Acute Hyperglycemia Induced by Oral Glucose Loading Suppresses Coronary Microcirculation on Transthoracic Doppler Echocardiography in Healthy Young Adults

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.

No acute hyperglycemia induced impairment in brachial artery flow-mediated dilation before or after aerobic exercise training in young recreationally active males

There is some evidence that transient endothelial dysfunction induced by acute hyperglycemia may be attenuated by a single bout of aerobic exercise. However, the impact of aerobic exercise training on acute hyperglycemia-induced endothelial dysfunction has not been explored. The purpose of this study was to determine the impact of aerobic exercise training on the endothelial function response to acute hyperglycemia. Brachial artery flow-mediated dilation (FMD) was assessed in 24 healthy males (21 ± 1 years) pre-, 60 and 90 min post ingestion of 75 g of glucose. Participants completed a four-week control (CON; n = 13) or exercise training (EX; n = 11) intervention. The EX group completed four weeks of cycling exercise (30 min, 4×/week at 65% work rate peak). Cardiorespiratory fitness ([Formula: see text]O2peak) increased and resting HR decreased in EX, but not CON post-intervention (p < 0.001). Glucose and insulin increased (p < 0.001) following glucose ingestion, with no significant difference pre- and post-intervention. In contrast to previous research, FMD was unaffected by glucose-ingestion, pre- and post-intervention in both groups. In conclusion, acute hyperglycemia did not impair endothelial function, before or after exercise training. Relatively high baseline fitness ([Formula: see text]O2peak ~ 46 mL/kg/min) and young age may have contributed to the lack of impairment observed. Further research is needed to examine the impact of exercise training on hyperglycemia-induced impairments in endothelial function in sedentary males and females.

An oral glucose tolerance test does not affect cerebral blood flow: role of NOS

Animal data indicate that insulin triggers a robust nitric oxide synthase (NOS)-mediated dilation in cerebral arteries similar to the peripheral tissue vasodilation observed in healthy adults. Insulin's role in regulating cerebral blood flow (CBF) in humans remains unclear but may be important for understanding the links between insulin resistance, diminished CBF, and poor brain health outcomes. We tested the hypothesis that an oral glucose challenge (oral glucose tolerance test, OGTT), which increases systemic insulin and glucose, would acutely increase CBF in healthy adults due to NOS-mediated vasodilation, and that changes in CBF would be greater in anterior regions where NOS expression or activity may be greater. In a randomized, single-blind approach, 18 young healthy adults (24 ± 5 yr) underwent magnetic resonance imaging (MRI) with a placebo before and after an OGTT (75 g glucose), and 11 of these adults also completed an NG-monomethyl-l-arginine (l-NMMA) visit. Four-dimensional (4-D) flow MRI quantified macrovascular CBF and arterial spin labeling (ASL) quantified microvascular perfusion. Subjects completed baseline imaging with a placebo (or l-NMMA), then consumed an OGTT followed by MRI scans and blood sampling every 10-15 min for 90 min. Contrary to our hypothesis, total CBF (P = 0.17) and global perfusion (P > 0.05) did not change at any time point up to 60 min after the OGTT, and no regional changes were detected. l-NMMA did not mediate any effect of OGTT on CBF. These data suggest that insulin-glucose challenge does not acutely alter CBF in healthy adults.

HbA1c level is associated with the development of heart failure with recovered ejection fraction in hospitalized heart failure patients with type 2 diabetes

BACKGROUND

Due to advances in medical treatments, a substantial proportion of heart failure (HF) patients with reduced left ventricular ejection fraction (EF, HFrEF) have experienced partial or complete recovery of EF, termed HFrecEF, and markedly improved clinical outcomes. In the present study, we sought to investigate the relationship between glycemic control and the incidence of HFrecEF in hospitalized HFrEF patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 463 hospitalized T2DM patients with HFrEF were consecutively enrolled. Follow-up echocardiogram was performed after around 12 months. Patients who had an absolute EF improvement ≥10% and a second EF > 40% were classified into HFrecEF, and those who did not meet these criteria were defined as persistent HFrEF.

