Severity of obstructive sleep apnea is associated with cardiac troponin I concentrations in a community-based sample: data from the Akershus Sleep Apnea Project

Effects of obstructive sleep apnea on myocardial injury and dysfunction: a review focused on the molecular mechanisms of intermittent hypoxia

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxia (IH) and is strongly associated with adverse cardiovascular outcomes. Myocardial injury and dysfunction have been commonly observed in clinical practice, particularly in patients with severe OSA. However, the underlying mechanisms remain obscure. In this review, we summarized the molecular mechanisms by which IH impact on myocardial injury and dysfunction. In brief, IH-induced cardiomyocyte death proceeds through the regulation of multiple biological processes, including differentially expressed transcription factors, alternative epigenetic programs, and altered post-translational modification. Besides cell death, various cardiomyocyte injuries, such as endoplasmic reticulum stress, occurs with IH. In addition to the direct effects on cardiomyocytes, IH has been found to deteriorate myocardial blood and energy supply by affecting the microvascular structure and disrupting glucose and lipid metabolism. For better diagnosis and treatment of OSA, further studies on the molecular mechanisms of IH-induced myocardial injury and dysfunction are essential.

Is COPD the Determinant Factor for Myocardial Injury and Cardiac Wall Stress in OSA Patients?

Background and Objectives: Evidence shows that COPD-OSA overlap syndrome (OS) is more frequently accompanied by cardiovascular disease (CVD) in comparison to either disease alone. The aim of the study was to explore whether patients with OS have a higher burden of subclinical myocardial injury and wall stress compared with OSA patients. Materials and Methods: Consecutive patients, without established CVD, underwent polysomnography and pulmonary function testing, due to suspected sleep-disordered breathing. An equal number of patients with OS (n = 53, with an apnea hypopnea index (AHI) > 5/h and FEV1/FVC < 0.7) and patients with OSA (n = 53, AHI > 5/h and FEV1/FVC > 0.7) were included in the study. The detection of asymptomatic myocardial injury and wall stress was performed via the assessment of serum high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP), respectively. Results: OS patients were older (p < 0.001) and had worse hypoxemic parameters, namely average oxyhemoglobin saturation (SpO2) (p = 0.002) and time spent with SpO2 < 90% (p = 0.003) during sleep as well as daytime pO2 (p < 0.001), than patients with OSA. No difference was observed between groups in terms of Epworth Sleepiness Scale (p = 0.432) and AHI (p = 0.587). Both levels of hs-cTnT (14.2 (9.1-20.2) vs. 6.5 (5.6-8.7) pg/mL, p < 0.001) and NT-proBNP (93.1 (37.9-182.5) vs. 19.2 (8.3-35.4) pg/mL, p < 0.001) were increased in OS compared to OSA patients. Upon multivariate linear regression analysis, levels of NT-proBNP and hs-cTnT correlated with age and average SpO2 during sleep. Conclusions: Our study demonstrated higher levels of hs-cTnT and NT-proBNP in OS patients, indicating an increased probability of subclinical myocardial injury and wall stress, compared with OSA individuals.

The impact of sleep disordered breathing on cardiac troponin in acutely decompensated heart failure

PURPOSE

Sleep disordered breathing in decompensated heart failure has physiological consequences (e.g., intermittent hypoxemia) that may predispose to subclinical myocardial injury, yet a temporal relationship between sleep apnea and troponin elevation has not been established.

METHODS

We assessed the feasibility of performing respiratory polygraphy and measuring overnight high-sensitivity cardiac troponin T change in adults admitted to the hospital with acutely decompensated heart failure. Repeat sleep apnea tests (SATs) were performed to determine response to optimal medical heart failure therapy. Multivariable logistic regression was used to identify associations between absolute overnight troponin change and sleep apnea characteristics.

RESULTS

Among the 19 subjects with acutely decompensated heart failure, 92% of SATs demonstrated sleep disordered breathing (apnea-hypopnea index [AHI] > 5 events/h). For those with repeat SATs, AHI increased in 67% despite medical management of heart failure. Overnight troponin increase was associated with moderate to severe sleep apnea (vs. no to mild sleep apnea, odds ratio (OR = 18.4 [1.51-224.18]), central apnea index (OR = 1.11 [1.01-1.22]), and predominantly central sleep apnea (vs. obstructive, OR = 22.9 [1.29-406.32]).

