Long-term Patient Prognostication by Coronary Flow Reserve and Index of Microcirculatory Resistance: International Registry of Comprehensive Physiologic Assessment

Invasive assessment of coronary microvascular dysfunction and cardiovascular outcomes across the full spectrum of CHD: a meta-analysis

INTRODUCTION AND OBJECTIVES

Coronary microvascular dysfunction (CMD) is highly prevalent and is recognized as an important clinical entity in patients with coronary heart disease (CHD). Nevertheless, the association of CMD with adverse cardiovascular events in the spectrum of CHD has not been systemically quantified.

METHODS

We searched electronic databases for studies on patients with CHD in whom coronary microvascular function was measured invasively, and clinical events were recorded. The primary endpoint was major adverse cardiac events (MACE), and the secondary endpoint was all-cause death. Estimates of effect were calculated using a random-effects model from published risk ratios.

RESULTS

We included 27 studies with 11 404 patients. Patients with CMD assessed by invasive methods had a higher risk of MACE (RR, 2.18; 95%CI, 1.80-2.64; P<.01) and all-cause death (RR, 1.88; 95%CI, 1.55-2.27; P<.01) than those without CMD. There was no significant difference in the impact of CMD on MACE (interaction P value=.95) among different invasive measurement modalities. The magnitude of risk of CMD assessed by invasive measurements for MACE was greater in acute coronary syndrome patients (RR, 2.84, 95%CI, 2.26-3.57; P<.01) than in chronic coronary syndrome patients (RR, 1.77, 95%CI, 1.44-2.18; P<.01) (interaction P value<.01).

CONCLUSIONS

CMD based on invasive measurements was associated with a high incidence of MACE and all-cause death in patients with CHD. The magnitude of risk for cardiovascular events in CMD as assessed by invasive measurements was similar among different methods but varied among CHD populations.

Understanding Patient Characteristics and Coronary Microvasculature: Early Insights from the Coronary Microvascular Disease Registry

Coronary angiography has limitations in accurately assessing the coronary microcirculation. A new comprehensive invasive hemodynamic assessment method utilizing coronary flow reserve (CFR) and the index of microvascular resistance (IMR) offers improved diagnostic capabilities. This study aimed to present early real-world experience with invasive hemodynamic assessment of the coronary microvasculature in symptomatic patients with nonobstructive coronary artery disease (CAD) from the Coronary Microvascular Disease Registry, which is a prospective, multi-center registry that standardized the evaluation of patients with angina and nonobstructive CAD who underwent invasive hemodynamic assessment of the coronary microvasculature using the Coroventis CoroFlow Cardiovascular System. All patients underwent comprehensive invasive hemodynamic assessment. Analysis was performed on the first 154 patients enrolled in the Coronary Microvascular Disease Registry; their mean age was 62.4 years and 65.6% were female. A notable proportion of patients (31.8%) presented with a Canadian Cardiovascular Society Angina Score of 3 or 4. Coronary microvascular dysfunction was diagnosed in 39 of 154 patients (25.3%), with mean fractional flow reserve of 0.89 ± 0.43, mean resting full cycle ratio of 0.93 ± 0.08, mean CFR of 1.8 ± 0.9, and mean IMR of 36.26 ± 19.23. No in-hospital adverse events were reported in the patients. This study demonstrates the potential of invasive hemodynamic assessment using CFR and IMR to accurately evaluate the coronary microvasculature in patients with nonobstructive CAD. These findings have important implications for improving the diagnosis and management of coronary microvascular dysfunction, leading to more targeted and effective therapies for patients with microvascular angina.

The Relationship between Coronary Flow Reserve and the TyG Index in Patients with Gestational Diabetes Mellitus

Background and Objectives: Gestational diabetes mellitus (GDM) is a prevalent metabolic disorder characterized by glucose intolerance during pregnancy. The triglyceride glucose (TyG) index, a marker of insulin resistance, and coronary flow reserve (CFR), a measure of coronary microvascular function, are emerging as potential indicators of cardiovascular risk. This study aims to investigate the association between CFR and the TyG index in GDM patients. Materials and Methods: This cross-sectional study of 87 GDM patients and 36 healthy controls was conducted. The participants underwent clinical assessments, blood tests, and echocardiographic evaluations. The TyG index was calculated as ln(triglycerides × fasting glucose/2). CFR was measured using Doppler echocardiography during rest and hyperemia induced by dipyridamole. Results: The study included 87 individuals in the GDM group and 36 individuals in the control group. There was no significant difference in age between the two groups (34.1 ± 5.3 years for GDM vs. 33.1 ± 4.9 years for the control, p = 0.364). The TyG index was significantly higher in the GDM group compared to the controls (p < 0.001). CFR was lower in the GDM group (p < 0.001). A negative correlation between the TyG index and CFR was observed (r = -0.624, p < 0.001). Linear regression revealed the TyG index as an independent predictor of reduced CFR. Conclusions: The study findings reveal a significant association between the TyG index and CFR in GDM patients, suggesting their potential role in assessing cardiovascular risk.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 1

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of evidence that has led to major recommendations in clinical practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region based on updated information in the field that including both wire- and image-based physiologic assessment. This is Part 1 of the whole consensus document, which describes the general concept of coronary physiology, as well as practical information on the clinical application of physiologic indices and novel image-based physiologic assessment.

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.