RESULTS

During the 12-month follow-up, 44.5% of T2DM patients developed HFrecEF. Patients with HFrecEF had significantly lower HbA1c level than those with persistent HFrEF (6.5% [IQR 5.8% ∼ 7.2%] vs. 6.7% [IQR 6.1% ∼ 7.8%], P = 0.003), especially in HF of an ischemic etiology. HbA1c levels were inversely correlated with changes in EF during follow-up. After multivariate adjustment, every 1% increase in HbA1c conferred a 17.4% (OR: 0.826 [95% CI 0.701-0.968]) lower likelihood of HFrecEF. Compared to patients with good glycemic control (HbA1c ≤ 6.2%), those with poor glycemic control (HbA1c > 7.1%) had a 52.0% (OR: 0.480 [95% CI 0.281-0.811] decreased likelihood of HFrecEF.

CONCLUSIONS

This study demonstrates that uncontrolled HbA1c level is associated with compromised development of HFrecEF in T2DM patients with HF, especially in those with an ischemic etiology.

The Role of Systemic Microvascular Dysfunction in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a condition with increasing incidence, leading to a health care problem of epidemic proportions for which no curative treatments exist. Consequently, an urge exists to better understand the pathophysiology of HFpEF. Accumulating evidence suggests a key pathophysiological role for coronary microvascular dysfunction (MVD), with an underlying mechanism of low-grade pro-inflammatory state caused by systemic comorbidities. The systemic entity of comorbidities and inflammation in HFpEF imply that patients develop HFpEF due to systemic mechanisms causing coronary MVD, or systemic MVD. The absence or presence of peripheral MVD in HFpEF would reflect HFpEF being predominantly a cardiac or a systemic disease. Here, we will review the current state of the art of cardiac and systemic microvascular dysfunction in HFpEF (Graphical Abstract), resulting in future perspectives on new diagnostic modalities and therapeutic strategies.

The Heart in Diabetic Ketoacidosis: A Narrative Review Focusing on the Acute Cardiac Effects and Electrocardiographic Abnormalities

Diabetic ketoacidosis (DKA) is a serious complication of diabetes mellitus. Hyperglycemia, acidosis, and electrolyte imbalances can directly affect the heart by inducing toxicity, impairing myocardial blood flow, autonomic dysfunction, and altering activation and conduction of electrical impulses throughout the heart, increasing the risk of arrhythmias and ischemia. The electrocardiogram is useful in monitoring patients during and after an episode of DKA, as it allows the detection of arrhythmias and guides metabolic correction. Unfortunately, reports on electrocardiographic abnormalities in patients with DKA are lacking. We found two electrocardiographic patterns that are frequently reported in the literature: a pseudo-myocardial infarction and a Brugada Phenocopy. Both are associated with DKA metabolic anomalies and they resolve after treatment. Because of their clinical relevance and the challenge they represent for clinicians, we analyzed the clinical characteristics of these patients and the mechanisms involved in these electrocardiographic findings.

Role of plasma glucose level on myocardial perfusion in ST-segment elevation myocardial infarction patients

AIMS

Hyperglycemia is frequent in patients with ST elevation myocardial infarction (STEMI) and is associated with adverse outcome. Aim of our study was to evaluate the correlation between admission plasma glucose level (PGL) and coronary arteries flow velocity.

METHODS

We enrolled 149 STEMI patients successfully treated with primary percutaneous coronary intervention (pPCI). The study population was divided into two groups based on PGL (< or >140 mg/dl) and on history of diabetes, and the groups compared in terms of corrected TIMI frame count (cTFC).

RESULTS

Hyperglycemic patients had a significantly higher cTFC in both the culprit (p < 0.0001) and non-culprit vessel (p: 0.0002); diabetes history impairs as well cTFC of the culprit (p < 0.0001) and non-culprit vessel (p: 0.0001). Within the subpopulation of diabetic patients hyperglycemic ones showed higher cTFC in both the culprit (p 0.0013) and non-culprit vessel (p: 0.0006). Moreover in the whole population cTFC values of both arteries increase linearly with the increment of admission PGL.

