Day-night variation of acute myocardial infarction in obstructive sleep apnea

Chemoreflex physiology and implications for sleep apnoea: insights from studies in humans

NEW FINDINGS

What is the topic of this review? This review summarizes chemoreflex physiology in health and disease, with specific focus on chemoreflex-mediated pathophysiology in obstructive and central sleep apnoea. What advances does it highlight? Chemoreflex mechanisms are thought to contribute significantly to the pathophysiology and adverse outcomes seen in sleep apnoea. Clinical implications of altered chemoreflex function in sleep apnoea from recent studies in humans, including cardiac arrhythmias, coronary artery disease, systolic/diastolic heart failure and sudden cardiac death are highlighted. Activation of the chemoreflex in response to hypoxaemia results in an increase in sympathetic neural outflow. This process is predominantly mediated by the peripheral chemoreceptors in the carotid bodies and is potentiated by the absence of the sympatho-inhibitory influence of ventilation during apnoea, as is seen in patients with sleep apnoea. In these patients, repetitive nocturnal hypoxaemia and apnoea elicit sympathetic activation, which may persist into wakefulness and is thought to contribute to the development of systemic hypertension and cardiac and vascular dysfunction. Chemoreflex activation could possibly lead to adverse cardiovascular outcomes, such as nocturnal myocardial infarction, systolic and/or diastolic heart failure, cardiac arrhythmias and sudden death in patients with sleep apnoea. This review summarizes chemoreflex physiology in health and disease, with specific focus on chemoreflex-mediated pathophysiology in obstructive and central sleep apnoea. Measurement of the chemoreflex response may serve as a potential avenue for individualized screening for cardiovascular disease. Whether modulation of this response in sleep apnoea may aid in the prevention and treatment of adverse cardiovascular consequences will require further study.

Morning pentraxin3 levels reflect obstructive sleep apnea-related acute inflammation

This study investigated morning levels of pentraxin3 (PTX3) as a sensitive biomarker for acute inflammation in patients with obstructive sleep apnea (OSA). A total of 61 consecutive patients with OSA were divided into two groups: non-to-mild (n = 20) and moderate-to-severe (n = 41) OSA based on their apnea-hypopnea index (AHI) score. Those patients with moderate-to-severe OSA were further divided into continuous positive airway pressure (CPAP) treated (n = 21) and non-CPAP-treated (n = 20) groups. Morning and evening serum PTX3 and high-sensitivity (hs) C-reactive protein (CRP) levels were measured before and after 3 mo of CPAP therapy. The baseline hs-CRP and PTX3 levels were higher in patients with moderate-to-severe OSA than in those with non-to-mild OSA. Moreover, the serum PTX3 levels, but not the hs-CRP levels, were significantly higher after than before sleep in the moderate-to-severe OSA group (morning PTX3, 1.96 ± 0.52; evening PTX3, 1.71 ± 0.44 ng/ml). OSA severity as judged using the AHI was significantly correlated with serum PTX3 levels but not hs-CRP levels. The highest level of correlation was found between the AHI and morning PTX3 levels (r = 0.563, P < 0.001). CPAP therapy reduced evening and morning serum hs-CRP and PTX3 levels in patients with moderate-to-severe OSA; however, the reduction in PTX3 levels in the morning was greater than that in the evening (morning -29.8 ± 16.7% vs. evening -12.6 ± 26.8%, P = 0.029). Improvement in the AHI score following CPAP therapy was strongly correlated with reduced morning PTX3 levels(r = 0.727, P < 0.001). Based on these results, morning PTX3 levels reflect OSA-related acute inflammation and are a useful marker for improvement in OSA following CPAP therapy.

Coronary endothelial function in patients with obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with increased risk for cardiovascular events, possibly mediated by endothelial dysfunction. The current study evaluates the association between invasive coronary endothelial dysfunction and OSA in patients with nonobstructive coronary atherosclerosis.

METHODS

All patients who had undergone both polysomnography and an invasive coronary vasomotor study at the Mayo Clinic, Rochester, Minnesota, from January 1997 to August 2011 were identified (n=143). OSA was defined as an apnea-hypopnea index of 5 or higher. Three endpoints of coronary endothelial function - percentage change in coronary artery diameter at the mid and distal left anterior descending artery to intracoronary acetylcholine and percentage change in coronary blood flow to intracoronary acetylcholine - were assessed. Differences between patients with OSA (n=102) and those without OSA (n=41) were evaluated using multivariate analysis of variance. Follow-up mortality data were collected and Kaplan-Meier curves were plotted to evaluate differences in mortality between patients with and without OSA.

RESULTS

Patients with OSA were more likely to have hypertension compared with patients without OSA. OSA was not significantly associated with coronary endothelial dysfunction on univariate analysis (P=0.23) and after adjustment for hypertension (P=0.19). Similarly, there was no significant difference in coronary endothelial function in patients who had oxygen desaturation of less than 90% during polysomnography (P=0.42). There was a trend toward higher mortality in patients with OSA compared with those without OSA, but this did not reach statistical significance (5 vs. 0% at 10 years, P=0.25).

