[Effect of collateral circulation on myocardial protection in patients with acute myocardial infarction: comparison of technetium-99m-tetrofosmin myocardial single photon emission computed tomography and coronary angiography]

Abstract

Objectives: Evaluation of myocardial blood flow from collateral vessels into the infarct area has been estimated by coronary angiography. In patients with acute myocardial infarction with Thrombolysis in Myocardial Infarction (TIMI) 0 flow, myocardial tracer uptake on single photon emission computed tomography (SPECT) images can predict the collateral blood flow in the infarct area if technetium (Tc)-99m-tetrofosmin was administered before recanalization. The present study investigated whether collateral blood flow evaluated by myocardial scintigraphy is a good predictor of myocardial salvage in patients with acute myocardial infarction.

Methods: The study group consisted of 30 patients (mean age 65 +/- 14 years, 23 males, 7 females) with first acute myocardial infarction and coronary angiography evidence of total occlusion (TIMI 0) within 12 hr after the onset. All patients had one vessel disease related to infarction and TIMI 3 flow after percutaneous coronary intervention (PCI). Tc-99m-tetrofosmin was injected intravenously before the PCI. The regional severity score index (RSSI) was obtained from SPECT using the 17 segment method with the four-point scoring system. Myocardial viability was evaluated by the RSSI obtained from thallium-glucose-insulin infusion SPECT after 1 week and regional wall motion score index obtained from echocardiography during the chronic phase.

Results: The patients were divided into two groups according to the angiographic collateral finding. There were no differences in RSSI on thallium-glucose-insulin SPECT and regional wall motion score between the good collateral group (n = 8) and poor collateral group (n = 22). Myocardial Tc-99m-tetrofosmin RSSI was similar in these groups. On the other hand, the patients were divided according to Tc-99m-tetrofosmin scintigraphic evaluation before PCI. RSSI on thallium-glucose-insulin SPECT was significantly greater (0.7 +/- 0.5 vs 1.5 +/- 0.4, p < 0.01) and regional wall motion score was significantly less (1.46 +/- 0.50 vs 2.08 +/- 0.78, p < 0.05) in the lower Tc-99m-tetrofosmin RSSI (< 1.9) group (n = 22) compared with the higher RSSI (> or = 1.9) group (n = 8). In addition, a significant correlation was obtained between Tc-99 m-tetrofosmin RSSI and regional wall motion score index (r = 0.53, p < 0.01).

Conclusions: The collateral flow evaluated by scintigraphy was significantly correlated with myocardial viability.