RESUMO
OBJECTIVE: To determine the influence of body posture and central hemodynamics on the plasma levels of immunoreactive atrial natriuretic peptide (irANP) during exercise in cardiac transplant patients. METHODS: Central hemodynamics, mixed expired gas and ventilatory measurements, and venous blood sampling (for irANP determination) were obtained in cardiac transplant patients at rest and during supine (n = 12) or upright (n = 12) graded cycle exercise. Cardiopulmonary and irANP responses to exercise were compared between the upright and supine postures. RESULTS: At rest (supine), irANP concentrations were similar in both groups (172 +/- 87 pg/mL supine and 182 +/- 72 pg/mL upright) and did not correlate with resting supine central hemodynamics. During exercise, central filling pressures increased in both groups but patients exercising in the supine position had a greater increase. Peak exercise right atrial pressure was 12 +/- 4 mmHg supine versus 7 +/- 5 mmHg upright (P < 0.005). Peak exercise pulmonary capillary wedge pressure was 22 +/- 6 mmHg supine versus 14 +/- 5 mmHg upright (P < 0.005). At peak exercise, irANP levels were greater in the supine than upright position (419 +/- 166 pg/mL supine versus 277 +/- 40 pg/mL upright, P < 0.05). The change in irANP from rest to peak exercise correlated (P < 0.05) with changes in pulmonary capillary wedge pressure (r = 0.67), systolic pulmonary artery pressure (r = 0.78) and right atrial pressure (r = 0.53). There was, however, no correlation between change in irANP and peak oxygen consumption, change in heart rate or change in mean arterial blood pressure. CONCLUSIONS: In cardiac transplant recipients, exercise is a stimulus for ANP secretion, and augmentation in plasma irANP levels during exercise is modulated by changes in central hemodynamics.
