Atrial natriuretic peptide (ANP) levels reflect circulating blood volume and atrial pressure. To assess the correlation between plasma ANP levels and systolic pulmonary arterial pressure (PAP) in maintenance hemodialysis (HD) patients, we examined 23 patients immediately before and after HD. Plasma ANP concentrations were measured by a specific and sensitive radioimmunoassay. Tricuspid reguritation was recorded by contrast Doppler echocardiography. PAP was computed by a modification of the Bernoulli formula as the sum of the transtricuspid gradient and right atrial pressure (PAP=4V²+10mmHg, where V is the maximal velocity of the tricuspid regurgitant jet, and 10mmHg is average right atrial pressure).
The mean plasma ANP level after HD was markedly lower than before HD (before: 265±185pg/ml, after: 64±85pg/ml, p<0.0001). The mean PAP level was also reduced by HD (before: 35.3±10.1mmHg, after: 25.7±7.1mmHg). There was a significant correlation between plasma ANP and PAP levels (before HD: r=0.67, p<0.001, after HD: r=0.43, p<0.05). There was also a significant correlation between the change in plasma ANP level and the change in PAP by HD (r=0.67, p<0.001). The two of the 23 patients who had a history of pulmonary edema within the previous 6 months showed PAP values over 40mmHg after HD.
In conclusion, plasma ANP concentrations reflect PAP, and measurement of PAP by contrast echocardiography seems to be a safe and useful method of estimating the ideal weight of HD patients.