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percutaneouscoronary intervention ; intravascular ultrasound ; myocardial infarction ; virtual histology
Abstract:
Acute coronary syndromes are the result of acute imbalance between myocardial demand for oxygen and the possibility of delivery by the coronary arteries. This condition is usually caused by a resulting massive thrombus that develops in place of a ruptured atherosclerotic plaque, leading to partial or complete occlusion of the coronary artery supplying a miocardium. An occlusion or severe stenosis (angiographic culprit lesion) of the infarct related artery (IRA), in STelevation myocardial infarction (STEMI) as well as in non-ST-elevation myocardial infarction (NSTEMI), is frequently located at the site of the maximum thrombus burden, whereas the origin of the plaque rupture (the true culprit) can be situated proximal or distal to it. This may lead to incomplete stent coverage of lesion which is responsible for acute coronary syndrome, if the procedure was performed only under angiographic guidance. We examined coverage of the true culprit lesion in 20 STEMI and 20 NSTEMI patients who had TIMI 3 flow restored in IRA (with or without thrombus aspiration) with angiographically-guided direct stenting. The lesion was imaged with virtual histology intravascular ultrasound (VH-IVUS) pre- and postintervention (blinded to the operator). To assess the phenomenon of "geographic miss" (GM) in relation to the previous implanted stent, a composition of plaque by virtual histology was performe ; d in the segment 10 mm proximal (REF PROX) and distal (DIST REF) to the stent. “Geographic miss” was defined as the presence of uncovered by a stent an atherosclerotic plaque with large necrotic core covered with a thin fibrous cap (TCFA, thin cap fibroatheroma). "Geographicmiss" was found in 50% of patients with STEMI and 35% of NSTEMI. The main reason of the "geographic miss" was the very often incidence of necroticcore tissue and the accumulation of plaque rupture proximal to the sites with the smallest lumen, which was seen on angiography. Implementation of intravascular ultrasound virtual histology, illustrated the phenomenon of "geographic miss" in patients with myocardial infarction, is safe and provides the operator to keep the additional information to further optimize coronary angioplasty. High incidence of this phenomenon in patients with myocardial infarction justifies the need of randomized trials which would answer the question of whether the optimization result of coronary angioplasty in patients with acute myocardial infarction based on intravascular ultrasound and virtual histology data may lead into better long-term results.