A Novel Echocardiographic Method for Assessing Arterial Stiffness in Obstructive Sleep Apnea Syndrome

The predictive role of aortic propagation velocity for coronary artery disease

BACKGROUND

It is well recognized that cardio- vascular risk factors lead to histological and functional changes in aorta, and aortic stiffness is the best predictor of cardiovascular morbidity and mortality. In this study we evaluated the relation of a less evaluated echocardiographic parameter of aortic stiffness, aortic propagation velocity (APV) with the presence and severity of CAD.

METHODS

This cross sectional study was conducted from May 2015 to March 2016 in Imam Reza hospital, Mashhad, Iran. Seventy patients who were referred for elective coronary artery angiography were enrolled. Patients were divided into two sub-groups based on angiographic findings: patients with CAD (38 patients, 54.3%) and non-CAD (32 patients, 45.7%). Transthoracic echocardiography was performed using the conventional 2D and color M-Mode imaging. Aortic propagation velocity (APV), aortic strain (AS) and distensibility (AD) were measured. The presence and Severity of CAD (assessing by syntax score) and their relation with aortic stiffness indices were assessed.

RESULTS

Aortic strain (6.23 ± 1.93% versus 11.66 ± 4.86%, P < 0.0001), distensibility (2.46 ± 0.91 vs 5.57 ± 2.25 cm 2 dyn-110-3, P < 0.0001) and APV (48.63 ± 10.31 cm/sec vs 77.75 ± 9.97 cm/s, P < 0.0001) were significantly decreased in CAD group compared with non-CAD group. In our study, APV showed significant inverse relationship with CAD. Based on our results, APV less than 56 cm/sec could be used to predict CAD with sensitivity and specificity of 96.9 and 78.9% respectively. We also found an inverse correlation between APV and severity of CAD.

CONCLUSION

Aortic strain, AD and APV (a less evaluated echocardiographic index) showed significant inverse correlation with presence and severity of CAD.

Aortic propagation velocity does not correlate with classical aortic stiffness parameters in healthy individuals

Objective:

Aortic stiffness is an important cardiovascular risk marker, which can be determined using different noninvasive techniques. Aortic propagation velocity (APV) has recently been established as a novel echocardiographic parameter of aortic stiffness. This study aimed to investigate the association between APV and the classical echocardiography-derived aortic stiffness parameters, aortic distensibility (AD) and aortic strain (AS), in a group of otherwise healthy individuals.

Methods:

In total, 97 consecutive healthy subjects were recruited in this observational study. APV was measured using color M-mode echocardiography from the suprasternal window in the descending aorta. AS and AD were calculated using clinical blood pressure and the M-mode echocardiography-derived aortic diameters. Correlation analyses were performed between cardiovascular risk factors related to increased aortic stiffness (age, obesity, and blood pressure) and measured stiffness parameters (APV, AS, and AD). Correlation analyses were also performed among the measured stiffness parameters.

Results:

Good correlation of age, blood pressure, and BMI with AS and AD was observed. One-on-one correlation of age, blood pressure, and BMI with APV was not observed. No correlation was observed between APV and AS (r=–0.05, p=0.6) or between APV and AD (r=–0.17, p=0.8).

Conclusion:

Although APV has been proposed as a novel and practical echocardiographic parameter of aortic stiffness, especially in patients with coronary artery disease, correlations between classical stiffness parameters (AS and AD) and APV were absent in healthy individuals at low–intermediate risk. The clinical and research applicability of APV should be further evaluated.

Patients with Obstructive Sleep Apnea Display Decreased Flow-Mediated Dilatation: Evidence from a Meta-Analysis

Background

Endothelial dysfunction, which can be measured by flow-mediated dilatation (FMD), is an early clinical marker of atherosclerosis, which is considered to be the main cause of the observed cardiovascular complications in obstructive sleep apnea (OSA) patients. The association between OSA and endothelial dysfunction has been reported in a number of studies; however, the findings are not entirely consistent. Our aim was to meta-analytically synthesize the existing evidence to explore the association between OSA and endothelial dysfunction.

Material/Methods

Data from PubMed, EMBASE, the Cochrane library, and Google Scholar for all trials that investigated the relationship between endothelial dysfunction and OSA were systematically reviewed. The minimum inclusion criteria for the studies were reporting of the Apnea-Hypopnea Index (AHI) and FMD measurements (as an indicator of endothelial dysfunction) for both OSA and control groups. Data from case-control studies that met the inclusion criteria were extracted.

Results

Twenty-eight studies comprising a total of 1496 OSA patients and 1135 controls were included in the meta-analysis. A random-effects model was used. The weighted mean difference in the FMD measurements was −3.07 and the 95% confidence interval was −3.71 to −2.43 (P<0.01). Meta-regression analysis showed that age, sex, body mass index (BMI), blood pressure, glucose, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol did not explain the heterogeneity.

Conclusions

This meta-analysis showed that patients with OSA have decreased FMD, which may contribute to the development of atherosclerosis.

The Association Between Obstructive Sleep Apnea and Carotid Intima-Media Thickness: A Systematic Review and Meta-Analysis

Obstructive sleep apnea (OSA) has been suggested as a risk factor for carotid atherosclerosis. The present meta-analysis aimed to evaluate the association between OSA and carotid intima-media thickness (CIMT). Eighteen studies comparing CIMT of patients with OSA versus non-OSA patients were included. Quantitative data synthesis was used to pool weighted standardized difference in means (SMD) of CIMT in a random-effects model. Compared to healthy controls, patients with OSA had a significantly higher CIMT (SMD: 0.881; 95% confidence interval [CI]: 0.647-1.115; P < .001). Due to the great heterogeneity, a subgroup analysis was conducted based on the study design. The pooled SMD of CIMT between patients with OSA and healthy controls were 0.810 (95% CI: 0.676-0.943; P < .001) and 1.008 (95% CI: 0.506-1.510; P < .001) in matched and unmatched group, respectively. Moreover, the correlation of apnea-hypopnea index and CIMT was moderate ( r = .389; 95% CI: 0.315-0.459; P < .001). After adjustment for several major confounders, OSA is an independent risk factor for CIMT. These findings remind clinicians to screen for cardiovascular diseases in patients with OSA.

Vascular Aging: Lessons From Pediatric Hypertension

Hypertension (HTN) in children is associated with early vascular aging (EVA) and underlying immunologic-metabolic abnormalities and accelerated biological maturation. Morphologic and functional vascular changes underlying EVA and HTN in children resemble those seen in the elderly including but not limited to an increase in intima-media thickness (IMT) and arterial stiffness and endothelial dysfunction. Although progeria syndrome leading to EVA and the development of clinically manifested cardiovascular (CV) disease in the second decade of life is a rare hereditary disorder, primary HTN, which is also associated with EVA, is much more common (reported in up to 10% in adolescents). EVA associated with HTN in children leads to the premature development of target organ injury in childhood and CV events in early adulthood. Limited evidence from prospective observational studies in children and adolescents indicates that early lifestyle measures (low salt/low sugar intake and exercise) or pharmacologic treatment of HTN, or both, partially reverses morphologic and functional changes underlying EVA such as an increase in carotid IMT and pulse wave velocity, a decrease in flow-mediated dilation of the brachial artery, and an increase in oxidative stress and visceral fat. Future mechanistic and therapeutic clinical trials are desirable to assess the mechanisms and treatment strategies of EVA in the context of HTN in children and their effect on CV events in early adulthood.