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

Obstructive sleep apnea and heart failure

Obstructive sleep apnea (OSA) exerts several effects that may be particularly deleterious in patients with heart failure (HF). OSA should be considered especially in HF patients who are obese or have the metabolic syndrome, systemic hypertension, or pulmonary hypertension. HF patients in whom OSA is suspected should undergo a full evaluation by a sleep specialist, including a polysomnogram, to diagnose OSA and differentiate this disease from central sleep apnea. Those found to have OSA should then receive continuous positive airway pressure and/or other interventions, and standard disease management strategies should be used to maximize compliance. Those who cannot tolerate continuous positive airway pressure may be candidates for mandibular advancement devices or surgical therapies including tracheostomy. Standard HF medications should be used to treat HF, and optimization of fluid balance may help minimize OSA severity. However, it is still unknown whether treatment of OSA in HF patients will reduce hospitalizations or mortality.

Noninvasive measurement of central vascular pressures with arterial tonometry: clinical revival of the pulse pressure waveform?

The arterial pulse has historically been an essential source of information in the clinical assessment of health. With current sphygmomanometric and oscillometric devices, only the peak and trough of the peripheral arterial pulse waveform are clinically used. Several limitations exist with peripheral blood pressure. First, central aortic pressure is a better predictor of cardiovascular outcome than peripheral pressure. Second, peripherally obtained blood pressure does not accurately reflect central pressure because of pressure amplification. Lastly, antihypertensive medications have differing effects on central pressures despite similar reductions in brachial blood pressure. Applanation tonometry can overcome the limitations of peripheral pressure by determining the shape of the aortic waveform from the radial artery. Waveform analysis not only indicates central systolic and diastolic pressure but also determines the influence of pulse wave reflection on the central pressure waveform. It can serve as a useful adjunct to brachial blood pressure measurements in initiating and monitoring hypertensive treatment, in observing the hemodynamic effects of atherosclerotic risk factors, and in predicting cardiovascular outcomes and events. Radial artery applanation tonometry is a noninvasive, reproducible, and affordable technology that can be used in conjunction with peripherally obtained blood pressure to guide patient management. Keywords for the PubMed search were applanation tonometry, radial artery, central pressure, cardiovascular risk, blood pressure, and arterial pulse. Articles published from January 1, 1995, to July 1, 2009, were included in the review if they measured central pressure using radial artery applanation tonometry.

Characteristics and predictors of obstructive sleep apnea in patients with systemic hypertension

Obstructive sleep apnea (OSA) is a secondary cause of hypertension and independently associated with target-organ damage in hypertensive patients. However, OSA remains largely underdiagnosed and undertreated. The aim of the present study was to evaluate the characteristics and clinical predictors of OSA in a consecutive series of patients followed up in a hypertension unit. A total of 99 patients (age 46 + or - 11 years, body mass index 28.8 kg/m(2), range 25.1 to 32.9) underwent polysomnography. The clinical parameters included age, gender, obesity, daytime sleepiness, snoring, Berlin Questionnaire, resistant hypertension, and metabolic syndrome. Of the 99 patients, 55 (56%) had OSA (apnea-hypopnea index >5 events/hour). Patients with OSA were older and more obese, had greater levels of blood pressure, and presented with more diabetes, dyslipidemia, resistant hypertension, and metabolic syndrome than the patients without OSA. Of the patients with OSA, 51% had no excessive daytime sleepiness. The Berlin Questionnaire and patient age revealed a high sensitivity (0.93 and 0.91, respectively) but low specificity (0.59 and 0.48, respectively), and obesity and resistant hypertension revealed a low sensitivity (0.58 and 0.44, respectively) but high specificity (0.75 and 0.91, respectively) for OSA. Metabolic syndrome was associated with high sensitivity and specificity for OSA (0.86 and 0.85, respectively). Multiple regression analysis showed that age of 40 to 70 years (odds ratio 1.09, 95% confidence interval 1.03 to 1.16), a high risk of OSA on the Berlin Questionnaire (odds ratio 8.36, 95% confidence interval 1.67 to 41.85), and metabolic syndrome (odds ratio 19.04, 95% confidence interval 5.25 to 69.03) were independent variables associated with OSA. In conclusion, more important than the typical clinical features that characterize OSA, including snoring and excessive daytime sleepiness, the presence of the metabolic syndrome is as an important marker of OSA among patients with hypertension.

