Objectives: To evaluate changes in plasma volume(Δ PV)during exercise in patients with single ventricular physiology with cyanosis; post-Fontan patients; and in patients after right ventricular outflow tract reconstruction(RVOTR). Background: Compensatory mechanisms which regulate body fluid volumes operate in heart failure patients to maintain blood pressure. A better understanding of this pathophysiological process, especially during exercise, should help manage and follow such patients. Methods: Twenty-six CHD patients(14± 4 years), including 5 cyanotic patients, 12 after the Fontan operation, 9 after RVOTR, and 13 controls(14± 5 years), performed a treadmill exercise test. Δ PV from rest to peak was calculated and compared with changes in cardiovascular responses,plasma total protein(TP), norepinephrine(NE), osmolality(Osm), and blood lactate concentration(La). Results:Δ PV was smaller in CHD patients than in controls(Cyanotic:-5.9% , Fontan:-10.0% , RVOTR: -11.4% , Controls:-14.5% , p< 0.001). In all subjects, peak heart rate, systolic blood pressure and oxygen uptake correlated inversely with Δ PV(p< 0.05 to 0.005). Δ PV correlated inversely with changes in TP, NE, and La(p< 0.005 for all), but not with the change in Osm. In CHD patients, the Δ PV correlated only with the NE increase(p< 0.01). Conclusions: Δ PV is smaller in CHD patients than in controls, especially in cyanotic patients. The smaller increases in cardiovascular responses during exercise and La are associated with the small Δ PV. These mechanisms may help to maintain cardiac output and increased sympathetic nervous activity may be beneficial to ensure sufficient perfusion pressure against Δ PV during exercise.
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