Coronary Microvascular Dysfunction Is Associated With Myocardial Ischemia and Abnormal Coronary Perfusion During Exercise

Relationship between coronary microvascular dysfunction (CMD) and left ventricular diastolic function in patients with symptoms of myocardial ischemia with non-obstructive coronary artery disease (INOCA) by cardiovascular magnetic resonance feature-tracking

AIM

To investigate whether there was an association between coronary microvascular dysfunction (CMD) and left ventricular (LV) diastolic function in patients with myocardial ischemia with non-obstructive coronary artery disease (INOCA).

MATERIALS AND METHODS

Our study included 115 subjects with suspected myocardial ischemia that underwent stress perfusion cardiac magnetic resonance (CMR). They were divided into non-CMD and CMD two groups. CMR-derived volume-time curves and CMR-FT parameters were used to assess LV diastolic function using CVI42 software. The latter included global/regional LV peak longitudinal, circumferential, radial diastolic strain rate (LDSR, CDSR, RDSR). Logistic regression analysis was performed with CMR-FT strain parameters as independent variables and CMD as dependent variables, and the effect value was expressed as an odds ratio (OR).

RESULTS

Of the 115 patients, we excluded data from 23 patients and 92 patients (56.5% male；52 ± 12 years) were finally included in the study. Of these, 19 patients were included in the non-CMD group (49 ± 11 years) and CMD group included 73patient (52 ± 12 years). The regional CDSR (P=0.019), and regional RDSR (P=0.006) were significantly lower in the CMD group than in non-CMD group. But, regional LDSR in CMD group was higher than non-CMD (P=0.003). In logistic regression analysis, regional LDSR (adjusted β= 0.1, 95%CI 0.077, 0.349, p=0.002) and RDSR (adjusted β= 0.1, 95 % CI 0.066, 0.356, p=0.004) were related to CMD.

CONCLUSIONS

LV myocardial perfusion parameter MPRI was negatively correlated with LV diastolic function (CDSR) which needs to take into account the degree of diastolic dysfunction.

Coronary microvascular dysfunction in childhood: An emerging pathological entity and its clinical implications

Coronary microvascular dysfunction (CMD) encompasses a spectrum of structural and functional alterations in coronary microvasculature resulting in impaired coronary blood flow and consequent myocardial ischemia without obstruction in epicardial coronary artery. The pathogenesis of CMD is complex involving both functional and structural alteration in the coronary microcirculation. In adults, CMD is predominantly discussed in context with anginal chest pain or existing ischemic heart disease and its risk factors. The presence of CMD suggests increased risk of adverse cardiovascular events independent of coronary atherosclerosis. Coronary microvascular dysfunction is also known in children but is rarely recognized due to paucity of concommitent coronary artery disease. Thus, its clinical presentation, underlying mechanism of impaired microcirculation, and prognostic significance are poorly understood. In this review article, we will overview variable CMD reported in children and delineate its emerging clinical significance.

Transthoracic ultrasound localization microscopy of myocardial vasculature in patients

Myocardial microvasculature and haemodynamics are indicative of potential microvascular diseases for patients with symptoms of coronary heart disease in the absence of obstructive coronary arteries. However, imaging microvascular structure and flow within the myocardium is challenging owing to the small size of the vessels and the constant movement of the patient's heart. Here we show the feasibility of transthoracic ultrasound localization microscopy for imaging myocardial microvasculature and haemodynamics in explanted pig hearts and in patients in vivo. Through a customized data-acquisition and processing pipeline with a cardiac phased-array probe, we leveraged motion correction and tracking to reconstruct the dynamics of microcirculation. For four patients, two of whom had impaired myocardial function, we obtained super-resolution images of myocardial vascular structure and flow using data acquired within a breath hold. Myocardial ultrasound localization microscopy may facilitate the understanding of myocardial microcirculation and the management of patients with cardiac microvascular diseases.

The role of coronary microvascular dysfunction in the pathogenesis of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is a common condition with few effective therapies and hence represents a major healthcare burden. The clinical syndrome of HFpEF can be caused by varying pathophysiological processes, with coronary microvascular dysfunction (CMD) proposed as one of the aetiologies, although confirming causality has been challenging. CMD is characterised by the inability of the coronary vasculature to augment blood flow in response to a physiological stressor and has been established as the driver of angina in patients with non-obstructed coronaries (ANOCA), and this has subsequently led to efficacious endotype-directed therapies. CMD is also highly prevalent among sufferers of HFpEF and may represent a novel treatment target for this particular endotype of this condition. This review aims to discuss the role of the microcirculation in the healthy heart how it's dysfunction may precipitate HFpEF and explore the current diagnostic tools available. We also discuss the gaps in evidence and where we believe future research should be focussed.

Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction

BACKGROUND

Ischemia with no obstructive coronary arteries is frequently caused by coronary microvascular dysfunction (CMD). Consensus diagnostic criteria for CMD include baseline angiographic slow flow by corrected TIMI (Thrombolysis In Myocardial Infarction) frame count (cTFC), but correlations between slow flow and CMD measured by invasive coronary function testing (CFT) are uncertain.

OBJECTIVES

The aim of this study was to investigate relationships between cTFC and invasive CFT for CMD.

METHODS

Adults with ischemia with no obstructive coronary arteries underwent invasive CFT with thermodilution-derived baseline coronary blood flow, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR). CMD was defined as abnormal CFR (<2.5) and/or abnormal IMR (≥25). cTFC was measured from baseline angiography; slow flow was defined as cTFC >25. Correlations between cTFC and baseline coronary flow and between CFR and IMR and associations between slow flow and invasive measures of CMD were evaluated, adjusted for covariates. All patients provided consent.

RESULTS

Among 508 adults, 49% had coronary slow flow. Patients with slow flow were more likely to have abnormal IMR (36% vs 26%; P = 0.019) but less likely to have abnormal CFR (28% vs 42%; P = 0.001), with no difference in CMD (46% vs 51%). cTFC was weakly correlated with baseline coronary blood flow (r = -0.35; 95% CI: -0.42 to -0.27), CFR (r = 0.20; 95% CI: 0.12 to 0.28), and IMR (r = 0.16; 95% CI: 0.07-0.24). In multivariable models, slow flow was associated with lower odds of abnormal CFR (adjusted OR: 0.53; 95% CI: 0.35 to 0.80).

CONCLUSIONS

Coronary slow flow was weakly associated with results of invasive CFT and should not be used as a surrogate for the invasive diagnosis of CMD.

[Myocardial Infarction with no obstructive coronary arteries: Imaging plays a central role]

Myocardial infarction with non-obstructive coronary lesion (MINOCA) represents a non-negligible percentage of the proportion of myocardial infarctions (≈6%). Moreover, the long-term prognosis is poor, with an annual mortality rate of 2%. This high mortality rate may be explained by the fact that MINOCA represents a heterogeneous group, and the diagnosis of pathology is poorly understood. It is essential to be aware of this clinical presentation, and to follow the different diagnostic strategies, in order to identify the etiological mechanism, and thus set up a suitable treatment. Many tools are available to support diagnosis, notably in the fields of imaging, the principal contributors being coronary angiography, coronary physiology and pharmacological testing, as well as endo-coronary imaging and cardiac MRI. This review will provide an update on the definition, epidemiology, diagnostic strategies and treatment options for patients with MINOCA.

Intracoronary electrocardiogram detects coronary microvascular dysfunction and ischemia in patients with no obstructive coronary arteries disease

BACKGROUND

Coronary microvascular dysfunction (CMD) is the leading cause of ischemia with no obstructive coronary arteries disease (INOCA) disease. Diagnosis of CMD relies on surrogate physiological indices without objective proof of ischemia.

OBJECTIVES

Intracoronary electrocardiogram (icECG) derived hyperemic indices may accurately and objectively detect CMD and reversible ischemia in related territory.

METHODS

INOCA patients with proven ischemia by myocardial perfusion scan (MPS) and completely normal coronary arteries underwent simultaneous intracoronary electrophysiological (icECG) and physiological (intracoronary Doppler) assessment in all 3 coronary arteries during rest and under adenosine induced hyperemia.

RESULTS

Sixty vessels in 21 patients were included in the final analysis. All patients had at least one vessel with abnormal CFR. 41 vessels had CMD (CFR < 2.5), of which 26 had increased microvascular resistance (structural CMD, HMR > 1.9 mmHg.cm-1.s) and 15 vessels had CMD (CFR < 2.5) with normal microvascular resistance (functional CMD, HMR <= 1.9 mmHg.cm-1.s). Only one-third of the patients (n = 7) had impaired CFR < 2.5 in all 3 epicardial arteries. Absolute ST shift between hyperemia and rest (∆ST) has shown the best diagnostic performance for ischemia (cut-off 0.10 mV, sensitivity: 95%, specificity: 72%, accuracy: 80%, AUC: 0.860) outperforming physiological indices (CFR: 0.623 and HMR: 0.653 DeLong's test P = .0002).

CONCLUSIONS

In INOCA patients, CMD involves coronary artery territories heterogeneously. icECG can accurately detect CMD causing perfusion abnormalities in patients with INOCA outperforming physiological CMD markers, by demonstrating actual ischemia instead of predicting the likelihood of inducible ischemia based on violated surrogate thresholds of blunted flow reserve or increased minimum microvascular resistance.

