Change in plasma volume during peak exercise in patients with cyanotic congenital heart disease after definitive operation.

OBJECTIVES

To evaluate changes in plasma volume (deltaPV) 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. DeltaPV 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

DeltaPV 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 deltaPV (p<0.05 to 0.005). DeltaPV 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 deltaPV correlated only with the NE increase (p<0.01).

CONCLUSIONS

DeltaPV 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 deltaPV. These mechanisms may help to maintain cardiac output and increased sympathetic nervous activity may be beneficial to ensure sufficient perfusion pressure against deltaPV during exercise.