Obstructive sleep apnea, masked hypertension, and arterial stiffness in men

BACKGROUND

Obstructive sleep apnea (OSA) is an established cause of hypertension. However, it is not clear whether the frequency of masked hypertension in patients with OSA and whether OSA have an independent role on arterial stiffness taking into account ambulatory blood pressure (BP) monitoring (ABPM).

METHODS

We evaluated 61 male normotensive participants as determined by casual clinic BP level <140/90 mm Hg without clinical evidence of cardiovascular disease and on no medications (43 patients with moderate-to-severe OSA (apnea-hypopnea index (AHI) > or = 15 events/hour by polysomnography) and 18 age- and body mass index-matched controls without OSA (AHI <5 events/hour)). Pulse wave velocity (PWV), an index of arterial stiffness, and 24-h ABPM were performed in a blinded fashion. Masked hypertension was defined when abnormal daytime ABPM was > or = 135 or > or = 85 mm Hg.

RESULTS

The AHI and lowest oxygen saturation were 2.6 +/- 1.6 and 90 +/- 2 vs. 52.8 +/- 21.0 events/hour and 75 +/- 10% for controls and OSA patients, respectively; P < 0.001. Compared with controls, patients with OSA had higher office systolic BP (113 +/- 9 vs. 118 +/- 10 mm Hg; P = 0.05) and a higher unadjusted proportion of masked hypertension (2 controls (11.1%) vs. 13 patients (30.2%); P < 0.05). PWV was 8.7 +/- 0.7, 9.4 +/- 1.0, and 10.6 +/- 1.1 m/s in the control, OSA without and with masked hypertension groups, respectively (P < 0.01 for each comparison). Multiple regression showed that systolic daytime ABPM and the lowest oxygen saturation were independently related to PWV (adjusted R2 = 0.34; P < 0.01).

CONCLUSIONS

Patients with OSA presented a higher unadjusted rate of masked hypertension than matched controls. Lowest oxygen saturation has an independent association with arterial stiffness.

Changes in left and right ventricular mechanics during the Mueller maneuver in healthy adults: a possible mechanism for abnormal cardiac function in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea is highly prevalent in patients with cardiovascular disease and has detrimental effects on systolic and diastolic function of the ventricles. In this research, the changes in strain (S) and strain rate (SR) during the performance of the Mueller maneuver (MM) in an effort to better understand how negative intrathoracic pressures affect ventricular mechanics.

METHODS AND RESULTS

The MM was performed to maintain a target intrathoracic pressure of -40 mm Hg. Echocardiography was used to measure various parameters of cardiac structure and function. Myocardial deformation measurements were performed using tissue speckle tracking. Twenty-four healthy subjects (9 women; mean age, 30+/-6 years) were studied. Global left ventricular longitudinal S in systole and SR in early filling were significantly decreased during the MM (S: baseline, -17.0+/-1.6%; MM, -14.5+/-2.2%; P<0.0001, SR: baseline, 1.09+/-0.20 s(-1); MM, 0.92+/-0.21 s(-1); P=0.01). Global right ventricular longitudinal S was also significantly decreased during the MM (baseline, -22.0+/-3.1%; MM, -17.2+/-2.5%; P<0.0001), as was global right ventricular longitudinal systolic SR (baseline, -1.34+/-0.35 s(-1); MM, -1.02+/-0.21 s(-1); P=0.0006).

CONCLUSIONS

Left ventricular and right ventricular longitudinal deformation are significantly reduced during the MM. These results suggest that negative intrathoracic pressure during apnea may contribute to changes in myocardial mechanics. These results could help explain the observed changes in left ventricular and right ventricular mechanics in patients with obstructive sleep apnea.

Obstructive sleep apnea is common and independently associated with atrial fibrillation in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is associated with arrhythmias and cardiovascular death. Left atrial enlargement and atrial fibrillation (AF) are considered markers for death due to heart failure in patients with HCM. Obstructive sleep apnea (OSA) is independently associated with heart remodeling and arrhythmias in other populations. We hypothesized that OSA is common and is associated with heart remodeling and AF in patients with HCM.

