COMPARISON OF CARDIOPULMONARY ADAPTATION DURING EXERCISE IN CHILDREN AFTER THE ATRIOPULMONARY AND TOTAL CAVOPULMONARY CONNECTION FONTAN PROCEDURES

Background There are several potential physiological differences betwe en the atriopulmonary (AP) and the total cavopulmonary connection (TCP C) Fontan circulations. Studies suggest that the TCPC reduces energy l oss due to turbulence and may have more dependence on respiratory move ment for pulmonary blood flow. We compared cardiopulmonary physiology during rest and exercise in patients who had undergone the AP Fontan p rocedure with those who had undergone the TCPC Fontan procedure. Metho ds and Results Forty-three children were studied more than 6 months af ter undergoing a Fontan procedure (23 AP and 20 TCPC); 106 healthy chi ldren were also studied as a control group. Measurements of effective pulmonary blood flow, stroke volume, arteriovenous oxygen difference, minute ventilation, heart rate, and oxygen and carbon dioxide consumpt ion were made with an Innovision quadrupole mass spectrometer. Data fr om the control group allowed calculation of z scores for the Fontan gr oups matched for age, sex, pubertal stage, and body surface area. Maxi mal exercise performance was equal in the two Fontan groups, but it wa s below normal. However, adaptation to exercise was different in the F ontan groups. After 9 minutes of exercise, pulmonary blood flow rose l ess in the AP group than in the TCPC group (P<.01), and the stroke vol ume in the AP group also tended to be lower (P=.057) and their arterio venous oxygen difference was significantly greater (P<.01). Although m inute ventilation per unit of carbon dioxide production was similar in the Fontan groups at this level of exercise, children in the TCPC gro up breathed faster by approximately 10 breaths per minute (P<.005). Co nclusions At submaximal exercise, children who had undergone the TCPC Fontan procedure had pulmonary hemodynamics superior to those of child ren who had undergone the AP procedure, largely because of respiratory adaptation that permitted blood to be ''sucked'' into the lungs. To a chieve the same maximal exercise performance, children who had undergo ne the AP procedure had a superior metabolic adaptation to exercise st ress.