Ventricular function in snorers and patients with obstructive sleep apnea

Right Ventricular Remodeling and Dysfunction in Obstructive Sleep Apnea: A Systematic Review of the Literature and Meta-Analysis

Background

Recent studies have reported that obstructive sleep apnea (OSA) patients present alterations in right ventricular (RV) structure and function. However, large randomized controlled trials evaluating the impact of OSA on the right ventricle are lacking.

Methods

A comprehensive electronic database (PubMed, Web of Science, and Google Scholar) and reference search up to October 30, 2016, was performed. A systematic review and meta-analysis were performed to assess RV structure and function in OSA patients based on conventional echocardiography and tissue Doppler imaging.

Results

Twenty-five studies with 1,503 OSA patients and 796 controls were included in this study. OSA patients exhibited an increase in RV internal diameter (weighted mean difference (WMD) (95% confidence intervals (CIs)) 2.49 (1.62 to 3.37); p = 0.000) and RV wall thickness (WMD (95% CIs) 0.82 (0.51 to 1.13); p = 0.000). Furthermore, OSA patients had a significantly elevated RV myocardial performance index (WMD (95% CI) 0.08 (0.06 to 0.10); p = 0.000), decreased RV S' (WMD (95% CI) −0.95 (−1.59 to −0.32); p = 0.003), tricuspid annular plane systolic excursion (WMD (95% CI) −1.76 (−2.73 to −0.78); p = 0.000), and RV fractional area change (WMD (95% CI) −3.16 (−5.60 to −0.73); p = 0.011).

Conclusion

OSA patients display RV dilatation, increased wall thickening, and altered RV function.

Sleep Disordered Breathing: Hypertension and Cardiac Structure and Function

Obstructive sleep apnea (OSA) is a common form of sleep disordered breathing and has a relatively high prevalence in the general population. The frequency and severity of OSA is associated with age, male sex, and obesity, and OSA has been linked to cardiovascular complications and death. Importantly, OSA has a strong association with both prevalent and incidental hypertension and has a particularly high prevalence in patients with resistant hypertension. In these patients, CPAP and other OSA-directed treatments have been proposed as therapy to help control blood pressure (BP), especially in patients who have not attained optimal BP control despite maximum pharmacological therapy. OSA has also been associated with alterations in cardiac structure and function, although most studies are small and highly limited in study design. Existing data suggest an association between OSA greater left ventricle (LV) mass and hypertrophy that appears independent of confounders including hypertension and obesity. Although less clear and more controversial, OSA severity has been linked to LV systolic and diastolic function, pulmonary hypertension, and right ventricular hypertrophy. Further studies are needed to confirm the potential causal role of OSA in these observed associations with cardiac abnormalities.

A novel method for sensitive determination of subclinical right ventricular systolic dysfunction in patients with obstructive sleep apnea

OBJECTIVE

The aim of this study was to evaluate right ventricular (RV) regional systolic function and dyssynchrony in patients with newly diagnosed obstructive sleep apnea using real-time three-dimensional (3D) echocardiography.

METHODS

Eighty-two subjects without hypertension, diabetes mellitus or any cardiac or pulmonary disease referred for evaluation of obstructive sleep apnea (OSA) had overnight polysomnography and complete echocardiographic assessment. According to the apnea hypopnea index (AHI), subjects were divided into four groups: group 1: control subjects (AHI < 5, n = 19), group 2: patients with mild OSA (AHI: 5-14, n = 21), group 3: moderate OSA (AHI: 15-30, n = 18), group 4: severe OSA (AHI > 30, n = 24). Real-time three-dimensional echocardiographic images were acquired to obtain RV regional (inflow, body and outflow) ejection fraction (EF) and time to minimum systolic volume in all subjects.

RESULTS

Body weight and body mass index were greater in the severe and moderate OSA group than those of mild and controls group (P < 0.05). There was a significant decrease in mean SaO2 and the lowest SaO2 in severe OSA when compared to other groups (P < 0.001). Inflow EF and global EF were significantly lower in moderate and severe OSA patients than in controls (P < 0.05). Inflow EF and global EF were negatively correlated with AHI (r = -0.534 and r = -0.479, respectively, P < 0.001).

CONCLUSIONS

In patients with OSA, RV inflow and global systolic function were impaired and were in inverse relationship with AHI. Evaluation of RV regional systolic function using real-time three-dimensional echocardiography may play a potential role in the noninvasive assessment of the severity of OSA.