METHODS

We evaluated 80 consecutive stable patients with a confirmed diagnosis of HCM by sleep questionnaire, blood tests, echocardiography, and sleep study (overnight respiratory monitoring).

RESULTS

OSA (apnea-hypopnea index [AHI] > 15 events/h) was present in 32 patients (40%). Patients with OSA were significantly older (56 [41-64] vs 38.5 [30-53] years, P < .001) and presented higher BMI (28.2 +/- 3.5 vs 25.2 +/- 5.2 kg/m(2), P < .01) and increased left atrial diameter (45 [42-52.8] vs 41 [39-47] mm, P = .01) and aorta diameter (34 [30-37] vs 29 [28-32] mm, P < .001), compared with patients without OSA. Stepwise multiple linear regression showed that the AHI (P = .05) and BMI (P = .06) were associated with left atrial diameter. The AHI was the only variable associated with aorta diameter (P = .01). AF was present in 31% vs 6% of patients with and without OSA, respectively (P < .01). OSA (P = .03) and left atrial diameter (P = .03) were the only factors independently associated with AF.

CONCLUSIONS

OSA is highly prevalent in patients with HCM and it is associated with left atrial and aortic enlargement. OSA is independently associated with AF, a risk factor for cardiovascular death in this population.

Sleep disordered breathing, insomnia, and health related quality of life -- a comparison between age and gender matched elderly with heart failure or without cardiovascular disease

AIMS

The aims of this study are (I) to compare the prevalence of sleep disordered breathing (SDB) and insomnia between elderly with heart failure (HF) and age and gender matched elderly without cardiovascular disease (CVD), and (II) to examine the association between HF, SDB and insomnia, as well as their impact on health related quality of life (Hr-QoL).

METHODS

Three hundred and thirty-one elderly (71-87 years) community-living individuals underwent sleep recordings and echocardiography. Questionnaires assessed insomnia and Hr-QoL. Comparisons were made between age and gender matched individuals with HF (n=36) and without CVD (n=36).

RESULTS

The HF group had higher mean apnoea-hypopnoea index (17.6 vs. 6.3, p<0.001). Moderate/severe SDB was found in 42% of those with HF vs. 8% in those without CVD (p=0.001). Those with HF had more difficulties maintaining sleep (DMS) (72% vs. 50%, p=0.05) and excessive daytime sleepiness (EDS) (25% vs. 8%, p=0.05) and scored worse Hr-QoL in five of eight SF-36 domains. In regression analysis SDB had no association to Hr-QoL. DMS associated to the physical-, and non restorative sleep to the mental domain of Hr-QoL. SDB had no correlations to insomnia or EDS.

CONCLUSIONS

SDB, DMS and EDS are more common in elderly with HF. SDB is not an obvious cause for sleep complaints or poor Hr-QoL in elderly.

Effects of massage therapy on sleep quality after coronary artery bypass graft surgery

INTRODUCTION

Having poor sleep quality is common among patients following cardiopulmonary artery bypass graft surgery. Pain, stress, anxiety and poor sleep quality may be improved by massage therapy.

OBJECTIVE

This study evaluated whether massage therapy is an effective technique for improving sleep quality in patients following cardiopulmonary artery bypass graft surgery.

METHOD

Participants included cardiopulmonary artery bypass graft surgery patients who were randomized into a control group and a massage therapy group following discharge from the intensive care unit (Day 0), during the postoperative period. The control group and the massage therapy group comprised participants who were subjected to three nights without massage and three nights with massage therapy, respectively. The patients were evaluated on the following mornings (i.e., Day 1 to Day 3) using a visual analogue scale for pain in the chest, back and shoulders, in addition to fatigue and sleep. Participants kept a sleep diary during the study period.

RESULTS

Fifty-seven cardiopulmonary artery bypass graft surgery patients were enrolled in the study during the preoperative period, 17 of whom were excluded due to postoperative complications. The remaining 40 participants (male: 67.5%, age: 61.9 years ± 8.9 years, body mass index: 27.2 kg/m² ± 3.7 kg/m²) were randomized into control (n = 20) and massage therapy (n = 20) groups. Pain in the chest, shoulders, and back decreased significantly in both groups from Day 1 to Day 3. The participants in the massage therapy group had fewer complaints of fatigue on Day 1 (p=0.006) and Day 2 (p=0.028) in addition, they reported a more effective sleep during all three days (p=0.019) when compared with the participants in the control group.

