Relationship between endothelial function in the coronary and brachial arteries

Is the peripheral microcirculation a window into the human coronary microvasculature?

An increasing body of evidence suggests a pivotal role for the microvasculature in the development of cardiovascular disease. A dysfunctional coronary microvascular network, specifically within endothelial cells-the inner most cell layer of vessels-is considered a strong, independent risk factor for future major adverse cardiac events. However, challenges exist with evaluating this critical vascular bed, as many of the currently available techniques are highly invasive and cost prohibitive. The more easily accessible peripheral microcirculation has surfaced as a potential surrogate in which to study mechanisms of coronary microvascular dysfunction and likewise may be used to predict poor cardiovascular outcomes. In this review, we critically evaluate a variety of prognostic, physiological, and mechanistic studies in humans to answer whether the peripheral microcirculation can add insight into coronary microvascular health. A conceptual framework is proposed that the health of the endothelium specifically may link the coronary and peripheral microvascular beds. This is supported by evidence showing a correlation between human coronary and peripheral endothelial function in vivo. Although not a replacement for investigating and understanding coronary microvascular function, the microvascular endothelium from the periphery responds similarly to (patho)physiological stress and may be leveraged to explore potential therapeutic pathways to mitigate stress-induced damage.

Flow Mediated Dilation in Systemic Sclerosis: Association with clinical findings, capillaroscopic patterns and endothelial circulating markers

AIM

Endothelial dysfunction represents a key feature of the pathological process underlying micro and macro-vascular damage in Systemic Sclerosis (SSc). This study aims to improve knowledge of the physiopathology of vascular damage in SSc through the assessment of the endothelial dysfunction by Flow Mediated Dilation (FMD) and serum levels of circulating endothelial dysfunction markers and the correlation of macrovascular damage with clinical findings and microvascular capillaroscopic patterns.

METHODS

57 SSc patients and 37 healthy subjects were recruited. All included subjects underwent radial artery FMD test and Nailfold Video-Capillaroscopy; serum levels of Vascular Endothelial Growth Factor (VEGF), Vascular Cell Adhesion Molecule-1 (VCAM-1) and angiopoietin-2 were evaluated.

RESULTS

Compared to healthy subjects, in SSc patients lower FMD and higher time needed to obtain the maximal FMD responsewere observed, whereas serum levels of VEGF, VCAM-1, and angiopoietin-2 were significantly higher. The impairment of FMD values was associated with disease duration, pulmonary arterial hypertension, and digital ulcers and correlates with greater microvascular damage evaluated by Nailfold Video-Capillaroscopy… An inverse relationship between VEGF, angiopoietin-2, VCAM-1 levels and FMD was observed, but only VEGF and angiopoietin-2 were significantly higher in patients with digital ulcers and pulmonary arterial hypertension.

CONCLUSIONS

FMD ultrasound test and circulating levels of endothelial dysfuncion markers could be useful as biomarkers of vasculopathy and could be a helpful tool in the overall assessment of vascular injury in Systemic Sclerosis patients.

Endothelial cell dysfunction in cardiac disease: driver or consequence?

The vascular endothelium is a multifunctional cellular system which directly influences blood components and cells within the vessel wall in a given tissue. Importantly, this cellular interface undergoes critical phenotypic changes in response to various biochemical and hemodynamic stimuli, driving several developmental and pathophysiological processes. Multiple studies have indicated a central role of the endothelium in the initiation, progression, and clinical outcomes of cardiac disease. In this review we synthesize the current understanding of endothelial function and dysfunction as mediators of the cardiomyocyte phenotype in the setting of distinct cardiac pathologies; outline existing in vivo and in vitro models where key features of endothelial cell dysfunction can be recapitulated; and discuss future directions for development of endothelium-targeted therapeutics for cardiac diseases with limited existing treatment options.

Early Effects of Ticagrelor Versus Clopidogrel on Peripheral Endothelial Function After Non-ST-Elevation Acute Coronary Syndrome and Assessment of Its Relationship With Coronary Microvascular Function

Peripheral endothelial dysfunction is an independent predictor of adverse long-term prognosis after acute coronary syndrome. Data are lacking on the effects of oral P2Y12-inhibitors on peripheral endothelial function in non-ST-elevation acute coronary syndrome (NSTEACS). Furthermore, the relation between peripheral endothelial function and invasive indexes of coronary microvascular function in NSTEACS is unclear. Between March 2018 and July 2020, hospitalized patients with NSTEACS were randomized (1:1) to ticagrelor or clopidogrel. Peripheral endothelial function was assessed with brachial artery flow-mediated vasodilation (FMD). Invasive indexes of coronary microvascular function were obtained using an intracoronary pressure-temperature sensor-tipped wire. In 70 patients included, mean age was 58.6 years, 78.6% (n = 55) were male and 20% (n = 14) had diabetes mellitus. Compared with clopidogrel, ticagrelor significantly improved FMD (14.2 ± 5.4% vs 8.9 ± 5.3%, p <0.001) after a median treatment time of 41.2 hours. The FMD was significantly correlated with the index of microcirculatory resistance (IMR) measured in the infarct-related artery (r = -0.38, p = 0.001), with a stronger correlation found in those who did not have percutaneous coronary intervention (r = -0.52, p = 0.03). Using receiver operating characteristic curve analysis, an FMD of 8.2% identified an IMR of >34 as the threshold, with 77.6% sensitivity and 52.4% specificity. In patients who did not have a percutaneous coronary intervention, an FMD of 11.49% identified an IMR of >34 with 84.6% sensitivity and 80% specificity. In conclusion, ticagrelor significantly improved peripheral endothelial function compared with clopidogrel in patients with NSTEACS. There was a significant correlation between brachial artery FMD and IMR of the infarct-related artery.

The protective effect of remote ischemic conditioning is lost in patients with hypercholesterolemia

Remote ischemic conditioning (RIC), brief repetitive cycles of ischemia and reperfusion in remote tissues, is known to induce robust protection against myocardial ischemia-reperfusion (I/R) injury in preclinical studies. However, translation of the beneficial effects to the clinical setting has been challenging. A possibility is that comorbidities, including hypercholesterolemia, interfere with the protective mechanisms of RIC. The aim of this study was to test if hypercholesterolemia attenuates the efficacy of RIC in patients with hypercholesterolemia. Patients with familial hypercholesterolemia (FH) with high (≥5.5 mmol/L) low-density lipoprotein cholesterol (LDL-C), FH with low (≤2.5 mmol/L) and healthy control subjects (n = 12 in each group) were included. Flow-mediated vasodilatation (FMD) of the brachial artery was evaluated, before and after a 20-min period of forearm ischemia and 20 min reperfusion (I/R) as a measure of endothelial function. Study subjects were randomized to a RIC protocol consisting of four cycles of 5 min of leg ischemia or sham using a crossover design. Forearm I/R induced significant reduction in FMD in all three groups during the sham procedure. RIC protected from endothelial dysfunction induced by forearm ischemia-reperfusion in healthy controls [FMD baseline 2.8 ± 2.3 vs. FMD after I/R + RIC 4.5 ± 4.0%; means (SD)] and in patients with FH with low LDL-C (4.5 ± 3.5 vs. 4.4 ± 4.2%). By contrast, RIC fails to protect against I/R-induced endothelial dysfunction in patients with FH and high LDL-C (3.9 ± 3.0 vs. 1.1 ± 1.5%; P < 0.01). These findings provide the first evidence in humans that the protective effect of RIC is lost in patients with elevated cholesterol.NEW & NOTEWORTHY We investigated the impact of hypercholesterolemia on the protective effect of RIC on ischemia-reperfusion injury in a well-characterized patient population with isolated hypercholesterolemia. The results show that the protective effect of RIC is absent in patients with hypercholesterolemia but is apparent in patients with hypercholesterolemic following treatment with lipid-lowering drugs. The results are of importance for the understanding of how comorbidities affect the therapeutic potential of RIC.

TNF-α Predicts Endothelial Function and Number of CD34+ Cells after Stimulation with G-CSF in Patients with Advanced Heart Failure

Patients with advanced heart failure (HF) have reduced cardiac output and impaired peripheral blood flow, which diminishes endothelial shear stress and consequently flow-mediated dilatation (FMD). The aim of our study was to find out whether endothelial dysfunction is associated with the number of CD34+ cells and TNF-α levels in patients with ischemic and non-ischemic HF after stimulation with granulocyte colony-stimulating factor (G-CSF). We included 56 patients with advanced HF (LVEF < 35%). Eighteen patients (32.14%) had ischemic and 38 (67.86%) patients had non-ischemic HF. FMD of the brachial artery was performed before the patients underwent 5-day bone marrow stimulation with daily subcutaneous injections of G-CSF (5 μg/kg bid). On the fifth day peripheral blood CD34+ cell count was measured. No statistically significant differences were found between the patient groups in NT-proBNP levels ((1575 (425−2439) vs. 1273 (225−2239)) pg/mL; p = 0.40), peripheral blood CD34+ cell count ((67.54 ± 102.32 vs. 89.76 ± 71.21) × 106; p = 0.32), TNF-α ((8.72 ± 10.30 vs. 4.96 ± 6.16) ng/mL; p = 0.13) and FMD (6.7 ± 5.4 vs. 7.2 ± 5.9%; p = 0.76). In a linear regression model, only FMD (p = 0.001) and TNF-α (p = 0.003) emerged as statistically significant predictors of CD34+ cells counts. Our study suggests that TNF-α is a good predictor of impaired endothelial function and of CD34+ cells mobilization after G-CSF stimulation in patients with advanced HF of ischemic and non-ischemic origin.

