EXCESSIVE ANAEROBIC METABOLISM DURING EXERCISE AFTER REPAIR OF AORTICCOARCTATION

Objectives: To determine whether survivors of surgery for coarctation of the aorta (CoA) have an excessive reliance on anaerobic metabolism during exercise.Background: Patients with peripheral vascular disease cannot increase blood Row to their muscles normally during exercise. C onsequently they acquire an early, excessive reliance on anaerobic met abolism and have depression of the ventilatory anaerobic threshold (VA T) and of the slope of the oxygen consumption-work rate relationship ( Delta V-O2/Delta WR). We speculated that the capacity to augment blood flow to the lower extremities during exercise may be impaired after C oA surgery and would result in similar metabolic disturbances. Study d esign: Progressive exercise tests were performed on 15 patients (ages 19 +/- 7 years; range, 10 to 32) after successful repair of CoA (resid ual resting gradient, 7.7 +/- 7.1 mm Hg; range, 0 to 18), 15 age-and s ex-matched healthy control subjects, and 10 patients (ages 13 +/- 3 ye ars; range, 10 to 20) who had undergone Ligation of a patent ductus ar teriosus. Results: The CoA patients' VAT averaged 14.8 +/- 3.8 ml O-2/ kg per minute versus 19.3 +/- 3.1 ml O-2/kg per minute for the control subjects (p < 0.01), and their Delta V-O2/Delta WR averaged 8.2 +/- 1 .8 ml/watt compared with 10.1 +/- 1.4 ml/watt for control subjects (p < 0.01). Furthermore, 10 of 15 CoA patients had a VAT of less than 40% of predicted maximal oxygen consumption, and 9 of 15 had a Delta V-O2 /Delta WR of less than 8.7 mi O-2/watt (generally, accepted abnormal v alues). Patients with patent ductus arteriosus resembled the healthy c ontrol subjects with regard to anaerobic metabolism during exercise. C onclusions: Patients who have had CoA repairs commonly manifest an exc essive reliance on anaerobic metabolism during exercise. This phenomen on may result from persistent blood flow abnormalities across the aort ic arch during exercise, which maybe present even after apparently suc cessful surgery.