Machine-learning-based prediction of fractional flow reserve after percutaneous coronary intervention

BACKGROUND AND AIMS

Post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) reflects residual atherosclerotic burden and is associated with future events. How much post-PCI FFR can be predicted based on baseline basic information and the clinical relevance have not been investigated.

METHODS

We compiled a multicenter registry of patients undergoing pre- and post-PCI FFR. Machine-learning (ML) algorithms were designed to predict post-PCI FFR levels from baseline demographics, quantitative coronary angiography, and pre-PCI FFR. FFR deviation was defined as actual minus ML-predicted post-PCI FFR levels, and its association with incident target vessel failure (TVF) was evaluated.

RESULTS

Median (IQR) pre- and post-PCI FFR values were 0.71 (0.61, 0.77) and 0.88 (0.84, 0.93), respectively. The Spearman correlation coefficient of the actual and predicted post-PCI FFR was 0.54 (95% CI: 0.52, 0.57). FFR deviation was non-linearly associated with incident TVF (HR [95% CI] with Q3 as reference: 1.65 [1.14, 2.39] in Q1, 1.42 [0.98, 2.08] in Q2, 0.81 [0.53, 1.26] in Q4, and 1.04 [0.69, 1.56] in Q5). A model with polynomial function of continuous FFR deviation indicated increasing TVF risk for FFR deviation ≤0 but plateau risk with FFR deviation >0.

CONCLUSIONS

An ML-based algorithm using baseline data moderately predicted post-PCI FFR. The deviation of post-PCI FFR from the predicted value was associated with higher vessel-oriented event.

Coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance imaging of coronary sinus: a meta-analysis

BACKGROUND

Phase-contrast cine cardiovascular magnetic resonance (CMR) of the coronary sinus has emerged as a non-invasive method for measuring coronary sinus blood flow and coronary flow reserve (CFR). However, its clinical utility has not yet been established. Here we performed a meta-analysis to clarify the clinical value of CMR-derived CFR in various cardiovascular diseases.

METHODS

An electronic database search was performed of PubMed, Web of Science Core Collection, Cochrane Advanced Search, and EMBASE. We compared the CMR-derived CFR of various cardiovascular diseases (stable coronary artery disease [CAD], hypertrophic cardiomyopathy [HCM], dilated cardiomyopathy [DCM]) and control subjects. We assessed the prognostic value of CMR-derived CFR for predicting major adverse cardiac events (MACE) in patients with stable CAD.

RESULTS

A total of 47 eligible studies were identified. The pooled CFR from our meta-analysis was 3.48 (95% confidence interval [CI], 2.98-3.98) in control subjects, 2.50 (95% CI, 2.38-2.61) in stable CAD, 2.01 (95% CI, 1.70-2.32) in cardiomyopathies (HCM and DCM). The meta-analysis showed that CFR was significantly reduced in stable CAD (mean difference [MD] = -1.48; 95% CI, -1.78 to -1.17; p < 0.001; I2 = 0%; p for heterogeneity = 0.33), HCM (MD = -1.20; 95% CI, -1.63 to -0.77; p < 0.001; I2 = 0%; p for heterogeneity = 0.49), and DCM (MD = -1.53; 95% CI, -1.93 to -1.13; p < 0.001; I2 = 0%; p for heterogeneity = 0.45). CMR-derived CFR was an independent predictor of MACE for patients with stable CAD (hazard ratio = 0.52 per unit increase; 95% CI, 0.37-0.73; p < 0.001; I2 = 84%, p for heterogeneity < 0.001).

CONCLUSIONS

CMR-derived CFR was significantly decreased in cardiovascular diseases, and a decreased CFR was associated with a higher occurrence of MACE in patients with stable CAD. These results suggest that CMR-derived CFR has potential for the pathological evaluation of stable CAD, cardiomyopathy, and risk stratification in CAD.

Robust Association Between Changes in Coronary Flow Capacity Following Percutaneous Coronary Intervention and Vessel-Oriented Outcomes and the Implication for Clinical Practice

Background

Coronary flow capacity (CFC) is a potentially important physiologic marker of ischemia for guiding percutaneous coronary intervention (PCI) indication, while the changes through PCI have not been investigated.

Objectives

To assess the determinants and prognostic implication of delta CFC, defined as the change in the CFC status following PCI.

Materials and Methods

From a single-center registry, a total of 450 patients with chronic coronary syndrome (CCS) who underwent fractional flow reserve (FFR)-guided PCI with pre-/post-PCI invasive coronary physiological assessments were included. Associations between PCI-related changes in thermodilution method-derived CFC categories and incident target vessel failure (TVF) were assessed.