Perioperative complications in obstructive sleep apnea patients

BACKGROUND

Perioperative complications in obstructive sleep apnea (OSA) patients are described in a small series of case reports. No study to date systematically evaluates perioperative complications in a large number of OSA patients receiving surgeries other than those involving the pharynx.

METHODS

Names of the 860 OSA patients seen in a hospital-based sleep disorders center was cross-referenced with a list of the names of the 2,350 patients receiving surgeries in hospital during an 18 month period. In-patient and sleep center records of the 57 OSA patients receiving surgery were reviewed.

RESULTS

Nine perioperative complications occurred in eight of 48 OSA patients (17%) receiving general anesthesia. All of these complications were related to difficulties with airway management both pre- and postoperatively. Clinical characteristics including body mass index and Polysomnographie measurements of OSA severity did not prove to be useful predictors of perioperative complications.

CONCLUSIONS

The incidence of respiratory complications related to difficulties in airway management in OSA patients was higher than that reported in a recent study for all patients receiving general anesthesia (4%). The perioperative complications observed in these OSA patients are consistent with the underlying pathogenesis of OSA, pharyngeal obstruction. The absence of observed perioperative arrhythmias and myocardial ischemia is consistent with previous findings that sleep-related cardiac ischemia is uncommon in OSA patients. Our results suggest it is prudent to cautiously manage all OSA patients receiving surgeries involving general anesthesia.

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.

Obstructive sleep apnea and cardiovascular disease

Obstructive sleep apnea (OSA) is a common yet an under-diagnosed sleep related breathing disorder affecting predominantly middle-aged men. OSA is associated with many adverse health outcomes, including cardiovascular disease. Common OSA associated/induced cardiovascular disorders include coronary artery disease, heart failure, hypertension, cardiac arrhythmias and stroke, which further increase morbidity and mortality in the OSA population. Endothelial dysfunction, coagulopathy, impaired sympathetic drive, oxidative and inflammatory stress are the pathophysiological pathways suggested for the development of cardiovascular disease in OSA. The evidence would suggest that OSA should be considered as a cardiovascular risk factor, and is a treatable condition. Multiple studies using Continuous Positive Airway Pressure (CPAP) have shown improvements in the clinical state as well as retardation of disease progression. Therefore, patients with cardiovascular disease should be proactively screened for OSA and vice versa.

Effects of continuous positive airway pressure therapy on right ventricular function assessment by tissue Doppler imaging in patients with obstructive sleep apnea syndrome

OBJECTIVES

The effects of continuous positive airway pressure (CPAP) therapy on right ventricular (RV) function in patients with obstructive sleep apnea syndrome (OSAS) has not been previously studied by tissue Doppler imaging (TDI). The aim of this study was to assess RV function using TDI in patients with OSAS before and after CPAP therapy.

METHODS

Twenty-eight patients with newly diagnosed OSAS in the absence of any confounding factors and 18 controls were included in this study. The peak systolic velocity (S'm), early (E'm) and late (A'm) diastolic myocardial peak velocities at tricuspid lateral annulus, isovolumic acceleration (IVA), myocardial precontraction time (PCT'm), myocardial contraction time (CT'm), and myocardial relaxation time (RT'm) were measured. All echocardiographic parameters were calculated 6 months after CPAP therapy.

RESULTS

The RV diastolic parameters such as E'm velocity and E'm-to-A'm ratio were significantly lower, RT'm was significantly prolonged, A'm velocity was similar in patients with OSAS compared to controls; and the RV systolic parameters such as IVA and CT'm were significantly lower and S'm was similar in patients with OSAS compared to controls. At the end of the treatment, 20 of 28 patients were compliant with CPAP therapy. E'm velocity, E'm-to-A'm ratio, IVA, and CT'm increased, PCT'm, PCT'm-to-CT'm ratio, and RT'm decreased significantly after therapy, whereas S'm velocity and A'm velocity did not change after CPAP treatment in the compliant patients.

CONCLUSION

OSAS is associated with RV systolic and diastolic dysfunction, and 6 months of CPAP therapy improves the RV systolic and diastolic dysfunction.

Decreased Right and Left Ventricular Myocardial Performance in Obstructive Sleep Apnea

BACKGROUND

Obstructive sleep apnea (OSA) may predispose patients to congestive heart failure (CHF), suggesting a deleterious effect of OSA on myocardial contractility.

