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

Invasive coronary function testing in clinical practice: Implementing the 2024 ESC guidelines on chronic coronary syndromes

Angina with non-obstructive coronary arteries (ANOCA) is increasingly recognized as a significant aspect of chronic coronary syndromes. These patients frequently experience recurrent angina, resulting in high healthcare costs and impaired quality of life. Invasive coronary function testing (ICFT) is able to identify ANOCA endotypes, which can guide treatment and improve quality of life. Despite Class II recommendations for invasive microvascular assessments in the previous 2019 European Society of Cardiology (ESC) Guidelines, ICFT has yet to translate into widespread clinical practice. Patients with ANOCA experience poor quality of life and reduced functional capacity, highlighting the need for earlier ICFT implementation. The 2024 ESC Guidelines now strongly recommend ICFT (Class I, level of evidence B) for patients with non-obstructive coronary arteries and persistent angina despite optimal medical therapy, and for confirming or excluding ANOCA in patients with uncertain diagnoses on non-invasive testing (Class I, level of evidence B). Consequently, a standardized approach to optimize the management of ANOCA patients is warranted. Therefore, this review aims to provide interventional cardiologists with a contemporary review of the literature and a practical guideline on implementation of ICFT. It will discuss the following subjects: the definitions of the different endotypes, an example of an ICFT protocol, discontinuation of medication prior to ICFT, use of radial cocktail, target vessel for testing, acetylcholine injection techniques and rechallenge, adenosine injection techniques, the order of testing, the interpretation of ICFT, safety and feasibility, and the pharmacological treatment.

Clinical standards in angina and non-obstructive coronary arteries: A clinician and patient consensus statement

Patients with angina and non-obstructive coronary arteries (ANOCA) or myocardial ischaemia with non-obstructive coronary arteries (INOCA) comprise a relatively large subgroup within those with ischaemic heart disease. Advances in the understanding of disease mechanisms, diagnostic tests and multidisciplinary care are improving awareness of the needs of affected individuals. However, practice variations and suboptimal management promulgate the health burden and increase health care resource consumption. Clinical standards represent a limited number of quality statements that describe the care patients should be offered by health professionals and providers for a specific clinical condition or defined clinical pathway in line with current best evidence. Clinical standards should address implementation of this evidence along with education of patients and healthcare professionals, multidisciplinary care networks, and research. In this consensus statement, we highlight contemporary evidence and stakeholder views, including clinicians and patients, to provide an international perspective for developing clinical standards for services involving ANOCA/INOCA patients. A clinical service for ANOCA/INOCA should "consider the whole patient" and provide a multidisciplinary, patient-centred service.

Coronary microvascular dysfunction and its role in heart failure with preserved ejection fraction for future prevention and treatment

Ischemic heart disease has long been established as the leading cause of heart failure, typically as a result of hemodynamically significant and obstructive coronary anatomy. Since, the role of dysfunctional coronary microvascular pathophysiologic mechanisms have also been associated with the development of congestive heart failure (CHF), most notably heart failure with preserved ejection fraction (HFpEF) although with limited clinical evidence. Conventional cardiometabolic and behavioral risk factors common to HFpEF such as diabetes mellitus (DM), obesity, hypertension, dyslipidemia, smoking, and chronic kidney disease foster a pro-inflammatory environment conducive to endothelial dysfunction and improper regulation of vasoactive substances. The impaired relaxation and increased vasoconstriction of damaged endothelium gives rise to impaired coronary blood flow and episodes of transient ischemia. Such coronary microvascular dysfunction (CMD) has its own implication on cardiovascular pathophysiologic mechanisms beyond symptomatic coronary and myocardial ischemia, and thus its own potential prevention goals and treatment targets for patients with HFpEF, where previous management had been limited. As such, we conducted a literature review to address the current landscape of data which links CMD to HFpEF. Furthermore, we considered the implications of biopsychosocial elements such as race, ethnicity, sex, gender, and the social determinants of health as they relate to the disparate health outcomes of those most at risk for CMD and HFpEF.

Gout and rheumatoid arthritis are associated with subclinical vascular damage, reduced brachial vasoreactivity and coronary microvascular dysfunction: a case-control study

Gout and rheumatoid arthritis (RA) are distinct disorders, but both of these inflammatory arthropaties are associated with a relatively similar risk of atherosclerotic cardiovascular disease. We aimed to assess carotid intima-media thickness (CIMT), flow-mediated vasodilatation (FMD) and coronary flow reserve (CFR) in both disorders to understand and compare the extent of vascular damage. Patients with recently diagnosed gout (n = 30) and RA (n = 40) without previous cardiovascular disease were included to the present study, and 45 healthy volunteers served as controls. All participants underwent ultrasonographic examinations to measure CIMT, FMD and CFR. In unadjusted analysis, both gout and RA were associated with a significantly higher CIMT and significantly lower CFR as compared to controls, while FMD was only lower in the gout group. After adjustment, there was a significantly higher odds ratio (OR) for CIMT (OR:7.02, 95%CI:2.45-20.58 for gout and OR:2.86, 95%CI:1.27-6.57 for RA) and a lower OR for CFR (OR:0.21, 95%CI:0.08-0.55 for gout and OR:0.17, 95%CI:0.07-0.45 for RA) in both groups, while only gout patients had a lower OR for FMD (OR:0.21, 95%CI:0.08-0.55). There were no significant differences or evidence of a difference between gout and RA patients for CIMT, FMD or CFR. Gout and RA are associated with a similar degree of vascular damage, which may explain the similar incidence of atherosclerotic cardiovascular disease in both diseases.

Sex differences in myocardial flow reserve among individuals with type 2 diabetes: insights from the DiaHeart study

BACKGROUND

Type 2 diabetes is a stronger risk factor for cardiovascular disease (CVD) in women compared with men possibly due to higher susceptibility to develop myocardial microvascular dysfunction. We investigated sex-dependent effects of risk factors on myocardial blood flow (MBF) and myocardial flow reserve (MFR) in individuals with type 2 diabetes without overt CVD.

METHODS

Cross-sectional analysis of a prospective study including 901 individuals recruited between 2020 and 2023. All participants underwent a cardiac 82-Rubidium positron emission tomography/computed tomography scan to quantify MBF at rest and during pharmacologically induced stress, allowing for calculation of MFR. Linear regression, with/without interaction terms for sex, was used to test whether sex modified the association between MFR/MBF and risk factors.

RESULTS

Mean (SD) age was 65 (8.9) years, diabetes duration was 14 (8.4) years, and 266 (29.5%) were women. Women had higher MBF at rest and stress but had lower MFR (mean (SD) 2.44 (0.67) vs. 2.59 (0.77), p = 0.003) than men. A similar proportion of men and women (21.1% vs. 23.7%) had an MFR < 2. The decline in predicted MFR with age differed between sexes. At age 55, women had a mean MFR that was 0.29 lower than men (95% CI: - 0.44 to - 0.14), but by age 75, this difference had nearly disappeared (- 0.04, 95% CI: - 0.19 to 0.11). However, after adjustment for other risk factors, the interaction between sex and age was not statistically significant (p = 0.057). No other risk factors exhibited significant sex-dependent interactions.

CONCLUSIONS

In individuals with type 2 diabetes without overt CVD, women exhibited lower MFR than men, primarily due to higher MBF at rest, suggesting sex-related differences. While MFR declined in both sexes, the sex difference was more pronounced in younger individuals and diminished over time. These findings underscore the need for further research into sex-specific thresholds for MFR in cardiovascular risk stratification.

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.

