Blood pressure, cardiac structure and severity of obstructive sleep apnea in a sleep clinic population

Is myocardial strain an early marker of systolic dysfunction in obstructive sleep apnoea? Findings from a meta-analysis of echocardiographic studies

AIM

We investigated the association between obstructive sleep apnoea (OSA) and subclinical systolic dysfunction through a meta-analysis of echocardiographic studies that provided data on left ventricular (LV) mechanics as assessed by global longitudinal strain (GLS).

DESIGN

The PubMed, OVID-MEDLINE, and Cochrane library databases were systematically analyzed to search English-language articles published from inception to 31 December 2021. Studies were detected by using the following terms: 'obstructive sleep apnea', 'sleep quality', 'sleep disordered breathing', 'cardiac damage', 'left ventricular hypertrophy', 'systolic dysfunction', 'global longitudinal strain', 'left ventricular mechanics', 'echocardiography' and 'speckle tracking echocardiography'.

RESULTS

The meta-analysis included 889 patients with OSA and 364 non-OSA controls from 12 studies. Compared with controls, GLS was significantly reduced in the pooled OSA group (SMD -1.24 ± 0.17, CI: -1.58 to -0.90, P  < 0.0001), as well as in the normotensive OSA subgroup (SMD: -1.17 ± 0.12 CI:-1.40 to -0.95, P  < 0.0001). Similar findings were obtained in sub-analyses performed separately in mild, moderate and severe OSA. This was not the case for LV ejection fraction (LVEF) (i.e. comparisons between controls vs. mild OSA, mild vs. moderate OSA, moderate vs. severe OSA).

CONCLUSION

GLS is impaired in patients with OSA (independently from hypertension), worsening progressively from mild to moderate and severe forms, thus allowing to identify subclinical alterations of the systolic function not captured by LVEF. Therefore, myocardial strain assessment should be implemented systematically in the OSA setting to timely detect systolic dysfunction.

[Cardiac dysfunction and the obstructive sleep apnoea syndrome]

INTRODUCTION

Cardiac insufficiency affects nearly 2% of the population with increased morbidity/mortality despite advances in therapeutic management. The sleep apnoea syndrome (SAS) is a risk factor for, and cause of aggravation of, myocardial dysfunction.

BACKGROUND

SAS is found in 70% of patients with chronic cardiac failure, 65% of patients with refractory hypertension, 60% of patients with cerebro-vascular accidents and 50% of patients with atrial fibrillation. The associated cardiovascular mortality is multiplied by a factor of 2 to 3. The pathophysiological mechanisms are intermittent nocturnal hypoxia, variations in CO₂ levels, variations in intrathoracic pressure and repeated arrousals from sleep, concurrent with sympathetic hyperactivity, endothelial dysfunction and systemic inflammation.

CONCLUSIONS

SAS and cardiological management in patients presenting with myocardial dysfunction should be combined. It is necessary to pursue the scientific investigations with the aim of determining a precise care pathway and the respective places of each of the cardiological and pulmonary measures.

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.

Relationship between Clinical and Polysomnography Measures Corrected for CPAP Use

OBJECTIVES

The changes in patient-reported measures of obstructive sleep apnea (OSA) burden are largely discordant with the change in apnea-hypopnea index (AHI) and other polysomnography measures before and after treatment. For patients treated with continuous positive airway pressure (CPAP), some investigators have theorized that this discordance is due in part to the variability in CPAP use. We aim to test the hypothesis that patient-reported outcomes of CPAP treatment have stronger correlations with AHI when it is corrected for mean nightly CPAP use.

METHODS

This was a cross-sectional study of 459 adults treated with CPAP for OSA. Five patient-reported measures of OSA burden were collected at baseline and after 6 months of CPAP therapy. The correlations between the change in each patient-reported measure and the change in AHI as well as mean nightly AHI (corrected for CPAP use with a weighted average formula) were measured after 6 months of treatment. The same analysis was repeated for 4 additional polysomnography measures, including apnea index, arousal index, lowest oxyhemoglobin saturation, and desaturation index.

