Exercise Stress Testing in Pediatric Hypertrophic Cardiomyopathy

Cardiopulmonary stress testing in pediatric patients with hypertrophic cardiomyopathy may have clinical benefits.

Certain pediatric patients with hypertrophic cardiomyopathy (HCM) may find clinical benefit in exercise stress testing (EST). These findings were published in the Journal of the American College of Cardiology: Advances.

Researchers aimed to explore the clinical utility of EST in pediatric HCM. The primary composite endpoint included arrhythmia requiring internal cardiac defibrillator placement, transplant, or cardiac death. The researchers used the first outcome for analysis if patients experienced 2 or more outcomes.

They conducted a retrospective single-center analysis of patients younger than 21 years of age with HCM who received EST from January 2000 until January 2019 at the Children’s Hospital of Philadelphia, PA, United States. They included 140 patients (20% girls or women; 70% White) of whom 52% had a recognized genetic variant. Median age at the first EST was 13.6 years and 44% of patients were taking a beta-blocker. The majority of patients (90%) were tested using ramp cycle ergometry and 79.4% had a maximum effort test. Analysis used Cox proportional hazard modeling.

Echocardiographic data for 116 patients revealed median left ventricular ejection fraction (EF) of 68.0% and 1.4 cm for the median maximum septal wall thickness. None of the patients had EF of less than 55%, and more than 28% of patients had a peak left ventricular outflow tract gradient.

EST is a valuable clinical tool to assess exercise capacity in this population.

The median peak power was 2.6 W/kg (SD, 1.1) or 73.7% predicted. The mean anaerobic threshold was 21.8 mL (IQR, 8.3), and the median peak oxygen consumption was 37.1 mL/kg/min (IQR, 12.5) or 81.2% predicted.

Eight percent of patients had an abnormal blood pressure response to exercise and there was ectopy in 44% of patients during EST. Twelve patients reached the primary endpoint and the presence of any ectopy was a predictor of the primary endpoint (hazard ratio, 5.8; 95% CI, 1.3-26.7).

Changes over time measured by additional ESTs showed a significant decrease in percent predicted VO2 and maximum heart rate as age increased (both P <.001) and no significant change in percent predicted power with age.

Significant study limitations include the retrospective design and lack of control group. There is also possible selection bias and the multivariable analysis of risk factors for the primary outcome was not performed due to an underpowered sample size.

“EST is a valuable clinical tool to assess exercise capacity in this population,” the study authors wrote. “These findings suggest that EST is useful in the care of pediatric patient with HCM.”

References:

Edelson JB, Stanley HM, Min J, et al. Cardiopulmonary exercise testing in pediatric patients with hypertrophic cardiomyopathy. JACC Adv. October 2022. doi:10.1016/j.jacadv.2022.100107