CONDENSED ABSTRACT

In 21 INOCA patients with coronary microvascular dysfunction (CMD) and myocardial perfusion scan proved ischemia, hyperemic indices of intracoronary electrocardiogram (icECG) have accurately detected vessel-specific CMD and resulting perfusion abnormalities & ischemia, outperforming invasive hemodynamic indices. Absolute ST shift between hyperemia and rest (∆ST) has shown the best classification performance for ischemia in no Obstructive Coronary Arteries (AUC: 0.860) outperforming Doppler derived CMD indices (CFR: 0.623 and HMR: 0.653 DeLong's test P = .0002).icECG can be used to diagnose CMD causing perfusion defects by demonstrating actual reversible ischemia at vessel-level during the initial CAG session, obviating the need for further costly ischemia tests.

CLINICALTRIALS

GOV: NCT05471739.

ANOCA patients with and without coronary vasomotor dysfunction present with limited electrocardiographic remodeling

Background

Coronary vasomotor dysfunction (CVDys) comprises coronary vasospasm (CVS) and/or coronary microvascular dysfunction (CMD) and is highly prevalent in patients with angina and non-obstructive coronary artery disease (ANOCA). Invasive coronary function testing (CFT) to diagnose CVDys is becoming more common, enabling pathophysiologic research of CVDys. This study aims to explore the electrophysiological characteristics of ANOCA patients with CVDys.

Methods

We collected pre-procedural 12-lead electrocardiograms of ANOCA patients with CVS (n = 35), CMD (n = 24), CVS/CMD (n = 26) and patients without CVDys (CFT-, n = 23) who participated in the NL-CFT registry and underwent CFT. Heart axis and conduction times were compared between patients with CVS, CMD or CVS/CMD and patients without CVDys.

Results

Heart axis, heart rate, PQ interval and QRS duration were comparable between the groups. A small prolongation of the QT-interval corrected with Bazett (QTcB) and Fridericia (QTcF) was observed in patients with CVDys compared to patients without CVDys (CVS vs CFT-: QTcB = 422 ± 18 vs 414 ± 18 ms (p = 0.14), QTcF = 410 ± 14 vs 406 ± 12 ms (p = 0.21); CMD vs CFT-: QTcB = 426 ± 17 vs 414 ± 18 ms (p = 0.03), QTcF = 413 ± 11 vs 406 ± 12 ms (p = 0.04); CVS/CMD vs CFT-: QTcB = 424 ± 17 vs 414 ± 18 ms (p = 0.05), QTcF = 414 ± 14 vs 406 ± 12 ms (p = 0.04)).

Conclusions

Pre-procedural 12-lead electrocardiograms were comparable between patients with and without CVDys undergoing CFT except for a slightly longer QTc interval in patients with CVDys compared to patients without CVDys, suggesting limited cardiac remodeling in patients with CVDys.

Rethinking False Positive Exercise Electrocardiographic Stress Tests by Assessing Coronary Microvascular Function

BACKGROUND

Exercise electrocardiographic stress testing (EST) has historically been validated against the demonstration of obstructive coronary artery disease. However, myocardial ischemia can occur because of coronary microvascular dysfunction (CMD) in the absence of obstructive coronary artery disease.

OBJECTIVES

The aim of this study was to assess the specificity of EST to detect an ischemic substrate against the reference standard of coronary endothelium-independent and endothelium-dependent microvascular function in patients with angina with nonobstructive coronary arteries (ANOCA).

METHODS

Patients with ANOCA underwent invasive coronary physiological assessment using adenosine and acetylcholine. CMD was defined as impaired endothelium-independent and/or endothelium-dependent function. EST was performed using a standard Bruce treadmill protocol, with ischemia defined as the appearance of ≥0.1-mV ST-segment depression 80 ms from the J-point on electrocardiography. The study was powered to detect specificity of ≥91%.

RESULTS

A total of 102 patients were enrolled (65% women, mean age 60 ± 8 years). Thirty-two patients developed ischemia (ischemic group) during EST, whereas 70 patients did not (nonischemic group); both groups were phenotypically similar. Ischemia during EST was 100% specific for CMD. Acetylcholine flow reserve was the strongest predictor of ischemia during exercise. Using endothelium-independent and endothelium-dependent microvascular dysfunction as the reference standard, the false positive rate of EST dropped to 0%.

CONCLUSIONS

In patients with ANOCA, ischemia on EST was highly specific of an underlying ischemic substrate. These findings challenge the traditional belief that EST has a high false positive rate.

ChaMP-CMD: A Phenotype-Blinded, Randomized Controlled, Cross-Over Trial

BACKGROUND

Angina with nonobstructive coronary arteries is a common condition for which no effective treatment has been established. We hypothesized that the measurement of coronary flow reserve (CFR) allows identification of patients with angina with nonobstructive coronary arteries who would benefit from anti-ischemic therapy.

METHODS

Patients with angina with nonobstructive coronary arteries underwent blinded invasive CFR measurement and were randomly assigned to receive 4 weeks of amlodipine or ranolazine. After a 1-week washout, they crossed over to the other drug for 4 weeks; final assessment was after the cessation of study medication for another 4 weeks. The primary outcome was change in treadmill exercise time, and the secondary outcome was change in Seattle Angina Questionnaire summary score in response to anti-ischemic therapy. Analysis was on a per protocol basis according to the following classification: coronary microvascular disease (CMD group) if CFR<2.5 and reference group if CFR≥2.5. The study protocol was registered before the first patient was enrolled (International Standard Randomised Controlled Trial Number: ISRCTN94728379).

RESULTS

Eighty-seven patients (61±8 years of age; 62% women) underwent random assignment (57 CMD group and 30 reference group). Baseline exercise time and Seattle Angina Questionnaire summary scores were similar between groups. The CMD group had a greater increment (delta) in exercise time than the reference group in response to both amlodipine (difference in delta, 82 s [95% CI, 37-126 s]; P<0.001) and ranolazine (difference in delta, 68 s [95% CI, 21-115 s]; P=0.005). The CMD group reported a greater increment (delta) in Seattle Angina Questionnaire summary score than the reference group in response to ranolazine (difference in delta, 7 points [95% CI, 0-15]; P=0.048), but not to amlodipine (difference in delta, 2 points [95% CI, -5 to 8]; P=0.549).

CONCLUSIONS

Among phenotypically similar patients with angina with nonobstructive coronary arteries, only those with an impaired CFR derive benefit from anti-ischemic therapy. These findings support measurement of CFR to diagnose and guide management of this otherwise heterogeneous patient group.

High-resolution quantification of stress perfusion defects by cardiac magnetic resonance

Aims

Quantitative stress perfusion cardiac magnetic resonance (CMR) is becoming more widely available, but it is still unclear how to integrate this information into clinical decision-making. Typically, pixel-wise perfusion maps are generated, but diagnostic and prognostic studies have summarized perfusion as just one value per patient or in 16 myocardial segments. In this study, the reporting of quantitative perfusion maps is extended from the standard 16 segments to a high-resolution bullseye. Cut-off thresholds are established for the high-resolution bullseye, and the identified perfusion defects are compared with visual assessment.

Methods and results

Thirty-four patients with known or suspected coronary artery disease were retrospectively analysed. Visual perfusion defects were contoured on the CMR images and pixel-wise quantitative perfusion maps were generated. Cut-off values were established on the high-resolution bullseye consisting of 1800 points and compared with the per-segment, per-coronary, and per-patient resolution thresholds. Quantitative stress perfusion was significantly lower in visually abnormal pixels, 1.11 (0.75-1.57) vs. 2.35 (1.82-2.9) mL/min/g (Mann-Whitney U test P < 0.001), with an optimal cut-off of 1.72 mL/min/g. This was lower than the segment-wise optimal threshold of 1.92 mL/min/g. The Bland-Altman analysis showed that visual assessment underestimated large perfusion defects compared with the quantification with good agreement for smaller defect burdens. A Dice overlap of 0.68 (0.57-0.78) was found.

Conclusion

This study introduces a high-resolution bullseye consisting of 1800 points, rather than 16, per patient for reporting quantitative stress perfusion, which may improve sensitivity. Using this representation, the threshold required to identify areas of reduced perfusion is lower than for segmental analysis.

Characterizing Mechanisms of Ischemia in Patients With Myocardial Bridges

BACKGROUND

Myocardial bridges (MBs) are prevalent and can be associated with acute and chronic ischemic syndromes. We sought to determine the substrates for ischemia in patients with angina with nonobstructive coronary arteries and a MB in the left anterior descending artery.

METHODS

Patients with angina with nonobstructive coronary arteries underwent the acquisition of intracoronary pressure and flow during rest, supine bicycle exercise, and adenosine infusion. Coronary wave intensity analysis was performed, with perfusion efficiency defined as accelerating wave energy/total wave energy (%). Epicardial endothelial dysfunction was defined as a reduction in epicardial vessel diameter ≥20% in response to intracoronary acetylcholine infusion. Patients with angina with nonobstructive coronary arteries and a MB were compared with 2 angina with nonobstructive coronary arteries groups with no MB: 1 with coronary microvascular disease (CMD: coronary flow reserve, <2.5) and 1 with normal coronary flow reserve (reference: coronary flow reserve, ≥2.5).

