Relation between stress-induced myocardial perfusion defects on cardiovascular magnetic resonance and coronary microvascular dysfunction in patients with cardiac syndrome X

Prognostic Value of Stress Perfusion Cardiac MRI in Cardiovascular Disease: A Systematic Review and Meta-Analysis of the Effects of the Scanner, Stress Agent, and Analysis Technique

Purpose To perform a systematic review and meta-analysis to assess the prognostic value of stress perfusion cardiac MRI in predicting cardiovascular outcomes. Materials and Methods A systematic literature search from the inception of PubMed, Embase, Web of Science, and China National Knowledge Infrastructure until January 2023 was performed for articles that reported the prognosis of stress perfusion cardiac MRI in predicting cardiovascular outcomes. The quality of included studies was assessed using the Quality in Prognosis Studies tool. Reported hazard ratios (HRs) of univariable regression analyses with 95% CIs were pooled. Comparisons were performed across different analysis techniques (qualitative, semiquantitative, and fully quantitative), magnetic field strengths (1.5 T vs 3 T), and stress agents (dobutamine, adenosine, and dipyridamole). Results Thirty-eight studies with 58 774 patients with a mean follow-up time of 53 months were included. There were 1.9 all-cause deaths and 3.5 major adverse cardiovascular events (MACE) per 100 patient-years. Stress-inducible ischemia was associated with a higher risk of all-cause mortality (HR: 2.55 [95% CI: 1.89, 3.43]) and MACE (HR: 3.90 [95% CI: 2.69, 5.66]). For MACE, pooled HRs of qualitative, semiquantitative, and fully quantitative methods were 4.56 (95% CI: 2.88, 7.22), 3.22 (95% CI: 1.60, 6.48), and 1.78 (95% CI: 1.39, 2.28), respectively. For all-cause mortality, there was no evidence of a difference between qualitative and fully quantitative methods (P = .79). Abnormal stress perfusion cardiac MRI findings remained prognostic when subgrouped based on underlying disease, stress agent, and field strength, with HRs of 3.54, 2.20, and 3.38, respectively, for all-cause mortality and 3.98, 3.56, and 4.21, respectively, for MACE. There was no evidence of subgroup differences in prognosis between field strengths or stress agents. There was significant heterogeneity in effect size for MACE outcomes in the subgroups assessing qualitative versus quantitative stress perfusion analysis, underlying disease, and field strength. Conclusion Stress perfusion cardiac MRI is valuable for predicting cardiovascular outcomes, regardless of the analysis method, stress agent, or magnetic field strength used. Keywords: MR-Perfusion, MRI, Cardiac, Meta-Analysis, Stress Perfusion, Cardiac MR, Cardiovascular Disease, Prognosis, Quantitative © RSNA, 2024 Supplemental material is available for this article.

Comparison of Baseline and Post-Nitrate Exercise Testing in Patients with Angina but Non-Obstructed Coronary Arteries with Different Acetylcholine Test Results

Background: Intracoronary acetylcholine testing may induce epicardial coronary artery spasm (CAS) or coronary microvascular spasm (CMVS) in patients with angina syndromes but non-obstructive coronary artery disease, but their causal role in individual patients is not always clear. In this prospective, observational single-center study, we aimed to assess whether (1) the induction of myocardial ischemia/angina by electrocardiogram (ECG) exercise stress test (EST) differs between patients showing different results in response to acetylcholine testing (i.e., CAS, CMVS, or no spasm); (2) the preventive administration of short-acting nitrates has any different effects on the EST of those patients who showed a positive basal EST. We expected that if exercise-induced angina and/or ischemic ECG changes are related to CAS, they should improve after nitrates administration, whereas they should not significantly improve if they are caused by CMVS. Methods: We enrolled 81 patients with angina syndromes and non-obstructive coronary artery disease, who were divided into three groups according to acetylcholine testing: 40 patients with CAS (CAS-group), 14 with CMVS (CMVS-groups), and 27 with a negative test (NEG-group). All patients underwent a basal EST (B-EST). Patients with a positive B-EST repeated the test 24-48 h later, 5 min after the administration of short-acting nitrates (N-EST). Results: There were no significant differences among the groups in terms of the B-EST results. B-EST was positive in eight (20%) patients in the CAS-group, seven (50%) in the CMVS-group, and six (22%) in the NEG-group (p = 0.076). N-EST, performed in eight, six, and five of these patients, also showed similar results in the three groups. Furthermore, the N-EST results also did not significantly differ compared to B-EST in any group, remaining positive in seven (87.5%), four (66.7%), and four (80%) patients in the CAS-group, CMVS-group, and NEG-group, respectively (p = 0.78). Conclusions: Our data show that patients with angina and non-obstructive coronary artery disease show largely comparable results of the ECG exercise stress test and similar poor effects of short-acting nitrates on abnormal ECG exercise stress test results. On the whole, our findings suggest caution in attributing to the results of Ach testing a definite causal role for the clinical syndrome in individual patients.

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.

Coronary microvascular dysfunction affects left ventricular global longitudinal strain response to dipyridamole stress echocardiography: a pilot study

The aim is to investigate, by means of speckle tracking echocardiography, left ventricular (LV) contractile function at rest and during dipyridamole stress in patients with coronary microvascular dysfunction (CMD). 59 patients (39% women, mean age 65.6 ± 6.1 years) with history of chest pain and without obstructive coronary artery disease (CAD) underwent dipyridamole stress echocardiography. Coronary flow was assessed in the left anterior descending coronary artery. Coronary flow reserve (CFR) was determined as the ratio of hyperaemic to baseline diastolic coronary flow velocity. CMD was defined as CFR < 2. Global longitudinal strain (GLS) was measured at rest and at peak dose. Nineteen patients (32%) among the overall population showed CMD. Baseline GLS was significantly lower in patients with CMD (- 16.8 ± 2.7 vs. - 19.1 ± 3.1, p < 0.01). A different contractile response to dipyridamole infusion was observed between the two groups: GLS significantly increased up to peak dose in patients without CMD (from - 19.1 ± 3.1 to - 20.2 ± 3.1, p < 0.01), and significantly decreased in patients with CMD (from - 16.8 ± 2.7 to - 15.8 ± 2.7, p < 0.01). There was a significant inverse correlation between CFR and ∆GLS (r = - 0.82, p < 0.01). Rest GLS and GLS response to dipyridamole stress are markedly impaired among patients with chest pain syndrome, non-obstructive CAD and CMD, reflecting subclinical LV systolic dysfunction and lack of LV contractile reserve due to underlying myocardial ischemia.

Strengths and weaknesses of alternative noninvasive imaging approaches for microvascular ischemia

Structural and functional abnormalities of coronary microvasculature are highly prevalent in several clinical settings and often associated with worse clinical outcomes. Therefore, there is a growing interest in the detection and treatment of this, often overlooked, disease. Coronary angiography allows the assessment of the Coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR). However, the measurement of these parameters is not always feasible because of limited technical availability and the need for a cardiac catheterization with a small but real risk of potential complications. Recent advances in non-invasive imaging techniques allow the assessment of coronary microvascular function with good accuracy and reproducibility. The objective of this review is to discuss the strengths and weaknesses of alternative non-invasive approaches used in the diagnosis of coronary microvascular dysfunction (CMD), highlighting the most recent advances for each imaging modality.

Sex-Specific Stress Perfusion Cardiac Magnetic Resonance Imaging in Suspected Ischemic Heart Disease: Insights From SPINS Retrospective Registry

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of mortality in women, but current noninvasive cardiac imaging techniques have sex-specific limitations.

OBJECTIVES

In this study, the authors sought to investigate the effect of sex on the prognostic utility and downstream invasive revascularization and costs of stress perfusion cardiac magnetic resonance (CMR) for suspected CVD.

METHODS

Sex-specific prognostic performance was evaluated in a 2,349-patient multicenter SPINS (Stress CMR Perfusion Imaging in the United States [SPINS] Study) registry. The primary outcome measure was a composite of cardiovascular death and nonfatal myocardial infarction; secondary outcomes were hospitalization for unstable angina or heart failure, and late unplanned coronary artery bypass grafting.

