Background: An analysis of the US National Cardiovascular Data Registry has revealed that only 38% of patients referred for coronary angiography after non-invasive coronary testing have relevant coronary obstruction (CO) (≥70%) of one or more coronary arteries.Methods: A single-center trial was undertaken in 165 consecutive, symptomatic patients with either known or suspected coronary disease and/or valve disease(VHD) who agreed to undergo cardiac catheterization and coronary angiography if stress myocardial perfusion imaging was abnormal. A total of 116 patients with abnormal SPECT MPI tests, persistent chest pain, or significant VHD underwent final analysis. An MCG coronary obstruction (CO) score of ≥ 4.0 was considered indicative of relevant CO (≥70%) in one or more coronary arteries. Angiographic results were finalized by consensus of two angiographers.Results: CO (≥70%) was present in 53 of 116 patients (46%). The MCG CO score was significantly higher for patients with relevant CO (5.4 ± 1.9 vs. 2.5 ± 1.9). The MCG correctly classified 103 of the 116 patients (89%) enrolled in the study as either having or not having CO (≥70%) (sensitivity- 91%; specificity- 87%; NPV- 92%; PPV- 86%). SPECT MPI was abnormal in 99 of the 116 (85%) patients undergoing catheterization, but correctly classified only 54 of the 116 patients (47%) entered in the study as either having or not having relevant CO (sensitivity-85%; specificity-14%; NPV - 53%; PPV- 45%).Conclusions: The MCG was shown in this paired-comparison trial with SPECT MPI to safely and accurately identify patients with relevant CO (≥70%) prior to catheterization.

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