RESULTS

Ninety-two patients were enrolled in the study (30 MB, 33 CMD, and 29 reference). Fractional flow reserve in these 3 groups was 0.86±0.05, 0.92±0.04, and 0.94±0.05; coronary flow reserve was 2.5±0.5, 2.0±0.3, and 3.2±0.6. Perfusion efficiency increased numerically during exercise in the reference group (65±9%-69±13%; P=0.063) but decreased in the CMD (68±10%-50±10%; P<0.001) and MB (66±9%-55±9%; P<0.001) groups. The reduction in perfusion efficiency had distinct causes: in CMD, this was driven by microcirculation-derived energy in early diastole, whereas in MB, this was driven by diminished accelerating wave energy, due to the upstream bridge, in early systole. Epicardial endothelial dysfunction was more common in the MB group (54% versus 29% reference and 38% CMD). Overall, 93% of patients with a MB had an identifiable ischemic substrate.

CONCLUSIONS

MBs led to impaired coronary perfusion efficiency during exercise, which was due to diminished accelerating wave energy in early systole compared with the reference group. Additionally, there was a high prevalence of endothelial and microvascular dysfunction. These ischemic mechanisms may represent distinct treatment targets.

Coronary Microvascular Dysfunction in Patients With Heart Failure: Characterization of Patterns in HFrEF Versus HFpEF

BACKGROUND

Coronary microvascular dysfunction (CMD) is involved in heart failure (HF) onset and progression, independently of HF phenotype and obstructive coronary artery disease. Invasive assessment of CMD might provide insights into phenotyping and prognosis of patients with HF. We aimed to assess absolute coronary flow, absolute microvascular resistance, myocardial perfusion, coronary flow reserve, and microvascular resistance reserve in patients with HF with preserved ejection fraction and HF with reduced ejection fraction (HFrEF).

METHODS

Single-center, prospective study of 56 consecutive patients with de novo HF with nonobstructive coronary artery disease divided into HF with preserved ejection fraction (n=21) and HFrEF (n=35). CMD was invasively assessed by continuous intracoronary thermodilution and defined as coronary flow reserve <2.5. Left ventricular and left anterior descending artery-related myocardial mass was quantified by echocardiography and coronary computed tomography angiography. Myocardial perfusion (mL/min per g) was calculated as the ratio between absolute coronary flow and left anterior descending artery-related mass.

RESULTS

Patients with HFrEF showed a higher left ventricular and left anterior descending artery-related myocardial mass compared with HF with preserved ejection fraction (P<0.010). Overall, 52% of the study population had CMD, with a similar prevalence between the 2 groups. In HFrEF, CMD was characterized by lower absolute microvascular resistance and higher absolute coronary flow at rest (functional CMD; P=0.002). CMD was an independent predictor of a lower rate of left ventricular reverse remodeling at follow-up. In patients with HF with preserved ejection fraction, CMD was mainly due to higher absolute microvascular resistance and lower absolute coronary flow during hyperemia (structural CMD; P≤0.030).

CONCLUSIONS

Continuous intracoronary thermodilution allows the definition and characterization of patterns with distinct CMD in patients with HF and could identify patients with HFrEF with a higher rate of left ventricular reverse remodeling at follow-up.

Global Longitudinal Strain as Predictor of Inducible Ischemia in No Obstructive Coronary Artery Disease in the CIAO-ISCHEMIA Study

BACKGROUND

Global longitudinal strain (GLS) is a sensitive marker for identifying subclinical myocardial dysfunction in obstructive coronary artery disease (CAD). Little is known about the relationship between GLS and ischemia in patients with myocardial ischemia and no obstructive CAD (INOCA).

OBJECTIVES

To investigate the relationship between resting GLS and ischemia on stress echocardiography (SE) in patients with INOCA.

METHODS

Left ventricular GLS was calculated offline on resting SE images at enrollment (n = 144) and 1-year follow-up (n = 120) in the CIAO-ISCHEMIA (Changes in Ischemia and Angina over One year in International Study of Comparative Health Effectiveness with Medical and Invasive Approaches trial screen failures with no obstructive CAD on computed tomography [CT] angiography) study, which enrolled participants with moderate or severe ischemia by local SE interpretation (≥3 segments with new or worsening wall motion abnormality and no obstructive (<50% stenosis) on coronary computed tomography angiography.

RESULTS

Global longitudinal strain values were normal in 83.3% at enrollment and 94.2% at follow-up. Global longitudinal strain values were not associated with a positive SE at enrollment (GLS = -21.5% positive SE vs GLS = -19.9% negative SE, P = .443) or follow-up (GLS = -23.2% positive SE vs GLS = -23.1% negative SE, P = .859). Significant change in GLS was not associated with positive SE in follow-up (P = .401). Regional strain was not associated with colocalizing ischemia at enrollment or follow-up. Changes in GLS and number of ischemic segments from enrollment to follow-up showed a modest but not clinically meaningful correlation (β = 0.41; 95% CI, 0.16, 0.67; P = .002).

CONCLUSIONS

In this cohort of INOCA patients, resting GLS values were largely normal and did not associate with the presence, severity, or location of stress-induced ischemia. These findings may suggest the absence of subclinical myocardial dysfunction detectable by echocardiographic strain analysis at rest in INOCA.

Low-dose exercise protects the heart against established myocardial infarction via IGF-1-upregulated CTRP9 in male mice

Regular exercise is recommended as an important component of therapy for cardiovascular diseases in clinical practice. However, there are still major challenges in prescribing an optimized exercise regimen to individual patients with established cardiac disease. Here, we tested the effects of different exercise doses on cardiac function in mice with established myocardial infarction (MI). Exercise was introduced to mice with MI after 4 weeks of surgery. Low-dose exercise (15 min/day for 8 weeks) improved mortality and cardiac function by increasing 44.39% of ejection fractions while inhibiting fibrosis by decreasing 37.74% of distant region. Unlike higher doses of exercise, low-dose exercise consecutively upregulated cardiac expression of C1q complement/tumor necrosis factor-associated protein 9 (CTRP9) during exercise (>1.5-fold). Cardiac-specific knockdown of CTRP9 abolished the protective effects of low-dose exercise against established MI, while cardiac-specific overexpression of CTRP9 protected the heart against established MI. Mechanistically, low-dose exercise upregulated the transcription factor nuclear receptor subfamily 2 group F member 2 by increasing circulating insulin-like growth factor 1 (IGF-1), therefore, upregulating cardiac CTRP9 expression. These results suggest that low-dose exercise protects the heart against established MI via IGF-1-upregulated CTRP9 and may contribute to the development of optimized exercise prescriptions for patients with MI.

Primary versus iatrogenic (post-PCI) coronary microvascular dysfunction: a wire-based multimodal comparison

BACKGROUND

Although there are studies examining each one separately, there are no data in the literature comparing the magnitudes of the iatrogenic, percutaneous coronary intervention (PCI)-induced, microvascular dysfunction (Type-4 CMD) and coronary microvascular dysfunction (CMD) in the setting of ischaemia in non-obstructed coronary arteries (INOCA) (Type-1 CMD).

OBJECTIVES

We aimed to compare the characteristics of Type-1 and Type-4 CMD subtypes using coronary haemodynamic (resistance and flow-related parameters), thermodynamic (wave energy-related parameters) and hyperemic ECG changes.

METHODS

Coronary flow reserve (CFR) value of <2.5 was defined as CMD in both groups. Wire-based multimodal perfusion markers were comparatively analysed in 35 patients (21 INOCA/CMD and 14 CCS/PCI) enrolled in NCT05471739 study.

RESULTS

Both groups had comparably blunted CFR values per definition (2.03±0.22 vs 2.11±0.37; p: 0.518) and similar hyperemic ST shift in intracoronary ECG (0.16±0.09 vs 0.18±0.07 mV; p: 0.537). While the Type-1 CMD was characterised with impaired hyperemic blood flow acceleration (46.52+12.83 vs 68.20+28.63 cm/s; p: 0.017) and attenuated diastolic microvascular decompression wave magnitudes (p=0.042) with higher hyperemic microvascular resistance (p<0.001), Type-4 CMD had blunted CFR mainly due to higher baseline flow velocity due to post-occlusive reactive hyperemia (33.6±13.7 vs 22.24±5.3 cm/s; p=0.003).

CONCLUSIONS

The perturbations in the microvascular milieu seen in CMD in INOCA setting (Type-1 CMD) seem to be more prominent than that of seen following elective PCI (Type-4 CMD), although resulting reversible ischaemia is equally severe in the downstream myocardium.

Coronary microvascular dysfunction and heart failure with preserved ejection fraction: what are the mechanistic links?

PURPOSE OF REVIEW

Heart failure with preserved ejection fraction (HFpEF) accounts for half of all heart failure presentations and is associated with a dismal prognosis. HFpEF is an umbrella term that constitutes several distinct pathophysiological entities. Coronary microvascular dysfunction (CMD), defined as the inability of the coronary vasculature to augment blood flow adequately in the absence of epicardial coronary artery disease, is highly prevalent amongst the HFpEF population and likely represents one distinct HFpEF endotype, the CMD-HFpEF endotype. This review appraises recent studies that have demonstrated an association between CMD and HFpEF with an aim to understand the pathophysiological links between the two. This is of significant clinical relevance as better understanding of the pathophysiology underlying CMD-HFpEF may result in more targeted and efficacious therapeutic options in this patient cohort.

