Where the Evidence Runs Out: Ten Open Questions in Myocardial Perfusion Scintigraphy and Stress Perfusion Cardiovascular Magnetic Resonance

Guidelines list stress perfusion cardiovascular magnetic resonance (CMR) and myocardial perfusion scintigraphy (MPS) side by side for chronic coronary syndromes, with the same class of recommendation; in practice, availability decides. The comparative literature is less settled than that parity suggests. In CE-MARC, CMR reached an area under the curve of 0.89 against 0.74 for single-photon emission computed tomography (SPECT); a same-patient meta-analysis against invasive angiography gives sensitivity of 72% against 63% and specificity of 77% against 78%, with heterogeneity above 90%; when tested by randomisation in CE-MARC 2, unnecessary angiography occurred in 7.5% of CMR-guided and 7.1% of MPS-guided patients. This narrative review examines ten open questions: whether absolute flow quantification is ready to guide decisions when positron emission tomography supplies validated thresholds, whether ischaemia without obstructive disease is an imaging or an invasive diagnosis, whether viability testing still changes management after STICH and REVIVED-BCIS2, and whether cost-effectiveness estimates computed under assumed availability apply where 56% of Eastern European respondents report no formal CMR training. For each, we set out the competing positions and the study that could resolve it, identify areas of consensus, propose a framework for modality selection, and outline the head-to-head comparison the field still lacks.