Prevalence and Significance of Spontaneous Thrombolysis in Transmural Myocardial Infarction

To define the prevalence and significance of spontaneous thrombolysis, we studied 36 patients during early transmural myocardial infarction and later after recovery from the acute event. Of the 36 patients studied, 29 demonstrated persistent coronary occlusion. Of these 29 patients, 17 demonstrated persistent occlusion on repeat coronary arteriography and left ventriculography. Twelve of the patients were found to have undergone spontaneous reperfusion. Within the persistent occlusion group there was little improvement in regional function, while the spontaneous reperfusion group frequently demonstrated significant improvement in regional function. This occurred whether the infarction was anterior or inferior. Despite the improvement in regional function, both the persistent occlusion group and spontaneous reperfusion patients demonstrated inconsistent regional performance {i.e., some patients improved despite persistent occlusion while some did not despite demonstrating spontaneous reperfusion). Importantly, even though spontaneous reperfusion was associated with improvement in global and regional function, the measurements at restudy did not yield values that were consistently a major improvement over the persistent occlusion group. This may have occurred because of the relatively small numbers in the study and because the spontaneous reperfusion group frequently demonstrated myocardial infarction (MI) measurements that were more depressed than those of the persistent occlusion group. We conclude that spontaneous recanalisation occurs in approximately 40 per cent of patients who demonstrate total coronary occlusion during the early hours of acute transmural myocardial infarction and that some contractile deficit persists even when spontaneous recanalisation is achieved.