Navigating dynamic stress CT perfusion in the presence of myocardial fibrosis: a CMR-guided interpretation

Abstract Introduction Dynamic stress CT perfusion (dynCTP) offers a 'one-stop' assessment of CAD's anatomy and function. However, myocardial fibrosis, common in atherosclerotic patients, often mimics inducible ischemia, leading to false-positive dynCTP results. Crucially, such patients, despite fibrosis's significant prognostic role in ischemic heart disease, are largely excluded from dynCTP validation studies. Objectives 1.- Evaluate the concordance between regadenoson-stress dynCTP and 3-T cardiac magnetic resonance (CMR) perfusion in symptomatic patients, including those with and without prior myocardial infarction. 2. Determine if a normal dynCTP result can reliably exclude focal myocardial fibrosis as defined by late gadolinium enhancement (LGE) CMR. Methods A prospective, single-center study enrolled symptomatic patients with suspected or known CAD who underwent regadenoson-stress dynamic dual-source CT and 3.0-T stress CMR. Myocardial blood flow (MBF) from CT was quantified using a 100 mL/100g/min cut-off for dichotomization. CT-derived MBF concordance with CMR findings (qualitative perfusion defects and LGE) was assessed. Mean time between CT and CMR examinations was 68 ± 30 days. Results Forty-two patients (age: 68 ± 11 years; 78% male) were included. Baseline characteristics: hypertension (76%), dyslipidemia (71%), smoking (48%), diabetes (31%), and prior CAD (31%). Mean radiation exposure for the CT protocol was 5.74 ± 3.2 mSv. Six hundred seventy-two myocardial segments were evaluated using both dynCTP and stress CMR. Overall ischemic/non-ischemic concordance was 78% (524/672). This rose to 81% (479/588) in non-LGE segments but fell to 58% (45/84) in LGE segments. Segment-level CT-MBF diagnostic performance for detecting perfusion defects yielded: in non-LGE CMR segments, sensitivity, specificity, PPV, and NPV were 65%, 87%, 60%, and 89%, respectively. For LGE segments, these values were 69%, 48%, 54%, and 64% Only 4.7% (26/558) of segments deemed non-ischemic by both techniques displayed LGE on CMR, a majority of which showed