Association between fractional flow reserve and coronary plaque characteristics assessed by optical coherence tomography

Predictive value of plaque characteristics for identification of lesions causing ischemia

BACKGROUND

Functional assessment using fractional flow reserve (FFR) and anatomical assessment using optical coherence tomography (OCT) are used in clinical practice for patients with intermediate coronary stenosis. Moreover, coronary computed tomography angiography (CTA) is a common noninvasive imaging technique for evaluating suspected coronary artery disease before being referred for angiography. This study aimed to investigate the association between FFR and plaque characteristics assessed using coronary CTA and OCT for intermediate coronary stenosis.

METHODS

Based on a prospective multicenter registry, 159 patients having 339 coronary lesions with intermediate stenosis were included. All patients underwent coronary CTA before being referred for coronary angiography, and both FFR measurements and OCT examinations were performed during angiography. A stenotic lesion identified with FFR ≤0.80 was deemed diagnostic of an ischemia-causing lesion. The predictive value of plaque characteristics assessed using coronary CTA and OCT for identifying lesions causing ischemia was analyzed.

RESULTS

Stenosis severity and plaque characteristics on coronary CTA and OCT differed between lesions that caused ischemia and those that did not. In multivariate analysis, low attenuation plaque on coronary CTA (odds ratio [OR]=2.78; P=0.038), thrombus (OR=5.13; P=0.042), plaque rupture (OR=3.25; P=0.017), and intimal vasculature on OCT (OR=2.57; P=0.012) were independent predictors of ischemic lesions. Increasing the number of these plaque characteristics offered incremental improvement in predicting the lesions causing ischemia.

CONCLUSIONS

Comprehensive anatomical evaluation of coronary stenosis may provide additional supportive information for predicting the lesions causing ischemia.

The Association Between Quantitative Flow Ratio and Intravascular Imaging-defined Vulnerable Plaque Characteristics in Patients With Stable Angina and Non-ST-segment Elevation Acute Coronary Syndrome

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.

OCT-Derived Plaque Morphology and FFR-Determined Hemodynamic Relevance in Intermediate Coronary Stenoses

Background: optical coherence tomography (OCT) might allow identifying lesion features reportedly associated with plaque vulnerability and increased risk of clinical events. Previous studies on correlation between OCT and functional lesion significance indices reported contradictory results, yet integration of complementary information from both modalities is gaining increased interest. The aim of the study was to compare plaque morphology using OCT in hemodynamically relevant vs. non-relevant lesions by fractional flow reserve (FFR). Methods: consecutive patients with intermediate grade coronary stenoses by angiography were evaluated by both FFR and OCT in this single-center study. Stenoses were labeled hemodynamically relevant in case of the FFR ≤ 0.80. Minimal lumen area (MLA), fibrous cap thickness (FCT), minimal cap thickness over the calcium, angle of the calcium, and necrotic core within the lesions were evaluated. Results: a total of 105 patients (124 vessels) were analyzed. Of them, 65 patients were identified with at least one lesion identified as hemodynamically relevant by FFR (72 vessels, 58.1%). Lesions with FFR ≤0.80 presented with lower mean and minimal lumen area (3.46 ± 1.29 vs. 4.65 ± 2.19, p =0.001 and 1.84 ± 0.97 vs. 2.66 ± 1.40, p = 0.001) compared to patients with FFR > 0.80. No differences were found between groups in the mean and minimal FCT, mean, and maximal necrotic core, calcium angle, as well as the overall rate of calcified and lipid plaques. Conclusion: hemodynamic relevance of intermediate grade lesions correlated moderately with the luminal assessment by OCT. No differences were identified in the plaque morphology between relevant and non-relevant coronary stenoses by FFR.

Prevalence of Thin-Cap Fibroatheroma in Relation to the Severity of Anatomical and Physiological Stenosis

BACKGROUND

The relationship between the features of morphologically unstable plaque and physiological lesion severity remains elusive. We aimed to investigate this relationship using optical coherence tomography (OCT)-derived high-risk plaque characteristics and fractional flow reserve (FFR) as the degree of anatomical and physiological stenosis severity.

