Cardiac hypertrophy in obstructive sleep apnea syndrome

Morbid obesity influences the nocturnal electrocardiogram wave and interval durations among suspected sleep apnea patients

BACKGROUND

Obesity is a global issue with a major impact on cardiovascular health. This study explores how obesity influences nocturnal cardiac electrophysiology in suspected obstructive sleep apnea (OSA) patients.

METHODS

We randomly selected 12 patients from each of the five World Health Organization body mass index (BMI) classifications groups (ntotal  = 60) while keeping the group's age and sex matched. We evaluated 1965 nocturnal electrocardiography (ECG) samples (10 s) using modified lead II recorded during normal saturation conditions. R-wave peaks were detected and confirmed using dedicated software, with the exclusion of ventricular extrasystoles and artifacts. The duration of waves and intervals was manually marked. The average electric potential graphs were computed for each segment. Thresholds for abnormal ECG waveforms were P-wave > 120 ms, PQ interval > 200 ms, QRS complex > 120 ms for, and QTc > 440 ms.

RESULTS

Obesity was significantly (p < .05) associated with prolonged conduction times. Compared to the normal weight (18.5 ≤ BMI < 25) group, the morbidly obese patients (BMI ≥ 40) had a significantly longer P-wave duration (101.7 vs. 117.2 ms), PQ interval (175.8 vs. 198.0 ms), QRS interval (89.9 vs. 97.7 ms), and QTc interval (402.8 vs. 421.2 ms). We further examined ECG waveform prolongations related to BMI. Compared to other patient groups, the morbidly obese patients had the highest number of ECG segments with PQ interval (44% of the ECG samples), QRS duration (14%), and QTc duration (20%) above the normal limits.

CONCLUSIONS

Morbid obesity predisposes patients to prolongation of cardiac conduction times. This might increase the risk of arrhythmias, stroke, and even sudden cardiac death.

The impact of the Adenotonsillectomy on cardiac functions and oxidative stress

OBJECTIVE

Obstructive sleep apnea syndrome (OSAS) causes cardiovascular comorbidities and increased oxidative stress. Adenotonsillectomy is the first treatment option for OSAS secondary to adenotonsillar hypertrophy (ATH). This study evaluated the presence of cardiovascular changes, hypertension and oxidative stress before and after adenotonsillectomy in patients with OSAS secondary to ATH.

METHODS

Patients with ATH diagnosed with OSAS by polysomnography (PSG) were included. All participants received an Echocardiography (ECHO) and 24-h ambulatory blood pressure measurement (ABPM). Serum malonyldialdehyde (MDA) and total oxidant activity (TOS) levels of oxidant parameters; total antioxidant activity (TAS), catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) levels of antioxidant parameters were measured. All patients received an adenotonsillectomy. Postoperative evaluation was performed at the 6th month. In the postoperative period, PSG, ECHO, ABPM and the oxidant-antioxidant parameter levels in the serum was repeated.

RESULTS

Twenty-eight patients (13 males, 15 females; mean age 8.2 ± 2.06 years) were included in the study. In the preoperative period, concentric remodeling was observed in 14,8% of the patients, although they had no cardiovascular system complaints. The apnea-hypopnea index (AHI) scores were classified as mild in 39.3% (n = 11), moderate in 21.4% (n = 6) and severe in 39.3% (n = 11) preoperatively. In the postoperative period, 22 patients were evaluated. It was observed that the severity of OSAS decreased, ventricular functions improved, oxidant parameters decreased and antioxidant parameters increased postoperatively.

CONCLUSION

Adenotonsillectomy provides a positive change in cardiovascular system parameters and an antioxidant change in the oxidative balance in patients with OSAS.

Intermittent hypoxia changes the interaction of the kinin-VEGF system and impairs myocardial angiogenesis in the hypertrophic heart

Intermittent hypoxia (IH) is a feature of obstructive sleep apnea (OSA), a condition highly associated with hypertension-related cardiovascular diseases. Repeated episodes of IH contribute to imbalance of angiogenic growth factors in the hypertrophic heart, which is key in the progression of cardiovascular complications. In particular, the interaction between vascular endothelial growth factor (VEGF) and the kallikrein-kinin system (KKS) is essential for promoting angiogenesis. However, researchers have yet to investigate experimental models of IH that reproduce OSA, myocardial angiogenesis, and expression of KKS components. We examined temporal changes in cardiac angiogenesis in a mouse IH model. Adult male C57BI/6 J mice were implanted with Matrigel plugs and subjected to IH for 1-5 weeks with subsequent weekly histological evaluation of vascularization. Expression of VEGF and KKS components was also evaluated. After 3 weeks, in vivo myocardial angiogenesis and capillary density were decreased, accompanied by a late increase of VEGF and its type 2 receptor. Furthermore, IH increased left ventricular myocardium expression of the B2 bradykinin receptor, while reducing mRNA levels of B1 receptor. These results suggest that in IH, an unexpected response of the VEGF and KKS systems could explain the reduced capillary density and impaired angiogenesis in the hypoxic heart, with potential implications in hypertrophic heart malfunction.

Canonical Pathways Associated with Blood Pressure Response to Sleep Apnea Treatment: A Post Hoc Analysis

BACKGROUND

Several studies have reported an association between microRNAs (miRNAs) and hypertension or cardiovascular disease (CVD). In a previous study performed on a group of 38 patients, we observed a cluster of 3 miRNAs (miR-378a-3p, miR-100-5p, and miR-486-5p) that were functionally associated with the cardiovascular system that predicted a favorable blood pressure (BP) response to continuous positive airway pressure (CPAP) treatment in patients with resistant hypertension (RH) and obstructive sleep apnea (OSA) (HIPARCO score). However, little is known regarding the molecular mechanisms underlying this phenomenon.

OBJECTIVES

The aim of the study was to perform a post hoc analysis to investigate the genes, functions, and pathways related to the previously found HIPARCO score miRNAs.

METHODS

We performed an enrichment analysis using Ingenuity pathway analysis. The genes potentially associated with the miRNAs were filtered based on their confidence level. Particularly for CVD, only the genes regulated by at least 2 of the miRNAs were studied.

RESULTS

We observed that the miRNAs studied regulate 200-249 molecules associated with several functions and diseases, including extracranial solid tumors and abdominal neoplasms, among others. The cardiac hypertrophy and NF-kB signaling pathways were identified as the cardiovascular pathways most influenced by these 3 miRNAs.

CONCLUSIONS

The mechanisms by which CPAP treatment decreases the BP in OSA patients with RH could be related to the cardiac hypertrophy and NF-kB signaling pathways. Further investigations will be necessary to confirm these findings, contributing to the elucidation of new therapeutic targets in patients who do not respond to CPAP treatment.

Clinical Characteristics of Hypertensive Patients with Obstructive Sleep Apnoea Syndrome Developing Different Types of Left Ventricular Geometry

Objective

The objective of the study was to compare polygraphic parameters and selected laboratory parameters in patients with obstructive sleep apnoea (OSA) who develop various types of left ventricular (LV) geometry. Material and Methods. The research covered 122 patients with obstructive sleep apnoea and coexisting effectively treated systemic hypertension (95 men, 27 women, average age: 54 ± 10.63). Overnight polygraphy, echocardiography, carotid artery ultrasonography, and laboratory measurements were performed. The patients were classified into four groups, depending on LV geometry. Group 1 comprised patients with normal LV geometry, group 2 included those with LV concentric remodelling. Group 3 and group 4 were patients with LV hypertrophy, concentric or eccentric, respectively.

