Coronary flow reserve, insulin resistance and blood pressure response to standing in patients with normoglycaemia: is there a relationship?

The Importance of Integrated Regulation Mechanism of Coronary Microvascular Function for Maintaining the Stability of Coronary Microcirculation: An Easily Overlooked Perspective

Coronary microvascular dysfunction (CMD) refers to a group of disorders affecting the structure and function of coronary microcirculation and is associated with an increased risk of major adverse cardiovascular events. At present, great progress has been made in the diagnosis of CMD, but there is no specific treatment for it because of the complexity of CMD pathogenesis. Vascular dysfunction is one of the important causes of CMD, but previous reviews mostly considered microvascular dysfunction as a whole abnormality so the obtained conclusions are skewed. The coronary microvascular function is co-regulated by multiple mechanisms, and the mechanisms by which microvessels of different luminal diameters are regulated vary. The main purpose of this review is to revisit the mechanisms by which coronary microvessels at different diameters regulate coronary microcirculation through integrated sequential activation and briefly discuss the pathogenesis, diagnosis, and treatment progress of CMD from this perspective.

Effects of Exercise On Coronary Flow Reserve And Biochemical Parameters in Patients With Type 2 Diabetes Mellitus

The most important mortality and morbidity causes in diabetic patients are coronary, peripheral and cerebral diseases. The aim of our study was to noninvasively determine dysfunction in epicardial coronary arteries and microvascular circulation with measurement of coronary flow reserve using transthoracic echocardiography in patients with type 2 diabetes despite absence of ischemic symptoms, and to demonstrate the amelioration in endothelial functions, glycemic control and insulin resistance along with increase in coronary flow reserve after 8 weeks of regular exercise. 40 patients diagnosed with type 2 diabetes in Istanbul Facuty of Medicine, Department of Diabetes, who were on follow-up for at least three years due to diabetes, without ischemic symptoms and 20 healthy subjects took part in study. Basal values before exercise of diabetic patients who were included in the exercise program were compared with basal values of diabetic patients who did not exercise regularly. To summarize, regular exercise and physical activity are highly important in diabetic patients for primary and secondary protection against cardiovascular incidents. Physical activity increases insulin sensitivity in diabetic patients, and has many positive effects on glucose metabolism. It is the important way to decrease obesity and visceral fat tissue. There is evidence pointing out that regular exercise can defer or even prevent initiation of diabetes.

Increased Short-Term Beat-to-Beat QT Interval Variability in Patients with Impaired Glucose Tolerance

Prediabetic states and diabetes are important risk factors for cardiovascular morbidity and mortality. Determination of short-term QT interval variability (STVQT) is a non-invasive method for assessment of proarrhythmic risk. The aim of the study was to evaluate the STVQT in patients with impaired glucose tolerance (IGT). 18 IGT patients [age: 63 ± 11 years, body mass index (BMI): 31 ± 6 kg/m2, fasting glucose: 6.0 ± 0.4 mmol/l, 120 min postload glucose: 9.0 ± 1.0 mmol/l, hemoglobin A1c (HbA1c): 5.9 ± 0.4%; mean ± SD] and 18 healthy controls (age: 56 ± 9 years, BMI: 27 ± 5 kg/m2, fasting glucose: 5.2 ± 0.4 mmol/l, 120 min postload glucose: 5.5 ± 1.3 mmol/l, HbA1c: 5.4 ± 0.3%) were enrolled into the study. ECGs were recorded, processed, and analyzed off-line. The RR and QT intervals were expressed as the average of 30 consecutive beats, the temporal instability of beat-to-beat repolarization was characterized by calculating STVQT as follows: STVQT = Σ|QTn + 1 - QTn| (30x√2)-1. Autonomic function was assessed by means of standard cardiovascular reflex tests. There were no differences between IGT and control groups in QT (411 ± 43 vs 402 ± 39 ms) and QTc (431 ± 25 vs 424 ± 19 ms) intervals or QT dispersion (44 ± 13 vs 42 ± 17 ms). However, STVQT was significantly higher in IGT patients (5.0 ± 0.7 vs 3.7 ± 0.7, P < 0.0001). The elevated temporal STVQT in patients with IGT may be an early indicator of increased instability of cardiac repolarization during prediabetic conditions.

[Evaluation of vascular function by modern non-invasive methods]

Vascular functional alterations frequently precede morphological changes and, therefore, their recognition may theoretically improve early detection of vascular injury. The aim of this review is to demonstrate recently available non-invasive clinical methods including vascular stiffness examinations, flow-mediated vasodilatation, coronary flow reserve and myocardial flow reserve measurements.

[Functional vascular alterations associated with aortic valve stenosis]

Degenerative changes, atherosclerotic process and calcification of valvular leaflets are mostly responsible for valvular aortic valve stenosis, but congenital bicuspid aortic valve and rheumatic fever in history are also known predisposing factors. Aortic valve stenosis is frequently associated with different functional vascular alterations. The aim of this review is to demonstrate these vascular alterations evaluated by non-invasive methods and underlying physiologic and pathophysiologic processes.

Impact of Abnormal Glucose Tolerance, Hypertension and Other Risk Factors on Coronary Artery Disease

BACKGROUND

The degree to which abnormal glucose tolerance contributes to the development of coronary artery disease (CAD) has not been clarified in Japanese. The relationship between abnormal glucose tolerance and severity of coronary artery stenosis, as well as the contributions of hypertension, diabetes and other risk factors for CAD to recurrence of the disease, were investigated in the present study.

METHODS AND RESULTS

The subjects were 474 consecutive patients (mean age: 63.8+/-11.3 years) with suspected CAD who were admitted to Sapporo Medical University Hospital during April 1, 1997 to March 31, 2004. The coronary index and stenosis score were higher in subjects with diabetes mellitus (DM) and in subjects with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) than in subjects with normal glucose tolerance (NGT). Ischemic episodes recurred during the observation period (mean 2.5 years) in 61 of 341 patients diagnosed as having CAD. In the follow-up subjects, systolic blood pressure (SBP) was significantly higher in the recurrence group than in the non-recurrence group, and SBP was a significant variable in logistic regression analysis after adjustment for age, gender, hemoglobin A1c, total cholesterol, body mass index, smoking history, family history and stenosis score. The relative risk of recurrence became 1.7-fold higher with a rise in SBP of 10 mmHg (95% confidence interval: 1.252-2.250). Analysis of the relationship between glucose tolerance and recurrence showed that the rate of recurrence was higher in patients with IFG+IGT+DM than in those with NGT.

CONCLUSIONS

CAD progresses not only in patients with DM but also in those with IGT. The rate of recurrence of ischemic episodes increases in individuals with IGT or DM, and suggesting that hypertension is a risk factor for recurrence of ischemic episodes. Management of glucose tolerance and blood pressure is therefore important for prevention of CAD in Japanese.