RECENT FINDINGS

There is a high prevalence of CMD, diagnosed invasively or noninvasively, in patients with HFpEF. Patients with HFpEF who have an impaired myocardial perfusion reserve (MPR) have a worse outcome than those with a normal MPR. Both MPR and coronary flow reserve (CFR) are associated with measures of left ventricular diastolic function and left ventricular filling pressures during exercise. Impaired lusitropy and subendocardial ischaemia link CMD and HFpEF mechanistically.

SUMMARY

CMD-HFpEF is a prevalent endotype of HFpEF and one that is associated with adverse cardiovascular prognosis. Whether CMD leads to HFpEF, through subendocardial ischaemia, or whether it is secondary to the impaired lusitropy that is characteristic of HFpEF is not known. Further mechanistic work is needed to answer this pertinent question.

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.

Invasive Coronary Assessment in Myocardial Ischemia with No Obstructive Coronary Arteries

PURPOSE OF REVIEW

The purpose of this review is threefold: (i) to give an overview of well-established invasive methods for assessing patients with ischemia with no obstructive coronary arteries (INOCA) in the cardiac catheterization laboratory; (ii) to describe the prognostic and treatment implications based on these findings, and (iii) to discuss current knowledge gaps and future perspectives.

RECENT FINDINGS

Recent studies have demonstrated that invasive coronary function testing not only allows for risk stratification of patients with INOCA but also guides medical therapy with improvement in symptoms and quality of life. Based on these findings, invasive coronary function assessment is now a class 2a recommendation in the 2021 ACC/AHA chest pain guideline to improve the diagnosis of coronary microvascular dysfunction and to enhance risk stratification. Invasive functional testing for patients with INOCA is well established and easily performed in the catheterization laboratory. Comprehensive invasive assessment is a key to differentiating INOCA endotypes and optimizing both medical therapy and preventive strategies including lifestyle modification.

Evaluation of left ventricular diastolic function in patients with coronary microvascular dysfunction via cardiovascular magnetic resonance feature tracking

Background

Coronary microvascular dysfunction (CMD) has been suggested to be one of the pathologic mechanisms contributing to heart failure with preserved left ventricular ejection fraction (LVEF) and left ventricular (LV) diastolic dysfunction. We therefore aimed to evaluate LV diastolic function in patients with CMD using cardiovascular magnetic resonance feature tracking (CMR-FT).

Methods

We prospectively enrolled 115 patients referred to cardiology clinics for chest pain assessment who subsequently underwent coronary computed tomography angiogram and stress perfusion CMR. CMD was defined as the presence of subendocardial inducible ischemia detected through visual assessment. LV diastolic function was evaluated using CMR-derived volume-time curves and CMR-FT parameters. The former included early peak filling rate (PFR) and time to PFR; the latter included LV global/regional peak longitudinal diastolic strain rate (LDSR), circumferential diastolic strain rate (CDSR), and radial diastolic strain rate (RDSR).

Results

A total of 92 patients with 1,312 segments were eventually included. Of these, 19 patients were classified as non-CMD (48.8±11.2 years; 63.2% male) and 73 as with CMD (52.3±11.9 years; 54.8% male). The LVEFs were similar and preserved in both groups (P=0.266). At the per-patient level, no differences were observed in PFR, time to PFR, or LV global diastolic strain rates between the two groups. At the per-segment level, 51% (665/1,312) of the myocardial segments were classified as CMD, whereas 49% (647/1,312) were classified as non-CMD. CMD segments showed significantly lower regional CDSR (P=0.019) and RDSR (P=0.006) compared with non-CMD segments.

Conclusions

Despite normal LV ejection fraction in CMD patients, decreased LV diastolic function in CMD myocardial segments indicates early diastolic impairment.

Fully automated pixel-wise quantitative CMR-myocardial perfusion with CMR-coronary angiography to detect hemodynamically significant coronary artery disease

OBJECTIVES

We applied a fully automated pixel-wise post-processing framework to evaluate fully quantitative cardiovascular magnetic resonance myocardial perfusion imaging (CMR-MPI). In addition, we aimed to evaluate the additive value of coronary magnetic resonance angiography (CMRA) to the diagnostic performance of fully automated pixel-wise quantitative CMR-MPI for detecting hemodynamically significant coronary artery disease (CAD).

METHODS

A total of 109 patients with suspected CAD were prospectively enrolled and underwent stress and rest CMR-MPI, CMRA, invasive coronary angiography (ICA), and fractional flow reserve (FFR). CMRA was acquired between stress and rest CMR-MPI acquisition, without any additional contrast agent. Finally, CMR-MPI quantification was analyzed by a fully automated pixel-wise post-processing framework.

RESULTS

Of the 109 patients, 42 patients had hemodynamically significant CAD (FFR ≤ 0.80 or luminal stenosis ≥ 90% on ICA) and 67 patients had hemodynamically non-significant CAD (FFR ˃ 0.80 or luminal stenosis < 30% on ICA) were enrolled. On the per-territory analysis, patients with hemodynamically significant CAD had higher myocardial blood flow (MBF) at rest, lower MBF under stress, and lower myocardial perfusion reserve (MPR) than patients with hemodynamically non-significant CAD (p < 0.001). The area under the receiver operating characteristic curve of MPR (0.93) was significantly larger than those of stress and rest MBF, visual assessment of CMR-MPI, and CMRA (p < 0.05), but similar to that of the integration of CMR-MPI with CMRA (0.90).

CONCLUSIONS

Fully automated pixel-wise quantitative CMR-MPI can accurately detect hemodynamically significant CAD, but the integration of CMRA obtained between stress and rest CMR-MPI acquisition did not provide significantly additive value.

KEY POINTS

• Full quantification of stress and rest cardiovascular magnetic resonance myocardial perfusion imaging can be postprocessed fully automatically, generating pixel-wise myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) maps. • Fully quantitative MPR provided higher diagnostic performance for detecting hemodynamically significant coronary artery disease, compared with stress and rest MBF, qualitative assessment, and coronary magnetic resonance angiography (CMRA). • The integration of CMRA and MPR did not significantly improve the diagnostic performance of MPR alone.

Comprehensive Management of ANOCA, Part 1-Definition, Patient Population, and Diagnosis: JACC State-of-the-Art Review

Angina with nonobstructive coronary arteries (ANOCA) is increasingly recognized and may affect nearly one-half of patients undergoing invasive coronary angiography for suspected ischemic heart disease. This working diagnosis encompasses coronary microvascular dysfunction, microvascular and epicardial spasm, myocardial bridging, and other occult coronary abnormalities. Patients with ANOCA often face a high burden of symptoms and may experience repeated presentations to multiple medical providers before receiving a diagnosis. Given the challenges of establishing a diagnosis, patients with ANOCA frequently experience invalidation and recidivism, possibly leading to anxiety and depression. Advances in scientific knowledge and diagnostic testing now allow for routine evaluation of ANOCA noninvasively and in the cardiac catheterization laboratory with coronary function testing (CFT). CFT includes diagnostic coronary angiography, assessment of coronary flow reserve and microcirculatory resistance, provocative testing for endothelial dysfunction and coronary vasospasm, and intravascular imaging for identification of myocardial bridging, with hemodynamic assessment as needed.

Unveiling the Enigma: Exploring the Intricate Link Between Coronary Microvascular Dysfunction and Takotsubo Cardiomyopathy

This review article delves into the intricate and evolving relationship between coronary microvascular dysfunction (CMD) and takotsubo cardiomyopathy (TCM), two intriguing cardiovascular conditions increasingly recognised for their potential interplay. We examine their characteristics, shared pathophysiological mechanisms, diagnostic challenges, and management strategies. Emerging evidence suggests a link between microvascular dysfunction and the development of TCM, leading to a deeper exploration of their connection. Accurate diagnosis of both conditions becomes essential, as microvascular dysfunction may modify TCM outcomes. We underscore the significance of understanding this connection for improved patient care, emphasising the need for tailored interventions when CMD and TCM coexist. Collaborative research and heightened clinical awareness are advocated to advance our comprehension of this relationship. Through interdisciplinary efforts, we aim to refine diagnostic precision, develop targeted therapies, and enhance patient outcomes in cardiovascular medicine.

Microvascular resistance reserve: diagnostic and prognostic performance in the ILIAS registry

AIMS

The microvascular resistance reserve (MRR) was introduced as a means to characterize the vasodilator reserve capacity of the coronary microcirculation while accounting for the influence of concomitant epicardial disease and the impact of administration of potent vasodilators on aortic pressure. This study aimed to evaluate the diagnostic and prognostic performance of MRR.

METHODS AND RESULTS

A total of 1481 patients with stable symptoms and a clinical indication for coronary angiography were included from the global ILIAS Registry. MRR was derived as a function of the coronary flow reserve (CFR) divided by the fractional flow reserve (FFR) and corrected for driving pressure. The median MRR was 2.97 [Q1-Q3: 2.32-3.86] and the overall relationship between MRR and CFR was good [correlation coefficient (Rs) = 0.88, P < 0.005]. The difference between CFR and MRR increased with decreasing FFR [coefficient of determination (R2) = 0.34; Coef.-2.88, 95% confidence interval (CI): -3.05--2.73; P < 0.005]. MRR was independently associated with major adverse cardiac events (MACE) at 5-year follow-up [hazard ratio (HR) 0.78; 95% CI 0.63-0.95; P = 0.024] and with target vessel failure (TVF) at 5-year follow-up (HR 0.83; 95% CI 0.76-0.97; P = 0.047). The optimal cut-off value of MRR was 3.0. Based on this cut-off value, only abnormal MRR was significantly associated with MACE and TVF at 5-year follow-up in vessels with functionally significant epicardial disease (FFR <0.75).