CONCLUSION

The current study suggests that OSA is not an independent risk factor for coronary endothelial dysfunction in patients with early coronary atherosclerosis. Adverse coronary outcomes in patients with OSA may be independent of coronary endothelial dysfunction.

Real-time phase-contrast flow MRI of haemodynamic changes in the ascending aorta and superior vena cava during Mueller manoeuvre

AIM

To evaluate the potential of real-time phase-contrast flow magnetic resonance imaging (MRI) at 40 ms resolution for the simultaneous determination of blood flow in the ascending aorta (AA) and superior vena cava (SVC) in response to reduced intrathoracic pressure (Mueller manoeuvre).

MATERIALS AND METHODS

Through-plane flow was assessed in 20 healthy young subjects using real-time phase-contrast MRI based on highly undersampled radial fast low-angle shot (FLASH) with image reconstruction by regularized non-linear inversion. Haemodynamic alterations (three repetitions per subject = 60 events) were evaluated during normal breathing (10 s), inhalation with nearly closed epiglottis (10 s), and recovery (20 s).

RESULTS

Relative to normal breathing and despite interindividual differences, reduced intrathoracic pressure by at least 30 mmHg significantly decreased the initial peak mean velocity (averaged across the lumen) in the AA by -24 ± 9% and increased the velocity in the SVC by +28 ± 25% (p < 0.0001, n = 23 successful events). Respective changes in flow volume per heartbeat were -25 ± 9% in the AA and +49 ± 44% in the SVC (p < 0.0001, n = 23). Flow parameters returned to baseline during sustained pressure reduction, while the heart rate was elevated by 10% (p < 0.0001) after the start (n = 24) and end (n = 17) of the manoeuvre.

CONCLUSIONS

Real-time flow MRI during low intrathoracic pressure non-invasively revealed quantitative haemodynamic adjustments in both the AA and SVC.

Sleep-disordered breathing in hypertrophic cardiomyopathy: challenges and opportunities

Sleep-disordered breathing (SDB) may be a treatable risk factor in patients with hypertrophic cardiomyopathy (HCM), the most common inherited cardiomyopathy. Evidence suggests a high prevalence of SDB in HCM. We summarize the pathophysiology of SDB as it relates to hypertension, coronary artery disease, atrial fibrillation, and sudden cardiac death in patients with HCM. The implications regarding the care of patients with HCM and SDB are discussed as well as the knowledge deficits needing further exploration.

Sleep apnea prevalence in acute myocardial infarction--the Sleep Apnea in Post-acute Myocardial Infarction Patients (SAPAMI) Study

BACKGROUND

While sleep apnea (SA) might be a modifiable cardiovascular risk factor, recent data suggest that SA is severely underdiagnosed in patients after acute myocardial infarction (MI). There is limited evidence about day-night variation of onset of MI on dependence of having SA. We therefore investigated the prevalence of SA and examined the day-night variation of onset of MI in acute MI patients.

METHODS

We prospectively studied 782 consecutive patients admitted to the hospital with the diagnosis of acute MI. All subjects underwent sleep evaluations using a portable device after at least 48 h post-admission. Using the apnea-hypopnea index (AHI), groups were defined as patients without SA (<5 events/h), mild SA (5-15 events/h), moderate SA (15-30 events/h), and severe SA (≥ 30 events/h).

RESULTS

Almost all patients (98%) underwent urgent coronary angiography and 91% of patients underwent primary PCI. Using a threshold of AHI ≥ 5 events/h, SA was present in 65.7% of patients after acute MI. Mild SA was present in 32.6%, moderate in 20.4% and severe in 12.7%. The day-night variation in the onset of MI in all groups of SA patients was similar to that observed in non-SA patients. From 6 AM to 12 PM, the frequency of MI was higher in both SA and non-SA patients, as compared to the interval from 12 AM to 6 AM (all p<0.05).

CONCLUSION

There is a high prevalence of SA in patients presenting with acute MI. Peak time of MI onset in SA patients was between 6 AM and noon, similar to that in the general population. Whether diagnosis and treatment of SA after MI will significantly improve outcomes in these patients remains to be determined.

Effects of nighttime single-dose administration of vasodilating vs sympatholytic antihypertensive agents on sleep blood pressure in hypertensive patients with sleep apnea syndrome

Obstructive sleep apneas syndrome (OSAS) is associated with nocturnal hypertension with higher sleep blood pressure (BP) and its variability, both of which increase cardiovascular risk. In this crossover design study, the effect of nighttime single-dose administration of vasodilating (nifedipine 40 mg) vs sympatholytic (carvedilol 20 mg) antihypertensive agents on sleep BP in 11 hypertensive OSAS patients was evaluated. The authors recently developed a trigger sleep BP monitor with an oxygen-triggered function that initiates BP measurement when oxygen desaturation falls. The BP-lowering effects of nifedipine on the mean (P<.05) and minimum sleep systolic BPs (SBPs) (P<.01) were stronger than those of carvedilol. Sleep SBP surge (difference between the hypoxia-peak SBP measured by oxygen-triggered function and SBPs within 30 minutes before and after the peak SBP) was only significantly reduced by carvedilol (P<.05). The nighttime dosing of both vasodilating and sympatholytic antihypertensive drugs is effective to reduce sleep BP but with different BP-lowering profiles.

