Myocardial Late Enhancement With Photon-Counting Detector CT in Spontaneous Coronary Artery Dissection: Prospective Comparison With Cardiac MRI.

Objectives: Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome and myocardial infarction. Accurate diagnosis is crucial for appropriate management. This study aimed to compare late enhancement (LE) imaging using photon-counting detector (PCD)-CT with cardiac MRI in patients with SCAD in the acute phase and during follow-up and to introduce a novel approach for visualizing myocardial extracellular volume (ECV) distribution in the myocardium.

Materials and methods: This single-center prospective study enrolled patients with SCAD diagnosed with invasive coronary angiography. LE iodine imaging with spectral dual-source PCD-CT and cardiac MRI was performed early after symptom onset and at short-term follow-up. CT included coronary angiography and LE imaging (5 minutes after contrast). LE CT was assessed using the combination of conventional LE images, overlay images, polar maps, and with newly developed atlas maps. Atlas maps represent 2-dimensional maps with prefiltering applied to enable a simpler and more intuitive reading of ECV distribution across the myocardium. Cardiac MRI served as the reference standard for identifying pathologic myocardial segments based on late gadolinium enhancement (LGE) and edema on T2-weighted and T2-mapping images. Agreement between modalities was evaluated using Cohen's κ.

Results: Seventeen patients (median age, 44 years [interquartile range, 36-52]; 11 women) underwent 24 LE CT and cardiac MRI scans. Sixteen patients (median age, 44 years; 10 women) underwent acute phase imaging (median 6 days after symptom onset), and 8 patients (median age, 45 years; 6 women) underwent follow-up imaging (median 120 days after symptom onset). Atlas maps were helpful in detecting segments with pathological ECV and to adjudicate corresponding myocardial segments. Agreement between LE CT with LGE cardiac MRI was strong in the acute phase (κ = 0.832), improving to almost perfect when comparing LE-CT with both LGE and edema in cardiac MRI (κ = 0.944). At follow-up imaging, agreement further improved as edema resolved (κ = 0.956).

Conclusions: LE imaging with PCD-CT demonstrated strong agreement with cardiac MRI for detecting myocardial injury in SCAD, which further improved at follow-up when edema resolved. Newly introduced atlas maps proved useful for a simple and intuitive visualization of myocardial injury.