Cardiac hypertrophy in obstructive sleep apnea syndrome

The incremental effect of obstructive sleep apnea syndrome on right and left ventricular myocardial performance in newly diagnosed essential hypertensive subjects

Obstructive sleep apnea syndrome (OSAS) may predispose patients to congestive heart failure, suggesting a deleterious effect of OSAS on myocardial contractility. We investigated whether essential hypertensive individuals with OSAS are characterized by decreased right and left ventricular myocardial performance. Our study population consisted of 45 consecutive patients with newly diagnosed untreated stage I-II essential hypertension suffering from OSAS (35 men, aged 49+/-8 years) and 48 hypertensives without OSAS, matched for age, sex, level of blood pressure, heart rate, body mass index and smoking status. All subjects underwent polysomnography and echocardiography. Right and left ventricular functions were evaluated using the myocardial performance index (MPI). Right and left ventricular functions were altered in hypertensives with OSAS. The mean right MPI was 0.26+/-0.11 in hypertensives without OSAS and 0.51+/-0.16 in hypertensives with OSAS (P<0.01). The mean left MPI values were 0.29+/-0.07 and 0.44+/-0.13, respectively (P<0.01). Right and left MPI correlated positively and significantly with apnea-hypopnea index (rho=0.40, P=0.002).OSAS is associated with impaired right and left ventricular function. These phenomena were independent of hypertension.

Obstructive sleep apnoea and its cardiovascular consequences

Obstructive sleep apnoea (OSA) is a common disorder in which repetitive apnoeas expose the cardiovascular system to cycles of hypoxia, exaggerated negative intrathoracic pressure, and arousals. These noxious stimuli can, in turn, depress myocardial contractility, activate the sympathetic nervous system, raise blood pressure, heart rate, and myocardial wall stress, depress parasympathetic activity, provoke oxidative stress and systemic inflammation, activate platelets, and impair vascular endothelial function. Epidemiological studies have shown significant independent associations between OSA and hypertension, coronary artery disease, arrhythmias, heart failure, and stroke. In randomised trials, treating OSA with continuous positive airway pressure lowered blood pressure, attenuated signs of early atherosclerosis, and, in patients with heart failure, improved cardiac function. Current data therefore suggest that OSA increases the risk of developing cardiovascular diseases, and that its treatment has the potential to diminish such risk. However, large-scale randomised trials are needed to determine, definitively, whether treating OSA improves cardiovascular outcomes.

No evidence of enhanced oxidant production in blood obtained from patients with obstructive sleep apnea

Background

Obstructive sleep apnea syndrome (OSAS) is a recognized risk factor for cardiovascular morbidity and mortality, perhaps due to causative exacerbations of systemic oxidative stress. Putative oxidative stress related to numerous episodes of intermittent hypoxia, may be an oxidants chief driving force in OSAS patients.

Methods

We assessed the resting and n-formyl-methionyl-leucyl-phenylalanine (fMLP)- induced whole blood chemiluminescence (as a measure of oxidant production by polymorphonuclear leukocytes and monocytes), ferric reducing ability of plasma (FRAP) and H₂O₂ generation in the whole blood of 27 untreated OSAS patients, 22 subjects after a night of CPAP therapy and 11 controls without OSAS. All of them were matched to age, BMI (body mass index) and smoking habits. All parameters were measured before and after polysomnography-controlled sleep, individual results were obtained as a mean from duplicated experiments.

Results

No significant differences were distinguished between evening and morning blood chemiluminescence, H₂O₂ activity and FRAP within and between all three study groups.

For instance patients with untreated OSAS had similar morning and evening resting whole blood chemiluminescence (2.3 +/- 2.2 vs. 2.4 +/- 2.2 [aU·10^-4 phagocytes]), total light emission after stimulation with fMLP (1790 +/- 1371 vs. 1939 +/- 1532 [aU·s·10^-4 phagocytes]), as well as FRAP after 3 min. plasma incubation (602 +/- 202 vs. 671 +/- 221 [uM]). Although, in the subgroup of 11 patients with severe OSAS (apnea/hypopnea index 58 +/- 18/h and oxygen desaturation index 55 +/- 19/h), the morning vs. evening resting chemiluminescence and total light emission after stimulation with fMLP observed a propensity to elevate 2.5 +/- 2.7 vs. 1.9 +/- 1.8 [aU·10^-4 phagocytes] and 1778 +/- 1442 vs. 1503 +/- 1391 [aU·s·10^-4 phagocytes], respectively, these did not attain statistical significance (p > 0.05).