Results

The most frequent type of LV geometry in the examined population was eccentric hypertrophy (36%). The highest average values of BMI and T-Ch were observed in the group of patients with concentric remodelling (group 2). The most severe respiratory disorders were found in the group of patients developing LV concentric hypertrophy (group 3); however, these differences were not statistically significant in comparison to other groups. Patients with LV eccentric hypertrophy had significantly decreased LV ejection fraction (p = 0.0008).

Conclusions

LV eccentric hypertrophy is the most frequent type of LV geometry in OSA patients. Patients with severe sleep-disordered breathing are more likely to develop concentric hypertrophy, while concentric remodelling occurs more frequently among OSA patients with other coexisting conditions, such as obesity or lipid-related disorders.

Effect of Obstructive Sleep Apnea and Positive Airway Pressure Therapy on Cardiac Remodeling as Assessed by Cardiac Biomarker and Magnetic Resonance Imaging in Nonobese and Obese Adults

It is unknown whether obesity modifies the effect of obstructive sleep apnea (OSA) and positive airway pressure (PAP) therapy on cardiac remodeling and NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels. We compared NT-proBNP and cardiac magnetic resonance imaging in adults without OSA (n=56) and nonobese (n=73; body mass index <30 kg/m²) and obese (n=136; body mass index ≥30 kg/m²) adults with OSA. We also investigated these traits in nonobese (n=45) and obese (n=78) participants with OSA adherent to 4 months of PAP treatment. At baseline, left ventricular mass to end-diastolic volume ratio, a measure of left ventricular concentricity, was greater in both nonobese and obese participants with OSA compared with those without OSA. Participants with OSA and obesity exhibited reduced phasic right atrial function. No significant differences in baseline NT-proBNP were observed across groups. The effect of PAP treatment on NT-proBNP and left atrial volume index was significantly modified by obesity. In nonobese participants, PAP therapy was associated with a decrease in NT-proBNP (P<0.0001) without a change in left atrial volume index, whereas in obese participants, PAP was associated with an increase in left atrial volume index (P=0.006) without a change in NT-proBNP. OSA was associated with left ventricular concentric remodeling independent of obesity and right atrial dysfunction in participants who were obese. PAP treatment was associated with reduced NT-proBNP in nonobese participants with OSA, but left atrial enlargement in obese participants with OSA, suggesting that PAP-induced reduction in BNP release (which is known to occur during obstructive apnea episodes) may lead to volume retention in obese participants with OSA. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01578031.

The Relationship between Obstructive Sleep Apnea and Alzheimer's Disease

Obstructive sleep apnea (OSA) and Alzheimer's disease (AD) are highly prevalent conditions with growing impact on our aging society. While the causes of OSA are now better characterized, the mechanisms underlying AD are still largely unknown, challenging the development of effective treatments. Cognitive impairment, especially affecting attention and executive functions, is a recognized clinical consequence of OSA. A deeper contribution of OSA to AD pathogenesis is now gaining support from several lines of research. OSA is intrinsically associated with disruptions of sleep architecture, intermittent hypoxia and oxidative stress, intrathoracic and hemodynamic changes as well as cardiovascular comorbidities. All of these could increase the risk for AD, rendering OSA as a potential modifiable target for AD prevention. Evidence supporting the relevance of each of these mechanisms for AD risk, as well as a possible effect of AD in OSA expression, will be explored in this review.

The association of sleep disordered breathing with left ventricular remodeling in CAD patients: a cross-sectional study

Background

There is still insufficient knowledge on the potential effect of mild to moderate sleep-disordered breathing (SDB) that is widely prevalent, often asymptomatic, and largely undiagnosed in patients with stable coronary artery disease (CAD). SDB affects 34% of men and 17% of women aged between 30 and 70. The objective of this study was to evaluate the association between SDB and left ventricular (LV) hypertrophy as well as structural remodeling in stable CAD patients.

Methods

The study was based on a cross-sectional design. Echocardiography and polysomnography was performed in 772 patients with CAD and with untreated sleep apnea. All study participants underwent testing by Epworth Sleepiness Scale questionnaire. Their mean age, NYHA and left ventricular ejection fraction were, respectively: 57 ± 9 years, 2.1 ± 0.5 and 51 ± 8%, and 76% were men. Sleep apnea (SA) was defined as an apnea-hypopnea-index (AHI) ≥5 events/h, and, non-SA, as an AHI <5.

Results

Sleep apnea was present in 39% of patients, and a large fraction of those patients had no complaints on excessive daytime sleepiness. The patients with SA were older, with higher body mass and higher prevalence of hypertension. LV hypertrophy (LVH), defined by allometrically corrected (LV mass/height^2.7) gender-independent criteria, was more common among the patients with SA than those without (86% vs. 74%, p < 0.001). The frequency of LVH by wall thickness criteria (interventricular septal thickness or posterior wall thickness ≥ 12 mm: 49% vs. 33%, p < 0.001) and concentric LVH (61% vs. 47%, p = 0.001) was higher in CAD patients with SA. The patients with SA had significantly higher values of both interventricular septal thickness and posterior wall thickness. Multiple logistic regression analysis showed that even mild sleep apnea was an independent predictor for LVH by wall thickness criteria and concentric LVH (OR = 1.5; 95% CI 1.04–2.2 and OR = 1.9; 1.3–2.9 respectively).

Conclusions

We concluded that unrecognized sleep apnea was highly prevalent among patients with stable CAD, and the majority of those patients did not report daytime sleepiness. Mild to moderate sleep apnea was associated with increased LV wall thickness, LV mass, and with higher prevalence of concentric LV hypertrophy independently of coexisting obesity, hypertension, diabetes mellitus or advancing age.

Right Ventricular Structure and Function Are Associated With Incident Atrial Fibrillation: MESA-RV Study (Multi-Ethnic Study of Atherosclerosis-Right Ventricle)

BACKGROUND

Right ventricular (RV) morphology has been associated with drivers of atrial fibrillation (AF) risk, including left ventricular and pulmonary pathology, systemic inflammation, and neurohormonal activation. The aim of this study was to investigate the association between RV morphology and risk of incident AF.

METHODS AND RESULTS

We interpreted cardiac magnetic resonance imaging in 4204 participants free of clinical cardiovascular disease in the MESA (Multi-Ethnic Study of Atherosclerosis). Incident AF was determined using hospital discharge records, study electrocardiograms, and Medicare claims data. The study sample (n=3819) was 61±10 years old and 47% male with 47.2% current/former smokers. After adjustment for demographics and clinical factors, including incident heart failure, higher RV ejection fraction (hazard ratio, 1.16 per SD; 95% confidence interval, 1.03-1.32; P=0.02) and greater RV mass (hazard ratio, 1.25 per SD; 95% confidence interval, 1.08-1.44; P=0.002) were significantly associated with incident AF. After additional adjustment for the respective left ventricular parameter, higher RV ejection fraction remained significantly associated with incident AF (hazard ratio, 1.15 per SD; 95% confidence interval, 1.01-1.32; P=0.04), whereas the association was attenuated for RV mass (hazard ratio, 1.16 per SD; 95% confidence interval, 0.99-1.35; P=0.07). In a subset of patients with available spirometry (n=2540), higher RV ejection fraction and mass remained significantly associated with incident AF after additional adjustment for lung function (P=0.02 for both).

