Differentials
Venous hum
SIGNS / SYMPTOMS
A venous hum can be heard usually more on the right side. In addition, it diminishes with supine positioning and with local compression.
INVESTIGATIONS
Physical examination will distinguish a venous hum as described previously. If there is still sufficient concern, echo can be performed. In the case of a venous hum, the echo will be normal.
Coronary artery fistula
SIGNS / SYMPTOMS
This murmur is also continuous. However, it is usually heard lower in the precordium.[2]
INVESTIGATIONS
Can be distinguished by echo. On echo evaluation, a coronary fistula will appear as a small continuous jet of flow into the right ventricle or main pulmonary artery. It can be distinguished by location.
Left-sided shunts (ventricular septal defect, atrioventricular septal defect)
SIGNS / SYMPTOMS
These lesions can present similarly with regard to clinical history, ECG, and chest x-ray findings. However, the murmur of most left-to-right shunts will only be heard in systole. The exception is an aortopulmonary window, which is a large connection between aorta and pulmonary artery, and will present with clinical findings identical to that of a large patent ductus arteriosus.
INVESTIGATIONS
Echo can definitively distinguish these lesions by their characteristic appearance and location. Left heart enlargement, if present, will look similar in all these lesions.
Aortic regurgitation
SIGNS / SYMPTOMS
These patients often present at an older age. They can also present with symptoms of exercise intolerance. They usually do not demonstrate tachypnoea. The murmur is characteristically a high-pitched diastolic decrescendo murmur best heard at the lower left sternal border.
INVESTIGATIONS
Echo can definitively distinguish aortic regurgitation from a patent ductus arteriosus. On echo, the descending aorta may similarly demonstrate diastolic flow reversal depending on the degree of aortic regurgitation. However, a diastolic regurgitant jet will be seen at the level of the aortic valve.
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