Ischemic right ventricular dysfunction was diagnosed in 54 patients with acute myocardial infarction who had a right atrial pressure disproportionately increased in relation to the pulmonary capillary pressure. The right atrial pressure curve in 40 patients (74 percent) was M- or W-shaped, termed a noncompliant pattern, and was similar to the pattern found in constrictive pericarditis. Kussmaul's sign was found in the patients whose respiration was recorded. This pattern, which represents poor right ventricular compliance, was severe in 30 cases (y descent greater than x descent) and slight in 10 cases (y descent = x descent). Its duration was variable, ranging from days to years. Of the 54 patients, 32 (59 percent) had a low output syndrome, diagnosed in the presence of a cardiac index of less than 2.2 liters/min per m2, with signs of poor tissue perfusion. The severe noncompliant pattern was significantly related to the presence of a low output syndrome (p less than 0.01) and mortality from this cause (p less than 0.05). The jugular venous tracing pulse had a pattern similar to that of the right atrial pressure recording and therefore may be valuable in the noninvasive diagnosis of right ventricular dysfunction and in the study of the evolution of the noncompliant pattern and, hence, of ventricular compliance.