RESULTS

SPINS included 1,104 women (47% of cohort); women had higher prevalence of chest pain (62% vs 50%; P < 0.0001) but lower use of medical therapies. At the 5.4-year median follow-up, women with normal stress CMR had a low annualized rate of primary composite outcome similar to men (0.54%/y vs 0.75%/y, respectively; P = NS). In contrast, women with abnormal CMR were at higher risk for both primary (3.74%/y vs 0.54%/y; P < 0.0001) and secondary (9.8%/y vs 1.6%/y; P < 0.0001) outcomes compared with women with normal CMR. Abnormal stress CMR was an independent predictor for the primary (HR: 2.64 [95% CI: 1.20-5.90]; P = 0.02) and secondary (HR: 2.09 [95% CI: 1.43-3.08]; P < 0.0001) outcome measures. There was no effect modification for sex. Women had lower rates of invasive coronary angiography (ICA; 3.6% vs 7.3%; P = 0.0001) and downstream costs ($114 vs $171; P = 0.001) at 90 days following CMR. There was no effect of sex on diagnostic image quality.

CONCLUSIONS

Stress CMR demonstrated excellent prognostic performance with lower rates of ICA referral in women. Stress CMR should be considered as a first-line noninvasive imaging tool for the evaluation of women. (Stress CMR Perfusion Imaging in the United States [SPINS] Study [SPINS]; NCT03192891).

Impairment in quantitative microvascular function in non-ischemic cardiomyopathy as demonstrated using cardiovascular magnetic resonance

Background

Microvascular dysfunction (MVD) is present in various cardiovascular diseases and portends worse outcomes. We assessed the prevalence of MVD in patients with non-ischemic cardiomyopathy (NICM) as compared to subjects with preserved ejection fraction (EF) using stress cardiovascular magnetic resonance (CMR).

Methods

We retrospectively studied consecutive patients with NICM and 58 subjects with preserved left ventricular (LV) EF who underwent stress CMR between 2011–2016. MVD was defined visually as presence of a subendocardial perfusion defect and semiquantitatively by myocardial perfusion reserve index (MPRI<1.51). MPRI was compared between groups using univariate analysis and multivariable linear regression.

Results

In total, 41 patients with NICM (mean age 51 ± 14, 59% male) and 58 subjects with preserved LVEF (mean age 51 ± 13, 31% male) were identified. In the NICM group, MVD was present in 23 (56%) and 11 (27%) by semiquantitative and visual evaluation respectively. Compared to those with preserved LVEF, NICM patients had lower rest slope (3.9 vs 4.9, p = 0.05) and stress perfusion slope (8.8 vs 11.7, p<0.001), and MPRI (1.41 vs 1.74, p = 0.02). MPRI remained associated with NICM after controlling for age, gender, hypertension, ethnicity, diabetes, and late gadolinium enhancement (log MPR, β coefficient = -0.19, p = 0.007).

Conclusions

MVD—as assessed using CMR—is highly prevalent in NICM as compared to subjects with preserved LVEF even after controlling for covariates. Semiquantitative is able to detect a greater number of incidences of MVD compared to visual methods alone. Further studies are needed to determine whether treatment of MVD is beneficial in NICM.

Critical role of the coronary microvasculature in heart disease: From pathologic driving force to "innocent" bystander

The coronary microvasculature is responsible for providing oxygen and nutrients to myocardial tissue. A healthy microvasculature with an intact and properly functioning endothelium accomplishes this by seemless changes in vascular tone to match supply and demand. Perturbations in the normal physiology of the microvasculature, including endothelial and/or vascular smooth muscle dysfunction, result in impaired function (vasoconstriction, antithrombotic, etc.) and structural (hypertrophic, fibrotic) abnormalities that lead to microvascular ischemia and potential organ damage. While coronary microvascular dysfunction (CMD) is the primary pathologic driving force in ischemia with non-obstructive coronary artery disease (INOCA), angina with no obstructive coronary arteries (ANOCA), and myocardial infarction with non-obstructed coronary arteries (MINOCA), it may be a bystander in many cardiac disorders which later become pathologically associated with signs and/or symptoms of myocardial ischemia. Importantly, regardless of the primary or secondary basis of CMD in the heart, it is associated with important increases in morbidity and mortality. In this review we discuss salient features pertaining to known pathophysiologic mechanisms driving CMD, the spectrum of heart diseases where it places a critical role, invasive and non-invasive diagnostic testing, management strategies, and the gaps in knowledge where future research efforts are needed.

Coronary microvascular dysfunction and findings of heart failure with preserved ejection fraction in patients with microvascular angina

BACKGROUND

Coronary microvascular dysfunction (CMD) may cause symptoms of myocardial ischemia (microvascular angina [MVA]), but recent studies suggested that it might also contribute to the syndrome of heart failure with preserved ejection fraction (HFpEF). In this study we assessed the relation of CMD with findings of HFpEF in MVA patients.

METHODS

We enrolled 36 consecutive patients with MVA, in whom we assessed: 1) coronary blood flow (CBF) response to adenosine and cold pressor test (CPT) by color-Doppler echocardiography of the left anterior descending coronary artery; 2) complete echocardiographic examination; 3) N-terminal-pro-B-natriuretic peptide (NT-proBNP); 4) grade of dyspnea by the modified Medical Research Scale.

RESULTS

Among patients, 15 had definite HFpEF findings (group 1), 12 had equivocal HFpEF findings (group 2) and 9 had no evidence of HFpEF findings (group 3). Group 1 patients were older, had more cardiovascular risk factors and higher NT-proBNP levels (P=0.018), and showed a higher prevalence of diastolic dysfunction. Left ventricle dimensions and systolic function, however, did not differ among groups. Dyspnea was also not significantly different among groups (P=0.19). CBF to adenosine was 1.85±0.47, 1.78±0.40 1.49±0.32 in group 1, 2 and 3, respectively (P=0.13). Similarly, CBF response to CPT was 1.57±0.4, 1.49±0.2 and 1.45±0.3 in the 3 groups, respectively (P=0.74). Both CBF response to adenosine and CPT showed no relation with the severity of dyspnea symptoms.

CONCLUSIONS

Our data suggest that in patients with MVA there is no relation between the grade of impairment of coronary microvascular dilatation and findings of HFpEF.

Clinical features and outcomes of patients with stable or unstable chest pain and no-obstructive coronary artery disease

Background

Coronary microvascular dysfunction can be responsible for both stable angina and acute coronary syndrome (ACS). There are scarce data, however, about comparisons of clinical characteristics and outcomes of these 2 groups of patients.

Materials and methods

We studied 47 consecutive patients who underwent coronary angiography for angina syndromes and showed no obstructive stenosis. Patients were divided in 2 groups, according to their clinical presentation, i.e., stable angina (n = 21) or non-ST segment elevation ACS (NSTE-ACS; n = 26). An intracoronary acetylcholine (Ach) test was performed in 12 and 17 patients of the 2 groups, respectively. Angina status, assessed by Seattle Angina Questionnaire (SAQ), and clinical events were assessed after 1, 6, and 30 months. An exercise stress test was performed 1 month after discharge.

Results

Clinical characteristics and exercise test results of the 2 groups were largely similar. Ach testing induced epicardial or microvascular spasm in 6 (50.0%) and 10 (58.8%) stable and NSTE-ACS patients, respectively (p = 0.72). Stable patients reported higher rates of angina, compared to NSTE-ACS patients, both at 1 (p = 0.04) and 30 months (81 vs. 50%, p = 0.036) of follow-up. SAQ scores were also lower in stable vs. NSTE-ACS patients. Ach testing results showed no association with clinical outcomes.

Conclusion

Clinical characteristics and exercise and Ach testing results are similar in angina patients with no-obstructive coronary artery disease with a stable or NSTE-ACS presentation. Stable patients show a worse symptomatic outcome irrespective of Ach test results.

Coronary Microvascular Dysfunction is Common in Patients Hospitalized with COVID-19 Infection

Background and Aims

Microvascular disease is considered as one of the main drivers of morbidity and mortality in severe COVID‐19, and microvascular dysfunction has been demonstrated in the subcutaneous and sublingual tissues in COVID‐19 patients. The presence of coronary microvascular dysfunction (CMD) has also been hypothesized, but direct evidence demonstrating CMD in COVID‐19 patients is missing. In the present study, we aimed to investigate CMD in patients hospitalized with COVID‐19, and to understand whether there is a relationship between biomarkers of myocardial injury, myocardial strain and inflammation and CMD.

Methods

39 patients that were hospitalized with COVID‐19 and 40 control subjects were included to the present study. Biomarkers for myocardial injury, myocardial strain, inflammation, and fibrin turnover were obtained at admission. A comprehensive echocardiographic examination, including measurement of coronary flow velocity reserve (CFVR), was done after the patient was stabilized.

