Primary Coronary Microvascular Dysfunction

Serum uric acid as a surrogate marker of favorable response to bevacizumab treatment in patients with metastatic colon cancer

Bevacizumab is a monoclonal antibody which is a vascular endothelial growth factor inhibitor. It obscures vascularization of tumor tissue and damages intratumoral microcirculation. The damaged intratumoral microcirculation leads to tissue hypoxia and results in increase of uric acid level. The main aim of our study was to investigate the relationship between uric acid change and response to bevacizumab therapy. This study included a total of 158 patients with metastatic colorectal cancer who had received bevacizumab therapy. The number of male patients was 100 (63.3 %) while female patients number was 58 (37.7 %). The median age was 61 (29-83). There was relationship between increase of uric acid level of third month uric acid level and stable disease (p < 0.001). There was a significant overall survival increased in the group with increased uric acid level (p < 0.001). The decline of CEA level was related to uric acid level (p < 0.022). In conclusion, this study is the first showing significant increases of serum uric acid in patients with metastatic colorectal cancer who favorably responded to chemotherapy with bevacizumab. But further studies are justified to test whether monitoring uric acid levels might predict clinical outcomes of patients with metastatic colorectal cancer.

Coronary Slow Flow Phenomenon Clinical Findings and Predictors

Background:

In some patients with chest pain, selective coronary angiography reveals slow contrast agent passage through the epicardial coronary arteries in the absence of stenosis. This phenomenon has been designated the slow coronary flow (SCF) phenomenon.

Objectives:

In this study, we aimed to describe the demographic and clinical findings and presence of common atherosclerosis risk factors in patients with the SCF phenomenon.

Patients and Methods:

Between October 2014 and March 2015, demographic data, clinical histories, atherosclerosis risk factors, and laboratory and angiographic findings were recorded for all consecutive patients scheduled for coronary angiography and diagnosed with the SCF phenomenon, as well as a control group (patients with normal epicardial coronary arteries; NECA). SCF was diagnosed based on the thrombolysis in myocardial infarction frame count (TFC). A TFC > 27 indicated a diagnosis of SCF phenomenon.

Results:

Among the 3600 patients scheduled for selective coronary angiography, 75 (2%) met the SCF criteria. SCF and NECA patients did not exhibit statistically significant differences in traditional risk factors except for hypertension, which was more prevalent in SCF than NECA patients (52% versus 31%, P = 0.008). A multivariable analysis indicated a low body mass index, presence of hypertension, low high-density lipoprotein cholesterol (HDL-c) level, and high hemoglobin level as independent predictors of the SCF phenomenon; of these, hypertension was the strongest predictor (odds ratio = 6.3, 95% confidence interval: 2.2 - 17.9, P = 0.001).

Conclusions:

The SCF phenomenon is relatively frequent, particularly among patients with acute coronary syndrome who are scheduled for coronary angiography. Hypertension, a low HDL-c level, and high hemoglobin level can be considered independent predictors of this phenomenon.

Coronary endothelial dysfunction in non-obstructive coronary artery disease: Risk, pathogenesis, diagnosis and therapy

Up to half of patients with signs and symptoms of stable ischemic heart disease have non-obstructive coronary artery disease (NoCAD). Recent evidence demonstrates that two-thirds of patients with NoCAD have demonstrable coronary endothelial dysfunction represented by microvascular or diffuse epicardial spasm following acetylcholine challenge. Patients with coronary endothelial dysfunction are recognized to have significant health services use and morbidity as well as increased risk of developing flow-limiting coronary artery disease and myocardial events, including death. Currently, there are few centers that test for this etiology owing to lack of knowledge, limited evidence for treatment options and invasive diagnostic strategies. This article reviews the pathophysiology, epidemiology, diagnosis and treatment of coronary endothelial dysfunction as a subgroup of NoCAD.

Diagnosis of coronary microvascular dysfunction - Present status

Definite clinical diagnosis of microvascular angina is not possible with the existing knowledge. Resting electrocardiogram may be normal, and exercise electrocardiogram may be unremarkable. Echocardiography usually does not show regional wall motion abnormalities. Transthoracic Doppler echocardiography can satisfactorily evaluate only left anterior descending coronary artery and that too in some patients. Radio-isotope imaging can detect only severe localized disease. Noninvasive diagnosis needs high index of suspicion. At present, definite diagnosis is based on documentation of normal epicardial coronaries, coronary flow reserve less than 2.5 on adenosine induced hyperemia, and absence of spasm of epicardial coronaries on acetylcholine provocation. Invasive evaluation is costly, needs sophisticated equipments and expertise. Therapeutic and prognostic implications of various parameters remains to be evaluated. At present invasive evaluation is recommended only for patients with intractable symptoms with unconfirmed diagnosis, requiring repeated hospitalization and evaluation with failure of empirical therapy.