RESULTS

The change in AHI was weakly but significantly correlated with change in 2 of the 5 clinical measures. The change in mean nightly AHI demonstrated statistically significant correlations with 4 out of 5 clinical measures, though each with coefficients less than 0.3. Similar results were seen for apnea index, arousal index, lowest oxyhemoglobin saturation, and desaturation index.

CONCLUSIONS

Correction for CPAP use yielded overall small but significant improvements in the correlations between patient-reported measures of sleep apnea burden and polysomnography measures after 6 months of treatment.

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.

Frequent periodic leg movement during sleep is associated with left ventricular hypertrophy and adverse cardiovascular outcomes

BACKGROUND

Sleep disturbance caused by obstructive sleep apnea is recognized as a contributing factor to adverse cardiovascular outcomes. However, the effect of restless legs syndrome, another common cause of fragmented sleep, on cardiac structure, function, and long-term outcomes is not known. The aim of this study was to assess the effect of frequent leg movement during sleep on cardiac structure and outcomes in patients with restless legs syndrome.

METHODS

In our retrospective study, patients with restless legs syndrome referred for polysomnography were divided into those with frequent (periodic movement index > 35/hour) and infrequent (≤ 35/hour) leg movement during sleep. Long-term outcomes were determined using Kaplan-Meier and logistic regression models.

RESULTS

Of 584 patients, 47% had a periodic movement index > 35/hour. Despite similarly preserved left ventricular ejection fraction, the group with periodic movement index > 35/hour had significantly higher left ventricular mass and mass index, reflective of left ventricular hypertrophy (LVH). There were no significant baseline differences in the proportion of patients with hypertension, diabetes, hyperlipidemia, prior myocardial infarction, stroke or heart failure, or the use of antihypertensive medications between the groups. Patients with frequent periodic movement index were older, predominantly male, and had more prevalent coronary artery disease and atrial fibrillation. However, on multivariate analysis, periodic movement index > 35/hour remained the strongest predictor of LVH (odds ratio, 2.45; 95% confidence interval, 1.67-3.59; P < .001). Advanced age, female sex, and apnea-hypopnea index were other predictors of LVH. Patients with periodic movement index > 35/hour had significantly higher rates of heart failure and mortality over median 33-month follow-up.

CONCLUSIONS

Frequent periodic leg movement during sleep is an independent predictor of severe LVH and is associated with increased cardiovascular morbidity and mortality.

Composite severity indices reflect sleep apnea disease burden more comprehensively than the apnea-hypopnea index

OBJECTIVE

To compare 2 composite indices of sleep apnea disease burden with the commonly used apnea-hypopnea index with regard to baseline measurement of subjective and objective disease burden.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary academic medical center sleep laboratory.

SUBJECTS AND METHODS

Patients with suspected diagnosis of sleep apnea undergoing first diagnostic polysomnography. Subjective data were collected via validated questionnaires; objective data were obtained by standardized physical examination, chart extraction, and polysomnography. Four subjective (patient-reported) disease burden measures and 3 objective (anatomic and physiologic) disease burden measures were used for validation. Associations between composite indices or apnea-hypopnea index and these 7 construct validation measures were compared using bootstrapped correlation coefficients.

RESULTS

Two hundred sixteen subjects were included in the final analysis. Both composite disease burden indices showed clinically important or nearly important associations with 3 of 4 subjective validation measures and all 3 objective validation measures, whereas the apnea-hypopnea index was associated only with the objective validation measures.

CONCLUSION

Composite indices of sleep apnea disease burden may capture the breadth of baseline sleep apnea disease burden, particularly subjective disease burden, better than the apnea-hypopnea index.

