The natural history of contraction abnormalities and their response after acute
myocardial infarction in man were studied using
radionuclide angiography. Sixteen patients were studied before and after sublingual
nitroglycerin within 24 hours, 5-7 days and 4-6 weeks after the onset of
chest pain. Within 24 hours, central chord shortening in the zone of
infarction was reduced to 13.1 +/- 9.8%, but improved 27.2 +/- 18.4% (p less than 0.001) after
nitroglycerin. After 5-7 days, central chord shortening improved similarly, but less markedly, from 12.9 +/- 9.2% to 24.4 +/- 13.2% (p less than 0.001). After
nitroglycerin 4--6 weeks after the acute
myocardial infarction, the central chord showed no response to
nitroglycerin; it was 13.9 +/- 10.9% before and 13.4 +/- 2.5% after
nitroglycerin. Changes in the lateral chords paralleled changes in the central chords in the three studies. Nonischemic zone improvement after
nitroglycerin in all three studies. Global ejection fraction improved and end-diastolic and end-systolic volumes decreased in all three studies after
nitroglycerin. These data indicate that after acute
myocardial infarction, there is a significant reduction in hemiaxis shortening in the central and lateral chords that remains essentially unchanged over 4-6 weeks. However, the asynergic ischemic area improves considerably after
nitroglycerin within 24 hours and 5-7 days, but fails to improve after 6 weeks.