CONCLUSIONS

Admission PGL affects coronary flow of both culprit and non-culprit vessel. The impairment of coronary flow is also demonstrated in known diabetic patients, suggesting to consider hyperglycemia an additional risk factor. We finally demonstrated for the first time a positive linear relationship between PGL and cTFC.

Effect of Dipyridamole Injected for Myocardial Perfusion Imaging on Blood Glucose Concentration; A Preliminary Study

INTRODUCTION

Dipyridamole inhibits adenosine reuptake and increases cyclic Adenosine Monophosphate (cAMP) levels in platelets, erythrocytes and endothelial cells, all of which influence blood glucose. Acute hyperglycaemia reduces endothelium-dependent vasodilation and suppresses coronary microcirculation; which, in theory, can alter the outcome of a radionuclide scan.

AIM

The present study was conducted with the aim to investigate the changes in blood glucose level of patients receiving dipyridamole for cardiac scan.

MATERIALS AND METHODS

A total of 293 patients (85 men and 208 women, age: 60.59±10.43 years) were included in the study. Fasting Blood Glucose (FBG) was measured before and 8 min after dipyridamole (0.568 mg/kg) injection during myocardial perfusion imaging. The data in different groups were analysed by paired t-test.

RESULTS

There was not a significant difference between first (106.89 ± 19.21mg/dL) and second (107.98 ± 17.57 mg/dL) FBG measurements (p= 0.293). However, when the patients were grouped based on the quartiles of first measurement, there was an increase in FBG following dipyridamole injection in the first quartile (mean difference: 7.15±21.27 mg/dL, p<0.01); in contrast, FBG levels showed a significant decrease after dipyridamole administration in the 4(th) quartile (mean difference: -9.53±18.20 mg/dL, p<0.001). The differences in 2(nd) and 3(rd) quartiles were negligible. The patients were divided into normal, ischemic and fixed lesions based on the outcome of scans, then the possible correlation of dipyridamole-induced FBG alteration and scan results were investigated. There were no significant difference between the FBG values before and after dipyridamole injection and the final outcome of scan.

CONCLUSION

The effects of dipyridamole on blood glucose highly depend on the initial blood glucose level.

Acute Hyperglycemia Impairs Vascular Function in Healthy and Cardiometabolic Diseased Subjects

Objectives—

Controversy exists over the effect of acute hyperglycemia on vascular function. In this systematic review, we compared the effect of acute hyperglycemia on endothelial and vascular smooth muscle functions across healthy and cardiometabolic diseased subjects.

Approach and Results—

A systematic search of MEDLINE, EMBASE, and Web of Science from inception until July 2014 identified articles evaluating endothelial or vascular smooth muscle function during acute hyperglycemia and normoglycemia. Meta-analyses compared the standardized mean difference (SMD) in endothelial and vascular smooth muscle functions between acute hyperglycemia and normoglycemia. Subgroup analyses and metaregression identified sources of heterogeneity. Thirty-nine articles (525 healthy and 540 cardiometabolic subjects) were analyzed. Endothelial function was decreased (39 studies; n=1065; SMD, −1.25; 95% confidence interval, −1.52 to −0.98; P <0.01), whereas vascular smooth muscle function was preserved (6 studies; n=144; SMD, −0.07; 95% confidence interval, −0.30 to 0.16; P =0.55) during acute hyperglycemia compared with normoglycemia. Significant heterogeneity was detected among endothelial function studies ( P <0.01). A subgroup analysis revealed that endothelial function was decreased in the macrocirculation (30 studies; n=884; SMD, −1.40; 95% confidence interval, −1.68 to −1.12; P <0.01) but not in the microcirculation (9 studies; n=181; SMD, −0.63; 95% confidence interval, −1.36 to 0.11; P =0.09). Similar results were observed according to health status. Macrovascular endothelial function was inversely associated with age, blood pressure, and low-density lipoprotein cholesterol and was positively associated with the postocclusion interval of vascular assessment.

