Atypical Patent Ductus Arteriosus

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 pressure gradient between the aorta and pulmonary 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 rewarding, as a seemingly hopeless and confusing situation may be resolved safely and definitely at the operating table. In atypical patent ductus there may be no murmur, a pulmonic systolic flow murmur, or a late systolic-early diastolic murmur overriding the pulmonic second sound having either a late systolic or early diastolic accentuation.1 2 OCcasionally the murmur of pulmonary insufficiency appears with severe pulmonary hypertension. Atypical murmurs occur chiefly in infaney3 or when secondary pulmonary hypertension 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-diastolic