CONCLUSIONS

Sleep apnea severity and a central apnea pattern may be associated with myocardial injury. Respiratory polygraphy with serial biomarker assessment is feasible in this population, and combining this approach with interventions (e.g., positive airway pressure) may help establish if a link exists between sleep apnea and subclinical myocardial injury.

Association between insomnia phenotypes and subclinical myocardial injury: the Multi-Ethnic Study of Atherosclerosis

STUDY OBJECTIVES

To assess whether the association between insomnia and subclinical myocardial injury, as measured by cardiac troponin T (cTnT), differs across insomnia phenotypes.

METHODS

We measured cTnT in 2188 participants in the Multi-Ethnic Study of Atherosclerosis study who had completed sleep questionnaires and undergone unattended polysomnography (PSG) and 7-day actigraphy. Insomnia symptoms were defined as reporting at least one of the following ≥5 nights/week over the past 4 weeks: trouble falling asleep, waking up several times a night, having trouble getting back to sleep after waking up too early, or taking sleeping pills to help falling asleep. Obstructive sleep apnea (OSA) was defined as an apnea-hypopnea index (AHI >15 events/h). Participants were classified into insomnia phenotypes, including comorbid insomnia and OSA (COMISA) and insomnia associated with actigraphy-estimated short sleep (<6 h) or sleep fragmentation.

RESULTS

The mean age was 68.8 (SD 9.2) years, 53.6% were male. In total, 47.8% met threshold levels for insomnia symptoms, and 43.1% had an AHI >15. In adjusted linear regression models COMISA (β 0.08 [standard error (SE) 0.03], p < .01) and insomnia with short sleep duration (β 0.07 [SE 0.03], p < .05) were each associated with higher cTnT compared to a reference group with no insomnia. Insomnia with fragmented sleep (β 0.03 [SE 0.02]) was not associated with higher cTnT (p > .05) in adjusted analyses. OSA was associated with higher cTnT (β 0.09 [SE 0.03], p < .01) in adjusted models.

CONCLUSIONS

COMISA and insomnia with short sleep duration, but not insomnia symptoms alone or fragmented sleep, were associated with increased circulating cTnT in older adults.

Effect of positive airway pressure on cardiac troponins in patients with sleep-disordered breathing: A meta-analysis

Background

Cardiac troponins are highly sensitive and specific biomarkers for cardiac injury. Previous studies evaluating the effect of positive airway pressure (PAP) on cardiac troponins in patients with sleep‐disordered breathing (SDB) have yielded conflicting results. The meta‐analysis was performed to examine the effect of PAP on cardiac troponins in SDB patients.

Methods

PubMed, Web of Science, and EMBASE before September 2021 on original English language studies were searched. The data on cardiac troponins in both baseline and post‐PAP treatment were extracted from all studies. The data on the change of cardiac troponins in both PAP and control group were extracted from randomized controlled trials. Standardized mean difference (SMD) was used to synthesize quantitative results.

Results

A total of 11 studies were included. PAP treatment was not associated with a significant change in cardiac troponin T between the baseline and post‐PAP treatment (SMD = −0.163, 95% confidence interval [CI] = −0.652 to 0.326, z = 0.65, p = .514). The pooled estimate of SMD of cardiac troponin I between the pre‐ and post‐PAP treatment was 0.287, and the 95% CI was −0.586 to 1.160 (z = 0.64, p = .519). The pooled SMD of change of cardiac troponin T between the PAP group and control group was −0.473 (95% CI = −1.198 to 0.252, z = 1.28, p = .201).

Conclusions

This meta‐analysis revealed that PAP treatment was not associated with any change of cardiac troponin in SDB patients.

Identification of Potential Diagnostic Biomarkers From Circulating Cells During the Course of Sleep Deprivation-Related Myocardial Infarction Based on Bioinformatics Analyses

Background

Myocardial infarction (MI) is the leading cause of death from non-infectious diseases worldwide and results in rapid deterioration due to the sudden rupture of plaques associated with atherosclerosis, a chronic inflammatory disease. Sleep is a key factor that regulates immune homeostasis of the body. The imbalance in circulating immune cells caused by sleep deprivation (SD) may represent a risk factor leading to the rapid deterioration of plaques and MI. Therefore, it is of profound significance to identify diagnostic biomarkers for preventing SD-related MI.