[Diagnostics and therapy of chronic stable coronary artery disease : new guidelines of the European Society of Cardiology]

The European Society of Cardiology (ESC) guidelines on the management of stable coronary artery disease published in 2013 give practical recommendations for diagnostics and therapy. The approach depends on the clinical picture and symptoms of the patient, the severity and extent of ischemia, the degree and location of coronary stenoses, additional cardiac findings and finally on non-cardiac comorbidities. The selection of suitable diagnostic tools is based on the tabulated pretest probability for the presence of coronary artery disease which plays an important and central role in the diagnostic algorithm. An invasive approach is recommended only in patients with severe angina, i.e. a Canadian Cardiovascular Society (CCS) angina grading scale of ≥ CCS3 or in patients who are at high risk for death or myocardial infarction based on the results of the test used for detection of ischemia. Detailed therapeutic recommendations are given for medicinal and interventional or surgical therapy. Medicinal therapy includes drugs both for relief of symptoms and prevention of cardiovascular events. Recommendations are also given for the use of new antianginal drugs. A PCI is only indicated in vessels causing ischemia which can be verified by using fractional flow reserve measurements. The indications for PCI now also include patients with a low SYNTAX score and multivessel disease or left main stenosis; however, the optimal strategy should be individually determined in heart team discussions.

64Cu-CTS: A Promising Radiopharmaceutical for the Identification of Low-Grade Cardiac Hypoxia by PET

The subtle hypoxia underlying chronic cardiovascular disease is an attractive target for PET imaging, but the lead hypoxia imaging agents (64)Cu-2,3-butanedione bis(N4-methylthiosemicarbazone) (ATSM) and (18)F-fluoromisonidazole are trapped only at extreme levels of hypoxia and hence are insufficiently sensitive for this purpose. We have therefore sought an analog of (64)Cu-ATSM better suited to identify compromised but salvageable myocardium, and we validated it using parallel biomarkers of cardiac energetics comparable to those observed in chronic cardiac ischemic syndromes.

METHODS

Rat hearts were perfused with aerobic buffer for 20 min, followed by a range of hypoxic buffers (using a computer-controlled gas mixer) for 45 min. Contractility was monitored by intraventricular balloon, energetics by (31)P nuclear MR spectroscopy, lactate and creatine kinase release spectrophotometrically, and hypoxia-inducible factor 1-α by Western blotting.

RESULTS

We identified a key hypoxia threshold at a 30% buffer O2 saturation that induces a stable and potentially survivable functional and energetic compromise: left ventricular developed pressure was depressed by 20%, and cardiac phosphocreatine was depleted by 65.5% ± 14% (P < 0.05 vs. control), but adenosine triphosphate levels were maintained. Lactate release was elevated (0.21 ± 0.067 mmol/L/min vs. 0.056 ± 0.01 mmol/L/min, P < 0.05) but not maximal (0.46 ± 0.117 mmol/L/min), indicating residual oxidative metabolic capacity. Hypoxia-inducible factor 1-α was elevated but not maximal. At this key threshold, (64)Cu-2,3-pentanedione bis(thiosemicarbazone) (CTS) selectively deposited significantly more (64)Cu than any other tracer we examined (61.8% ± 9.6% injected dose vs. 29.4% ± 9.5% for (64)Cu-ATSM, P < 0.05).

CONCLUSION

The hypoxic threshold that induced survivable metabolic and functional compromise was 30% O2. At this threshold, only (64)Cu-CTS delivered a hypoxic-to-normoxic contrast of 3:1, and it therefore warrants in vivo evaluation for imaging chronic cardiac ischemic syndromes.

Coronary microvascular dysfunction: sex-specific risk, diagnosis, and therapy

Cardiovascular disease is the leading cause of death worldwide. In the presence of signs and symptoms of myocardial ischaemia, women are more likely than men to have no obstructive coronary artery disease (CAD). Women have a greater burden of symptoms than men, and are often falsely reassured despite the presence of ischaemic heart disease because of a lack of obstructive CAD. Coronary microvascular dysfunction should be considered as an aetiology for ischaemic heart disease with signs and symptoms of myocardial ischaemia, but no obstructive CAD. Coronary microvascular dysfunction is defined as impaired coronary flow reserve owing to functional and/or structural abnormalities of the microcirculation, and is associated with an adverse cardiovascular prognosis. Therapeutic lifestyle changes as well as antiatherosclerotic and antianginal medications might be beneficial, but clinical outcome trials are needed to guide treatment. In this Review, we discuss the prevalence, presentation, diagnosis, and treatment of coronary microvascular dysfunction, with a particular emphasis on ischaemic heart disease in women.

