Abstract
Background: This study aimed to examine whether quantitative flow ratio (QFR), an angiography-based computation of fractional flow reserve, was associated with intravascular imaging-defined vulnerable plaque features, such as thin cap fibroatheroma (TCFA) in patients with stable angina, and non-ST-segment elevation acute coronary syndrome.Methods: Patients undergoing optical coherence tomography (OCT) or intravascular ultrasound (IVUS) examinations were identified from two prospective studies and their interrogated vessels were assessed with QFR. Lesions in the OCT cohort were classified into tertiles: QFR-T1 (QFR ≤ 0.85), QFR-T2 (0.85 < QFR ≤ 0.93), and QFR-T3 (QFR > 0.93). Lesions in the IVUS cohort were classified dichotomously as low or high QFR groups.Results: This post-hoc analysis included 132 lesions (83 for OCT and 49 for IVUS) from 126 patients. The prevalence of OCT-TCFA was significantly higher in QFR-T1 (50%) than in QFR-T2 (14%) and QFR-T3 (19%) (p = 0.003 and 0.018, respectively). Overall significant differences were also observed among tertiles in maximum lipid arc, thinnest fibrous cap thickness, and minimal lumen area (p = 0.017, 0.040, and <0.001, respectively). Thrombus was more prevalent in QFR-T1 (39%) than in QFR-T2 (3%), and QFR-T3 (12%) (p = 0.001 and 0.020, respectively). In the multivariable analysis, QFR ≤ 0.80 remained as a significant determinant of OCT-TCFA regardless of the presence of NSTE-ACS and the level of low-density lipoprotein cholesterol (adjusted OR: 4.387, 95% CI 1.297–14.839, p = 0.017). The diagnostic accuracy of QFR was moderate in identifying lesions with OCT-TCFA (area under the curve: 0.72, 95% CI 0.58–0.86, p = 0.003). In the IVUS cohort, significant differences were found between two groups in minimal lumen area and plaque burden but not in the distribution of virtual histology (VH)-TCFA (p = 0.025, 0.036, and 1.000, respectively).Conclusions: Lower QFR was related to OCT-defined plaque vulnerability in angiographically mild-to-intermediate lesions. The QFR might be a useful tool for ruling out high-risk plaques without using any pressure wire or vasodilator.
Highlights
The fractional flow reserve (FFR) is widely accepted as an essential tool in assessing the physiological severity of coronary stenosis, and guiding decision-making for myocardial revascularization [1, 2]
Postmortem studies found that a plaque prone to rupture is typically characterized by a large lipid or necrotic core that is covered by a thin fibrous cap and, introduced the concept of thin cap fibroatheroma (TCFA) to describe this atherosclerotic plaque type [8, 9]
Other vulnerable indicators include minimal lumen area, plaque burden, macrophage infiltration, and lipid arc circumferential extension [10, 11]. These vulnerable characteristics can be visualized in vivo by intravascular imaging modalities, such as virtual histology intravascular ultrasound (VH-IVUS) and high-resolution optical coherence tomography (OCT) [12]
Summary
The fractional flow reserve (FFR) is widely accepted as an essential tool in assessing the physiological severity of coronary stenosis, and guiding decision-making for myocardial revascularization [1, 2]. The association between coronary physiology and OCT/IVUSdefined plaque vulnerability remains elusive and warrants more evidence Given this background, we sought to further investigate the relationships between QFR and lesion-specific morphological characteristics detected by OCT or IVUS, in patients presenting stable angina and in culprit lesions from patients with medically stabilized non-ST-segment elevation ACS (NSTE-ACS). This study aimed to examine whether quantitative flow ratio (QFR), an angiography-based computation of fractional flow reserve, was associated with intravascular imaging-defined vulnerable plaque features, such as thin cap fibroatheroma (TCFA) in patients with stable angina, and non-ST-segment elevation acute coronary syndrome
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