OXYGEN UPTAKE, ARTERIAL BLOOD GASES AND BLOOD LACTATE CONCENTRATION DURING SUBMAXIMAL AND MAXIMAL EXERCISE IN ADULT SUBJECTS WITH SHUNT‐OPERATED TETRALOGY OF FALLOT

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Abstract
Ten female and six male adult subjects with shunt-operated tetralogy of Fallot have been studied at rest and during submaximal and maximal exercise on an average 20 years after the palliative operation. There was a considerable reduction in the aerobic work capacity, maximal oxygen uptake (VO2) being 1.00 1/min STPD. Though ventilation (VE) was out of proportion to VO2 as indicated by an abnormally high ventilation equivalent (52.1), values for VEmax were low (50.81/min BTPS) and of approximately the same order as in a comparable group of totally corrected TOF patients. In spite of increased VE in relation VO2 the PaCO2 increased from 30 mmHg at rest to 49 mmHg during maximal exercise, while PaCO2 decreased from 60 mmHg at rest to 44 mmHg during submaximal exercise I. During heavier exercise no further fall was noted. Base excess decreased from -2.9 to -9.8 mEq/l. Thus a combined respiratory and metabolic acidosis was at hand during exercise, the metabolic component, however, being normal. Maximal blood lactate concentrations were low (5.8 mmol/l) and contrasted with the high intramuscular lactate concentrations earlier reported in some of the patients. The low values found for VO2 max indicate that a palliative operative procedure in TOF is no alternative to an intracardiac repair in the long-term course. The two main factors limiting exercise tolerance were acidosis and accumulation of lactate within the muscle cell.