Relation of endothelial and cardiac autonomic function with left ventricle diastolic function in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

Diabetes mellitus (DM) is a risk factor for left ventricle (LV) diastolic dysfunction. Aim of this study was to investigate whether endothelial and/or autonomic dysfunction are associated with LV diastolic dysfunction in DM patients.

METHODS

We studied 84 non-insulin-dependent type 2 DM (T2DM) patients with no heart disease by assessing: 1) LV diastolic function by echocardiography; 2) peripheral vasodilator function, by measuring flow-mediated dilation (FMD) and nitrate-mediate dilation (NMD); 3) heart rate variability (HRV) on 24-h Holter electrocardiographic monitoring.

RESULTS

Twenty-five patients (29.8%) had normal LV diastolic function, while 47 (55.9%) and 12 (14.3%) showed a mild and moderate/severe diastolic dysfunction, respectively. FMD in these 3 groups was 5.25 ± 2.0, 4.95 ± 1.6 and 4.43 ± 1.8% (p = 0.42), whereas NMD was 10.8 ± 2.3, 8.98 ± 3.0 and 8.82 ± 3.2%, respectively (p = 0.02). HRV variables did not differ among groups. However, the triangular index tended to be lower in patients with moderate/severe diastolic dysfunction (p = 0.09) and a significant correlation was found between the E/e' ratio and both the triangular index (r = -0.26; p = 0.022) and LF amplitude (r = -0.29; p = 0.011).

CONCLUSIONS

In T2DM patients an impairment of endothelium-independent, but not endothelium-dependent, dilatation seems associated with LV diastolic dysfunction. The possible role of cardiac autonomic dysfunction in diastolic dysfunction deserves investigation in larger populations of patients.

Brachial and carotid hemodynamic response to hot water immersion in men and women

This study sought to compare the brachial and carotid hemodynamic response to hot water immersion (HWI) between healthy young men and women. Ten women (W) and 11 men (M) (24 ± 4 yr) completed a 60-min HWI session immersed to the level of the sternum in 40°C water. Brachial and carotid artery hemodynamics (Doppler ultrasound) were measured at baseline (seated rest) and every 15 min throughout HWI. Within the brachial artery, total shear rate was elevated to a greater extent in women [+479 (+364, +594) s^-1] than in men [+292 (+222, +361) s^-1] during HWI (P = 0.005). As shear rate is inversely proportional to blood vessel diameter and directly proportional to blood flow velocity, the sex difference in brachial shear response to HWI was the result of a smaller brachial diameter among women at baseline (P < 0.0001) and throughout HWI (main effect of sex, P < 0.0001) and a greater increase in brachial velocity seen in women [+48 (+36, +61) cm/s] compared with men [+35 (+27, +43) cm/s] with HWI (P = 0.047) which allowed for a similar increase in brachial blood flow between sexes [M: +369 (+287, +451) mL/min, W: +364 (+243, +486) mL/min, P = 0.943]. In contrast, no differences were seen between sexes in carotid total shear rate, flow, velocity, or diameter at baseline or throughout HWI. These data indicate the presence of an artery-specific sex difference in the hemodynamic response to a single bout of HWI.

Assessment of vascular function in complete glycaemic spectrum

Purpose: The present study was conceived to delineate the point of vascular dysfunction along the glycemic spectrum (normoglycemic individuals with no family history of diabetes, normoglycemic individuals with family history of diabetes, prediabetic individuals, and diabetic individuals).Materials and Methods: In this cross-sectional comparative study, we enrolled 252 participants of both gender in the age group of 30-50 years. They were classified based on their family history of diabetes and glycemic status into four groups along the glycemic spectrum as mentioned above. We measured flow-mediated dilation (FMD) from brachial artery and vascular function biomarkers such as enthothelin-1 (ET-1), von Willbrand Factor (vWF), Vascular Endothelial Growth Factor (VEGF) to assess the vascular function. The comparison of data between groups were done using One Way ANOVA/Kruskal-Wallis followed by post-hoc analysis using LSD/Mann-Whitney U Test depending on the normality of the data. Spearman correlation was done between vascular function and plasma glucose levels to identify its relationship. Linear regression was carried out to identify the factors influencing the FMD across the glycemic spectrum.Results: We observed that vascular function negatively correlated with blood glucose levels. However, endothelin-1 and vWF derangement was there even in normoglycemic first degree relatives of diabetes (FDRD) and the derangement increased in prediabetes and diabetes. Physiological dysfunction in terms of decreased flow-mediated dilation starts from prediabetes only. VEGF derangement is found only in diabetic individuals.Conclusion: Vascular dysfunction is found even in normoglycemic FDRD and the derangement increased and compounded with the advancement of disease.

Endothelial dysfunction in patients with myocardial ischemia or infarction and nonobstructive coronary arteries

PURPOSE

The syndromes of myocardial infarction/myocardial ischemia with No Obstructive Coronary Artery Disease (MINOCA/INOCA) are seen more and more often. Endothelial dysfunction (ED) leading to ischemic events has been reported in many of these patients. We aimed to compare patients with MINOCA and INOCA regarding brachial artery flow-mediated endothelium-dependent vasodilation (flow-mediated dilation [FMD]) and plasma concentration of cardiotrophin-1 (CT-1).

METHODS

We included 42 patients with MINOCA and 38 patients with INOCA. Endothelial function was assessed by measuring FMD% and nitroglycerin-mediated dilatation (NMD%) in the brachial artery. The plasma level of CT-1 was determined by solid-phase enzyme-linked immunosorbent assay.

RESULTS

FMD% was significantly lower in MINOCA than in INOCA patients (6.45 ± 2.65 vs 8.94 ± 3.32, P < .001), without significant difference in NMD% (10.69 ± 3.19 vs 12.16 ± 3.69, P = .06). Plasma CT-1 levels were not significantly different: 40.1 pg/mL (22.5-102.1) vs 37.2 pg/mL (23.5-67.2), P = .53.

CONCLUSION

Our results suggest worse ED in MINOCA than in INOCA patients, but demonstrated no difference in CT-1 levels between patients with stable and unstable ischemic heart disease and normal coronary arteries.

Periodontal therapy and treatment of hypertension-alternative to the pharmacological approach. A systematic review and meta-analysis

AIM

Quantitative comparison of the effects of intensive (IPT) or conventional (CPT) periodontal treatment on arterial blood pressure, endothelial function and inflammatory/metabolic biomarkers.

MATERIALS AND METHODS

A systematic search was conducted to identify randomized controlled trials (RCT) of IPT (supra and subgingival instrumentation). Eight RCTs were included in the meta-analysis. Difference in change of systolic blood pressure (SBP) and diastolic blood pressure (DBP) before and after IPT or CPT were the primary outcomes. The secondary outcomes included: endothelial function and selected inflammatory/anti-inflammatory (CRP, IL-6, IL-10, IFN-γ) and metabolic biomarkers (HDL, LDL, TGs).

RESULTS

The overall effect estimates (pooled Weighted Mean Difference (WMD)) of the primary outcome for SBP and DBP was -4.3 mmHg [95%CI: -9.10-0.48], p = 0.08 and -3.16 mmHg [95%CI: -6.51-0.19], p = 0.06 respectively. These studies were characterized by high heterogeneity. Therefore, random effects model for meta-analysis was performed. Sub-group analyses confirmed statistically significant reduction in SBP [WMD = -11.41 mmHg (95%CI: -13.66, -9.15) P < 0.00001] and DBP [WMD = -8.43 mmHg (95%CI: -10.96,-5.91)P < 0.00001] after IPT vs CPT among prehypertensive/hypertensive patients, while this was not observed in normotensive individuals. The meta-analyses showed significant reductions in CRP and improvement of endothelial function following IPT at all analysed timepoints.

CONCLUSIONS

IPT leads to improvement of the cardiovascular health in hypertensive and prehypertensive individuals.

