Cardiovascular responses to dynamic submaximal exercise in children previously treated with anthracycline

This study assessed the long-term (5-year) outcome of pediatric low-dose anthracycline therapy on the circulatory response to moderate exercise. Thirteen patients (13 +/- 4 years old) and 15 age-matched control subjects completed a maximal cycle ergometer protocol as well as two 5-minute cycling tests at 33% and 66% maximal oxygen uptake (V(O2)max) for determination of cardiac index (carbon dioxide rebreathing). V(O2)max was lower in patients than in control subjects (1.3 +/- 0.5 L/min vs 2.3 +/- 0.6 L/min) (p< 0.05). Smaller relative increases in cardiac index for similar increases in relative exercise intensities were found in patients (33% V(O2)max, 73% vs 116%; 66% V(O2)max, 115% vs 192%), as a result of smaller increases in stroke index from rest (33% V(O2)max, 33% vs 54%; 66% V(O2)max, 33% vs 69%; p< 0.05). Similarly, despite normal resting systolic function, patients exhibited a lower stroke index and higher heart rate for any given value of oxygen uptake (milliliters per minute per square meter). Children who had survived cancer exhibited stroke index impairment during exercise similar in intensity to that of recreational activities or play, attesting to a limited inotropic reserve.