The feasibility of SPECT CZT measurement of myocardial blood flow and reserve in patients with acute coronary syndrome: comparison with cardiac magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: None. Background. Myocardial infarction with non-obstructive coronary arteries (MINOCA) is currently of interest in terms of diagnostic and treatment strategy. The diagnosis of MINOCA has been included in the STEMI guidelines of the European Society of Cardiology. However, there is lack of data regarding the relationship between myocardial damage according to cardiac magnetic resonance (CMR) and myocardial blood flow (MBF), myocardial flow reserve (MFR) obtained by dynamic SPECT. Purpose. To elucidate impairment of myocardial perfusion, MBF and MFR in patients with MINOCA. Methods. The study included 31 patients (21 men, age 62(56;70) years) with ASC. According to electrocardiography, cardiac biomarkers, invasive coronary angiography two groups were identified: with non-obstructive coronary arteries MINOCA (n = 10); MICAD (n = 21). Within 7-14 days after admission to the hospital all patients underwent dynamic SPECT on CZT gamma-camera with the assessment of standard indices of myocardial perfusion (SSS, SRS, SDS) and quantitative parameters (stress/rest myocardial blood flow (s/r MBF), myocardial flow reserve (MFR)). All patients underwent CMR with late gadolinium enhancement as well. Infarct size (IS), microvascular obstruction (MVO) and myocardial edema size (ME) were evaluated. Results. SSS and SRS differed significantly (p < 0.05) in MINOCA and MICAD patients: MINOCA: SSS 5.0(3.0;5.0), SRS 2.0(1.0;3.0); MICAD: SSS 9.0(5.0;13.0), SRS 6.0(3.0;11.0). However, SDS did not differ significantly in these two groups 2.5(1.0;4.0) vs 4.0(2.0;5.0). Moreover MINOCA patients in comparison with those with MIACD had higher values of quantitative parameters (p < 0.05): sMBF 2.02 (1.71;2.37) vs 0.86 (0.72;1.02) ml/min/g, rMBF 0.68 (0.66;0.86) vs 0.49 (0.4;0.57) ml/min/g, MFR 2.61 (2.23;3.14) vs 1.67 (1.1;1.9), respectively. Based on CMR, a total of 93 left ventricular vessel territories were analyzed. A total of 36(39%) vessel territories were considered as having acute myocardial injury (5 in MICAD, 31 in MINOCA). In patients with MICAD the values of IS, ME were significantly higher as compared to those with MINOCA (IS: 19.4(10.4;29.7)% vs1.8(0.0;6.9)%, ME: 19.5(12.0;30.0)% vs 3.0(0.0;12.0)% - p < 0.01). Based on regional analysis sMBF and MFR were significantly lower in vessel territories considering as CMR positive compared to those without MR signs of myocardial injury: regional sMBF 0.98(0.73;1.79) vs 1.33(0.94;2.08); regional MFR 0.58(0.43;0.9) vs 0.71(0.57;0.88), respectively. Conclusion. SPECT CZT is feasible in identifying both global and regional disturbances of myocardial blood flow and reserve in patients with acute coronary syndrome. MINOCA patients are characterized by mild reduction of myocardial blood flow and perfusion assessed visually and quantitatively. Therefore despite the absence of obstructive coronary artery lesion this group of patients has more pronounced risk of cardiac events and need more aggressive observation and treatment.