Sacubitril-valsartan improves conduit vessel function and functional capacity and reduces inflammation in heart failure with reduced ejection fraction

The Prospective comparison of ARNI with angiotensin-converting enzyme inhibitor to Determine Impact on Global Mortality and morbidity in Heart Failure trial identified a marked reduction in the risk of death and hospitalization for heart failure in patients with heart failure with reduced ejection fraction (HFrEF) treated with sacubitril-valsartan (trade name Entresto), but the physiological processes underpinning these improvements are unclear. We tested the hypothesis that treatment with sacubitril-valsartan improves peripheral vascular function, functional capacity, and inflammation in patients with HFrEF. We prospectively studied patients with HFrEF (n = 11, 10 M/1 F, left ventricular ejection fraction = 27 ± 8%) on optimal, guideline-directed medical treatment who were subsequently prescribed sacubitril-valsartan (open-label, uncontrolled, and unblinded). Peripheral vascular function [brachial artery flow-mediated dilation (FMD, conduit vessel function) and reactive hyperemia (RH, microvascular function)], functional capacity [six-minute walk test (6MWT) distance], and the proinflammatory biomarkers tumor necrosis factor-α (TNF-α) and interleukin-18 (IL-18) were obtained at baseline and at 1, 2, and 3 mo of treatment. %FMD improved after 1 mo of treatment, and this favorable response persisted for months 2 and 3 (baseline: 3.25 ± 1.75%; 1 mo: 5.23 ± 2.36%; 2 mo: 5.81 ± 1.79%; 3 mo: 6.35 ± 2.77%), whereas RH remained unchanged. 6MWT distance increased at months 2 and 3 (baseline: 420 ± 92 m; 1 mo: 436 ± 98 m; 2 mo: 465 ± 115 m; 3 mo: 460 ± 110 m), and there was a sustained reduction in TNF-α (baseline: 2.38 ± 1.35 pg/mL; 1 mo: 2.06 ± 1.52 pg/mL; 2 mo: 1.95 ± 1.34 pg/mL; 3 mo: 1.92 ± 1.37 pg/mL) and a reduction in IL-18 at month 3 (baseline: 654 ± 150 pg/mL; 1 mo: 595 ± 140 pg/mL; 2 mo: 601 ± 176 pg/mL; 3 mo: 571 ± 127 pg/mL). This study provides new evidence for the potential of this new drug class to improve conduit vessel function, functional capacity, and inflammation in patients with HFrEF.NEW & NOTEWORTHY We observed an approximately twofold improvement in conduit vessel function (brachial artery FMD), increased functional capacity (6MWT distance), and a reduction in inflammation (TNF-α and IL-18) following 3 mo of sacubitril-valsartan therapy. These findings provide important new information concerning the physiological mechanisms by which this new drug class provokes favorable changes in HFrEF pathophysiology.

Clinical significance of prolonged chest pain in vasospastic angina

BACKGROUND

Patients with vasospastic angina (VSA) sometimes experience prolonged chest symptoms. The clinical characteristics of these patients have not been clarified.

AIM

To investigate the clinical characteristics of prolonged VSA patients.

METHODS

This study included 167 patients with VSA diagnosed by spasm provocation tests (SPTs) using acetylcholine, which recorded the frequencies of positive reactions to a low dose of acetylcholine (L-ACh), total occlusion due to spasm (TOC), focal spasm, and the unavoidable use of nitroglycerin (unavoidable-NTG) during SPTs. The patients underwent a medical interview that investigated the maximum duration and frequency of chest symptoms as well as the frequencies of variant angina and other serious symptoms. The patients were divided into two groups based on the maximal duration: The short-duration group (< 15 min; n = 114) and the long-duration group (≥ 15 min; n = 53). They were also divided into two groups based on the frequency of chest symptoms: The low-frequency group (< 4/mo; n = 88) and the high-frequency group (≥ 4/mo; n = 79).

RESULTS

The long-duration group showed higher frequencies of other serious symptoms (P < 0.001) and variant angina (P < 0.05) as well as higher frequencies of spasm induction by L-ACh (P < 0.05), TOC (P < 0.05), focal spasm (P < 0.01), and unavoidable-NTG (P < 0.01) than the short-duration group. These parameters did not differ significantly between the low-frequency and high-frequency groups.

CONCLUSION

These findings suggest that patients with VSA who experience prolonged chest symptoms may have more severe characteristics of VSA.

Diagnostic Criteria of Flow-Mediated Vasodilation for Normal Endothelial Function and Nitroglycerin-Induced Vasodilation for Normal Vascular Smooth Muscle Function of the Brachial Artery

Background

Diagnostic criteria of flow‐mediated vasodilation (FMD), an index of endothelial function, and nitroglycerin‐induced vasodilation (NID), an index of vascular smooth muscle function, of the brachial artery have not been established. The purpose of this study was to propose diagnostic criteria of FMD and NID for normal endothelial function and normal vascular smooth muscle function.

Methods and Results

We investigated the cutoff values of FMD and NID in subjects with (risk group) and those without cardiovascular risk factors or cardiovascular diseases (no‐risk group) in 7277 Japanese subjects (mean age 51.4±10.8 years) from the Flow‐Mediated Dilation Japan study and the Flow‐Mediated Dilatation Japan Registry study for analysis of the cutoff value of FMD and in 1764 Japanese subjects (62.2±16.1 years) from the registry of Hiroshima University Hospital for analysis of the cutoff value of NID. Receiver‐operator characteristic curve analysis of FMD to discriminate subjects in the no‐risk group from patients in the risk group showed that the optimal cutoff value of FMD to diagnose subjects in the no‐risk group was 7.1%. Receiver‐operator characteristic curve analysis of NID to discriminate subjects in the no‐risk group from patients in the risk group showed that the optimal cutoff value of NID to diagnose subjects in the no‐risk group was 15.6%.

Conclusions

We propose that the cutoff value for normal endothelial function assessed by FMD of the brachial artery is 7.1% and that the cutoff value for normal vascular smooth muscle function assessed by NID of the brachial artery is 15.6% in Japanese subjects.

Clinical Trial Registration

http://www.umin.ac.jp Unique identifiers: UMIN000012950, UMIN000012951, UMIN000012952, and UMIN000003409

Heat therapy reduces sympathetic activity and improves cardiovascular risk profile in women who are obese with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) affects up to 15% of women and is associated with increased risk of obesity and cardiovascular disease. Repeated passive heat exposure [termed "heat therapy" (HT)] is a lifestyle intervention with the potential to reduce cardiovascular risk in obesity and PCOS. Women with obesity (n = 18) with PCOS [age 27 ± 4 yr, body mass index (BMI) 41.3 ± 4.7 kg/m²] were matched for age and BMI, then assigned to HT (n = 9) or time control (CON; n = 9). HT subjects underwent 30 one-hour hot tub sessions over 8-10 wk, whereas CON subjects did not undergo HT. Muscle sympathetic nerve activity (MSNA), blood pressure, cholesterol, C-reactive protein, and markers of vascular function were assessed at the start (Pre) and end (Post) of 8-10 wk. These measures included carotid and femoral artery wall thickness and flow-mediated dilation (FMD), measured both before and after 20 min of ischemia-20 min of reperfusion (I/R) stress. HT subjects exhibited reduced MSNA burst frequency (Pre: 20 ± 8 bursts/min, Post: 13 ± 5 bursts/min, P = 0.012), systolic (Pre: 124 ± 5 mmHg, Post: 114 ± 6 mmHg; P < 0.001) and diastolic blood pressure (Pre: 77 ± 6 mmHg, Post: 68 ± 3 mmHg; P < 0.001), C-reactive protein (Pre: 19.4 ± 13.7 nmol/L, Post: 15.2 ± 12.3 nmol/L; P = 0.018), total cholesterol (Pre: 5.4 ± 1.1 mmol/L, Post: 5.0 ± 0.8 mmol/L; P = 0.028), carotid wall thickness (Pre: 0.054 ± 0.005 cm, Post: 0.044 ± 0.005 cm; P = 0.010), and femoral wall thickness (Pre: 0.056 ± 0.009 cm, Post: 0.042 ± 0.005 cm; P = 0.003). FMD significantly improved in HT subjects over time following I/R (Pre: 5.6 ± 2.5%, Post: 9.5 ± 1.7%; P < 0.001). No parameters changed over time in CON, and BMI did not change in either group. These findings indicate that HT reduces sympathetic nerve activity, provides protection from I/R stress, and substantially improves cardiovascular risk profiles in women who are obese with PCOS.

Bilirubin and Endothelial Function

Bilirubin is a fundamental metabolic end product of heme degradation. Despite acting as a cytotoxic metabolite at high concentrations, bilirubin at physiological concentrations has antioxidant effects, such as scavenging reactive oxygen species, leading to a decrease in oxidative stress. Endothelial dysfunction is an early feature of and plays an important role in the development and progression of atherosclerosis, leading to cardiovascular complications. One mechanism of endothelial dysfunction is an increase in oxidative stress, by which the bioavailability of nitric oxide is decreased. Therefore, bilirubin is expected to improve endothelial function, to inhibit the progression of atherosclerosis, and to reduce cardiovascular complications by inactivating oxidative stress through its antioxidant effects. In this review, we will focus on the clinical associations of the antioxidant bilirubin with endothelial function and cardiovascular complications.