CONCLUSIONS

Higher RV ejection fraction and greater RV mass were associated with an increased risk of AF in a multiethnic population free of clinical cardiovascular disease at baseline.

Factors Contributing to Development and Reversal of LVH: A Pilot Study

INTRODUCTION

Left Ventricular Hypertrophy (LVH) often reflects as a physiological adaptation to chronic pressure overload. It has been identified as a strong independent risk factor of all-cause mortality and adverse cardiac events. Since not all subjects with hypertension develop LVH, understanding the clinical factors contributing to the development of LVH and the appropriate diagnostic and treatment strategies may help clinicians in conducting more definitive evaluation and managing the disease effectively.

AIM

To assess the incidence of LVH in hypertensive subjects and the factors influencing its development and reversal. The study also evaluated the most effective diagnostic technique and therapy that could improve the disease symptoms and prognosis.

MATERIALS AND METHODS

The prospective study, conducted at Jagadguru Sri Shivarathreeshwara (JSS) Medical College JSS University, Mysore, India, included 50 patients with hypertension. Detailed history of the recruited subjects was collected from patient records and through physical examination. Demographic and clinical characteristics such as age, gender, BMI, and stage of hypertension (stage I HTN and stage II HTN) were also obtained. Funduscopic examination was done for all patients for evidence of hypertensive retinopathy. Echocardiography (ECHO), electrocardiography (ECG), and chest X-Ray were used for detection of LVH. The patients were reviewed after six months and reassessment of LVH was carried out. Statistical analysis was conducted using SPSS software and R 3.2 package.

RESULTS

Angiotensin-Converting Enzyme (ACE) inhibitors were found to be more effective in the treatment of LVH when compared to calcium channel blockers and beta blockers. ECHO was found to be the best method to diagnose LVH. In patients with stage I HTN, 47.1% had normal LVM. Around 53% of the subjects with stage I HTN and all with stage II HTN had abnormal LVM. Retinal changes were noted in 96.2% of abnormal LVM patients and 50% of normal LVM patients. A positive association between BMI and LVH (OR: 1.39) was also noted.

CONCLUSION

BMI may positively influence LVH regression. The presence of retinopathy, in addition to LVH, suggests an increased chance of regression with anti-hypertensive treatment.

Chronic intermittent hypoxia induces cardiac hypertrophy by impairing autophagy through the adenosine 5'-monophosphate-activated protein kinase pathway

Autophagy is tightly regulated to maintain cardiac homeostasis. Impaired autophagy is closely associated with pathological cardiac hypertrophy. However, the relationship between autophagy and cardiac hypertrophy induced by chronic intermittent hypoxia (CIH) is not known. In the present study, we measured autophagy-related genes and autophagosomes during 10 weeks of CIH in rats, and 6 days in H9C2 cardiomyocytes, and showed that autophagy was impaired. This conclusion was confirmed by the autophagy flux assay. We detected significant hypertrophic changes in myocardium with impaired autophagy. Rapamycin, an autophagy enhancer, attenuated the cardiac hypertrophy induced by CIH. Moreover, silencing autophagy-related gene 5 (ATG5) exerted the opposite effect. The role of adenosine monophosphate-activated protein kinase (AMPK) in regulating autophagy under CIH was confirmed using AICAR to upregulate this enzyme and restore autophagy flux. Restoring autophagy by AICAR or rapamycin significantly reversed the hypertrophic changes in cardiomyocytes. To investigate the mechanism of autophagy impairment, we compared phospho (p)-AMPK, p-Akt, cathepsin D, and NFAT3 levels, along with calcineurin activity, between sham and CIH groups. CIH activated calcineurin, and inhibited AMPK and AMPK-mediated autophagy in an Akt- and NFAT3-independent manner. Collectively, these data demonstrated that impaired autophagy induced by CIH through the AMPK pathway contributed to cardiac hypertrophy.

Carotid Body Ablation Abrogates Hypertension and Autonomic Alterations Induced by Intermittent Hypoxia in Rats

Chronic intermittent hypoxia (CIH), the main feature of obstructive sleep apnea, enhances carotid body (CB) chemosensory responses to hypoxia and produces autonomic dysfunction, cardiac arrhythmias, and hypertension. We tested whether autonomic alterations, arrhythmogenesis, and the progression of hypertension induced by CIH depend on the enhanced CB chemosensory drive, by ablation of the CB chemoreceptors. Male Sprague-Dawley rats were exposed to control (Sham) conditions for 7 days and then to CIH (5% O2, 12/h 8 h/d) for a total of 28 days. At 21 days of CIH exposure, rats underwent bilateral CB ablation and then exposed to CIH for 7 additional days. Arterial blood pressure and ventilatory chemoreflex response to hypoxia were measured in conscious rats. In addition, cardiac autonomic imbalance, cardiac baroreflex gain, and arrhythmia score were assessed during the length of the experiments. In separate experimental series, we measured extracellular matrix remodeling content in cardiac atrial tissue and systemic oxidative stress. CIH induced hypertension, enhanced ventilatory response to hypoxia, induced autonomic imbalance toward sympathetic preponderance, reduced baroreflex gain, and increased arrhythmias and atrial fibrosis. CB ablation normalized blood pressure, reduced ventilatory response to hypoxia, and restored cardiac autonomic and baroreflex function. In addition, CB ablation reduced the number of arrhythmias, but not extracellular matrix remodeling or systemic oxidative stress, suggesting that reductions in arrhythmia incidence during CIH were related to normalization of cardiac autonomic balance. Present results show that autonomic alterations induced by CIH are critically dependent on the CB and support a main role for the CB in the CIH-induced hypertension.

Association between Obstructive Sleep Apnea and Left Ventricular Structure by Age and Gender: the Multi-Ethnic Study of Atherosclerosis

STUDY OBJECTIVES

The presence and severity of obstructive sleep apnea (OSA) are associated with impaired left ventricular (LV) structure and function. Our goal was to quantify the associations between LV systolic function and mass with severity of OSA in an ethnically diverse cohort, assessing variations by age and sex.

METHODS

We conducted a cross-sectional analysis of data from 1,412 racially/ethnically diverse participants across 6 US communities from the Multi-Ethnic Study of Atherosclerosis who underwent both overnight polysomnography and cardiac magnetic resonance imaging from 2010-2012. We evaluated the association between the obstructive apnea-hypopnea index (AHI) by clinical category (< 5, 5-15, 15-30, 30-50, > 50) and secondary measures of sleep apnea with the outcomes left ventricular (LV) mass adjusted for height, LV mass/volume ratio, and LV ejection fraction.

RESULTS

After adjusting for potential confounders and mediators, LV mass was significantly increased with increasing AHI category for subjects age 65 y or younger (β = 1.84 ± 0.47 g/m, P = 0.0001). The association between the AHI and LV mass appeared stronger in whites and Chinese compared to blacks and Hispanics, although interaction terms were not statistically significant. Additionally, while both LV mass and LV mass/volume ratio were significantly associated with hypoxia, ejection fraction was not associated with any OSA severity index. Comparable associations were observed in men and women.