CONCLUSION

MRR seems a robust indicator of the microvascular vasodilator reserve capacity. Moreover, in line with its theoretical background, this study suggests a diagnostic advantage of MRR over other indices of vasodilatory capacity in patients with hemodynamically significant epicardial coronary artery disease.

Echocardiographic assessment of primary microvascular angina and primary coronary microvascular dysfunction

There is an increasing interest in the role of echocardiography in the evaluation of primary microvascular angina, which is attributed to primary coronary microvascular dysfunction. Valid echocardiographic techniques are expected to facilitate the diagnosis and follow-up of these patients and would be valuable for research purposes and therapy evaluation. However, adequate echocardiographic data are lacking, and the interpretation of the limited available literature is hindered by the previous addition of microvascular angina under more inclusive entities, such as cardiac syndrome X. In experienced hands, the assessment of primary coronary microvascular dysfunction in patients with suspected primary microvascular angina, using multiple echocardiographic techniques is feasible, relatively inexpensive, and safe. Exclusion of obstructive epicardial coronary artery disease is, however, a prerequisite for diagnosis. Two-dimensional transthoracic echocardiography, routine stress echocardiography, and speckle-tracking echocardiography indirectly assess primary coronary microvascular dysfunction by evaluating potential impairment in myocardial function and lack diagnostic sensitivity and specificity. Conversely, certain echocardiographic techniques, including Doppler-derived coronary flow velocity reserve and myocardial contrast echocardiography, assess some coronary microvascular dysfunction parameters and have exhibited diagnostic and prognostic potentials. Doppler-derived coronary flow velocity reserve is the best studied and only guideline-approved echocardiographic technique for documenting coronary microvascular dysfunction in patients with suspected microvascular angina. Myocardial contrast echocardiography, by comparison, can detect heterogeneous and patchy myocardial involvement by coronary microvascular dysfunction, which is an advantage over the common practice of coronary flow velocity reserve assessment in a single vessel (commonly the left anterior descending artery) which only reflects regional microvascular function. However, there is no consensus regarding the diagnostic criteria, and expertise performing this technique is limited. Echocardiography remains underexplored and inadequately utilized in the setting of microvascular angina and coronary microvascular dysfunction. Appraisal of the current echocardiographic literature regarding coronary microvascular dysfunction and microvascular angina is important to stay current with the progress in its clinical recognition and create a basis for future research and technological advancements.

Practical Approach for Angina and Non-Obstructive Coronary Arteries: A State-of-the-Art Review

Anginal symptoms are frequently encountered in patients without the presence of significant obstructive coronary artery disease (CAD). It is increasingly recognized that vasomotor disorders, such as an abnormal vasodilatory capacity of the coronary microcirculation or coronary vasospasm, are the dominant pathophysiological substrate in these patients. Although the evidence with respect to angina in patients with non-obstructive coronary arteries is accumulating, the diagnosis and treatment of these patients remains challenging. In this review, we aimed to provide a comprehensive overview regarding the pathophysiological origins of angina with non-obstructive coronary arteries disorders and its diagnostic and therapeutic considerations. Hereby, we provide a practical approach for the management of patents with angina and non-obstructive CAD.

Development of artificial intelligence tools for invasive Doppler-based coronary microvascular assessment

Aims

Coronary flow reserve (CFR) assessment has proven clinical utility, but Doppler-based methods are sensitive to noise and operator bias, limiting their clinical applicability. The objective of the study is to expand the adoption of invasive Doppler CFR, through the development of artificial intelligence (AI) algorithms to automatically quantify coronary Doppler quality and track flow velocity.

Methods and results

A neural network was trained on images extracted from coronary Doppler flow recordings to score signal quality and derive values for coronary flow velocity and CFR. The outputs were independently validated against expert consensus. Artificial intelligence successfully quantified Doppler signal quality, with high agreement with expert consensus (Spearman's rho: 0.94), and within individual experts. Artificial intelligence automatically tracked flow velocity with superior numerical agreement against experts, when compared with the current console algorithm [AI flow vs. expert flow bias -1.68 cm/s, 95% confidence interval (CI) -2.13 to -1.23 cm/s, P < 0.001 with limits of agreement (LOA) -4.03 to 0.68 cm/s; console flow vs. expert flow bias -2.63 cm/s, 95% CI -3.74 to -1.52, P < 0.001, 95% LOA -8.45 to -3.19 cm/s]. Artificial intelligence yielded more precise CFR values [median absolute difference (MAD) against expert CFR: 4.0% for AI and 7.4% for console]. Artificial intelligence tracked lower-quality Doppler signals with lower variability (MAD against expert CFR 8.3% for AI and 16.7% for console).

Conclusion

An AI-based system, trained by experts and independently validated, could assign a quality score to Doppler traces and derive coronary flow velocity and CFR. By making Doppler CFR more automated, precise, and operator-independent, AI could expand the clinical applicability of coronary microvascular assessment.

Illness Perception and the Impact of a Definitive Diagnosis on Women With Ischemia and No Obstructive Coronary Artery Disease: A Qualitative Study

BACKGROUND

Ischemia and no obstructive coronary artery disease (INOCA) disproportionately impacts women, yet the underlying pathologies are often not distinguished, contributing to adverse health care experiences and poor quality of life. Coronary function testing at the time of invasive coronary angiography allows for improved diagnostic accuracy. Despite increased recognition of INOCA and expanding access to testing, data lack on first-person perspectives and the impact of receiving a diagnosis in women with INOCA.

METHODS

From 2020 to 2021, we conducted structured telephone interviews with 2 groups of women with INOCA who underwent invasive coronary angiography (n=29) at Yale New Haven Hospital, New Haven, CT: 1 group underwent coronary function testing (n=20, of whom 18 received a mechanism-based diagnosis) and the other group who did not undergo coronary function testing (n=9). The interviews were analyzed using the constant comparison method by a multidisciplinary team.

RESULTS

The mean age was 59.7 years, and 79% and 3% were non-Hispanic White and non-Hispanic Black, respectively. Through iterative coding, 4 themes emerged and were further separated into subthemes that highlight disease experience aspects to be addressed in patient care: (1) distress from symptoms of uncertain cause: symptom constellation, struggle for sensemaking, emotional toll, threat to personal and professional identity; (2) a long journey to reach a definitive diagnosis: self-advocacy and fortitude, healthcare interactions brought about further uncertainty and trauma, therapeutic alliance, sources of information; (3) establishing a diagnosis enabled a path forward: relief and validation, empowerment; and (4) commitment to promoting awareness and supporting other women: recognition of sex and racial/ethnic disparities, support for other women.

CONCLUSIONS

Insights about how women experience the symptoms of INOCA and their interactions with clinicians and the healthcare system hold powerful lessons for more patient-centered care. A coronary function testing-informed diagnosis greatly influences the healthcare experiences, quality of life, and emotional states of women with INOCA.

Haemodynamic and metabolic adaptations in coronary microvascular disease

OBJECTIVE

We aimed to evaluate the microcirculatory resistance (MR) and myocardial metabolic adaptations at rest and in response to increased cardiac workload in patients with suspected coronary microvascular dysfunction (CMD).

METHODS

Patients with objective ischaemia and/or myocardial injury and non-obstructive coronary artery disease underwent thermodilution-derived microcirculatory assessment and transcardiac blood sampling during graded exercise with adenosine-mediated hyperaemia. We measured MR at rest and following supine cycle ergometry. Patients (n=24) were stratified by the resting index of MR (IMR) into normal-IMR (IMR<22U, n=12) and high-IMR groups (IMR≥22U, n=12).

RESULTS

The mean age was 57 years; 67% were males and 38% had hypertension. The normal-IMR group had increased IMR response to exercise (16±5 vs 23±12U, p=0.03) compared with the high-IMR group, who had persistently elevated IMR at rest and following exercise (38±19 vs 33±15U, p=0.39) despite similar exercise duration and rate-pressure product between the groups, both p>0.05. The normal-IMR group had augmented oxygen extraction ratio following exercise (53±18 vs 64±11%, p=0.03) compared with the high-IMR group (65±14 vs 59±11%, p=0.26). The postexercise lactate uptake was greater in the high-IMR (0.04±0.05 vs 0.11±0.07 mmol/L, p=0.004) compared with normal-IMR group (0.08±0.06 vs 0.09±0.09 mmol/L, p=0.67). The high-IMR group demonstrated greater troponin release following exercise compared with the normal-IMR group (0.13±0.12 vs 0.001±0.05 ng/L, p=0.03).

CONCLUSIONS

Patients with suspected CMD appear to have distinctive microcirculatory resistive and myocardial metabolic profiles at rest and in response to exercise. These differences in phenotypes may permit individualised therapies targeting microvascular responsiveness (normal-IMR group) and/or myocardial metabolic adaptations (normal-IMR and high-IMR groups).

