Endothelial Function as a Possible Significant Determinant of Cardiac Function during Exercise in Patients with Structural Heart Disease

This study was investigated the role that endothelial function and systemic vascular resistance (SVR) play in determining cardiac function reserve during exercise by a new ambulatory radionuclide monitoring system (VEST) in patients with heart disease. The study population consisted of 32 patients. The patients had cardiopulmonary stress testing using the treadmill Ramp protocol and the VEST. The anaerobic threshold (AT) was autodetermined using the V-slope method. The SVR was calculated by determining the mean blood pressure/cardiac output. Flow-mediated vasodilation (FMD) was measured in the brachial artery to evaluate endotheilial function. FMD and the percent change f'rom rest to AT in SVR correlated with those from rest to AT in ejection fraction and peak ejection ratio by VEST, respectively. Our findings suggest that FMD in the brachial artery and the SVR determined by VEST in patients with heart disease can possibly reflect cardiac function reserve during aerobic exercise

Endothelial dysfunction, carotid artery plaque burden, and conventional exercise-induced myocardial ischemia as predictors of coronary artery disease prognosis

<p>Abstract</p> <p>Background</p> <p>While both flow-mediated vasodilation (FMD) in the brachial artery (BA), which measures endothelium-dependent vasodilatation, and intima-media thickness (IMT) in the carotid artery are correlated with the prognosis of coronary artery disease (CAD), it is not clear which modality is a better predictor of CAD. Furthermore, it has not been fully determined whether either of these modalities is superior to conventional ST-segment depression on exercise stress electrocardiogram (ECG) as a predictor. Thus, the goal of the present study was to compare the predictive value of FMD, IMT, and stress ECG for CAD prognosis.</p> <p>Methods and Results</p> <p>A total of 103 consecutive patients (62 ± 9 years old, 79 men) with clinically suspected CAD had FMD and nitroglycerin-induced dilation (NTG-D) in the BA, carotid artery IMT measurement using high-resolution ultrasound, and exercise treadmill testing. The 73 CAD patients and 30 normal coronary patients were followed for 50 ± 15 months. Fifteen patients had coronary events during this period (1 cardiac death, 2 non-fatal myocardial infarctions, 3 acute heart failures, and 9 unstable anginas). On Kaplan-Meier analysis, only FMD and stress ECG were significant predictors for cardiac events.</p> <p>Conclusion</p> <p>Brachial endothelial function as reflected by FMD and conventional exercise stress testing has comparable prognostic value, whereas carotid artery plaque burden appears to be less powerful for predicting future cardiac events.</p

Effect of Lateral Body Position on Heart Rate Variability in Patients with Sleep Apnea Syndrome

Sleep apnea syndrome (SAS) can exacerbate cardiovascular disease by augmenting activity of the sympathetic nervous system. One method of treating SAS is via modulation of body posture. Therefore, the goal of the present study was to investigate whether assuming the lateral position during sleep can influence autonomic nervous system activity, as assessed by measurement of heart rate variability (HRV). Six patients with coronary artery disease (CAD) complicated by SAS underwent serial measurements of HRV and arterial blood oxygen saturation (SPO2) during sleep. Online analyses for HRV was performed using five consecutive RR intervals from electrocardiography using the modified Maximum Entropy Method. Low frequency spectra (LF, 0.04–0.15 Hz), high frequency spectra (HF, 0.15–0.40 Hz) and the ratio of low and high frequency spectra (LF/HF ratio) were continuously calculated. HRV and SPO2 measurements were performed after 30 min of sleep in different sleeping positions (supine vs. lateral) with or without supplementary oxygen administration by nasal cannula. The LF and LF/HF ratio were significantly smaller in the lateral position with and without oxygen when compared with the supine position with or without oxygen (LF: Supine to Lateral position, from 673 ± 643 ms2/Hz to 201 ± 221 ms2/Hz, P < 0.05; Supine to Lateral position with supplementary oxygen, from 617 ± 511 ms2/Hz to 288 ± 389 ms2/Hz, P < 0.05; LF/HF ratio: Supine to Lateral position, from 9.4 ± 643 to 2.9 ± 1.9, P < 0.05; Supine to Lateral position with supplementary oxygen, from 6.1 ± 3.5 to 2.3 ± 1.5, P < 0.05). Further, arterial blood oxygen saturation was higher in the lateral position than in the supine position and was higher with supplementary oxygen than without supplementary oxygen (Supine, 86.7 ± 4.3%; Lateral, 94.5 ± 0.8%; Supine + O2, 93.2 ± 4.5%; Lateral + O2, 98.2 ± 1.5%). In conclusion, the lateral position during sleep attenuated sympathetic nervous system activity and improved oxygenation in patients with concomitant CAD and SAS