Mood Predicts Response to Placebo CPAP

Study Objectives. Continuous positive airway pressure (CPAP) therapy is efficacious for treating obstructive sleep apnea (OSA), but recent studies with placebo CPAP (CPAP administered at subtherapeutic pressure) have revealed nonspecific (or placebo) responses to CPAP treatment. This study examined baseline psychological factors associated with beneficial effects from placebo CPAP treatment. Participants. Twenty-five participants were studied with polysomnography at baseline and after treatment with placebo CPAP. Design. Participants were randomized to either CPAP treatment or placebo CPAP. Baseline mood was assessed with the Profile of Mood States (POMS). Total mood disturbance (POMS-Total) was obtained by summing the six POMS subscale scores, with Vigor weighted negatively. The dependent variable was changed in apnea-hypopnea index (ΔAHI), calculated by subtracting pre- from post-CPAP AHI. Negative values implied improvement. Hierarchical regression analysis was performed, with pre-CPAP AHI added as a covariate to control for baseline OSA severity. Results. Baseline emotional distress predicted the drop in AHI in response to placebo CPAP. Highly distressed patients showed greater placebo response, with a 34% drop (i.e., improvement) in AHI. Conclusion. These findings underscore the importance of placebo-controlled studies of CPAP treatment. Whereas such trials are routinely included in drug trials, this paper argues for their importance even in mechanical-oriented sleep interventions.

Common secondary causes of resistant hypertension and rational for treatment

Resistant hypertension is defined as uncontrolled blood pressure despite the use of three antihypertensive drugs, including a diuretic, in optimal doses. Treatment resistance can be attributed to poor adherence to antihypertensive drugs, excessive salt intake, physician inertia, inappropriate or inadequate medication, and secondary hypertension. Drug-induced hypertension, obstructive sleep apnoea, primary aldosteronism, and chronic kidney disease represent the most common secondary causes of resistant hypertension. Several drugs can induce or exacerbate pre-existing hypertension, with non-steroidal anti-inflammatory drugs being the most common due to their wide use. Obstructive sleep apnoea and primary aldosteronism are frequently encountered in patients with resistant hypertension and require expert management. Hypertension is commonly found in patients with chronic kidney disease and is frequently resistant to treatment, while the management of renovascular hypertension remains controversial. A step-by-step approach of patients with resistant hypertension is proposed at the end of this review paper.

Review article: Managing sleep apnoea in kidney diseases

A higher prevalence of sleep apnoea (SA) has been observed in the chronic kidney disease (CKD) population compared with estimates in the general population. Increased rates of SA have been described in patients with various renal-related diagnoses including dialysis, renal transplant, early-stage CKD and proteinuria. The mechanism or underlying aetiology for this association is different for each type of kidney disease. The extracellular fluid volume and metabolic derangements that characterize the uremic state likely contributes to SA in the dialysis population. SA causing direct renal insults from haemodynamic changes, ischaemic stress, or an intermediary condition such as hypertension, can lead to early CKD and proteinuria. While renal transplantation has cured SA in some patients, the post-transplant state is itself a risk factor for SA. The high prevalence of SA in kidney disease and the associated clinical implications warrant vigilance in diagnosis and treatment of SA in the CKD patient. This review focuses on the prevalence of SA in patients with CKD including dialysis and transplant patients, and those with early-stage CKD and proteinuria. SA may vary in form and aetiology depending on type or stage of CKD. Based on these associations, we discuss our rationale for recommendations on screening and management of SA specific to the CKD population.

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.

The price of obstructive sleep apnea-hypopnea: hypertension and other ill effects

This review addresses the cardiovascular, cerebrovascular, and metabolic consequences that accompany obstructive sleep apnea-hypopnea (OSAH) in conjunction with the mechanistic pathways implicated in mediating these effects. Particular emphasis is placed on the association with hypertension (HTN). Varying levels of evidence support a role of OSAH in perpetuating sustained HTN, nocturnal HTN, and difficult to control HTN as well as in contributing to the occurrences of nondipping of blood pressure (BP) and increased BP variability. In this context, the emergence of matched designs, adjusted analyses, meta-analyses as well as longitudinal and interventional studies strengthens causal inferences drawn from older observational studies, which suffered from such limitations as confounding.