The Novel A-Flux Coronary Sinus Reducer Normalizes Coronary Microvascular Function in a Persistently Symptomatic Patient

Coronary microvascular dysfunction (CMD) contributes to persistent angina/anginal equivalent symptoms and is associated with adverse outcomes. Coronary sinus reduction (CSR) is a device-based therapy with the potential to improve outcomes by reducing symptom burden and improving coronary flow reserve. A patient with CMD underwent CSR with the next-generation A-Flux device.

Clinical Significance of Coronary Flow Reserve Improvement After Elective Percutaneous Coronary Intervention

BACKGROUND

Limited research has explored the prognostic significance of changes in coronary flow velocity reserve (CFVR), as measured by stress-transthoracic Doppler echocardiography (S-TDE), following elective percutaneous coronary intervention (PCI). This study aimed to assess whether post-PCI changes in CFVR are associated with major adverse cardiac events (MACE) and to identify baseline clinical factors that predict improvement of CFVR.

METHODS

A retrospective analysis was performed on 184 patients who underwent elective FFR-guided PCI for the left anterior descending (LAD) artery. Standard pre-PCI TDE examinations and pre- and post-PCI physiological assessments using S-TDE were performed. Patients were categorized based on CFVR improvement, defined as an increase greater than the median value of CFVR changes. MACE, including all-cause death, myocardial infarction, ischemic stroke, and heart failure requiring hospitalization, was evaluated.

RESULTS

The median improvement in CFVR was 0.50 (28.8%). During a median follow-up period of 1.9 years, MACE occurred in 26 patients (14.1%). Patients without CFVR improvement had significantly worse outcomes (p = 0.029). In multivariate Cox regression analysis, both lower pre-PCI CFVR and lack of CFVR improvement were associated with poor prognosis. A multivariate logistic regression analysis identified absence of diabetes, lower pre-PCI FFR, lower pre-PCI CFVR, and longer pre-PCI deceleration time of diastolic coronary flow as predictors of CFVR increase, with an AUC of 0.814 (95% CI: 0.755-0.873).

CONCLUSIONS

In patients undergoing elective FFR-guided LAD PCI, a lower pre-PCI CFVR and lack of CFVR improvement were associated with poor prognosis, whereas a comprehensive pre-PCI evaluation predicted CFVR improvement.

Rationale and design of the ILIAS ANOCA clinical trial: A blinded-arm controlled trial for routine ad-hoc coronary function testing

BACKGROUND

Angina with nonobstructive coronary arteries (ANOCA) is a major cause of chronic coronary syndromes, affecting nearly half of patients with anginal symptoms who undergo invasive coronary angiography. ANOCA may lead to substantial symptom burden, increased risk of adverse cardiac events, increased healthcare utilization due to ongoing symptoms, repeat hospitalizations, and invasive testing. The pathophysiology of ANOCA often involves a variety of coronary disorders, such as coronary microvascular dysfunction, epicardial or microvascular vasospasm and endothelial dysfunction. While coronary function testing (CFT) can identify each of these specific endotypes, in current practice it is used as a second- or third-line diagnostic tool, delaying diagnosis which contributes to persistent symptoms and diminished quality of life. The ILIAS ANOCA clinical trial aims to enhance understanding and management of ANOCA through early routine CFT-guided management.

METHODS

After exclusion of obstructive coronary artery disease, eligible patients undergo comprehensive CFT, and will be randomized to blinding of the CFT results (control group) or disclosure of the CFT results combined with a tailored medical therapy escalation plan (intervention group). The control group will be unblinded after 1 year. The primary outcome is the mean difference in the within-subject change in Seattle Angina Questionnaire (SAQ) summary score between the groups at 6 months from baseline. Secondary outcomes include differences in SAQ-summary score and additional health-status and quality of life questionnaires at 12 and 24 months from baseline.

CLINICAL TRIAL REGISTRATION

International Clinical Trials Registry Platform identifier NL-OMON20739.

Emerging Applications of Positron Emission Tomography in Coronary Artery Disease

Coronary artery disease remains the leading cause of morbidity and mortality worldwide. With the changing clinical manifestation and novel therapeutical options, precise disease phenotyping becomes increasingly important at the point of care. In the management of coronary artery disease, myocardial perfusion imaging (MPI) remains the cornerstone of clinical practice. Although traditionally MPI has been primarily performed with single photon emission computed tomography (SPECT), nowadays, given the changing spectrum of the disease, greater precision and additional assessment of myocardial blood flow are desired. Due to the fundamental advantages of PET over SPECT, i.e., higher spatial resolution, accurate attenuation correction for each scan, and higher count rates, the sensitivity and specificity of PET MPI are higher than those of SPECT MPI and are estimated to be approximately 90-92% vs. 83-88% and 81-87% vs. 70-76%, respectively, according to meta-analysis data. Consequently, over the past decade, we have witnessed an increased uptake of positron emission tomography (PET) MPI. With the improved spatial resolution, the ability to quantify myocardial blood flow, and the potential to depict the burden of coronary atherosclerosis with low-dose computed tomography, PET/CT is uniquely positioned to facilitate a comprehensive non-invasive assessment of disease, providing an opportunity for precision medicine. The wealth of data obtained during a single imaging session can be challenging to integrate at the time of image analysis. There has therefore been an increasing interest in developing predefined thresholds or variables (scores) which combine the multidimensional data acquired with PET MPI. Beyond MPI, PET can also serve for the assessment of disease activity at the atherosclerotic plaque level, further refining our understanding of the biology of coronary artery disease and providing hope for enhanced prediction of myocardial infarctions. In this narrative review, we present the current applications of PET MPI in coronary artery disease and focus specifically on two areas that have recently garnered considerable interest-the integration of multiparametric PET MPI data and coronary plaque activity PET imaging.

Eclipsed mitral regurgitation and the role of multimodality imaging: a case report

Background

Eclipsed mitral regurgitation (MR) is a rare, reversible condition that leads to transient severe MR and acute heart failure in patients with preserved left ventricular (LV) ejection fraction. Its diagnosis is challenging due to its intermittent presentation, necessitating advanced imaging techniques to reveal the underlying pathology.

Case summary

We present a case of a 74-year-old female with recurrent severe MR associated with a non-obstructive lesion in the proximal left anterior descending (LAD) artery. Multimodality imaging played a pivotal role in diagnosing this condition, as conventional vasodilator stress tests failed to uncover the ischaemic mechanism. Exercise stress echocardiography and myocardial perfusion scintigraphy successfully demonstrated a small ischaemic region affecting the mitral valve apparatus, which triggered severe MR during physical exertion. This dynamic ischaemia, undetected by routine tests, was essential in diagnosing the pathophysiology behind the patient's recurrent MR. Following percutaneous coronary intervention (PCI) to the LAD, her symptoms resolved, confirming the ischaemic origin of the MR.

Discussion

This case underscores the critical role of multimodality imaging in revealing the pathophysiology of recurrent MR. Advanced imaging techniques, particularly under physiologic stress, are crucial for diagnosing dynamic ischaemia and its impact on valvular function. By identifying the ischaemic cause of MR, individualized treatment strategies, such as PCI, can be implemented, avoiding unnecessary valve surgery and improving patient outcomes.

