Value of 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) gated SPECT for the detection of silent myocardial ischemia in hemodialysis patients:: clinical variables associated with abnormal test results

Background Although coronary artery disease is a major cause of mortality and morbidity in patients undergoing hemodialysis, there is no accurate diagnostic strategy for these patients. Aim To assess the value of Tc-99m-methoxyisobutylisonitrile (Tc-99m-MIBI) gated single-photon emission computed tomography for the detection of silent myocardial ischemia in patients undergoing hemodialysis and to evaluate the clinical variables associated with abnormal test results. Methods Thirty-one asymptomatic patients undergoing hemodialysis (20 men, 11 women), with a mean age of 45 years (range, 25-75 years), were included in the study. Serum electrolytes, creatinine, homocysteine and adhesion molecules were measured prior to dialysis. Ambulatory blood pressure, carotid intima-media thickness measurements, echocardiography and stress Tc-99m-MIBI imaging were performed in all patients, whereas coronary angiography was performed only in patients with abnormal myocardial perfusion scintigraphy and/or echocardiography. Results Gated myocardial perfusion scintigraphy results were abnormal in nine patients (29%) and coronary angiography was abnormal in six patients. After a median follow-up of 20 months (range, 14-28 months), nine patients experienced a cardiac event. Seven of the nine patients (78%) with abnormal myocardial perfusion scintigraphy suffered a cardiac event, compared with only two of 22 patients (9%) with normal myocardial perfusion scintigraphy (P<0.0001). Patients with abnormal perfusion scintigraphy had higher serum C-reactive protein, homocysteine and adhesion molecule levels and the duration of hemodialysis was significantly longer. Conclusion In asymptomatic hemodialysis patients, gated myocardial perfusion scintigraphy is a safe and non-invasive screening technique for the detection of coronary artery disease and for predicting future cardiac events. The presence of ischemia correlates significantly with markers of inflammation. The discordant results (abnormal myocardial perfusion scintigraphy/normal coronary angiography) can be attributed to angiographically unrecognized occult atherosclerotic changes and abnormal vasodilatation capacity of the coronary circulation.