Left ventricular morphology and systolic function in sleep-disordered breathing: the Sleep Heart Health Study

BACKGROUND

Whether sleep-disordered breathing (SDB) is a risk factor for left ventricular (LV) hypertrophy and dysfunction is controversial. We assessed the relation of SDB to LV morphology and systolic function in a community-based sample of middle-aged and older adults.

METHODS AND RESULTS

The present study was a cross-sectional observational study of 2058 Sleep Heart Health Study participants (mean age 65+/-12 years; 58% women; 44% ethnic minorities) who had technically adequate echocardiograms. A polysomnographically derived apnea-hypopnea index (AHI) and hypoxemia index (percent of sleep time with oxyhemoglobin saturation < 90%) were used to quantify SDB severity. LV mass index was significantly associated with both AHI and hypoxemia index after adjustment for age, sex, ethnicity, study site, body mass index, current and prior smoking, alcohol consumption, systolic blood pressure, antihypertensive medication use, diabetes mellitus, and prevalent myocardial infarction. Adjusted LV mass index was 41.3 (SD 9.90) g/m(2.7) in participants with AHI < 5 (n=957) and 44.1 (SD 9.90) g/m(2.7) in participants with AHI > or = 30 (n=84) events per hour. Compared with participants with AHI < 5, those with AHI > or = 30 had an adjusted odds ratio of 1.78 (95% confidence interval 1.14 to 2.79) for LV hypertrophy. A higher AHI and higher hypoxemia index were also associated with larger LV diastolic dimension and lower LV ejection fraction, with a trend toward lower LV fractional shortening. LV wall thickness was significantly associated with the hypoxemia index but not with AHI. Left atrial diameter was not associated with either SDB measure.

CONCLUSIONS

In a community-based cohort, SDB is associated with echocardiographic evidence of increased LV mass and reduced LV systolic function.

Independent association between obstructive sleep apnea and subclinical coronary artery disease

BACKGROUND

Obstructive sleep apnea (OSA) is associated with coronary risk factors, but it is unknown if OSA is associated with development of coronary disease. We evaluated the association between OSA and the presence of subclinical coronary disease assessed by coronary artery calcification (CAC).

METHODS

Consecutive patients with no history of coronary disease who underwent electron-beam CT within 3 years of polysomnography between March 1991 and December 2003 were included. OSA was defined by an apnea-hypopnea index (AHI) > or = 5 events per hour, and patients were grouped by quartiles of AHI severity. Logistic regression modeled the association between OSA severity and presence of CAC.

RESULTS

There were 202 patients (70% male; median age, 50 years; mean body mass index, 32 kg/m(2); 8% diabetic; 9% current smokers; 60% hypercholesterolemic; and 47% hypertensive). OSA was present in 76%. CAC was present in 67% of OSA patients and 31% of non-OSA patients (p < 0.001). Median CAC scores (Agatston units) were 9 in OSA patients and 0 in non-OSA patients (p < 0.001). Median CAC score was higher as OSA severity increased (p for trend by AHI quartile < 0.001). With multivariate adjustment, the odds ratio for CAC increased with OSA severity. Using the first AHI quartile as reference, the adjusted odds ratios for the second, third, and fourth quartiles were 2.1 (p = 0.12), 2.4 (p = 0.06), and 3.3 (p = 0.03), respectively.

CONCLUSIONS

In patients without clinical coronary disease, the presence and severity of OSA is independently associated with the presence and extent of CAC. OSA identifies patients at risk for coronary disease and may represent a highly prevalent modifiable risk factor.