Current developments and future applications of intracoronary hemodynamics

Intracoronary hemodynamic assessment of the physiologic significance of coronary lesions improves clinical outcomes in patients with coronary artery disease. Coronary flow velocity reserve, fractional flow reserve, instantaneous wave-free ratio, and index of microcirculatory resistance utilize sensor-mounted guidewires to approximate coronary flow. Coronary flow velocity reserve and fractional flow reserve rely on pharmacologic administration of adenosine to achieve hyperemia and diagnose epicardial lesion severity. As an adenosine-free index, the instantaneous wave-free ratio utilizes a wave-free period in the mid-late diastole during which resistance is constant and low to assess lesion significance. The index of microcirculatory resistance combines hyperemic pressure measurements with thermodilution to quantify microvascular resistance. We review the physiology, clinical trials, and clinical applications of these invasive hemodynamic assessments.

Is there a role for ivabradine beyond its conventional use?

Results of recent clinical trials in patients with stable angina and chronic heart failure have successfully demonstrated a beneficial role of use of ivabradine in addition to the conventional therapy. Based on the results of these trials, the aim of our review was to give an overview of the literature about the use of ivabradine in clinical settings outside its usual purpose.

Poor Tolerance and Limited Effects of Isosorbide-5-Mononitrate in Microvascular Angina

Objectives: To assess the effects of isosorbide-5-mononitrate (ISMN) in patients with microvascular angina (MVA). Methods: We randomized 20 MVA patients, treated with a β-blocker or a calcium antagonist, to 60 mg slow-release ISMN (halved to 30 mg if not tolerated) or placebo once a day for 4 weeks; the patients were then switched to the other treatment for another 4 weeks. Their clinical status was assessed with the Seattle Angina Questionnaire (SAQ) and the EuroQoL score for quality of life. The exercise stress test (EST), coronary blood flow (CBF) response to nitrate and the cold pressor test (CPT), brachial artery flow-mediated dilation (FMD) and nitrate-mediated dilation (NMD) were also assessed. Results: Nine patients (45%) did not complete the ISMN phase due to side effects; 2 patients refused a follow-up. Nine patients completed the study. The SAQ and EuroQoL scores were significantly better with ISMN than with placebo, although the differences were small. No differences were found between the treatments in the EST results, CBF response to nitroglycerin (p = 0.55) and the CPT (p = 0.54), FMD (p = 0.26) and NMD (p = 0.35). Conclusions: In this study, a high proportion of MVA patients showed an intolerance to ISMN; in those tolerating the drug, significant effects on their angina status were observed, but the benefit appeared to be modest and independent of effects on coronary microvascular function.

Microvascular angina: angina that predominantly affects women

In women receiving evaluation for suspected ischemic symptoms, a "normal" diagnosis is five times more common than it is in men. These women are often labeled as having cardiac syndrome X, also known as microvascular angina (MVA). MVA is defined as angina pectoris caused by abnormalities of the small coronary arteries, and is characterized by effort chest pain and evidence of myocardial ischemia with a non-invasive stress test, although the coronary arteries can appear normal or near normal by angiography. MVA patients are often neglected due to the assumption of a good prognosis. However, MVA has important prognostic implications and a proper diagnosis is necessary in order to relieve the patients' symptoms and improve clinical outcomes. The coronary microvasculature cannot be directly imaged using coronary angiography, due to the small diameter of the vessels; therefore, the coronary microvascular must be assessed functionally. Treatment of MVA initially includes standard anti-ischemic drugs (β-blockers, calcium antagonists, and nitrates), although control of symptoms is often insufficient. In this review, we discuss the pathophysiology, diagnosis, and treatment of MVA.

Microvascular angina: an update on diagnosis and treatment

ABSTRACT 

Many patients with chest pain who are relieved to learn that they have no obstructive stenoses at diagnostic angiography are misclassified as having noncardiac chest pain. Only recently have we developed the conceptual framework and diagnostic tools to understand that ischemic heart disease is not exclusively caused by obstructive coronary artery disease, but often has its origin in the microcirculation. This article will focus on the diagnosis and treatment of microvascular angina as a cause of myocardial ischemia in patients with abnormal but ‘normal appearing’ coronary arteries.

Single-wire pressure and flow velocity measurement for quantifying microvascular dysfunction in patients with coronary vasospastic angina

Endothelial and vascular smooth muscle dysfunction of epicardial coronary arteries play a pivotal role in the pathogenesis of vasospastic angina (VSA). However, coronary microvascular (MV) function in patients with VSA is not fully understood. In the present study, subjects without coronary obstruction were divided into two groups according to the acetylcholine provocation test: VSA group ( n = 29) and non-VSA group ( n = 21). Hyperemic MV resistance (hMR) was measured using a dual-sensor (Doppler velocity and pressure)-equipped guidewire, and guidewire-derived hemodynamic parameters were compared. There were no between-group differences in clinical demographics, including potential factors affecting MV function (e.g., diabetes). Although coronary flow velocity reserve was similar between the two groups [2.4 ± 1.0 (VSA group) vs. 2.4 ± 0.9 (non-VSA group); P = 0.8], coronary vessel resistance and hMR were significantly elevated in the VSA group compared with the non-VSA group (2.6 ± 3.1 vs. 1.2 ± 0.8, P = 0.04; 1.9 ± 0.6 vs. 1.6 ± 0.5, P = 0.03, respectively). Coronary vasospasm, older age, E/e', and estimated glomerular filtration rate were significantly associated with MV dysfunction [defined as ≥ median value of hMR (1.6)] in univariate analysis. Coronary vasospasm most strongly predicted higher hMR in multivariate logistic regression analysis (odds ratio, 4.61; 95% confidence interval, 0.98–21.60; P = 0.053). In conclusion, coronary MV resistance is impaired in patients with VSA compared with non-VSA patients, whereas coronary flow velocity reserve is maintained at normal levels in both groups. In vivo assessment of hMR might be a promising index of coronary MV dysfunction in patients with VSA.