Conclusions—

To our knowledge, this is the first systematic review and meta-analysis of its kind. In healthy and diseased subjects, we found evidence for macrovascular but not microvascular endothelial dysfunction during acute hyperglycemia.

Metabolic Syndrome is Associated With Higher Wall Motion Score and Larger Infarct Size After Acute Myocardial Infarction

Background:

Infarct size is an important surrogate end point for early and late mortality after acute myocardial infarction. Despite the high prevalence of metabolic syndrome in patients with atherosclerotic diseases, adequate data are still lacking regarding the extent of myocardial necrosis after acute myocardial infarction in these patients.

Objectives:

In the present study we aimed to compare myocardial infarction size in patients with metabolic syndrome to those without metabolic syndrome using peak CK-MB and cardiac troponin I (cTnI) at 72 hours after the onset of symptoms.

Patients and Methods:

One-hundred patients with metabolic syndrome (group I) and 100 control subjects without metabolic syndrome (group II) who experienced acute myocardial infarction were included in the study. Diagnosis of metabolic syndrome was based on the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) guidelines published in 2001. Myocardial infarction size was compared between the two groups of patients using peak CK-MB and cTnI level in 72 hours after the onset of symptoms.

Results:

Peak CK-MB and cTnI in 72 hours were found to be significantly higher in patients with metabolic syndrome compared with control subjects (both P < 0.001). Patients with metabolic syndrome also had markedly higher wall motion abnormality at 72 hours after the onset of symptoms as assessed by echocardiographically-derived Wall Motion Score Index (WMSI) (P < 0.001). Moreover, statistically significant relationships were found between WMSI and peak CK-MB and also cTnI at 72 hours (Spearman's rho = 0.56, P < 0.001 and Spearman's rho = 0.5, P < 0.001; respectively). However, association between WMSI and left ventricular ejection fraction was insignificant (Spearman's rho = -0.05, P = 0.46).

Conclusions:

We showed that patients with metabolic syndrome have larger infarct size compared to control subjects.

Coronary Microvascular Function and Beyond: The Crosstalk between Hormones, Cytokines, and Neurotransmitters

Beyond its hemodynamic function, the heart also acts as a neuroendocrine and immunoregulatory organ. A dynamic communication between the heart and other organs takes place constantly to maintain cardiovascular homeostasis. The current understanding highlights the importance of the endocrine, immune, and nervous factors to fine-tune the crosstalk of the cardiovascular system with the entire body. Once disrupted, this complex interorgan communication may promote the onset and the progression of cardiovascular diseases. Thus, expanding our knowledge on how these factors influence the cardiovascular system can lead to novel therapeutic strategies to improve patient care. In the present paper, we review novel concepts on the role of endocrine, immune, and nervous factors in the modulation of microvascular coronary function.

Acute hyperglycemia reduces myocardial blood flow reserve and the magnitude of reduction is associated with insulin resistance: a study in nondiabetic humans using contrast echocardiography

The effect of acute hyperglycemia per se on coronary perfusion in humans is undefined. We evaluated the effects of short-term hyperglycemia on myocardial blood flow reserve (MBFR) in healthy nondiabetic volunteers. Twenty-one nondiabetic volunteers (76 % females, mean ± SD, age 48 ± 5 years) had noninvasive MBFR assessment while exposed to pancreatic clamp with somatostatin and replacement glucagon and growth hormone infusions, with frequent interval plasma glucose (PG) monitoring. Insulin was infused at 0.75 mU/kg/min to mimic postprandial plasma insulin concentrations, and glucose was infused to maintain euglycemia (PG 93.9 ± 7.3 mg/dl) followed by hyperglycemia (PG 231.5 ± 18.1 mg/dl). Myocardial contrast echocardiography (MCE) was performed during each glycemic steady state using continuous infusion of Definity at rest and during regadenoson (Lexiscan 5 ml (400 μg) intravenous bolus) infusion to quantify myocardial blood flow (MBF) and determine MBFR. Insulin resistance (IR) was assessed by glucose infusion rate (GIR; mg/kg/min) at euglycemia. Median stress MBF, MBFR, and β reserve were significantly reduced during acute hyperglycemia versus euglycemia (stress MBF 3.9 vs 5.4, P = 0.02; MBFR 2.0 vs 2.7, P < 0.0001; β reserve 1.45 vs 2.4, P = 0.007). Using a median threshold GIR of 5 mg/kg/min, there was a correlation between GIR and hyperglycemic MBFR (r = 0.506, P = 0.019). MBFR, as determined noninvasively by MCE, is significantly decreased during acute hyperglycemia in nondiabetic volunteers, and the magnitude of this reduction is modulated by IR.