Translational regulation of SND1 governs endothelial homeostasis during stress

Translational control shapes the proteome and is particularly important in regulating gene expression under stress. A key source of endothelial stress is treatment with tyrosine kinase inhibitors (TKIs), which lowers cancer mortality but increases cardiovascular mortality. Using a human induced pluripotent stem cell-derived endothelial cell (hiPSC-EC) model of sunitinib-induced vascular dysfunction combined with ribosome profiling, we assessed the role of translational control in hiPSC-ECs in response to stress. We identified staphylococcal nuclease and tudor domain-containing protein 1 (SND1) as a sunitinib-dependent translationally repressed gene. SND1 translational repression was mediated by the mTORC1/4E-BP1 pathway. SND1 inhibition led to endothelial dysfunction, whereas SND1 OE protected against sunitinib-induced endothelial dysfunction. Mechanistically, SND1 transcriptionally regulated UBE2N, an E2-conjugating enzyme that mediates K63-linked ubiquitination. UBE2N along with the E3 ligases RNF8 and RNF168 regulated the DNA damage repair response pathway to mitigate the deleterious effects of sunitinib. In silico analysis of FDA-approved drugs led to the identification of an ACE inhibitor, ramipril, that protected against sunitinib-induced vascular dysfunction in vitro and in vivo, all while preserving the efficacy of cancer therapy. Our study established a central role for translational control of SND1 in sunitinib-induced endothelial dysfunction that could potentially be therapeutically targeted to reduce sunitinib-induced vascular toxicity.

Clinical implications of coronary microvascular dysfunction in patients with non-obstructive coronary artery disease and role of the thermodilution method

More than 60% of patients undergoing coronary angiography present no coronary artery disease (CAD). Angina and myocardial ischemia are classically determined by epicardial vascular obstruction, but coronary microvascular dysfunction (CMD) may also represent a possible cause for these phenomena. Two endotypes of CMD have been recognized, with two different pathophysiological mechanisms: structural CMD, characterized by low coronary flow reserve (CFR) and high microvascular resistance (MVR) values; and functional CMD, characterized by low CFR and normal MVR values. According to the present data, almost half of patients with non-obstructive CAD have shown signs of CMD. For this reason, further investigations for microvascular function assessment should be considered when evaluating no-CAD patients complaining of angina or presenting signs of myocardial ischemia. The thermodilution method is currently becoming a widespread invasive technique due to its feasibility and high reproducibility for coronary physiology evaluation. Furthermore, a recently introduced technique - called continuous thermodilution - allows for direct measurement of absolute coronary flow and resistances. The role of this brand-new technique in the clinical scenario is however still to be fully investigated and its use is at present limited to research purposes only. Among no-CAD patients, both structural and functional CMD are related to a worse prognosis in term of mortality and major adverse cardiovascular events (MACE). In this review, we will discuss the present evidence supporting the definition, prevalence and clinical implication of the different forms of CMD and the technical aspects of its invasive assessment.

Functional assessment in angina and non-obstructive coronary arteries: from microvascular resistance reserve to subtypes of coronary microvascular dysfunction

AIMS

Coronary microvascular dysfunction (CMD) is a heterogeneous condition defined by reduced coronary flow reserve (CFR). The new index 'microvascular resistance reserve' (MRR) has been developed, but its role is unclear. We investigate the relationships between functional indices in ANOCA (angina and non-obstructive coronary arteries) patients and evaluate the hemodynamic features of different CMD subtypes.

METHODS

We enrolled consecutive ANOCA patients assessed by using the bolus thermodilution technique. CFR, index of microcirculatory resistance (IMR) and MRR were estimated and correlated with each other. Patients were divided into two groups based on CMD presence (CFR < 2.5). Subsequently, high-hyperaemic-resistance (HHR) and low-hyperaemic-resistance (LHR) CMD subtypes were defined according to IMR values (cut-off 25). Microvascular flow and resistance were estimated both at rest and during hyperaemia with Tmnrest/IMRrest and Tmnhyp/IMR, respectively. All functional indices were compared between groups.

RESULTS

In total, 108 patients were enrolled: 66 patients in the normal group (CFR ≥ 2.5), 20 in the HHR-CMD group (CFR < 2.5 and IMR ≥ 25) and 22 in the LHR-CMD group (CFR < 2.5 and IMR < 25). MRR strongly correlated (r = 0.968, P < 0.01) with CFR, showing a good discriminatory power (area under the curve = 0.97) and accuracy (85%) for detecting CMD. LHR-CMD patients showed reduced microvascular resistance (IMRrest 34.3 ± 15.1, P < 0.01) and increased resting flow (Tmnrest 0.37 ± 0.17, P < 0.01), while HHR-CMD patients had impaired hyperaemic flow (Tmnhyp 0.45 ± 0.24 P < 0.01). MRR was reduced in CMD patients (P < 0.01), with no differences between CMD subtypes (P = 0.66).

CONCLUSIONS

In ANOCA patients, MRR and CFR are strongly correlated and could be considered as functionally interchangeable tools. IMR is crucial for differentiating CMD endotypes.

Paroxysmal Atrial Fibrillation during Spasm Provocation Test with Acetylcholine: Clinical Characteristics of Patients and Effect on Coronary Microvascular Function Measurements

BACKGROUND

Atrial fibrillation (AF) is a complication that occurs following a spasm provocation test (SPT) with acetylcholine (ACh). However, the characteristics of patients with AF remain unclear. Furthermore, the association of AF with the outcome of the coronary microvascular function test (CMFT) is unknown. This study aimed to evaluate whether patients with angina with non-obstructive coronary artery disease (ANOCA) who developed AF during SPT with ACh had any clinical characteristics. Additionally, we assessed the association of AF with the CMFT results.

METHODS

We included 123 patients with ANOCA who underwent SPT and CMFT. We defined AF as AF during ACh provocation. The coronary arteries that demonstrated AF before CMFT were defined as AF vessels (n = 21) and those in sinus rhythm (SR) were defined as SR-1 vessels (n = 165). Vessels that were restored to sinus rhythm immediately following AF were defined as AF-SR vessels (n = 29) and those that remained in sinus rhythm for some time were defined as SR-2 vessels (n = 136). Coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) were obtained, and CFR of <2.0 and/or IMR of ≥25 were diagnosed as coronary microvascular dysfunction (CMD).

RESULTS

Of the 123 patients, 31 (25%) had AF but with no characteristic patient background. CFR was significantly lower in AF vessels than in SR-1 vessels (p = 0.035) and IMR did not differ between the two groups (p = 0.918). A study of the three groups that included AF-SR vessels revealed that IMR tended to be lower in AF-SR vessels than in the SR-2 and AF vessels (p = 0.089), and that the frequency of IMR of ≥25 was significantly lower than in the other two groups (p = 0.016).

CONCLUSIONS

AF occurred in 25% of SPTs with ACh, but the predictive clinical context remains unclear. Our results indicated that AF may affect the outcome of the CMFT. Thus, decisions for CMD management should be made with caution in the presence of AF.

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.

Coronary Microvascular Dysfunction: Insights on Prognosis and Future Perspectives

Coronary microvascular dysfunction (CMD) comprises a wide spectrum of structural and/or functional abnormalities of coronary microcirculation that can lead to myocardial ischemia. Emerging evidence has indicated that CMD is a relevant cause of morbidity and mortality and is associated with a high risk of major adverse cardiovascular events (MACEs) and heart failure with preserved ejection fraction as well as poor quality of life. This review aims to elucidate briefly the pathogenesis and diagnostic modalities of CMD and to shed light on contemporary evidence on the prognostic impact of CMD. Finally, we will provide an overview of novel emerging therapeutic strategies for CMD.

Coronary Microvascular Function in Asymptomatic Middle-Aged Individuals With Cardiometabolic Risk Factors

BACKGROUND

In patients with ischemic heart disease, coronary microvascular dysfunction is associated with cardiovascular risk factors and poor prognosis; however, data from healthy individuals are scarce.

