The nature and clinical features of myocardial infarction with normal coronary arteriogram.

Six new cases of acute myocardial infarction with normal coronary arteriogram are presented and supplemented by 19 collected cases (group I). These are compared with 16 cases of myocardial infarction caused by occlusive coronary artery disease in a comparable population (group ii). The following significant differences between the two groups are established: patients in group I were younger (27.5 years vs 33.7 years, P less than 0.005); at least one risk factor was present in all patients in group II, but in only 40% of group I (P less than 0.0001). effort angina preceded the attack in ten patients of group II, but in none of group I (P less than 0.0001). The attack was unheralded in 24 of the 25 patients in group I, but was preceded by prodromes in 11 of 16 in group II (P less than 0.0001). Attacks of pain following myocardial infarction occurred in five patients of group 2 and II of group II) (P less than 0.001). Results are discussed in the light of the nature of myocardial infarction in group I. No support is found for the coronary spasm theory. The most likely mechanism for development of myocardial infarction in group I is thought to be a thromboembolic "accident." This accident is not necessarily related to atherosclerotic coronary disease and is presumed to be benign in nature.