Ischemia With Nonobstructive Coronary Artery Disease: Concept, Assessment, and Management

In daily clinical practice, physicians often encounter patients with angina or those with evidence of myocardial ischemia from noninvasive tests but not having obstructive coronary artery disease. This type of ischemic heart disease is referred to as ischemia with nonobstructive coronary arteries (INOCA). INOCA patients often suffer from recurrent chest pain without adequate management and are associated with poor clinical outcomes. There are several endotypes of INOCA, and each endotype should be treated based on its specific underlying mechanism. Therefore, identifying INOCA and discriminating its underlying mechanisms are important issues and of clinical interest. Invasive physiologic assessment is the first step in the diagnosis of INOCA and discriminating the underlying mechanism; additional provocation tests help physicians identify the vasospastic component in INOCA patients. Comprehensive information acquired from these invasive tests can provide a template for mechanism-specific management for patients with INOCA.

Invasive evaluation of coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is a prevalent cause of ischemic heart disease and is associated with poorer quality of life and worse patient outcomes. Both functional and structural abnormalities of the microcirculation can generate ischemia in the absence of epicardial stenosis or worsen concomitant obstructive coronary artery disease (CAD). The invasive assessment of CMD allows for the evaluation of the entirety of the coronary vascular tree, from the large epicardial vessels to the microcirculation, and enables the study of vasomotor function through vasoreactivity testing. The standard evaluation of CMD includes vasomotor assessment with acetylcholine, as well as flow- and resistance-derived indices calculated with either thermodilution or Doppler guidewires. Tailored treatment based upon the information gathered from the invasive evaluation of CMD has been demonstrated to reduce the burden of angina; therefore, a thorough understanding of these procedures is warranted with the aim of improving the quality of life of the patient. This review summarizes the most widespread approaches for the invasive evaluation of CMD, with a focus on patients with ischemia and non-obstructive CAD.

Coronary flow reserve and cardiovascular outcomes: a systematic review and meta-analysis

AIMS

This meta-analysis aims to quantify the association of reduced coronary flow with all-cause mortality and major adverse cardiovascular events (MACE) across a broad range of patient groups and pathologies.

METHODS AND RESULTS

We systematically identified all studies between 1 January 2000 and 1 August 2020, where coronary flow was measured and clinical outcomes were reported. The endpoints were all-cause mortality and MACE. Estimates of effect were calculated from published hazard ratios (HRs) using a random-effects model. Seventy-nine studies with a total of 59 740 subjects were included. Abnormal coronary flow reserve (CFR) was associated with a higher incidence of all-cause mortality [HR: 3.78, 95% confidence interval (CI): 2.39-5.97] and a higher incidence of MACE (HR 3.42, 95% CI: 2.92-3.99). Each 0.1 unit reduction in CFR was associated with a proportional increase in mortality (per 0.1 CFR unit HR: 1.16, 95% CI: 1.04-1.29) and MACE (per 0.1 CFR unit HR: 1.08, 95% CI: 1.04-1.11). In patients with isolated coronary microvascular dysfunction, an abnormal CFR was associated with a higher incidence of mortality (HR: 5.44, 95% CI: 3.78-7.83) and MACE (HR: 3.56, 95% CI: 2.14-5.90). Abnormal CFR was also associated with a higher incidence of MACE in patients with acute coronary syndromes (HR: 3.76, 95% CI: 2.35-6.00), heart failure (HR: 6.38, 95% CI: 1.95-20.90), heart transplant (HR: 3.32, 95% CI: 2.34-4.71), and diabetes mellitus (HR: 7.47, 95% CI: 3.37-16.55).

CONCLUSION

Reduced coronary flow is strongly associated with increased risk of all-cause mortality and MACE across a wide range of pathological processes. This finding supports recent recommendations that coronary flow should be measured more routinely in clinical practice, to target aggressive vascular risk modification for individuals at higher risk.

Prognostic value of comprehensive intracoronary physiology assessment early after heart transplantation

AIMS

We evaluated the long-term prognostic value of invasively assessing coronary physiology after heart transplantation in a large multicentre registry.

METHODS AND RESULTS

Comprehensive intracoronary physiology assessment measuring fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) was performed in 254 patients at baseline (a median of 7.2 weeks) and in 240 patients at 1 year after transplantation (199 patients had both baseline and 1-year measurement). Patients were classified into those with normal physiology, reduced FFR (FFR ≤ 0.80), and microvascular dysfunction (either IMR ≥ 25 or CFR ≤ 2.0 with FFR > 0.80). The primary outcome was the composite of death or re-transplantation at 10 years. At baseline, 5.5% had reduced FFR; 36.6% had microvascular dysfunction. Baseline reduced FFR [adjusted hazard ratio (aHR) 2.33, 95% confidence interval (CI) 0.88-6.15; P = 0.088] and microvascular dysfunction (aHR 0.88, 95% CI 0.44-1.79; P = 0.73) were not predictors of death and re-transplantation at 10 years. At 1 year, 5.0% had reduced FFR; 23.8% had microvascular dysfunction. One-year reduced FFR (aHR 2.98, 95% CI 1.13-7.87; P = 0.028) and microvascular dysfunction (aHR 2.33, 95% CI 1.19-4.59; P = 0.015) were associated with significantly increased risk of death or re-transplantation at 10 years. Invasive measures of coronary physiology improved the prognostic performance of clinical variables (χ2 improvement: 7.41, P = 0.006). However, intravascular ultrasound-derived changes in maximal intimal thickness were not predictive of outcomes.

CONCLUSION

Abnormal coronary physiology 1 year after heart transplantation was common and was a significant predictor of death or re-transplantation at 10 years.