Obstructive sleep apnoea increases the incidence of morning peak of onset in acute myocardial infarction

AIMS

There exists a discrepancy regarding the relationship between obstructive sleep apnoea (OSA) and circadian variation during the onset of acute myocardial infarction (MI). We hypothesized that OSA patients show a characteristic circadian variation and that the severity of OSA significantly affects this variation.

METHODS AND RESULTS

The present study included 288 patients with first acute MI who underwent percutaneous coronary intervention within 12 h of symptom onset. The diagnosis of OSA required an apnoea-hypopnoea index (AHI) of ≥5 events/h. A total of 216 patients fulfilled the OSA criteria. The incidence of MI onset between 06:00 and 11:59 hours was significantly higher in OSA patients than in control patients (38 vs. 25%, p=0.039). Circadian variation in the morning peak of MI onset was attenuated in mild OSA (as defined by AHI, 5.0-14.9 events/h; 33 vs. 25%, p=0.240). Moderate-to-severe OSA (as defined by AHI ≥15.0 events/h) clearly increased the incidence of MI onset between 06:00 and 11:59 hours (43 vs. 25%, p=0.014). Multiple logistic regression adjusting for AHI (≥15.0 events/h), age, body mass index, hypertension, and current smoking showed that moderate-to-severe OSA significantly contributed to MI onset between 06:00 and 11:59 hours (odds ratio 2.00, p=0.010).

CONCLUSIONS

OSA showed a morning peak with regard to MI onset, and moderate-to-severe OSA significantly enhanced this circadian variation.

Obstructive Sleep Apnoea and Type 2 Diabetes

With the growing prevalence of obesity, the burden of type 2 diabetes is increasing. Obstructive sleep apnoea (OSA) is a very common medical condition that is associated with increased risk of cardiovascular disease and mortality. Obesity is a common risk factor for OSA and type 2 diabetes and hence it is not surprising that OSA and type 2 diabetes are interlinked. OSA has been shown to be an independent risk factor for the development of incident pre-diabetes/type 2 diabetes. OSA is also associated with worse glycaemic control and vascular disease in patients with type 2 diabetes. However, evidence for the benefits of OSA treatment in patients with type 2 diabetes is still lacking. The aim of this article is to provide an overview of OSA, the relationships between OSA and dysglycaemia and the impact of OSA in patients with type 2 diabetes, highlighting recent advances in the field.

Clinical implications of sleep disordered breathing in acute myocardial infarction

Background

Sleep disordered breathing (SDB), characterized by nightly intermittent hypoxia, is associated with multiple pathophysiologic alterations that may adversely affect patients with acute myocardial infarction (AMI). This prospective study investigated whether the metabolic perturbations associated with SDB are present when these patients develop AMI and if they affect clinical outcomes.

Methods

We prospectively enrolled 180 AMI patients. SDB was defined as oxygen desaturation index (ODI) >5 events/hour based on a Watch Pat-100 sleep study. Blood samples were obtained for high-sensitivity C-reactive protein (hs-CRP) and markers of oxidative stress (lipid peroxides [PD] and serum paraoxonase-1 [PON-1] (arylesterase activity). Echocardiography was performed to evaluate cardiac dimensions and pulmonary artery systolic pressure.

Results

SDB was present in 116 (64%) patients. Hs-CRP levels, PD and PON-1 were similar in patients with and without SDB. Echocardiography revealed higher left atrial dimension (4.1±0.5 vs 3.8±0.5 cm; P = 0.003) and a significant positive correlation between ODI and pulmonary artery systolic pressure (r = 0.41, P<0.0001). After a median follow up of 68 months, no significant differences were observed between the study groups with regard to clinical outcomes, including death, heart failure, myocardial infarction and unstable angina.

Conclusion

There is a high prevalence of previously undiagnosed SDB among patients with AMI. SDB in the setting of AMI is associated with higher pulmonary artery systolic pressure. SDB was not associated with adverse clinical outcomes.

Obstructive sleep apnea: no independent association to troponins

BACKGROUND

Cardiac troponins (cTn) are to date the most sensitive and specific biochemical markers of myocardial injury. Abnormal breathing patterns in patients with obstructive sleep apnea (OSA) may cause myocardial cell stress detectable by novel cTn assays. The objectives of this study were to investigate whether a new single-molecule cTnI (S-cTnI) assay and a commercially available high-sensitivity cTnT (hs-cTnT) assay would detect myocyte injury in individuals evaluated for possible OSA, and to explore their relation to variables of disordered breathing during sleep.