Results

The mean (SD) age was 67.1 (10.0) years and there were 75 (16.7%) women. Compared with patients showing no change in CFC categories after PCI, patients with category worsened, +1, +2, and +3 category improved had the hazard ratio (95% CI) for incident TVF of 2.27 (0.95, 5.43), 0.85 (0.33, 2.22), 0.45 (0.12, 1.63), and 0.14 (0.016, 1.30), respectively (p for linear trends = 0.0051). After adjustment for confounders, one additional change in CFC status was associated with 0.61 (0.45, 0.83) times the hazard of TVF. CFC changes were largely predicted by the pre-PCI CFC status.

Conclusion

Coronary flow capacity changes following PCI, which was largely determined by the pre-PCI CFC status, were associated with the lower risk of incident TVF in patients with CCS who underwent PCI. The CFC changes provide a mechanistic explanation on potential favorable effect of PCI on reducing vessel-oriented outcome in lesions with reduced CFC and low FFR.

Differential Impact of Coronary Revascularization on Long-Term Clinical Outcome According to Coronary Flow Characteristics: Analysis of the International ILIAS Registry

BACKGROUND

Coronary pressure indices such as fractional flow reserve are the standard for guiding elective revascularization. However, considering additional coronary flow parameters could further individualize and optimize the decision on revascularization. We aimed to investigate the potentially differential prognostic associations of elective percutaneous coronary intervention (PCI) according to coronary flow properties represented by coronary flow reserve (CFR), coronary flow capacity (CFC), and baseline CFC (bCFC).

METHODS

From the ILIAS Registry (Inclusive Invasive Physiological Assessment in Angina Syndromes) composed of 16 hospitals globally from 7 countries, patients with obstructive coronary artery disease who underwent invasive coronary physiological assessment were included (N=2370 vessels). We assessed effect measure modifications of the association of PCI and 5-year target vessel failure according to CFR, CFC, and bCFC either assessed by Doppler-technique or thermodilution-method.

RESULTS

The mean age of the population was 63.3 years, and there were 1322 (73.6%) males. Median fractional flow reserve was 0.85, and PCI was performed in 600 (25.3%) vessels. Reduced CFR, CFC, and abnormal bCFC were defined in 988 (41.7%), 542 (22.9%), and 600 (25.3%) vessels, respectively. Significant effect measure modifications were observed by CFC either in odds ratio (P=0.0018), additive (P=0.029), and hazard ratio scale (P=0.0002). The absolute risk of 5-year target-vessel failure was higher if treated by PCI in vessels with normal CFC by 1.8 (-1.7 to 5.3) percent, while that was lower by -5.9 (-12 to -0.1) percent in those with reduced CFC. CFR and bCFC were not significant effect modifiers in any scales. Similar associations were observed in per-patient analyses, whereas the findings were less robust.

CONCLUSIONS

We observed qualitative effect measure modification of PCI and 5-year clinical outcomes according to CFC status in additive scale. CFR and bCFC were not robust effect modifiers. Therefore, CFC could be potentially used to optimize the patient selection for elective PCI treatment combined with fractional flow reserve.

Clinical outcomes of Fractional Flow Reserve-Guided Percutaneous Coronary Intervention By Coronary Flow Capacity Status in Stable Lesions

BACKGROUND

Coronary flow capacity (CFC) provides integrated information about coronary flow reserve (CFR) and hyperaemic coronary flow and is useful for identifying coronary flow limitation.

AIMS

The aim of this study was to investigate the effect of percutaneous coronary intervention (PCI) on vessel-related major adverse cardiovascular events (MACE) according to CFC status in stable coronary lesions.

METHODS

From a global, multicentre registry of comprehensive physiological assessment, a total of 1,397 patients (1,694 vessels) were analysed. Low CFC was defined for lesions with reduced CFR and inverse of hyperaemic mean transit time (1/hTmn). A predefined definition of CFC (CFR <2.0 and 1/hTmn less than the corresponding percentile) was assessed first in a multivariable marginal Cox proportional model with the interaction term between CFC status and PCI (performed or not), and then the optimal definition of CFC was explored.

RESULTS

We observed a significant interaction between predefined low CFC and PCI (p=0.067). With the optimal definition of CFC (CFR ≤3.2 and 1/hTmn ≤2.8), the HR (95% CI) of PCI was 0.278 (0.103-0.751) and 1.393 (0.783-2.478) in lesions with low and normal CFC, respectively. If lesions with fractional flow reserve (FFR) ≤0.8 and normal CFC had been deferred, the number of PCI would have decreased by 64%.

