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Perfusion Impairment in Patients with Normal-appearing Coronary Arteries: Identification with Contrast-enhanced MR Imaging¹

¹ From the Cardiovascular Magnetic Resonance Laboratory Heart Institute (L.F.R.d.A., J.L.F., C.E.R., J.P.F.) and Institute of Radiology (G.G.C.), University of São Paulo Medical School, Coord Diagnostico por Imagem, Av Dr Enéas de Carvalho Aguiar 44, São Paulo, SP 05403-000, Brazil. Received December 3, 2004; revision requested December 15; revision received February 18, 2005; accepted March 15; final version accepted, June 28. Address correspondence to J.L.F. (e-mail: jlaraf{at}terra.com.br).

Purpose: To prospectively determine the feasibility of using first-pass magnetic resonance (MR) imaging to distinguish between myocardial segments in patients with coronary artery disease (CAD) of different degrees of obstruction and those in patients with normal-appearing coronary arteries.

Materials and Methods: The study was approved by the institutional ethics committee, and all patients provided informed consent. First-pass contrast material–enhanced MR imaging was performed at rest and after the infusion of dipyridamole in 37 patients (29 men, eight women; mean age, 57.2 years ± 10.5 [standard deviation]) who had positive exercise test results or a clinical history of CAD. Myocardial segments were divided into five groups according to the degree of obstruction in the supplying artery. Signal intensity upslope, peak signal intensity, and time to peak signal intensity, as well as hyperemia-to-rest (HR) ratios for each of these three variables, were analyzed for each segment by using a generalized linear model.

Results: Signal intensity upslope in patients with normal coronary arteries at angiography was significantly higher than that in patients with CAD (P < .001). Signal intensity upslope for segments in patients without CAD was significantly different from that for normal-appearing segments in patients with CAD (P < .001). Signal intensity upslope (P < .05) and peak signal intensity (P < .01) enabled the differentiation of segments with more than 70% reduction in luminal diameter from those in all other groups. HR ratios demonstrated findings that were similar to those obtained by using each signal intensity variable alone.

Conclusion: First-pass MR imaging can be used to distinguish segments with different degrees of obstructive CAD. Importantly, MR imaging can help identify segments with impaired perfusion and normal-appearing coronary arteries in patients with CAD and can demonstrate obstructive lesions in other territories.

© RSNA, 2005