Comparison of coronary microcirculation in female nurses after day-time versus night-time shifts

Nightshift work, which is known to cause mental stress and disrupt normal biological diurnal rhythms, leads to endothelial dysfunction resulting in increased risk for cardiovascular disease. This study aimed to investigate the acute effect of night-shift work on coronary microcirculation through assessment of coronary flow reserve (CFR) by transthoracic Doppler echocardiography. This study consisted of 36 women nurses who underwent transthoracic Doppler echocardiographic examinations after working a nightshift and on a regular day without previous nightshift work. Flow velocity in the distal portion of the left anterior descending coronary artery was measured at baseline and during adenosine infusion. CFR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFR after night work was lower than that on a regular workday (3.8 ± 0.6 vs 4.1 ± 0.6, p <0.001). Degree of decreases in CFR after night work was correlated to Framingham risk score (r = 0.35, p = 0.036). In conclusion, this study demonstrated that coronary microcirculation was impaired after nightshift work in women nurses.

The correlation between the oral glucose tolerance test 30-minutes plasma glucose and risk factors for diabetes and cardiovascular diseases: a cross-sectional epidemiological study of diabetes in Fujian Province in the South-East of China

OBJECTIVE

To investigate the correlation between abnormal oral glucose tolerance test (OGTT) 30-min plasma glucose (PG) and risk factors and metabolic abnormalities of diabetes and cardiovascular diseases (CVD).

METHODS

Participants (no.=2457) underwent a physical examination, blood biochemistry examination, OGTT, and a 12-lead electrocardiogram. We measured fasting PG (FPG) and PG at 30 min (30minPG) and 1 h (1hPG) of the OGTT. The association between an increase in 30minPG (by 1 SD) and the metabolic abnormalities of diabetes and CVD such as hypertension, overweight and obesity, central obesity, and hyperlipidemia; osteoporosis was assessed by logistic regression analysis after controlling for FPG and 2hPG.

RESULTS

This analysis showed that an increase of 30minPG by 1 SD (1.92 mmol/l) significantly increased the risk of chronic metabolic abnormalities in diabetes and CVD such as hypertension, overweight, and obesity, central obesity, hyperlipidemia, and osteoporosis. Stepwise multiple regression analysis also showed that 30minPG was significantly correlated with male gender, smoking, FPG, 2hPG, total cholesterol, waist/hip ratio, and blood pressure.

CONCLUSIONS

An elevation of 30minPG increased the risk of diabetes and CVD. The increased risk was independent of FPG, 2hPG, age, sex, and smoking status.

Circadian variation in coronary flow velocity reserve and its relation to α1-sympathetic activity in humans

BACKGROUND

The circadian change in coronary microvascular function has not been directly assessed in human beings. Recent advances in transthoracic Doppler echocardiography (TTDE) provide noninvasive, physiological assessment of coronary flow velocity reserve (CFVR).

METHODS

This study consisted of 20 young healthy subjects (24 ± 2 years, 20 men) who underwent CFVR examinations at 3 different times; early morning (6AM), late morning (11AM) and late evening (10PM). The flow velocity in the distal portion of the left anterior descending coronary artery was measured with TTDE at baseline and during adenosine infusion to calculate CFVR. These examinations were repeated with the intake of α1-blocker (prazosin 1mg) on the other day.