Conclusion

Our investigation exposed no evidence in the overproduction of oxidants via circulating phagocytes, once considered a culprit in the oxidative stress of OSAS patients.

Effects of continuous positive airway pressure therapy on left ventricular function assessed by tissue Doppler imaging in patients with obstructive sleep apnoea syndrome

AIMS

In this study, we aimed to assess left ventricular (LV) systolic and diastolic functions by tissue Doppler imaging (TDI) in patients with obstructive sleep apnoea syndrome (OSAS) and to investigate the effects of 6 month continuous positive airway pressure (CPAP) on LV systolic and diastolic functions.

METHODS AND RESULTS

We studied 28 new diagnosed moderate and severe OSAS patients (apnoea-hypopnoea index >15) and 18 control group. Exclusion criteria were the presence of structural heart disease, pulmonary disease, diabetes mellitus, dyslipidaemia, alcoholism, neuromuscular disease, renal failure, or malignancy. They were not previously considered or treated for OSA and were all free of drugs. Left ventricular lateral and septal wall early myocardial peak velocity (Em), late myocardial peak velocity (Am), Em to Am ratio, myocardial relaxation time (RTm), myocardial systolic wave (Sm) velocity, isovolumic acceleration (IVA), myocardial pre-contraction time (PCTm), contraction time (CTm), and PCTm to CTm ratio were measured. All echocardiographic parameters were calculated 6 months after CPAP therapy. No statistically significant difference was detected between the groups according to age, gender, body mass index, systolic and diastolic blood pressure, heart rate, fasting blood glucose, and serum lipid parameters. Left ventricular systolic parameters, such as LV septal and lateral wall IVA, CTm, and PCTm to CTm ratio, were significantly lower and Sm was similar in patients with the OSAS group compared with the controls. Left ventricular diastolic parameters, such as LV septal and lateral wall Em velocity and Em to Am ratio, were significantly lower; RTm was significantly prolonged; and Am velocity was similar in patients with OSAS compared with the controls. At the end of the treatment, 20 of 28 patients were compliant with CPAP therapy. Left ventricular septal and lateral wall Em velocity, Em to Am ratio, IVA and CTm, and PCTm to CTm increased significantly, PCTm, PCTm to CTm ratio, and RTm decreased significantly after the therapy, whereas Sm velocity and Am velocity did not change after CPAP therapy in compliant patients.

CONCLUSION

Left ventricular systolic and diastolic dysfunctions were determined in patients with OSAS, and it was demonstrated that LV systolic and diastolic dysfunctions improved with 6 month CPAP therapy.

Aortic pressure augmentation as a marker of cardiovascular risk in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is associated with increases in cardiovascular morbidity and mortality. Vascular changes in individuals with OSAS have not been fully elucidated, however. The possible impact of OSAS on the extent of aortic pressure augmentation (AG), an indicator of cardiovascular risk, was investigated. Forty-five consecutive male patients aged 35 to 78 years (56.0+/-9.6 years) who were referred to the sleep clinic of Nagoya University Hospital for screening and treatment of OSAS and 71 age-matched healthy men were enrolled in the study. AG was derived from the pressure waveform measured at the radial artery by applanation tonometry. The number of apnea and hypopnea episodes per hour (apnea-hypopnea index [AHI]) was determined by standard polysomnography. AG was significantly greater in OSAS patients than in controls (9.0+/-4.1 vs. 6.4+/-3.4 mmHg, p<0.001), and it was significantly reduced in 19 OSAS patients treated with continuous positive airway pressure. AG was also significantly correlated with the AHI (r=0.562, p<0.001) and age (r=0.356, p=0.016) but not with the serum concentrations of low and high density lipoprotein-cholesterol, triglyceride, or glycosylated hemoglobin. Stepwise multiple regression analysis revealed that the AHI was the most significant contributing factor to the increased AG in OSAS patients (beta=0.109, r=0.530, p<0.001). OSAS may thus have an adverse effect on vascular function that can be ameliorated by appropriate treatment.

