A12-year-old boy is diagnosed with congenital coarctation (constriction) of the aorta. A posterior-to-anterior chest film reveals a characteristic notch in the aortic knob in the superior aspect of the left border of the cardiovascular shadow. This points to a constriction just past the origin of the left subclavian artery. Radiographic examination also reveals characteristic notching of the lower border of the upper ribs, most pronounced along the posterior segments. You perform simultaneous examination of the radial and posterior tibial pulses on the 12-year-old boy. What is the expected relationship of the posterior tibial pulse to the radial pulse?
(A) It is delayed and of greater volume than the radial pulse.
(B) It is delayed and of lesser volume than the radial pulse.
© It is in sequence with and equal in volume with the radial pulse.
(D) It is in sequence with, but of greater volume than, the radial pulse.
(E) It is in sequence with, but of lesser volume than, the radial pulse.
Explanation:
(B) In congenital coarctation of the aorta, the thoracic aorta is usually obstructed just past the origin of the left subclavian artery. If the constriction reduces the diameter of the aorta by more than 50%, then the patient develops symptoms such as decreased tolerance to exercise and greater fatigability. Because the radial artery arises from branches proximal to the coarctation and the posterior tibial artery from branches distal to the coarctation, simultaneous palpation of their pulses typically reveals posterior tibial pulses to be delayed and of lesser volume than the radial pulses. Choices A, C, D, and E are all incorrect.