TIn depth histologic study was performed on 23 patients who died during the acute phase or within the first three months following acute myocardial infarction. Six died suddenly and unexpectedly out of the hospital, five of these with the acute myocardial infarction unrecognized.The remainder were hospital deaths, five within the first 48 hours, 8 between 2-14 days, and 4 between 14 and 94 days. Five cases showed subendocardial infarction (SI). Four of these occuring out of hospital. The remaining 18 cases were transmural infarctions (TI). Sixteen of 17 hospital deaths exhibited TI.Special emphasis was given to a histologic search for coronary artery thrombosis, particularly nonocclusive thrombosis (NT), and fibrin fragments in the microcirculation. An acute coronary thrombus (ACT) was found in 22 of 23 (96%) cases. The ACT was totally occlusive in 12 of 23 (52%), and NT in 17 of 23 (74%). TI was associated with an acute occlusive thrombus (OT) in 11 of 18 (61%) , and with NT in 12 (67%). All five cases with SI had a NT. Seven (30%) exhibited both an OT and NT located in different coronary arteries. Six of these had TI.Fibrin fragments were located in the microcirculation of the myocardium in 15 of 23 (65%). These were associated with the fresh OT in 8 of 15 (53%) and with a NT in 12 of 15 (80%).Conclude:
1. NT is more common than OT in deaths associated with acute myocardial ’infarction
2. Fibrin fragments are present in the majority of patients with ACT, particularly NT.
3. SI was consistently asscoiated with NT.
4. OT and NT are frequently present in different arteries in the same heart.
5. NT are common in patients with TI.