Long-term prognostic implications of hemodynamic and plaque assessment using coronary CT angiography

Prognostic Time Frame of Plaque and Hemodynamic Characteristics and Integrative Risk Prediction for Acute Coronary Syndrome

BACKGROUND

The relevant time frame for predicting future acute coronary syndrome (ACS) based on coronary lesion characteristics remains uncertain.

OBJECTIVES

The aim of this study was to investigate the association of lesion characteristics with test-to-event time and their prognostic impact on ACS.

METHODS

The EMERALD II (Exploring the Mechanism of Plaque Rupture in Acute Coronary Syndrome Using Coronary CT Angiography and Computational Fluid Dynamics II) study analyzed 351 patients who underwent coronary computed tomography angiography (CTA) and experienced ACS between 1 month and 3 years of follow-up. Lesions identified on coronary CTA were classified as culprit (n = 363) or nonculprit (n = 2,088) on the basis of invasive coronary angiography findings at the time of ACS. Core laboratory coronary CTA analyses assessed 4 domains: degree of stenosis, plaque burden, number of adverse plaque characteristics (APC) (low-attenuation plaque, positive remodeling, spotty calcification, and napkin-ring sign), and changes in coronary CTA-derived fractional flow reserve across the lesion (ΔFFRCT). Patients were categorized into short (<1 year), mid (1-2 years), and long (2-3 years) test-to-event time groups.

RESULTS

Patient characteristics, including cardiovascular risk factors, did not differ across short, mid, and long test-to-event groups (P > 0.05 for all), and the proportion of ACS culprit lesions was similar (P = 0.552). Among culprit lesions, shorter test-to-event time was associated with higher luminal stenosis, plaque burden, and ΔFFRCT (P for trend < 0.001 for all). The predictability for ACS culprit lesions based on the combined 4 characteristics tended to decrease over time and significantly reduced beyond 2 years (AUC: 0.851 vs 0.741; P = 0.006). In predicting ACS risk within test-to-event time <2 years using obstructive lesions (stenosis ≥ 50%), APC ≥2, plaque burden ≥70%, and ΔFFRCT ≥0.10, the risk was elevated compared to the average proportion of lesions becoming ACS culprit (12.1%) in the following subsets: lesions with 4 characteristics (proportion of lesions becoming ACS culprit: 49.3%; P < 0.001), lesions with 3 characteristics (obstructive lesions with plaque burden ≥70% and either ΔFFRCT ≥0.10 [proportion of lesions becoming ACS culprit: 33.0%; P < 0.001] or APC ≥2 [proportion of lesions becoming ACS culprit: 31.2%; P < 0.001]), and lesions with 2 characteristics (plaque burden ≥70% and ΔFFRCT ≥0.10; proportion of lesions becoming ACS culprit: 21.5%; P = 0.016).

CONCLUSIONS

Increased luminal stenosis, plaque burden, and ΔFFRCT were associated with shorter test-to-ACS event time. The prognostic impact of lumen, plaque, and local hemodynamic characteristics was most relevant to ACS risk within a 2-year period, with higher risk observed when specific combinations of them were present. (Exploring the Mechanism of Plaque Rupture in Acute Coronary Syndrome Using Coronary CT Angiography and Computational Fluid Dynamics II [EMERALD II] Study; NCT03591328).

Diagnostic Performance of On-Site Automatic Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve

BACKGROUND AND OBJECTIVES

Fractional flow reserve (FFR) is an invasive standard method to identify ischemia-causing coronary artery disease (CAD). With the advancement of technology, FFR can be noninvasively computed from coronary computed tomography angiography (CCTA). Recently, a novel simpler method has been developed to calculate on-site CCTA-derived FFR (CT-FFR) with a commercially available workstation.

METHODS

A total of 319 CAD patients who underwent CCTA, invasive coronary angiography, and FFR measurement were included. The primary outcome was the accuracy of CT-FFR for defining myocardial ischemia evaluated with an invasive FFR as a reference. The presence of ischemia was defined as FFR ≤0.80. Anatomical obstructive stenosis was defined as diameter stenosis on CCTA ≥50%, and the diagnostic performance of CT-FFR and CCTA stenosis for ischemia was compared.

