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The impact of tissue characteristics of culprit lesion on myocardial tissue-level perfusion in non-ST-segment elevation acute coronary syndrome (NSTE-ACS) has not been elucidated. The IMAP-ACS-II study was a prospective observational study to investigate the relationship between pre-percutaneous coronary intervention (PCI) plaque characteristics and post-PCI myocardial perfusion with newly developed 40-MHz iMap IVUS in NSTE-ACS patients.
A total of 164 patients with coronary artery disease undergoing grayscale-IVUS and iMap-IVUS were enrolled in the IMAP-ACS-II study. The iMap-IVUS system analyzed coronary plaques as fibrotic, lipidic, necrotic, or calcified tissue based on the radiofrequency spectrum. Epicardial coronary perfusion was assessed by TIMI flow grade, and myocardial tissue-level perfusion was assessed by TIMI myocardial perfusion grade (TMPG) and TIMI myocardial perfusion frame count (TMPFC). Cardiac magnetic resonance (CMR)-verified microvascular obstruction (MVO) was also determined.
The percentages of necrotic areas at the minimum lumen area (MLA, 22.3±9.2% vs. 17.3±8.7%; P=0.002) and necrotic volume at the entire lesion (20.8±7.9% vs. 15.9±7.2%, P=0.0004) were significantly greater in NSTE-ACS than in stable angina pectoris. Patients with impaired epicardial coronary perfusion (TIMI 0-2) had higher percentage of the necrotic component both at MLA (P=0.002) and the entire lesion (P=0.001) than patients with TIMI 3. Patients with impaired myocardial perfusion (TMPFC>90) had greater necrotic percentages at MLA (P=0.025) and the entire culprit lesion (P<0.0001) than patients with TMPFC≤90. Moreover, CMR findings showed that MVO (+) patients had higher percentages of necrotic volume than patients without MVO (P=0.0001). Multivariate analysis showed that iMap-derived necrotic volume percentage was independently associated with reduced myocardial perfusion (OR 2.39 [95% CI 1.60 to 3.57], P = 0.009). The ROC curve showed that 20.04% was the optimal threshold of necrotic percentage of the entire lesion to predict impaired myocardial perfusion on CMR (sensitivity 82.3%, specificity 86.1%).
Impaired myocardial perfusion was associated with larger necrotic fraction of the lesion in NSTEMI patients. iMAP-IVUS might be useful for identifying culprit plaques at high risk for developing impaired myocardial tissue-level perfusion(Trial Registration: ChiCTR-OCH-13003046).