The Impact of Microvascular Resistance Reserve on the Outcome of Patients With STEMI

The prognostic role of microvascular resistance reserve: A systematic review and meta-analysis

INTRODUCTION

Microvascular resistance reserve (MRR) is a novel indice for coronary microcirculation assessment, addressing limitations of coronary flow reserve (CFR) and index of microcirculatory resistance (IMR). Given its promising role in the future of coronary microvascular dysfunction assessment, we aimed to systematically review and meta-analyze available studies reporting its prognostic significance.

METHODS

We performed a systematic search in 3 different databases (MEDLINE/PubMed, Web of Science and Scopus). After selecting all appropriate studies according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a random effect meta-analysis was performed.

RESULTS

Our analysis, including 5 studies and a total of 1605 (453 abnormal MRR; 1152 normal MRR) patients, shows that patients with abnormal MRR are at significantly higher risk for cardiovascular death [Risk Ratio (RR): 4.88 95 % Confidence Interval (CI): 3.49-6.83], major adverse cardiovascular events (RR: 2.37; 95%CI: 1.52-3.70), myocardial infarction (RR: 1.93; 95%CI: 1.53-2.42) and heart failure hospitalizations (RR: 4.83; 95%CI: 1.59-14.70), in comparison to the normal MRR cohort. As expected, abnormal MRR was not associated with a significantly higher risk of future revascularizations, compared to normal controls (RR: 1.29; 95%CI: 0.52-3.19).

CONCLUSION

This study shows the significant microcirculation-specific prognostic effect of MRR in both survival and adverse outcomes. Further data from large randomized studies, will delineate the clinical utility and prognostic effect of MRR in coronary microvascular dysfunction.

Phenotyping the Use of Cangrelor in Percutaneous Coronary Interventions

The use of antiplatelet agents is essential in percutaneous coronary interventions, both periprocedurally and in the post-interventional period. Procedural antiplatelet therapy, aiming to limit ischemic complications, is mostly administered with oral agents, including aspirin and P2Y12 inhibitors. However, there are several limitations in the use of oral P2Y12 inhibitors, including their difficult administration in patients presenting with cardiogenic shock and their relatively slower onset of action, leaving a significant period of the procedure with a suboptimal antiplatelet effect. These pitfalls could be avoided with the use of cangrelor, the only available intravenous P2Y12 inhibitor, which has a rapid onset and offset antiplatelet effect, as well as a favorable pharmacological profile. The use of cangrelor has been increasing in recent years, with several studies aiming to determine what the optimal patient phenotype to receive such treatment ultimately is and how its use could be adjunctive to oral P2Y12 inhibitors. Therefore, the aim of this review is to provide an overview of the pharmacological profile of cangrelor and an update regarding the clinical evidence supporting its use, as well as to discuss the optimal patient phenotype, related clinical algorithms, and future implications for larger implementation of this agent into everyday clinical practice.

Angiography-Derived Fractional Flow Reserve: Newer Data and Future Directions

Several novel software systems have been developed for the reconstruction of the coronary artery tree and the calculation of fractional flow reserve (FFR) from coronary artery angiography images without coronary artery instrumentation: FFRangio, Computational pressure-flow dynamics derived FFR, quantitative flow ratio (QFR), and vessel FFR. In this report, we review the current evidence on each software, their contemporary use, and future directions.

Microvascular resistance reserve: impact on health status and myocardial perfusion after revascularization in chronic coronary syndrome

BACKGROUND AND AIMS

The microvascular resistance reserve (MRR) is a novel invasive index of the microcirculation, which is independent of epicardial stenoses, and has both diagnostic and prognostic implications. This study investigates whether MRR is associated with health status outcomes by revascularization in patients with moderate coronary stenoses.

METHODS

Consecutive patients with stable chest pain and moderate (30%-90% diameter) stenoses on invasive coronary angiography (n = 222) underwent invasive physiology assessment. Revascularization was performed according to guideline recommendations. At baseline and follow-up, health status and myocardial perfusion were assessed by the Seattle Angina Questionnaire (SAQ) and positron emission tomography. The primary endpoint was freedom from angina at follow-up with secondary endpoints including changes in health status by SAQ domains and myocardial perfusion by MRR and revascularization status. Low MRR was defined as ≤3.0.

RESULTS

Freedom from angina occurred in 38/173 patients. In multivariate analyses, MRR was associated with freedom from angina at follow-up (odds ratio 0.860, 95% confidence interval 0.740-0.987). By MRR and revascularization groups, patients with normal MRR who did not undergo revascularization, and patients with abnormal MRR who underwent revascularization, had improved health status of angina frequency [mean difference SAQ angina frequency score 8.5 (3.07-13.11) and 13.5 (2.82-23.16), respectively]. For both groups, health status of physical limitation [mean difference in SAQ physical limitation score 9.7 (4.79-11.93) and 8.7 (0.53-13.88), respectively] and general health status [mean difference in SAQ summary score 9.3 (5.18-12.50) and 10.8 (2.51-17.28), respectively] also improved. Only patients with abnormal MRR who underwent revascularization had improved myocardial perfusion.

CONCLUSIONS

In patients with moderate coronary stenoses, MRR seems to predict the symptomatic and perfusion benefit of revascularization.

CLINICAL TRIAL IDENTIFIERS

NCT03481712 and NCT04707859.

ANOCA updated: From pathophysiology to modern clinical practice

Lately, a large number of stable ischemic patients, with no obstructed coronary arteries are being diagnosed. Despite this condition, which is being described as angina with no obstructive coronary arteries (ANOCA), was thought to be benign, recent evidence report that it is associated with increased risk for adverse cardiovascular outcomes. ANOCA is more frequent in women and, pathophysiologically, it is predominantly related with microvascular dysfunction, while other factors, such as endothelial dysfunction, inflammation and autonomic nervous system seem to also play a major role to its development, while other studies implicate ANOCA and microvascular dysfunction in the pathogenesis of heart failure with preserved ejection fraction. For establishing an ANOCA diagnosis, measurement including coronary flow reserve (CFR), microvascular resistance (IMR) and hyperemic microvascular resistance (HMR) are mostly used in clinical practice. In addition, new modalities, such as optical coherence tomography (OCT) are being tested and show promising results for future diagnostic use. Regarding management, pharmacotherapy consists of a wide selection of drugs, according to the respected pathophysiology of the disease (vasospastic angina or microvascular dysfunction), while research for new treatment options including interventional techniques, is currently ongoing. This review, therefore, aims to provide a comprehensive analysis of all aspects related to ANOCA, from pathophysiology to clinical managements, as well as clinical implications and suggestions for future research efforts, which will help advance our understanding of the syndrome and establish more, evidence-based, therapies.