OBJECTIVES

The purpose of this study was to assess the impact of cardiovascular risk factors and subclinical atherosclerosis on coronary microvascular function in middle-aged asymptomatic individuals.

METHODS

Myocardial perfusion was measured at rest and under stress using cardiac magnetic resonance in 453 individuals and used to generate myocardial blood flow (MBF) maps and calculate myocardial perfusion reserve (MPR). Subclinical atherosclerosis was assessed using 3-dimensional vascular ultrasound of the carotid and femoral arteries and coronary artery calcium scoring at baseline and at 3-year follow-up.

RESULTS

Median participant age was 52.6 years (range: 48.9-55.8 years), and 84.5% were male. After adjusting for age and sex, rest MBF was directly associated with the number of the metabolic syndrome components present (elevated waist circumference, systolic and diastolic blood pressure, fasting glucose, and triglycerides and low high-density lipoprotein cholesterol), insulin resistance (homeostatic model assessment for insulin resistance), and presence of diabetes. MPR was reduced in the presence of several metabolic syndrome components, elevated homeostatic model assessment for insulin resistance, and diabetes. Stress MBF was inversely associated with coronary artery calcium presence and with global plaque burden. Higher stress MBF and MPR were associated with less atherosclerosis progression (increase in plaque volume) at 3 years.

CONCLUSIONS

In asymptomatic middle-aged individuals free of known cardiovascular disease, the presence of cardiometabolic risk factors and systemic (poly-vascular) subclinical atherosclerosis are associated with impaired coronary microvascular function. Better coronary microvascular function reduces atherosclerosis progression at follow-up. (Progression of Early Subclinical Atherosclerosis [PESA]; NCT01410318).

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.

The role of coronary microcirculation in heart failure with preserved ejection fraction: An unceasing odyssey

Heart failure with preserved ejection fraction (HFpEF) represents an entity with complex pathophysiologic pathways, among which coronary microvascular dysfunction (CMD) is believed to be an important orchestrator. Research in the field of CMD has highlighted impaired vasoreactivity, capillary rarefaction, and inflammation as potential mediators of its development. CMD can be diagnosed via several noninvasive methods including transthoracic echocardiography, cardiac magnetic resonance, and positron emission tomography. Moreover, invasive methods such as coronary flow reserve and index of microcirculatory resistance are commonly employed in the assessment of CMD. As far as the association between CMD and HFpEF is concerned, numerous studies have highlighted the coexistence of CMD in the majority of HFpEF patients. Additionally, patients affected by both conditions may be facing an adverse prognosis. Finally, there is limited evidence suggesting a beneficial effect of renin-angiotensin-aldosterone system blockers, ranolazine, and sodium-glucose cotransporter-2 inhibitors in CMD, with further evidence being awaited regarding the impact of other pharmacotherapies such as anti-inflammatory agents.

Assessment of coronary endothelial dysfunction using contemporary coronary function testing

BACKGROUND

The established diagnosis of coronary endothelial dysfunction (CED) is through the response to low-dose acetylcholine during invasive coronary function testing (CFT). Current diagnostic criteria encompass deficient epicardial vasodilation and/or insufficient increase in coronary blood flow (CBF) calculated from additional Doppler flow velocity measurements. The aim is to evaluate the diagnostic yield of using angiographic epicardial vasomotion and CBF as single criteria for diagnosing CED during CFT.

METHODS

A total of 110 patients with angina and non-obstructive coronary arteries who underwent clinically indicated CFT were included. CED was defined as any reduction in epicardial diameter through quantitative coronary angiography and/or < 50 % increase in CBF compared to baseline after low-dose acetylcholine.

RESULTS

Based on current diagnostic criteria, 78 % of patients (N = 86/110) was diagnosed with CED. When only considering epicardial diameter, 24 % CED (N = 21/86) and 50 % severe CED diagnoses (N = 19/38) were missed. When only considering CBF, 27 % CED (N = 23/86) and 18 % severe CED diagnoses (N = 7/38) were missed. A similar diagnostic yield for CED detection was found for both parameters (OR: 0.913, 95 %CI 0.481-1.726, p = 0.763). The incidence of CFT diagnoses was comparable among all groups.

CONCLUSIONS

As single parameters, both epicardial diameter and CBF were ineffective in accurately diagnosing CED compared to the current diagnostic criteria. Combining both parameters is necessary to diagnose the complete spectrum of CED, as missed diagnoses of deficient CBF responses (e.g., microvascular CED) and epicardial vasomotion (e.g., epicardial CED) might occur when relying on these parameters as single diagnostic criteria for CED.

Reduction of Coronary Flow Velocity Reserve as the Main Driver of Prognostically Beneficial Coronary Revascularization

BACKGROUND

Regional wall motion abnormality (RWMA) can be absent during stress echocardiography (SE) in patients with chronic coronary syndromes (CCS) and angiographically significant coronary artery disease (CAD) despite a reduction of coronary flow velocity reserve (CFVR).

OBJECTIVES

To assess the value of a physiology-driven approach, based on CFVR, to coronary revascularization in patients with physiologically and anatomically significant disease of the left anterior descending (LAD) coronary artery.

METHODS

In a 3-center, observational study with retrospective analysis of prospectively acquired data, 749 patients with CCS, CFVR of the LAD ≤2.0, and ≥50% diameter stenosis of the LAD were enrolled. All patients were evaluated with dipyridamole (0.84 mg/kg in 6') SE. Patients were followed for 6.4 ± 4.5 years for the outcome of all-cause death.

RESULTS

Inducible RWMA was present in 295 patients (39%). Coronary flow velocity reserve was lower in patients with inducible RWMA compared to those without (1.51 ± 0.28 vs 1.65 ± 0.25; P < .001). Coronary revascularization was performed in 514 (69%) patients (388 with percutaneous coronary intervention, 126 with coronary artery bypass surgery). Of them, 226 exhibited inducible RWMA and 288 exhibited isolated reduction of CFVR. During the follow-up, 185 (25%) deaths occurred. The 10-year survival in the entire study population was 70%. The survival at 10 years was markedly lower in conservatively treated patients compared to invasively treated patients (53 vs 76%; P < .0001), with no significant difference between those with solitary reduction of CFVR and reduction of CFVR accompanied by concurrent inducible RWMA. Propensity score-weighted all-cause mortality risk was significantly higher for conservative than for invasive strategy (propensity score adjusted hazard ratio = 2.12; 95% CI, 1.51-2.96; P < .0001).

CONCLUSIONS

In patients with CCS and physiologically and anatomically significant LAD disease, coronary revascularization driven by a reduction in CFVR is accompanied by a prognostic benefit independently of the presence of inducible RWMA.

Chapter 13.0. FFR, iFR, CFR, and IMR: Results from clinical trials

In this review article, we provide an overview of the definition and application of fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), coronary flow reserve (CFR), and index of microvascular resistance (IMR) in the diagnosis, prognosis, and management of coronary microvascular dysfunction. We discuss their respective limitations as it relates to microvascular dysfunction. In each section, we review the most recent evidence supporting their use in microvascular and epicardial coronary artery disease. We also highlight specific clinical conditions with emerging indications for the use of these indices, including in the setting of microvascular dysfunction due to acute myocardial infarction, heart failure with preserved ejection fraction, and post-cardiac transplant.

Differences in coronary microcirculation measurements during regadenoson vs. adenosine - induced hyperemia

BACKGROUND

Little is known about the similarity of microcirculation assessment outcomes performed with regadenoson and adenosine. The aim of the current study was to compare coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) assessment using adenosine and regadenoson, and to evaluate predictors regarding the size of differences.

