Dynamic stenosis of left main coronary artery responsible for sudden cardiac arrest: new insights from coronary computed tomography angiography Laetitia Neuvillers 1, Lisa Guirgis 2, Virginie Lambert 1, and Jean-François Paul 3* 1 Cardiology Department, Institut Mutualiste Montsouris, 42 Bd Jourdan, 7504, Paris, France; 2 Cardiopediatry Department, Hoˆ pital Marie Lannelongue, 92350, Le Plessis-Robinson, France; and 3 Radiology Department, Institut Mutualiste Montsouris, 42 Bd Jourdan, 7504, Paris, France *Corresponding author. Tel: +33 1 56616057, Email: [email protected] An 11-year-old boy with an unremarkable medical history collapsed during sports practice with cardiac arrest and was successfully resuscitated after immediate cardiac massage by his school teacher. The electrocardiogram (Panel A) showed anterior myocardial infarction with aVR ST-elevation. Coronary angiography (Panels B and C, Supplementary material online, S1) and ventriculography (Supplementary material online, S2) showed no coronary stenosis and antero-apical akinesia. Coronary computed tomography (CT) showed that the origin of the left main coronary artery (LMCA) arose from the posterior sinus close to the left non-coronary commissure (Panel D), at the level of the sinotubular junction. Take-off was acute. Only mild stenosis was seen on the diastolic images (Panels E and F, top). However, end-systolic reconstructions showed severe systolic stenosis (Panels E and F, bottom). Coronary reimplantation surgery was recommended by the heart team as the only means of correcting this anomaly. The exercise-induced ischaemia may be explained by several mechanisms, alone or in combination: • The exercise-induced blood pressure increase, resulting in greater pressure on the aortic wall and therefore, potentially, in increased stenosis due to the acute take-off; • Aortic root expansion due to the increased blood flow during systole (as shown in E, with a 3-mm increase in the long-axis diameter at the sinotubular junction), resulting in systolic stretching of the LMCA, with severe luminal narrowing (Panels E and F, bottom); • The exercise-induced heart rate increase, with impaired blood flow during systole (due to the stenosis) and diastole (due to the short diastolic time). This case underlines the importance of dynamic CT acquisition for comprehensive evaluation of anomalous coronary connections. Supplementary material is available at European Heart Journal online.