METHODS

A cross-sectional study of 85 subjects with suspected OSA who had undergone their first overnight polysomnogram, accompanied by an echocardiographic study. Patients were divided according to the apnea-hypopnea index as follows: < 5 (control subjects); 5 to 14 (mild OSA); and >or= 15 (moderate-to-severe OSA). Right and left ventricular function was evaluated using the myocardial performance index (MPI) and other echocardiographic parameters. For the right ventricle analyses, we excluded patients with a Doppler pulmonary systolic pressure of >or= 45 mm Hg, while for the left ventricle we excluded patients with an ejection fraction of <or= 45%.

RESULTS

The mean (+/- SD) age was 60 +/- 15 years, and 83% were men. Right and left ventricular function were altered in patients with OSA, especially in those with the moderate-to-severe OSA, even after adjustment for potential confounders. The mean right MPI was 0.23 +/- 0.10 in control subjects, 0.26 +/- 0.16 in patients with mild OSA, and 0.37 +/- 0.11 in patients with moderate-to-severe OSA (p value for trend, < 0.01). The mean left MPI values were 0.28 +/- 0.05, 0.27 +/- 0.07, and 0.41 +/- 0.14, respectively (p value for trend, 0.04). Right and left MPI correlated positively and significantly with the apnea-hypopnea index (rho = 0.40, p = 0.002; and rho = 0.27, p = 0.02, respectively). Mean left atrial volume index was increased in patients with OSA (control subjects, 26.8 +/- 11; patients with mild OSA, 32.5 +/- 15; and patients with moderate-to-severe OSA, 30.4 +/- 11; p value for trend, 0.04).

CONCLUSIONS

OSA, particularly when moderate to severe, is associated with impaired right and left ventricular function and increased left atrial volume. These findings support the notion that OSA may contribute to the development of atrial fibrillation and CHF.

Effects of CPAP on right ventricular myocardial performance index in obstructive sleep apnea patients without hypertension

OBJECTIVES

Obstructive sleep apnoea (OSA) might cause right ventricular dysfunction and pulmonary hypertension. We aimed to determine the effects of nasal continuous positive airway pressure (CPAP) therapy on right ventricular myocardial performance index (MPI) in OSA patients without hypertension.

METHODS

49 subjects without hypertension, diabetes mellitus, any cardiac and pulmonary disease had overnight polysomnography and echocardiography. In 18 moderate-severe OSA (apnea-hypopnea index > or = 15) patients, right ventricular free wall diameter (RVFWD) was measured by M-mode, and right ventricular MPI was calculated as (isovolumic contraction time+ isovolumic relaxation time) / pulmonary ejection time using Doppler at baseline and after 6 months CPAP therapy.

RESULTS

Mean age was 46.5 +/- 4.9 year. Patients had high body mass index (BMI: 30.6 +/- 4,0 kg/m2), but there was no change in either BMI or blood pressures after 6 months. Right ventricular end-diastolic and end-systolic diameters were in normal limits at baseline, and did not change after CPAP usage. Baseline RVFWD (7.1 +/- 2.1 mm) significantly decreased after CPAP therapy (6.2 +/- 1.7 mm, p < 0.001). 15 of patients (83%) had right ventricular diastolic dysfunction at baseline, and it was completely improved in 11 of them (73%) by CPAP usage. Right ventricular global dysfunction was shown in 11 patients (61%) with a high MPI (62.2 +/- 9.3%) at baseline; and MPI was significantly decreased after CPAP therapy (47.3 +/- 8.4%, p < 0.0001), and it was completely corrected in 4 of them (36%).

CONCLUSION

CPAP therapy significantly decreases RVFWD and improves right ventricular diastolic and global functions (MPI) in OSA patients without hypertension.

Effect of Obstructive Sleep Apnea on Aortic Elastic Parameters

BACKGROUND

Obstructive sleep apnea (OSA) syndrome has a critical association with cardiovascular mortality and morbidity. Aortic elastic parameters are important markers for left ventricular (LV) function and are deteriorated in cardiovascular disease.

