Multidirectional M-mode echocardiography (echo) was used to investigate functional and structural changes of the heart in 68 consecutive patients with acute or subacute infectious myocarditis. Forty patients had mild myocardial involvement evident by gradually changing ST-segment or T-wave alterations (not responsive to beta blockade) in serial ECGs; 21 patients also had loud S3 gallop and palpable paradoxical cardiac pulsations, and 7 patients had severe congestive heart failure. Echo revealed regional changes in the left ventricular (LV) contraction in all patients with acute myocarditis. The site and size of the asynergic wall motion abnormalities correlated with both the clinical severity of the disease and the location of the T-wave inversions in the ECG. In mild myocarditis hypokinesia only was noted in 1 to 3 sites (mean 2.3) of 11 recorded LV sites (21%). In moderate myocarditis, the local asynergic change was mainly akinesia and more widespread, being surrounded by hypokinetic regions (3.8 of 11 sites, 35% of the LV sites). In congestive heart failure, the hypokinetic or akinetic segments affected almost the entire left ventricle (7.6 of 11 sites, 69% of the LV sites) (p less than 0.001 between the groups). In the last group, all patients had strong "fibrotic" echoes, in contrast to mild myocarditis (13%). In mild infectious myocarditis the contraction disturbance of the asynergic regions also generated a peculiar "quivering" pattern with thin echo lines. In the uninvolved segments, hyperkinesia was observed in most patients. The LV end-diastolic diameters in the 3 groups were 51 +/- 5, 58 +/- 4 and 65 +/- 5 mm (p less than 0.05), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)