Coronary Microvascular Dysfunction by Myocardial Contrast Echocardiography in Nonelderly Patients Referred for Computed Tomographic Coronary Angiography

BACKGROUND

Microvascular dysfunction (MVD) is a potential cause of chest pain in younger individuals. The authors hypothesized that nonelderly patients referred for computed tomographic angiography (CTA) but without significant stenosis would have a high prevalence of MVD by myocardial contrast echocardiography (MCE). Secondary aims were to test whether the presence of nonobstructive coronary artery disease (CAD) or reduced brachial flow-mediated dilation (FMD) predicted MVD.

METHODS

Subjects ≤60 years of age undergoing CTA were recruited if they had either no evidence of coronary plaque or evidence of mild CAD (<50% stenosis) and at least one high-risk plaque feature. Subjects underwent quantitative perfusion imaging using MCE at rest and during regadenoson vasodilator stress. MVD was defined as global or segmental delay of microvascular refill (≥2 sec) during regadenoson. FMD of the brachial artery was also performed.

RESULTS

Of the 29 patients in whom MCE could be performed, 12 (41%) had MVD. These subjects, compared with those with normal microvascular function, had lower hyperemic perfusion (mean, 236 ± 68 vs 354 ± 161 intensity units/sec; P = .02) and microvascular flux rate (mean, 1.6 ± 0.4 vs 2.5 ± 0.9 sec-1; P = .002) on quantitative MCE. The degree of FMD was not significantly different in those with or without MVD (mean, 11 ± 4% vs 9 ± 4%; P = .32), and there was a poor correlation between results on stress MCE and FMD. Only eight of the 29 subjects were classified as having nonobstructive CAD. There were no groupwise differences in the prevalence of MVD function in those with versus without CAD (43% vs 38% for negative and positive findings on CTA, respectively, P = .79).

CONCLUSIONS

MVD is a common finding in the nonelderly population referred for CTA for evaluation of possible CAD but without obstructive stenosis. Neither the presence of noncritical atherosclerotic disease nor abnormal FMD increases the likelihood for detecting MVD in this population.

Strong Relationship Between Vascular Function in the Coronary and Brachial Arteries

Early detection of coronary artery dysfunction is of paramount cardiovascular clinical importance, but a noninvasive assessment is lacking. Indeed, the brachial artery flow-mediated dilation test only weakly correlated with acetylcholine-induced coronary artery function ( r=0.36). However, brachial artery flow-mediated dilation methodologies have, over time, substantially improved. This study sought to determine if updates to this technique have improved the relationship with coronary artery function and the noninvasive indication of coronary artery dysfunction. Coronary artery and brachial artery function were assessed in 28 patients referred for cardiac catheterization (61±11 years). Coronary artery function was determined by the change in artery diameter with a 1.82 μg/min intracoronary acetylcholine infusion. Based on the change in vessel diameter, patients were characterized as having dysfunctional coronary arteries (>5% vasoconstriction) or relatively functional coronary arteries (<5% vasoconstriction). Brachial artery function was determined by flow-mediated dilation, adhering to current guidelines. The acetylcholine-induced change in vessel diameter was smaller in patients with dysfunctional compared with relatively functional coronary arteries (-11.8±4.6% versus 5.8±9.8%, P<0.001). Consistent with this, brachial artery flow-mediated dilation was attenuated in patients with dysfunctional compared with relatively functional coronaries (2.9±1.9% versus 6.2±4.2%, P=0.007). Brachial artery flow-mediated dilation was strongly correlated with the acetylcholine-induced change in coronary artery diameter ( r=0.77, P<0.0001) and was a strong indicator of coronary artery dysfunction (receiver operator characteristic=78%). The current data support that updates to the brachial artery flow-mediated dilation technique have strengthened the relationship with coronary artery function, which may now provide a clinically meaningful indication of coronary artery dysfunction.

Peripheral Microvascular Function Reflects Coronary Vascular Function

Objectives- Coronary endothelial dysfunction is a precursor of atherosclerosis and adverse outcomes. Whether endothelial dysfunction is a localized or generalized phenomenon in humans remains uncertain. We simultaneously measured femoral and coronary vascular function with the hypothesis that peripheral vascular endothelial function will be reflective of coronary endothelial function. Approach and Results- Eighty-five subjects underwent coronary angiography for evaluation of chest pain or abnormal stress tests. Endothelium-dependent and -independent vascular function were measured using intracoronary and intrafemoral infusions of acetylcholine and sodium nitroprusside, respectively. Coronary flow reserve was assessed using intracoronary adenosine infusion. Flow velocity was measured in each circulation using a Doppler wire (FloWire, EndoSonics). Coronary vascular resistance and femoral vascular resistance were calculated as mean arterial pressure (mm Hg)/coronary blood flow (mL/min) and mean arterial pressure (mm Hg)/femoral average peak velocity (cm/s), respectively. Mean age was 53±11 years, 37% were female, 44% had hypertension, 12% had diabetes mellitus, and 38% had obstructive coronary artery disease. There was a correlation between the change in femoral vascular resistance with acetylcholine and acetylcholine-mediated changes in both the coronary vascular resistance ( r=0.27; P=0.014) and in the epicardial coronary artery diameter ( r=-0.25; P=0.021), indicating that subjects with normal endothelial function in the femoral circulation had normal endothelial function in the coronary epicardial and microcirculation and vice versa. The coronary vasodilator response to adenosine also correlated with the femoral vasodilatation with acetylcholine ( r=0.4; P=0.0002). There was no correlation between the coronary and femoral responses to sodium nitroprusside. Conclusions- Endothelial functional changes in the peripheral and coronary circulations were modestly correlated. Thus, peripheral microvascular endothelial function reflects endothelium-dependent coronary epicardial and microvascular function and the coronary flow reserve. Visual Overview- An online visual overview is available for this article.

Lipoprotein Apheresis Acutely Reverses Coronary Microvascular Dysfunction in Patients With Severe Hypercholesterolemia

OBJECTIVES

This study evaluated whether lipoprotein apheresis produces immediate changes in resting perfusion in subjects with severe hypercholesterolemia, and whether there is a difference in the response between peripheral and coronary microcirculations.

BACKGROUND

Lipoprotein apheresis is used in patients with severe hypercholesterolemia to reduce plasma levels of low-density lipoprotein cholesterol.

METHODS

Quantitative contrast-enhanced ultrasound perfusion imaging of the myocardium at rest and skeletal muscle at rest and during calibrated contractile exercise was performed before and immediately after lipoprotein apheresis in 8 subjects with severe hypercholesterolemia, 7 of whom had a diagnosis of familial hypercholesterolemia. Myocardial perfusion imaging was also performed in 14 normal control subjects. Changes in myocardial work and left ventricular function were assessed by echocardiography. Ex vivo ovine coronary and femoral artery ring tension assays were assessed in the presence of pre- and post-apheresis plasma.

RESULTS

Apheresis acutely decreased low-density lipoprotein cholesterol (234.9 ± 103.2 mg/dl vs. 67.1 ± 49.5 mg/dl; p < 0.01) and oxidized phospholipid on apolipoprotein B-100 (60.2 ± 55.2 nmol/l vs. 47.0 ± 24.5 nmol/l; p = 0.01), and acutely increased resting myocardial perfusion (55.1 [95% confidence interval: 77.2 to 73.1] IU/s vs. 135 [95% confidence interval: 81.2 to 189.6] IU/s; p = 0.01), without changes in myocardial work. Myocardial longitudinal strain improved in those subjects with reduced pre-apheresis function. Skeletal muscle perfusion at rest and during contractile exercise was unchanged by apheresis. Acetylcholine-mediated dilation of ex vivo ovine coronary but not femoral arteries was impaired in pre-apheresis plasma and was completely reversed in post-apheresis plasma.

CONCLUSIONS

Lipoprotein apheresis produces an immediate improvement in coronary microvascular function, which increases myocardial perfusion and normalizes endothelial-dependent vasodilation. These changes are not observed in the periphery. (Acute Microvascular Changes With LDL Apheresis; NCT02388633).

Correlation of endothelial dysfunction measured by flow-mediated vasodilatation to severity of coronary artery disease

OBJECTIVES

Brachial artery ultrasound imaging during reactive hyperemia is widely used tool for quantifying endothelium dependent vasomotion. Angiodefender device is used for non invasive determination of percentage flow mediated vasodilation (FMD). An attempt is made to study whether endothelial dysfunction determined by FMD of brachial artery predicts the presence or absence of coronary artery disease and its correlation with the severity of coronary artery disease.

METHODS

One hundred six patients admitted between May 2014 and April 2015 who were posted for coronary angiography diagnosed to have chronic stable angina on clinical basis and/or by exercise stress test, for evaluation of coronary artery disease were submitted to standard clinical evaluation, calculation of percentage FMD by Angiodefender device. Statistical significance of difference of categorical variables was tested using Fisher's exact test. Sensitivity, specificity, positive predictive value and negative predictive value of FMD were studied.

