Infants with critical aortic stenosis may have global or regional left ventricular contraction abnormalities. In order to evaluate the clinical significance of these contraction abnormalities, we examined the systolic left ventricular function before and after aortic valvotomy in 16 infants operated on between 1980 and 1987. Left ventricular free wall and septal motion were studied by cross sectional echocardiography using the apical 4-chamber view. Enddiastolic and endsystolic left ventricular frames were digitized. The relative systolic reduction of the total left ventricular area (reflecting ejection fraction) as well as of 5 left ventricular sectors (reflecting regional wall motion) was calculated and compared to previously established normal values. Before valvotomy, 8 infants had normal and the other 8 impaired left ventricular systolic wall motion. These latter infants showed hypokinesia of the apex and/or the posterolateral left ventricular wall resulting in a decreased systolic reduction of the total left ventricular area. Four of these infants had evidence of myocardial infarction on intraoperative inspection. Early after operation, the systolic reduction of the total left ventricular area was normal in all infants, and the left ventricular apex and poster-lateral wall were either normo- or hyperkinetic. Follow-up studies of all infants more than 10 months and of 7 infants more than 3 years after operation showed that the left ventricular systolic wall motion remained normal in all, irrespective of whether it was normal or abnormal preoperatively. This study suggests that left ventricular contraction abnormalities in infants with critical aortic stenosis may be reversible and thus do not constitute a contraindication against aortic valvotomy.(ABSTRACT TRUNCATED AT 250 WORDS)