Cardiorespiratory Response to Exercise after the Fontan Procedure for Tricuspid Atresia

Abstract

Noninvasive exercise testing was used to assess gas exchange in 13 patients age 6-25 yr who had undergone Fontan procedures for tricuspid atresia, five of whom had preexisting Glenn shunts. The results were compared to 28 age- and sex-matched controls. Oxygen saturation was measured by ear oximetry at rest and after exercise. Ventilation, oxygen consumption (VO2), carbon dioxide production (VCO2), and heart rate were measured during progressive exercise. The ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2), mixed expired pCO2 (PECO2) end-tidal pCO2 (PETCO2), and dead space to tidal volume ratio (VD/VT) were determined during steady state exercise on a cycle ergometer. Heart rate was higher for VO2 by 15% (p less than 0.02) and ventilation was higher for both VO2 (by 37%, p less than 0.001) and VCO2 (by 27%, p less than 0.002) in the patients than the controls. Mean VE/VO2 was 35.4 +/- 7.8 (SD) compared to 25.8 +/- 3.1 (p less than 0.001) and mean VE/VCO2 was 41.7 +/- 9.0 compared to 31.6 +/- 4.3 (p less than 0.001). Mean PECO2 was 21.4 +/- 4.4 torr with controls at 27.9 +/- 3.8 (p less than 0.001) and mean PETCO2 was 33.0 +/- 5.3 torr compared to 40.0 +/- 3.3 (p less than 0.001). The patients had a mean oxygen saturation of 92 +/- 5% at rest and abnormal saturation after exercise (87 +/- 9, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise capacity and impact of exercise training in patients after a Fontan procedure: A review

“…The authors also observed reduced skeletal muscle endurance in a group of seven Fontan patients compared with healthy individuals (15). Some skeletal muscle (75) No change in cardiac output at exercise Grant et al (37) Lower maximal heart rate Brassard et al (15) (75) Higher submaximal heart rate Grant et al (37) Lower arterial blood saturation maximum Brassard et al (15) (75) Lower cardiac output at exercise Durongpisitkul et al (39) alterations encountered in CHF patients, like muscle atrophy and weakness, morphological changes and/or altered metabolic capacity, may explain these results. The authors also observed a significant relationship between skeletal muscle strength and exercise tolerance, suggesting that the skeletal muscle function may be a limiting factor of exercise tolerance in these patients (15).…”

“…This is demonstrated by an elevated ventilatory equivalent for oxygen at rest and at (41) No change in submaximal heart rate Driscoll et al (41) Higher or no change in blood Driscoll et al (10) (10) ventilation maximal exercise (14). Following the surgical procedure, the ventilatory equivalent for oxygen may be corrected at rest but stays slightly elevated at maximal exercise (15,37). This is the consequence of an increased physiological dead space to tidal volume ratio resulting from ventilation or perfusion mismatch and a persistent right-to-left shunt, hypoxic stimulation of ventilation and/or the need to maintain acid-base homeostasis by eliminating carbon dioxide from a reduced blood volume (10,14,39,41).…”

“…This is the consequence of an increased physiological dead space to tidal volume ratio resulting from ventilation or perfusion mismatch and a persistent right-to-left shunt, hypoxic stimulation of ventilation and/or the need to maintain acid-base homeostasis by eliminating carbon dioxide from a reduced blood volume (10,14,39,41). Furthermore, a significant increment of the ventilatory equivalent for carbon dioxide has also been reported (15,37,(42)(43)(44), suggesting excessive ventilation in patients after a Fontan procedure compared with healthy individuals. These abnormalities may be secondary to the increased physiological dead space to tidal volume ratio or a lower chemoreceptors threshold for arterial carbon dioxide partial pressure (42).…”

“…This reduction may be the consequence of an intrapulmonary right-to-left shunt that may become more important over time following the procedure, coronary sinus blood return to the pulmonary venous atrium, an intracardiac rightto-left shunt, a significant physiological dead space and/or a ventilation/perfusion mismatch with an abnormal pulmonary blood flow distribution (10,14,17,37,47). The lower arterial blood saturation may also be the result of a flow increment in the lungs' superior lobes with increased pulmonary vascular resistance (47).…”

Exercise Testing and Training in Children With Congenital Heart Disease

“…52,53 Once again, this observation is probably due, to a large extent, to pulmonary blood flow maldistribution (and associated V/Q mismatch) secondary to the absence of a pulmonary ventricle. 54 In Fontan patients, however, the degree of V E/V CO 2 slope elevation is not strongly associated with increased mortality because, in contrast to the aforementioned conditions, the elevated slope is intrinsic to the patients' single ventricle physiology and not closely related to the progression/severity of the underlying cardiovascular disease process.…”