a u s c u l t a t i o n    t u t o r
Patent Ductus Arteriosis


A patent ductus is an arteriovenous fistula between an arterial circuit of high pressure (aorta) and an
arterial system of lesser pressure (pulmonary artery) (Fig. 8–41C). The continuous murmur results from
blood flowing continuously into the pulmonary artery during the entire heart cycle. The higher pressure
during ventricular systole increases murmur’s pitch. Uncorrected, the increased PA pressure leads to RVH
and eventually right-to-left shunting with peripheral cyanosis confined to the lower extremities
(Eisenmenger physiology). The Murmur A murmur heard in the first and second left interspace continuously
through systole and diastole is usually caused by a patent ductus. The murmur is medium-pitched and
rough, heard with either bell or diaphragm. Louder murmurs are harsh. There is typically a crescendo late
in systole and a decrescendo after S2, producing a machinery murmur (Fig. 8–39F, page 370).Most
frequently, transmission is to the interscapular region; occasionally it is transmitted down the left sternal
border, sometimes to the apex. As pulmonary artery pressures approach aortic pressure, the diastolic
portion of the murmur may disappear. TR may develop from the pulmonary hypertension. Increased flow
through the mitral orifice may produce a diastolic rumble simulating mitral stenosis. Heart Sounds S2 may
be buried in the crescendo portion of the murmur. Frequently there is a short pause between S1 and the
murmur. Palpation The precordial thrust of both ventricles may be accentuated. Arterial Pulses With large
shunts the peripheral pulse may have a collapsing quality, similar to AI. DDX: Clubbing may be present in
the toes but spare the fingers when persistent right to left shunt occurs late. The continuous murmur must
be distinguished from a venous hum.
t h e     h e a r t
Normal Cardiac Cycle
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