Cardiac remodeling in obesity

The dramatic increase in the prevalence of obesity and its strong association with cardiovascular disease have resulted in unprecedented interest in understanding the effects of obesity on the cardiovascular system. A consistent, but puzzling clinical observation is that obesity confers an increased susceptibility to the development of cardiac disease, while at the same time affording protection against subsequent mortality (termed the obesity paradox). In this review we focus on evidence available from human and animal model studies and summarize the ways in which obesity can influence structure and function of the heart. We also review current hypotheses regarding mechanisms linking obesity and various aspects of cardiac remodeling. There is currently great interest in the role of adipokines, factors secreted from adipose tissue, and their role in the numerous cardiovascular complications of obesity. Here we focus on the role of leptin and the emerging promise of adiponectin as a cardioprotective agent. The challenge of understanding the association between obesity and heart failure is complicated by the multifaceted interplay between various hemodynamic, metabolic, and other physiological factors that ultimately impact the myocardium. Furthermore, the end result of obesity-associated changes in the myocardial structure and function may vary at distinct stages in the progression of remodeling, may depend on the individual pathophysiology of heart failure, and may even remain undetected for decades before clinical manifestation. Here we summarize our current knowledge of this complex yet intriguing topic.

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.

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.

Obstructive sleep apnea, hypertension, and their interaction on arterial stiffness and heart remodeling

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) and hypertension are independently associated with increased stiffness of large arteries that may contribute to left ventricular (LV) remodeling. We sought to investigate the impact of OSA, hypertension, and their association with arterial stiffness and heart structure.

DESIGN

We studied 60 middle-aged subjects classified into four groups according to the absence or presence of severe OSA with and without hypertension. All participants were free of other comorbidities. The groups were matched for age, sex, and body mass index.

MEASUREMENTS AND RESULTS

Full polysomnography, pulse-wave velocity (PWV), and transthoracic echocardiography were performed in all participants. Compared with normotensive subjects without OSA, PWV, left atrial diameter, interventricular septal thickness, LV posterior wall thickness, LV mass index, and percentage of LV hypertrophy had similar increases in normotensive OSA and patients with hypertension and no OSA (p < 0.05 for all comparisons), with a significant further increase in PWV, LV mass index, and percentage of LV hypertrophy in subjects with OSA and hypertension. Multivariate regression analysis showed that PWV was associated with systolic BP (p < 0.001) and apnea-hypopnea index (p = 0.002). The only independent variable associated with LV mass index was PWV (p < 0.0001).

CONCLUSIONS

Severe OSA and hypertension are associated with arterial stiffness and heart structure abnormalities of similar magnitude, with additive effects when both conditions coexist. Increased large arterial stiffness contributes to ventricular afterload and may help to explain heart remodeling in both OSA and hypertension.

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.

Prevalence of left ventricular hypertrophy in persons with and without obstructive sleep apnea

We investigated the prevalence of left ventricular hypertrophy (LVH) in persons with and without obstructive sleep apnea (OSA). Fifty-three persons had a nocturnal polysomnogram to diagnose OSA and 2-dimensional echocardiograms to measure left ventricular mass. OSA was considered mild if the respiratory disturbance index (RDI) was 5 to 15, moderate if the RDI was 15 to 30, and severe if the RDI was >30. LVH was diagnosed if the left ventricular mass index was >110 g/m in women and >134 g/m in men. LVH was present in 21 of 27 persons (78%) with moderate or severe OSA, in 6 of 13 persons (46%) with mild OSA, and in 3 of 13 persons (23%) with no OSA (P < 0.001 comparing moderate or severe OSA with no OSA and P < 0.05 comparing moderate or severe OSA with mild OSA). OSA was a significant independent predictor of LVH after controlling the confounding effects of hypertension with an odds ratio of 3.579 (95% confidence interval, 1.589-8.058).

Left Ventricular Structural Adaptations to Obstructive Sleep Apnea in Dilated Cardiomyopathy

RATIONALE AND OBJECTIVES

Obstructive sleep apnea is common among patients with heart failure and exposes the left ventricle to trophic mechanical and adrenergic stimuli. We hypothesized that in heart failure patients with nonischemic dilated cardiomyopathy (a condition characterized by eccentric hypertrophy), those with obstructive sleep apnea would have a higher prevalence of left ventricular hypertrophy by wall thickness criteria (> or = 12 mm), and greater septal thickness than those without obstructive sleep apnea.

