Objectives The purpose of this study was to evaluate whether plasma aldosterone (ALD) is extracted or produced through the heart in patients with acute myocardial infarction (AMI) and to determine the relationship between transcardiac extraction of plasma ALD and left ventricular (LV) remodeling. Background Although we demonstrated that circulating ALD was extracted through the failing heart and that transcardiac extraction of ALD correlated with LV end-diastolic volume index (LVEDVI) in patients with congestive heart failure, the existence and increase of ALD synthase in the hearts of infarct rats were reported, suggesting cardiac: production of ALD in patients with AMI. Methods We measured plasma ALD in the aortic root (Ao) and coronary sinus (CS) in 57 consecutive patients who received successful revascularization and enalapril, with first AMI at acute phase and after one month. We also measured plasma procollagen type III aminoterminal peptide (PIIINP) in the CS. Results Plasma ALD was significantly lower in the CS than it was in the Ac, at the acute phase (84.7 +/-6.3 pg/ml vs. 105.5 +/-8.0 pg/ml, p<0.0001). Significant positive correlations exist between the transcardiac gradient of ALD at the acute phase and the LVEDVI at one month. Moreover, the transcardiac gradient of plasma ALD at the acute phase has a significant correlation with plasma PIIINP, a biochemical marker of fibrosis, after one month. Stepwise multivariate analysis showed that transcardiac extraction of plasma ALD at the acute phase had an independent and significant positive relationship with a large LVEDVI after one month. Conclusions These results indicate that plasma ALD is extracted through the heart in patients with AMI at the acute phase and that the extracted ALD plays an important role in modulating post-infarct LV remodeling. (J Am Coll Cardiol 2001;38:1375-82) (C) 2001 by the American College of Cardiology.