Sleep apnea: epidemiology, pathophysiology, and relation to cardiovascular risk

Several studies have shown the occurrence of an independent association between obstructive sleep apnea syndrome (OSAS) and cardiovascular disease, including arterial hypertension, ischemic heart disease, and stroke. The pathogenesis of the cardiovascular complications of OSAS is still poorly understood, however. Several mechanisms are likely to be involved, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormality in the process of coagulation, and metabolic dysregulation. The latter may involve insulin resistance and disorders of lipid metabolism. The aim of this review, which reports the data presented at a workshop jointly endorsed by the European Society of Hypertension and by the European Union COST action on OSAS (COST B26), is to critically summarize the evidence available to support an independent association between OSAS and cardiovascular disease.

Obstructive sleep apnea: an update on mechanisms and cardiovascular consequences

BACKGROUND AND AIM

There is growing recognition of the widespread incidence and health consequences of obstructive sleep apnea (OSA). This review examines the evidence linking sleep apnea with cardiovascular disease and discusses potential mechanisms underlying this link.

DATA SYNTHESIS

The weight of evidence provides increasing support for a causal relationship between OSA and hypertension. Furthermore, OSA may contribute to the initiation and progression of cardiac ischemia, heart failure and stroke. Chronic sympathetic activation appears to be a key mechanism linking OSA to cardiovascular disease. Other potential mechanisms include inflammation, endothelial dysfunction, increased levels of endothelin, hypercoagulability and stimulation of the renin angiotensin system. OSA, hypertension and obesity often coexist and interact, sharing multiple pathophysiological mechanisms and cardiovascular consequences. Effective treatment of OSA may attenuate neural and humoral abnormalities in circulatory control, improve blood pressure control and conceivably reduce the risk of future cardiovascular events.

CONCLUSION

Patients with OSA are at increased risk for cardiovascular disease. OSA should be considered in the differential diagnosis of hypertensive patients who are obese. In particular, OSA should be excluded in patients with hypertension resistant to conventional drug therapy.

Left ventricular hypertrophy in severe obesity: interactions among blood pressure, nocturnal hypoxemia, and body mass

Obese subjects have a high prevalence of left ventricular (LV) hypertrophy. It is unclear to what extent LV hypertrophy results directly from obesity or from associated conditions, such as hypertension, impaired glucose homeostasis, or obstructive sleep apnea. We tested the hypothesis that LV hypertrophy in severe obesity is associated with additive effects from each of the major comorbidities. Echocardiography and laboratory testing were performed in 455 severely obese subjects with body mass index 35 to 92 kg/m(2) and 59 nonobese reference subjects. LV hypertrophy, defined by allometrically corrected (LV mass/height(2.7)), gender-specific criteria, was present in 78% of the obese subjects. Multivariable regression analyses showed that average nocturnal oxygen saturation <85% was the strongest independent predictor of LV hypertrophy (P<0.001), followed by systolic blood pressure (P<0.015) and then body mass index (P<0.05). With regard to LV mass, there were synergistic effects between hypertension and body mass index (P interaction <0.001) and between hypertension and reduced nocturnal oxygen saturation. Severely obese subjects had normal LV endocardial fractional shortening (35+/-6% versus 35+/-6%) but mildly decreased midwall fractional shortening (15+/-2% versus 17+/-2%; P<0.001), indicating subtle myocardial dysfunction. In conclusion, more severe nocturnal hypoxemia, increasing systolic blood pressure, and body mass index are all independently associated with increased LV mass. The effects of increased blood pressure seem to amplify those of sleep apnea and more severe obesity.

Left ventricular geometry in patients with obstructive sleep apnea coexisting with treated systemic hypertension

BACKGROUND

Left ventricular (LV) hypertrophy is a common consequence of systemic hypertension (SH) and obstructive sleep apnea (OSA). However, little is known about the degree of LV involvement in patients with OSA coexisting with treated SH.