METHODS AND RESULTS

We performed echocardiography and polysomnography in 47 patients with nonischemic dilated cardiomyopathy. Obstructive sleep apnea was present in 45% of these patients. The prevalence of left ventricular hypertrophy was greater in those with than in those without obstructive sleep apnea (47.6 vs. 15.4%, p = 0.016). Interventricular septal thickness (p < 0.001) and relative wall thickness (p = 0.011) were significantly greater in those with than in those without obstructive sleep apnea. However, there was no significant difference in posterior wall thickness between the groups. The frequency of obstructive apneas and hypopneas during sleep was the only significant independent correlate of septal thickness (p = 0.001).

CONCLUSIONS

In patients with nonischemic dilated cardiomyopathy, the presence of obstructive sleep apnea is associated with an increased prevalence of left ventricular hypertrophy. The higher relative wall thickness and interventricular septal thickness in patients with obstructive sleep apnea indicate that the left ventricle is relatively less eccentric than in patients without obstructive sleep apnea, and that such remodeling affects mainly the septum. These structural adaptations may reflect unique nocturnal mechanical and adrenergic stimuli associated with obstructive sleep apnea.

Assessment of continuous positive airway pressure treatment in obstructive sleep apnea syndrome using 24-hour urinary catecholamines

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is related to diurnal sympathetic hyperactivity and increased blood pressure, both factors that are likely to lead to the development of cardiovascular disease.

HYPOTHESIS

The study investigated whether 24-h urinary catecholamines would reflect the effect of obstructive sleep apnea on autonomic activity.

METHODS

Standard polysomnography was performed in 17 patients with OSAS (age 53.7 +/- 13.5 years, mean +/- standard deviation). The number of apnea/hypopnea episodes per hour of sleep (apnea/hypopnea index [AHI]); number of oxygen desaturation episodes per hour (desaturation index [DSI]); arousals per hour (arousal index); lowest oxygen saturation (lowest SpO2); and percentages of stages 1, 2, 3/4, and rapid eye movement sleep (% stage 1, -2, and -3/4, and % REM, respectively) were measured. Overnight continuous positive airway pressure (CPAP) titration was performed the night after the baseline sleep measurements had been taken. Twenty-four-hour urinary adrenaline and noradrenaline were also examined.

RESULTS

During the CPAP treatment, both 24-h urinary adrenaline and noradrenaline were significantly lower compared with natural sleep. Continuous positive airway pressure significantly decreased the AHI, DSI, % stage 1, and arousal index and significantly increased the lowest SpO2. There were no significant differences in % stage 2, % stage 3/4, and % REM between before and during CPAP treatment. Multiple analysis of covariance tests revealed that lowest SpO2 was the most important factor for increasing 24-h urinary noradrenaline levels (F = 4.75, p = 0.048).

CONCLUSIONS

One night CPAP treatment could improve autonomic dysfunction. The assessment of 24-h urinary noradrenaline would provide important information for evaluating the effect of CPAP treatment.

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.

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.

Associated Factors to Predict Outcomes of Uvulopharyngopalatoplasty Plus Genioglossal Advancement for Obstructive Sleep Apnea

OBJECTIVES

This study aimed to evaluate the effectiveness of uvulopharyngopalatoplasty (UPPP) plus genioglossal advancement (GA) for severe obstructive sleep apnea (OSA) patients and to determine the predictive factors for surgical success.

STUDY DESIGN

Prospective case series.

METHODS

Patients with apnea-hypopnea index greater than 40/hour during an overnight sleep study and who were reluctant to receive nasal continuous positive airway pressure (nCPAP) therapy were included. Basic data were obtained along with physical examination, cephalometric measurements, and Epworth Sleepiness Score (ESS) questionnaire. All patients received UPPP plus GA under general anesthesia. Overnight sleep study was repeated at least 3 months after operation along with cephalometry and ESS questionnaire.

RESULTS

Forty-four patients with severe OSA were enrolled in this study. The overall success rate was 52.3%. Preoperative apnea index (AI) was the only significant predictor for the success of operation (P = .007). Furthermore, patients with AI less than 25/hour had a higher success rate than those with AI 25/hour or greater (odds ratio 13.1).