RESULTS

There was no correlation between number of risk factors and percentage of FMD. Significantly higher proportion of cases with less FMD had higher prevalence of coronary artery disease and vice-versa. Significantly higher proportion of cases with positive stress test had less percentage of FMD and vice-versa. Significantly higher proportion of cases with less percentage of FMD and positive stress test had higher prevalence of obstructive coronary artery disease and vice-versa. Specificity was 100% when percentage of FMD was ≤10.

CONCLUSIONS

FMD an inexpensive and non-invasive test provides information regarding extent and severity of coronary artery disease.

Exercise-induced heat stress disrupts the shear-dilatory relationship

NEW FINDINGS

What is the central question of this study? Although heat stress is known to increase cardiovascular strain, no study, to date, had explored the potential impact of exercise-induced heat stress on vascular function. What is the main finding and its importance? We found that acute exercise tended to reduce flow-mediated dilatation (FMD), owing in part to reduced reactive hyperaemia/shear stimulus; thus, when FMD is normalized to shear no postexercise deficit exists. Exercise-induced heat stress increased reactive hyperaemia, shear rate, coupled with a sustained FMD postexercise, suggests that exercise-induced heat stress increases the amount of shear stimulus to elicit a similar response, indicating reduced vascular responsiveness, or reserve, which might increase cardiovascular susceptibility. Heat stress increases cardiovascular strain and is of particular concern in occupations, such as firefighting, in which individuals are required to perform strenuous work while wearing personal protective equipment. Sudden cardiac events are associated with strenuous activity and are the leading cause of duty-related death among firefighters, accounting for ∼50% of duty-related fatalities per year. Understanding the acute effects of exercise-induced heat stress (EIHS) on vascular endothelial function may provide insight into the mechanisms precipitating acute coronary events in firefighters. The purpose of this study, therefore, was to determine the effects of EIHS on vascular endothelial function. Using a balanced crossover design, 12 healthy men performed 100 min of moderate-intensity, intermittent exercise with and without EIHS (personal protective equipment or cooling vest, respectively). Measurements of flow-mediated dilatation (FMD), reactive hyperaemia and shear rate area under the curve (SR_AUC ) were performed pre- and postexercise. During EIHS, core temperature was significantly higher (38 ± 0.1 versus 37 ± 0.1°C). Postexercise FMD tended to be suppressed in both conditions, but was not different from pre-exercise. Reactive hyperaemia was reduced after no-EIHS but increased after EIHS. Thus, normalizing FMD to the shear stimulus (FMD/SR_AUC ) revealed a significant reduction in FMD after EIHS only (pre-exercise 0.15 ± 0.04 and 0.13 ± 0.02 s^-1 versus postexercise, 0.13 ± 0.02 and 0.06 ± 0.02 s^-1 , no-EIHS and EIHS, respectively). We conclude that moderate heat stress superimposed on moderate-intensity exercise resulted in reduced vascular endothelial function. This heat stress-induced alteration in the shear-dilatory relationship may relate to the increased risk of acute coronary events associated with activities that combine physical exertion and heat stress (i.e. firefighting).

Enhancement of arterial pulsation during flow-mediated dilation is impaired in the presence of ischemic heart disease

Purpose

The aim of this study is to investigate the relationship between arterial pulse amplitude change under increased shear stress and the presence of ischemic heart disease (IHD).

Methods

This study comprised 31 subjects, including 14 subjects with IHD. We investigated the change in brachial artery pulse amplitude during flow-mediated dilation (FMD) using ultrasonography.

Results

The arterial pulse amplitude increased during FMD in 19 subjects, whereas it decreased in 12 subjects. There was a marked difference in the change in arterial pulse amplitude (the maximum amplitude of the arterial pulse amplitude during FMD/the arterial pulse amplitude at baseline) between subjects with and without IHD (0.98 ± 0.53 and 1.37 ± 0.53, p = 0.028). Furthermore, decreased arterial pulse amplitude during FMD was a significant predictor of IHD after adjustment of age, blood pressure, the presence of each type of coronary risks, the value of FMD and sex (p = 0.0001).

Conclusions

The decrease of arterial pulsation amplitude during FMD was a useful predictive parameter for IHD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2794-0) contains supplementary material, which is available to authorized users.

Effect of CPAP Withdrawal on myocardial perfusion in OSA: A randomized controlled trial

BACKGROUND AND OBJECTIVE

Obstructive sleep apnoea (OSA) is highly prevalent and associated with an increased incidence of cardiovascular events. Endothelial dysfunction is the proposed causative mechanism. Continuous positive airway pressure (CPAP) is presumed to improve cardiovascular outcome in OSA. CPAP withdrawal was recently shown to lead to peripheral endothelial dysfunction. However, it is not known whether short-term CPAP withdrawal reduces myocardial perfusion in OSA.

METHODS

In this double-blind randomized controlled study, 45 patients with moderate to severe OSA previously adherent to CPAP were assigned to either subtherapeutic or continuing therapeutic CPAP for 2 weeks. The primary outcome was adenosine-induced myocardial blood flow (MBF) as a measure of endothelial function, assessed by (13) N-ammonia positron emission tomography. Secondary outcomes were measures of dermal and renal microvascular function, morning blood pressure (BP) and heart rate.

RESULTS

Despite return of OSA associated with significant increases in BP (+9.1 mm Hg, 95% CI +4.9 to +13.4 mm Hg, P < 0.001) and heart rate (+9.6 bpm, 95% confidence interval (CI) +4.6 to +14.6 bpm, P < 0.001), CPAP withdrawal had no significant effect on maximal myocardial perfusion capacity (hyperaemic MBF -0.01 ml/min/g, 95% CI -0.33 to +0.24 ml/min/g, P = 0.91), nor renal and dermal microvascular function.

CONCLUSION

In patients with OSA, a short-term CPAP withdrawal does not lead to detectable impairment of coronary endothelial function, as has been demonstrated in the brachial artery, despite a clinically relevant increase in BP of nearly 10 mm Hg. There was also no evidence of an impairment of renal or dermal microvascular function.

Effect of CPAP therapy on endothelial function in obstructive sleep apnoea: A systematic review and meta-analysis

Obstructive sleep apnoea (OSA) is a prevalent sleep-related breathing disorder associated with adverse cardiovascular outcome. Endothelial dysfunction is one of the proposed mechanistic links between OSA and the increased cardiovascular risk. Treatment with continuous positive airway pressure (CPAP) may reverse this detrimental pathophysiological consequence of OSA. Most studies on the effect of CPAP on endothelial function in OSA are limited by their low sample size. The objective of this systematic review was to assess the effect CPAP therapy on endothelial function in patients with OSA. We conducted a systematic review and meta-analysis searching literature databases up to August 2013 for randomized controlled trials (RCTs) on the effect of CPAP on endothelial function in OSA, assessed by flow-mediated dilatation (FMD) and other validated techniques. The primary outcome for the meta-analysis (DerSimonian/Laird random-effects method) was the treatment effect on FMD. Eight RCTs comparing the effects of therapeutic CPAP versus subtherapeutic CPAP (or no intervention) on endothelial function involving 245 OSA patients were included in the systematic review. The studies are consistent in effect direction, showing an improvement of endothelial function by CPAP. Four RCTs involving 150 patients could be used for the meta-analysis. Compared to the control group, CPAP therapy (range 2-24 weeks) significantly increased absolute % FMD by 3.87% (95% confidence interval: 1.93-5.80, P < 0.001). In patients with OSA, CPAP therapy improves endothelial function significantly and to a clinically important extent.

Impaired coronary and retinal vasomotor function to hyperoxia in Individuals with Type 2 diabetes

PURPOSE

Adults with diabetes are at a high risk of developing coronary heart disease. The purpose of this study was to assess coronary artery vascular function non-invasively in individuals with and without Type 2 diabetes and to compare these coronary responses to another microvascular bed (i.e. retina). We hypothesized that individuals with diabetes would have impaired coronary reactivity and that these impairments would be associated with impairments in retinal reactivity.

METHODS

Coronary blood velocity (Transthoracic Doppler Echocardiography) and retinal diameters (Dynamic Vessel Analyzer) were measured continuously during five minutes of breathing 100% oxygen (i.e. hyperoxia) in 15 persons with Type 2 diabetes and 15 age-matched control subjects. Using fundus photographs, retinal vascular calibers were also measured (central retinal arteriole and venule equivalents).

RESULTS

Individuals with diabetes compared to controls had impaired coronary (-2.34±16.64% vs. -14.27±10.58%, P=0.03) and retinal (arteriole: -0.04±3.34% vs. -3.65±5.07%, P=0.03; venule: -1.65±3.68% vs. -5.23±5.47%, P=0.05) vasoconstrictor responses to hyperoxia, and smaller central arteriole-venule equivalent ratios (0.83±0.07 vs. 0.90±0.07, P=0.014). Coronary reactivity was associated with central retinal arteriole equivalents (r=-0.516, P=0.005) and retinal venular reactivity (r=0.387, P=0.034).

