The clinical, angiographic and therapeutic features of eight patients who developed a left ventricular pseudoaneurysm (PA) after an acute myocardial infarction (AMI) and those of 25 who did not develop this complication following a medically managed left ventricular free wall rupture (FWR) were compared. These 25 patients were treated with pericardiocentesis, extended rest and strict blood pressure control. Most patients with FWR or PA had a first AMI and absence of overt heart failure. Both groups had a comparable age, frequency of systemic hypertension and extent of coronary disease. Pericardial effusion (> or =10 mm) was documented in all patients with FWR and in two of the three with PA with this information. Twenty four patients with FWR were hospitalized within the first 48 h (96%) but only three of those with PA (37.5%, P<0.002). Moreover, in patients with PA, a FWR was not suspected during AMI and, as opposed to those with FWR, they did not undergo a strict blood pressure control or a restriction of physical activity following AMI. Also, beta blockers were administered to 15 patients with FWR (60%) but to only one with PA (11%, P<0.02). Our findings suggest that failure to recognise a self limited FWR during AMI and to provide adequate control of blood pressure and physical exercise during the acute phase and the early weeks postinfarction, are likely to favor development of PA.