METHODS

Consecutive individuals referred to Lovisenberg Diakonale Hospital's sleep laboratory between 1 October 2009 and 1 March 2010 were included. We measured cTn in specimens collected the morning after sleep and studied these in relation to variables recorded during polygraphy or polysomnography.

RESULTS

All 222 (100 %) individuals had measurable cTn levels using either assay. Stratified into categories according to the apnea-hypopnea index (AHI), patients with OSA (AHI ≥5) had a different distribution of S-cTnI (P = 0.036) and hs-cTnT (P = 0.002) compared to those without (AHI <5). The median (quartiles 1-3) were 3.0 (1.9-6.0) versus 2.3 (1.6-3.8) ng/l for S-cTnI, and 7.0 (5.5-8.7) versus 6.2 (4.9-7.2) ng/l for hs-cTnT. However, in multiple median regression analyses adjusted for conventional predictors, neither S-cTnI (P = 0.57) nor hs-cTnT (P = 0.80) were significantly associated with AHI.

CONCLUSIONS

This study reveals no association independent of conventional predictors between OSA and myocardial cell injury measured by S-cTnI and hs-cTnT assays. Our findings support a search for novel biomarkers for prognostication of OSA.

Measuring comorbidity in cardiovascular research: a systematic review

Background. Everything known about the roles, relationships, and repercussions of comorbidity in cardiovascular disease is shaped by how comorbidity is currently measured. Objectives. To critically examine how comorbidity is measured in randomized controlled trials or clinical trials and prospective observational studies in acute myocardial infarction (AMI), heart failure (HF), or stroke. Design. Systematic review of studies of hospitalized adults from MEDLINE CINAHL, PsychINFO, and ISI Web of Science Social Science databases. At least two reviewers screened and extracted all data. Results. From 1432 reviewed abstracts, 26 studies were included (AMI n = 8, HF n = 11, stroke n = 7). Five studies used an instrument to measure comorbidity while the remaining used the presence or absence of an unsubstantiated list of individual diseases. Comorbidity data were obtained from 1-4 different sources with 35% of studies not reporting the source. A year-by-year analysis showed no changes in measurement. Conclusions. The measurement of comorbidity remains limited to a list of conditions without stated rationale or standards increasing the likelihood that the true impact is underestimated.

Rationale and methodology of the impact of continuous positive airway pressure on patients with ACS and nonsleepy OSA: the ISAACC Trial

BACKGROUND

Obstructive sleep apnea (OSA) is common in acute coronary syndrome (ACS) and a possible cause of increased morbidity and mortality.

OBJECTIVES

The main objective is to determine in patients with ACS and OSA if CPAP treatment reduces the incidence of cardiovascular events (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, and hospitalization for unstable angina or transient ischemic attack). The secondary objectives are to determine the prevalence of nonsleepy OSA in patients with ACS; assess the effect of CPAP on the incidence of newly diagnosed diabetes mellitus, symptoms, and quality of life; identify biomarkers of risk involved in cardiovascular complications in these patients; and conduct a cost-effectiveness analysis of diagnosis and treatment.

POPULATION AND METHODOLOGY

Multicenter, prospective, randomized and controlled study. Patients are admitted to the coronary care unit with diagnosis of ACS and without daytime sleepiness (Epworth Sleepiness Scale ≤10) at 15 teaching hospitals in Spain. All patients undergo a sleep study by cardiorespiratory polygraphy. Patients with an apnea-hypopnea index ≥15/hour will be randomized to treatment with CPAP (group 1, 632 patients) or conservative treatment (group 2, 632 patients). Patients with an apnea-hypopnea index <15/hour (group 3, 600 patients) will be followed as a reference group. Patients will be monitored at baseline (T0), 1 month (T1), 3 months (T2), 6 months (T3), 12 months (T4), and every 6 months thereafter (where applicable) during the follow-up period.

CONCLUSIONS

The ISAACC trial will contribute to evaluating the effect of CPAP treatment on cardiovascular events in patients with ACS and OSA.

Association of sleep onset of acute coronary syndrome with sleep apnea syndrome and abnormal diurnal variation of hemostasis and adipokine levels