Coronary microvascular dysfunction and cardiovascular disease: Pathogenesis, associations and treatment strategies

Coronary microvascular dysfunction (CMD) is a high-risk factor for a variety of cardiovascular events. Due to its complex aetiology and concealability, knowledge of the pathophysiological mechanism of CMD is still limited at present, which greatly restricts its clinical diagnosis and treatment. Studies have shown that CMD is closely related to a variety of cardiovascular diseases, can aggravate the occurrence and development of cardiovascular diseases, and is closely related to a poor prognosis in patients with cardiovascular diseases. Improving coronary microvascular remodelling and increasing myocardial perfusion might be promising strategies for the treatment of cardiovascular diseases. In this paper, the pathogenesis and functional assessment of CMD are reviewed first, along with the relationship of CMD with cardiovascular diseases. Then, the latest strategies for the treatment of CMD and cardiovascular diseases are summarized. Finally, urgent scientific problems in CMD and cardiovascular diseases are highlighted and future research directions are proposed to provide prospective insights for the prevention and treatment of CMD and cardiovascular diseases in the future.

Coronary Microvascular Disease in Contemporary Clinical Practice

Coronary microvascular disease (CMD) causes myocardial ischemia in a variety of clinical scenarios. Clinical practice guidelines support routine testing for CMD in patients with ischemia with nonobstructive coronary artery disease. Invasive testing to identify CMD requires Doppler or thermodilution measures of flow to determine the coronary flow reserve and measures of microvascular resistance. Acetylcholine coronary reactivity testing identifies concomitant endothelial dysfunction, microvascular spasm, or epicardial coronary spasm. Comprehensive testing may improve symptoms, quality of life, and patient satisfaction by establishing a diagnosis and guiding-targeted medical therapy and lifestyle measures. Beyond ischemia with nonobstructive coronary artery disease, testing for CMD may play a role in patients with acute myocardial infarction, angina following coronary revascularization, heart failure with preserved ejection fraction, Takotsubo syndrome, and after heart transplantation. Additional education and provider awareness of CMD and its role in cardiovascular disease is needed to improve patient-centered outcomes of ischemic heart disease.

The Impact of Trimethylamine N-Oxide and Coronary Microcirculatory Dysfunction on Outcomes following ST-Elevation Myocardial Infarction

INTRODUCTION

Persistent coronary microcirculatory dysfunction (CMD) and elevated trimethylamine N-oxide (TMAO) levels after ST-elevation myocardial infarction (STEMI) may drive negative structural and electrical cardiac remodeling, resulting in new-onset atrial fibrillation (AF) and a decrease in left ventricular ejection fraction (LVEF).

AIMS

TMAO and CMD are investigated as potential predictors of new-onset AF and left ventricular remodeling following STEMI.

METHODS

This prospective study included STEMI patients who had primary percutaneous coronary intervention (PCI) followed by staged PCI three months later. Cardiac ultrasound images were obtained at baseline and after 12 months to assess LVEF. Coronary flow reserve (CFR), and index of microvascular resistance (IMR) were assessed using the coronary pressure wire during the staged PCI. Microcirculatory dysfunction was defined as having an IMR value ≥25 U and CFR value <2.5 U.

RESULTS

A total of 200 patients were included in the study. Patients were categorized according to whether or not they had CMD. Neither group differed from the other with regards to known risk factors. Despite making up only 40.5% of the study population, females represented 67.4% of the CMD group p < 0.001. Similarly, CMD patients had a much higher prevalence of diabetes than those without CMD (45.7% vs. 18.2%; p < 0.001). At the one-year follow-up, the LVEF in the CMD group had decreased to significantly lower levels than those in the non-CMD group (40% vs. 50%; p < 0.001), whereas it had been higher in the CMD group at baseline (45% vs. 40%; p = 0.019). Similarly, during the follow-up, the CMD group had a greater incidence of AF (32.6% vs. 4.5%; p < 0.001). In the adjusted multivariable analysis, the IMR and TMAO were associated with increased odds of AF development (OR: 1.066, 95% CI: 1.018-1.117, p = 0.007), and (OR: 1.290, 95% CI: 1.002-1.660, p = 0.048), respectively. Similarly, elevated levels of IMR and TMAO were linked with decreased odds of LVEF improvement, while higher CFR values are related to a greater likelihood of LVEF improvement.

CONCLUSIONS

CMD and elevated TMAO levels were highly prevalent three months after STEMI. Patients with CMD had an increased incidence of AF and a lower LVEF 12 months after STEMI.

Abnormal left ventricular subendocardial perfusion and diastolic function in women with obesity and heart failure and preserved ejection fraction

PURPOSE

- Coronary microvascular dysfunction (CMD) is common in patients with heart failure with preserved ejection fraction (HFpEF) and obesity. Stress cardiovascular magnetic resonance (CMR) has been proposed as a non-invasive tool for detection of CMD. The aim of this study was to determine relationship between CMD and diastolic function in patients with HFpEF using a novel CMR technique.

METHODS

- Patients with obesity and HFpEF without epicardial coronary artery disease (CAD) underwent Doppler echocardiography to measure diastolic function, followed by vasodilator stress CMR, using a single bolus, dual sequence, quantitative myocardial perfusion mapping to measure myocardial blood flow (MBF) at rest and at peak hyperemia. With this, myocardial perfusion reserve (MPR), global stress endocardial-to-epicardial (endo:epi) perfusion ratio, and total ischemic burden (IB, defined as myocardial segments with MBF < 1.94 mL/min/g) were calculated. Results are reported as median and interquartile range.

RESULTS

- Nineteen subjects were enrolled (100% female, 42% Black). Median age was 64 [56-72] years. Global stress MBF was 2.43 ml/min/g [2.16-2.78] and global myocardial perfusion reserve (MPR) was 2.34 [2.07-2.88]. All had an abnormal subendocardial perfusion with an endo:epi of less than 1 (0.87 [0.81-0.90]). Regional myocardial hypoperfusion was detected in 14 (74%) patients with an IB of 6% [0-34.4]. Endo:epi ratio significantly correlated with IB (R=-0.510, p = 0.026) and measures of diastolic function (R = 0.531, p = 0.019 and R=-0.544, p = 0.014 for e' and E/e' respectively).

CONCLUSION

- Using a novel quantitative stress CMR myocardial perfusion mapping technique, women with obesity and HFpEF were found to have patterns of abnormal subendocardial perfusion which significantly correlated with measures of diastolic dysfunction.

Invasive Detection of Coronary Microvascular Dysfunction: How It Began, and Where We Are Now

The landscape of interventional cardiology is ever evolving. Contemporary practice has shifted from a stenosis-centred approach to the total characterisation of both the epicardial and microcirculatory vessels. Microcirculatory dysfunction plays an important role in the pathophysiology of acute and chronic coronary syndromes, and characterisation of the microcirculation has important clinical consequences. Accordingly, the invasive diagnosis of microcirculatory dysfunction is becoming a key feature of the interventional cardiologist's toolkit. This review focuses on the methodology underpinning the invasive diagnosis of microvascular dysfunction and highlights the indices that have arisen from these methodologies.

Influence of fasting plasma glucose-lowering rate on BNP levels in type 2 diabetes mellitus patients with coronary microcirculation dysfunction

AIM

The aim was to analyze the influence of fasting plasma glucose-lowering rate (FPGLR) on plasma BNP levels in type 2 diabetes mellitus (T2DM) patients with coronary microcirculation dysfunction (CMD) and to determine the optimal FPGLR for these patients.

METHODS

A total of 170 T2DM patients who received intensive glucose-lowering therapy during hospitalization in the First Affiliated Hospital of Harbin Medical University were enrolled. Ninety-two patients with CMD and 78 patients without CMD were assigned to a study and a control group, respectively. The study group was stratified as S1 (4.1 ~ 6.0 mmol·L^-1·day^-1), S2 (2.1 ~ 4.0 mmol·L^-1·day^-1), and S3 (≤ 2.0 mmol·L^-1·day^-1) by different FPGLR, and the same in the control group (C1, C2, and C3). The plasma BNP levels with the same FPGLR were compared between the study and the control group, and patients with a different FPGLR in the study group were also compared.

RESULTS

In the study and the control group, the BNP level in S1 was significantly higher than that in C1 (87 vs. 12 pg/ml, P < 0.001), although there was no significant difference between S2 and C2, S3 and C3. In the study group, the BNP level in S1 was significantly higher than that in S2 (87 vs. 22 pg/ml, P < 0.001) and S3 (87 vs. 15 pg/ml, P < 0.001), but there was no significant difference between S2 and S3.

CONCLUSION

Rapid intensive glucose-lowering may lead to increased plasma BNP levels in T2DM patients with CMD. Optimal FPGLR for these patients was determined to be no more than 4.0 mmol·L^-1·day^-1.