CONCLUSION

Massage therapy is an effective technique for improving patient recovery from cardiopulmonary artery bypass graft surgery because it reduces fatigue and improves sleep.

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.

Time course of intermittent hypoxia-induced impairments in resistance artery structure and function

We previously demonstrated that chronic exposure to intermittent hypoxia (CIH) impairs endothelium-dependent vasodilation in rats. To determine the time course of this response, rats were exposed to CIH for 3, 14, 28, or 56 days. Then, we measured acetylcholine- and nitroprusside-induced vasodilation in isolated gracilis arteries. Also, we measured endothelial and inducible nitric oxide synthase, nitrotyrosine, and collagen in the arterial wall and urinary isoprostanes. Endothelium-dependent vasodilation was impaired after 2 weeks of CIH. Three days of CIH was not sufficient to produce this impairment and longer exposures (i.e. 4 and 8 weeks) did not exacerbate it. Impaired vasodilation was accompanied by increased collagen deposition. CIH elevated urinary isoprostane excretion, whereas there was no consistent effect on either isoform of nitric oxide synthase or nitrotyrosine. Exposure to CIH produces functional and structural deficits in skeletal muscle resistance arteries. These impairments develop within 2 weeks after initiation of exposure and they are accompanied by systemic evidence of oxidant stress.

Right ventricular subclinical diastolic dysfunction in obese children: the effect of weight reduction with a low-carbohydrate diet

This study aimed primarily to identify whether childhood obesity leads to right ventricular (RV) subclinical diastolic dysfunction or not. It also aimed to examine the effect of weight reduction on right ventricular function. Standard and tissue Doppler echocardiography was performed for 28 overweight (body mass index [BMI], 25-30 kg/m(2)) and 34 obese (BMI, > or = 30 kg/m(2)) children and for 29 age- and sex-matched lean referents (BMI, 17-25 kg/m(2)). Levels of plasma lipids, fasting glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) were obtained for all the participants. For 6 months, 30 obese children were given a low-carbohydrate diet and then reevaluated by echocardiography. Conventional echocardiographic parameters all were similar for obese, overweight, and lean control children. The tricuspid free-wall isovolumetric relaxation time (IVRT), tricuspid lateral annular early diastolic velocity (e'), ratio of early-to-late diastolic velocity (e'/a'), and tricuspid lateral annular IVRT differed significantly between the overweight and control children. The RV tissue Doppler parameters were found to be similar between the preobese and control children. The IVRT of the RV free wall and lateral tricuspid annulus was significantly decreased, and the e'/a' of the lateral tricuspid annulus was significantly increased after the diet. In conclusion, obesity is associated with subclinical RV diastolic dysfunction in pediatric patients. Weight reduction with a low-carbohydrate diet may reverse the effects of obesity on RV diastolic function.

Obstructive sleep apnea is highly prevalent and correlates with impaired glycemic control in consecutive patients with the metabolic syndrome

Obstructive sleep apnea (OSA) and the metabolic syndrome (MS) are independently associated with increased cardiovascular risk. The objective of the present study was to determine the prevalence of OSA among consecutive patients with MS and to determine whether OSA is associated with impaired glycemic control. Fifty consecutive patients with a recent diagnosis of MS and no previous diagnosis of OSA underwent a polysomnography and anthropometric and laboratory measurements. The prevalence of OSA (apnea-hypopnea index >or=15 events per hour of sleep) was 68% and in the same range of all other individual components of MS. Moreover, OSA was associated with increased levels of glucose (P=.03) and glycosylated hemoglobin (P=.03) but not with body mass index (P=.30). Glycosylated hemoglobin was independently associated with glucose (P<.001) and apnea-hypopnea index (P=.03). The prevalence of OSA is in the same range as all the individual components of MS and is independently associated with impaired glycemic control.

The incremental role of obstructive sleep apnoea on markers of atherosclerosis in patients with metabolic syndrome

OBJECTIVE

Metabolic syndrome (MS) is associated with subclinical atherosclerosis, but the relative role of obstructive sleep apnoea (OSA) is largely unknown. The main objective of this study is to determine the impact of OSA on markers of atherosclerosis in patients with MS.