CONCLUSION

Patients with AI less than 25/hour unwilling to receive nCPAP therapy could be more suitable for UPPP plus GA in terms of the success rate.

Heart failure and sleep apnoea: to sleep perchance to dream

Heart failure and sleep apnoea are major health problems with an increasingly recognized association; evidence suggests that sleep apnoea may play a role in the progression of heart failure. However, confounding factors such as obesity, hypertension and coronary heart disease make this relationship uncertain and an independent correlation remains unproven. Diagnosis of sleep apnoea is suboptimal, as it is often asymptomatic and polysomnography is expensive and time-consuming. A simple and reliable screening protocol is required. All heart failure patients should be considered to be at high risk of sleep apnoea, as this association might be linked to adverse outcome. Continuous positive airway pressure has shown some beneficial effects, but long-term outcome and improvement in survival remains to be demonstrated. Despite recent advances in the understanding of the complex relationship between heart failure and sleep apnoea, there are a number of areas requiring further investigation, which may have important implications for the management and prognosis of a significant number of patients.

Acute and chronic cardiovascular effects of intermittent hypoxia in C57BL/6J mice

We investigated the effects of 1) acute hypoxia and 2) 5 wk of chronic intermittent hypoxia (IH) on the systemic and pulmonary circulations of C57BL/6J mice. Mice were chronically instrumented with either femoral artery or right ventricular catheters. In response to acute hypoxia (4 min of 10% O2; n = 6), systemic arterial blood pressure fell (P < 0.005) from 107.7 +/- 2.5 to 84.7 +/- 6.5 mmHg, whereas right ventricular pressure increased (P < 0.005) from 11.7 +/- 0.8 to 14.9 +/- 1.3 mmHg. Another cohort of mice was then exposed to IH for 5 wk (O2 nadir = 5%, 60-s cycles, 12 h/day) and then implanted with catheters. In response to 5 wk of chronic IH, mice (n = 8) increased systemic blood pressure by 7.5 mmHg, left ventricle + septum weight by 32.2 +/- 7.5 x 10(-2) g/100 g body wt (P < 0.015), and right ventricle weight by 19.3 +/- 3.2 x 10(-2) g/100 g body wt (P < 0.001), resulting in a 14% increase in the right ventricle/left ventricle + septum weight (P < 0.005). We conclude that in C57BL/6J mice 1) acute hypoxia causes opposite effects on the pulmonary and systemic circulations, leading to preferential loading of the right heart; and 2) chronic IH in mice results in mild to moderate systemic and pulmonary hypertension, with resultant left- and right-sided ventricular hypertrophy.

Obesidade visceral, hipertensão arterial e risco cárdio-renal: uma revisão

A maior parte da adversidade atribuída à obesidade é dada pelo risco cardiovascular/coronariano imputado à mesma, particularmente presente nos obesos com distribuição visceral de gordura corporal. O acúmulo de gordura visceral está sabidamente associado à maior prevalência de desarranjos metabólicos, hormonais, inflamatórios e hemodinâmicos, que no conjunto implicarão em maior acometimento da microvasculatura e impacto negativo sobre os órgãos-alvo, particularmente sobre o eixo cárdio-renal. Neste sentido, além da associação clássica com a doença coronariana, têm-se verificado uma associação maior da obesidade visceral com a hipertrofia ventricular esquerda e microalbuminúria, ambos fatores de risco cardiovascular e nefrológico reconhecidos. Assim, a abordagem terapêutica dos pacientes obesos, particularmente dos hipertensos, deve levar em conta a estratificação de risco baseada na distribuição de gordura corporal, o que permitirá uma terapêutica mais adequada, visando-se não só o controle dos fatores de risco como a monitorização do acometimento de órgãos-alvo nestas populações.

[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.

The effect of simulated obstructive apnoea on intraocular pressure and pulsatile ocular blood flow in healthy young adults

AIM

To investigate the effect of negative inspiratory effort, as generated by the Mueller manoeuvre, on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in healthy young adults.