CONCLUSION

Diabetes impairs coronary and retinal microvascular function to hyperoxia. Impaired vasoconstrictor responses may be part of a systemic diabetic vasculopathy, which may contribute to adverse cardiovascular events in individuals with diabetes.

Vegan diet, subnormal vitamin B-12 status and cardiovascular health

Vegetarian diets have been associated with atherosclerosis protection, with healthier atherosclerosis risk profiles, as well as lower prevalence of, and mortality from, ischemic heart disease and stroke. However, there are few data concerning the possible cardiovascular effects of a vegan diet (with no meat, dairy or egg products). Vitamin B-12 deficiency is highly prevalent in vegetarians; this can be partially alleviated by taking dairy/egg products in lact-ovo-vegetarians. However, metabolic vitamin B-12 deficiency is highly prevalent in vegetarians in Australia, Germany, Italy and Austria, and in vegans (80%) in Hong Kong and India, where vegans rarely take vitamin B-12 fortified food or vitamin B-12 supplements. Similar deficiencies exist in northern Chinese rural communities consuming inadequate meat, egg or dairy products due to poverty or dietary habits. Vascular studies have demonstrated impaired arterial endothelial function and increased carotid intima-media thickness as atherosclerosis surrogates in such metabolic vitamin B-12 deficient populations, but not in lactovegetarians in China. Vitamin B-12 supplementation has a favourable impact on these vascular surrogates in Hong Kong vegans and in underprivileged communities in northern rural China. Regular monitoring of vitamin B-12 status is thus potentially beneficial for early detection and treatment of metabolic vitamin B-12 deficiency in vegans, and possibly for prevention of atherosclerosis-related diseases.

Close relationship between serum hyaluronan levels and vascular function in patients with type 2 diabetes

OBJECTIVE

To clarify the relationship between serum hyaluronan levels and vascular function in type 2 diabetic patients.

METHODS

A cross-sectional cohort study.

RESULTS

In multivariate regression analysis, endothelium-dependent flow-mediated dilation was associated with age and duration of diabetes, but not with serum hyaluronan level, while endothelium-independent nitroglycerine-mediated dilation (NMD) was only associated with serum hyaluronan level (standardized estimate = -0.401, p = 0.003). NMD in the lowest tertile of hyaluronan level was significantly higher than the other tertiles (15.9% versus 12.5% and 10.4%, p = 0.047 and p = 0.002, respectively).

CONCLUSIONS

Serum hyaluronan level may be useful as a surrogate marker for early changes in the vascular function, which often occurs in patients with diabetes mellitus.

Ischemic postconditioning does not improve peripheral endothelial function in ST-segment elevation myocardial infarction patients

The purpose of this study was to determine whether ischemic postconditioning (IPC) could improve peripheral endothelial function in patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). Of 102 patients randomly assigned to an IPC or standard protocol to study infarct size utilizing cardiovascular magnetic resonance imaging, 84 patients had peripheral endothelial function assessed with brachial ultrasound measures and peripheral arterial tonometry (PAT) during reactive hyperemia 3 days after PCI. Overall IPC was not associated with a smaller infarct size compared to controls, though there was a trend towards greater myocardial salvage with IPC. Patients randomized to IPC (n=43; age 56 ± 11 years; 85% male) and standard protocol (n=41; age 56 ± 10 years; 88% male) underwent endothelial function assessment. Flow mediated vasodilatation was not significantly greater in the IPC group than in the standard group (7.4 ± 4.9% versus 6.6 ± 4.0% respectively, p=0.40) nor was peak hyperemic velocity-time integral (78 ± 26 cm versus 71 ± 30 cm respectively, p=0.28). Similarly, the PAT hyperemic ratio was not significantly greater in the IPC group than in the standard group (2.0 ± 0.9 versus 1.8 ± 0.6 respectively, p=0.14). In conclusion, IPC did not improve early peripheral endothelial function in patients with STEMI undergoing primary PCI.

Endothelial function increases after a 16-week diet and exercise intervention in overweight and obese young women

Weight loss improves endothelial function in overweight individuals. The effects of weight loss through combined aerobic and resistance training and caloric restriction on in vivo vascular measures and blood markers associated with the regulation of endothelial function have not been comprehensively examined. Therefore, we investigated brachial artery endothelial function and potential regulatory blood markers in twenty overweight women (30.3 ± 2.0 years) who participated in 16 weeks of aerobic (5 d/wk) and resistance training (2 d/wk) (combined: ≥250 kcal/d) and caloric restriction (−500 kcal/d versus requirement). Resting brachial artery flow mediated dilation (FMD) and circulating endothelin-1 (ET-1) and interleukin-6 (IL-6) were assessed at baseline and following the intervention. Relative and absolute FMD increased (before: 4.0 ± 0.5% versus after: 6.9 ± 0.6%, P < 0.05, and before: 0.14 ± 0.02 mm versus after: 0.23 ± 0.02 mm, P < 0.05, resp.), while body mass decreased (before: 86.9 ± 2.4 kg versus after: 81.1 ± 2.4 kg, P < 0.05) following the intervention. There were no changes in either blood marker (IL-6: before: 1.5 ± 0.2 pg/mL versus after: 1.5 ± 0.1 pg/mL, P > 0.05, and ET-1: before: 0.55 ± 0.05 pg/mL versus after: 0.59 ± 0.09 pg/mL, P > 0.05). 16 weeks of combined aerobic/resistance training and diet-induced weight loss improved endothelial function in overweight and obese young women, but this increase was not associated with changes in blood markers of vasoconstriction or inflammation.

Brachial artery constriction during brachial artery reactivity testing predicts major adverse clinical outcomes in women with suspected myocardial ischemia: results from the NHLBI-sponsored women's ischemia Syndrome Evaluation (WISE) Study

BACKGROUND

Limited brachial artery (BA) flow-mediated dilation during brachial artery reactivity testing (BART) has been linked to increased cardiovascular risk. We report on the phenomenon of BA constriction (BAC) following hyperemia.

OBJECTIVES

To determine whether BAC predicts adverse CV outcomes and/or mortality in the women's ischemic Syndrome Evaluation Study (WISE). Further, as a secondary objective we sought to determine the risk factors associated with BAC.

METHODS

We performed BART on 377 women with chest pain referred for coronary angiography and followed for a median of 9.5 years. Forearm ischemia was induced with 4 minutes occlusion by a cuff placed distal to the BA and inflated to 40mm Hg > systolic pressure. BAC was defined as >4.8% artery constriction following release of the cuff. The main outcome was major adverse events (MACE) including all-cause mortality, non-fatal MI, non-fatal stroke, or hospitalization for heart failure.

RESULTS

BA diameter change ranged from -20.6% to +44.9%, and 41 (11%) women experienced BAC. Obstructive CAD and traditional CAD risk factors were not predictive of BAC. Overall, 39% of women with BAC experienced MACE vs. 22% without BAC (p=0.004). In multivariate Cox proportional hazards regression, BAC was a significant independent predictor of MACE (p=0.018) when adjusting for obstructive CAD and traditional risk factors.

CONCLUSIONS

BAC predicts almost double the risk for major adverse events compared to patients without BAC. This risk was not accounted for by CAD or traditional risk factors. The novel risk marker of BAC requires further investigation in women.

Diabetic retinopathy and endothelial dysfunction in patients with type 2 diabetes mellitus

BACKGROUND

We investigated the relationship between endothelial dysfunction and diabetic retinopathy (DR) in patients with type 2 diabetes.

METHODS

We used a cross-sectional design to examine 167 patients with type 2 diabetes mellitus. All patients underwent biochemical and ophthalmological examination. We assessed endothelial dysfunction by a flow-mediated vasodilation method of the brachial artery. Changes in vasodilation (flow-mediated vasodilatation, %FMD) were expressed as percent change over baseline values.

RESULTS

The mean±standard deviation of patient age was 54.1±8.6 years. The %FMD was significantly lower in patients with DR than without DR. The prevalence of retinopathy decreased across increasing tertiles of %FMD. After adjusting for patients' age, sex, diabetes duration, use of insulin, use of antihypertensive, antiplatelet, and lipid lowering medications, systolic blood pressure, fasting plasma glucose, 2-hour plasma glucose, glycated hemoglobin, and urinary albumin excretion, participants with a reduced %FMD were more likely to have DR (odds ratio, 11.819; 95% confidence interval, 2.201 to 63.461; P=0.004, comparing the lowest and highest tertiles of %FMD).

CONCLUSION

Endothelial dysfunction was associated with DR, which was most apparent when the endothelial dysfunction was severe. Our study provides insights into the possible mechanism of the influence of endothelial dysfunction on the development of DR.

