Background-Adult patients with total correction of tetralogy of Fallot
may have poor exercise capacity associated with impaired right heart
function and in particular pulmonary regurgitation. The ventilatory re
sponses to exercise were studied in a group of such patients to assess
relations between ventilation, exercise capacity, and right ventricul
ar function. Methods-30 patients (7 female) (aged 27.8 (6.0) years) an
d 30 (7 female) controls of a similar age range were studied prospecti
vely. All underwent exercise testing with metabolic gas exchange to de
termine peak oxygen consumption (peak VO2), and (as indices of the ven
tilatory response) the slope of the relation between both respiratory
rate (RR) and ventilation (VE) against carbon dioxide production (VCO2
). Patients were studied with pulsed wave Doppler echocardiography to
determine pulmonary arterial systolic and diastolic flow characteristi
cs. Patients were defined as having restrictive right ventricular func
tion where diastolic pulmonary forward flow was seen coincident with a
trial systole. Results-in the group With tetralogy of Fallot mean (SD)
peak VO2 was 35.3 (7.5) ml/kg/min (93.6 (15.3) % of expected for age,
weight, height and sex). The RR/VCO2 slope was steeper in the Fallot
group (6.8 (2.6) v 9.6 (4.7), P < 0.02). Those with restrictive right
ventricles achieved a higher peak Vo, than those without (82.5 (10.1)%
v 100.9 (13.8), P < 0.001). In the Fallot group alone, there was an i
nverse relation between ventilatory response and peak VO2 (RR/VCO2 v p
eak VO2; r = - 0.63, P = 0.003: VE/VCO2 v peak VO2; r = - 0.62, P < 0.
001). Conclusions-Many of these patients with repaired tetralogy of Fa
llot had near normal exercise capacity, but as exercise capacity decre
ased, the ventilatory response to exercise increased. This was not due
to alterations in pulmonary function tests or to the effects of cardi
ac size causing decreased lung volume. It may be that the increased ve
ntilatory rate at a given level of carbon dioxide production acts as a
respiratory pump aiding right ventricular function.