Results

Patients with COVID‐19 infection had a significantly lower hyperemic coronary flow velocity, resulting in a significantly lower CFVR (2.0 ± 0.3 vs. 2.4 ± 0.5, p < .001). Patients with severe COVID‐19 had a lower CFVR compared to those with moderate COVID‐19 (1.8 ± 0.2 vs. 2.2 ± 0.2, p < .001) driven by a trend toward higher basal flow velocity. CFVR correlated with troponin (p = .003, r: −.470), B‐type natriuretic peptide (p < .001, r: −.580), C‐reactive protein (p < .001, r: −.369), interleukin‐6 (p < .001, r: −.597), and d‐dimer (p < .001, r: −.561), with the three latter biomarkers having the highest areas‐under‐curve for predicting CMD.

Conclusions

Coronary microvascular dysfunction is common in patients with COVID‐19 and is related to the severity of the infection. CMD may also explain the “cryptic” myocardial injury seen in patients with severe COVID‐19 infection.

The evolving role of coronary computed tomography in understanding sex differences in coronary atherosclerosis

Our understanding of sex differences in subclinical atherosclerosis and plaque composition and characteristics have greatly improved with the use of coronary computed tomography (CCTA) over the past years. CCTA has emerged as an important frontline diagnostic test for women, especially as we continue to understand the impact of non-obstructive atherosclerosis as well as diffuse, high risk plaque as precursors of acute cardiac events in women. Based on its ability to identify complex plaque morphology such as low attenuation plaque, high risk non calcified plaque, positive remodeling, fibrous cap, CCTA can be used to assess plaque characteristics. CCTA can avoid false positive of other imaging studies, if included earlier in assessment of ischemic symptoms. In the contemporary clinical setting, CCTA will prove useful in further understanding and managing cardiovascular disease in women and those without traditional obstructive coronary disease.

Doppler Echocardiography Assessment of Coronary Microvascular Function in Patients With Angina and No Obstructive Coronary Artery Disease

Echocardiographic evaluation is an essential part of the diagnostic work-up in patients with known or suspected cardiovascular disease. Transthoracic Doppler echocardiography (TTDE) enables straightforward and reliable visualization of flow in the left anterior descending artery. In the absence of obstructive coronary artery disease, low TTDE-derived coronary flow velocity reserve (CFVR) is considered a marker of coronary microvascular dysfunction (CMD). TTDE CFVR is free from ionizing radiation and widely available, utilizing high-frequency transducers, pharmacologic vasodilator stress, and pulsed-wave Doppler quantification of diastolic peak flow velocities. European Society of Cardiology guidelines recommend TTDE CFVR evaluation only following preceding anatomic invasive or non-invasive coronary imaging excluding obstructive CAD. Accordingly, clinical use of TTDE CFVR is limited and CMD frequently goes undiagnosed. An evolving body of evidence underlines that low CFVR is an important and robust predictor of adverse prognosis and continuing symptoms in angina patients both with and without obstructive CAD. The majority of angina patients have no obstructive CAD, particularly among women. This has led to the suggestion that there may be a gender-specific female atherosclerotic phenotype with less epicardial obstruction, and a low CFVR signifying CMD instead. Nevertheless, available evidence indicates low CFVR is an equally important prognostic marker in both men and women. In this review, TTDE CFVR was evaluated regarding indication, practical and technical aspects, and interpretation of results. Association with symptoms and prognosis, comparison with alternative invasive and non-invasive imaging modalities, and possible interventions in angina patients with low CFVR were discussed, and key research questions were proposed.

Assessment and pathophysiology of microvascular disease: recent progress and clinical implications

The development of novel, non-invasive techniques and standardization of protocols to assess microvascular dysfunction have elucidated the key role of microvascular changes in the evolution of cardiovascular (CV) damage, and their capacity to predict an increased risk of adverse events. These technical advances parallel with the development of novel biological assays that enabled the ex vivo identification of pathways promoting microvascular dysfunction, providing novel potential treatment targets for preventing cerebral-CV disease. In this article, we provide an update of diagnostic testing strategies to detect and characterize microvascular dysfunction and suggestions on how to standardize and maximize the information obtained from each microvascular assay. We examine emerging data highlighting the significance of microvascular dysfunction in the development CV disease manifestations. Finally, we summarize the pathophysiology of microvascular dysfunction emphasizing the role of oxidative stress and its regulation by epigenetic mechanisms, which might represent potential targets for novel interventions beyond conventional approaches, representing a new frontier in CV disease reduction.

Coronary Microvascular Dysfunction: A Practical Approach to Diagnosis and Management

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of diagnostic and treatment considerations in patients with coronary microvascular dysfunction (CMD) in the absence of obstructive coronary artery disease (CAD).

RECENT FINDINGS

The prevalence of obstructive CAD in unselected patient populations referred for evaluation of angina is less than 10%. A significant proportion of patients with angina and no obstructive CAD have CMD, a condition associated with impaired cardiovascular prognosis. Non-invasive and invasive evaluation of coronary microvascular function is feasible and widely available, yet CMD is underdiagnosed and undertreated. A patient-tailored treatment approach guided by coronary microvascular testing shows promising results for patient-reported outcomes of symptom burden and quality of life. Coronary microvascular testing should be considered in angina patients with no obstructive CAD, before other causes of chest pain are explored. A patient-tailored treatment approach guided by a complete evaluation of epicardial anatomy and macro-and microvascular function may help optimize treatment strategy and prevent unnecessary medical interventions. More research is needed to establish the long-term effect of patient-tailored therapies on risk reduction in CMD.

Evaluation of non-invasive imaging parameters in coronary microvascular disease: a systematic review

BACKGROUND

Coronary microvascular dysfunction (CMD) is an important underlying cause of angina pectoris. Currently, no diagnostic tool is available to directly visualize the coronary microvasculature. Invasive microvascular reactivity testing is the diagnostic standard for CMD, but several non-invasive imaging techniques are being evaluated. However, evidence on reported non-invasive parameters and cut-off values is limited. Thus, we aimed to provide an overview of reported non-invasive parameters and corresponding cut-off values for CMD.

METHODS

Pubmed and EMBASE databases were systematically searched for studies enrolling patients with angina pectoris without obstructed coronary arteries, investigating at least one non-invasive imaging technique to quantify CMD. Methodological quality assessment of included studies was performed using QUADAS-2.

RESULTS

Thirty-seven studies were included. Ten cardiac magnetic resonance studies reported MPRI and nine positron emission tomography (PET) and transthoracic echocardiography (TTE) studies reported CFR. Mean MPRI ranged from 1.47 ± 0.36 to 2.01 ± 0.41 in patients and from 1.50 ± 0.47 to 2.68 ± 0.49 in controls without CMD. Reported mean CFR in PET and TTE ranged from 1.39 ± 0.31 to 2.85 ± 1.35 and 1.69 ± 0.40 to 2.40 ± 0.40 for patients, and 2.68 ± 0.83 to 4.32 ± 1.78 and 2.65 ± 0.65 to 3.31 ± 1.10 for controls, respectively.

CONCLUSIONS

This systematic review summarized current evidence on reported parameters and cut-off values to diagnose CMD for various non-invasive imaging modalities. In current clinical practice, CMD is generally diagnosed with a CFR less than 2.0. However, due to heterogeneity in methodology and reporting of outcome measures, outcomes could not be compared and no definite reference values could be provided.

Cardiovascular risk is associated with a transmural gradient of myocardial oxygenation during adenosine infusion

AIMS

In patients with coronary artery disease (CAD), a transmural gradient of myocardial perfusion has been repeatedly observed, with the subendocardial layer showing more pronounced perfusion deficits. Oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) allows for monitoring transmural changes of myocardial oxygenation in vivo. We hypothesized that OS-CMR could help identify a transmural oxygenation gradient as a disease marker in patients at risk for CAD.

METHODS AND RESULTS

We assessed 34 patients with known CAD and 28 subjects with coronary risk factors but no evidence of significant CAD. Results were compared with 11 healthy volunteers. OS-CMR was performed at 1.5 T, applying a T2*-weighted cine steady state free precession sequence at baseline and during infusion of adenosine. A reader blinded to patient data quantified the relative change of myocardial oxygenation in OS-CMR, defined by the change of signal intensity (ΔSI%) between baseline and during adenosine infusion in the entire myocardium, the subepicardial layer, and the subendocardial layer. SI changes were homogenous throughout the myocardium in healthy subjects, whereas both, patients with risk factors only and patients with CAD, had a significantly smaller ΔSI% in the subendocardial layer than in the subendocardial layer. Both patient groups had an overall decreased ΔSI% across all layers when compared with healthy subjects (P < 0.05).