METHODS

Eighty-one consecutive patients with MS according to the Adult Treatment Panel III underwent a clinical evaluation, polysomnography, laboratory and vascular measurements of carotid intima media thickness (IMT), carotid-femoral pulse wave velocity (PWV) and carotid diameter (CD) in a blind fashion. OSA was defined as an apnoea-hypopnoea index (AHI) > or =15 events/hour. Multiple linear regression was performed to determine the variables that were independently associated with the vascular parameters.

RESULTS

Fifty-one patients (63%) had OSA. No significant differences existed in age, sex, MS criteria, and cholesterol levels between patients with (MS+OSA) and without OSA (MS-OSA). Compared with MS-OSA patients, MS+OSA patients had higher levels of IMT (661+/-117 vs. 767+/-140 microm), PWV (9.6+/-1.0 vs. 10.6+/-1.6m/s), and CD (6705+/-744 vs. 7811+/-862 microm) (P<0.001 for each comparison). Among patients with MS+OSA, all vascular parameters were similar in patients with and without daytime sleepiness. The independent parameters associated with IMT, PWV, and CD were AHI, abdominal circumference, and systolic blood pressure (R(2)=0.42); AHI and systolic blood pressure (R(2)=0.38); and AHI, age, abdominal circumference and systolic blood pressure (R(2)=0.45), respectively. The R(2) of AHI for IMT, PWV and CD was 0.12, 0.10 and 0.20, respectively.

CONCLUSIONS

OSA is very common and has an incremental role in atherosclerotic burden in consecutive patients with MS.

Continuous positive airway pressure treatment for obstructive sleep apnoea reduces resting heart rate but does not affect dysrhythmias: a randomised controlled trial

Obstructive sleep apnoea (OSA) is associated with cardiovascular morbidity and may precipitate cardiac dysrhythmias. Uncontrolled reports suggest that continuous positive airway pressure (CPAP) may reduce dysrhythmia frequency and resting heart rate. We undertook a randomised controlled trial of therapeutic CPAP and compared with a subtherapeutic control which included an exploration of changes in dysrhythmia frequency and heart rate. Values are expressed as mean (SD). Eighty-three men [49.5 (9.6) years] with moderate-severe OSA [Oxygen Desaturation Index, 41.2 (24.3) dips per hour] underwent 3-channel 24-h electrocardiograms during normal daily activities, before and after 1 month of therapeutic (n = 43) or subtherapeutic (n = 40) CPAP. Recordings were manually analysed for mean heart rate, pauses, bradycardias, supraventricular and ventricular dysrhythmias. The two groups were well matched for age, body mass index, OSA severity, cardiovascular risk factors and history. Supraventricular ectopics and ventricular ectopics were frequently found in 95.2% and 85.5% of patients, respectively. Less common were sinus pauses (42.2%), episodes of bradycardia (12%) and ventricular tachycardias (4.8%). Compared with subtherapeutic control, CPAP reduced mean 24-h heart rate from 83.0 (11.5) to 79.7 (9.8) (P < 0.002) in the CPAP group compared with a non-significant rise (P = 0.18) from 79.0 (10.4) to 79.9 (10.4) in the subtherapeutic group; this was also the case for the day period analysed separately. There was no significant change in the frequencies of dysrhythmias after CPAP. Four weeks of CPAP therapy reduces mean 24-h heart rate possibly due to reduced sympathetic activation but did not result in a significant decrease in dysrhythmia frequency.

Left atrial diameter is independently associated with arterial stiffness in patients with obstructive sleep apnea: potential implications for atrial fibrillation

BACKGROUND

Obstructive sleep apnea (OSA) is associated with increased risk for the occurrence and recurrence of atrial fibrillation. However, the mechanisms involved are poorly understood.

METHODS

We studied 73 middle-aged subjects divided in two groups: with moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥ 15 events/h) or without OSA (AHI ≤5 events/h) by polysomnography. The groups were matched for age, sex, body mass index and hypertension diagnosis. Carotid-femoral pulse wave velocity (a non invasive measurement of arterial stiffness of the aorta) and transthoracic echocardiography were performed in all participants.