Our aim was to examine the pathophysiology of sleep onset of acute coronary syndrome (ACS); in particular, we focused on the association of sleep onset of ACS, sleep-apnea syndrome (SAS), and diurnal variation of hemostasis and adipokine levels. Seventy-four patients (mean 60.0 years; 84% men) with ACS were cross-sectionally examined. They were examined by circulatory levels of hemostasis [plasminogen activator inhibitor-1 (PAI-1), D-dimer, soluble fibrin] and adipokines (adiponectin, visfatin) before and after sleep, and cardiorespiratory function. The severity of SAS was defined as mild to no SAS [apnea-hypopnea index (AHI) <15/h, n = 30], moderate SAS (AHI 15-30/h, n = 26), and severe SAS (AHI >30/h, n = 18). Nineteen patients (26%) were diagnosed with sleep onset of ACS, and these patients had a greater extent of morning increase from the night-time levels of PAI-1 (median PAI-1 increase: +37.1 vs. +27.3 ng/ml; P = 0.01) and visfatin (median visfatin increase: +0.40 vs. +0.00 ng/ml; P = 0.08) than those who had daytime onset of ACS. Among patients who had sleep onset of ACS, 89% were diagnosed with moderate to severe SAS. According to the severity of SAS, the morning increase from the night-time levels of PAI-1 and visfatin became greater (median PAI-1 increase: +23.7 vs. +29.2 vs. +39.3 ng/ml; median visfatin increase: 0.00 vs. 0.00 vs. +0.45 ng/ml; both P < 0.05), and these differences remained unchanged even after adjustment for significant covariates (both P < 0.05). Patients who have sleep onset of ACS are likely to have high prevalence of SAS and abnormal diurnal variations of PAI-1 and visfatin levels.

Delirium after cardiac surgery: have we overlooked obstructive sleep apnea?

Obstructive sleep apnea is common in patients with cardiovascular disease. It is well known that cardiac surgery is a risk factor for delirium. Researchers have shown that obstructive sleep apnea is an independent risk factor for the occurrence of delirium. In this manuscript we speculate on how obstructive sleep apnea may increase the risk of delirium in patients with cardiac surgery. If this is found to be confirmed, we would have another target through which we can decrease the risk of delirium in this population.

Obstructive sleep apnea and coronary artery disease: from pathophysiology to clinical implications

Coronary artery disease (CAD) and obstructive sleep apnea (OSA) are both complex and significant clinical problems. The pathophysiological mechanisms that link OSA with CAD are complex and can influence the broad spectrum of conditions caused by CAD, from subclinical atherosclerosis to myocardial infarction. OSA remains a significant clinical problem among patients with CAD, and evidence suggesting its role as a risk factor for CAD is growing. Furthermore, increasing data support that CAD prognosis may be influenced by OSA and its treatment by continuous positive airway pressure (CPAP) therapy. However, stronger evidence is needed to definitely answer these questions. This paper focuses on the relationship between OSA and CAD from the pathophysiological effects of OSA in CAD, to the clinical implications of OSA and its treatment in CAD patients.

Relation between time of symptom onset of ST-segment elevation myocardial infarction and patient baseline characteristics: from the National Cardiovascular Data Registry

BACKGROUND

The presence of a morning excess of ST-segment elevation myocardial infarction (STEMI) has been observed. The relation between patient characteristics and timing of STEMI may provide insight into the biological processes responsible for this phenomenon.

HYPOTHESIS

Patient baseline characteristics will vary with timing of STEMI.

METHODS

We performed an analysis using a large national registry of unselected patients with STEMI (N=45,218). Patients were categorized by time of symptom onset: early (6 am-2 pm), late day (2 pm-10 pm), and overnight (10 pm-6 am) then evaluated for variations in characteristics.

RESULTS

A circadian variation in the timing of symptom onset of STEMI was observed (early 41%, late day 32%, and overnight 26%, P<0.001). Circadian variations in factors known to alter timing of events were seen, including lower rates of home β-blocker use, smoking, and diabetes, with early onset of STEMI symptoms. In addition, patients in the 6 am to 2 pm subgroup were more likely older, white race, and male, with higher rates of home aspirin use and lower rates of obesity. Higher rates of coexisting cardiovascular disease, including prior heart failure, 3-vessel coronary artery disease, and depressed left ventricular ejection fraction, were observed in the overnight group. More robust antiplatelet therapy with home clopidogrel use was not associated with a change in the timing of events.

CONCLUSIONS

A morning excess of STEMI continues to exist and represents a potential target for preventative strategies. Patient baseline characteristics vary with the onset of STEMI and may reflect a physiologic relationship between these factors and the timing of events.

Obstructive sleep apnea and oxygen therapy: a systematic review of the literature and meta-analysis

BACKGROUND

Hypoxemia is an immediate consequence of obstructive sleep apnea. Oxygen (O2) administration has been used as an alternative treatment in patients with obstructive sleep apnea (OSA) who do not adhere to continuous positive airway pressure (CPAP) in order to reduce the deleterious effects of intermittent hypoxemia during sleep. This systematic review aims to investigate the effects of O2 therapy on patients with OSA.

METHOD

We conducted a systematic search of the databases Medline, Embase, Cochrane Central Register of Controlled Trials (1(st) Quarter 2011), Cochrane Database of Systematic Reviews (from 1950 to February 2011). Our search strategy yielded 4,793 citations. Irrelevant papers were excluded by title and abstract review, leaving 105 manuscripts. We reviewed all prospective studies that included: (1) a target population with obstructive sleep apnea, (2) O2 therapy and/or CPAP as a study intervention, (3) the effects of O2 on the apnea-hypopnea index (AHI), nocturnal hypoxemia, or apnea duration.