METHODS AND RESULTS

We investigated 286 de novo intermediate and severe coronary lesions in 248 patients who underwent OCT and FFR examinations. Lesions were divided into tertiles based on either FFR or quantitative coronary angiographic diameter stenosis (QCA-%DS). The OCT findings were compared among the tertiles of FFR and QCA-%DS. FFR and QCA tertiles were defined as follows: FFR-T1 (FFR <0.74), FFR-T2 (0.74≤FFR≤0.81), and FFR-T3 (FFR >0.81); and QCA-T1 (%DS ≥61%), QCA-T2 (51%≤%DS<61%), and QCA-T3 (%DS <51%). The prevalence of thin-cap fibroatheroma (TCFA) was significantly greater in FFR-T1 (20.0%) than in FFR-T2 and FFR-T3 (7.0%, P=0.03 and 7.7%, P=0.04, respectively), although no significant differences were observed among the QCA tertiles.

CONCLUSIONS

Physiological severity of coronary stenosis evaluated by FFR correlated with plaque instability in terms of TCFA. Preferable clinical outcomes for lesions with negative FFR based on the existing clinical evidence might be attributable to less likelihood of TCFA.

Two-year outcome after treatment of severely calcified lesions with newer-generation drug-eluting stents in acute coronary syndromes: A patient-level pooled analysis from TWENTE and DUTCH PEERS

BACKGROUND

Data on medium-term outcome of patients with acute coronary syndrome (ACS), treated with newer-generation durable polymer drug-eluting stents (DES) in severely calcified coronary lesions, are scarce. We aimed to assess the impact of severe coronary lesion calcification on clinical outcome of patients with ACS, treated with newer-generation DES.

METHODS

The TWENTE and DUTCH PEERS randomized trials comprise 1779 ACS patients, who were categorized into patients with versus without severe target lesion calcification. We performed a patient-level pooled analysis to assess 2-year outcome, including target vessel failure (TVF), a composite of cardiac death, target vessel-related myocardial infarction (MI), or target vessel revascularization (TVR).

RESULTS

Patients with severe target lesion calcification (n=340, 19.1%) were older (66.8±10.6 years vs. 62.8±11.5 years, p<0.001) and had more often diabetes (22.1% vs. 16.8%, p=0.02) and hypercholesterolemia (51.5% vs. 42.9%, p=0.005) than other patients (n=1439, 79.9%). In addition they showed a higher TVF rate (12.4% vs.7.0%, p=0.001), mainly related to a difference in TVR (6.8% vs. 3.3%, p=0.003). There was a borderline significant between-group difference in cardiac death (3.6% vs. 1.8%, p=0.05), but not in target vessel MI (3.8% vs.2.6%, p=0.23) and definite stent thrombosis (0.9% vs. 0.6%, p=0.71). Multivariate analysis demonstrated that severe lesion calcification was an independent risk factor of TVF (adjusted HR; 1.58, 95% CI: 1.23-2.03; p<0.001).

CONCLUSIONS

In patients with ACS, treatment of severely calcified lesions with newer-generation DES was associated with an overall higher clinical event risk - related in particular to a higher TVR rate, while the risk of MI was low.

A systematic review of imaging anatomy in predicting functional significance of coronary stenoses determined by fractional flow reserve

Fractional flow reserve (FFR) is the current gold standard to assess the physiological significance of coronary stenoses. With the development of coronary imaging techniques, several anatomic parameters have been investigated in vivo and their associations with FFR have been studied. The aim of this review is to summarize the accuracy of anatomic parameters derived by the present coronary imaging techniques including invasive coronary angiography, coronary computed tomography angiography, intravascular ultrasound and optical coherence tomography, in predicting a significant FFR. The impact of patient characteristics, lesion locations, variability of FFR and imaging resolution on the predictive ability are discussed.