Predominantly diastolic coronary narrowing caused by iatrogenic left main dissection: deferral of stenting by combined angiographic- and ultrasound-based functional assessment

Case PresentationA 65-year-old woman with a history of arterial hypertension and type 2 diabetes mellitus presented with acute chest pain and dyspnea.Electrocardiography showed only mild ST-T abnormalities, while high-sensitivity cardiac troponin I was elevated (310 ng/L) with a rising trend to 6530 ng/L.Transthoracic echocardiography revealed reduced left ventricular ejection fraction with hypokinesis of the lateral and apical segments.The patient was diagnosed with non-ST-segment elevation myocardial infarction and underwent coronary angiography.The right coronary artery was free of significant stenosis.The left main coronary artery appeared angiographically normal, with a mild proximal LAD lesion.A critical stenosis was identified in the obtuse marginal branch of the left circumflex artery and treated successfully with stent implantation.At the end of the intervention, an iatrogenic dissection of the left main extending into the LAD was identified, likely due to deep engagement of the guiding catheter (Fig. 1, Supplementary Video 1).IVUS imaging confirmed a Type 2 dissection with an intimal flap extending from the LM into the proximal LAD (Supplementary Video 2).Angiographic assessment revealed an unusual dynamic pattern with more pronounced luminal narrowing during diastole.To evaluate functional significance, angiographyderived Murray law-based quantitative flow ratio (QFR) was calculated separately for diastole and systole.The values were 0.76 and 0.94, respectively, resulting in a cardiac cycle-averaged QFR (AQFR) of 0.85 (Fig. 2).Additionally, IVUS-derived Ultrasonic Flow Ratio (UFR) was calculated, yielding a value of 0.87, confirming preserved coronary flow [4, 5] (Fig. 3).