Pilot study testing the effect of physical training over the myocardial perfusion and quality of life in patients with primary microvascular angina

BACKGROUND

Primary microvascular angina (PMA) is a common clinical condition associated to negative impact on quality of life (QOL) and reduced physical capacity. This study aimed at evaluating the effects of aerobic physical training (APT) on myocardial perfusion, physical capacity, and QOL in patients with PMA.

METHODS

We investigated 12 patients (53.8 ± 9.7 years old; 7 women) with PMA, characterized by angina, angiographycally normal coronary arteries, and reversible perfusion defects (RPDs) detected on (99m)Tc-sestamibi-SPECT myocardial perfusion scintigraphy (MPS). At baseline and after 4 month of APT, the patients underwent MPS, cardiopulmonary test, and QOL questionnaire. Stress-rest MPS images were visually analyzed by attributing semi-quantitative scores (0 = normal; 4 = absent uptake), using a 17-segment left ventricular model. Summed stress, rest, and difference scores (SDS) were calculated.

RESULTS

In comparison to the baseline, in the post-training we observed a significant increase in peak-VO2 (19.4 ± 4.8 and 22.1 ± 6.2 mL·kg(-1)·minute(-1), respectively, P = .01), reduction of SDS (10.1 ± 8.8 and 2.8 ± 4.9, P = .008), and improvement in QOL scores.

CONCLUSIONS

Physical training in patients with PMA is associated with reduction of myocardial perfusion abnormalities, increasing of physical capacity, and improvement in QOL. The findings of this hypothesis-generating study suggest that APT can be a valid therapeutic option for patients with PMA.

Etiopathogenesis of microvascular angina: caveats in our knowledge

Nearly 50% of subjects of coronary artery disease suffer from coronary microvascular dysfunction. Various etiopathogenetic factors have been proposed by different workers but no hypothesis can explain the genesis of microvascular angina in all patients. We have made an attempt to review the literature to find caveats in our knowledge so that future studies can be better designed.

Stable angina pectoris

The stable coronary artery disease (SCAD) population is a heterogeneous group of patients both for clinical presentations and for different underlying mechanisms. The recent European Society of Cardiology guidelines extensively review SCAD from its definition to patients' diagnostic and therapeutic management. In this review, we deal with five topics that, in our opinion, represent the most intriguing, novel and/or clinically relevant aspects of this complex coronary condition. Firstly, we deal with a peculiar SCAD population: patients with angina and 'normal' coronary arteries. Secondly, we reinforce the clinical importance of a diagnostic approach based on the pretest probability of disease. Thirdly, we review and critically discuss the novel pharmacological therapies for SCAD patients. Finally, we analyse the results of the most recent clinical trials comparing revascularization versus optimal medical therapy in SCAD patients and review the currently recommended use of intracoronary functional evaluation of stenosis.

A prospective study of C-reactive protein as a state marker in Cardiac Syndrome X

Cardiac Syndrome X (CSX), the presence of angina pectoris despite normal epicardial coronary arteries seen on invasive angiography, is known to be associated with an elevation of several inflammatory biomarkers, suggesting a possible role for inflammation in its pathogenesis. We sought to establish if C-reactive protein (CRP) levels varied with disease severity and so whether it is a state or trait marker. We studied 16 CSX patients with typical angina pectoris, normal coronary arteries and an electrically positive exercise stress test (EST) and 13 age- and sex-matched healthy controls (HC). CSX patients were followed up at a subsequent visit with repeated exercise stress testing and CRP measurement. We found that CRP levels were significantly higher in the CSX group compared to the HC (1.5 [0.8-4.5] v 0.8 [0.4-1.4] mg/L, p=0.02). This elevation in CRP persisted throughout the study length. CRP correlated with time to symptoms on EST at enrolment and at the second visit (r=-0.690, df=10, p=0.013 and r=-0.899, df=4, p=0.015, respectively). At the follow-up visit, 50% of CSX patients developed electrically and symptomatically negative ESTs. The mean CRP of this group was significantly lower than that of the CSX patients with ongoing symptoms and positive ESTs (1.2±0.2 v 2.8±0.6mg/L, p=0.018) and did not differ significantly from that of healthy controls. CRP levels also dropped in patients whose symptoms improved while they increased in patients who became more symptomatic (p=0.027). We conclude that the results of this small study support the concept of CSX being an inflammatory-mediated condition with CRP levels prospectively varying with functional measures of disease severity. This indicates that CRP is a state marker in CSX.