RESULTS

Among participants (mean age 64.7±9.4 years, male 77.7%), mean FFR was 0.82±0.10, and 126 (39.5%) patients had an invasive FFR value of ≤0.80. The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR were 80.6% (95% confidence interval [CI], 80.5-80.7%), 88.1% (95% CI, 82.4-93.7%), 75.6% (95% CI, 69.6-81.7%), 70.3% (95% CI, 63.1-77.4%), and 90.7% (95% CI, 86.2-95.2%), respectively. CT-FFR had higher diagnostic accuracy (80.6% vs. 59.1%, p<0.001) and discriminant ability (area under the curve from receiver operating characteristic curve 0.86 vs. 0.64, p<0.001), compared with anatomical obstructive stenosis on CCTA.

CONCLUSIONS

This novel CT-FFR obtained from an on-site workstation demonstrated clinically acceptable diagnostic performance and provided better diagnostic accuracy and discriminant ability for identifying hemodynamically significant lesions than CCTA alone.

Long-term prognostic implications of CT angiography-derived fractional flow reserve: Results from the DISCOVER-FLOW study

BACKGROUND & OBJECTIVES

The long-term prognostic implications of CT angiography-derived fractional flow reserve (FFRCT) remains unclear. We aimed to explore the long-term outcomes of FFRCT in the first-in-human study of it.

MATERIALS & METHODS

A total of 156 vessels from 102 patients with stable coronary artery disease, who underwent coronary CT angiography (CCTA) and invasive FFR measurement, were followed. The primary endpoint was target vessel failure (TVF), including cardiovascular death, target vessel myocardial infarction, and target vessel revascularization. Outcome analysis with FFRCT was performed on a per-vessel basis using a marginal Cox proportional hazard model.

RESULTS

During median 9.9 years of follow-up, TVF occurred in 20 (12.8%) vessels. FFRCT ​≤0.80 discriminated TVF (hazard ratio [HR] 2.61, 95% confidence interval [CI] 1.06, 6.45). Among 94 vessels with deferral of percutaneous coronary intervention (PCI), TVF risk was inversely correlated with FFRCT ​(HR 0.62 per 0.1 increase, 95% CI 0.44, 0.86), with the cumulative incidence of TVF being 2.6%, 15.2%, and 28.6% for vessels with FFRCT ​>0.90, 0.81-0.90, and ≤0.80, respectively (p-for-trend 0.005). Predictive value for clinical outcomes of FFRCT was similar to that of invasive FFR (c-index 0.79 vs 0.71, P ​= ​0.28). The estimated TVF risk was higher in the deferral of PCI group than the PCI group for vessels with FFRCT ≤0.81.

CONCLUSION

FFRCT showed improved long-term risk stratification and displayed a risk continuum similar to invasive FFR.

CLINICAL TRIAL REGISTRATION

NCT01189331.

Noninvasive Coronary Physiological Assessment Derived From Computed Tomography

Identifying functional significance using physiological indexes is a standard approach in decision-making for treatment strategies in patients with coronary artery disease. Recently, coronary computed tomography angiography-based physiological assessments, such as computed tomography perfusion and fractional flow reserve derived from coronary computed tomography angiography (FFR-CT), have emerged. These methods have provided incremental diagnostic values for ischemia-causing lesions over anatomical stenosis defined solely by coronary computed tomography angiography. Clinical data have demonstrated their prognostic value in the prediction of adverse cardiovascular events. Several randomized controlled studies have shown that clinical use of FFR-CT can reduce unnecessary invasive procedures compared to usual care. Recent studies have also expanded the role of FFR-CT in defining target lesions for revascularization by acquiring noninvasive lesion-specific hemodynamic indexes like ΔFFR-CT. This review encompasses the current evidence of the diagnostic and prognostic performance of computed tomography-based physiological assessment in defining ischemia-causing lesions and adverse cardiac events, its clinical impact on treatment decision-making, and implications for revascularization.

Coronary Physiology-Based Approaches for Plaque Vulnerability: Implications for Risk Prediction and Treatment Strategies

In the catheterization laboratory, the measurement of physiological indexes can help identify functionally significant lesions and has become one of the standard methods to guide treatment decision-making. Plaque vulnerability refers to a coronary plaque susceptible to rupture, enabling risk prediction before coronary events, and it can be detected by defining a certain type of plaque morphology on coronary imaging modalities. Although coronary physiology and plaque vulnerability have been considered different attributes of coronary artery disease, the underlying pathophysiological basis and clinical data indicate a strong correlation between coronary hemodynamic properties and vulnerable plaque. In prediction of coronary events, emerging data have suggested independent and additional implications of a physiology-based approach to a plaque-based approach. This review covers the fundamental interplay between coronary physiology and plaque morphology during disease progression with clinical data supporting this relationship and examines the clinical relevance of physiological indexes in prediction of clinical outcomes and therapeutic decision-making along with plaque vulnerability.