Surveillance cardiopulmonary exercise testing can risk-stratify childhood cancer survivors: who are at risk for long-term cardiovascular complications and why?

Abstract

Background. Asymptomatic childhood cancer survivors (CCS) frequently show decreased exercise performance. Poor exercise performance may indicate impaired future cardiovascular health. Methods. Cardiopulmonary exercise testing (CPET) was performed in asymptomatic off-treatment CCS (age ≥10 years). Those excluded were children with body mass index (BMI) ≥ 30. Patients were divided into Good and Poor performance groups by their peak oxygen consumption (pVO2*) at 35 and 25 ml/kg/min in males and females, respectively. * denotes weight-indexed values. Results. Thirty-eight males (19 Good, 19 Poor) and 41 females (25 Good, 16 Poor) were studied. Total anthracycline dosage was comparable among 4 groups. The BMI, although normal, was significantly higher in Poor groups. Peak work rate (pWR*), pVO2*, peak oxygen pulse (pOP*), and ventilatory anaerobic threshold (VAT*) were significantly lower, whereas heart rate (HR) increase by WR* (DHR/DWR*) and peak respiratory exchange ratio (pRER) was significantly higher in Poor groups. Simultaneously plotting of weight & pVO2 and DHR/DWR* & pOP* revealed a distinct difference between the Good and Poor groups in both sexes, suggesting decreased skeletal muscle mass and decreased stroke volume reserve, respectively, in Poor CCS. Decreased endurance at peak exercise was noted in Poor groups by simultaneously plotting DVO2*/DHR and pOP*. Ventilatory efficiency was mildly diminished in the Poor groups. Conclusions. Decreased stroke volume reserve, decreased skeletal muscle mass, impaired muscle energy metabolism, decreased ventilatory efficiency, and increased BMI characterized Poor CCS in both sexes. This unique combined CPET analysis provides useful clinical biomarkers to screen subclinical cardiovascular abnormality in CCS.