Angiography-based estimation of coronary physiology: A frame is worth a thousand words

Correlation between abnormal microvascular perfusion and quantitative flow ratio after primary PCI in patients with STEMI

AIMS

Timely assessment of abnormal microvascular perfusion (MVP) may improve prognosis in patients with ST-segment elevation myocardial infarction (STEMI). This study aimed to determine the clinical implications of contrast-flow quantitative flow ratio (cQFR) in evaluating abnormal MVP and subsequent outcomes among STEMI patients after successful primary percutaneous coronary intervention (PPCI).

METHODS

The study population consisted of 2 independent cohorts. The diagnostic cohort was used to evaluate the correlation and diagnostic accuracy of cQFR in predicting abnormal MVP. In this cohort, MVP and cQFR of the culprit vessel (n = 186) were assessed from a prospective consecutive registry. Abnormal MVP was determined using myocardial contrast perfusion echocardiography (MCE) in the culprit vessel after PPCI. The prognostic cohort consisted of STEMI patients undergoing PPCI who were followed for a minimum of 2 years (n = 1931). The primary outcome was all-cause mortality.

RESULTS

In the diagnostic cohort, cQFR exhibited a moderate correlation with abnormal MVP assessed by MCE. Specificity, sensitivity, and area under the curve of post-PPCI cQFR to predict abnormal MVP were 81.6 %, 50.9 % and 0.709 (95 % confidence interval: 0.635-0.783), respectively, with the best cut-off value of 0.875. In the prognostic cohort, patients with cQFR <0.875 showed a significantly higher risk of long-term mortality compared to those with cQFR ≥0.875 (median follow-up: 52 months; mortality: 8.0 % vs. 3.8 %; p < 0.001). Cox-regression analysis revealed that cQFR ˂ 0.875 was an independent predictor of long-term mortality (adjusted HR: 2.132; 95 % CI: 1.358-3.346; p = 0.001) after adjusting for age, gender, diabetes mellitus, hyperlipidemia, symptom to balloon time, culprit vessel.

CONCLUSIONS

We found that cQFR demonstrated a relatively good performance in predicting abnormal MVP in patients with STEMI after successful PPCI. A cQFR value below 0.875 is an independent predictor of both abnormal MVP and long-term mortality. (Prognostic implication of cQFR in STEMI patients; NCT04996901).

Contemporary Functional Coronary Angiography: An Update

Functional coronary angiography (FCA) is a novel modality for assessing the physiology of coronary lesions, going beyond anatomical visualization by traditional coronary angiography. FCA incorporates indices like fractional flow reserve (FFR) and instantaneous wave-free ratio (IFR), which utilize pressure measurements across coronary stenoses to evaluate hemodynamic impacts and to guide revascularization strategies. In this review, we present traditional and evolving modalities and uses of FCA. We will also evaluate the existing evidence and discuss the applicability of FCA in various clinical scenarios. Finally, we provide insight into emerging evidence, current challenges, and future directions in FCA.

Prognostic Role of Functional SYNTAX Score Based on Quantitative Flow Ratio

BACKGROUND/OBJECTIVES

The quantitative flow ratio (QFR)-based functional Synergy Between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) score (FSSQFR) combines coronary arteries' anatomy and physiology.

METHODS

We performed an offline FSSQFR calculation in all-comers undergoing coronary angiography in a single center. Based on the tertiles of SYNTAX Score (SS), patients were divided into low-, intermediate-, and high-risk groups with the following cut-offs: SS/FSSQFR < 13, SS/FSSQFR: 13-21, and SS/FSSQFR: >21. The primary endpoint was the predictive value of the FSSQFR of the composite endpoint of all-cause death, myocardial infarction, ischemia-driven revascularization, hospitalization for heart failure, and life-threatening arrhythmias after the follow-up period.

RESULTS

This study included 410 patients. SS and FSSQFR were measured for all patients. After calculating FSSQFR, the risk stratification changed in 11% of the study population; more specifically, 26.8, 32.7, and 40.5% of patients were classified as high-, intermediate-, and low-risk, respectively. After a median 30.2 (25.7-33.7) months follow-up period, we recorded 85 events of the primary outcome. The high-risk FSSQFR group compared to the low-risk group had a significantly higher rate of the primary composite outcome (HR: 1.95, 95% CI 1.33-3.34, p = 0.016).

CONCLUSIONS

In our study, patients classified as the high-risk FSSQFR group had a significantly higher rate of cardiovascular adverse events.

Non-invasive fractional flow reserve estimation in coronary arteries using angiographic images

Coronary artery disease is the leading global cause of mortality and Fractional Flow Reserve (FFR) is widely regarded as the gold standard for assessing coronary artery stenosis severity. However, due to the limitations of invasive FFR measurements, there is a pressing need for a highly accurate virtual FFR calculation framework. Additionally, it's essential to consider local haemodynamic factors such as time-averaged wall shear stress (TAWSS), which play a critical role in advancement of atherosclerosis. This study introduces an innovative FFR computation method that involves creating five patient-specific geometries from two-dimensional coronary angiography images and conducting numerical simulations using computational fluid dynamics with a three-element Windkessel model boundary condition at the outlet to predict haemodynamic distribution. Furthermore, four distinct boundary condition methodologies are applied to each geometry for comprehensive analysis. Several haemodynamic features, including velocity, pressure, TAWSS, and oscillatory shear index are investigated and compared for each case. Results show that models with average boundary conditions can predict FFR values accurately and observed errors between invasive FFR and virtual FFR are found to be less than 5%.