Cardiovascular Protective Effects of Adjunctive Alternative Medicine (Salvia miltiorrhiza and Pueraria lobata) in High-Risk Hypertension

Introduction. Hypertension in association with diabetes (DM), renal impairment (RI), and left ventricular hypertrophy (LVH) increases the risk of future cardiovascular events. We hypothesize, traditional herbal medicines Danshen and Gegen (D&G) have beneficial effects on atherogenesis in these high-risk hypertensive subjects. Subjects and Methods. 90 asymptomatic hypertensive subjects associated with LVH (63.3%), DM (62.2%), or RI (30%) were randomized to receive D&G herbal capsules 1 gm/day, 2 gm/day, or identical placebo capsules in double-blind and parallel fashion for 12 months. Brachial flow-mediated dilation (endothelium-dependent dilation, FMD) and carotid intima-media thickness (IMT) were measured by ultrasound. All data were analyzed using the Statistical Package for Social Sciences in Windows 16.0. Results. Their mean age was 55 ± 8 years, and 74.4% were male. After 12 months of adjunctive therapies and compared with baseline, there were no significant changes in blood pressure, heart rate, hematological, glucose, and creatinine profiles in both placebo and D&G groups. FMD improved significantly during D&G (P = 0.0001) and less so after placebo treatment (P = 0.001). There was a mild but significant decrease in carotid IMT after D&G (P < 0.001) but no significant changes after placebo. A trend of better improvement in FMD after higher versus lower D&G dosages was seen. D&G were well tolerated, with no significant adverse events or blood biochemistry changes. Conclusion. D&G adjunctive treatment was well tolerated and significantly improved atherogenesis in high-risk hypertensive patients, with potential in primary atherosclerosis prevention.

Evaluation of coronary microvascular function in patients with vasospastic angina

AIM: To investigate endothelium-dependent and -independent coronary microvascular functions in patients with vasospastic angina (VSA).

METHODS: Thirty-six patients with VSA (30 men and 6 women; mean age, 58 years) were enrolled in this study. VSA was defined as ≥ 90% narrowing of the epicardial coronary arteries on angiography performed during a spasm provocation test, presence of chest pain, and/or ST-segment deviation on an electrocardiogram (ECG). Patients (n = 36) with negative spasm provocation test results and those matched for age and sex were enrolled as a control group (nonVSA group). Low-dose acetylcholine (ACh; 3 μg/min) was infused into the left coronary ostium for 2 min during the spasm provocation test. Following the spasm provocation test, nitroglycerin (0.2 mg) was administered intracoronally. Coronary blood flow (was calculated from quantitative angiography and Doppler flow velocity measurements, and the coronary flow reserve was calculated as the ratio of coronary flow velocity after injection of adenosine triphosphate (20 μg) to the baseline value. Changes in the coronary artery diameter in response to ACh and nitroglycerin infusion were expressed as percentage changes from baseline measurements.

RESULTS: Body mass index was significantly lower in the VSA group than in the nonVSA group. The frequency of conventional coronary risk factors and the rate of statin use were similar between the 2 groups. The left ventricular ejection fraction as evaluated by echocardiography was similar between the 2 groups. The duration of angina was 9 ± 2 mo. The results of blood chemistry analysis were similar between the 2 groups. Low-dose ACh did not cause coronary spasms. The change in coronary artery diameter in response to ACh was lower in the VSA group (-1.4% ± 9.3%) than in the nonVSA group (3.1% ± 6.5%, P < 0.05), whereas nitroglycerin-induced coronary artery dilatation and coronary blood flow increase in response to ACh or coronary flow reserve did not differ significantly between the 2 groups.

CONCLUSION: These findings suggest that microvascular coronary function may be preserved despite endothelial dysfunction of the epicardial coronary arteries in patients with VSA.

Association between diabetic retinopathy and flow-mediated vasodilation in type 2 DM

OBJECTIVE

Retinal endothelial dysfunction is a key in the etiogenesis of diabetic retinopathy (DR), in patients with type 2 diabetes mellitus (DM). Brachial artery flow-mediated vasodilation (FMD) is a marker of endothelial function associated with production of endogenous nitric oxide. Using FMD, we investigated the relationship between macrovascular function and DR.

METHODS

We studied 74 patients with type 2 DM, including non-DR (NDR) (n = 30); mild nonproliferative DR (NPDR) (n = 16); moderate NPDR (n = 10); severe NPDR (n = 10); and proliferative DR (PDR) (n = 8); and 21 age-matched controls. We measured FMD in each group. Retinal blood flow and pulsatility ratios were measured using laser Doppler velocimetry.

RESULTS

FMD decreased significantly in patients with DM compared with healthy control subjects. No significant differences were found in FMD among the NDR, mild NPDR, and moderate NPDR groups. FMD decreased significantly in the severe NPDR and PDR groups compared with the NDR group. FMD was significantly and negatively correlated with duration of DM and pulsatility ratio.

CONCLUSION

Systemic endothelial dysfunction appears to be associated with DR and vascular abnormalities in patients with type 2 DM.

Multiple endothelial biomarkers and noninvasive vascular function in the general population: the Gutenberg Health Study

Vascular reactivity is reflected by blood biomarkers and noninvasive vascular function measurement. The relation of biomarkers to flow-mediated dilation and peripheral arterial tonometry in the general population is little understood. In 5000 individuals (mean age, 56±11 years; age range, 35-74 years; 49% women) of the population-based Gutenberg Health Study we simultaneously assessed 6 biomarkers of cardiovascular function (midregional proadrenomedullin [MR-proADM], midregional pro atrial natriuretic peptide [MR-proANP], N-terminal pro B-type natriuretic peptide, copeptin, C-terminal proendothelin 1, and neopterin) in relation to flow-mediated dilation and peripheral arterial tonometry. Strongest partial correlations (adjusted for age and sex) were observed for baseline pulse amplitude with MR-proADM (r=0.13) and MR-proANP (r=-0.13); hyperemic response variables showed the highest correlation for MR-proADM and peripheral arterial tonometry ratio (r=-0.14). In multivariable linear regression models, strongest associations with baseline vascular function were observed for MR-proANP with baseline pulse amplitude (β per SD increase [99.17%], -0.080 [-0.115 to -0.044]; P<0.0001 after Bonferroni correction for multiple testing) and MR-proADM (-0.044 [-0.070 to -0.017]; P<0.0001), as well as MR-proANP (-0.033 [-0.057 to -0.009]; P=0.0017) and N-terminal pro B-type natriuretic peptide (-0.027 [-0.051 to -0.003]; P=0.015) with brachial artery diameter. For hyperemic response variables, highest associations were seen for peripheral arterial tonometry ratio with MR-proADM (-0.022 [-0.043 to -0.004]; P=0.043), MR-proANP (0.016 [-0.0034 to 0.035]; P=0.18), and C-terminal proendothelin 1 (-0.025 [-0.043 to -0.008]; P=0.00094]. In our large, population-based study, we identified MR-proADM and MR-proANP as circulating biomarkers of vascular function most strongly related to noninvasive measures of conduit artery and peripheral arterial performance. Whether determination of blood biomarkers helps to better understand vascular pathology and may provide prognostic information needs to be investigated in future studies.

Endothelial function assessment: flow-mediated dilation and constriction provide different and complementary information on the presence of coronary artery disease

AIMS

A number of risk factors for atherosclerosis have been identified, but it remains difficult, on an individual patient basis, to predict how these factors interact in determining the development of coronary artery disease (CAD). It also remains unclear whether the study of endothelial function provides information that is additive to that of traditional risk factors.

METHODS AND RESULTS

Flow-mediated dilation (FMD) and low-flow-mediated constriction (L-FMC) were measured in 451 consecutive patients before coronary angiography. Low-flow-mediated constriction (P< 0.0001) and FMD (P=0.0005) progressively decreased with the number of diseased vessels, and L-FMC showed a significant linear correlation with the SYNTAX score (R=0.38; P< 0.0001). Logistic regression analysis confirmed the association between endothelial function parameters and CAD (P=0.001 for L-FMC, P=0.02 for FMD). Receiver operating characteristic analysis demonstrated that the addition of L-FMC alone and of the combination of FMD and L-FMC improved the predictive power of a model based on traditional risk factors for CAD (area under the curve of the risk factor model=0.716; risk factor model + FMD=0.734, P=0.1 compared with risk factor model; risk factor model + L-FMC=0.771, P=0.004; risk factor model + L-FMC + FMD=0.779, P=0.002). Reclassification statistics showed that the introduction of FMD to the model based on the traditional risk factors correctly reclassified an additional 5% of patients, and that the introduction of L-FMC net correctly reclassified 19% of the patients. There was no correlation between different parameters of endothelial function.

CONCLUSION

Endothelial function assessment provides modest but statistically significant additional information in predicting the presence of CAD.