Positive Stress Electrocardiography in Patients With Non-obstructive Coronary Disease

Introduction The episodes of myocardial ischemia in patients with non-obstructive coronary disease are extremely variable in provoking factors and presentation. Purpose We investigated the significance of coronary blood flow velocity and epicardial diameter as correlates of a positive electrocardiographic exercise stress test (ExECG) in hospitalized patients with unstable angina and non-obstructive coronary artery disease. Methods The study was a single-center cohort retrospective. ExECG was performed and analyzed in a group of 79 patients with non-obstructive coronary disease (coronary stenoses < 50%). Thirty-one percent of the patients (n=25) were diagnosed with slow coronary flow phenomenon, SCFP; 40.5% (n=32) - patients with hypertensive disease, left ventricular hypertrophy (LVH), and slow epicardial flow; 27.8% (n=22) with hypertension, left ventricular hypertrophy and normal coronary flow. The patients were hospitalized in University Hospital "Alexandrovska," Sofia in the period 2006-2008. Results The frequency of positive ExECG is increased as a trend was associated with smaller epicardial diameters and pronounced delay in epicardial coronary flow. In the subgroup with SCFP, the risk for a positive ExECG test was determined by slower coronary flow (36.5±7.7 frames vs. 30.3±4.4 frames, p=0.044) and borderline significant by epicardial lumen diameters (3.3±0.8 mm vs. 4.1±1.0 mm, p=0.051) and greater myocardial mass (92.8±12.6 g/m² vs. 82.9±8.6 g/m², p=0.054). In cases of left ventricular hypertrophy, which included both patients with the normal and slow epicardial flow, there were no statistically significant correlates of an abnormal exercise stress ECG test. Conclusions In patients with non-obstructive coronary atherosclerosis and predominantly slow epicardial coronary flow, the provoking of ischemia at an electrocardiographic exercise stress test is associated with the lower epicardial flow velocity at rest and with the smaller epicardial diameter. In SCFP, the risk for an abnormal stress test is determined by slower coronary flow, smaller epicardial lumen diameter, and greater myocardial mass. The presence and size of the plaque burden are not associated with a greater risk of a positive ExECG in these patients.

Diagnostic performance of exercise stress tests for detection of epicardial and microvascular coronary artery disease: the UZ Clear study

BACKGROUND

Cardiac stress tests remain the cornerstone for evaluating patients suspected of having obstructive coronary artery disease (CAD). Coronary microvascular dysfunction (CMD) can lead to abnormal non-invasive tests.

AIMS

We sought to assess the diagnostic performance of exercise stress tests with indexes of epicardial and microvascular resistance as reference.

METHODS

This was a prospective, single-arm, multicentre study of patients with an intermediate pretest probability of CAD and positive exercise stress tests who were referred for invasive angiography. Patients underwent an invasive diagnostic procedure (IDP) with measurement of fractional flow reserve (FFR) and index of microvascular resistance (IMR) in at least one coronary vessel. Obstructive CAD was defined as diameter stenosis (DS) >50% by quantitative coronary angiography (QCA). The objective was to determine the false discovery rate (FDR) of cardiac exercise stress tests with both FFR and IMR as references.

RESULTS

One hundred and seven patients (137 vessels) were studied. The mean age was 62.1±8.7, and 27.1% were female. The mean diameter stenosis was 37.2±27.5%, FFR was 0.84±0.10, coronary flow reserve was 2.74±2.07, and IMR 20.3±11.9. Obstructive CAD was present in 39.3%, whereas CMD was detected in 20.6%. The FDR was 60.7% and 62.6% with QCA and FFR as references (p-value=0.803). The combination of FFR and IMR as clinical reference reduced the FDR by 25% compared to QCA (45.8% vs 60.7%; p-value=0.006).

CONCLUSIONS

In patients with evidence of ischaemia, an invasive functional assessment accounting for the epicardial and microvascular compartments led to an improvement in the diagnostic performance of exercise tests, driven by a significant FDR reduction.

Heart failure with preserved ejection fraction: the role of microvascular dysfunction

Aim. To evaluate the relationship between coronary microvascular dysfunction (CMD), biomarkers of cardiac fibrosis and cardiac remodeling (soluble ST2 (sST2), fibroblast growth factor-23 (FGF-23), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and NT-proBNP), parameters of diastolic dysfunction (DD), and the presence of heart failure with preserved ejection fraction (HFpEF) in symptomatic patients.

Materials and methods. Study participants were 59 patients with non-obstructive coronary artery disease (CAD) and preserved left ventricular ejection fraction (LVEF) of 62 (56; 67) %. Non-obstructive CAD was verified by coronary computed tomography angiography. Stress-and rest-myocardial blood flow (MBF) and coronary flow reserve (CFR) parameters were evaluated by CZT SPECT. Serum levels of cardiac biomarkers were measured by the enzyme immunoassay. Two-dimensional transthoracic echocardiography was used to assess DD parameters.

Results. Decreased CFR was defined as CFR ≤ 2. Therefore, CMD was defined as the presence of decreased CFR in the absence of flow-limiting CAD. Distribution of patients was performed by CFR values: group 1 included patients with preserved CFR (>2, n = 35), and group 2 encompassed patients with decreased CFR (≤2, n = 24). In 87.5% of cases, patients with CMD were diagnosed with HFpEF, whereas in patients with preserved CFR, heart failure was diagnosed only in 51.4% of cases (p < 0.0001). CFR values were correlated with the left atrial volume (r = –0.527; p = 0.001), E / A ratio (r = –0.321, p = 0.012), and E / e’ (r = –0.307; p = 0.021). Following the ROC analysis, the levels of sST2 ≥ 31.304 ng / ml (AUС = 0.730; р = 0.004) and NT-proBNP ≥ 0.034 pg / ml (AUС = 0.815; р = 0.034) were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Conclusion. The obtained data suggest that CMD may play an essential role in HFpEF. The values of CFR were correlated with DD parameters, and decreased CFR was associated with overexpression of biomarkers of cardiac fibrosis and cardiac remodeling. Serum levels of sST2 and NT-proBNP were identified as cut-off values for the presence of CMD in patients with non-obstructive CAD.

Reference values for intracoronary Doppler flow velocity-derived hyperaemic microvascular resistance index

BACKGROUND

Invasive assessments of microvascular function are rapidly becoming an integral part of physiological assessment in chronic coronary syndromes.

OBJECTIVE

We aimed to establish a reference range for Doppler flow velocity-derived hyperaemic microvascular resistance index (HMR) in a cohort of angina with no significant epicardial coronary obstruction (ANOCA) patients with no structural pathophysiological alterations in the coronary circulation.

METHODS

The reference population consisted of ANOCA patients undergoing invasive coronary vasomotor function assessment who had a coronary flow reserve (CFR) >2.5, and had either (1) tested negatively for spasm provocation (n = 12) or (2) tested positively with only angina at rest (n = 29). A reference range for HMR was established using a non-parametric method and correlations with clinical characteristics were determined using a spearman rank correlation analysis.

RESULTS

In 41 patients median HMR amounted to 1.6 mmHg/cm/s [Q1, Q3: 1.3, 2.2 mmHg/cm/s]. The reference range for HMR that is applicable to 95% of the population was 0.8 mmHg/cm/s (90% CI: 0.8-1.0 mmHg/cm/s) to 2.7 mmHg/cm/s (90% CI: 2.6-2.7 mmHg/cm/s). No significant correlations were found between HMR and clinical characteristics.

CONCLUSION

In this reference population undergoing invasive coronary vasomotor function testing, the 90% confidence interval of the HMR upper limit of normal ranges from 2.6 to 2.7 mmHg/cm/s. A > 2.5 mmHg/cm/s HMR threshold can be used to identify abnormal microvascular resistance in daily clinical practice.

Epicardial atherosclerosis and coronary tortuosity in patients with acetylcholine-induced coronary spasm

BACKGROUND

Angina pectoris in the absence of relevant epicardial stenoses is frequently caused by coronary spasm. This mechanism of angina is common yet underdiagnosed in daily clinical practice. The pathophysiology of coronary spasm is complex, multifactorial, and not completely understood. The purpose of this study was to analyze the relationship between macroscopic coronary morphologies and coronary spasm.

METHODS

Epicardial atherosclerosis, coronary vessel tortuosity, coronary aneurysms, and myocardial bridges were analyzed angiographically in 610 patients and a potential association with the result of an intracoronary acetylcholine (ACh) provocation test was investigated.

RESULTS

The comparison showed that angiographic morphologic variations in the coronary arteries are related to the occurrence of coronary spasm. We observed a strong association between the presence of epicardial atherosclerosis and epicardial spasm [87 patients of 179 with epicardial spasm had epicardial atherosclerosis (49%) vs. 45 patients of 172 with microvascular spasm (26%) vs. 89 patients of 259 with negative/inconclusive ACh test (36%); P < 0.005]. Moreover, we found a higher frequency of coronary tortuosity in patients with microvascular spasm [99 patients of 172 with microvascular spasm had at least moderate coronary tortuosity (58%) vs. 76 patients of 179 with epicardial spasm (43%) vs. 126 patients of 259 with negative/inconclusive ACh test (49%); P = 0.017]. Multivariable analysis revealed epicardial atherosclerosis (<50% stenosis) on coronary angiography as a predictor for epicardial spasm (OR, 2.096; 95% CI, 1.467-2.995; P < 0.0005). Female sex (OR, 5.469; 95% CI, 3.433-8.713; P < 0.0005), and exertional angina (OR, 2.411; 95% CI, 1.597-3.639; P < 0.0005) were predictors of microvascular spasm in multivariable analysis.

CONCLUSION

In angina patients with no obstructive coronary artery disease, epicardial atherosclerosis is associated with ACh-induced epicardial coronary spasm. Moreover, coronary microvascular spasm is more prevalent in female patients and those with exertional angina. Our results provide insights into the relationship between coronary morphology and coronary vasomotor function.