RESULTS

As expected, patients with OSA presented higher AHI than patients without OSA (49.6 ± 21.5 vs. 3.3 ± 1.4 events/h; P<0.001). Compared with subjects without OSA, pulse wave velocity (9.6 ± 1.5 vs. 10.7 ± 1.8 m/s; P<0.001) and left atrial diameter (34.7 ± 3.2 vs. 37.6 ± 3.3 mm; P<0.001) were significantly increased in patients with OSA. Pulse wave velocity significantly correlated with left atrial diameter (r=0.45; P<0.001). Multivariate regression analysis showed that AHI and systolic blood pressure were the only independent determinants of pulse wave velocity (F=30.5; r(2)=0.48; P<0.01). The only independent variable associated with left atrial diameter was pulse wave velocity.

CONCLUSIONS

Left atrial diameter is significantly increased and independently associated with arterial stiffness in patients with OSA. This potential mechanism of atrial remodeling may contribute to explain the increase risk of atrial fibrillation in these patients.

Sleep in heart failure

Sleep plays a large role in patients with heart failure. In normal subjects, sleep is usually in a supine position with reduced sympathetic drive, elevated vagal tone and as such a relatively lower cardiac output and minute ventilation, allowing for recuperation. Patients with heart failure may not experience the same degree of autonomic activity change and the supine position may place a large strain on the pulmonary system. More than half of all heart failure patients have one of two types of sleep apnea: either obstructive or central sleep apnea. Some patients have both types. Obstructive sleep apnea is likely to be a cause of heart failure due to large negative intrathoracic pressures, apnea related hypoxemia and hypercapnia, terminated by an arousal and surge in systemic blood pressure associated with endothelial damage and resultant premature atherosclerosis. Reversal of obstructive sleep apnea improves blood pressure, systolic contraction and autonomic dysfunction however mortality studies are lacking. Central sleep apnea with Cheyne Stokes pattern of respiration (CSA-CSR) occurs as a result of increased central controller (brainstem driving ventilation) and plant (ventilation driving CO2) gain in the setting of a delayed feed back (i.e., low cardiac output). It is thought this type of apnea is a result of moderately to severely impaired cardiac function and is possibly indicative of high mortality. Treatment of CSA-CSR is best undertaken by treating the underlying cardiac condition which may include with medications, pacemakers, transplantation or continuous positive airway pressure (CPAP). In such patients CPAP exerts unique effects to assist cardiac function and reduce pulmonary edema. Whether CPAP improves survival in this heart failure population remains to be determined.

Obstructive sleep apnea and hypertension: mechanisms, evaluation, and management

Obstructive sleep apnea (OSA) is a recognized cause of secondary hypertension. OSA episodes produce surges in systolic and diastolic pressure that keep mean blood pressure levels elevated at night. In many patients, blood pressure remains elevated during the daytime, when breathing is normal. Contributors to this diurnal pattern of hypertension include sympathetic nervous system overactivity and alterations in vascular function and structure caused by oxidant stress and inflammation. Treatment of OSA with nasal continuous positive airway pressure (CPAP) abolishes apneas, thereby preventing intermittent arterial pressure surges and restoring the nocturnal "dipping" pattern. CPAP treatment also has modest beneficial effects on daytime blood pressure. Because even small decreases in arterial pressure can contribute to reducing cardiovascular risk, screening for OSA is an essential element of evaluating patients with hypertension.

Additive effects of obstructive sleep apnea and hypertension on early markers of carotid atherosclerosis

Obstructive sleep apnea (OSA) has emerged as an independent risk factor for atherosclerosis. However, OSA is frequently associated with several risk factors for atherosclerosis, including hypertension (HTN). The impact of OSA and HTN alone compared with the association of both conditions on carotid atherosclerosis is not understood. We studied 94 middle-aged participants free of smoking and diabetes mellitus who were divided into 4 groups: controls (n=22), OSA (n=25), HTN (n=20), and OSA+HTN (n=27). All of the participants underwent polysomnography and carotid measurements of intima-media thickness, diameter, and distensibility with an echo-tracking device. Compared with controls, intima-media thickness and carotid diameter were similarly higher in OSA (713+/-117 and 7117+/-805 microm), and HTN groups (713+/-182 and 7191+/-818 microm), with a further significant increase in OSA+HTN patients (837+/-181 and 7927+/-821 microm, respectively; P<0.01). Carotid distensibility was significantly lower in HTN (P<0.05) and OSA+HTN subjects (P<0.001) compared with controls. In the OSA+HTN group, carotid distensibility was significantly lower than in the OSA group and controls (P<0.05 for each comparison). Multivariate analysis showed that intima-media thickness was positively related to systolic blood pressure and apnea-hypopnea index. Apnea-hypopnea index was the only factor related to carotid diameter. Age and systolic blood pressure were independently related to carotid distensibility. In conclusion, the association of OSA and HTN has additive effects on markers of carotid atherosclerosis. Because early markers of carotid atherosclerosis predict future cardiovascular events, including not only stroke but also myocardial infarction, these findings may help to explain the increased risk of cardiovascular disease in patients with OSA.