CONCLUSIONS

FFR-guided PCI for low CFC lesions was associated with reduced incidence of MACE in low CFC but not in normal CFC lesions. Our results suggest the potential use of CFC in combination with FFR for optimising the indication for PCI by reducing potentially unbeneficial PCI.

CLINICAL TRIALS REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT03690713.

FFR=1.0 flow changes after percutaneous coronary intervention

BACKGROUND

The present study investigated the relationships between physiological indices and increased coronary flow during percutaneous coronary intervention (PCI) using a novel index of "anticipated maximum flow" [AMF; theoretical coronary flow of fractional flow reserve (FFR) = 1]. FFR-guided PCI aims to increase coronary flow, whereas recent studies have reported that PCI does not necessarily increase coronary flow despite improvement in FFR.

METHODS

This retrospective analysis was performed in 71 functionally significant lesions treated with elective PCI. AMF obtained by hyperemic average peak coronary flow velocity (h-APV) divided by FFR would not change after PCI given the constant microvascular resistance, which is the assumption of FFR as a surrogate of coronary flow. We evaluated the relationship between AMF and coronary flow during PCI.

RESULTS

Post-PCI AMF was significantly different from pre-PCI AMF (p = 0.022), which impacted discordance between FFR improvement and change in coronary flow. Coronary flow increase >50% was associated with smaller minimum lumen diameter (p = 0.010), greater diameter stenosis (p = 0.003), lower pre-PCI FFR (p < 0.001), lower pre-PCI coronary flow reserve (p = 0.001), higher pre-PCI hyperemic stenosis resistance (p < 0.001), lower pre-PCI h-APV (p = 0.001), and lower pre-PCI AMF (p = 0.031). Pre-PCI AMF provided significant incremental predictive capability for coronary flow increase >50% when added to the clinical model including pre-PCI FFR.

CONCLUSION

Pre-PCI AMF provided incremental ability to predict increased coronary flow after PCI and impacted the discordance between FFR improvement and increased coronary flow.

Prognostic implication of global myocardial blood flow in patients with ST-segment elevation myocardial infarction

The prognostic implications of cardiovascular magnetic resonance imaging (CMR)-derived hyperemic myocardial blood flow (MBF) in patients with ST-elevation myocardial infarction (STEMI) are unknown. This study sought to investigate the incremental prognostic value of hyperemic MBF over conventional CMR markers to identify patients with high risk of future incidence of patient-oriented composite outcomes (POCO) and major adverse cardiac events (MACE) after STEMI. A total of 237 patients who presented with STEMI were prospectively enrolled. The CMR protocol included left-ventricular ejection fraction (LVEF), late gadolinium enhancement (LGE) and microvascular obstruction (MVO) measurement, and volumetric MBF assessment. During a median follow-up of 2.6 years, 47 patients experienced POCO (primary outcome) and 21 patients had MACE. In a multivariable model, multivessel disease, LGE, MVO, and hyperemic MBF were independently associated with POCO. Addition of hyperemic MBF to the model consisting of GRACE score, multivessel disease, LVEF, LGE, and MVO significantly improved the predictive efficacy (integrated discrimination improvement 0.020, p = 0.021). Patients with low hyperemic MBF had significantly higher incidence of MACE compared to those with high hyperemic MBF in propensity score matching analysis (p = 0.018). In conclusion, CMR-derived hyperemic MBF could provide independent and incremental prognostic value over LVEF, LGE, and MVO in patients with STEMI.

Improvement of Fractional Flow Reserve after Percutaneous Coronary Intervention Does Not Necessarily Indicate Increased Coronary Flow

Coronary flow is expected to increase by epicardial lesion modification after successful percutaneous coronary intervention (PCI) in stable angina. According to the concept of fractional flow reserve (FFR), the improvement in FFR after PCI reflects the extent of coronary flow increase. However, this theory assumes that hyperaemic microvascular resistance does not change after PCI, which is being refuted in recent studies. The authors quantitated regional absolute coronary blood flow (ABF) before and after PCI using a thermodilution method and compared it with FFR in 28 patients with stable coronary artery disease who had undergone successful PCI. Although FFR indicated changes in ABF, with a mean difference of -5.5 ml/min, there was no significant relationship between individual changes in FFR and in ABF (R=0.27, p=0.16). The discrepancy was partly explained by changes in microvascular resistance following PCI. These results suggest that changes in FFR do not necessarily indicate an increase in absolute coronary blood flow following PCI in individual patients, although they could be correlated in a cohort level.