CONCLUSION

Even in the absence of overt CAD, cardiovascular risk factors are associated with a transmural gradient of the myocardial oxygenation response to adenosine as assessed by OS-CMR. An inducible transmural oxygenation gradient may serve as a non-invasive marker for cardiovascular risk.

The Chief Scientist Office Cardiovascular and Pulmonary Imaging in SARS Coronavirus disease-19 (CISCO-19) study

BACKGROUND

COVID-19 is typically a primary respiratory illness with multisystem involvement. The prevalence and clinical significance of cardiovascular and multisystem involvement in COVID-19 remain unclear.

METHODS

This is a prospective, observational, multicentre, longitudinal, cohort study with minimal selection criteria and a near-consecutive approach to screening. Patients who have received hospital care for COVID-19 will be enrolled within 28 days of discharge. Myocardial injury will be diagnosed according to the peak troponin I in relation to the upper reference limit (URL, 99th centile) (Abbott Architect troponin I assay; sex-specific URL, male: >34 ng/L; female: >16 ng/L). Multisystem, multimodality imaging will be undertaken during the convalescent phase at 28 days post-discharge (Visit 2). Imaging of the heart, lung, and kidneys will include multiparametric, stress perfusion, cardiovascular magnetic resonance imaging, and computed tomography coronary angiography. Health and well-being will be assessed in the longer term. The primary outcome is the proportion of patients with a diagnosis of myocardial inflammation.

CONCLUSION

CISCO-19 will provide detailed insights into cardiovascular and multisystem involvement of COVID-19. Our study will inform the rationale and design of novel therapeutic and management strategies for affected patients.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04403607.

Feasibility and Prognostic Value of Vasodilator Stress Perfusion CMR in Patients With Atrial Fibrillation

OBJECTIVES

The aim of this study was to assess the feasibility and prognostic value of vasodilator stress perfusion cardiovascular magnetic resonance (CMR) in patients with atrial fibrillation (AF).

BACKGROUND

Because most studies have excluded arrhythmic patients, the prognostic value of stress perfusion CMR in patients with AF is unknown.

METHODS

Between 2008 and 2018, consecutive patients with suspected or stable chronic coronary artery disease and AF referred for vasodilator stress perfusion CMR were included and followed for the occurrence of major adverse cardiovascular event(s) (MACE), defined as cardiovascular death or nonfatal myocardial infarction. The diagnosis of AF was defined by 12-lead electrocardiography before and after CMR. Univariate and multivariate Cox regressions were performed to determine the prognostic value of inducible ischemia or late gadolinium enhancement (LGE) by CMR.

RESULTS

Of 639 patients (mean age 72 ± 9 years, 77% men), 602 (94%) completed the CMR protocol, and 538 (89%) completed follow-up (median 5.1 years); 80 had MACE. Using Kaplan-Meier analysis, the presence of ischemia (hazard ratio [HR]: 7.56; 95% confidence interval [CI]: 4.86 to 11.80) or LGE (HR: 2.41; 95% CI: 1.55 to 3.74) was associated with the occurrence of MACE (p < 0.001 for both). In a multivariate Cox regression including clinical and CMR indexes, the presence of ischemia (HR: 5.98; 95% CI: 3.68 to 9.73) or LGE (HR: 2.61; 95% CI: 1.89 to 3.60) was an independent predictor of MACE (p < 0.001 for both).

CONCLUSIONS

In patients with AF, stress perfusion CMR is feasible and has good discriminative prognostic value to predict the occurrence of MACE.

State of the Art in Noninvasive Imaging of Ischemic Heart Disease and Coronary Microvascular Dysfunction in Women: Indications, Performance, and Limitations

PURPOSE OF REVIEW

Establishing a diagnosis of ischemic heart disease (IHD) in women, including assessment for coronary microvascular dysfunction (CMD) when indicated, can be challenging. Access to performance of invasive testing when appropriate may be limited, and noninvasive imaging assessments have evolved. This review will summarize the various noninvasive imaging modalities available for the diagnosis of IHD and CMD in women, outlining indications, performance modalities, advantages, and limitations.

RECENT FINDINGS

While stress echocardiography and single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) are widely available and can detect IHD in women, their ability to specifically identify CMD is limited. Novel developments in cardiac magnetic resonance (CMR) imaging, including spectroscopy, and positron emission tomography (PET) have changed the diagnostic landscape. Coronary computed tomographic angiography (CCTA), while unable to diagnose CMD, is developing an emerging role in the risk stratification of ischemic syndromes. Despite the discovery of increased CMD prevalence in symptomatic women and technological advances in diagnostic imaging, practitioners are limited by user expertise and center availability when choosing a diagnostic imaging modality. Knowledge of this evolving field is imperative as it highlights the need for sex-specific assessment of cardiovascular syndromes.

Determination of Myocardial Scar Tissue in Coronary Slow Flow Phenomenon and The Relationship Between Amount of Scar Tissue and Nt-ProBNP

Fundamento

A fisiopatologia e o prognóstico não estão claramente determinados nos pacientes com fenômeno do fluxo coronário lento (FCL). Esses pacientes apresentam várias condições clínicas, que variam desde quadro assintomático até internação hospitalar com morte cardíaca súbita.

Objetivos

Nosso objetivo foi avaliar os achados da ressonância magnética cardíaca (RMC) com o realce tardio pelo gadolínio (RTG), como um indicador de fibrose miocárdica. Também buscamos determinar a relação entre a presença de fibrose miocárdica e os níveis de NT-proBNP em pacientes com FCL na artéria coronária descendente anterior esquerda (DAE).

Métodos

Ao todo, 35 pacientes, entre 31 e 75 anos de idade, foram incluídos. Os pacientes estudados (n=19) apresentaram artérias coronárias epicárdicas normais na angiografia, mas tinham FCL na DAE. O grupo controle de pacientes (n=16) apresentou artérias coronárias epicárdicas normais e níveis de escore TIMI normais na angiografia. Em ambos os grupos, os pacientes foram examinados com RMC para a detecção de presença de fibrose miocárdica. Além disso, níveis plasmáticos de NT-proBNP foram medidos. Valores de p < 0,05 foram considerados significativos.

Resultados

A taxa de fibrose miocárdica foi significativamente maior na RMC para os pacientes com FCL (p=0.018). Uma quantidade variável de tecido cicatricial foi detectada no ápice ventricular esquerdo em 7 pacientes e nas regiões inferior e inferolateral em 3 pacientes. Não foram observadas diferenças nos níveis de NT-proBNP nos pacientes com FCL. Entretanto, os níveis de NT-proBNP foram maiores nos pacientes com FCL, que apresentaram fibrose miocárdica na RMC (p=0.022).

Conclusões

Em suma, o RTG na RMC mostrou que a cicatriz miocárdica isquêmica pode estar presente nos pacientes com FCL. Esses resultados indicam que o FCL pode nem sempre ser inofensivo. (Arq Bras Cardiol. 2020; 114(3):540-551)

Clinical outcomes in patients with primary stable microvascular angina: is the jury still out?

Several studies have demonstrated that angina chest pain in presence of normal or near normal coronary arteries (NCAs) is mainly related to coronary microvascular dysfunction (CMD). However, controversial findings exist about clinical outcome of these patients. In this article, we critically review characteristics and results of the main clinical studies reporting clinical outcome of stable patients with angina chest pain and non-obstructive coronary artery disease (NO-CAD). Published data indicate that clinical outcomes of these patients are heterogeneous, but those with strict criteria for primary stable microvascular angina (MVA, i.e. typical angina with NCAs mainly related to efforts) do not appear to have an increased mortality or risk of major coronary events. A major determinant of outcome in patients with MVA and NO-CAD seems instead related to non-critical atherosclerotic disease, the presence of which should suggest a more aggressive management of cardiovascular risk factors and preventive management. Future studies should assess whether CMD may have a relevant prognostic role in the latter clinical context and/or in other clinical settings of NO-CAD different from primary stable MVA.