CONCLUSIONS

Independent of confounders, higher levels of AHI are significantly associated with increased LV mass in both men and women younger than 65 y from a community-based cohort.

Use of Ambulatory Blood Pressure Monitoring for the Screening of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a frequent and underdiagnosed disease in hypertensive individuals who experience cardiovascular events. The aim of this study was to define the best model that combined the ambulatory blood pressure (BP) monitoring (ABPM), anthropometric, sociodemographic, and biological variables to identify moderate to severe OSA. A total of 105 ABPM-confirmed hypertensive patients were evaluated using their clinical histories, blood analyses, ABPM, and home respiratory polygraphic results. A multivariate logistic regression analysis was performed to identify the significant variables. The best model included sex, presence of obesity (body mass index ≥30 kg/m(2) and abdominal obesity), mean daytime BP, mean nocturnal heart rate, and minimal diastolic nighttime BP to achieve an area under the curve of 0.804. Based on this model, a validated scoring system was developed to identify the patients with an apnea-hypopnea index ≥15. Therefore, in untreated hypertensive patients who snored, ABPM variables might be used to identify patients at risk for OSA.

Left ventricular diastolic dysfunction in obstructive sleep apnoea syndrome by an echocardiographic standardized approach: An observational study

BACKGROUND

The association between obstructive sleep apnoea syndrome (OSAS), left ventricular (LV) diastolic dysfunction and LV geometry remains controversial because of coexisting disorders.

AIMS

To evaluate LV diastolic dysfunction and its independent predictors in a real-life cohort of OSAS patients, by a standardized approach.

METHODS

We consecutively included 188 OSAS patients after an overnight polysomnography to undergo clinical evaluation, ambulatory blood pressure measurement and complete echocardiography, combining M-mode, two-dimensional Doppler and tissue Doppler imaging modes. Correlations between OSAS severity and clinical and echocardiographical variables were assessed, and logistic regression models were used to identify possible determining factors of LV diastolic dysfunction.

RESULTS

Most patients were hypertensive (n=148, 78.7%) and already receiving treatment by continuous positive airway pressure (n=158, 84.5%). The prevalence of LV hypertrophy, defined by LV mass index (LVMi) normalized by height (2.7), was 12.4%, with a significant correlation with hypertension (P=0.004). The apnoea-hypopnoea index was correlated with body mass index (P<0.0001), 24-hour systolic blood pressure (P=0.01) and LVMi normalized by height (2.7) (P=0.03). Diastolic function assessed by a global approach was impaired for 70 patients (37.2%) and none of the OSAS severity variables was a determining factor after multivariable analysis with adjustment for age and sex.

CONCLUSION

Diastolic dysfunction assessed by a standardized approach is common in OSAS and should be routinely evaluated; it is independently predicted by none of the respiratory severity variables.

Obesity and atrial fibrillation: A comprehensive review of the pathophysiological mechanisms and links

Obesity is a worldwide health problem with epidemic proportions that has been associated with atrial fibrillation (AF). Even though the underlying pathophysiological mechanisms have not been completely elucidated, several experimental and clinical studies implicate obesity in the initiation and perpetuation of AF. Of note, hypertension, diabetes mellitus, metabolic syndrome, coronary artery disease, and obstructive sleep apnea, represent clinical correlates between obesity and AF. In addition, ventricular adaptation, diastolic dysfunction, and epicardial adipose tissue appear to be implicated in atrial electrical and structural remodeling, thereby promoting the arrhythmia in obese subjects. The present article provides a concise overview of the association between obesity and AF, and highlights the underlying pathophysiological mechanisms.

Association of electrocardiographic left ventricular hypertrophy with incident cardiovascular disease in Japanese older hypertensive patients

BACKGROUND

Our aim was to assess whether electrocardiographic left ventricular hypertrophy (ECG-LVH) is associated with a higher risk of cardiovascular disease (CVD) events, independent of 24-hour blood pressure (BP) and circulating levels of norepinephrine and hemostatic factors.

METHODS

In 514 older hypertensive patients (mean age 72.3 years; 37% men), we assessed ambulatory BP values, circulating levels of norepinephrine and hemostatic factors (plasma fibrinogen, prothrombin fragment 1+2 (F1+2), von Willebrand factor (vWF), and plasminogen activator inhibitor-1 (PAI-1)), and the presence or absence of ECG-LVH (Sokolow-Lyon voltage ≥ 3.5 mV). The incidence of CVD events (i.e., myocardial infarction and stroke) was prospectively ascertained.

RESULTS

During an average 41 months of follow-up (1,751 person-years), 43 stroke and 3 myocardial infarction events occurred. At baseline, patients with ECG-LVH had higher mean 24-hour BP (148.8/83.8mm Hg vs. 135.7/77.2mm Hg) and circulating norepinephrine levels (404.6 pg/ml vs. 336.3 pg/ml) compared to those without ECG-LVH; the differences remained unchanged after adjustment for age, gender, smoking status, presence of diabetes, and antihypertensive medication uses at follow-up time (all P < 0.01). Cox proportional hazards models suggested that the hazard ratio (HR; 95% confidence interval (CI)) of CVD events for those with ECG-LVH was 4.4 (2.3-8.2), and the association between ECG-LVH and incident CVD events remained significant after adjustment for high 24-hour BP (≥130/80mm Hg), nocturnal SBP, circulating norepinephrine and fibrinogen levels (HRs, 3.5-4.2, all P < 0.001).

CONCLUSIONS

In older hypertensive patients, ECG-LVH was associated with a higher risk of CVD events, independent of ambulatory BP parameters and circulating norepinephrine and fibrinogen levels.

Diastolic dysfunction in controlled hypertensive patients with mild-moderate obstructive sleep apnea

BACKGROUND

Hypertension and severe obstructive sleep apnea (OSA) may independently contribute to left ventricular diastolic dysfunction. However, scanty data is available on this issue in hypertensives with mild-moderate OSA.

METHODS AND RESULTS

We performed polysomnography, echocardiography and 24h ambulatory blood pressure monitoring in 115 treated essential hypertensives with suspicion of OSA. After exclusion of severe/treated OSA and/or cardiovascular disease patients, mild-moderate OSA (5 ≤ apnoea/hypopnoea index<30 events·h(-1)) was diagnosed in 47.3% of the remaining 91 patients, while 52.7% were free of OSA. Transmitral early (E) and late (A) peak flow velocities were assessed in 69 patients, and mitral annular velocity (E') in 53. Compared to non-OSA, mild-moderate OSA heart rate was higher (p=0.031) while E/A was lower (p<0.001) without differences in 24h mean systolic and diastolic blood pressures (125.36 ± 12.46/76.46 ± 6.97 vs 128.63 ± 11.50/77.70 ± 7.72 mmHg, respectively, NS). Patients with E'< 10 cm/s and E/A<0.8 showed a lower mean SpO2 than subjects with normal diastolic function (p=0.004; p<0.001). In a logistic regression model age, mean SpO2, daytime heart rate and nocturnal diastolic blood pressure fall were associated with altered relaxation pattern, independently from BMI and gender.