AI-AIF: artificial intelligence-based arterial input function for quantitative stress perfusion cardiac magnetic resonance

Aims

One of the major challenges in the quantification of myocardial blood flow (MBF) from stress perfusion cardiac magnetic resonance (CMR) is the estimation of the arterial input function (AIF). This is due to the non-linear relationship between the concentration of gadolinium and the MR signal, which leads to signal saturation. In this work, we show that a deep learning model can be trained to predict the unsaturated AIF from standard images, using the reference dual-sequence acquisition AIFs (DS-AIFs) for training.

Methods and results

A 1D U-Net was trained, to take the saturated AIF from the standard images as input and predict the unsaturated AIF, using the data from 201 patients from centre 1 and a test set comprised of both an independent cohort of consecutive patients from centre 1 and an external cohort of patients from centre 2 (n = 44). Fully-automated MBF was compared between the DS-AIF and AI-AIF methods using the Mann-Whitney U test and Bland-Altman analysis. There was no statistical difference between the MBF quantified with the DS-AIF [2.77 mL/min/g (1.08)] and predicted with the AI-AIF (2.79 mL/min/g (1.08), P = 0.33. Bland-Altman analysis shows minimal bias between the DS-AIF and AI-AIF methods for quantitative MBF (bias of -0.11 mL/min/g). Additionally, the MBF diagnosis classification of the AI-AIF matched the DS-AIF in 669/704 (95%) of myocardial segments.

Conclusion

Quantification of stress perfusion CMR is feasible with a single-sequence acquisition and a single contrast injection using an AI-based correction of the AIF.

Coronary Slow Flow Is Not Diagnostic of Microvascular Dysfunction in Patients With Angina and Unobstructed Coronary Arteries

Background Guidelines recommend that coronary slow flow phenomenon (CSFP), defined as corrected thrombolysis in myocardial infarction frame count (CTFC) >$$ > $$27, can diagnose coronary microvascular dysfunction (CMD) in patients with angina and nonobstructed coronary arteries. CSFP has also historically been regarded as a sign of coronary endothelial dysfunction (CED). We sought to validate the utility of CTFC, as a binary classifier of CSFP and as a continuous variable, to diagnose CMD and CED. Methods and Results Patients with angina and nonobstructed coronary arteries had simultaneous coronary pressure and flow velocity measured using a dual sensor-tipped guidewire during rest, adenosine-mediated hyperemia, and intracoronary acetylcholine infusion. CMD was defined as the inability to augment coronary blood flow in response to adenosine (coronary flow reserve <2.5) and CED in response to acetylcholine (acetylcholine flow reserve ≤1.5); 152 patients underwent assessment using adenosine, of whom 82 underwent further acetylcholine testing. Forty-six patients (30%) had CSFP, associated with lower flow velocity and higher microvascular resistance as compared with controls (16.5±$$ \pm $$6.9 versus 20.2±$$ \pm $$6.9 cm/s; P=0.001 and 6.26±$$ \pm $$1.83 versus 5.36±$$ \pm $$1.83 mm Hg/cm/s; P=0.009, respectively). However, as a diagnostic test, CSFP had poor sensitivity and specificity for both CMD (26.7% and 65.2%) and CED (21.1% and 56.0%). Furthermore, on receiver operating characteristics analyses, CTFC could not predict CMD or CED (area under the curve, 0.41 [95% CI, 0.32%-0.50%] and 0.36 [95% CI, 0.23%-0.49%], respectively). Conclusions In patients with angina and nonobstructed coronary arteries, CSFP and CTFC are not diagnostic of CMD or CED. Guidelines supporting the use of CTFC in the diagnosis of CMD should be revisited.

Invasive coronary physiology in patients with angina and non-obstructive coronary artery disease: a consensus document from the coronary microvascular dysfunction workstream of the British Heart Foundation/National Institute for Health Research Partnership

Nearly half of all patients with angina have non-obstructive coronary artery disease (ANOCA); this is an umbrella term comprising heterogeneous vascular disorders, each with disparate pathophysiology and prognosis. Approximately two-thirds of patients with ANOCA have coronary microvascular disease (CMD). CMD can be secondary to architectural changes within the microcirculation or secondary to vasomotor dysfunction. An inability of the coronary vasculature to augment blood flow in response to heightened myocardial demand is defined as an impaired coronary flow reserve (CFR), which can be measured non-invasively, using imaging, or invasively during cardiac catheterisation. Impaired CFR is associated with myocardial ischaemia and adverse cardiovascular outcomes.The CMD workstream is part of the cardiovascular partnership between the British Heart Foundation and The National Institute for Health Research in the UK and comprises specialist cardiac centres with expertise in coronary physiology assessment. This document outlines the two main modalities (thermodilution and Doppler techniques) for estimation of coronary flow, vasomotor testing using acetylcholine, and outlines a standard operating procedure that could be considered for adoption by national networks. Accurate and timely disease characterisation of patients with ANOCA will enable clinicians to tailor therapy according to their patients' coronary physiology. This has been shown to improve patients' quality of life and may lead to improved cardiovascular outcomes in the long term.

Empagliflozin inhibits coronary microvascular dysfunction and reduces cardiac pericyte loss in db/db mice

Background

Coronary microvascular dysfunction (CMD) is a pathophysiological feature of diabetic heart disease. However, whether sodium-glucose cotransporter 2 (SGLT2) inhibitors protect the cardiovascular system by alleviating CMD is not known.

Objective

We observed the protective effects of empagliflozin (EMPA) on diabetic CMD.

Materials and methods

The mice were randomly divided into a db/db group and a db/db + EMPA group, and db/m mice served as controls. At 8 weeks of age, the db/db + EMPA group was given empagliflozin 10 mg/(kg⋅d) by gavage for 8 weeks. Body weight, fasting blood glucose and blood pressure were dynamically observed. Cardiac systolic and diastolic function and coronary flow reserve (CFR) were detected using echocardiography. The coronary microvascular structure and distribution of cardiac pericytes were observed using immunofluorescence staining. Picrosirius red staining was performed to evaluate cardiac fibrosis.

Results

Empagliflozin lowered the increased fasting blood glucose levels of the db/db group. The left ventricular ejection fraction, left ventricular fractional shortening, E/A ratio and E/e' ratio were not significantly different between the three groups. CFR was decreased in the db/db group, but EMPA significantly improved CFR. In contrast to the sparse and abnormal expansion of coronary microvessels observed in the db/db group, the number of coronary microvessels was increased, and the capillary diameter was decreased in the db/db + EMPA group. The number and microvascular coverage of cardiac pericytes were reduced in the db/db mice but were improved by EMPA. The cardiac fibrosis was increased in db/db group and may alleviate by EMPA.

Conclusion

Empagliflozin inhibited CMD and reduced cardiac pericyte loss in diabetic mice.

Treatment of HFpEF beyond the SGLT2-Is: Does the Addition of GLP-1 RA Improve Cardiometabolic Risk and Outcomes in Diabetic Patients?

Heart failure with preserved ejection fraction (HFpEF) is a common clinical syndrome frequently seen in elderly patients, the incidence of which is steadily increasing due to an ageing population and the increasing incidence of diseases, such as diabetes, hypertension, obesity, chronic renal failure, and so on. It is a multifactorial disease with different phenotypic aspects that share left ventricular diastolic dysfunction, and is the cause of about 50% of hospitalizations for heart failure in the Western world. Due to the complexity of the disease, no specific therapies have been identified for a long time. Sodium-Glucose Co-Transporter 2 Inhibitors (SGLT2-Is) and Glucagon-Like Peptide Receptor Agonists (GLP-1 RAs) are antidiabetic drugs that have been shown to positively affect heart and kidney diseases. For SGLT2-Is, there are precise data on their potential benefits in heart failure with reduced ejection fraction (HFrEF) as well as in HFpEF; however, insufficient evidence is available for GLP-1 RAs. This review addresses the current knowledge on the cardiac effects and potential benefits of combined therapy with SGLT2-Is and GLP-1RAs in patients with HFpEF.

Global trends and frontiers in research on coronary microvascular dysfunction: a bibliometric analysis from 2002 to 2022

BACKGROUND

Coronary microvascular dysfunction (CMD) is a leading cause of ischemic heart disease. Over the past few decades, considerable progress has been made with respect to research on CMD. The present study summarized the current research hotspots and trends on CMD by applying a bibliometric approach.

METHODS

Relevant publications between 2002 and 2022 were extracted from the Web of Science Core Collection. Visualization network maps of countries, institutions, authors, and co-cited authors were built using VOSviewer. CiteSpace was used for keyword analysis and the construction of a dual-map overlay of journals and a timeline view of co-cited references.

RESULTS

1539 CMD-related publications were extracted for bibliometric analysis. The annual publications generally showed an upward trend. The United States of America was the most prolific country, with 515 publications (33.5%). Camici P. G. was the most influential author, whereas the European Heart Journal, Circulation, and Journal of the American College of Cardiology were the most authoritative journals. Research hotspot analysis revealed that endothelial dysfunction as well as reduced nitric oxide production or bioavailability played critical roles in CMD development. Positron emission tomography was the most widely used imaging method for diagnosis. In addition, microvascular angina, hypertrophic cardiomyopathy, and heart failure have attracted much attention as the main clinical implications. Furthermore, international standards for CMD diagnosis and management may be the future research directions.

CONCLUSIONS

This study offers a comprehensive view about the hotspots and development trends of CMD, which can assist subsequent researchers and guide future directions.