METHODS

44 patients were enrolled and diagnosed between 2021 and 2023. Fractional flow reserve (FFR), CFR and IMR were measured twice in the circumflex (Cx) (n = 8) or left anterior descending (LAD) (n = 36) artery: once with continuous infusion of adenosine (Adenocor 140 µg/kg/min) and 10 minutes later with regadenoson (Rapiscan 400 µg i.v.).

RESULTS

Averaged results were quantified with adenosine and regadenoson for FFR (0.81 [0.75 ÷ 0.89] vs. 0.80 [0.73 ÷ 0.88]), CFR (3.84 [1.67 ÷ 4.08] vs. 3.97 [1.78 ÷ 4.32]) and IMR (20.01 [11 ÷ 24.5] vs. 20.25 [10.75 ÷ 23]), respectively. None of the differences were statistically significant. Among the significant (p < 0.05) predictors of greater ΔCFR, the following can be noted: prior percutaneous transluminal angioplasty/carotid artery stenting (β = 2.35), oral anticoagulant usage (β = 0.89), and prior stroke/transient ischaemic attack (TIA) (β = 1.09), with the latter being also confirmed for greater ΔIMR (β = 8.89). Moreover, patients with New York Heart Association (NYHA) class II/III, as compared to those with NYHA class I, were more likely to have greater ΔIMR (β = 11.89).

CONCLUSIONS

Regadenoson may be a feasible alternative to adenosine in coronary microcirculation assessment, as it produces similar outcomes. Selected factors were found to be predictors of greater differences in IMR, CFR and FFR values according to the agent used for coronary hyperemia.

Vascular Remodeling in Coronary Microvascular Dysfunction

BACKGROUND

Approximately one-half of the patients with angina and nonobstructive coronary artery disease (ANOCA) have evidence of coronary microvascular dysfunction (CMD).

OBJECTIVES

This study aims to characterize patients with ANOCA by measuring their minimal microvascular resistance and to examine the pattern of vascular remodeling associated with these measurements.

METHODS

The authors prospectively included patients with ANOCA undergoing continuous thermodilution assessment. Lumen volume and vessel-specific myocardial mass were quantified using coronary computed tomography angiography (CTA). CMD was defined as coronary flow reserve <2.5 and high minimal microvascular resistance as >470 WU.

RESULTS

A total of 153 patients were evaluated; 68 had CMD, and 22 of them showed high microvascular resistance. In patients with CMD, coronary flow reserve was 1.9 ± 0.38 vs 3.2 ± 0.81 in controls (P < 0.001). Lumen volume was significantly correlated with minimal microvascular resistance (r = -0.59 [95% CI: -0.45 to -0.71]; P < 0.001). In patients with CMD and high microvascular resistance, lumen volume was 40% smaller than in controls (512.8 ± 130.3 mm3 vs 853.2 ± 341.2 mm3; P < 0.001). Epicardial lumen volume assessed by coronary CTA was independently associated with minimal microvascular resistance (P < 0.001). The predictive capacity of lumen volume from coronary CTA for detecting high microvascular resistance showed an area under the curve of 0.79 (95% CI: 0.69-0.88).

CONCLUSIONS

Patients with CMD and high minimal microvascular resistance have smaller epicardial vessels than those without CMD. Coronary CTA detected high minimal microvascular resistance with very good diagnostic capacity. Coronary CTA could potentially aid in the diagnostic pathway for patients with ANOCA.

Developing a Women's Heart Center With a Specialization in Coronary Microvascular and Vasomotor Dysfunction: If You Build It, They Will Come

BACKGROUND

Women's Heart Centers (WHC) are comprehensive, multidisciplinary care centers designed to close the existing gap in women's cardiovascular care. The WHC at The Christ Hospital Heart and Vascular Institute (TCH-WHC) in Cincinnati, Ohio was established in October of 2020, and is a specialized coronary microvascular and vasomotor dysfunction (CMVD) program.

METHODS

The TCH-WHC focuses its efforts across five pillars: patient care, research, education, community outreach and advocacy, and grants and philanthropy. These areas, centered around providing specalized CMVD care and treatment have allowed for substantial growth.

RESULTS

From October 2020-December 2023, TCH-WHC saw a total of 3219 patients, 42% of which were apart of the CMVD program. Since establishment, patient volume has consistently increased year over year.

CONCLUSION

The CMVD program at TCH-WHC is one of the fastest growing in the U. S. and is nationally recognized for specialized clinical care, diagnostics, and research. The goal of this review is to provide an overview of the TCH-WHC structure that allows for the establishment and growth of a CMVD program and to outline core activities supporting the TCH-WHC approach.

Troponin Elevation in Asymptomatic Cancer Patients: Unveiling Connections and Clinical Implications

PURPOSE OF THE REVIEW

Elevated troponin levels are well established e.g., for the diagnosis of suspected acute coronary syndrome in symptomatic patients. In contrast, troponin elevations in asymptomatic cancer patients emerge as a complex phenomenon, challenging traditional perceptions of its association solely with cardiac events.

RECENT FINDINGS

Recent data support the predictive value of cardiac biomarker for all-cause mortality and cardiotoxicity in cancer patients. This review gives an overview about the current literature about cardiac troponins in prediction and identification of high-risk cancer patients. The overview is focusing on diagnostic challenges, biomarker significance, and gaps of knowledge. Latest publications highlight the relevance of cardiac troponin in risk analysis before cancer treatment as well as a potential diagnostic gatekeeper for further cardiological diagnostics and therapy.

Utilizing Invasive Coronary Functional Testing in a Coronary Microvascular and Vasomotor Dysfunction Program: Methods and Considerations

BACKGROUND

Coronary microvascular and vasomotor dysfunction (CMVD) is associated with a threefold increased risk of major adverse cardiovascular events (MACE) and is the primary mechanism responsible for angina/ischemia in patients with nonobstructive coronary artery disease (ANOCA/INOCA). Proper assessment for CMVD is vital to provide targeted treatment and improve patient outcomes. Invasive coronary functional testing (ICFT) is the "gold standard," for CMVD assessment and can be used to diagnose all endotypes. However, there is a lack of standardization for ICFT protocols and use in the treatment of CMVD.

AIMS

To provide a comprehensive overview of ICFT protocols utilized at the Christ Hospital Womens Heart Center (TCH-WHC).

METHODS

Here, we outline our standard operating procedures for ICFT utilized at TCH-WHC, including the procedures two main methods: Doppler and Thermodilution. We describe our structured approach for ICFT referral and postdiagnostic clinical management utilized at The Christ Hospital Women's Heart Center (TCH-WHC) CMVD program. We then quantified how ICFT has contributed to growth of the TCH-WHC.

RESULTS

From October of 2020 until July of 2024, a total of 422 patients have undergone ICFT at TCH-WCH, 64% were performed via the Doppler protocol and 36% were performed via the Thermodilution protocol. Based on exclusive endotype categories, 19% had an endothelial-independent CMD alone, 19% had endothelial-dependent CMD or microvascular VSA alone, 3% had epicardial VSA alone, 42% had mixed disease (any combination of the above categories), and 17% had a normal ICFT.

CONCLUSIONS

ICFT provides opportunity to provide diagnostic clarity and optimize medical treatment for CMVD. TCH-WHC's structured approach for ICFT referral and protocol for conducting comprehensive ICFT which has been vital for the growth of our specialized CMVD program.