CONCLUSIONS

In controlled hypertensives mild-moderate OSA may be associated with early diastolic dysfunction, independently from age, gender and mean blood pressure and in the absence of concentric left ventricular hypertrophy. Moreover nocturnal hypoxia may be a key factor in determining early diastolic dysfunction, under the synergic effects of hypertension and mild-moderate OSA.

Independent association of obstructive sleep apnea with left ventricular geometry and systolic function in resistant hypertension: the RESIST-POL study

OBJECTIVE

We investigated the impact of obstructive sleep apnea (OSA) and night blood pressure (BP) on left ventricular geometry and systolic function in patients with resistant hypertension (RHTN).

METHODS AND RESULTS

Data from 155 patients with RHTN were analyzed. All patients underwent biochemical evaluations, ambulatory blood pressure monitoring (ABPM), and polysomnography. Left ventricular mass index (LVMI), relative wall thickness (RWT), left ventricular ejection fraction (LVEF), midwall fractional shortening (mwFS) and global longitudinal strain (GLS) were measured. Patients were divided into four groups based on the presence of metabolic syndrome (MS) and OSA: group 1: OSA(-), MS(-) [n = 42]; group 2: OSA(+), MS(-) [n = 14]; group 3: OSA(-), MS(+) [n = 46]; and group 4: OSA(+), MS(+) [n = 53]. In group 3 and 4 concentric geometry was present in 53.2% and 79.6% respectively (P = 0.004). There were no differences in LVEF between groups. Group 3 and 4 had lower mwFS as compared with group 1 (16.40 ± 1.9 and 15.38 ± 2.2 vs 17.44 ± 1.9; P < 0.049 and P < 0.0001 respectively). Group 4 had significantly lower GLS as compared with group 1 (-12.64 ± 3.3 vs -15.59 ± 4.0; P < 0.001). In the multivariable analysis, factors independently associated with concentric geometry were age, nighttime SBP (OR -1.04; 95%Cl 1.019-1.082; P < 0.0001) and OSA (OR -3.97; 95%Cl 1.835-8.590; P < 0.0001). In the other multivariable analysis, factors independently associated with GLS were OSA (beta = 0.279; P = 0.001), and nighttime DBP (beta = 0.168; P = 0.048) whereas factors independently associated with mwFS were age, gender, nighttime SBP, concentric geometry, and metabolic syndrome.

CONCLUSIONS

In patients with true RHTN without diabetes concentric geometry and systolic dysfunction are independently associated with moderate and severe OSA and nighttime BP levels.

Relationship between obstructive sleep apnea and markers of cardiovascular alterations in never-treated hypertensive patients

We addressed a question if there is a relationship between severity of newly diagnosed obstructive sleep apnea (OSA) and markers of cardiovascular alterations in middle-aged untreated hypertensive patients. In 121 consecutive patients with never-treated essential hypertension (mean age 35.9±10.1 years; 97 men and 24 women) evaluation of office and ambulatory blood pressure (BP) measurements, metabolic syndrome (MS) components and markers of alterations in cardiovascular system including left ventricular structure and function, carotid artery wall intima-media thickness (cIMT) and urinary albumin excretion (UAE) was performed. OSA was classified as mild (apnea/hypopnea index (AHI) 5-15 events h(-1)) or moderate-to-severe (AHI >15 events h(-1)). Mild and moderate-to-severe OSA were diagnosed in 30% and 20% of patients, respectively. No differences in nighttime BP levels and decline between patients with and without OSA were observed. The patients with moderate-to-severe OSA were characterized by higher cIMT (0.74±0.16 vs. 0.60±0.15 mm; P=0.001), UAE (14.5±6.9 vs. 10.0±8.0 mg 24 h(-1); P=0.014), relative wall thickness (0.42±0.05 vs. 0.39±0.05; P=0.023) and by a higher degree of diastolic dysfunction (E'-wave velocity 11.4±3.2 vs. 15.5±3.8 m s(-1); P<0.001) as compared with the patients without OSA. In multivariate analysis, AHI independently of BP and MS components correlated with UAE, relative wall thickness and E'-wave velocity. In the middle-aged never-treated hypertensive patients, moderate-to-severe OSA correlates with markers of cardiovascular alterations independently of BP levels and MS components.

Obstructive sleep apnea severity is associated with left ventricular mass independent of other cardiovascular risk factors in morbid obesity

OBJECTIVE

To evaluate the relation between obstructive sleep apnea (OSA) and left ventricular mass (LVM) in morbid obesity and the influence of gender, menopausal status, anthropometry, body composition, hypertension, and other cardiovascular risk factors in this relationship.

DESIGN

Cross-sectional descriptive study.

METHODS

Polysomnographic and echocardiographic studies were performed in a cohort of 242 patients (86 men, 100 premenopausal (PreM) and 56 postmenopausal (PostM) women), with grade II obesity and above (BMI: 43.7 ± 0.4 kg/m(2)) to investigate OSA and LVM respectively. Anthropometry, body composition, glucose tolerance, and blood pressure were also recorded.

RESULTS

OSA to different degrees was diagnosed in 76.2% of the patients (n: 166), its prevalence being 90.9% (n: 70) for men, and 76% (n: 38) and 63.8% (n: 58) for PostM and PreM women, respectively (p < 0.01). LVM excess was greatest for PostM women (90.2%), followed by men (81.9%) and PreM females (69.6%) (p < 0.01). LVM values increased in accordance to OSA severity (absence, 193.7 ± 6.9 g; mild, 192.6 ± 7.8 g; moderate, 240.5 ± 12.5 g; severe, 273.6 ± 14.6 g; p < 0.01). LVM magnitude correlated with the menopausal state, age, central adiposity, hypertension (HT), type 2 diabetes (DM), desaturation index (DI), and apnea-hypopnea index (AHI) (r = 0.41; p < 0.01). The relationship between LVM and AHI persisted in the multivariate analysis (β = 0.25; p < 0.05) after adjusting for age, gender, menopausal state, BMI, waist circumference, neck circumference, DI, fasting plasma glucose, DM, and HT. But if tobacco habits are included, the statistical difference disappears (β = 0.22; p = 0.06).

CONCLUSIONS

Morbid obesity is frequently associated with abnormal LVM, particularly in patients with OSA; this association is independent of HT, BMI, body composition, and other clinical factors, supporting a direct role of OSA on LVM in morbid obesity. This suggests that OSA and LVM might be taken as predictors of the cardiovascular risk in these patients.

The Relationship between Obstructive Sleep Apnea and Atrial Fibrillation: A Complex Interplay

In recent years, growing evidence suggests an association between obstructive sleep apnea (OSA), a common sleep breathing disorder which is increasing in prevalence as the obesity epidemic surges, and atrial fibrillation (AF), the most common cardiac arrhythmia. AF is a costly public health problem increasing a patient's risk of stroke, heart failure, and all-cause mortality. It remains unclear whether the association is based on mutual risk factors, such as obesity and hypertension, or whether OSA is an independent risk factor and causative in nature. This paper explores the pathophysiology of OSA which may predispose to AF, clinical implications of stroke risk in this cohort who display overlapping disease processes, and targeted treatment strategies such as continuous positive airway pressure and AF ablation.