Pathophysiology, classification, and MRI parallels in microvascular disease of the heart and brain

Diagnostic imaging technology in vascular disease has long focused on large vessels and the pathologic processes that impact them. With improved diagnostic techniques, investigators are now able to uncover many underlying mechanisms and prognostic factors for microvascular disease. In the heart and brain, these pathologic entities include coronary microvascular disease and cerebral small vessel disease, both of which have significant impact on patients, causing angina, myocardial infarction, heart failure, stroke, and dementia. In the current paper, we will discuss parallels in pathophysiology, classification, and diagnostic modalities, with a focus on the role of magnetic resonance imaging in microvascular disease of the heart and brain. Novel approaches for streamlined imaging of the cardiac and central nervous systems including the use of intravascular contrast agents such as ferumoxytol are presented, and unmet research gaps in diagnostics are summarized.

Five-Year Follow-Up of Coronary Microvascular Dysfunction and Coronary Artery Disease in Systemic Lupus Erythematosus: Results From a Community-Based Lupus Cohort

OBJECTIVE

The present study was undertaken to investigate prospective change in the prevalence of coronary microvascular dysfunction (CMD) and obstructive coronary artery disease (CAD) in a cohort of subjects with systemic lupus erythematosus (SLE) initially evaluated for anginal chest pain (CP). Prior work documented a relatively high prevalence of CMD in the absence of obstructive CAD in subjects with SLE.

METHODS

Twenty female SLE subjects with CP who underwent stress cardiac magnetic resonance imaging (CMRI) and coronary computed tomography angiography at baseline were reevaluated at 5 years.

RESULTS

Seventeen subjects (85%) were available and reenrolled, of which 11 (65%) had persistent CP at follow-up. Fourteen subjects had complete follow-up CMRI, of which 36% (n = 5) demonstrated CMD at follow-up. Further, 25% (1 of 4) of the originally abnormal myocardial perfusion reserve index (MPRI) findings at baseline were lower at follow-up, while 2 additional abnormal MPRI findings at follow-up were noted in previously normal MPRI results. The prevalence of CMD and nonobstructive/obstructive CAD both was unchanged between baseline and follow-up, respectively (both P values not significant). During follow-up, 33% of subjects (5 of 15) had adverse cardiac outcomes, including pericarditis, unstable angina, or intracranial aneurysm clipping procedure.

CONCLUSION

At the 5-year follow-up of SLE subjects with CP who were evaluated at baseline and follow-up, a majority had persistent CP, and nearly one-half had similar or worse myocardial perfusion consistent with CMD without obstructive CAD. These findings propose an alternative explanation for CP in SLE subjects compared to the more common SLE-related accelerated obstructive CAD accounting for CP and adverse outcomes. These findings support further studies of CMD as an etiology for cardiac morbidity and mortality in SLE.

Prevalence and clinical significance of cardiovascular magnetic resonance adenosine stress-induced myocardial perfusion defect in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is thought to be associated with microvascular dysfunction. Adenosine stress-perfusion cardiovascular magnetic resonance imaging (CMR) is a sensitive method for assessing microvascular perfusion abnormalities. We evaluated the prevalence and clinical characteristics of HCM patients with adenosine-induced perfusion defects on CMR.

METHODS

Among 189 consecutive patients with HCM who underwent adenosine-stress perfusion CMR, 115 patients who had clinical, echocardiography, 24-h Holter monitoring and treadmill exercise test data were analyzed. We calculated myocardial perfusion ratio index from the intensity-over-time curve to quantify perfusion defects. The presence and extent of the stress-induced perfusion defect were compared with clinical characteristics, presence and extent of late gadolinium enhancement (LGE), left ventricular (LV) mass index and volume, presence of non-sustained ventricular tachycardia (NSVT) and results of treadmill exercise test.

RESULTS

The mean age of enrolled patients was 51.8 ± 11.3 years. Most patients were asymptomatic except 25 subjects presented with New York Heart Association Class II dyspnea and 16 patients with atypical non-exertional chest discomfort. LGE was present in 103 (89.6%) subjects. Adenosine stress-induced perfusion defects were present in 48 (42%) subjects. None of the perfusion defects corresponded with a single or multiple coronary artery territories, showing a multiple patchy pattern in 24 (50.0%), a concentric subendocardial pattern in 20 subjects (41.7%), and as a single blot-like defect in the remaining 4 (8.3%). A perfusion defect was associated with NSVT, LV apical aneurysm, higher LV mass index, and higher LGE volume on univariate analysis. Multivariate analysis revealed female gender (P = 0.008), presence of apical aneurysm and NSVT (P = 0.036 and 0.047, respectively), and LV mass index (P = 0.022) to be independently associated with adenosine stress-induced perfusion defects.

CONCLUSIONS

In patients with HCM, adenosine-stress perfusion defects on CMR are present in more than 40% of subjects. This perfusion defect is associated with NSVT, higher LV mass index, and apical aneurysms. The prognostic value of this finding needs further elucidation.

Coronary microvascular dysfunction

Patients with coronary microvascular dysfunction (CMVD) represent a widespread population and despite the good prognosis, many of them have a poor quality of life with strong limitations in their daily activities because of the angina symptoms. This article summarizes the most frequent clinical presentation pictures like stable and unstable microvascular angina. Main risk factors are discussed, followed by the latest updates on the subject about different pathogenic hypotheses, diagnosis and treatment. Not very well understood microvascular alterations, like slow flow phenomenon and no reflow are discussed and both prognosis and the impact of the disease in the quality of life are analyzed.

Design, methodology and baseline characteristics of the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD)

A significant number of women with signs and symptoms of ischemia with no obstructive coronary artery disease (INOCA) have coronary vascular dysfunction detected by invasive coronary reactivity testing (CRT). However, the noninvasive assessment of coronary vascular dysfunction has been limited.

METHODS

The Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) was a prospective study of women with suspected INOCA aimed to investigate whether (1) cardiac magnetic resonance imaging (CMRI) abnormalities in left ventricular morphology and function and myocardial perfusion predict CRT measured coronary microvascular dysfunction, (2) these persistent CMRI abnormalities at 1-year follow-up predict persistent symptoms of ischemia, and (3) these CMRI abnormalities predict cardiovascular outcomes. By design, a sample size of 375 women undergoing clinically indicated invasive coronary angiography for suspected INOCA was projected to complete baseline CMRI, a priori subgroup of 200 clinically indicated CRTs, and a priori subgroup of 200 repeat 1-year follow-up CMRIs.

RESULTS

A total of 437 women enrolled between 2008 and 2015, 374 completed baseline CMRI, 279 completed CRT, and 214 completed 1-year follow-up CMRI. Mean age was 55± 11 years, 93% had 20%-50% coronary stenosis, and 7% had <20% stenosis by angiography.

CONCLUSIONS

The WISE-CVD study investigates the utility of noninvasive CMRI to predict coronary vascular dysfunction in comparison to invasive CRT, and the prognostic value of CMRI abnormalities for persistent symptoms of ischemia and cardiovascular outcomes in women with INOCA. WISE-CVD will provide new understanding of a noninvasive imaging modality for future clinical trials.

Novel application of quantitative flow ratio for predicting microvascular dysfunction after ST-segment-elevation myocardial infarction

OBJECTIVES

This study evaluated quantitative flow ratio (QFR) to predict microvascular dysfunction (MVD) in patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

QFR is a novel approach for the rapid computation of fractional flow reserve based on three-dimensional quantitative coronary angiography. We hypothesized that QFR computation could be used to predict MVD after STEMI.

METHODS

Indexes such as contrast-flow QFR (cQFR), fixed-flow QFR (fQFR), and hyperemic flow velocity (HFV) were calculated in 130 STEMI patients with culprit lesion with ≥50% diameter stenosis and TIMI flow grade 2/3 in the spontaneously recanalized culprit artery on initial angiography. MVD was defined as microvascular obstruction determined by contrast-enhanced cardiac magnetic resonance at a median of 5 days after percutaneous coronary intervention.

RESULTS

Patients were divided into the MVD group (76/130, 58.5%) and non-MVD group (54/130, 41.5%). Patients with MVD had higher cQFR-fQFR value (0.080 ± 0.058 vs. 0.038 ± 0.039, p < .001) and lower modeled HFV (0.096 ± 0.044 vs. 0.144 ± 0.041 m/s, p < .001). Receiver operator characteristic curve analysis revealed that both the cQFR-fQFR value (area under the curve, AUC = 0.716, p < .001) and modeled HFV (AUC = 0.805, p < .001) had high specificity and positive predictive value to predict MVD. In multivariable logistic analysis, cQFR-fQFR was identified as an independent predictor of MVD (odds ratio = 9.800, p < .001).