METHODS AND RESULTS

Aortic elastic parameters and LV functions and mass were investigated in 40 patients with OSA (apnea - hypopnea index (AHI) >or=5) (mean age 51.3 +/-9 years, 32 males) and 24 controls (AHI <5) (mean age 51.9+/-5.2 years, 19 males). All subjects underwent polysomnographic examination and recordings were obtained during sleep. They also underwent a complete echocardiographic examination and systolic and diastolic aortic measurements were noted from M-mode traces of the aortic root. There were no significant differences in the demographic data of the patients with OSA and the controls. Subjects with OSA demonstrated higher values of aortic stiffness (7.1+/-1.88 vs 6.42+/-1.56, p=0.0001), but lower distensibility (9.47+/-1.33 vs 11.8+/-3.36, p=0.0001) than the controls. LV ejection fraction was significantly lower in patients with OSA when compared with the control group (61.3+/-5.2% vs 65.9+/-8.4%, p=0.0001). LV diastolic parameters were also compared and were worse in the subjects with OSA than in the control subjects (mitral E/A: 0.91 +/-0.42 vs 1.35+/-0.66, p=0.001; Em/Am: 0.86+/-0.54 vs 1.23+/-0.59, p=0.021). Respiratory disturbance index had a positive correlation with aortic stiffness (r=0.63, p=0.0001 and negative correlation with distensibility (r=-0.41, p=0.001).

CONCLUSION

Aortic elastic parameters are deteriorated in OSA, which has an extremely high association with cardiovascular disease. Increased aortic stiffness might be responsible for the LV systolic and diastolic deterioration in OSA syndrome.

Impact of obstructive sleep apnea on right ventricular global function: sleep apnea and myocardial performance index

BACKGROUND

Obstructive sleep apnea (OSA) is characterized by repetitive upper airway obstructions during sleep, and it might cause cardiovascular complications such as heart failure, arrhythmias, myocardial infarction, systemic and pulmonary hypertension.

OBJECTIVES

To determine right ventricular diameters and myocardial performance index (MPI) reflecting ventricular global function in uncomplicated OSA patients.

METHODS

49 subjects without hypertension, diabetes mellitus, or any cardiac or pulmonary disease referred for evaluation of OSA had overnight polysomnography and complete echocardiographic assessment. According to the apnea-hypopnea index (AHI), subjects were divided into three groups: group 1: control subjects (AHI <5, n = 20), group 2: patients with mild OSA (AHI: 5-14, n = 11), and group 3: moderate-severe OSA (AHI > or = 15, n = 18). Right ventricular free wall diameter was measured by M mode, and right ventricular MPI was calculated as (isovolumic contraction time + isovolumic relaxation time)/pulmonary ejection time.

RESULTS

There were no differences of age, body mass index, heart rates, systolic and diastolic blood pressures among the groups (p > 0.05). Right ventricular end-diastolic and end-systolic diameters were not statistically different between the groups, and were within normal limits. Also, right ventricular free wall diameter was not significantly different between the groups of control, mild OSA and moderate-severe OSA (6.7 +/- 0.9, 6.9 +/- 1.0, 7.1 +/- 1.1 mm, p > 0.05). Right ventricular diastolic dysfunction was shown only in group 3 patients. Right ventricular MPI was statistically higher in group 3 (0.62 +/- 0.18) than in group 2 patients (0.50 +/- 0.10), and group 1 patients (0.48 +/- 0.08, p < 0.001).

CONCLUSIONS

It was suggested that patients with moderate-severe OSA had a right ventricular global dysfunction, in addition to the presence of a diastolic dysfunction.

Obstructive Sleep Apnea Syndrome Affects Left Ventricular Diastolic Function

Background— The purpose of this study was to determine the role of obstructive sleep apnea syndrome (OSAS) as an independent risk factor for the development of left ventricular diastolic abnormalities. Moreover, we tested the hypothesis that nasal continuous positive airway pressure (nCPAP) improves such alterations in OSAS patients by eliminating apneic events.

Methods and Results— In this prospective, randomized, placebo-controlled, double-blind crossover study, 27 consecutive newly diagnosed middle-aged OSAS men with neither controllable factors nor conditions affecting left ventricular diastolic function and 15 healthy control subjects were selected. OSAS patients were randomized to 12 weeks on sham nCPAP and 12 weeks on effective nCPAP application. Echocardiographic parameters, blood pressure recordings, and urinary catecholamine levels were obtained at baseline and after both treatment modalities. At baseline, an abnormal left ventricular filling pattern was present in 15 of the 27 OSAS patients and only in 3 of the 15 control subjects ( P =0.020). Impaired relaxation was by far the most common abnormal pattern in both groups (11 and 3 patients, respectively). In OSAS patients, 12 weeks on effective nCPAP induced a significant increase in E/A ratio ( P <0.01), as well as reductions in mitral deceleration ( P <0.01) and isovolumic relaxation ( P <0.05) times.

