Plasma levels of atrial natriuretic peptide at rest and during exercise in heart failure--influence of cardiac rhythm and haemodynamics.

The relationship between plasma levels of immunoreactive atrial natriuretic peptide (ir-ANP), arginine vasopressin (AVP), cardiac rhythm and different haemodynamic variables were studied at rest and during exercise in 16 patients with heart failure undergoing heart catheterization for clinically indicated reasons. Even though there was no significant relationship between pulmonary capillary wedge pressure (PCW) and ir-ANP at rest (r = 0.39; P = 0.14) changes in these variables with exercise correlated well (r = 0.71; P = 0.002). Change in right atrial mean pressure, heart rate, mean arterial blood pressure or cardiac index did not significantly influence change in plasma levels of ir-ANP. The correlation between PCW and AVP at rest (r = 0.92; P less than 0.001) disappeared during exercise. Calculated ir-ANP/PCW ratios decreased slightly during exercise, but were not influenced by initial atrial pressures or atrial fibrillation. These observations provide evidence for a similar responsiveness of ANP in patients with sinus rhythm and atrial fibrillation. The ability of rapid change in ANP plasma levels during exercise was preserved and proportional to changes in PCW over a wide pressure range in the studied patient group. This finding indicates that left atrium distension rather than right atrium distension is the major determinant for the release of ANP in patients with congestive heart failure. The observed rapid responsiveness of ANP to change in left atrial pressure may allow the hormone to modulate haemodynamic response during short periods of exercise.