METHODS

Seven volunteers with no history of systemic or ocular disease were recruited (mean age 30.7 years, range 25-40 years, M/F: 4/3). After initial instruction and practice of the Mueller manoeuvre, baseline measurements of IOP and POBF were obtained for both eyes after 10 and 15 minutes of rest, respectively, in the supine position. Thereafter, the Mueller manoeuvre was performed creating a mouthpiece pressure of -20 cm H(2)O, for at least 15 seconds followed by a 5 minute rest. The manoeuvre was repeated with a mouthpiece pressure of -40 cm H(2)O. IOP and POBF were measured 5-15 seconds into the manoeuvre for both -20 cm H(2)O (M2A) and -40 cm H(2)O (M4A) and directly upon recovery (after two respiratory cycles) from each manoeuvre (M2B, M4B). Baseline measurements were compared using paired t test, whereas manoeuvre induced changes in IOP and POBF were analysed individually using repeated measures ANOVA with Student-Newman Keuls post hoc analyses. Linear regression analysis was used to investigate a dose-response effect.

RESULTS

No significant differences were found between baseline measurements so they were subsequently pooled. There was a significant decrease in IOP for M2B (-9.2%, p<0.05), M4A (-13.8%, p<0.05), and M4B (-15.6%, p<0.05), relative to baseline. A dose-response relation was found for the effect of mouthpiece pressure on measurements 5-10 seconds into the manoeuvre (M2A and M4A, r = 0.54, p = 0.045). There was a trend of increased POBF relative to baseline for all measurements; however, significance was reached for M4B only (p = 0.039).

CONCLUSION

It was shown that forced inspiratory efforts as generated by the Mueller manoeuvre are associated with a dose dependent decrease in IOP and a concomitant increase in pulsatile ocular blood flow.

The Relationship Between Congestive Heart Failure, Sleep Apnea, and Mortality in Older Men

STUDY OBJECTIVES

To examine the association of sleep apnea with heart disease.

DESIGN

Prospective study.

SETTING

Medical wards at the Veterans Affairs San Diego Healthcare System.

PATIENTS

Three hundred fifty-three randomly selected inpatient men.

MEASUREMENTS AND RESULTS

Sleep was recorded for 2 nights in the hospital. Medical conditions were obtained from hospital medical records. Cox proportional hazards analyses indicated that patients with congestive heart failure (CHF) plus central sleep apnea (CSA) had shorter survival than those with just CHF, just sleep apnea (obstructive or central), or neither. Survival for those with obstructive sleep apnea (OSA) or CSA and no CHF was no different than for those with neither disorder. Follow-up analysis showed that for those with no CHF, neither CSA nor OSA shortened survival (p > 0.80). For those with CHF, having CSA shortened the life span with a hazard ratio of 1.66 (p = 0.012), but having OSA had no effect. Patients with CHF had more severe sleep apnea than those with no heart disease.

CONCLUSIONS

This study does not clarify the issues of cause and effect, but does reinforce the strong associations between sleep apnea and heart disease in elderly men. These data suggest that people with coronary disease should be regarded as a risk group for sleep apnea.

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.

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.

Cardiovascular consequences of obstructive sleep apnea

Sleep apnea is associated with several cardiovascular disease conditions. A causal relationship between sleep apnea and each of these diseases is likely, but remains to be proven. The clearest evidence implicating OSA in the development of new cardiovascular disease involves data that show an increased prevalence of new hypertension in patients with OSA followed over 4 years [3]. Circumstantial evidence and data from small study samples suggest that OSA, in the setting of existing cardiovascular disease, may exacerbate symptoms and accelerate disease progression. The diagnosis of OSA always should be considered in patients with refractory heart failure, resistant hypertension, nocturnal cardiac ischemia, and nocturnal arrhythmias, especially in individuals with risk factors for sleep apnea (e.g., central obesity, age, and male gender). Treating sleep apnea may help to achieve better clinical control in these diseases and may improve long-term cardiovascular prognosis.

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.

Effect of continuous positive airway pressure and placebo treatment on sympathetic nervous activity in patients with obstructive sleep apnea

STUDY OBJECTIVES

We studied the effect of continuous positive airway pressure (CPAP) treatment on sympathetic nervous activity in 38 patients with obstructive sleep apnea.

DESIGN

Randomized, placebo-controlled trial.

SETTING

Patients underwent polysomnography on three occasions in a clinical research center, and had BP monitored over 24 h at home. All of the patients had sleep apnea with a respiratory disturbance index (RDI) > 15.