Prognostic role of discordance between quantitative flow ratio and visual estimation in revascularization guidance

Aims

Revascularization guided by functional severity has presented improved outcomes compared with visual angiographic guidance. Quantitative flow ratio (QFR) is a reliable angiography-based method for functional assessment. We sought to investigate the prognostic value of discordance between QFR and visual estimation in coronary revascularization guidance.

Methods and results

We performed offline QFR analysis on all-comers undergoing coronary angiography. Vessels with calculated QFR were divided into four groups based on the decision to perform or defer percutaneous coronary intervention (PCI) and on the QFR result, i.e.: Group A (PCI-, QFR > 0.8); Group B (PCI+, QFR ≤ 0.8); Group C (PCI+, QFR > 0.8); Group D (PCI-, QFR ≤ 0.8). Patients with at least one vessel falling within the disagreement groups formed the discordance group, whereas the remaining patients formed the concordance group. The primary endpoint was the composite endpoint of cardiovascular death, myocardial infarction, and ischaemia-driven revascularization. Overall, 546 patients were included in the study. Discordance between QFR and visual estimation was found in 26.2% of patients. After a median follow-up period of 2.5 years, the discordance group had a significantly higher rate of the composite outcome (hazard ratio: 3.34, 95% confidence interval 1.99-5.60, P < 0.001). Both disagreement vessel Groups C and D were associated with increased cardiovascular risk compared with agreement Groups A and B.

Conclusion

Discordance between QFR and visual estimation in revascularization guidance was associated with a worse long-term prognosis. Our results highlight the importance of proper patient selection for intervention and the need to avoid improper stent implantations when not dictated by a comprehensive functional assessment.

Prognostic Value of Post-PCI Angiography-Derived Fractional Flow Reserve: A Systematic Review and Meta-Analysis of Cohort Studies

The post-percutaneous coronary intervention (post-PCI) fractional flow reserve (FFR) can detect suboptimal PCI or residual ischemia and potentially lead to fewer adverse clinical outcomes. We sought to investigate the predictive value of the angiography-derived FFR for adverse cardiovascular events in patients after PCI. We conducted a comprehensive search of electronic databases, MEDLINE, EMBASE, and the Cochrane Library, for studies published until March 2023 that investigated the prognostic role of angiography-derived fractional flow reserve values after PCI. We investigated the best predictive ability of the post-PCI angiography-derived FFR and relative risk (RR) estimates with 95% confidence intervals (CIs) between post-PCI angiography-derived FFR values and adverse events. Thirteen cohort studies involving 6961 patients (9719 vascular lesions; mean follow-up: 2.2 years) were included in this meta-analysis. The pooled HR of the studies using specific cut-off points for post-PCI angiography-derived FFR was 4.13 (95% CI, 2.92-5.82) for total cardiovascular events, while the pooled HRs for target vessel revascularization, cardiac death, target vessel myocardial infarction, and target lesion revascularization were 6.87 (95% CI, 4.93-9.56), 6.17 (95% CI, 3.52-10.80), 3.98 (95% CI, 2.37-6.66) and 6.27 (95% CI, 3.08-12.79), respectively. In a sensitivity analysis of three studies with 1789 patients assessing the predictive role of the post-PCI angiography-derived FFR as a continuous variable, we found a 58% risk reduction for future adverse events per 0.1 increase in the post-PCI angiography-derived FFR value. In conclusion, post-PCI angiography-derived FFR is an effective tool for predicting adverse cardiovascular events and could be potentially used in decision making, both during PCI and in the long-term follow-up.

Functional Evaluation of Intermediate Coronary Lesions with Integrated Computed Tomography Angiography and Invasive Angiography in Patients with Stable Coronary Artery Disease

Background and objectives

The hemodynamic evaluation of coronary stenoses undergoes a transition from wire-based invasive measurements to image-based computational assessments. However, fractional flow reserve (FFR) values derived from coronary CT angiography (CCTA) and angiography-based quantitative flow ratio have certain limitations in accuracy and efficiency, preventing their widespread use in routine practice. Hence, we aimed to investigate the diagnostic performance of FFR derived from the integration of CCTA and invasive angiography (FFR_CT-angio) with artificial intelligence assistance in patients with stable coronary artery disease (CAD).

Methods

Forty stable CAD patients with 67 target vessels (50%-90% diameter stenosis) were included in this single-center retrospective study. All patients underwent CCTA followed by coronary angiography with FFR measurement within 30 days. Both CCTA and angiographic images were combined to generate a three-dimensional reconstruction of the coronary arteries using artificial intelligence. Subsequently, functional assessment was performed through a deep learning algorithm. FFR was used as the reference.

Results

FFR_CT-angio values were significantly correlated with FFR values (r = 0.81, P < 0.001, Spearman analysis). Per-vessel diagnostic accuracy of FFR_CT-angio was 92.54%. Sensitivity and specificity in identifying ischemic lesions were 100% and 88.10%, respectively. Positive predictive value and negative predictive value were 83.33% and 100%, respectively. Moreover, the diagnostic performance of FFR_CT-angio was satisfactory in different target vessels and different segment lesions.

Conclusions

FFR_CT-angio exhibits excellent diagnostic performance of identifying ischemic lesions in patients with stable CAD. Combining CCTA and angiographic imaging, FFR_CT-angio may represent an effective and practical alternative to invasive FFR in selected patients.