[Cardiac output evaluation during exercise in children treated with atrial surgery for transposition of great...

The long-term physiopathological consequences of atrial surgery (Senning or Mustard procedures) for transposition of the great vessels with respect to exercise capacity are not well known. We measured the cardiac index by the technique of CO2 rebreathing at two submaximal levels of exercise corresponding to a stable oxygen consumption of 20 (E20) and 30 (E30) ml/min/kg in 7 patients successfully operated for transposition of the great vessels and in 7 control children paired for age, gender and body surface area. Despite an identical chronotropic response to exercise in the two groups, the increase in cardiac index was not as great in the children operated for transposition (from 6.86 +/- 0.51 to 7.71 +/- 0.78 l/min/m2) as in the control population (from 7.71 +/- 0.78 to 10.2 +/- 0.51 l/min/m2; p < 0.02). The stroke volume index was therefore significantly lower in the transposition group at both levels of exercise (52 +/- 3.2 vs 63 +/- 4.1 ml/m2; p < 0.04 at E20; and 46.4 +/- 4.3 vs 66 +/- 5.1 ml/m2 at E30). The main cause of this reduction of the stroke volume index is probably a lack of adaptation of right ventricular systolic function on exercise but it is not possible to exclude diastolic dysfunction due to reduce compliance secondary to the intraatrial patch. The conditions of preload are in fact instrumental in increasing stroke volume index at submaximal exercise levels.