CONCLUSIONS

This proof-of-concept study suggested that QFR computation may be a useful tool to predict MVD after STEMI (Trial Registration:NCT03780335).

Long-term prognostic value of quantitative myocardial perfusion in patients with chest pain and normal coronary arteries

BACKGROUND

Patients with chest pain and no obstructive coronary artery disease have shown a high incidence of major adverse cardiovascular events (MACE). We evaluated the role of absolute myocardial perfusion quantification in predicting all-cause mortality and MACE during long-term follow-up in this group of patients.

METHODS

We studied 79 patients who underwent Nitrogen-13 ammonia PET for quantification of global myocardial blood flow (MBF) and myocardial flow reserve (MFR) due to suspected impaired myocardial perfusion. Patients with coronary artery disease (i.e., > 30% stenosis in one or more coronary arteries) were excluded. We assessed all-cause mortality and MACE. MACE was defined as the composite incidence of death, myocardial infarction (MI), or hospitalization due to heart failure.

RESULTS

Median follow-up was 8 (IQR: 3-14) years. Univariate Cox regression showed that only MFR (P = 0.01) was a predictor of all-cause mortality. Univariate Cox regression analysis showed that both MFR and Stress MBF were predictors of the composite endpoint of MACE (P < 0.001 and P = 0.01, respectively).

CONCLUSION

Quantitative assessment of myocardial perfusion may predict all-cause mortality and MACE in patients with chest pain and normal coronary arteries in the long-term follow-up.

Multimodality Imaging for the Assessment of Severe Aortic Stenosis

Aortic stenosis is the most common type of valvular heart disease. Aortic stenosis is characterized both by progressive valve narrowing and the left ventricular remodeling response that ensues. In aortic stenosis, therapeutic decision essentially depends on symptomatic status, stenosis severity, and status of left ventricular systolic function. Imaging is fundamental for the initial diagnostic work-up, follow-up, and selection of the optimal timing and type of intervention. Noninvasive imaging has played a pivotal role in enhancing our understanding of the complex pathophysiology underlying aortic stenosis, as well as disease progression in both the valve and myocardium. The present review provides the application of multimodality imaging in aortic stenosis.

Pathophysiological coronary and microcirculatory flow alterations in aortic stenosis

Regulation of coronary blood flow is maintained through a delicate balance of ventriculoarterial and neurohumoral mechanisms. The aortic valve is integral to the functions of these systems, and disease states that compromise aortic valve integrity have the potential to seriously disrupt coronary blood flow. Aortic stenosis (AS) is the most common cause of valvular heart disease requiring medical intervention, and the prevalence and associated socio-economic burden of AS are set to increase with population ageing. Valvular stenosis precipitates a cascade of structural, microcirculatory, and neurohumoral changes, which all lead to impairment of coronary flow reserve and myocardial ischaemia even in the absence of notable coronary stenosis. Coronary physiology can potentially be normalized through interventions that relieve severe AS, but normality is often not immediately achievable and probably requires continued adaptation. Finally, the physiological assessment of coronary artery disease in patients with AS represents an ongoing challenge, as the invasive physiological measures used in current cardiology practice are yet to be validated in this population. This Review discusses the key concepts of coronary pathophysiology in patients with AS through presentation of contemporary basic science and data from animal and human studies.

Coronary microvascular dysfunction in patients with acute coronary syndrome and no obstructive coronary artery disease

BACKGROUND

Between 10 and 15% of patients admitted for non-ST-segment elevation acute coronary syndrome (NSTE-ACS) show no obstructive coronary artery disease (NO-CAD) at angiography. Coronary microvascular spasm is a possible mechanism of the syndrome, but there are scarce data about coronary microvascular function in these patients.

OBJECTIVES

To assess coronary microvascular function in patients with NSTE-ACS and NO-CAD.

METHODS

We studied 30 patients (67 ± 10 years, 19 female) with NSTE-ACS and NO-CAD. Specific causes of NSTE-ACS presentation (e.g., variant angina, takotsubo disease, tachyarrhythmias, etc.) were excluded. Coronary blood flow (CBF) velocity response to IV ergonovine (6 µg/kg up to a maximal dose of 400 µg) was evaluated before discharge by transthoracic Doppler echocardiography. CBF response to IV adenosine (140 μg/kg/min) and cold pressor test (CPT) was also assessed after 1 month. Ten age- and sex-matched patients with non-cardiac chest pain served as controls. Vasoactive tests were repeated after 12 months in 10 NSTE-ACS patients.

RESULTS

The ergonovine/basal CBF velocity ratio was 0.79 ± 0.09 and 0.99 ± 0.01 in patients and controls, respectively (p < 0.001). The adenosine/basal CBF velocity ratio was 1.46 ± 0.2 and 3.25 ± 1.2 in patients and controls, respectively (p < 0.001), and the CPT/basal CBF velocity ratio was 1.36 ± 0.2 and 2.43 ± 0.3 in the 2 groups, respectively (p < 0.001). In 10 patients assessed after 12 months, CBF velocity responses to ergonovine, adenosine, and CPT were found to be unchanged.

CONCLUSIONS

Patients with NSTE-ACS and NO-CAD exhibit a significant coronary dysfunction, which seems to involve both an increased constrictor reactivity, likely mainly involving coronary microcirculation, and a reduced microvascular dilator function, both persisting at 12-month follow-up.

Late sodium channel blockade improves angina and myocardial perfusion in patients with severe coronary microvascular dysfunction: Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction ancillary study

BACKGROUND

In a prior trial of late sodium channel inhibition (ranolazine) among symptomatic subjects without obstructive coronary artery disease (CAD) and limited myocardial perfusion reserve index (MPRI), we observed no improvement in angina or MPRI, overall. Here we describe the clinical characteristics and myocardial perfusion responses of a pre-defined subgroup who had coronary flow reserve (CFR) assessed invasively.

METHODS

Symptomatic patients without obstructive CAD and limited MPRI in a randomized, double-blind, crossover trial of ranolazine vs. placebo were subjects of this prespecified substudy. Because we had previously observed that adverse outcomes and beneficial treatment responses occurred in those with lower CFR, patients were subgrouped by CFR <2.5 vs ≥2.5. Symptoms were assessed using the Seattle Angina Questionnaire and the SAQ-7, and left-ventricular volume and MPRI were assessed by magnetic resonance imaging (MRI). Coronary angiograms, CFR, and MRI data were analyzed by core labs masked to treatment and patient characteristics.

RESULTS

During qualifying coronary angiography, 81 patients (mean age 55 years, 98% women) had invasively determined CFR 2.69 ± 0.65 (mean ± SD; range 1.4-5.5); 43% (n = 35) had CFR <2.5. Demographic and symptomatic findings did not differ comparing CFR subgroups. Those with low CFR had improved angina (p = 0.04) and midventricular MPRI (p = 0.03) with ranolazine vs placebo. Among patients with low CFR, reduced left-ventricular end-diastolic volume predicted a beneficial angina response.

CONCLUSIONS

Symptomatic patients with CFR <2.5 and no obstructive CAD had improved angina and myocardial perfusion with ranolazine, supporting the hypothesis that the late sodium channel is important in management of coronary microvascular dysfunction.

TRIAL REGISTRATION

clinicaltrials.gov Identifier NCT01342029.

'Primary' Microvascular Angina: Clinical Characteristics, Pathogenesis and Management

Microvascular angina (MVA), i.e. angina caused by abnormalities of the coronary microcirculation, is increasingly recognised in clinical practice. The pathogenetic mechanisms of MVA are heterogeneous and may involve both structural and functional alterations of coronary microcirculation, and functional abnormalities may variably involve an impairment of coronary microvascular dilatation and an increased microvascular constrictor activity. Both invasive and non-invasive diagnostic tools exist to identify patients with MVA in clinical practice. Prognosis has been reported to be good in primary MVA patients, although the prognostic implications of coronary microvascular dysfunction (CMVD) in more heterogeneous populations of angina patients need further assessment. Management of primary MVA can be challenging, but pharmacological and non-pharmacological treatments exist that allow satisfactory control of symptoms in most patients.

Diagnosis of Microvascular Angina Using Cardiac Magnetic Resonance

BACKGROUND

In patients with angina and nonobstructive coronary artery disease (NOCAD), confirming symptoms due to coronary microvascular dysfunction (CMD) remains challenging. Cardiac magnetic resonance (CMR) assesses myocardial perfusion with high spatial resolution and is widely used for diagnosing obstructive coronary artery disease (CAD).

