants with hyaline membrane disease and no clinical evidence of pulmonary hypertension or a patent ductus arteriosus. The mean T 1 2 values in the former two groups were significantly different from that in the group with no pulmonary hypertension (P < 0.01). An evaluation of factors affecting T 1 2 leads to the conclusion that the patients with pulmonary hypertension had increased systemic vascular resistance as well. This finding has important diagnostic, etiologic and therapeutic implications.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine