Correlation of Myocardial Perfusion on Cardiac Magnetic Resonance Versus Myocardial Perfusion Scintigraphy in Cardiac Syndrome X

Background: In cardiac syndrome X, which is a syndrome defined as chest pain, positive exercise stress testing and/or reversible myocardial perfusion defects during myocardial scintigraphy and normal coronary angiograms, the ischemic origin is still debated. No previous study compared the myocardial perfusion in stress first-pass cardiac magnetic resonance (CMR) versus stress single-photon emission computed tomography (SPECT) in cardiac syndrome X. Methods: We performed stress SPECT and CMR imaging for 20 syndrome X patients. Perfusion analysis of the CMR was done by using the normalized upslope of myocardial signal enhancement to derive the myocardial perfusion index (MPI) and the myocardial perfusion reserve index (MPRI). The SPECT images were visually scored by 3 observers using a seg- mental model. Results: An MPRI of  1.2 was found for 31 (9%) of the 335 segments, indicating local ischemia. SPECT indicated re- versible perfusion defects for 39 (12%) of the 335 segments. However, the combination of both an MPRI  1.2 and a re- versible perfusion defect was detected in only 3 segments. Conclusions: Our data show about 10% stress-induced myocardial perfusion abnormalities on CMR and SPECT, suggest- ing local ischemia. However, only in 1% of the segments there was concordance for the presence of myocardial ischemia with both exams. This result may be evidence for the variability over time of the mechanisms responsible for coronary microvascular dysfunction.