Right heart and pulmonary artery pressures were measured in 28 patients with inferior acute myocardial infarction, 12 of whom also had ECG evidence of right ventricular involvement (RVI). Those with RVI had significantly higher mean right-sided filling pressures 9.3 mm Hg, SD +/- 4.5 than those without RVI, 4.3 mm Hg, SD +/- 1.9. A steeper relationship between right ventricular enddiastolic and mean pulmonary artery pressures was seen in patients with RVI in contrast to those without, where no marked rise in right-sided filling pressures with increasing mean pulmonary artery pressures was seen.