OBJECTIVES

The goal of this study was to validate CMR for diagnosing microvascular angina in patients with NOCAD, compared with patients with obstructive CAD and correlated to the index of microcirculatory resistance (IMR) during invasive coronary angiography.

METHODS

Fifty patients with angina (65 ± 9 years of age) and 20 age-matched healthy control subjects underwent adenosine stress CMR (1.5- and 3-T) to assess left ventricular function, inducible ischemia (myocardial perfusion reserve index [MPRI]; myocardial blood flow [MBF]), and infarction (late gadolinium enhancement). During subsequent angiography within 7 days, 28 patients had obstructive CAD (fractional flow reserve [FFR] ≤0.8) and 22 patients had NOCAD (FFR >0.8) who underwent 3-vessel IMR measurements.

RESULTS

In patients with NOCAD, myocardium with IMR <25 U had normal MPRI (1.9 ± 0.4 vs. controls 2.0 ± 0.3; p = 0.49); myocardium with IMR ≥25 U had significantly impaired MPRI, similar to ischemic myocardium downstream of obstructive CAD (1.2 ± 0.3 vs. 1.2 ± 0.4; p = 0.61). An MPRI of 1.4 accurately detected impaired perfusion related to CMD (IMR ≥25 U; FFR >0.8) (area under the curve: 0.90; specificity: 95%; sensitivity: 89%; p < 0.001). Impaired MPRI in patients with NOCAD was driven by impaired augmentation of MBF during stress, with normal resting MBF. Myocardium with FFR >0.8 and normal IMR (<25 U) still had blunted stress MBF, suggesting mild CMD, which was distinguishable from control subjects by using a stress MBF threshold of 2.3 ml/min/g with 100% positive predictive value.

CONCLUSIONS

In angina patients with NOCAD, CMR can objectively and noninvasively assess microvascular angina. A CMR-based combined diagnostic pathway for both epicardial and microvascular CAD deserves further clinical validation.

Why names matter for women: MINOCA/INOCA (myocardial infarction/ischemia and no obstructive coronary artery disease)

The syndromes of myocardial infarction/myocardial ischemia with No Obstructive Coronary Artery Disease (MINOCA/INOCA) are increasingly evident. A majority of these patients have coronary microvascular dysfunction. These patients have elevated risk for a cardiovascular event (including acute coronary syndrome, myocardial infarction, stroke, and repeated cardiovascular procedures) and appear to be at higher risk for development of heart failure with preserved ejection fraction. Terminology such as coronary artery disease or coronary heart disease is often synonymous with obstructive atherosclerosis in the clinician's mind, leaving one at a loss to recognize or explain the phenomenon of MINOCA and INOCA with elevated risk. We review the available literature regarding stable and unstable ischemic heart disease that suggests that use of the ischemic heart disease (IHD) terminology matters for women, and should facilitate recognition of risk to provide potential treatment targets and optimized health.

Coronary microvascular dysfunction in diabetes mellitus

The significance, mechanisms and consequences of coronary microvascular dysfunction associated with diabetes mellitus are topics into which we have insufficient insight at this time. It is widely recognized that endothelial dysfunction that is caused by diabetes in various vascular beds contributes to a wide range of complications and exerts unfavorable effects on microcirculatory regulation. The coronary microcirculation is precisely regulated through a number of interconnected physiological processes with the purpose of matching local blood flow to myocardial metabolic demands. Dysregulation of this network might contribute to varying degrees of pathological consequences. This review discusses the most important findings regarding coronary microvascular dysfunction in diabetes from pre-clinical and clinical perspectives.

Rapid rest/stress regadenoson ungated perfusion CMR for detection of coronary artery disease in patients with atrial fibrillation

Cardiovascular magnetic resonance (CMR) perfusion has been established as a useful imaging modality for the detection of coronary artery disease (CAD). However, there are several limitations when applying standard, ECG-gated stress/rest perfusion CMR to patients with atrial fibrillation (AF). In this study we investigate an approach with no ECG gating and a rapid rest/stress perfusion protocol to determine its accuracy for detection of CAD in patients with AF. 26 patients with AF underwent a rapid rest/regadenoson stress CMR perfusion imaging protocol, and all patients had X-ray coronary angiography. An ungated radial myocardial perfusion sequence was used. Imaging protocol included: rest perfusion image acquisition, followed nearly immediately by administration of regadenoson to induce hyperemia, 60 s wait, and stress image acquisition. CMR perfusion images were interpreted by three blinded readers as normal or abnormal. Diagnostic accuracy was evaluated by comparison to X-ray angiography. 21 of the CMR rest/stress perfusion scans were negative, and 5 were positive by angiography criteria. Majority results of the ungated datasets from all of the readers showed a sensitivity, specificity and accuracy of 80, 100 and 96%, respectively, for detection of CAD. An ungated, rapid rest/stress regadenoson perfusion CMR protocol appears to be useful for the diagnosis of obstructive CAD in patients with AF.

Ischemia and No Obstructive Coronary Artery Disease (INOCA): Developing Evidence-Based Therapies and Research Agenda for the Next Decade

The Cardiovascular Disease in Women Committee of the American College of Cardiology, in conjunction with interested parties (from the National Heart, Lung, and Blood Institute, American Heart Association, and European Society of Cardiology), convened a working group to develop a consensus on the syndrome of myocardial ischemia with no obstructive coronary arteries. In general, these patients have elevated risk for a cardiovascular event (including acute coronary syndrome, heart failure hospitalization, stroke, and repeat cardiovascular procedures) compared with reference subjects and appear to be at higher risk for development of heart failure with preserved ejection fraction. A subgroup of these patients also has coronary microvascular dysfunction and evidence of inflammation. This document provides a summary of findings and recommendations for the development of an integrated approach for identifying and managing patients with ischemia with no obstructive coronary arteries and outlines knowledge gaps in the area. Working group members critically reviewed available literature and current practices for risk assessment and state-of-the-science techniques in multiple areas, with a focus on next steps needed to develop evidence-based therapies. This report presents highlights of this working group review and a summary of suggested research directions to advance this field in the next decade.

Coronary Microvascular Dysfunction as a Mechanism of Angina in Severe AS: Prospective Adenosine-Stress CMR Study

BACKGROUND

Although a common symptom in patients with severe aortic stenosis (AS) without obstructive coronary artery disease (CAD), little is known about the pathogenesis of exertional angina.

OBJECTIVES

This study sought to prove that microvascular dysfunction is responsible for chest pain in patients with severe AS and normal epicardial coronary arteries using adenosine-stress cardiac magnetic resonance (CMR) imaging.

METHODS

Between June 2012 and April 2015, 117 patients with severe AS without obstructive CAD and 20 normal controls were enrolled prospectively. After exclusions, study patients were divided into 2 groups according to presence of exertional chest pain: an angina group (n = 43) and an asymptomatic group (n = 41), and the semiquantitative myocardial perfusion reserve index (MPRI) was calculated.

RESULTS

MPRI values were significantly lower in severe AS patients than in normal controls (0.90 ± 0.31 vs. 1.25 ± 0.21; p < 0.001), and were much lower in the angina group than the asymptomatic group (0.74 ± 0.25 vs. 1.08 ± 0.28; p < 0.001). In logistic regression analysis, the only independent predictor for angina was MPRI (odds ratio: 0.003; p < 0.001). Univariate associations with MPRI were identified for diastolic blood pressure, E/e' ratio, left ventricular volume and ejection fraction, cardiac index, presence of late gadolinium enhancement, and left ventricular mass index (LVMI). In multivariate analysis, LVMI was the strongest contributing factor to MPRI (standardization coefficient: -0.428; p < 0.001).

CONCLUSIONS

Our results suggest that, in patients with severe AS without obstructive CAD, angina is related to impaired coronary microvascular function along with LV hypertrophy detectable by semiquantitative MPRI using adenosine-stress CMR.

CLINICAL TRIAL REGISTRATION

NCT02575768.

First-pass myocardial perfusion MRI with reduced subendocardial dark-rim artifact using optimized Cartesian sampling

PURPOSE

The presence of subendocardial dark-rim artifact (DRA) remains an ongoing challenge in first-pass perfusion (FPP) cardiac magnetic resonance imaging (MRI). We propose a free-breathing FPP imaging scheme with Cartesian sampling that is optimized to minimize the DRA and readily enables near-instantaneous image reconstruction.