Ranolazine: Drug overview and possible role in primary microvascular angina management

Ranolazine is a novel well-tolerated anti-ischemic drug, which selectively inhibits late sodium current and exerts metabolic properties without any hemodynamic effect. Ranolazine has been approved as a second-line medical treatment for symptomatic stable coronary artery disease. Primary microvascular angina (MVA) is suspected when angina symptoms occur in patients with demonstrated myocardial ischemia, absence of myocardial disease and normal coronary artery angiography. Recent clinical data suggest that MVA represents a complex entity, which has been increasingly recognized as a significant cause of morbidity. High variability and low response to traditional anti-anginal treatment characterize primary MVA. Despite the fact that clinical and preclinical evidence provides information regarding ranolazine usefulness in primary MVA management, only three recent small randomized trials have investigated this issue. By selecting peer-reviewed literature in Pubmed and Cochrane Library, this review provides an overview on ranolazine pharmacology and efficacy, focusing on recent evidence suggesting its usefulness in management of primary MVA.

Plasma soluble urokinase-type plasminogen activator receptor level is independently associated with coronary microvascular function in patients with non-obstructive coronary artery disease

BACKGROUND

Soluble urokinase-type plasminogen activator receptor (suPAR) is a novel biomarker released from leukocytes and endothelial cells that has been associated with atherosclerotic cardiovascular disease. We hypothesized that plasma suPAR level is an independent predictor of coronary microvascular function.

METHODS

Coronary blood flow velocity and plasma suPAR levels were evaluated in patients with non-obstructive coronary artery disease. Coronary flow reserve (CFR) was calculated as the ratio of hyperemic to basal average peak blood flow velocity and coronary microvascular dysfunction was defined as CFR ≤ 2.0 in the setting of a fractional flow reserve value of ≥0.75. Plasma suPAR levels were measured using ELISA technique. The association between suPAR and CFR was investigated using univariate and multivariate regression analyses.

RESULTS

In 66 patients, 47% were men, 26% had diabetes, 68% had hypertension and 76% had dyslipidemia. Mean age was 55 ± 12 years and median suPAR level 2.82 (2.08-3.40) ng/mL. Plasma suPAR levels correlated with age (r = 0.31, p = 0.01), body mass index (r = 0.25, p = 0.04) and high-sensitivity C-reactive protein (hs-CRP) (r = 0.33, p = 0.009). While median suPAR level was not significantly different in patients with different cardiovascular risk factors, patients on statin therapy had significantly higher suPAR level (p = 0.03). SuPAR correlated negatively with CFR and, after multivariate adjustment for established cardiovascular risk factors, medications profiles and hs-CRP, suPAR remained an independent predictor of CFR (B = -0.30, p = 0.04), indicating an independent association between suPAR level and coronary microvascular function.

CONCLUSIONS

In this cross-sectional study, plasma suPAR level was an independent predictor of coronary microvascular function. Larger prospective clinical trials are warranted to investigate the prognostic value of this novel biomarker and the role of immune dysregulation in coronary microvascular disease.

Acute myocardial infarction with no obstructive coronary atherosclerosis: mechanisms and management

Myocardial infarction (MI) with no obstructive coronary atherosclerosis (MINOCA) is a syndrome with different causes. Its prevalence ranges between 5 and 25% of all MIs. The prognosis is extremely variable, depending on the causes of MINOCA. Clinical history, echocardiography, coronary angiography, and left ventriculography represent the first-level diagnostic investigations. Nevertheless, additional tests are required in order to establish its specific cause, thus allowing an appropriate risk stratification and treatment. We review pathogenesis, diagnosis, prognosis, and therapy of MINOCA and propose an algorithm for its management.

Regulation of coronary blood flow in health and ischemic heart disease

The major factors determining myocardial perfusion and oxygen delivery have been elucidated over the past several decades, and this knowledge has been incorporated into the management of patients with ischemic heart disease (IHD). The basic understanding of the fluid mechanical behavior of coronary stenoses has also been translated to the cardiac catheterization laboratory where measurements of coronary pressure distal to a stenosis and coronary flow are routinely obtained. However, the role of perturbations in coronary microvascular structure and function, due to myocardial hypertrophy or coronary microvascular dysfunction, in IHD is becoming increasingly recognized. Future studies should therefore be aimed at further improving our understanding of the integrated coronary microvascular mechanisms that control coronary blood flow, and of the underlying causes and mechanisms of coronary microvascular dysfunction. This knowledge will be essential to further improve the treatment of patients with IHD.