RESULTS

CFVR showed a circadian variation with an increase from the early morning to the late morning, following a decrease to the late evening thereafter (4.4 ± 0.9 at 6AM; 5.2 ± 1.3 at 11AM; 4.2 ± 1.1 at 10PM, p<0.001). In the study with α1-blocker, CFVR was comparable between the early morning and the late morning, whereas CFVR in the late evening was lower than those in other 2 time points (5.0 ± 1.1 at 6AM; 4.9 ± 0.9 at 11AM; 4.3 ± 0.9 at 10PM, p<0.001).

CONCLUSIONS

This study demonstrates that CFVR has a circadian variation in humans, with an increase from the late evening to the late morning. Adding α1-blocker ameliorated CFVR only in the early morning, indicating that α1-sympathetic activity plays a heterogeneous and important role in the circadian change of CFVR in humans.

Aromatherapy alleviates endothelial dysfunction of medical staff after night-shift work: preliminary observations

Night-shift work causes mental stress and lifestyle changes, and is recognized as a risk of cardiovascular diseases associated with impaired endothelial function. Aromatherapy is becoming popular as a complementary therapy that is beneficial for mental relaxation. The purpose of this study was to investigate the effect of aromatherapy on the endothelial function of medical staff after night-shift work. This study consisted of 19 healthy medical personnel (19 men, mean age 32 ± 7 years), including 11 physicians and 8 technicians. Aromatherapy was performed for 30 min by inhalation of the essential oil of lavender. Flow-mediated dilation (FMD) of the brachial artery was measured three times in each subject: on a regular workday, and after night-shift work before and immediately after aromatherapy. A control study was performed to assess the effect of a 30-min rest without aromatherapy. The mean value of sleep time during night-shift work was 3.3 ± 1.3 h. FMD after night-shift work was lower than on a regular workday (10.4 ± 1.8 vs. 12.5 ± 1.7%, P<0.001), which improved after aromatherapy (11.8 ± 2.5%, P=0.02 vs. before aromatherapy). FMD was stable in the control study (10.1 ± 1.9 vs. 10.1 ± 2.2%, P=0.9). This study demonstrated that night-shift work impaired endothelial function in medical staff, an effect that was alleviated by short-term aromatherapy.

"Passive exercise" using whole body periodic acceleration: effects on coronary microcirculation

BACKGROUND

The whole body periodic acceleration (WBPA) system has recently been developed as a "passive exercise" device by providing increased pulsatile shear stress for improvement of endothelial function. This study aimed to investigate the short-term effect of WBPA on coronary flow reserve (CFR) through transthoracic Doppler echocardiography (TTDE) in healthy subjects and patients with coronary artery disease (CAD).

METHODS

This study consisted of 15 healthy subjects and 20 patients with CAD who underwent CFR examination before and immediately after WBPA. The flow velocity in the distal portion of the left anterior descending coronary artery (LAD) was measured with TTDE at baseline and during adenosine infusion. Coronary flow reserve was calculated as the ratio of hyperemic to basal mean diastolic flow velocity.

RESULTS

The WBPA treatment was completed in all 35 subjects without complications. There were no significant differences in heart rate and systolic blood pressure before and after WBPA. Whole body periodic acceleration increased CFR from 3.3 +/- 1.0 to 3.7 +/- 1.1 in the 35 subjects (P < .001). Coronary angiography showed significant LAD narrowing in 8 of the 20 CAD patients, but WBPA increased CFR from 2.4 +/- 0.4 to 2.7 +/- 0.5 in them as well (P < .01).

CONCLUSIONS

This study demonstrates that WBPA improves CFR in healthy subjects and patients with CAD.

Influence of abnormal glucose metabolism on coronary microvascular function after a recent myocardial infarction

OBJECTIVES

This study sought to assess the association between abnormal glucose metabolism and abnormal coronary flow reserve (CFR) in patients with a recent acute myocardial infarction (AMI).

BACKGROUND

Mortality and morbidity after AMI is high among patients with abnormal glucose metabolism, which may be related to abnormal microcirculation.

