Non-dominant right coronary artery (RCA) is associated with suspected inferior ischemia on SPECT in patients without significant coronary artery disease (CAD).

OBJECTIVE: There is a huge uncertainty in the medical community regarding the significance of non-dominant right coronary artery (RCA) in patients with inferior wall ischemia on myocardial perfusion single-photon emission computed tomography (SPECT). The purpose of this study is to determine the effect of non-dominant RCA on myocardial perfusion SPECT (MPS) with respect to the misleading detection of ischemia in the inferior wall of the myocardium. METHODS: This is a retrospective study of 155 patients, who had undergone elective coronary angiography owing to an indication of inferior wall ischemia by MPS between 2012 and 2017. Patients were divided into two groups based on the coronary dominance: group 1 (n = 107), if RCA is the dominant artery, and group 2 (n = 48), if there are dominance of left artery and codominance of both arteries. Obstructive CAD was diagnosed in the case of stenosis that had severity greater than 50%. The positive predictive value (PPV), which was calculated as per the correlation between the inferior wall ischemia in MPS and obstruction level in RCA, was compared in both groups. RESULTS: Majority of patients were male (109, 70%) and the mean age was 59.5 ± 10.2. There were 45 patients with obstructive RCA disease (PPV: 42%) among 107 patients in group 1, whereas there were only 8 patients with obstructive coronary artery disease (CAD) in RCA among 48 patients in group 2, (PPV: 16% and p = 0.004). CONCLUSIONS: The results demonstrated that non-dominant RCA is associated with false-positive detection of inferior wall ischemia via MPS.