RESULTS

We identified 14 studies including a total of 359 patients. Nine studies were of single cohort design, while 5 studies were randomized control trials with 3 groups (CPAP, oxygen, and placebo/sham CPAP). When CPAP was compared to O2 therapy, all but one showed a significant improvement in AHI. Ten studies demonstrated that O2 therapy improved oxygen saturation vs. placebo. However, the average duration of apnea and hypopnea episodes were longer in patients receiving O2 therapy than those receiving placebo.

CONCLUSION

This review shows that O2 therapy significantly improves oxygen saturation in patients with OSA. However, it may also increase the duration of apnea-hypopnea events.

Effect of continuous positive airway pressure on day/night rhythm of prothrombotic markers in obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with an increased risk of atherothrombotic events. A prothrombotic state might partially explain this link. This study investigated OSA patients' day/night rhythm of several prothrombotic markers and their potential changes with therapeutic continuous positive airway pressure (CPAP).

METHODS

The study included 51 OSA patients [apnea hypopnea index (AHI) ⩾10] and 24 non-OSA controls (AHI<10). Of the 51 OSA patients, 25 were randomized to CPAP and 26 to placebo-CPAP. Twelve blood samples were collected over a 24h period to measure prothrombotic markers. For the apneic patients these samples were collected before treatment and after 3weeks of treatment with either CPAP or placebo-CPAP. Day/night variation in prothrombotic markers was examined using a cosinor analysis.

RESULTS

Compared with controls, OSA patients showed lower mesor (mean) and amplitude (difference between maximum and minimum activity) of D-dimer. In unadjusted (but not in adjusted) analysis, patients showed higher mesor of plasminogen activator inhibitor-1 (p<0.05 in all cases). No significant group differences were seen in mesor and amplitude for either soluble tissue factor or von Willebrand factor, or the acrophase (time of the peak) and periodic pattern for any prothrombotic markers. There were no significant differences in changes of periodic pattern and in day/night rhythm parameters of prothrombotic markers pre- to post-treatment between the CPAP and placebo condition.

CONCLUSIONS

There may be altered day/night rhythm of some prothrombotic markers in OSA patients compared with controls. CPAP treatment for 3weeks did not affect day/night rhythm of prothrombotic markers in OSA patients differently from placebo-CPAP.

Association between QRS duration and obstructive sleep apnea

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Obstructive sleep apnoea and cardiovascular disease

Obstructive sleep apnoea (OSA) is a common health concern caused by repeated episodes of collapse of the upper airway during sleep. The events associated with OSA lead to brain arousal, intrathoracic pressure changes, and intermittent episodes of hypoxaemia and reoxygenation. These events activate pathways such as oxidative stress, sympathetic activation, inflammation, hypercoagulability, endothelial dysfunction, and metabolic dysregulation that predispose patients with OSA to hypertension and atherosclerosis. OSA is a common cause of systemic hypertension and should be suspected in hypertensive individuals, especially those with resistant hypertension. In patients with OSA, continuous positive airway pressure (CPAP) treatment reduces blood pressure, and its effects are related to compliance and baseline blood pressure. Evidence suggests that OSA is a risk factor for stroke and heart failure. An association between coronary heart disease and OSA seems to be limited to middle-aged men (30-70 years). Cardiac rhythm disorders occur in about half of patients with OSA, but their clinical relevance is still unknown. The association of OSA with cardiovascular risk is mainly based on studies in men, and an association has yet to be established in women. Data on older patients is similarly scarce. Currently, there is not enough evidence to support treatment with CPAP for primary or secondary prevention of cardiovascular disease.

Obstructive sleep apnea, detected by the Berlin Questionnaire: an associated risk factor for coronary artery disease

Obstructive sleep apnea (OSA), a risk factor for coronary artery disease, remains under diagnosed. We investigated if OSA identified by the Berlin Questionnaire (BQ) is associated with the risk of coronary artery disease. Cases were patients referred for elective coronariography. The cases were classified with significant coronary lesions (stenosis > 50% in an epicardial coronary) or without significant coronary lesions. Controls were selected from a population-based sample. Positive BQ results were identified in 135 (41.2%) of 328 cases, in contrast with 151 (34.4%) of 439 control subjects (p = 0.03). In a multinomial logistic analysis, the risk for OSA identified by the BQ was independently associated with coronary artery disease in cases with lesions of at least 50% (OR = 1.53; 95%CI: 1.02-2.30; p = 0.04). The risk from OSA identified by the BQ was higher in younger subjects (40-59 years) (OR = 1.76; 95%CI: 1.05-2.97; p = 0.03) and in women (OR = 3.56; 95%CI: 1.64-7.72; p = 0.001). In conclusion, OSA identified by the BQ greatly increases the risks of coronary artery disease in patients having significant coronary artery lesions indicated by anangiogram, particularly in younger individuals and in women.