METHODS

We studied 183 patients with a first AMI. In 161 patients with no history of diabetes mellitus (DM), an oral glucose tolerance test was performed, and patients were categorized according to World Health Organization criteria for whole blood glucose into 3 groups. After coronary angiography and revascularization, a comprehensive transthoracic echocardiogram and noninvasive assessment of CFR was performed in the distal part of left descending artery, as an indicator of microvascular function. Adenosine was administered by intravenous infusion (140 microg/kg/min) to obtain the hyperemic flow profiles. The CFR was defined as the ratio of hyperemic to baseline peak diastolic coronary flow velocities.

RESULTS

Median CFR was 1.9 (interquartile range [IQR] 1.4 to 2.4], and 109 (60%) patients had a CFR <or=2. The lowest CFR was seen in patients with a history of DM (1.4 [IQR 1.4 to 1.7], n = 22) and in patients with newly diagnosed DM (1.6 [IQR 1.3 to 2], n = 39), whereas CFR did not differ in patients with abnormal glucose tolerance (2.1 [IQR 1.4 to 2.6], n = 58) and in patients with normal glucose tolerance (2.2 [IQR 1.7 to 2.6], n = 62). In a stepwise logistic regression model adjusting for age, sex, site and size of AMI, heart rate, risk factors of the metabolic syndrome, degree of angiographic evidence of coronary artery disease, and medical therapy, newly diagnosed DM (odds ratio: 3.0) and a history of DM (odds ratio: 9.9) remained significant predictors of CFR <2, whereas impaired glucose tolerance was not.

CONCLUSIONS

CFR is decreased in patients with known or newly diagnosed DM even after adjustment of possible confounders, whereas CFR in patients with impaired glucose tolerance seems less affected. (Coronary Flow Reserve and Glucometabolic State [CFRGS]; NCT00845468).

Acute hyperglycemia enhances oxidative stress and exacerbates myocardial infarction by activating nicotinamide adenine dinucleotide phosphate oxidase during reperfusion

OBJECTIVE

Acute hyperglycemia is independently associated with larger myocardial infarct size in both diabetic and nondiabetic patients. We hypothesized that the oxidative stress imposed by acute hyperglycemia contributes to the exacerbation of infarct size during reperfusion.

METHODS

C57BL/6 mice underwent 30 minutes of occlusion of the left anterior descending coronary artery followed by 60 minutes of reperfusion. Acute hyperglycemia was induced with an intraperitoneal injection of dextrose (2g/kg body weight) 30 minutes before left anterior descending occlusion. An antioxidant, N-2-mercaptopropionyl glycine, was injected intravenously 2 minutes before the onset of reperfusion at a dose of 20 mg/kg. A nicotinamide adenine dinucleotide phosphate oxidase inhibitor, apocynin (50 mg/kg), was applied either before or after the induction of hyperglycemia.

RESULTS

Blood glucose level before left anterior descending occlusion was 153 +/- 19 mg/dL in control mice and 444 +/- 26 mg/dL in hyperglycemic mice (P < .05). Plasma lipid peroxidation product (malondialdehyde) was significantly increased in both control and hyperglycemic mice at 1 hour after reperfusion, and levels of malondialdehyde in hyperglycemic mice were higher than that in control mice (3.38 +/- 0.21 vs 2.33 +/- 0.12 micromol/L; P < .05). N-2-mercaptopropionyl glycine administered just before reperfusion significantly reduced malondialdehyde levels in both control and hyperglycemic mice (1.21 +/- 0.06 and 1.03 +/- 0.24 micromol/L). Acute hyperglycemia increased infarct size (percent of risk region) from 34.0 +/- 2.7 to 49.4 +/- 1.6 (P < .05). N-2-mercaptopropionyl glycine reduced infarct size to 19.5 +/- 2.3 in control mice and to 26.2 +/- 2.9 in hyperglycemic mice. Apocynin also reduced malondialdehyde levels and infarct size in hyperglycemic mice if administered 5 minutes before injection of dextrose, but not before reperfusion.

CONCLUSION

Acute hyperglycemia enhances oxidative stress and exacerbates myocardial infarction in mice through activation of nicotinamide adenine dinucleotide phosphate oxidase.