Page 29 - Clinical Pearls in Cardiology

History and General Examination 17

volume). A decompensated heart cannot increase its force
of contraction in accordance with the Frank–Starling law.
A decreased sympathetic drive during sleep may also
contribute to the reduced force of cardiac contraction.
Hence there is pooling of blood in the cardiopulmonary
system. This leads to pulmonary venous hypertension
and produces pulmonary edema resulting in PND.
27. What is differential cyanosis and what is its significance?
Differential cyanosis means that the fingers are pink but
the toes are cyanotic (and usually clubbed). It signifies
the presence of a patent ductus arteriosus (PDA) with
a right-to-left shunt due to pulmonary hypertension
(i.e. Eisenmenger’s syndrome). If the ductus joins the
descending aorta before the origin of the left subclavian
artery, then the left hand may also be cyanotic (Fig. 4).

Fig. 4: Mechanism of differential cyanosis