Myocardial Ischemic Syndromes: A New Nomenclature to Harmonize Evolving International Clinical Practice Guidelines

Since the 1960s, cardiologists have adopted several binary classification systems for acute myocardial infarction (MI) that facilitated improved patient management. Conversely, for chronic stable manifestations of myocardial ischemia, various classifications have emerged over time, often with conflicting terminology-eg, "stable coronary artery disease" (CAD), "stable ischemic heart disease," and "chronic coronary syndromes" (CCS). While the 2019 European guidelines introduced CCS to impart symmetry with "acute coronary syndromes" (ACS), the 2023 American guidelines endorsed the alternative term "chronic coronary disease." An unintended consequence of these competing classifications is perpetuation of the restrictive terms "coronary" and 'disease', often connoting only a singular obstructive CAD mechanism. It is now important to advance a more broadly inclusive terminology for both obstructive and non-obstructive causes of angina and myocardial ischemia that fosters conceptual clarity and unifies dyssynchronous nomenclatures across guidelines. We, therefore, propose a new binary classification of "acute myocardial ischemic syndromes" and "non-acute myocardial ischemic syndromes," which comprises both obstructive epicardial and non-obstructive pathogenetic mechanisms, including microvascular dysfunction, vasospastic disorders, and non-coronary causes. We herein retain accepted categories of ACS, ST-segment elevation MI, and non-ST-segment elevation MI, as important subsets for which revascularization is of proven clinical benefit, as well as new terms like ischemia and MI with non-obstructive coronary arteries. Overall, such a more encompassing nomenclature better aligns, unifies, and harmonizes different pathophysiologic causes of myocardial ischemia and should result in more refined diagnostic and therapeutic approaches targeted to the multiple pathobiological precipitants of angina pectoris, ischemia, and infarction.

The evaluation of combined fractional flow reserve and dynamic SPECT in chronic total occlusion

Background

Chronic total occlusion (CTO) is the most challenging subset in percutaneous coronary intervention (PCI), but the optimal selection of patients and indication for such procedures remain a subject of debate. We sought to investigate the role of physiological function in treatment decisions of CTO PCI by measuring fractional flow reserve (FFR) and Dynamic SPECT imaging in this study.

Methods

All the FFR of CTO vessel were measured before and immediately after CTO revascularization, and Dynamic SPECT imaging were detected before PCI in patients with an identified CTO.

Results

A total of 53 patients with single-vessel CTO lesions were included in this cohort study. The mean FFR value was 0.34 ± 0.09 at baseline. Immediately after successful CTO PCI, the FFR value significantly increased to 0.79 ± 0.11. The regional coronary flow reserve (CFR) of CTO vessels was 1.62 ± 0.64, which was significantly and positively correlated with the baseline FFR value (r = 0.607, p = 0.005). The area under the ROC curve of the baseline FFR for the detection of ischemia was 0.923 (p < 0.001). The diagnostic performance in terms of sensitivity and specificity was 83.3 % and 85.7 % for baseline FFR with a ROC-optimized cutoff value of 0.35.

Conclusions

A significant correlation was found between the CFR derived from dynamic SPECT and baseline FFR. An FFR of <0.35 before CTO PCI can be taken as the cutoff for the presence of inducible ischemia, which was a useful index for therapy options.

Systematic review and meta-analysis of randomized and nonrandomized studies on fractional flow reserve-guided revascularization

INTRODUCTION AND OBJECTIVES

Several studies have investigated the effectiveness of fractional flow reserve (FFR) guidance in improving clinical outcomes after myocardial revascularization, yielding conflicting results. The aim of this study was to compare clinical outcomes in patients with coronary artery disease following FFR-guided or angiography-guided revascularization.

METHODS

Both randomized controlled trials (RCTs) and nonrandomized intervention studies were included. Coprimary endpoints were all-cause death, myocardial infarction, and major adverse cardiovascular events (MACE). The study is registered with PROSPERO (CRD42022344765).

RESULTS

A total of 30 studies enrolling 393 588 patients were included. FFR-guided revascularization was associated with significantly lower rates of all-cause death (OR, 0.63; 95%CI, 0.53-0.73), myocardial infarction (OR, 0.70; 95%CI, 0.59-0.84), and MACE (OR, 0.77; 95%CI, 0.70-0.85). When only RCTs were considered, no significant difference between the 2 strategies was observed for any endpoints. However, the use of FFR was associated with reduced rates of revascularizations and treated lesions. Metaregression suggested that the higher the rate of revascularized patients the lower the benefit of FFR guidance on MACE reduction compared with angiography guidance (P=.012). Similarly, higher rates of patients with acute coronary syndromes were associated with a lower benefit of FFR-guided revascularization (P=.039).

CONCLUSIONS

FFR-guided revascularization was associated with lower rates of all-cause death, myocardial infarction and MACE compared with angiographic guidance, with RCTs and nonrandomized intervention studies yielding conflicting data. The benefits of FFR-guidance seem to be less evident in studies with high revascularization rates and with a high prevalence of patients with acute coronary syndrome.

Risk factors for unsuccessful restoration of coronary flow reserve after coronary bypass surgery

OBJECTIVES

Coronary flow reserve (CFR) is a strong predictor of cardiovascular events and prognosis in patients with coronary artery disease. This study aimed to evaluate preoperative factors associated with the unsuccessful restoration of CFR after coronary artery bypass grafting (CABG).

METHODS

Included in this study were the 65 patients who presented with functionally significant left anterior descending artery (LAD) lesions confirmed by both fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR), and who underwent successful CABG at our hospital within the study period. After CABG, graft patency was confirmed by coronary computed tomography angiography, and CFR in the LAD artery was measured by echocardiography. We defined postoperative CFR <2.5 as impaired CFR, and CFR ≥2.5 as preserved CFR.

RESULTS

Of the 65 patients, 14 patients (22%) showed impaired CFR, while 51 patients had preserved CFR. Patients with impaired CFR had significantly higher HbA1c (6.7% vs. 6.0%, P < 0.01), greater use of insulin (43% vs. 4%, P < 0.01), longer lesion length (33 mm vs. 25 mm, P = 0.044), and lower iFR (0.69 vs 0.81, P = 0.01) than those with preserved CFR, although both groups had comparable FFR (0.65 vs 0.64, P = 0.46). In receiver operating characteristic curve analysis, iFR had a significantly larger area under the curve than FFR in terms of the prediction of impaired CFR (0.74 vs 0.42, P = 0.01).

CONCLUSIONS

Poorly-controlled preoperative diabetes, greater reliance on insulin, longer lesion length and lower iFR were associated with postoperative impaired CFR, suggesting the involvement of microvascular dysfunction.

Coronary microvascular dysfunction and cancer therapy-related cardiovascular toxicity

BACKGROUND

Coronary microvascular dysfunction (CMD) has been implicated as a potential mechanism in the pathophysiology of different clinical presentations, including ischemia and no obstructive coronary artery disease (INOCA), myocardial infarction and nonobstructive coronary arteries (MINOCA), stress cardiomyopathy, heart failure, and myocarditis. There are limited data about the role of CMD in cancer therapy-related cardiovascular toxicities.

CASE PRESENTATIONS

Four women with a diagnosis of active cancer receiving treatment who developed subsequent MINOCA or INOCA presented for cardiac catheterization. Upon coronary angiography showing no obstructive coronary arteries, coronary function testing was performed to evaluate for CMD.

METHODS

Coronary physiology was assessed measuring non-hyperemic (resting full-cycle ratio [RFR]) and hyperemic (fractional flow reserve [FFR]) indices using a physiologic pressure wire. The wire also measured coronary flow reserve (CFR), index of microcirculatory resistance (IMR), and RFR using thermodilution technology. CMD was confirmed if the CFR was <2.5 and the IMR was >25.