Assessment of coronary hemodynamics and vascular function

Coronary blood flow closely matches to metabolic demands of heart and myocardial oxygen consumption and is conditioned by function of coronary resistance vessels. The microvascular endothelium of coronary resistance vessels is exposed to a spatially and temporally regulated input from cardiomyocytes and the haemodynamic forces of the cardiac cycle. Functional measurements of coronary pressure and flow are important approaches that provide complementary information on the function of coronary vessel function that could not be assessed by the methods utilized for the anatomic characterization of coronary disease, such as coronary angiography. The goal of this paper is to review the methodologies for assessment of coronary vascular function and haemodynamics which are utilized in research and to discuss their potential applicability in the clinical settings.

A case of coronary microvascular spasm with slow flow induced by the intracoronary acetylcholine provocation test

Microvascular angina is a rare condition in which myocardial ischemia is caused by microvascular dysfunction without any abnormalities of the epicardial coronary arteries. In clinical practice, it is difficult to diagnose because the microvascular alterations cannot be detected by conventional angiography. Herein we present a rare case of a 67-year-old woman with unstable angina pectoris in whom considerably slow coronary flow was induced by the acetylcholine provocation test with mild epicardial arterial spasm, suggesting the presence of microvascular spasm. Moreover, we show that β-methyl-p-[(123)I]-iodophenyl-pentadecanoic ((123)I-BMIPP) single-photon emission computed tomography imaging is useful for proving myocardial ischemia.

Understanding of chest pain in microvascular disease proved by cardiac magnetic resonance image (UMPIRE): study protocol for a randomized controlled trial

Background

Microvascular angina (MVA) is characterized by anginal chest pain, an abnormal stress test, and normal coronary arteries on coronary angiography. Although the exact pathogenesis remains unclear, endothelial dysfunction is a contributing factor. To date, there exists no specific therapy for this disease. Phosphodiesterase-5 inhibitor improves the endothelial function and subsequently microvascular circulation. The aim of this study is to identify whether udenafil offers benefits in the treatment of MVA in female patients, who have a perfusion defect in their cardiac magnetic resonance image (CMR), but normal coronary arteries.

Methods/Design

The ‘Understanding of Chest Pain in Microvascular Disease Proved by Cardiac Magnetic Resonance Image: (UMPIRE)’ trial is a multicenter, prospective, randomized, placebo controlled trial, designed to evaluate the effect of udenafil on myocardial ischemia and symptoms in female patients with MVA. The myocardial ischemia will be quantified by myocardial stress perfusion defect in CMR. A total of 80 patients with proven perfusion defect in adenosine-stress CMR will be randomly assigned to either the udenafil treatment group (daily dose of 100 mg) or the placebo group for three months. The primary endpoint is >25% improvement in perfusion defect size in adenosine-stress CMR from baseline. The secondary endpoints include <25% improvement in perfusion defect size, chest pain frequency, ST depression in stress test, Duke score in stress test, quality of life (QoL) assessment by SF-36 questionnaire, sexual dysfunction assessment by BISF-W (Brief Index of Sexual Functioning for Women) self-assessment questionnaire, and biomarkers for endothelial function.

Discussion

The UMPIRE trial is the first randomized controlled trial to evaluate the efficacy of udenafil in female MVA patients. If udenafil demonstrates cardioprotective effects, it may provide a novel therapeutic option to reduce myocardial ischemia and improve cardiac function in female MVA patients.

Trial registration

Clinical Trials.gov: NCT01769482 (registered on 20 November 2012).

Severity of myocardial fatty acid dysmetabolism induced by coronary spasm does not differ with Thrombolysis in Myocardial Infarction (TIMI) grade during intracoronary acetylcholine provocation tests

Whether additional intracoronary acetylcholine (ACH) injections are required for severe coronary spasm without limited coronary flow in the ACH provocation test remains unclear. We used (123)I-β-methyl-iodophenyl pentadecanoic acid ((123)I-BMIPP) to identify myocardial ischemic memory to compare the severity of myocardial fatty acid dysmetabolism among Thrombolysis in Myocardial Infarction (TIMI) grade flow.Thirteen hypertensive volunteers (mean age, 69.5 years) and 37 patients with VSA (mean age, 62.8 years) were enrolled. The patients with VSA were stratified according to TIMI flow grades of 3 (90% luminal narrowing; n = 12) or TIMI 0-2 (≥ 99% or total occlusion; n = 25) during ACH provocation tests. Two weeks after cardiac catheterization, (123)I-BMIPP myocardial scintigraphic images were obtained at 15 minutes (early) and at 4 hours (delayed) after tracer injection. The heart-to-mediastinum (H/M) ratio and washout rates (WR) were calculated from planar images.The TIMI 3 and TIMI 0-2 groups had significantly lower early and delayed H/M ratios than controls but the difference did not reach significance between the two groups (Early: 2.7 ± 0.5 versus 2.3 ± 0.4 and 2.2 ± 0.3, P = 0.024; Delayed: 2.4 ± 0.4 versus 1.8 ± 0.3 and 1.8 ± 0.3, P = 0.001). The washout rate was greater for TIMI 0-2 than the controls.The severity of myocardial fatty acid dysmetabolism did not differ between TIMI 3 and TIMI 0-2 coronary spasms. Additional ACH might not be required considering safety and the severity of coronary spams with TIMI 3 grade flow.

