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chronic fatigue, effort intolerance, and a heart murmur. On physical examination, the boy
appeared slightly small for his age, had normal skin color, no clubbing of the fingers, and a
harsh murmur throughout systole that was heard best in the fourth intercostal space to the
left of the sternum but extended over the entire precordium. X-ray revealed an enlarged
heart, especially the right ventricle. An ear oximeter showed normal oxygenation of arterial
blood. Cardiac catheterization data were as follows:
Mean right atrial pressure 5 mm Hg
Right ventricular systolic pressure 30 mm Hg
Right ventricular diastolic pressure 3 mm Hg
Right atrial blood PO2 40 mm Hg
Right ventricular blood PO2 60 mm Hg
7. The patient was admitted to the cardiac surgery unit for repair of
A. Coarctation of the aorta
B. Interventricular septal defect
C. Pulmonic stenosis
D. Tetralogy of Fallot
E. Patent ductus arteriosus

B.

B.

there is a step up in Oxygen saturation in the right ventricle.

The answer is B. The murmur, the high right ventricular systolic pressure with a normal
right atrial pressure, the elevated PO2 of the right ventricular blood, and the absence
of cyanosis indicate a left-to-right shunt through an interventricular septal defect.
Coarctation (stenosis) of the aorta (choice A) would not be indicative of right ventricular
enlargement. Only slight elevation of pulmonary systolic pressure rules out pulmonic
stenosis (choice C), tetralogy of Fallot (choice D), and patent ductus arteriosus
(choice E).