RESULTS

Among 4 patients with diagnosis of active cancer presenting with chest pain, there was no evidence of obstructive coronary artery disease, leading to separate diagnoses of INOCA, MINOCA, stress cardiomyopathy, and myocarditis. We found CMD in 2 patients (1 with INOCA and 1 with immune checkpoint inhibitor-related myocarditis).

CONCLUSIONS

CMD may play a role in cardiovascular toxicities. Further coronary physiology studies are needed to understand the mechanisms of cancer therapy-related cardiovascular toxicity and CMD, as well as optimal preventive and treatment options.

Clinical Applications and Advancements of Positron Emission Tomography/Computed Tomography in Cardio-Oncology: A Comprehensive Literature Review and Emerging Perspectives

PURPOSE OF REVIEW

Recent advancements in molecular biology, biotechnology, chemistry/radiochemistry, artificial intelligence, and imaging techniques have significantly propelled the field of cardiovascular molecular imaging. This review aims to provide a comprehensive overview of the current state of cardiovascular positron emission tomography (PET) imaging and cardiac computed tomography (CT), exploring their roles in elucidating molecular and cellular processes, enabling early disease detection, and guiding novel therapeutic interventions for cardiovascular conditions.

RECENT FINDINGS

Cardiovascular PET imaging strives to uncover molecular and cellular events preceding visible anatomical manifestations or physiological changes. Meanwhile, cardiac CT has evolved into a multifaceted modality, offering insights into both anatomy and function. Utilizing advanced CT technologies allows for a thorough evaluation, encompassing fractional flow reserve, perfusion imaging, pericoronary adipose tissue attenuation, atherosclerotic plaque characterization, cardiomyopathies, structural cardiac abnormalities, and congenital heart anomalies. The emergence of hybrid imaging, combining PET and CT, presents innovative prospects in cardiology. This approach enables the simultaneous assessment of cardiac perfusion and coronary anatomy in a singular scan, providing complementary insights relevant to potential coronary artery disease. Despite the substantial potential impact, operational familiarity with this hybrid tool remains limited, and its integration into routine clinical practice warrants further exploration. In summary, the review underscores the transformative impact of recent technological advancements on cardiovascular molecular imaging. The integration of PET and CT, along with their individual capabilities, holds promise for early disease detection and informed clinical decision-making. While acknowledging the potential of hybrid imaging, it emphasizes the need for increased operational familiarity and continued exploration to facilitate its seamless integration into routine clinical practice. The insights gained from this review contribute to the ongoing dialogue in the field, offering a foundation for future research and advancements in cardiovascular imaging.

Basal Coronary Microvascular Resistance Predicting Death and Heart Failure in Patients Without Functional Coronary Stenosis

BACKGROUND

Abnormal coronary microcirculation is linked to poor patient prognosis, so the aim of the present study was to assess the prognostic relevance of basal microvascular resistance (b-IMR) in patients without functional coronary stenosis.

METHODS AND RESULTS

Analyses of 226 patients who underwent intracoronary physiological assessment of the left anterior descending artery included primary endpoints of all-cause death and heart failure, as well as secondary endpoints of cardiovascular death and atherosclerotic vascular events. During a median follow-up of 2 years, there were 12 (5.3%) primary and 21 (9.3 %) secondary endpoints. The optimal b-IMR cutoff for the primary endpoints was 47.1 U. Kaplan-Meier curve analysis demonstrated worse event-free survival of the primary endpoints in patients with a b-IMR below the cutoff (χ2=21.178, P<0.001). b-IMR was not significantly associated with the secondary endpoints (P=0.35). A low coronary flow reserve (CFR; <2.5) had prognostic value for both endpoints (primary endpoints: χ2=11.401, P=0.001; secondary endpoints: (χ2=6.015; P=0.014), and high hyperemic microvascular resistance (≥25) was associated only with the secondary endpoints (χ2=4.420; P=0.036). Incorporating b-IMR into a clinical model that included CFR improved the Net Reclassification Index and Integrated Discrimination Improvement for predicting the primary endpoints (P<0.001 and P=0.034, respectively).

CONCLUSIONS

b-IMR may be a specific marker of the risk of death and heart failure in patients without functional coronary stenosis.

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.

Coronary microvascular disease in women: epidemiology, mechanisms, evaluation, and treatment

Coronary microvascular dysfunction (CMD) involves functional or structural abnormalities of the coronary microvasculature resulting in dysregulation of coronary blood flow (CBF) in response to myocardial oxygen demand. This perfusion mismatch causes myocardial ischemia, which manifests in patients as microvascular angina (MVA). CMD can be diagnosed non-invasively via multiple imaging techniques or invasively using coronary function testing (CFT), which assists in determining the specific mechanisms involving endothelium-independent and dependent epicardial and microcirculation domains. Unlike traditional coronary artery disease (CAD), CMD can often occur in patients without obstructive atherosclerotic epicardial disease, which can make the diagnosis of CMD difficult. Moreover, MVA due to CMD is more prevalent in women and carries increased risk of future cardiovascular events. Successful treatment of symptomatic CMD is often patient-specific risk factor and endotype targeted. This article aims to review newly identified mechanisms and novel treatment strategies for managing CMD, and outline sex-specific differences in the presentation and pathophysiology of the disease.

Can Galanin Be Used as a Marker of Microvascular Dysfunction in Prehypertensives?

Objectives

Coronary microvascular dysfunction is present in large percentage of the population, and it has been shown to have a pathological and prognostic role in many conditions. Therefore, early detection of microvascular dysfunction is important, especially in selected populations. The aim of this study was to investigate the association of galanin with coronary flow reserve (CFR) in prehypertensive individuals to determine whether it can be used as a marker to detect microvascular dysfunction.

Methods

A total of 100 participants, 50 prehypertensive and 50 normotensive were included in this prospective study. Serum galanin levels were measured and CFR was calculated by detailed transthoracic echocardiography.

Results

CFR was significantly lower in the prehypertensive group (p<0.001). Also, galanin values were numerically lower in the prehypertensive group, but the difference between the groups did not reach statistical significance (p=0.062). There was no significant correlation between CFR and galanin (r=-0.161, p=0.11).

Conclusion

Lower CFR values in prehypertensives suggest that microvascular dysfunction starts above normotensive values even if hypertension does not develop. The reason why low galanin levels were not statistically significant in prehypertensives and no correlation was found between galanin and CFR may be due to the small study population. Relationship between galanin, prehypertension and microvascular dysfunction will become clearer if large-scale population studies are carried out.

