Peak Oxygen Uptake Correlates With Survival Without Clinical Deterioration in Ambulatory Children With Dilated Cardiomyopathy

Abstract

Background— Children stable at home with dilated cardiomyopathy remain at risk of death; there is evidence of survival benefit for transplantation out to 4 years postoperatively. The limited supply of donor organs makes risk stratification imperative, but although cardiopulmonary exercise test is well established as a powerful tool in adults with heart failure, no published studies have linked oxygen uptake to prognosis in children. Methods and Results— Between 2001 and 2009, using cardiopulmonary exercise test and echocardiography, we studied 82 children (mean age, 13.5±2.3 years) with dilated cardiomyopathy. All were ambulatory, outpatients, and >120 cm in height. All children completed a symptom-limited maximal exercise test. Resting left ventricular shortening fraction was 20±9%; peak heart rate was 87±13% of predicted; peak oxygen uptake (V̇ o 2 ) was 67±22% of predicted; and ventilatory efficiency was 32±8. Follow-up was available for 100% of the children, and was a mean of 32.3±7.5 months. Eighteen patients reached the defined clinical end point of death or listing for urgent heart transplantation. On univariate analysis, left ventricular shortening fraction, peak heart rate, peak V̇ o 2 , peak systolic blood pressure, and ventilatory efficiency were all associated with adverse outcome. On multivariable Cox analysis, only peak V̇ o 2 ( P =0.003) was associated with the study end point. Patients with a peak V̇ o 2 ≤62% of predicted had a higher 24-month event rate (50.6% versus 4.4%; hazard ratio, 10.78). Conclusions— We have demonstrated that a cardiopulmonary exercise test is feasible in ambulatory children with dilated cardiomyopathy who are >120 cm height and for the first time have linked peak V̇ o 2 with outcome in children.