Conclusions— OSAS can affect left ventricular diastolic function independently of other possible factors. Chronic application of nCPAP could avoid the progression of diastolic abnormalities, and indeed, it might reverse these alterations, at least in the initial stages before severe structural changes can be developed.

[Functional dynamics of the right ventricle and pulmonary circulation in obstructive sleep apnea. Therapeutic consequences]

Obstructive sleep apnea (OSA) is common with an incidence of at least 500,000 patients in the German population. Typical symptoms are daytime sleepiness, headache in the morning, and snoring. Presumably obstructive sleep apnea via various mechanisms increases cardiovascular morbidity. Hypoxemia causes nocturnal hypertension in most of the patients. Nevertheless, about 20% of the patients develop daytime pulmonary hypertension and right heart dysfunction. Clinical and animal studies demonstrated right ventricular hypertrophy as a consequence of intermittent hypoxemia and pulmonary hypertension. Right ventricular hemodynamics differ essentially from left ventricular hemodynamics. Right ventricular function is substantially influenced by right ventricular afterload, which is mainly determined by pulmonary vascular resistance, and slightly influenced by preload. Application of continuous positive airway pressure (CPAP) via a nose mask normalizes nocturnal breathing disorders and reduces pre- and afterload, especially in patients with cardiomegaly. Therefore, CPAP generates positive effects on the myocardium.

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.

Echocardiographic parameters in adolescents with sleep-related breathing disorders

Few data are known about the effects of sleep-related breathing disorders (SRBD) on the cardiovascular system in adolescents. Forty healthy adolescents (mean age, 13.7 +/- 1.6 years) answered a questionnaire regarding symptoms of sleep-related breathing disorders (SRBD) and underwent a cardiorespiratory polygraphy and echocardiography. Echocardiographic data in snorers with polygraphic abnormalities suggestive of SRBD (positive group, n = 29) were compared with the results in nonsnorers without polygraphic abnormalities (n = 11) who were included in the control group. Ventricular dimensions and indices of left ventricular systolic function were within normal limits and were not significantly different between the two groups. Indices of left ventricular diastolic function were also within normal limits, but isovolumetric relaxation time (IVRT) was significantly longer among the positive group (72.5 +/- 8.4 msec) than among the controls (65.1 +/- 7.9 msec) (P = 0.018). Multiple regression analysis showed that posterior wall thickness was predicted by a model that included cardiac events related with respiratory events and/or desaturations, and respiratory disturbance index (RDI) in supine position. Deceleration of early diastolic flow was predicted by RDI, percentage of total recording time with SaO(2) < 90% (CT(90)), and age; the variability of isovolumetric relaxation time was predicted by a model that included RDI in supine position. We found a significant relationship between polygraphic parameters suggestive of SRBD and echocardiographic measurements of ventricular dimensions and diastolic function. Also, echocardiographic parameters suggestive of some degree of left ventricular diastolic dysfunction were found in snoring adolescents with polygraphic abnormalities.

Left ventricular systolic dysfunction in patients with obstructive sleep apnea syndrome

STUDY OBJECTIVES

Conflicting results have been reported regarding the effects of obstructive sleep apnea syndrome (OSAS) on daytime left ventricular (LV) systolic function. This study aimed to assess the prevalence and causes of LV systolic dysfunction, using radionuclide angiography, in a large group of patients with OSAS.

DESIGN AND SETTING

A prospective study in the pneumology department of a university medical center.

PATIENTS

One hundred sixty-nine consecutive patients with OSAS diagnosed by polysomnography, hospitalized for the administration of nasal continuous positive airway pressure. Patients with a known cardiac disease were excluded.

MEASUREMENTS

LV ejection fraction (LVEF) was measured in all patients, using radionuclide ventriculography with multiple-gated equilibrium cardiac imaging. Myocardial scintigraphy with a dipyridamole stress test and echocardiography were performed in those patients with LV systolic dysfunction, defined by a LVEF < 50%, to detect silent heart disease, especially coronary artery disease.

RESULTS

LV systolic dysfunction was observed in 7.7% (13 of 169 patients). In these 13 patients, the mean +/- SD LVEF was 42 +/- 6%, the lowest value of LVEF was 32%, and no silent cardiac disease was revealed. Age, body mass index, apnea-hypopnea index, parameters of nocturnal oxyhemoglobin desaturation, and prevalence of systemic hypertension did not significantly differ between patients with LVEF < 50% and those with LVEF > 50%. In seven patients with LV dysfunction, LVEF was measured following treatment of OSAS and reached normal values.