INTERVENTIONS

The patients were randomized blindly to CPAP or placebo (CPAP at ineffective pressure) treatment.

MEASUREMENTS AND RESULTS

Prior to therapy, the number of apneas and the severity of nocturnal hypoxia correlated significantly with daytime urinary norepinephrine (NE) levels, but not nighttime urinary NE levels. CPAP treatment lowered daytime BP from 99 +/- 2 mm Hg to 95 +/- 3 mm Hg (mean +/- SEM) and nighttime BP from 93 +/- 3 mm Hg to 88 +/- 3 mm Hg. Placebo CPAP treatment decreased both day and night mean BP only 2 mm Hg. CPAP, but not placebo, treatment lowered daytime plasma NE levels by 23%, daytime urine NE levels by 36%, daytime heart rate by 2.6 beats/min, and increased lymphocyte beta(2)-adrenergic receptor sensitivity (all p < 0.05). The effect of CPAP treatment on nighttime urine NE levels and heart rate did not differ from placebo treatment. There was a suggestion of an effect of placebo CPAP treatment on nighttime measures, but not on daytime measures.

CONCLUSION

We conclude that daytime sympathetic nervous activation is greater with more severe sleep apnea. CPAP treatment diminished the daytime sympathetic activation; the potential nighttime effect of CPAP treatment was obscured by a small placebo effect.

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.

Influence of movement arousal on circadian rhythm of blood pressure in obstructive sleep apnea syndrome

OBJECTIVE

To investigate the hypothesis that repeated arousals at the termination of apnea/hypopnea in obstructive sleep apnea syndrome (OSAS) are related to abnormal circadian rhythm of blood pressure (BP).

DESIGN AND METHODS

We performed polysomnography (PSG) with pulse oximetry in 26 middle-aged patients with OSAS aged 42-58 years (mean age 51.8 years). The intensity of arousal on PSG was graded into two levels: grade 1 (EEG arousal, EA), an abrupt shift in EEG frequency, and grade 2 (movement arousal, MA), EEG arousal with an increase in electromyogram activity lasting at least 3 s. The number of apnea/hypopneas per hour (apnea/hypopnea index, AHI), and length of time during which nocturnal oxygen saturation decreased below 90% (oxygen desaturation time, ODT) were also evaluated. Percentage EA and %MA were assessed by the ratio of the number of apneas and hypopneas with EA or MA to the number of apneas and hypopneas in total. The 24 h systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured noninvasively. Multiple regression analysis was performed among AHI, ODT, %EA and %MA or among age, body mass index and %MA.

RESULTS

The %MA was the most significant factor contributing to the elevated 24 h SBP (r= 0.46, P< 0.05); oxygen desaturation (r= 0.44, P< 0.05) was the next most important contributing factor. The level and pattern of 24 h BP differed significantly between the patients with %MA 85% and %MA < 85% (mean 24 h SBP: 147 +/- 16.8 versus 125 +/- 19.6 mmHg, P< 0.01; mean 24 h DBP: 97.5 +/- 14.3 versus 85.6 +/- 14.6 mmHg, P< 0.01), and also differed between those with severe OSAS, i.e. ODT > or = 130 min, and mild to moderate OSAS, i.e. ODT < 130 min, (mean 24 h SBP: 149 +/- 15.8 versus 132 +/- 20.6 mmHg, P < 0.01; mean 24 h DBP: 100 +/- 14.1 versus 87.4 +/- 14.0 mmHg, P < 0.01).

CONCLUSION

Our findings suggest that MA and oxygen desaturation in OSAS make an important contribution to abnormal circadian rhythm of BP. We conclude that repeated end-apneic arousal and/or hypoxic asphyxia and the subsequent sleep fragmentation may contibute to nocturnal and diurnal elevation of BP.