Health effects of identifying patients with undiagnosed obstructive sleep apnea in the preoperative clinic: a follow-up study

BACKGROUND

Undiagnosed obstructive sleep apnea (OSA) is a highly prevalent breathing disorder. The purpose of this study was to determine the effects of preoperative screening and subsequent treatment for OSA on the health of patients.

METHODS

We conducted a two-year follow-up study of patients previously enrolled in a large prospective study in which patients were given the STOP questionnaire for OSA screening (n = 2,467). All patients who underwent a polysomnography were considered eligible (n = 211) and were asked to complete a paper-based mailed questionnaire. The severity of OSA, comorbidities, and treatment modalities and their effects were evaluated from the returned questionnaire. Research ethics board approval was obtained and returning the questionnaire implied informed patient consent.

RESULTS

The response rate was 67%. One hundred twenty-eight (82%) of the 156 patients who responded had OSA established by polysomnography. Among these 128 patients with OSA, 88 (69%) were prescribed continuous positive airway pressure (CPAP) therapy and 40 (31%) were prescribed other (non-CPAP) treatment. Among those 88 patients receiving CPAP, 40 (45%) were compliant and 48 (55%) were non-compliant. The CPAP compliant patients had a greater reduction in medication for comorbidities than the CPAP non-compliant or the other treatment group (38% vs 3% vs 0%, respectively; P < 0.001). A significant improvement in snoring, sleep quality, and daytime sleepiness was reported by CPAP compliant users compared with CPAP non-compliant or other treatment groups (P < 0.001).

CONCLUSION

The preoperative patients who were identified to have OSA and were compliant with CPAP use may have health benefits in terms of improved snoring, sleep quality, and daytime sleepiness. Timely diagnosis and treatment compliance may reduce symptoms of OSA and severity of associated comorbidities along with a reduction in medications.

Acute cardiopulmonary failure from sleep-disordered breathing

Sleep-disordered breathing (SDB) comprises a diverse set of disorders marked by abnormal respiration during sleep. Clinicians should realize that SDB may present as acute cardiopulmonary failure in susceptible patients. In this review, we discuss three clinical phenotypes of acute cardiopulmonary failure from SDB: acute ventilatory failure, acute congestive heart failure, and sudden death. We review the pathophysiologic mechanisms and recommend general principles for management. Timely recognition of, and therapy for, SDB in the setting of acute cardiopulmonary failure may improve short- and long-term outcomes.

Impact of sleep-disordered breathing, visceral fat accumulation and adiponectin levels in patients with night-time onset of acute coronary syndrome

Acute coronary syndrome (ACS) during sleep occurs at a relatively low frequency and the pathogenic background remains uncertain. The aim of the present study was to determine the significance of sleep-disordered breathing (SDB) and excess visceral fat with nocturnal dysregulation of adipocytokines in night-time onset of ACS. SDB, visceral fat area (VFA), and changes in circulating adipocytokine levels were assessed in 109 consecutive patients with ACS. SDB and VFA were assessed by cardiorespiratory monitoring and computed tomographic scan, respectively. Visceral fat accumulation was more common in patients with (12 to 7 a.m.) than without (7 to 12 a.m.) night-time onset of ACS (p <0.05). In patients with night-time onset of ACS, those with excess visceral fat were significantly more likely to have SDB and nocturnal dysregulation of adiponectin than those without such accumulation (p <0.05), but there was no difference between those with and without excess visceral fat (VFA cutoff 100 cm(2)) in patients with non-night-time onset of ACS. In conclusion, night-time onset of ACS is associated with excess visceral fat and SDB (referred as to "syndrome Z"). SDB and excess visceral fat are treatable risk factors. Decrease of excess visceral fat and treatment of SDB could be beneficial in in preventing nocturnal cardiac events.

Sleep-disordered breathing and excessive daytime sleepiness in patients with atrial fibrillation

BACKGROUND

An important consequence of sleep-disordered breathing (SDB) is excessive daytime sleepiness (EDS). EDS often predicts a favorable response to treatment of SDB, although in the setting of cardiovascular disease, particularly heart failure, SDB and EDS do not reliably correlate. Atrial fibrillation (AF) is another highly prevalent condition strongly associated with SDB. We sought to assess the relationship between EDS and SDB in patients with AF.

METHODS

We conducted a prospective study of 151 patients referred for direct current cardioversion for AF who also underwent sleep evaluation and nocturnal polysomnography. The Epworth Sleepiness Scale (ESS) was administered prior to polysomnography and considered positive if the score was ≥ 11. The apnea-hypopnea index (AHI) was tested for correlation with the ESS, with a cutoff of ≥ 5 events/h for the diagnosis of SDB.

RESULTS

Among the study participants, mean age was 69.1 ± 11.7 years, mean BMI was 34.1 ± 8.4 kg/m(2), and 76% were men. The prevalence of SDB in this population was 81.4%, and 35% had EDS. The association between ESS score and AHI was low (R(2) = 0.014, P = .64). The sensitivity and specificity of the ESS for the detection of SDB in patients with AF were 32.2% and 54.5%, respectively.