Myocardial ischaemic syndromes: a new nomenclature to harmonize evolving international clinical practice guidelines

Since the 1960s, cardiologists have adopted several binary classification systems for acute myocardial infarction (MI) that facilitated improved patient management. Conversely, for chronic stable manifestations of myocardial ischaemia, various classifications have emerged over time, often with conflicting terminology-e.g. 'stable coronary artery disease' (CAD), 'stable ischaemic heart disease', and 'chronic coronary syndromes' (CCS). While the 2019 European guidelines introduced CCS to impart symmetry with 'acute coronary syndromes' (ACS), the 2023 American guidelines endorsed the alternative term 'chronic coronary disease'. An unintended consequence of these competing classifications is perpetuation of the restrictive terms 'coronary' and 'disease', often connoting only a singular obstructive CAD mechanism. It is now important to advance a more broadly inclusive terminology for both obstructive and non-obstructive causes of angina and myocardial ischaemia that fosters conceptual clarity and unifies dyssynchronous nomenclatures across guidelines. We, therefore, propose a new binary classification of 'acute myocardial ischaemic syndromes' and 'non-acute myocardial ischaemic syndromes', which comprises both obstructive epicardial and non-obstructive pathogenetic mechanisms, including microvascular dysfunction, vasospastic disorders, and non-coronary causes. We herein retain accepted categories of ACS, ST-segment elevation MI, and non-ST-segment elevation MI, as important subsets for which revascularization is of proven clinical benefit, as well as new terms like ischaemia and MI with non-obstructive coronary arteries. Overall, such a more encompassing nomenclature better aligns, unifies, and harmonizes different pathophysiologic causes of myocardial ischaemia and should result in more refined diagnostic and therapeutic approaches targeted to the multiple pathobiological precipitants of angina pectoris, ischaemia and infarction.

Emerging opportunities to target inflammation: myocardial infarction and type 2 diabetes

After myocardial infarction (MI), patients with type 2 diabetes have an increased rate of adverse outcomes, compared to patients without. Diabetes confers a 1.5-2-fold increase in early mortality and, importantly, this discrepancy has been consistent over recent decades, despite advances in treatment and overall survival. Certain assumptions have emerged to explain this increased risk, such as differences in infarct size or coronary artery disease severity. Here, we re-evaluate that evidence and show how contemporary analyses using state-of-the-art characterization tools suggest that the received wisdom tells an incomplete story. Simultaneously, epidemiological and mechanistic biological data suggest additional factors relating to processes of diabetes-related inflammation might play a prominent role. Inflammatory processes after MI mediate injury and repair and are thus a potential therapeutic target. Recent studies have shown how diabetes affects immune cell numbers and drives changes in the bone marrow, leading to pro-inflammatory gene expression and functional suppression of healing and repair. Here, we review and re-evaluate the evidence around adverse prognosis in patients with diabetes after MI, with emphasis on how targeting processes of inflammation presents unexplored, yet valuable opportunities to improve cardiovascular outcomes in this vulnerable patient group.

Comparison of Ticagrelor with Clopidogrel on Coronary Microvascular Dysfunction Following Acute Myocardial Infarction Using Angiography-Derived Index of Microcirculatory Resistance

PURPOSE

This research aimed to assess the impact of ticagrelor and clopidogrel on coronary microvascular dysfunction (CMD) and prognosis following acute myocardial infarction (AMI), using the angiography-derived index of microcirculatory resistance (angio-IMR) as a non-invasive assessment tool.

METHODS

In this retrospective study, angio-IMR was performed to evaluate CMD before and after dual antiplatelet therapy (DAPT) with either ticagrelor (90 mg twice daily, n = 184) or clopidogrel (75 mg once daily, n = 72). The primary endpoint is the improvement of CMD evaluated by angio-IMR (delta angio-IMR) following DAPT. Secondary endpoints included myocardial reinfarction and readmission for heart failure during 2-year follow-up.

RESULTS

Compared with clopidogrel, ticagrelor exhibited a significantly higher delta angio-IMR [- 3.09 (5.14) versus - 1.99 (1.91), P = 0.008], indicating a superior improvement of CMD with ticagrelor treatment. Multivariate Cox regression indicated that ticagrelor treatment was related to a reduced risk of readmission for heart failure [8 (4.3) versus 9 (12.5), adjusted HR = 0.329; 95% CI = 0.116-0.934; P = 0.018] and myocardial reinfarction [7 (3.8) versus 8 (11.1), adjusted HR = 0.349; 95% CI = 0.125-0.975; P = 0.026]. Furthermore, ticagrelor treatment serves as an independent predictor of readmission for heart failure (HR = 0.322; 95% CI = 0.110-0.943; P = 0.039).

CONCLUSION

The results of this study indicate a potential association between ticagrelor treatment and improved CMD, as well as a reduced risk of cardiovascular events, including myocardial reinfarction and readmission for heart failure in AMI patients. Further randomized controlled trials are necessary to confirm the potential benefits of ticagrelor on CMD and cardiovascular prognosis. This clinical trial was registered in www.

CLINICALTRIALS

gov (NCT05978726).

Ischemia with non-obstructive coronary artery (INOCA): Non-invasive versus invasive techniques for diagnosis and the role of #FullPhysiology

Ischemia with non-obstructive coronary arteries (INOCA) is an increasingly recognized entity. It encompasses different pathophysiological subtypes (i.e., endotypes), including coronary microvascular dysfunction (CMD), vasospastic angina (VSA) and mixed entities resulting from the variable combination of both. Diagnosing INOCA and precisely characterizing the endotype allows for accurate medical treatment and has proven prognostic implications. A breadth of diagnostic technique is available, ranging from non-invasive approaches to invasive coronary angiography adjuvated by functional assessment and provocative tests. This review summarizes the strength and limitations of these methodologies and provides the rationale for the routine referral for invasive angiography and functional assessment in this subset of patients.

Usefulness of triglyceride-glucose index and homeostatic model assessment for predicting coronary microvascular dysfunction

BACKGROUND

Coronary microvascular dysfunction (CMD) is a common occurrence in individuals with insulin resistance (IR). Homeostatic model assessment for insulin resistance (HOMA-IR) is a widely used surrogate marker of IR, although recent studies suggest triglyceride-glucose (TyG) index is a superior marker of IR that had a better accuracy to predict type 2 diabetes or cardiovascular outcomes than HOMA-IR.

OBJECTIVES

We aimed to assess the accuracy and usefulness of TyG index and HOMA-IR for predicting CMD as assessed with echocardiographic coronary flow reserve (CFR) measurement.

METHODS

All cases included in the institutional CFR registry were retrospectively reviewed, and 656 cases without epicardial coronary artery disease and without major risk factors for atherosclerosis were included. A CFR ≤2.0 was defined as CMD.

RESULTS

TyG index was available in all cases, while HOMA-IR was available in 398 cases. Both TyG index and HOMA-IR were associated with CMD on univariate analyses, while after adjustment for potential confounders HOMA-IR (odds ratio [OR]:1.38, 95% confidence interval [CI]:1.14-1.67, p = 0.001) but not TyG index (OR:1.48, 95% CI:0.82-2.67, p = 0.19) was associated with CMD. The predictive accuracy of HOMA-IR (c-statistic:0.63, 95% CI:0.54-0.72, p = 0.003) was higher than TyG index(c-statistic:0.55, 95% CI:0.47-0.63, p = 0.13), although the difference was not statistically significant (DeLong p = 0.23). There was strong evidence favoring a true difference between CMD vs. non-CMD groups for HOMA-IR (BF10:3507) but not for TyG index(BF10:0.66).

CONCLUSIONS

HOMA-IR, but not TyG index, is closely associated with CMD.

Developments and Controversies in Invasive Diagnosis of Coronary Microvascular Dysfunction in Angina With Nonobstructive Coronary Arteries

Approximately half of all coronary angiograms performed for angina do not show obstructive coronary artery disease, and many of these patients have coronary microvascular dysfunction (CMD). Invasive testing for CMD has increased with the advent and wider availability of thermodilution systems. We review CMD pathophysiology and invasive diagnostic testing using the Doppler and thermodilution systems. We report the results of a PubMed search of invasive microvascular testing and discuss limitations of current diagnostic algorithms in the diagnosis of CMD, including controversies regarding the optimal cutoff value for abnormal coronary flow reserve, use of microvascular resistance indices, and options for increasing sensitivity of testing.