CONCLUSION

OSAS may be a direct cause of daytime LV systolic dysfunction that can resolve following reversal of nocturnal apneas.

Cardiovascular consequences of sleep-related breathing disorders

Sleep-related breathing disorders (SRBDs) represent a spectrum of abnormalities that range from simple snoring to upper airway resistance syndrome to sleep apnea. The clinical presentation may include obesity, snoring, neuropsychological dysfunction, and daytime hypersomnolence and tiredness. The acute hemodynamic alterations of obstructive sleep apnea include systemic and pulmonary hypertension, increased right and left ventricular afterload, and increased cardiac output. Earlier reports attributed the coexistence of SRBDs with cardiovascular diseases to the shared risk factors such as age, sex, and obesity. However, recent epidemiologic data confirm an independent association between SRBDs and the different manifestations of cardiovascular diseases. Possible mechanisms may include a combination of intermittent hypoxia and hypercapnia, repeated arousals, sustained increase in sympathetic tone, reduced baroreflex sensitivity, increased platelet aggregation, and elevated plasma fibrinogen and homocysteine levels. The strength of the association, its pathogenesis, and the impact of treatment of SRBDs on the health outcome of patients with cardiovascular diseases are issues to be addressed in future studies.

Pulmonary haemodynamics in obstructive sleep apnoea

In patients with obstructive sleep apnoea syndrome (OSAS), pulmonary haemodynamics can show both transient perturbations during sleep and permanent alterations. During sleep, repeated fluctuations in pulmonary artery pressure and pulmonary wedge pressure, coincident with apnoeas, can be observed. Calculation of transmural pressure values is preferable to intravascular pressures in OSAS, due to the marked swings in intrathoracic pressure associated with obstructive apnoeas. Pulmonary artery pressure may progressively increase during sleep, particularly in close sequences of highly desaturating apnoeas. Apnoea-induced hypoxia appears as the most important determinant of this pulmonary artery pressure behaviour. Stroke volume and cardiac output during obstructive apnoeas show changes mainly related to intrathoracic pressure variations. Permanent precapillary pulmonary hypertension at rest is observed in <50% OSAS patients, and is poorly reversible after OSAS treatment. It correlates best with diurnal respiratory function parameters. However, the finding of pulmonary hypertension in some patients with near normal diurnal lung function led to suggest that sleep respiratory disorders may contribute to permanent pulmonary haemodynamic impairment in predisposed subjects. Knowledge on right ventricle hypertrophy in OSAS is inconsistent. As to right ventricle failure, it is clinically evident in subjects with associated lung disease or morbid obesity, while it may be detected instrumentally in subjects without such alterations, presumably as effect of apnoeas themselves. Besides, it appears more fully reversible after long-term OSAS treatment than pulmonary hypertension.

Severe obstructive sleep apnea is associated with left ventricular diastolic dysfunction

INTRODUCTION

Hypertension is common in patients with obstructive sleep apnea (OSA). However, the effect of OSA on ventricular function, especially diastolic function, is not clear. Therefore, we have assessed the prevalence of diastolic dysfunction in patients with OSA and the relationship between diastolic parameters and severity of OSA.

METHODS

Sixty-eight consecutive patients with OSA confirmed by polysomnography underwent echocardiography. Diastolic function of the left ventricle was determined by transmitral valve pulse-wave Doppler echocardiography. Various baseline characteristics, severity of OSA, and echocardiographic parameters were compared between patients with and without diastolic dysfunction.

RESULTS

There were 61 male and 7 female patients with a mean age of 48.1 +/- 11.1 years, body mass index of 28.5 +/- 4.3 kg/m(2), and apnea/hypopnea index (AHI) of 44.3 +/- 23.2/h (mean +/- SD). An abnormal relaxation pattern (ARP) in diastole was noted in 25 patients (36.8%). Older age (52.7 +/- 8.9 years vs 45.1 +/- 11.3 years, p = 0.005), hypertension (56% vs 20%, p = 0.002), and a lower minimum pulse oximetric saturation (SpO(2)) during sleep (70.5 +/- 17.9% vs 78.8 +/- 12.9%, respectively; p = 0.049) were more common in patients with ARP. By multivariate analysis, minimum SpO(2) < 70% was an independent predictor of ARP (odds ratio, 4.34; 95% confidence interval, 1.23 to 15.25; p = 0.02) irrespective of age and hypertension. Patients with AHI > or = 40/h had significantly longer isovolumic relaxation times than those with AHI < 40/h (106 +/- 19 ms vs 93 +/- 17 ms, respectively; p = 0.005).