CONCLUSIONS

Despite a high prevalence of SDB in this population with AF, most patients do not report EDS. Furthermore, EDS does not appear to correlate with severity of SDB or to accurately predict the presence of SDB. Further research is needed to determine whether EDS affects the natural history of AF or modifies the response to SDB treatment.

Radiological Appearances of Oropharyngeal Soft Tissue Reduction with Bipolar Radio-Frequency Ablation in Sleep Disordered Breathing

To demonstrate and track the changes of bipolar radiofrequency volumetric tissue reduction (BRFVTR) induced lesions of the tongue base and soft palate in the treatment of sleep disordered breathing (SDB) in a pilot study.

Diagnostic accuracy of the Berlin Questionnaire in detecting sleep-disordered breathing in patients with a recent myocardial infarction

BACKGROUND

The Berlin Questionnaire (BQ) has been used to identify patients at high risk for sleep-disordered breathing (SDB) in a variety of populations. However, there are no data regarding the validity of the BQ in detecting the presence of SDB in patients after myocardial infarction (MI). The aim of this study was to determine the performance of the BQ in patients after MI.

METHODS

We conducted a cross-sectional study of 99 patients who had an MI 1 to 3 months previously. The BQ was administered, scored using the published methods, and followed by completed overnight polysomnography as the "gold standard." SDB was defined as an apnea-hypopnea index of ≥ 5 events/h. The sensitivity, specificity, and positive and negative predictive values of the BQ were calculated.

RESULTS

Of the 99 patients, the BQ identified 64 (65%) as being at high-risk for having SDB. Overnight polysomnography showed that 73 (73%) had SDB. The BQ sensitivity and specificity was 0.68 and 0.34, respectively, with a positive predictive value of 0.68 and a negative predictive value of 0.50. Positive and negative likelihood ratios were 1.27 and 0.68, respectively, and the BQ overall diagnostic accuracy was 63%. Using different apnea-hypopnea index cutoff values did not meaningfully alter these results.

CONCLUSION

The BQ performed with modest sensitivity, but the specificity was poor, suggesting that the BQ is not ideal in identifying SDB in patients with a recent MI.

Update on sleep and its disorders

Inadequate sleep and sleep disorders have important adverse consequences on multiple systems. This review covers three areas: (a) Genetic determinants of sleep disorders. Common gene variants with small effects have been identified for both restless legs syndrome and narcolepsy with cataplexy. Rare variants with large effects have been found in familial phase advance syndrome and in subjects with short sleep durations. (b) Obstructive sleep apnea (OSA). OSA is an oxidative stress disorder. Prospective cohort studies show an increased risk of cardiovascular events in patients with untreated severe OSA. (c) The impact of sleep disorders on obesity and diabetes. Inadequate sleep results in changes in insulin resistance and in hormone levels leading to increases in appetite. Hence, inadequate sleep is associated with development of obesity. OSA is also an independent risk factor for insulin resistance; treatment of OSA can improve insulin sensitivity.

Sleep apnea in congestive heart failure

Obstructive sleep apnea (OSA) is a form of sleep disordered breathing in which pharyngeal muscle relaxation leads to recurrent nighttime apneas and hypopneas that, through increased afterload, intermittent hypoxia, and excess sympathetic activity, weaken the already failing heart. This review presents the current evidence regarding the complex relationship between OSA and heart failure (HF), including support for OSA as both a cause and consequence of HF. The impact of OSA on other cardiovascular diseases, such as hypertension, ischemic heart disease and arrhythmias, as they relate to HF development or exacerbation, also are reviewed.

Complicated course of ischemic heart disease in a patient with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) can activate pathological routes which can lead to insulin resistance, development of atherosclerosis and hypertension. The combination of hypertension and OSA has an additive effect on the development of atherosclerosis. As a number of studies have revealed, that the incidence of OSA in patients with myocardial infarction is likely to be high.

METHODS AND RESULTS

We present a patient with acute myocardial infarction and no classical coronary artery disease risk factors: non-smoker, normal blood pressure, normal total and low-density lipoprotein cholesterol levels, borderline high-density lipoprotein cholesterol level, with good physical activity, no diabetes mellitus, no abdominal obesity, a negative family history. The only risk factor was untreated obstructive sleep apnea. The course of disease was complicated by subsequent in-stent restenosis and progression of atherosclerotic plaques, which led to the need for acute coronary artery bypass graft surgery complicated by consecutive in-anastomosis stenosis despite maximum cardiovascular therapy. One year of continuous positive airway pressure treatment was needed to stabilize his health condition, which is now stable for up to two years.

CONCLUSIONS

Given the complicated course of ischemic heart disease in patients with OSA, we believe that OSA diagnosis would be advisable each time these patients with symptoms of myocardial infarction, ischemic heart disease and OSA are examined. Even more important, however, is proper treatment of the OSA when it is present.