Assessment of “microvascular no-reflow phenomenon” using technetium-99m macroaggregated albumin scintigraphy in patients with acute myocardial infarction

Objectives. The aim of this study was the scintigraphic evaluation of clinical no-reflow phenomenon. Background. In patients with acute myocardial infarction, the relationship of the severity of reduction of microvascular reflow to the ischemi time or to the secondary extension of myocardial necrosis is poorly understood, and we accordingly conducted scintigraphic evaluation of clinical no-reflow phenomenon. Methods. The group studied consisted of 25 consecutive patients with their first acute myocardial infarction. After recanalization, each patient received intracoronary injections of technetium-99m macroaggregated albumin (MAA). Results. Eight patients (32%) had absent tracer uptake (scintigraphic no-reflow phenomenon). Fourteen patients showed absent or moderately reduced MA uptake (group 1) and 11 showed slightly reduced or normal uptake (group 2). The time to recanalization was significantly longer in group 1 than in group 2 (290.4 ± 130.6 min vs. 177.3 ± 93.5 min; p = 0.0238). In chronic phase, the thallium-201 (Tl-201) defect score index was significantly larger (p < 0.01) and regional ejection fraction was significantly lower (p < 0.01) in group 1 compared with corresponding values in group 2. No significant deterioration from acute phase to chronic phase in either Tl-201 defect score index or regional ejection fraction was found in either group (two-way repeated measures analysis of variance). Conclusions. These findings suggest that scintigraphic no-reflow phenomenon occurs in subgroup of patients without angiographic no-reflow phenomenon, that the myocardial damage depends on the severity of microvascular damage and that prolonged ischemi time may increase the likelihood of “microvascular no-reflow phenomenon.”