Severe obstructive sleep apnoea exacerbates the microvascular impairment in very mild hypertensives

BACKGROUND

Different studies have shown that obstructive sleep apnoea syndrome (OSAS), frequently associated with hypertension, represents a harmful and independent risk for cardiovascular diseases. The aim of our study was to ascertain whether the occurrence of OSAS could worsen microcirculatory impairment in very mild hypertensives.

MATERIALS AND METHODS

One hundred untreated very mild hypertensives underwent polysomnography and subdivided into 32 non-OSAS, 33 mild OSAS and 35 severe OSAS patients on standardized criteria. They underwent routine blood chemistry, ambulatory blood pressure monitoring and anthropometric analysis. Skin capillary density (n mm(-2)) of forearm (FAC) and periungueal (PUC) fields was obtained through videocapillaroscopy. By a venous congestion manoeuvre, PUC was maximized (CVC) and secondary capillary recruitment (GAIN) was calculated. These measurements served as indices of structural and functional capillary rarefaction, respectively.

RESULTS

Severe OSAS hypertensives showed reduced FAC (P < 0.001) and PUC (P < 0.001) as compared to those with mild OSAS and non-OSAS, but a greater CVC (P < 0.01) and GAIN (P < 0.001). Multiple regression analysis showed that PUC was inversely related to total sleep time with oxyhaemoglobin saturation at < 90% (TST90) (P < 0.001) and FAC to the apnoea-hypopnoea index (AHI) (P < 0.001) and to the sleep propensity (P < 0.01). CVC was positively associated to AHI (P < 0.001) and GAIN to TST90 (P < 0.05).

CONCLUSIONS

The findings suggest that OSAS, by means of reduced basal and functional capillarity rarefaction, might pose an additional risk of impaired peripheral perfusion in very mild hypertensives. A microcirculation study therefore should be a part of the clinical approach in patients at high cerebro-cardiovascular risk such as hypertensives and patients with OSAS.

Postnatal Intermittent Hypoxia and Developmental Programming of Hypertension in Spontaneously Hypertensive Rats

Obstructive and central apneas during sleep are associated with chronic intermittent hypoxia (CIH) and increased cardiovascular morbidity. Spontaneously hypertensive rats exposed to CIH during postnatal days 4 to 30 develop exaggerated hypertension as adults. We hypothesized that reactive oxygen species and altered L-Ca 2+ channel activity may underlie the postnatal programming of exaggerated blood pressure and cardiac remodeling. Newborn male spontaneously hypertensive rats were exposed to CIH (10% and 21% O 2 alternating every 90 seconds, 12 h/d, for postnatal days 4 to 30) or normoxia (room air). In each condition, spontaneously hypertensive rats received daily (SC) 1 of 3 treatments: l -calcium channel blocker nifedipine (5 mg/kg), superoxide dismutase mimetic MnTMPyP pentachloride (10 mg/kg), or vehicle (polyethylene glycol). Blood pressure was evaluated monthly for 6 months after birth, and echocardiographic assessments were conducted at 6 months of age. CIH vehicle-treated rats presented higher systolic blood pressure (187±5 mm Hg) as compared with normoxic vehicle treated controls (163±2 mm Hg; P <0.001). Postnatal CIH elicited marked increases in left ventricular wall thickness in a pattern of concentric hypertrophy with augmented systolic contractility. The treatment with nifedipine in the CIH group attenuated blood pressure (159±2 mm Hg; P <0.001) and normalized left ventricular wall thickness and systolic function, whereas the treatment with SOD mimetic decreased blood pressure (165±2 mm Hg; P <0.001) and reduced left ventricular wall thickness without changes in the systolic function. We conclude that Ca 2+ and reactive oxygen species–mediated signaling during intermittent hypoxia are critical mechanisms underlying postnatal programming of an increased severity of hypertension and hypertrophic cardiac remodeling in a genetically susceptible rodent model.