Therapeutic strategies for sleep apnea in hypertension and heart failure

Sleep-disordered breathing (SDB) causes hypoxemia, negative intrathoracic pressure, and frequent arousal, contributing to increased cardiovascular disease mortality and morbidity. Obstructive sleep apnea syndrome (OSAS) is linked to hypertension, ischemic heart disease, and cardiac arrhythmias. Successful continuous positive airway pressure (CPAP) treatment has a beneficial effect on hypertension and improves the survival rate of patients with cardiovascular disease. Thus, long-term compliance with CPAP treatment may result in substantial blood pressure reduction in patients with resistant hypertension suffering from OSAS. Central sleep apnea and Cheyne-Stokes respiration occur in 30-50% of patients with heart failure (HF). Intermittent hypoxemia, nocturnal surges in sympathetic activity, and increased left ventricular preload and afterload due to negative intrathoracic pressure all lead to impaired cardiac function and poor life prognosis. SDB-related HF has been considered the potential therapeutic target. CPAP, nocturnal O2 therapy, and adaptive servoventilation minimize the effects of sleep apnea, thereby improving cardiac function, prognosis, and quality of life. Early diagnosis and treatment of SDB will yield better therapeutic outcomes for hypertension and HF.

Association between QRS duration and obstructive sleep apnea

BACKGROUND

Both obstructive sleep apnea (OSA) and prolonged QRS duration are associated with hypertension, heart failure, and sudden cardiac death. However, possible links between QRS duration and OSA have not been explored.

METHODS

Cross-sectional study of 221 patients who underwent polysomnography at our center. Demographics, cardiovascular risk factors and ECG were collected to explore a relationship between OSA and QRS duration.

RESULTS

The apnea-hypopnea index (AHI) was positively correlated with QRS duration (r = 0.141, p = 0.03). Patients were divided into 3 groups: AHI < 5 (61), AHI 5-29 (104), and AHI > 30 (55). The mean QRS duration prolonged significantly as OSA worsened (AHI < 5, 85 ± 9.5; AHI 5-29, 89 ± 11.9; and AHI > 30, 95 ± 19.9 ms, p = 0.001). QRS ≥ 100 ms was present in 12.7% of patients with severe OSA compared with 0% in the rest of the sample (p < 0.0001). After adjustment for age, race, and cardiovascular risk factors, this association remained significant in women but not in men.

CONCLUSION

QRS duration and OSA were significantly associated. Severity of OSA independently predicted prolonged QRS in women but not men. Nevertheless, prolongation of QRS duration in either sex may potentiate arrhythmic risks associated with OSA.

Etiopathogenetic mechanisms of pulmonary hypertension in sleep-related breathing disorders

Obstructive sleep apnea syndrome is a common disorder with significant health consequences and is on the rise in consonance with the obesity pandemic. In view of the association between sleep-disordered breathing and pulmonary hypertension as depicted by multiple studies, current clinical practice guidelines categorize obstructive sleep apnea as a risk factor for pulmonary hypertension and recommend an assessment for sleep disordered breathing in evaluating patients with pulmonary hypertension. The dysregulatory mechanisms associated with hypoxemic episodes observed in sleep related breathing disorders contribute to the onset of pulmonary hypertension and identification of these potentially treatable factors might help in the reduction of overall cardiovascular mortality.

Relationship between obstructive sleep apnea severity index and left ventricular function and volume

BACKGROUND AND OBJECTIVES

Obstructive sleep apnea (OSA) causes increased cardiovascular morbidity and mortality, including systemic arterial hypertension, coronary heart disease, heart rhythm and conduction disorders, heart failure and stroke. In our study, we aimed to assess left ventricular mass and myocardial performance index (MPI) in OSA patients.

DESIGN AND SETTING

A cross-sectional study conducted between May 2007 and August 2009 in a tertiary hospital in Istanbul, Turkey.

PATIENTS AND METHODS

Forty subjects without any cardiac or pulmonary disease referred for evaluation of OSA had overnight polysomnography and echocardiography. According to the apnea-hypopnea index (AHI), subjects were classified into three groups; mild OSA (AHI: 5-14/h; n=7), moderate OSA (AHI: 15-29/h; n=13), and severe OSA (AHI: ;ge;30/h; n=20). The thickness of the interventricular septum (IVS) and left ventricular posterior wall (LVPW) were measured by M-mode along with left ventricular mass (LVM) and LVM index (LVMI). The left ventricular MPI was calculated as (isovolumic contraction time + isovolumic relaxation time)/aortic ejection time by Doppler echocardiography.

RESULTS

No differences were observed in age or body mass index among the groups, but blood pressures were higher in severe OSA compared with moderate and mild OSA. In severe OSA, the thickness of the IVS (11.6 [1.7 mm]), LVPW (10.7 [1.7 mm]), LVM (260.9 [50.5 g]), and LVMI (121.9 [21.1g/m2]) were higher than in moderate OSA (9.4 [1.3 mm]; 9.9 [1.6]; 196.4 [35.2]; 94.7 [13.2 g/m2], respectively) and mild OSA (9.8 [2.4 mm], 8.9 [2.0 mm], 187.6 [66.2 g], 95.8 [28.6 g/m2], respectively). In severe OSA, MPI (0.8 [0.2]) was significantly higher than in mild OSA (0.5 [P<.01]) but not significantly higher than moderate OSA (0.8 [0.1]).

CONCLUSIONS

OSA patients have demonstrable cardiac abnormalities that worsen with the severity of apnea. The MPI may have utility in subsequent OSA studies, possibly as a surrogate outcome measure.

Prevalence of obstructive sleep apnea, associated risk factors, and quality of life among Indian congestive heart failure patients: a cross-sectional survey

BACKGROUND AND OBJECTIVES

Stable congestive heart failure (CHF) patients frequently suffer from sleep apnea, which worsens the prognosis of heart failure and affects sleep quality of the patient. The present study was undertaken to assess the prevalence of obstructive sleep apnea (OSA) and associated quality of life (QOL) among CHF patients and to ascertain the relationship of OSA with excessive daytime sleepiness and selected demographic, clinical, and anthropometric characteristics.

SUBJECTS AND METHODS

Fifty CHF patients and 50 healthy controls were conveniently recruited at CHF clinic, cardiothoracic and neurosciences center outpatient department, All India Institute of Medical Sciences, New Delhi, India. Participants were interviewed using Epworth Sleepiness Scale, Modified Berlin Questionnaire, Kansas City Cardiomyopathy Questionnaire, and Quebec Sleep Questionnaire.

RESULTS

The present study revealed 18% and 8% prevalence of OSA in the CHF and control groups, respectively. The prevalence of OSA was comparable in males and females. Excessive daytime sleepiness was significantly associated with OSA in CHF patients (P = .02). Clinical severity (New York Heart Association class) and duration of illness were not significantly associated with OSA. Increased body mass index and neck circumference were the significant risk factors responsible for OSA. Quality of life of CHF patients was poor, and OSA had a significantly negative impact on the already compromised QOL in CHF patients as well as in individuals with no CHF.

CONCLUSION

Prevalence of OSA is high in CHF patients as well as in the general population, and it has negative impact on the already compromised QOL of CHF patient; therefore, assessment of the risk of OSA and referral for appropriate treatment should be a part of routine nursing clinical workup. Nursing interventions should also be planned to improve sleep quality of CHF patients.