CONCLUSION

Diastolic dysfunction with ARP was common in patients with OSA. More severe sleep apnea was associated with a higher degree of left ventricular diastolic dysfunction in this study.

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

OBJECTIVES

We investigated whether the severity of obstructive sleep apnea (OSA) predicts blood pressure or cardiac left ventricular thickness in a clinical population of OSA patients, if adjustments are made for age, gender, use of antihypertensive agents, smoking, body mass index, history of coronary artery disease, hypercholesterolemia and circulating C-peptide concentrations.

DESIGN

Relationships in this cross-sectional study were investigated with correlation analysis and multiple regression procedures.

PATIENTS AND METHODS

Apnea-hypopnea index (AHI, polysomnography) and office systolic and diastolic blood pressures (SBP and DBP) were measured in 81 subjects referred to a university hospital sleep laboratory. Ambulatory blood pressures were recorded during one 24 h cycle. Left ventricular (LV) muscle size was quantified as two-dimensionally directed M-mode-derived end-diastolic thickness of interventricular septum and posterior chamber wall.

RESULTS

After adjustment for separate or the entire set of covariates, AHI predicted office SBP and DBP as well as daytime ambulatory DBP and night-time ambulatory SBP and DBP, but not daytime ambulatory SBP. In contrast, associations between AHI and LV muscle thickness reflected complex inter-relationships with confounding variables. Smoking and age suppressed, whereas body mass index (BMI) and hypertension inflated the relationship between OSA severity and LV muscle thickness in this study.

CONCLUSIONS

AHI is an independent predictor of several measures of blood pressure. OSA severity and LV muscle thickness appear to be primarily linked via increased blood pressure.

Echocardiographic features of the right heart in sleep-disordered breathing: the Framingham Heart Study

The effect of sleep-disordered breathing (SDB) on right heart structure and function is controversial. Studies of patients referred for evaluation of possible sleep apnea have yielded conflicting results, and the impact of SDB on the right heart has not been investigated in the general population. We examined the echocardiographic features of subjects with SDB at the Framingham Heart Study site of the Sleep Heart Health Study. Of 1,001 polysomnography subjects, 90 with SDB defined as a respiratory disturbance index (RDI) score > 90th percentile (mean RDI = 42) were compared with 90 low-RDI subjects (mean RDI = 5) matched for age, sex, and body mass index. Right heart measurements, made without knowledge of clinical status, were compared between groups. The majority of the subjects were male (74%). After multivariable adjustment, right ventricle (RV) wall thickness was significantly greater (p = 0.005) in subjects with SDB (0.78 +/- 0.02 cm) than in the low-RDI subjects (0.68 +/- 0.02 cm). Right atrial dimensions, RV dimensions, and RV systolic function were not found to be significantly different between subjects with SDB and the low-RDI subjects. We conclude that in this community-based study of SDB and right heart echocardiographic features, RV wall thickness was increased in subjects with SDB. Whether the RV hypertrophy observed in persons with SDB is associated with increased morbidity and mortality remains unknown.

Impact of obstructive sleep apnea on left ventricular mass and diastolic function

We wished to determine if obstructive sleep apnea (OSA) is associated with increased left ventricular mass (LVM) and impaired left ventricular diastolic function (LVDF) independently of coexisting obesity, hypertension (HTN), and diabetes mellitus (DM). Patients without primary cardiac disease, referred for evaluation of OSA (n = 533), had overnight polysomnography and Doppler echocardiography while awake. Patients were divided, according to the apnea-hypopnea index (AHI), into an OSA group (AHI > or = 5/h, n = 353) and a non-OSA group (AHI < 5/h, n = 180). In men, LVM was greater in the OSA group (98.9 +/- 25.6 versus 92.3 +/- 22.5 g/m, p = 0.023) despite exclusion of those with HTN and DM. A similar trend was noted in women. Regression analysis revealed that LVM was correlated with body mass index (BMI) (beta = 0.480, p < 0.0005), age (beta = 0.16, p = 0.001), and the presence of HTN (beta = 0.137, p = 0.003) in men and with BMI (beta = 0.501, p < 0.0005) in women, but not with AHI or oxygen saturation during sleep. The ratio of peak early filling velocity to peak late filling velocity (E/A), an index of LVDF, was similar in both groups (1.28 +/- 0.32 versus 1.34 +/- 0.31, p = 0.058); it was correlated with age (beta = -0.474, p < 0.0005), but not with AHI or oxygen saturation during sleep. We conclude that OSA is not associated with increased LVM or impaired LVDF independently of obesity, HTN, or advancing age.