OBJECTIVES

Our study was designed in order to assess the prevalence of distinct types of LV geometry in treated hypertensive OSA patients.

METHODS

PATIENTS

183 patients with treated SH were enrolled to the study. Group 1 consisted of 38 patients with newly-diagnosed OSA and ineffectively treated SH. The remaining 145 patients with effectively treated SH were divided into three groups: group 2 - 70 patients with newly-diagnosed OSA, group 3 - 31 patients with OSA treated with continuous positive airway pressure (CPAP), and group 4 - 44 patients without OSA. Overnight sleep studies and M-mode echocardiography were performed.

RESULTS

LV mass index did not differ between the study groups. Mean values of LV end-diastolic diameter (LVED) were 55.4 +/- 6.8 mm in group 1 and 53.6 +/- 6.9 mm in group 2 and were significantly increased in comparison to subjects treated with CPAP and controls (49.8 +/- 6.8 mm and 50.1 +/- 64.7 mm, respectively; p = 0.001). LVED correlated positively with the apnea-hypopnea index and desaturation index. LV eccentric hypertrophy was the commonest type of LV geometry in newly-diagnosed OSA patients.

CONCLUSIONS

The major finding of our study is the predominance of LV eccentric hypertrophy in newly-diagnosed OSA patients. We suggest that a relatively moderate degree of LV involvement in hypertensive OSA patients may depend on the cardioprotective effect of concomitant antihypertensive therapy, ameliorating OSA-dependent neurohumoral abnormalities.

Obstructive sleep apnea and hypertension

There is growing evidence of a causal relationship between obstructive sleep apnea (OSA) and hypertension. Untreated OSA may have direct and deleterious effects on cardiovascular function and structure through several mechanisms, including sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. OSA may contribute to or augment elevated blood pressure levels in a large proportion of the hypertensive patient population. It is important to consider OSA in the differential diagnosis of hypertensive patients who are obese. OSA should be especially considered in those hypertensive patients who respond poorly to combination therapy with antihypertensive medications.

Plasma brain natriuretic peptide in obstructive sleep apnea

We compared brain natriuretic peptide (BNP) levels in patients with obstructive sleep apnea (OSA) with and without cardiovascular disease to BNP in healthy control subjects. OSA was not associated with increased plasma BNP or atrial natriuretic peptide (ANP) in otherwise healthy subjects during wakefulness. Untreated OSA increased ANP overnight, and ANP levels decreased with treatment of OSA. However, OSA did not elicit acute overnight changes in BNP, either in normal subjects or in patients with coexisting cardiovascular disease (including chronic heart failure).

Left ventricular hypertrophy is a common echocardiographic abnormality in severe obstructive sleep apnea and reverses with nasal continuous positive airway pressure

STUDY OBJECTIVES

To determine cardiac structural abnormalities by echocardiography in subjects with severe obstructive sleep apnea (OSA), and to determine the long-term effects of nasal continuous positive airway pressure (CPAP) on such abnormalities.

DESIGN

Polysomnography was conducted on oximetry-screened patients who showed a desaturation index > 40/h and > or = 20% cumulative time spent below 90%. From these, 25 patients with severe OSA but without daytime hypoxemia underwent echocardiography prior to, then 1 month and 6 months following initiation of CPAP treatment.

SETTING

Outpatient sleep disorders center.

RESULTS

Of the 25 patients, 13 patients (52%) had hypertension by history or on physical examination. Baseline echocardiograms showed that severe OSA was associated with numerous cardiovascular abnormalities, including left ventricular hypertrophy (LVH) [88%], left atrial enlargement (LAE) [64%], right atrial enlargement (RAE) [48%], and right ventricular hypertrophy (16%). In all patients (intent to treat) as well as those patients compliant with CPAP therapy (84% > 3 h nightly), there was a significant reduction in LVH after 6 months of CPAP therapy as measured by interventricular septal distance (baseline diastolic mean, 13.0 mm; 6-month mean after CPAP, 12.3 mm; p < 0.02). RAE and LAE were unchanged after CPAP therapy.