Effects of nasal continuous positive airway pressure on left ventricular concentric hypertrophy in obstructive sleep apnea syndrome

OBJECTIVE

Abnormal left ventricular (LV) geometry, especially concentric hypertrophy, is associated with cardiovascular morbidity and mortality. The aim of this study was to evaluate the impact of obstructive sleep apnea syndrome (OSAS) and the effects of nasal continuous positive airway pressure (CPAP) on the LV geometric patterns.

METHODS

The LV morphological parameters, including the LV mass index (LVMI) and the relative wall thickness (RWT), were evaluated using echocardiography in 37 patients with OSAS diagnosed on polysomnography and 34 control subjects. Based on the values of LVMI and RWT, the LV geometry was classified as normal, concentric remodeling, concentric hypertrophy or eccentric hypertrophy. The echocardiographic parameters were reassessed after three months of CPAP treatment.

RESULTS

Compared with the controls, the OSAS patients had a higher proportion of concentric hypertrophy patterns (54% vs. 0%, p<0.001) and a lower proportion of normal geometric patterns (5% vs. 62%, p<0.001). A univariate logistic regression analysis showed the apnea-hypopnea index, lowest oxygen saturation, hypoxemia index and body mass index to each be significantly associated with the presence of concentric hypertrophy. In a multivariate analysis of these factors, the apnea-hypopnea index was found to be a significant independent factor associated with the presence of concentric hypertrophy (odds ratio: 1.06, p=0.008). Three months of CPAP treatment resulted in significant decreases in LVMI and the proportion of cases with concentric hypertrophy (both p=0.025).

CONCLUSION

In our limited study population, OSAS patients were found to be associated with a high prevalence of concentric LV hypertrophy patterns that were able to be reversed with three months of CPAP treatment.

Left ventricle remodelling is associated with sleep-disordered breathing in non-ischaemic cardiopathy with systolic dysfunction

Sleep-disordered breathing (SDB) is associated with left ventricle (LV) remodelling in patients with normal LV function. Sleep-disordered breathing is common in chronic heart failure (CHF) with systolic LV dysfunction, and may contribute to LV remodelling and CHF progression. Our aim was to determine the consequence of SDB on LV geometry in patients with CHF. We hypothesised that SDB severity was correlated with the degree of LV hypertrophy (LVH). One-hundred and sixty patients with CHF with a non-ischaemic systolic LV dysfunction were assessed by overnight polygraphy and echocardiography. Patients were classified in four groups according to their apnoea-hypopnoea index (AHI): <5 (no-SDB); 5-14 (mild); 15-29 (moderate); ≥30 (severe). Left ventricular mass index (LVM Ind) was calculated using the usual echocardiographic M-Mode parameters. Their mean age, New York Heart Association and left ventricular ejection fraction were, respectively: 56 ± 13 years, 2.4 ± 0.8 and 30 ± 10%, and 77% were men. Body mass index, interventricular septal and posterior LV wall thicknesses, and LVM Ind were significantly increased in severe SDB versus no-SDB. LVM Ind was correlated to the AHI (R = 0.27, P = 0.0006) and, using logistic regression, AHI was the unique independent factor of LVH in this population. In non-ischaemic CHF, SDB severity is associated with LV remodelling.

Associations of Framingham risk score profile and coronary artery calcification with sleep characteristics in middle-aged men and women: Pittsburgh SleepSCORE study

BACKGROUND

Short and less efficient sleep may be risk factors for atherosclerosis. Few studies have investigated the associations between sleep characteristics and early cardiovascular disease (CVD) risk.

OBJECTIVE

Evaluate the associations between coronary artery calcification (CAC) and Framingham risk score profile with sleep characteristics in middle-aged men and women with no history of diagnosed myocardial infarction, interventional cardiology procedures, stroke, diabetes, or sleep disorders.

METHOD

224 participants enrolled in an epidemiological study of disparities in CVD risk were recruited for a 9-night assessment of sleep, with 2 nights of polysomnography (PSG) and 9 nights of actigraphy and sleep diaries. Of the 224 participants, 110 had high/moderate Framingham risk scores and 114 had low scores; 195 had computed tomography measures of CAC.

RESULTS

Individuals who had any CAC or higher Framingham risk scores had elevated apnea/hypopnea index (AHI) values, independent of age, race, and gender. The AHI association with CAC was nonsignificant in analyses adjusting for body mass index (BMI). Those with higher Framingham risk score profiles had shorter PSG sleep duration and less percent stage 3-4 and delta power sleep. High blood pressure and left ventricular hypertrophy were related to AHI and sleep duration, independent of BMI. Neither sleep duration nor efficiency was associated with CAC.

CONCLUSIONS

CAC was not associated with AHI, independent of BMI in a community-based sample of middle-aged men and women. Framingham risk score profiles were related to poor sleep. Sleep duration may not be related to early plaque burden in relatively healthy individuals.

Influence of obstructive sleep apnea on left ventricular mass and global function: sleep apnea and myocardial performance index

Obstructive sleep apnea (OSA) is associated with cardiovascular mortality and morbidity. It may predispose patients to left ventricular hypertrophy and heart failure. The aim of this study was to determine the left ventricular mass (LVM) and myocardial performance index (MPI) reflecting left ventricular global function in uncomplicated OSA patients. Sixty-four subjects without hypertension, diabetes mellitus, and any cardiac or pulmonary disease referred for evaluation of OSA underwent overnight polysomnography and complete echocardiographic assessment. According to the apnea hypopnea index (AHI), subjects were divided into three groups: group 1, control subjects with nonapneic snorers (AHI < 5, n = 18); group 2, patients with mild to moderate OSA (AHI: 5-30, n = 25); and group 3, severe OSA (AHI > 30, n = 21). Basic echocardiographic measurements, LVM, and LVM index were measured. Left ventricular MPI was calculated as (isovolumic contraction time+isovolumic relaxation time)/aortic ejection time by Doppler echocardiography. There were no significant differences in age, sex, body mass index, heart rate, and systolic and diastolic blood pressure among the three groups. Left atrium, interventricular septum, left ventricular posterior wall, left ventricular end-diastolic and end-systolic diameters, LVM mass, and LVM index were not significantly different among the three groups. Left ventricular MPI was significantly higher in severe OSA patients (0.64 +/- 0.18) than in controls (0.49 +/- 0.18; P < 0.05). There was no significant difference between controls (0.49 +/- 0.18) and mild to moderate OSA (0.61 +/- 0.16; P = 0.08) and between mild to moderate OSA (0.61 +/- 0.16) and severe OSA (0.64 +/- 0.18; P = 0.84). The present study demonstrates that patients with severe OSA have global left ventricular dysfunction.

Severe obstructive sleep apnea elicits concentric left ventricular geometry

BACKGROUND

Obstructive sleep apnea (OSA) has several negative effects on the heart including increase in myocardial end-systolic stress, venous return and sympathetic activity, all potential stimuli of left ventricular (LV) hypertrophy. The impact of the severity of OSA on LV geometry is unknown. We hypothesized that OSA is related to concentric LV geometry.

METHODS

One hundred and fifty-seven patients with suspected OSA underwent echocardiography, ambulatory 24-h blood pressure and ECG monitoring. On the basis of the severity of OSA, patients were divided into controls, mild OSA and moderate/severe OSA (apnea-hypopnea index <5, 5-15 and >15/h, respectively). Patients with LV hypertrophy were defined as LV mass at least 49.2 g/m2.7 for men and at least 46.7 for women. Relative wall thickness of at least 0.43 identified patients with concentric LV geometry.

