['The study evaluated the transcardiac extraction or spillover of aldosterone (ALDO) in normal subjects and in patients with congestive heart failure (CHF).', 'Aldosterone promotes collagen synthesis and structural remodeling of target organs such as the heart. Spironolactone, an ALDO receptor antagonist, has recently been reported to reduce the mortality of patients with CHF; however, the effects of spironolactone on the transcardiac gradient of ALDO have not been clarified.', 'We measured plasma ALDO in the aortic root (AO) and coronary sinus (CS) in normal subjects and 113 consecutive CHF patients and also measured plasma procollagen type III aminoterminal peptide (PIIINP) in CS, a biochemical marker of myocardial fibrosis.', 'Plasma ALDO was significantly lower in the CS than in the AO in normal subjects (n = 15; 61.2 +/- 9.3 vs. 83.1 +/- 11.8 pg/ml, p < 0.0001). In 96 CHF patients who did not receive spironolactone, plasma ALDO was significantly lower in the CS than in the AO (59.3 +/- 3.9 vs. 73.8 +/- 4.9 pg/ml, p < 0.0001). In contrast to the difference in these 96 patients, there was no significant difference in ALDO between the AO and CS in 17 patients who received spironolactone (127.4 +/- 20 vs. 124.0 +/- 19 pg/ml, p = 0.50). Stepwise multivariate analyses showed that spironolactone therapy had an independent and significant negative relationship with the transcardiac gradient of plasma ALDO in patients with CHF. In addition, significant positive correlations were seen between the transcardiac gradient of plasma ALDO and PIIINP (r = 0.565, p < 0.0001) and the left ventricular end-diastolic volume index (r = 0.484, p < 0.0001).'] Does spironolactone inhibit the transcardiac extraction of aldosterone in patients with congestive heart failure?