CONCLUSIONS

LVH was present in high frequency in subjects with severe OSA and regressed after 6 months of nasal CPAP therapy.

[Cardiovascular consequences of obstructive sleep apnea syndrome]

PURPOSE

This article is an update of past and current data on the relationship between obstructive sleep apnea syndrome and cardiovascular diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Obstructive sleep apnea syndrome is a common, but under-recognised, condition and should not be considered simplistically as the association of snoring and obesity. It may be suspected by the clinical history but a definite diagnosis requires the practice of polysomnography. Numerous studies have found a significant relationship between the presence of obstructive sleep apnea syndrome and the occurrence of cardiovascular events. Nonetheless, a definite causal relationship has only been established for the occurrence of hypertension. There are multiple immediate and delayed cardiovascular responses to the apneic events and thus there are many possible physiopathological mechanisms to explain the association of obstructive sleep apnea and cardiac and vascular events, the primary one being sympathetic hyperactivity. The prognosis of obstructive sleep apnea syndrome is closely related to the incidence of cardiovascular events. FUTURE PROSPECTS AND PROJECS: The existence of an independent relationship between obstructive sleep apnea syndrome and atherosclerosis is not yet demonstrated. The beneficial effects of continuous positive airway pressure, the treatment of choice for this condition, on the incidence of cardiovascular diseases remains to be confirmed although recent studies suggest that correct treatment of obstructive sleep apnea syndrome by continuous positive airway pressure may reduce the cardiovascular risk and in particular that of hypertension.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.

Prevalence and pathogenesis of sleep apnea and lung disease in acromegaly

Respiratory disorders are common and important complications in acromegaly. Patients suffering from acromegaly display a 1.6-3.3 fold increase in mortality rate, which is due to respiratory disorders in 25% of cases. In these patients, mortality for lung disease is 2-3 fold higher than in the general population. Every portion of the respiratory system may be involved. Deformities of facial bones, edema and hypertrophy of the mucosae and pharyngeal and laryngeal cartilages, enlargement of the tongue and inspiratory collapse of the hypopharinx, all may contribute to respiratory alterations. Nasal polyps, "hormonal rhinitis", changes of the voice and snoring are common occurrences. Though rarely, a laryngocele may ensue. Pneumomegaly is frequently observed and, as suggested by functional studies, might be due to an increased number rather than volume of the alveoli. An obstructive respiratory syndrome caused by mucosal thickening of the upper airways and bronchi is observed in 25% of female and 70% of male patients. The sleep apnea syndrome (SAS) affects 60-70% of acromegalic patients. SAS may be of obstructive, central or mixed type. Obstructive SAS is the prevailing form in acromegaly. It is due to intermittent obstruction of upper airways with preserved activity of the respiratory center, as testified by the remarkable thoracic and abdominal respiratory efforts. The pathogenesis of the central type of SAS is more complex. Narrowing of the upper airways may induce reflex inhibition of the respiratory center. Moreover, increased GH levels and, possibly, defects in the somatostatinergic pathways, may increase the ventilatory response of the respiratory center to carbon dioxide, thereby leading to respiratory arrest. In the mixed type of SAS, the phenomena underlying the other two forms coexist. Oxygen desaturation concomitant with the apneic episodes accounts for the frequent nocturnal wakening and diurnal drowsiness. Among the clinical correlates of SAS, arterial hypertension is of particular interest due to the close correlation existing between the two disorders. Sleep deprivation related to SAS seems per se to favor the appearance of hypertension. Moreover, short lasting hypoxemia may induce prolonged elevations of blood pressure, mediated by decreased endothelial generation of nitric oxide. Thus, since cardiovascular events are the main cause of mortality in patients with acromegaly, it is reasonable to hypothesize that SAS is involved in the reduced life span of these patients.