Blood flow velocities of cerebral arteries in lacunar infarction and other ischemic strokes

Blood flow velocity is an important determinant of vascular hemodynamics. The aim of the present study was to determine the mean flow velocities (MFVs) of cerebral arteries in patients with ischemic stroke, comparing lacunar and nonlacunar infarctions. 388 consecutive patients were examined for lacunar infarction, other subtypes of ischemic stroke, and the presence of underlying internal carotid artery steno-occlusion (ICS). MFVs were measured using transcranial Doppler along the full segments of each cerebral artery including both right and left middle cerebral arteries, basilar artery, and both of the vertebral arteries. The patients were categorized into two major groups: lacunar infarction, and nonlacunar infarction with or without underlying ICS. The characteristics of patients with lacunar infarction (n=83, 21.4%) were significantly different from those with nonlacunar infarctions: younger age, lower prevalence of type 2 diabetes, and lower concentration of plasma total homocysteine. The patients with lacunar infarction had lower MFVs in cerebral arteries than the patients with nonlacunar infarctions, especially in the posterior circulation vessels such as the basilar artery and both vertebral arteries. Different hemodynamics might be pathophysiologically associated with the lacunar infarction, compared with the other subtypes of ischemic stroke.

Noninvasive vascular function measurement in the community: cross-sectional relations and comparison of methods

BACKGROUND

Several methods of noninvasive vascular function testing have been suggested for cardiovascular risk screening in the community. A direct comparison of the different methods and their relation to classical cardiovascular risk factors in a large cohort is missing.

METHODS AND RESULTS

In 5000 individuals (mean age, 55.5 ± 10.9 years; age range, 35 to 74 years; women, 49.2%) of the population-based Gutenberg Heart Study, we performed simultaneous measurement of flow-mediated dilation (FMD) and peripheral arterial volume pulse determined by infrared photo (reflection index) and pneumatic plethysmography (PAT) and explored their associations. All function measures were recorded at baseline and after reactive hyperemia induced by 5-minute brachial artery occlusion. Correlations between different measures of vascular function were statistically significant but moderate. The strongest association for hyperemic response variables was observed for PAT ratio and FMD (Spearman r = 0.17; age- and sex-adjusted partial correlation, 0.068). Classical risk factors explained between 15.8% (baseline reflection index) and 58.4% (brachial artery diameter) of the baseline values but only accounted for 3.2% (reflection index), 15.4% (FMD), and 13.9% (PAT ratio) of the variability of reflective hyperemic response. Regression models varied in their relations to classical risk factors for the individual vascular function measures. Consistently associated with different vascular function methods were age, sex, body mass index, and indicators of hypertension. Peripheral tonometry also showed a relation to fasting glucose concentrations.

CONCLUSIONS

Noninvasive measures of conduit artery and peripheral arterial function are modestly correlated, differ in their relation to classical cardiovascular risk factors, and may thus reflect different pathologies.

Relationship between upper and lower limb conduit artery vasodilator function in humans

Brachial artery flow-mediated dilation (FMD) is a strong predictor of future cardiovascular disease and is believed to represent a "barometer" of systemic endothelial health. Although a recent study [Padilla et al. Exp Biol Med (Maywood) 235: 1287-1291, 2010] in pigs confirmed a strong correlation between brachial and femoral artery endothelial function, it is unclear to what extent brachial artery FMD represents a systemic index of endothelial function in humans. We conducted a retrospective analysis of data from our laboratory to evaluate relationships between the upper (i.e., brachial artery) vs. lower limb (superficial femoral n = 75; popliteal artery n = 32) endothelium-dependent FMD and endothelium-independent glyceryl trinitrate (GTN)-mediated dilation in young, healthy individuals. We also examined the relationship between FMD assessed in both brachial arteries (n = 42). There was no correlation between brachial and superficial femoral artery FMD (r(2) = 0.008; P = 0.46) or between brachial and popliteal artery FMD (r(2) = 0.003; P = 0.78). However, a correlation was observed in FMD between both brachial arteries (r(2) = 0.34; P < 0.001). Brachial and superficial femoral artery GTN were modestly correlated (r(2) = 0.13; P = 0.007), but brachial and popliteal artery GTN responses were not (r(2) = 0.08; P = 0.11). Collectively, these data indicate that conduit artery vasodilator function in the upper limbs (of healthy humans) is not predictive of that in the lower limbs, whereas measurement of FMD in one arm appears to be predictive of FMD in the other. These data do not support the hypothesis that brachial artery FMD in healthy humans represents a systemic index of endothelial function.

Progressive handgrip exercise: evidence of nitric oxide-dependent vasodilation and blood flow regulation in humans

In the peripheral circulation, nitric oxide (NO) is released in response to shear stress across vascular endothelial cells. We sought to assess the degree to which NO contributes to exercise-induced vasodilation in the brachial artery (BA) and to determine the potential of this approach to noninvasively evaluate NO bioavailability. In eight young (25 ± 1 yr) healthy volunteers, we used ultrasound Doppler to examine BA vasodilation in response to handgrip exercise (4, 8, 12, 16, 20, and 24 kg) with and without endothelial NO synthase blockade [intra-arterial N(G)-monomethyl-L-arginine (L-NMMA), 0.48 mg · dl(-1) · min(-1)]. Higher exercise intensities evoked significant BA vasodilation (4-12%) that was positively correlated with the hyperemic stimulus (r = 0.98 ± 0.003, slope = 0.005 ± 0.001). During NO blockade, BA vasodilation at the highest exercise intensity was reduced by ∼70% despite similar exercise-induced increases in shear rate (control, +224 ± 30 s(-1); L-NMMA, +259 ± 46 s(-1)). The relationship and slope of BA vasodilation with increasing shear rate was likewise reduced (r = 0.48 ± 0.1, slope = 0.0007 ± 0.0005). We conclude that endothelial NO synthase inhibition with L-NMMA abolishes the relationship between shear stress and BA vasodilation during handgrip exercise, providing clear evidence of NO-dependent vasodilation in this experimental model. These results support this paradigm as a novel and valid approach for a noninvasive assessment of NO-dependent vasodilation in humans.

Conventional and Mendelian randomization analyses suggest no association between lipoprotein(a) and early atherosclerosis: the Young Finns Study

BACKGROUND

Lipoprotein(a) [Lp(a)] is an established risk factor for coronary disease and stroke, but mechanisms underlying this association are unknown. We examined the association of Lp(a) with early atherosclerosis by using conventional epidemiologic analysis and a Mendelian randomization analysis. The latter utilized genetic variants that are associated with Lp(a) to estimate causal effect.

METHODS

A prospective population-based cohort study of 939 men and 1141 women was conducted. Lp(a) was measured repeatedly at mean ages 17 and 38 years. Measurements of carotid intima-media thickness (IMT) and brachial flow-mediated dilation (FMD) at mean ages 32 and 38 years were used to determine the level and 6-year progression of subclinical atherosclerosis. Lp(a)-related genetic variant, rs783147, was identified by a genome wide association analysis (P = 3.1 × 10⁻⁵⁸), and a genetic score was constructed based on 10 Lp(a)-related variants. Mendelian randomization test was performed using a two-stage instrumental variables analysis.

RESULTS

rs783147 and the genetic score were strong instruments for nonconfounded Lp(a) levels (F-statistics 269.6 and 446.0 in the first-stage instrumental variable analysis). However, Lp(a) levels were not associated with the levels of or change in IMT or FMD in any of the conventional and instrumental variables tests. The null finding was observed both with rs783147 and the genetic score as instruments and remained unchanged after adjustment for clinical characteristics, such as age, sex, HDL and LDL cholesterol, ApoB, systolic and diastolic blood pressure, diabetes and smoking.

CONCLUSIONS

Data from conventional and Mendelian randomization analyses provide no support for early atherogenic effects of increased Lp(a) levels.

Impaired coronary microvascular endothelial function in men with metabolic syndrome

AIM

To assess coronary endothelial function of conduit and resistance vessels in patients with metabolic syndrome (MS).

METHODS

Seventy-eight men (mean age, 57 years) with chest pain and angiographically normal coronary arteries were included in the study. Patients with coronary spastic angina were excluded. Changes in coronary artery diameter and coronary blood flow (CBF) in response to acetylcholine (ACh) were determined using quantitative coronary angiography and Doppler velocity measurements. Coronary flow reserve was calculated as the ratio of coronary blood velocity after adenosine triphosphate infusion relative to baseline values. Patients were divided into two groups based on the presence or absence of MS.

RESULTS

There were 24 patients in the MS group (31%). The increase in CBF in response to ACh infusion was impaired in the MS group (P < 0.0001) compared to the non-MS group, whereas changes in coronary artery diameter in response to ACh infusion did not differ between the two groups. Multivariate regression analysis revealed that MS was a significant factor associated with the lesser change in CBF induced by ACh infusion at 30 μg/min (P < 0.0001, r(2) = 0.46).

CONCLUSION

Coronary endothelial dysfunction was present at the level of resistance vessels but not conduit vessels in the MS patients included in our study.