Impairment of vascular endothelial function and left ventricular filling : association with the severity of apnea-induced hypoxemia during sleep

STUDY OBJECTIVE

To investigate whether a dose-effect relationship exists between the severity of obstructive sleep apnea (OSA) and subclinical indicators of myocardial or vascular dysfunction.

DESIGN

Cross-sectional study using correlation analysis.

PARTICIPANTS

Twenty subjects referred to our sleep laboratory for screening or therapy of OSA but without regular medication and without known cardiovascular disease.

MEASUREMENTS

Severity of OSA was quantified by polysomnography. Moreover, nocturnal excretion of norepinephrine was determined. Left ventricular (LV) myocardial function was assessed with Doppler echocardiography. Using ultrasonographic measurements, endothelium-dependent and endothelium-independent conduit artery dilation were measured as flow-mediated and glyceryltrinitrate-induced changes in brachial artery diameter.

RESULTS

Worsening nocturnal hypoxemia, measured as nocturnal oxygen saturation nadir or percentage of sleep time spent in hypoxemia (< 90% hemoglobin oxygen saturation), predicted increased interventricular septum thickness (corrected for age and body mass index), prolonged isovolumetric relaxation time, decreased ratio between peak early and late mitral flow velocities, as well as reduced endothelium-dependent dilatory capacity of the brachial artery (all relationships corrected for cofactor age and with p < 0.05) were observed. Associations between these cardiovascular function markers and nocturnal excretion of norepinephrine followed the same trend, but relations with interventricular septum thickness and flow-mediated artery dilation missed significance (p = 0.064 and p = 0.061, respectively). LV posterior wall thickness, measures of LV systolic function, early mitral flow deceleration time, and endothelium-independent artery dilation were not significantly related to the degree of nocturnal hypoxemia or norepinephrine excretion. None of the correlations with apnea-hypopnea index were statistically significant.

CONCLUSIONS

The severity of apnea-related hypoxemia is associated with a gradual deterioration of LV diastolic function as well as large-artery endothelial function.

Chronic intermittent hypoxia increases haematocrit and causes right ventricular hypertrophy in the rat

Chronic continuous hypoxia increases haematocrit and causes right ventricular hypertrophy and pulmonary hypertension. In obstructive sleep apnoea, the exposure to hypoxia is intermittent rather than continuous but the effects of chronic intermittent hypoxia on haematocrit and right ventricular mass are unclear. Wistar rats were exposed to alternating periods of hypoxia and normoxia twice per min for 8 h per day for 5 weeks in order to mimic the intermittent hypoxia of obstructive sleep apnoea in humans. Haematocrit was significantly raised at day 7, 14, 21, 28 and 35 of the treatment period. At the end of the treatment, there was a significant increase in right ventricular mass. Therefore, chronic intermittent hypoxia increases haematocrit and right heart mass. These results suggest that the raised haematocrit and pulmonary arterial pressure observed in some cases of obstructive sleep apnoea in humans may be caused by intermittent nocturnal hypoxaemia.

Sleep-related breathing disorders. 4. Consequences of sleep disordered breathing

Images

Obstructive sleep apnea and blood pressure elevation: what is the relationship? Working Group on OSA and Hypertension

Sleep disordered breathing has increasingly been recognised as a frequent cause of ill-health in the community. Moderate or severe forms of the most common condition, obstructive sleep apnea (OSA), occur in up to 12% of the adult male population. A substantial body of literature has been published on the potential relationship between OSA and cardiovascular disease. In particular, OSA has been associated with cardiac failure, stroke, myocardial infarction and hypertension. Part of this association may be explained by other confounders, mainly obesity, which is common in OSA patients. The present review was prepared following a workshop aimed to critically review available scientific evidence suggesting that hypertension is a direct consequence of OSA. In addition, pathophysiologic mechanisms that may be involved in the relationship between OSA and cardiovascular disease, particularly brief intermittent elevation of blood pressure and sustained systemic hypertension, are discussed.