RESULTS

Patients with moderate/severe OSA (n = 86) had a higher body mass index and a higher prevalence of paroxysmal atrial fibrillation than those (n = 51) with mild OSA and controls (n = 20). Prevalence of hypertension, diabetes, obesity, LV mass and blood pressure did not differ between the groups. Relative wall thickness was positively related to apnea-hypopnea index (r = 0.30; P = 0.003) and the prevalence of concentric LV geometry was 20% in controls, 12% in mild OSA and 58% in moderate/severe OSA (P < 0.001). In logistic regression analysis concentric LV geometry was associated with moderate/severe OSA [odds ratio (OR) 7.6, P < 0.001], low stress-corrected midwall shortening (OR 3.38, P = 0.004), and higher body mass index (OR 1.09, P = 0.03).

CONCLUSIONS

Moderate/severe OSA is associated with high prevalence of concentric LV geometry. This increased prevalence may in part explain the increased rate of cardiovascular events in these patients.

[Cardiac effects of obstructive sleep apnea]

Sleep disordered breathing, especially obstructive sleep apnea, are common in cardiovascular disease. Negative hemodynamic effects are mediated by nocturnal ischemia and intrathoracal pressure swings. Therefore "therapy resistant" arterial hypertension and congestive heart failure, as well as atrial fibrillation or sleep associated bradycardia are suggestive of sleep disordered breathing. Further on, clinical course of coronary artery disease seems to be influenced by nocturnal breathing disorders. Application of continuous positive airway pressure (CPAP) is effective in most of the patients and attenuates cardiodepressive hemodynamic effects of obstructive sleep apnea.

Impact of obstructive sleep apnoea on clinical characteristics and outcomes in patients with acute coronary syndrome following percutaneous coronary intervention

This study tested whether obstructive sleep apnoea syndrome (OSAS) influenced clinical characteristics and outcomes after successful percutaneous coronary intervention (PCI) in 123 consecutive patients with acute coronary syndrome (ACS). Patients with an apnoea-hypopnea index (AHI) >or= 5 were considered as having OSAS. Carotid ultrasonography and echocardiography were performed, and C-reactive protein (CRP) and fibrinogen were measured. Co-existence of ACS and OSAS occurred in 76 patients (61.8%) and patients with OSAS had a greater interventricular septum thickness (IVST) and higher levels of CRP than non-OSAS patients. In an elderly subpopulation (>or= 75 years of age), two-vessel disease was significantly more common and fibrinogen levels were significantly higher in OSAS than non-OSAS patients. Carotid intima-media thickness (IMT) correlated with the AHI in ACS patients. In elderly ACS patients, IMT, Gensini score and fibrinogen correlated with AHI. Patients were followed up for 1 year for major adverse cardiac events (MACEs) and no significant difference in major MACEs was found after this period between OASAS and non-OSAS patients. This study indicates that OSAS is associated with inflammation and increased IVST in ACS patients after successful PCI and, in elderly ACS patients, also with CAD severity and enhanced blood coagulability.

Pathophysiology of sleep apnea

Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.

Early cardiovascular abnormalities in newly diagnosed obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with high cardiovascular morbidity and mortality. Recent studies have shown that it is associated with atherosclerosis and left ventricular dysfunction markers. The aim of this study was to assess the cardiovascular effects of OSA depending on its severity, in patients without clinically diagnosed cardiovascular disease. One hundred thirty newly diagnosed, nondiabetic OSA patients (mean age 49 +/- 10 years), without vasoactive treatment were included. They underwent clinical and ambulatory blood pressure measurements, echocardiography, carotid ultrasound examination, and a carotid-femoral pulse wave velocity (PWV) measurement. Seventy-five percent of the subjects were hypertensive according to the clinical or ambulatory measurement. More patients with the most severe forms (respiratory disturbance index >37/hour) had a nondipper profile (52% vs 34%; P = 0.025) and their left ventricular mass was higher (40 +/- 7 vs 36 +/- 8 g/m, p = 0.014). This last parameter was independently and inversely associated with mean nocturnal oxygen saturation (P = 0.004). PWV and carotid intima-media thickness did not differ between one OSA severity group to another, but the prevalence of carotid hypertrophy was higher when mean SaO(2) was below 93.5% (29.5 vs 16%; P = 0.05). Our study shows that in OSA patients without clinically diagnosed cardiovascular disease, there is a significant left ventricular and arterial effect, which is even more marked when OSA is severe.

Circadian rhythm of autonomic activity in patients with obstructive sleep apnea syndrome

BACKGROUND AND HYPOTHESIS

Although the immediate effects of sleep apnea on hemodynamics and the neurological system have been studied, little is known about the circadian rhythm of heart rate variability in patients with obstructive sleep apnea syndrome (OSAS). The purpose of the present study was to investigate the effects of sleep apnea on the autonomic activity during daytime, which may play some role in the pathogenesis of cardiovascular complications in OSAS.

METHODS

We studied 18 middle-aged male patients with OSAS and 10 age-matched control subjects. Patients with OSAS were classified according to the severity of OSAS: patients with an apnea index (AI) < 20 were considered to have mild OSAS (Group 1, n = 8) and patients with an AI > or = 20 were considered to have severe OSAS (Group 2, n = 10). Heart rate variability was calculated from the 24-h ambulatory electrocardiograms by the Fourier transformation. Power spectra were quantified at 0.04-0.15 Hz [low frequency power (LF)ln(ms2)] and 0.15-0.40 Hz [high frequency power (HF)ln(ms2)]. The HF component and the ratio of LF to HF were used as indices of the parasympathetic and sympathetic activity, respectively.

RESULTS

The circadian rhythms of the LF, HF, and LF/HF ratio differed significantly in Group 2 compared with Group 1 and control subjects (p < 0.05). Hypertension (> 160/95 mm Hg) was found in 7 (70.0%) of 10 patients in Group 2, and in 1 (12.5%) of 8 patients in Group 1. Echocardiographic evidence of left ventricular hypertrophy (LVH) (an interventricular septal thickness or a left ventricular posterior wall thickness > or = 12 mm) was found in 3 (30.0%) of 10 patients in Group 2, and in 1 (12.5%) of 8 patients in Group 1. The mean HF from 4 A.M. to 12 noon was significantly lower in Group 2 than in Group 1 and the control group, and it correlated significantly with the lowest nocturnal SaO2 (r = 0.58, p < 0.05). The mean LF/HF ratio during the same period was significantly higher in Group 2 than in Group 1 and the control group, and it correlated significantly with total time of the nocturnal oxygen saturation < 90% (r = 0.64, p < 0.005) and the lowest nocturnal SaO2 (r = 0.56, p < 0.05). Ventricular tachycardia was found in the early morning in one patient, ST-T depression in two patients, and sinus arrest in two patients in Group 2.

CONCLUSION

These findings suggest that sleep-disordered breathing associated with severe oxygen desaturation might influence heart rate variability not only during sleep but also during daytime. OSAS per se might contribute to altered circadian rhythm in autonomic activity leading to the development of cardiovascular diseases.