MATERIALS AND METHODS

The proposed FPP method suppresses Gibbs ringing effects-a major underlying factor for the DRA-by "shaping" the underlying point spread function through a two-step process: 1) an undersampled Cartesian sampling scheme that widens the k-space coverage compared to the conventional scheme; and 2) a modified parallel-imaging scheme that incorporates optimized apodization (k-space data filtering) to suppress Gibbs-ringing effects. Healthy volunteer studies (n = 10) were performed to compare the proposed method against the conventional Cartesian technique-both using a saturation-recovery gradient-echo sequence at 3T. Furthermore, FPP imaging studies using the proposed method were performed in infarcted canines (n = 3), and in two symptomatic patients with suspected coronary microvascular dysfunction for assessment of myocardial hypoperfusion.

RESULTS

Width of the DRA and the number of DRA-affected myocardial segments were significantly reduced in the proposed method compared to the conventional approach (width: 1.3 vs. 2.9 mm, P < 0.001; number of segments: 2.6 vs. 8.7; P < 0.0001). The number of slices with severe DRA was markedly lower for the proposed method (by 10-fold). The reader-assigned image quality scores were similar (P = 0.2), although the quantified myocardial signal-to-noise ratio was lower for the proposed method (P < 0.05). Animal studies showed that the proposed method can detect subendocardial perfusion defects and patient results were consistent with the gold-standard invasive test.

CONCLUSION

The proposed free-breathing Cartesian FPP imaging method significantly reduces the prevalence of severe DRAs compared to the conventional approach while maintaining similar resolution and image quality.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:542-555.

Stress Cardiac MRI in Women With Myocardial Infarction and Nonobstructive Coronary Artery Disease

BACKGROUND

In a prospective study, cardiac MRI (CMR) and intravascular ultrasound were performed in women with myocardial infarction (MI) and nonobstructive coronary artery disease (MINOCA). Forty participants underwent adenosine-stress CMR (sCMR).

HYPOTHESIS

Abnormal perfusion may co-localize with ischemic late gadolinium enhancement (LGE) and T2-weighted signal hyperintensity (T2+), suggesting microvascular dysfunction contributed to MI.

METHODS

Qualitative perfusion analysis was performed by 2 independent readers. Abnormal myocardial perfusion reserve index (MPRI) was defined as global average ≤1.84.

RESULTS

Abnormal rest perfusion was present in 10 patients (25%) and stress perfusion abnormalities in 25 (63%). Abnormal stress perfusion was not associated with LGE but tended to occur with T2+. Among patients with abnormal perfusion and LGE, the LGE pattern was ischemic in half. The locations of abnormal perfusion and LGE matched in 75%, T2+ in 100%. Abnormal stress perfusion was not associated with plaque disruption and matched in location in 63%. MPRI was abnormal in 10 patients (25%) and was not associated with LGE, T2+ or plaque disruption.

CONCLUSIONS

Abnormal perfusion on sCMR is common among women with MINOCA. Abnormal perfusion usually co-localized with LGE and/or T2+ when present. Variability in LGE pattern leads to uncertainty about whether the finding of abnormal perfusion was cause or consequence of the tissue state leading to LGE. Low MPRI, possibly indicating diffuse microvascular disease, was observed with and without LGE and T2+. Multiple mechanisms may lead to abnormal perfusion on sCMR. Microvascular dysfunction may contribute to the pathogenesis of and coexist with other causes of MINOCA.

Stress cardiomyopathy: Is it limited to Takotsubo syndrome? Problems of definition

In 2006, Takotsubo syndrome (TTC) was described as a distinct type of stress-induced cardiomyopathy (stress cardiomyopathy). However, when thinking about Takotsubo cardiomyopathy from the viewpoints of the AHA and ESC classifications, 2 possible problems may arise. The first potential problem is that a forecast of disease outcome is lacking in the ESC classification, whereas the AHA only states that 'outcome is favorable with appropriate medical therapy'. However, based on the literature data, one can make a general conclusion that occurrence of myocardial lesions in TTC (i.e., myocardial fibrosis and contraction-band necrosis) causes the same effects as in other diseases with similar levels of myocardial damage and should not be considered to have a lesser impact on mortality. To summarise, TTC can cause not only severe complications such as pulmonary oedema, cardiogenic shock, and dangerous ventricular arrhythmias, but also damage to the myocardium, which can result in the development of potentially fatal conditions even after the disappearance of LV apical ballooning. The second potential problem arises from the definition of TTC as a stress cardiomyopathy in the AHA classification. In fact, the main factors leading to TTC are stress and microvascular anginas, since, as has been already discussed, coronary spasm can cause myocardium stunning, resulting in persistent apical ballooning. Thus, based on this review, 3 distinct types of stress cardiomyopathies exist (variant angina, microvascular angina, and TTC), with poor prognosis. Adding these diseases to the classification of cardiomyopathies will facilitate diagnosis and preventive prolonged treatment, which should include intensive anti-stress therapy.

Coronary Endothelial Dysfunction in Women With Type 2 Diabetes Measured by Coronary Phase Contrast Flow Velocity Magnetic Resonance Imaging

OBJECTIVE

The aim of this study was to determine if differences in coronary endothelial function are observed between asymptomatic women with type 2 diabetes mellitus (DM) and control subjects using coronary phase contrast flow velocity magnetic resonance imaging in response to cold pressor stress, an established endothelium-dependent vasodilatory stress.

METHODS

Phase contrast flow velocity imaging of the right coronary artery was performed in 7 asymptomatic premenopausal women with DM and 8 healthy female participants in response to the cold pressor test at 3 T.

RESULTS

There was no significant difference in percent increase in coronary flow velocity from rest to peak flow velocity between DM and control subjects (32% ± 22% vs 46% ± 17%; P = 0.11). However, percent increase in coronary flow velocity was lower in DM than in control subjects (-3% ± 14% vs 31% ± 30%; P = 0.01) during the second minute of cold pressor stress, when endothelial-mediated vasodilation should occur.

CONCLUSIONS

Asymptomatic women with DM demonstrate reduced coronary flow velocity during the second minute of cold pressor stress, indicating coronary endothelial dysfunction.

Cardiac Syndrome X: Update

Cardiac Syndrome X (CSX), characterized by angina-like chest discomfort, ST segment depression during exercise, and normal epicardial coronary arteries at angiography, is highly prevalent in women. CSX is not benign, and linked to adverse cardiovascular outcomes and a poor quality of life. Coronary microvascular and endothelial dysfunction and abnormal cardiac nociception have been implicated in the pathogenesis of CSX. Treatment includes life-style modification, anti-anginal, anti-atherosclerotic, and anti-ischemic medications. Non-pharmacological options include cognitive behavioral therapy, enhanced external counterpulsation, neurostimulation, and stellate ganglionectomy. Studies have shown the efficacy of individual treatments but guidelines outlining the best course of therapy are lacking.

Perfusion dyssynchrony analysis

AIMS

We sought to describe perfusion dyssynchrony analysis specifically to exploit the high temporal resolution of stress perfusion CMR. This novel approach detects differences in the temporal distribution of the wash-in of contrast agent across the left ventricular wall.

METHODS AND RESULTS

Ninety-eight patients with suspected coronary artery disease (CAD) were retrospectively identified. All patients had undergone perfusion CMR at 3T and invasive angiography with fractional flow reserve (FFR) of lesions visually judged >50% stenosis. Stress images were analysed using four different perfusion dyssynchrony indices: the variance and coefficient of variation of the time to maximum signal upslope (V-TTMU and C-TTMU) and the variance and coefficient of variation of the time to peak myocardial signal enhancement (V-TTP and C-TTP). Patients were classified according to the number of vessels with haemodynamically significant CAD indicated by FFR <0.8. All indices of perfusion dyssynchrony were capable of identifying the presence of significant CAD. C-TTP >10% identified CAD with sensitivity 0.889, specificity 0.857 (P < 0.0001). All indices correlated with the number of diseased vessels. C-TTP >12% identified multi-vessel disease with sensitivity 0.806, specificity 0.657 (P < 0.0001). C-TTP was also the dyssynchrony index with the best inter- and intra-observer reproducibility. Perfusion dyssynchrony indices showed weak correlation with other invasive and non-invasive measurements of the severity of ischaemia, including FFR, visual ischaemic burden, and MPR.

CONCLUSION

These findings suggest that perfusion dyssynchrony analysis is a robust novel approach to the analysis of first-pass perfusion and has the potential to add complementary information to aid assessment of CAD.