Sleep-related breathing disorders and cardiovascular disease

Sleep-related breathing disorders, ranging from habitual snoring to the increased upper airway resistance syndrome to sleep apnea, are now recognized as major health problems. The majority of patients have excessive daytime sleepiness and tiredness. Neuropsychological dysfunction results in poor work performance, memory impairment, and even depression. Until recently, the coexistence of cardiovascular and cerebrovascular diseases with sleep-related breathing disorders was thought to be the result of shared risk factors, such as age, sex, and obesity. However, in the past 5 years several epidemiologic studies have demonstrated that sleep-related breathing disorders are an independent risk factor for hypertension, probably resulting from a combination of intermittent hypoxia and hypercapnia, arousals, increased sympathetic tone, and altered baroreflex control during sleep. Sleep apnea may lead to the development of cardiomyopathy and pulmonary hypertension. Early recognition and treatment of sleep-related breathing disorders may improve cardiovascular function.

Haemodynamic responses to obstructive sleep apnoeas in premenopausal women

OBJECTIVES

Obstructive apnoeas during sleep are associated with marked cyclical blood pressure fluctuations in men with obstructive sleep apnoea (OSA). Haemodynamic responses to OSA in women are largely unknown. We aimed to investigate haemodynamics during apnoeic events in women with OSA and to assess the influence of the menstrual cycle on these responses.

DESIGN AND METHODS

Full overnight polysomnography and continuous non-invasive blood pressure monitoring was performed in 13 women with OSA during follicular and luteal phases of the menstrual cycle. Change in blood pressure (deltaBP) from pre- to post-apnoea termination was measured for each apnoeic cycle.

RESULTS

Only 10 of 13 subjects ovulated. In women who ovulated, pressor responses to apnoea termination occurred in both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, but substantially increased during the luteal phase of ovulatory cycles [NREM change in mean arterial pressure (deltaMAP) 12 +/- 3 mmHg during the follicular phase and 20 +/- 3 mmHg during the luteal phase, P < 0.001; REM deltaMAP 11 +/- 3 mmHg during the follicular phase and 23 +/- 3 mmHg during the luteal phase, P < 0.001]. Sleep apnoea severity did not change during the cycle in NREM sleep, but was reduced in REM during the luteal phase. Changes in pressor responses were absent in non-ovulating subjects.

CONCLUSIONS

Obstructive apnoeas in women were associated with marked blood pressure changes, similar to those previously reported in men. While respiratory events improved slightly in the luteal phase, blood pressure responses to these events increased by approximately 100%. Thus, the menstrual cycle has discordant effects on the respiratory and cardiovascular effects of OSA in women.

Prognosis of the middle-aged and aged patients with obstructive sleep apnea syndrome

The long-term natural course of obstructive sleep apnea syndrome (OSAS) is studied in order to determine whether severity of nocturnal oxygen desaturation associated with apnea/hypopnea, body mass index (BMI), and hypertension influence survival in young (<40 years), middle-aged (40-64 years), and aged (> or = 65 years) using a questionnaire survey. One hundred and forty-eight patients with OSAS aged 17-78 years (136 men, 12 women, mean 52.0+/-12.3 years), who were diagnosed by standard polysomnography (PSG) between 1983 and 1993, participated in the study. The survey revealed 15 deaths and 101 survivors; 32 subjects could not be located. The survival rate was 71.4% (95% confidence interval: 55.6-87.2%). The survival rate in patients with OSAS was significantly lower than that in the age and sex-adjusted control Japanese population (87.6%). In the young group, only one death (a 19-year-old woman) occurred unexpectedly during sleep. The patient showed an apnea/hypopnea index (AHI) of 33 per h and the length of time that the nocturnal oxygen saturation (SaO2) fell below 90% (time of SaO2 <90%) of 205 min. The survival rate in middle-aged patients with OSAS was significantly lower than that in the age and sex-adjusted control Japanese population (79.2 vs 91.0%), but this pattern was not seen among the aged. Time of SaO2 <90% was significantly longer in the middle-aged patients than in the aged patients, but AHI did not differ between the two groups. Moreover, it was significantly correlated with AHI in middle-aged patients, but not in the aged patients. The survival rate was significantly lower in patients with hypertension than in the patients without such complications in the middle-aged group (57.9 vs 90.4%). Cox proportional-hazard regression model including age, hypertension, BMI, AHI, lowest SaO2, and time of SaO2 <90% showed that hypertension was only significantly associated with lower survival rate in total group and middle-aged patients, but not in the young or aged patients. The prognosis in patients with OSAS may differ among the generations. The prognosis in the middle-aged population may depend on the role of OSAS on the complications of hypertension or severity of oxygen desaturation, but not on AHI only.