Precordial chest pain in patients with chronic Chagas disease

Precordial chest pain affects about 15% to 33% of patients with chronic Chagas disease. In the absence of megaesophagus, it should be ascribed to chronic Chagas heart disease. Precordial chest pain is atypical because it can usually neither be associated to physical exercise nor be alleviated by nitroglycerin. However, in certain circumstances, precordial chest pain can masquerade as acute coronary syndrome. Although obstructive coronary artery disease can occasionally be found, microvascular angina seems to be the mechanism behind such phenomenon. Precordial chest pain not always has a benign clinical course; sometimes, it can herald a dismal prognosis. On the basis of cases previously reported, it seems that nitrates, betablockers and/or calcium channel blockers can be of value in the treatment of this condition.

Do cardiac biomarkers NT-proBNP and hsTnT predict microvascular events in patients with type 2 diabetes? Results from the ADVANCE trial

OBJECTIVE

We investigated microvascular event risk in people with type 2 diabetes and assessed whether N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity troponin T (hsTnT) improved prediction.

RESEARCH DESIGN AND METHODS

We performed a case-cohort study, including 439 incident cases of microvascular events (new or worsening nephropathy or retinopathy) and 2,946 noncase subjects identified from participants in the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trial. NT-proBNP and hsTnT were measured in stored plasma samples using automated commercial assays.

RESULTS

After adjustment for age, sex, and randomized treatment, the hazard ratios for microvascular events per 1-SD increase in the log-transformed hsTnT and NT-proBNP were 1.67 (95% CI 1.51-1.85) and 1.63 (1.44-1.84), respectively. After further adjustment for classical and diabetes-related cardiovascular disease risk factors, the hazard ratios attenuated to 1.40 (1.24-1.58) and 1.41 (1.24-1.60), respectively. While the C statistic did not improve on addition of hsTnT or NT-proBNP for the total microvascular end point, a combination of both markers improved the prediction of nephropathy (P = 0.033) but not retinopathy (P = 0.72). The corresponding net reclassification indices in a three-risk category model (<10%, 10-15%, and >15% 5-year risk) for all microvascular events were 7.31% (95% CI 2.24-12.79) for hsTNT addition, 6.23% (1.74-11.5) for NT-proBNP addition, and 7.1% (1.5-12.9) for both markers together.

CONCLUSIONS

These data suggest that cardiac biomarkers moderately improve microvascular event risk prediction, in particular the risk of nephropathy. Further studies examining the value of this approach for trial design and clinical use are warranted.

Cardiac Syndrome X: update 2014

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.

Extension of the mitochondria dysfunction hypothesis of metabolic syndrome to atherosclerosis with emphasis on the endocrine-disrupting chemicals and biophysical laws

Metabolic syndrome and its component phenotypes, hyperglycemia, hypertension, (abdominal) obesity and hypertriglyceridemia, are major risk factors for atherosclerosis. Recently, associations between exposure to endocrine‐disrupting chemicals (EDCs), mitochondrial dysfunction, metabolic syndrome and atherosclerosis have been established, suggesting a possible common mechanism underlying these phenomena. Extending a previously proposed mitochondria dysfunction theory of metabolic syndrome and using biophysical laws, such as metabolic scaling, Murray's law and fractal geometry of the vascular branching system, we propose that atherosclerosis could be explained as an ill‐adaptive change occurring in nutrient‐supplying arteries in response to the decreasing tissue energy demand caused by tissue mitochondrial dysfunction. Various aspects of this new hypothesis are discussed.

Coronary microvascular dysfunction in women: an overview of diagnostic strategies

Coronary microvascular dysfunction (CMD) also known as syndrome X, is characterized by typical anginal symptoms, evidence of myocardial ischemia on non-invasive testing and normal to minimal coronary disease on coronary angiography. It has a female preponderance and has been detected in up to 50% of women presenting with chest pain symptoms. Definitive diagnosis of CMD is critical as recent evidence suggests that women with this condition are at increased risk of cardiovascular events in the future. Invasive coronary reactivity testing on coronary angiography is considered to be the 'gold standard' for diagnosis of CMD. Non-invasive imaging techniques such as PET and cardiac magnetic resonance hold promise for detection of CMD in the future.

