Congenital Heart Disease
Results of the Bruce Treadmill Test in Children After Arterial Switch Operation for Simple Transposition of the Great Arteries

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Abstract

Children who underwent arterial switch operation for simple transposition of the great arteries in the neonatal period are now reaching an age when exercise testing becomes feasible. This study was conducted to assess exercise tolerance and electrocardiographic response to exercise stress in 50 asymptomatic children, aged 4 to 9 years, using the Bruce walking treadmill protocol to voluntary exhaustion. Heart rate and blood pressure response to exercise stress, endurance time, and electrocardiographic changes were analyzed and compared with those of age-matched normal children. Forty-seven patients had normal exercise capacity and parameters. One patient, whose coronary angiogram showed occlusion of the left main coronary artery, developed electrocardiographic signs of myocardial ischemia during exercise. In 1 patient with a single right coronary artery ostium and in another, who underwent a neonatal internal mammary bypass graft for obstruction of the right coronary artery, the resting electrocardiogram showed ventricular premature complexes and exercise stress-induced salvos of ventricular tachycardia. We conclude that most of the children who underwent the neonatal arterial switch operation for simple transposition of the great arteries have a normal exercise capacity. Exercise testing appears to be useful in detecting ischemic damage or exercise-induced arrhythmias possibly secondary to reduced coronary flow reserve.

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Patients:

Eligibility criteria for participation in this study included (1) an arterial switch operation in our institution during the neonatal period, (2) age >48 months, (3) no physical limitations (New York Heart Association functional class 1), no symptoms and no cardioactive medications, (4) no prior experience with the treadmill and no opportunity for practice. Fifty patients, aged 4 to 9 years (mean ± SD 5.6 ± 1.5), participated in the study. There were 40 boys and 10 girls. All children were

Results

Forty-seven patients had a normal exercise capacity and normal cardiovascular parameters. The maximal heart rate at peak exercise was 186.9 ± 10.2 beats/min, but >180 beats/min in all cases. Endurance time was >90th percentile in 7 patients, between the 75th and the 90th percentile in 11, between the 50th and the 75th percentile in 14, between the 25th and the 50th percentile in 7, between the 10th and the 25th percentile in 7, and <10th percentile in 1. This last child did not produce a near

Discussion

The mobilization and translocation of the coronary arteries remains the most technically challenging aspect of the arterial switch operation; it carries the combined risk of primary ischemic injury and late problems with coronary artery kinking, stenosis, or occlusion.

Several investigators described late coronary occlusion or stenosis.2, 3, 5, 6, 7, 8Their incidence was 3% of the 366 patients whose cineangiograms had been reviewed by Tanel et al[9]and 7.8% of the 64 patients of Bonnet et al[8]

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