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 (V[Combining Dot Above]O2) 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 V[Combining Dot Above]O2, peak systolic blood pressure, and ventilatory efficiency were all associated with adverse outcome. On multivariable Cox analysis, only peak V[Combining Dot Above]O2 (P=0.003) was associated with the study end point. Patients with a peak V[Combining Dot Above]O2 ≤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 V[Combining Dot Above]O2 with outcome in children. © 2011 American Heart Association, Inc.