The role of capillary transit time heterogeneity in myocardial oxygenation and ischemic heart disease

Ischemic heart disease (IHD) is characterized by an imbalance between oxygen supply and demand, most frequently caused by coronary artery disease (CAD) that reduces myocardial perfusion. In some patients, IHD is ascribed to microvascular dysfunction (MVD): microcirculatory disturbances that reduce myocardial perfusion at the level of myocardial pre-arterioles and arterioles. In a minority of cases, chest pain and reductions in myocardial flow reserve may even occur in patients without any other demonstrable systemic or cardiac disease. In this topical review, we address whether these findings might be caused by impaired myocardial oxygen extraction, caused by capillary flow disturbances further downstream. Myocardial blood flow (MBF) increases approximately linearly with oxygen utilization, but efficient oxygen extraction at high MBF values is known to depend on the parallel reduction of capillary transit time heterogeneity (CTH). Consequently, changes in capillary wall morphology or blood viscosity may impair myocardial oxygen extraction by preventing capillary flow homogenization. Indeed, a recent re-analysis of oxygen transport in tissue shows that elevated CTH can reduce tissue oxygenation by causing a functional shunt of oxygenated blood through the tissue. We review the combined effects of MBF, CTH, and tissue oxygen tension on myocardial oxygen supply. We show that as CTH increases, normal vasodilator responses must be attenuated in order to reduce the degree of functional shunting and improve blood-tissue oxygen concentration gradients to allow sufficient myocardial oxygenation. Theoretically, CTH can reach levels such that increased metabolic demands cannot be met, resulting in tissue hypoxia and angina in the absence of flow-limiting CAD or MVD. We discuss these predictions in the context of MVD, myocardial infarction, and reperfusion injury.

Physiological basis and long-term clinical outcome of discordance between fractional flow reserve and coronary flow velocity reserve in coronary stenoses of intermediate severity

BACKGROUND

Discordance between fractional flow reserve (FFR) and coronary flow velocity reserve (CFVR) may reflect important coronary pathophysiology but usually remains unnoticed in clinical practice. We evaluated the physiological basis and clinical outcome associated with FFR/CFVR discordance.

METHODS AND RESULTS

We studied 157 intermediate coronary stenoses in 157 patients, evaluated by FFR and CFVR between April 1997 and September 2006 in which revascularization was deferred. Long-term follow-up was performed to document the occurrence of major adverse cardiac events: cardiac death, myocardial infarction, or target vessel revascularization. Discordance between FFR and CFVR occurred in 31% and 37% of stenoses at the 0.75, and 0.80 FFR cut-off value, respectively, and was characterized by microvascular resistances during basal and hyperemic conditions. Follow-up duration amounted to 11.7 years (Q1-Q3, 9.9-13.3 years). Compared with concordant normal results of FFR and CFVR, a normal FFR with an abnormal CFVR was associated with significantly increased major adverse cardiac events rate throughout 10 years of follow-up, regardless of the FFR cut-off applied. In contrast, an abnormal FFR with a normal CFVR was associated with equivalent clinical outcome compared with concordant normal results: ≤ 3 years when FFR <0.75 was depicted abnormal and throughout 10 years of follow-up when FFR ≤ 0.80 was depicted abnormal.

CONCLUSIONS

Discordance of CFVR with FFR originates from the involvement of the coronary microvasculature. Importantly, the risk for major adverse cardiac events associated with FFR/CFVR discordance is mainly attributable to stenoses where CFVR is abnormal. This emphasizes the requirement of intracoronary flow assessment in addition to coronary pressure for optimal risk stratification in stable coronary artery disease.

Increased hyperaemic coronary microvascular resistance adds to the presence of myocardial ischaemia

AIMS

It has been argued that hyperaemic microvascular resistance (HMR), defined as the ratio of mean distal coronary pressure to flow velocity, is overestimated in the presence of a coronary stenosis compared to actual microvascular resistance (MR), due to neglecting collateral flow. We aimed to test the hypothesis that HMR allows accurate identification of microvascular functional abnormalities by evaluating the association between high or low HMR and the presence of myocardial ischaemia on non-invasive stress testing.

METHODS AND RESULTS

Myocardial perfusion scintigraphy was performed in 228 patients, with 299 lesions to identify reversible myocardial ischaemia. Intracoronary distal pressure and flow velocity were assessed during adenosine-induced hyperaemia (20-40 µg, intracoronary) to determine hyperaemic stenosis resistance (HSR) and HMR. HMR >1.9 mmHg/cm/s was defined as high. The diagnostic odds ratio (OR) for myocardial ischaemia for lesions associated with high compared to low HMR was 2.6 (95% confidence interval [CI]: 1.5-4.4; p<0.001) overall, 3.3 (95% CI: 1.2-9.0; p=0.02) for lesions with HSR >0.8 mmHg/cm/s, and 1.3 (95% CI: 0.6-2.9; p=0.52) for lesions with HSR ≤0.8 mmHg/cm/s.

CONCLUSIONS

The increased risk of myocardial ischaemia in the presence of high HMR, uncorrected for collateral flow, demonstrates that HMR is reflective of an increase in actual MR, identifying pertinent pathophysiological alterations in the microvasculature.