Association between patient age, microcirculation, and coronary stenosis assessment with fractional flow reserve and instantaneous wave‐free ratio

Prognostic role of con-/discordant coronary flow reserve and microvascular resistance in coronary microvascular disease: a systematic review and network meta-analysis

BACKGROUND

Coronary microvascular disease (CMD) is defined as impaired coronary flow reserve (CFR) and/or increased microvascular resistance (MR) without significant epicardial coronary stenosis. This definition allows for discordant CFR and MR values within patients with CMD. The aim of this meta-analysis is to characterise the prognostic value and pathophysiological backgrounds of CFR and MR con-/discordance.

METHODS

A systematic search (PROSPERO CRD42024573004) identified studies determining CFR and MR in patients without significant epicardial coronary artery disease. Patients were divided into four groups: (1) normal CFR and MR, (2) abnormal CFR and MR, (3) abnormal CFR with normal MR and (4) normal CFR with abnormal MR and analysed for all-cause mortality and major adverse cardiovascular events (MACE).

RESULTS

We identified four studies representing 2310 total participants. Group B had the highest MACE (OR: 3.23; 95% CI 1.95 to 5.36) and mortality rate (OR: 2.27; 95% CI 1.12 to 4.58) compared with group A. Group C, associated with female sex, showed significantly higher MACE (OR: 2.07; 95% CI 1.25 to 3.45) but not mortality (OR: 1.89; 95% CI 0.92 to 3.88) compared with group A. In group D, associated with high body mass index, MACE and mortality rates did not differ significantly from group A (OR: 1.19; 95% CI 0.67 to 2.11 and OR: 0.55; 95% CI 0.16 to 1.90, respectively).

CONCLUSIONS

Abnormal CFR and MR are associated with a high risk of MACE and death. Abnormal CFR and normal MR are associated with an increased MACE-but not death. MACE and mortality risk in discordantly normal CFR and abnormal MR are low. Our findings show the need for tailoring CFR and MR diagnostic thresholds to patient characteristics and raise questions about the presence of CMD in patients with abnormal MR with normal CFR.

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.

Age-related structural remodelling of the coronary circulation

BACKGROUND

While it is broadly accepted that ageing is associated with impairment of coronary microvascular function, little is known about the underlying mechanisms.

AIMS

We investigated age-related changes in coronary microvascular structure in patients with stable angina without epicardial coronary stenoses.

METHODS

In an analysis of the IDEAL registry, a total of 165 vessels without coronary stenosis were interrogated with combined pressure/Doppler guidewires. We calculated diastolic microvascular conductance (DMVC) and backward expansion wave (BEW), and compared them between age tertiles. We calculated the prevalence of CMD, defined by reduced coronary flow reserve (CFR), and the prevalence of low BEW and low DMVC in each group.

RESULTS

The three study groups were defined as having 37-53, 54-66, and 67-77 years of age, respectively. Oldest (3rd tertile) patients showed lower hyperemic flow velocity (46.7 ± 14.4 vs. 45.1 ± 12.4 vs. 38.4 ± 11.5 cm s-1, p = 0.019), lower DMVC (1.90 ± 0.71 vs. 1.44 ± 0.56 vs. 1.37 ± 0.67 cm s-1 mmHg-1, p < 0.001) and lower BEW intensity (5.9 [2.9-8.4] vs. 4.8 [2.9-6.8] vs. 4.4 [3.4-6.3] × 106 W m-2 s-1, p = 0.094). Older age was independently associated with lower BEW intensity (B: -0.10, 95% confidence interval [CI]: -0.17 to -0.09, p = 0.021) and DMVC (B: -0.25 95% CI: -0.45 to -0.09, p = 0.027). In patients with CFR < 2.5, the prevalence of BEW intensity and DMVC below the 25th percentile increased with age (25.0% vs. 52.0% vs. 72.7%, p = 0.010).

CONCLUSIONS

Ageing is independently associated with structural microcirculatory remodeling that is reflected in BEW intensity and DMVC measurements, and with an increased prevalence of structural CMD. These results are important to understand non-obstructive mechanisms of myocardial ischemia in the elderly.

The Importance of Integrated Regulation Mechanism of Coronary Microvascular Function for Maintaining the Stability of Coronary Microcirculation: An Easily Overlooked Perspective

Coronary microvascular dysfunction (CMD) refers to a group of disorders affecting the structure and function of coronary microcirculation and is associated with an increased risk of major adverse cardiovascular events. At present, great progress has been made in the diagnosis of CMD, but there is no specific treatment for it because of the complexity of CMD pathogenesis. Vascular dysfunction is one of the important causes of CMD, but previous reviews mostly considered microvascular dysfunction as a whole abnormality so the obtained conclusions are skewed. The coronary microvascular function is co-regulated by multiple mechanisms, and the mechanisms by which microvessels of different luminal diameters are regulated vary. The main purpose of this review is to revisit the mechanisms by which coronary microvessels at different diameters regulate coronary microcirculation through integrated sequential activation and briefly discuss the pathogenesis, diagnosis, and treatment progress of CMD from this perspective.

Factors Predicting 150 and 200 Microgram Adenosine Requirement during Four Increasing Doses of Intracoronary Adenosine Bolus Fractional Flow Reserve Assessment

Direct intracoronary adenosine bolus is an excellent alternative to intravenous adenosine fractional flow reserve (FFR) measurement. This study, during four increasing adenosine boluses (50, 100, 150, and 200 mcg), aimed to explore clinical and angiographic predictors of coronary stenotic lesions for which the significant ischemic FFR (FFR ≤ 0.8) occurred at 150 and 200 mcg adenosine doses. Data from 1055 coronary lesions that underwent FFR measurement at the Central Chest Institute of Thailand from August 2011 to July 2021 were included. Baseline clinical and angiographic characteristics were analyzed. The FFR ≤ 0.8 occurred at adenosine 150 and 200 mcg boluses in 47 coronary lesions, while the FFR ≤ 0.8 occurred at adenosine 50 and 100 mcg boluses in 186 coronary lesions. After univariable and multivariable logistic regression analyses, four characteristics, including male sex, younger age, non-smoking status, and FFR procedure of RCA, were predictors of the occurrence of FFR ≤ 0.8 at adenosine 150 and 200 mcg doses. Combining all four predictors as a predictive model resulted in an AuROC of 0.72 (95% CI: 0.68–0.76), an 86% negative predictive value. Comparing these four predictors, the FFR procedure of RCA gave the most predictive power, with the AuROC of 0.60 (95% CI: 0.56–0.63).