Vasomotion and nitric oxide bioactivity in diseased coronary arteries

Inflammation and endothelial dysfunction as therapeutic targets in patients with heart failure

Evidence suggests that vascular endothelium plays key role in the regulation of vascular tone, in the process of inflammation and in the thrombotic mechanisms. Recent studies indicate that it is an important component of the pathophysiological mechanisms of heart failure. Heart failure may induce endothelial dysfunction by different mechanisms, such as reduced synthesis and release of nitric oxide (NO), increased degradation of NO or by increased production of endothelin-1. In addition, endothelial dysfunction has been associated with the progression of heart failure. Alterations in neurotransmitters, hormones and also in physiological stimuli are present in heart failure and affect the vascular endothelium. Treatments with beneficial effects on endothelial dysfunction may also improve prognosis in patients with heart failure.

Elevated plasma endothelin-1 levels in coronary sinus during rapid right atrial pacing in patients with slow coronary flow

The aim of the study was to evaluate whether there was an imbalance between endothelin-1 (ET-1) and nitric oxide (NOx) release and diffuse atherosclerotic changes existed in patients with slow coronary flow (SCF). Baseline and post-atrial pacing coronary sinus ET-1 and NOx levels were measured in 19 patients with SCF (11 female, 56 +/- 9 years) and in 14 control subjects (nine female, 54 +/- 7 years). All patients underwent subsequent intravascular ultrasound (IVUS) investigation at the same setting with right atrial pacing. Baseline arterial (12.4 +/- 9.9 vs. 6.3 +/- 5.1 pg/ml, P<0.005) and coronary sinus (12.2 +/- 11.1 vs. 6.4 +/- 6.9 pg/ml, P<0.005) ET-1 plasma levels were higher in patients than in controls. After atrial pacing, concentration of ET-1 level from coronary sinus (24.7 +/- 14.6) significantly increased as compared to baseline (12.4 +/- 9.9, P<0.0001) and control levels (5.3 +/- 6.3, P<0.0001). Additionally, coronary sinus ET-1 level increased significantly with atrial pacing compared to femoral artery ET-1 level (16.3 +/- 8.5, P<0.005) in patients with SCF. After atrial pacing, the femoral artery ET-1 level also increased in patients compared to control level (P<0.0001). No significant differences in arterial and coronary sinus NOx plasma levels were found between the two groups, both at baseline and after pacing. Upon IVUS investigation, the common finding was longitudinally extended massive calcification throughout the epicardial arteries in patients with SCF. Mean intimal thickness was 0.59 +/- 0.18 mm. The data of this study suggest that increased ET-1 levels and insufficient NOx response, as well as the pathological data of IVUS may be associated with coronary microvascular dysfunction and may be the manifestation of early diffuse epicardial atherosclerosis in these patients with SCF.

Endothelin-1 and Nitric Oxide Concentrations and Their Response to Exercise in Patients With Slow Coronary Flow

In this study, the endothelin-1 (ET-1) and nitric oxide (NO) concentrations in slow coronary flow (SCF) patients were assessed before and at the peak of the exercise stress test and compared with the values from healthy controls. The study population was 25 patients who underwent coronary angiography and were diagnosed as SCF (11 females (44%), aged 56.7+/-9.8 years), and 20 normal subjects (9 females (45%), aged 54.3+/-9.2 years). Mean TIMI frame count in the patients was 54.1+/-13.4. Blood samples were drawn at rest and immediately at the end of exercise testing. The baseline ET-1 concentrations of the control subjects were lower than those of the patients (7.0+/-4.5 pg/ml vs 11.1+/-5.9 pg/ml p<0.0001) and this difference increased after exercise (6.2+/-4.3 pg/ml vs 20.1 +/-10.4 pg/ml, p<0.0001). Post-exercise ET-1 concentrations were significantly higher than baseline in patients with SCF (p<0.0001) and a reduction in the ET-1 concentrations was observed in control subjects (p<0.05). Baseline NO concentrations of the patients were lower than those of the control subjects (27 +/-5.1 micromol/L vs 31.2+/-4.9 micromol/L, p=0.0001). Although the NO concentrations in both groups were significantly increased after exercise (29.4 +/-5.9 micromol/L vs 33.3+/-5.6 micromol/L, p<0.05 for both), the difference was not significant. A significant negative correlation among post-exercise ET-1 concentrations and maximal heart rate, exercise duration and exercise rate - pressure product, and a significant positive correlation among post-exercise NO concentrations and maximal heart rate and exercise duration were observed in both groups. The results of this study show that endothelial function (assessed by ET-1 and NO concentrations) and its response to exercise were abnormal in SCF patients compared with healthy subjects, and this may play some pathophysiologic role.