Atypical patent ductus arteriosus. The use of vasopressor agent as a diagnostic aid. Circulation 19: 332

Approximately 95 per cent of patients with patent ductus have characteristic maehinery imiurmiiurs. Five per cent have only systolic murmurs. In such patients, the intravenous or intramuscular administration of a pressor substance, mephentermine, may bring out a continuous murmur. This simple test is a useful adjunct in diagnosis. IN OUR EXPERIENCE about 95 per cent of patent ducti have the typical machinery murmur, and present no problem in diagnosis. A continuous murmur maximal in the second to third left intercostal space usually means patent ductus arteriosus. Other sites usually indicate other lesions. The typical machinery murmur reflects a systolic and diastolic pres-sure gradient between the aorta and pulmo-nary artery with left-to-right shunt in both systole and diastole. The intensity of the murmur may or may not parallel the size of the ductus and the degree of shunt. It is the atypical 5 per cent of ducti that cause difficulty in diagnosis. The diagnosis of atypical patent ductus can be most re-warding, as a seemingly hopeless and confus-ing situation may be resolved safely and defi-nitely at the operating table. In atypical patent ductus there may be no murmur, a pulmonic systolic flow murmur, or a late sys-tolic-early diastolic murmur overriding the pulmonic second sound having either a late systolic or early diastolic accentuation.1 2 OC-casionally the murmur of pulmonary insuf-ficiency appears with severe pulmonary hyper-tension. Atypical murmurs occur chiefly in infaney3 or when secondary pulmonary hyper-tension develops. When atypical murmurs are present, there are several possibilities. The ductus may be extremely small or quite large. In infants and small children with low systemic blood pressures and relatively high pressures in the pulmonary artery4 ' 5 the systolic-diastoli