Attenuated heart rate recovery following exercise testing in overweight young men with untreated obstructive sleep apnea

STUDY OBJECTIVE

To evaluate whether cardiovascular responses to maximal exercise testing and recovery are altered with obstructive sleep apnea (OSA) in overweight young adult men.

DESIGN

Three sedentary subject groups were recruited: Overweight with OSA (OSA), overweight without OSA (No-OSA), and normal weight without OSA (Control). Presence of OSA was screened via portable diagnostic device. Body composition was measured with dual-energy X-ray absorptiometry. Subjects performed maximal ramping exercise testing (RXT) on a cycle ergometer with 5 minutes of active recovery. Exercise measurements included heart rate (HR), blood pressure (BP), respiratory exchange ratio (RER), and oxygen consumption (VO2). Recovery HR was converted to a HR difference (HR(diff)) calculation (HR(peak) - HR(each minute recovery)), and BP was converted to a recovery ratio for each minute.

SETTING

The study was carried out on the campus of Virginia Tech, Department of Human Nutrition, Foods, and Exercise, Blacksburg, Virginia.

PARTICIPANTS

14 OSA, 16 No-OSA, and 14 Control volunteers.

INTERVENTION

N/A.

MEASUREMENTS AND RESULTS

In OSA subjects, HR recovery was significantly attenuated compared to the No-OSA and Control groups throughout recovery (P = 0.009). No differences were noted in the HR or BP response to exercise in any group. The VO2, adjusted for fat-free soft tissue mass, did not differ between groups.

CONCLUSIONS

We found that OSA elicits alterations in the cardiovascular response post exercise, reflected by an attenuated HR recovery. This may indicate an imbalance in the autonomic regulation of HR. Exercise tests may provide utility in risk stratification for those at risk for OSA.

Effects of continuous positive airway pressure on early signs of atherosclerosis in obstructive sleep apnea

RATIONALE

Obstructive sleep apnea (OSA) is associated with adverse cardiovascular outcomes, including myocardial infarction and stroke. Atherosclerosis is a key mechanism for these cardiovascular events. Recent cross-sectional studies showed the presence of early signs of atherosclerosis in patients with OSA who were free of comorbidities.

OBJECTIVES

To determine the impact of treatment with continuous positive airway pressure (CPAP) on atherosclerosis.

METHODS

We randomly assigned 24 patients with severe OSA (age, 46 +/- 6 yr) who were free of comorbidities to receive no treatment (control, n = 12) or CPAP (n = 12) for 4 months. Carotid intima-media thickness, arterial stiffness (evaluated by pulse-wave velocity), carotid diameter, 24-hour blood pressure monitoring, C-reactive protein, and catecholamines were determined at baseline and after 4 months.

MEASUREMENTS AND MAIN RESULTS

At baseline, all measurements were similar in both groups and did not change in the control group after 4 months. In contrast, a significant decrease occurred in carotid intima-media thickness (707 +/- 105 vs. 645 +/- 95 microm, P = 0.04), pulse-wave velocity (10.4 +/- 1.0 vs. 9.3 +/- 0.9 m/s, P < 0.001), C-reactive protein (3.7 +/- 1.8 vs. 2.0 +/- 1.2 mg/L, P = 0.001), and catecholamines (365 +/- 125 vs. 205 +/- 51 ng/ml, P < 0.001) after 4 months of CPAP. Carotid diameter did not change significantly. Regarding the whole group, changes in carotid intima-media thickness were correlated with changes in catecholamines (r = 0.41, P < 0.05). Changes in pulse-wave velocity were correlated with changes in C-reactive protein (r = 0.58, P < 0.01) and catecholamines (r = 0.54, P < 0.01).

CONCLUSIONS

The treatment of OSA significantly improves early signs of atherosclerosis, supporting the concept that OSA is an independent risk factor for atherosclerosis. Clinical trial registered with www.clinicaltrials.gov (NCT 00400543).