Methods

In the present study, we identified coexpressed differentially expressed genes (co-DEGs) between peripheral blood mononuclear cells from MI and SD samples (compared to controls) from a public database. LASSO regression analysis was applied to identify significant diagnostic biomarkers from co-DEGs. Moreover, receiver operating characteristic (ROC) curve analysis was performed to test biomarker accuracy and diagnostic ability. We further analyzed immune cell enrichment in MI and SD samples using the CIBERSORT algorithm, and the correlation between biomarkers and immune cell composition was assessed. We also investigated whether diagnostic biomarkers are involved in immune cell signaling pathways in SD-related MI processes.

Results

A total of 10 downregulated co-DEGs from the sets of MI-DEGs and SD-DEGs were overlapped. After applying LASSO regression analysis, SYTL2, KLRD1, and C12orf75 were selected and validated as diagnostic biomarkers using ROC analysis. Next, we found that resting NK cells were downregulated in both the MI samples and SD samples, which is similar to the changes noted for SYTL2. Importantly, SYTL2 was strongly positively correlated not only with resting NK cells but also with most genes related to NK cell markers in the MI and SD datasets. Moreover, SYTL2 was highly associated with genes in NK cell signaling pathways, including the MAPK signaling pathway, cytotoxic granule movement and exocytosis, and NK cell activation. Furthermore, GSEA and KEGG analyses provided evidence that the DEGs identified from MI samples with low vs. high SYTL2 expression exhibited a strong association with the regulation of the immune response and NK cell-mediated cytotoxicity.

Conclusion

In conclusion, SYTL2, KLRD1, and C12orf75 represent potential diagnostic biomarkers of MI. The association between SYTL2 and resting NK cells may be critically involved in SD-related MI development and occurrence.

Novel oxygen desaturation parameters are associated with cardiac troponin I: Data from the Akershus Sleep Apnea Project

Novel diagnostic markers for obstructive sleep apnea beyond the apnea-hypopnea index (AHI) have been introduced. There are no studies on their association with markers of subclinical myocardial injury. We assessed the association between novel desaturation parameters and elevated cardiac troponin I and T. Participants with polysomnography (498) from the Akershus Sleep Apnea study were divided into normal and elevated biomarker groups based on sex-specific concentration thresholds (cardiac troponin I: ≥4 ng/L for women, ≥6 ng/L for men; and cardiac troponin T: ≥7 ng/L for women, ≥8 ng/L for men). Severity of obstructive sleep apnea was evaluated with the AHI, oxygen desaturation index, total sleep time with oxygen saturation below 90% (T90), lowest oxygen saturation (Min SpO₂ %), and novel oxygen desaturation parameters: desaturation duration and desaturation severity. How the AHI and novel desaturation parameters predicted elevated cardiac troponin I and cardiac troponin T levels was assessed by the area under the curve (AUC). Based on multivariable-adjusted linear regression, the AHI (β = 0.004, p = 0.012), desaturation duration (β = 0.007, p = 0.004), and desaturation severity (β = 0.147, p = 0.002) were associated with cardiac troponin I levels but not cardiac troponin T. T90 was associated with cardiac troponin I (β = 0.006, p = 0.009) and cardiac troponin T (β = 0.005, p = 0.007). The AUC for the AHI 0.592 (standard error 0.043) was not significantly different from the AUC of T90 (SD 0.640, p = 0.08), desaturation duration 0.609 (SD 0.044, p = 0.42) or desaturation severity 0.616 (SD 0.043, p = 0.26) in predicting myocardial injury as assessed by cardiac troponin I. Oxygen desaturation parameters and the AHI were associated with cardiac troponin I levels but not cardiac troponin T levels. Novel oxygen desaturation parameters did not improve the prediction of subclinical myocardial injury compared to the AHI.

Sleep-disordered breathing and left ventricular scar on cardiac magnetic resonance: results of the Multi-Ethnic Study of Atherosclerosis

STUDY OBJECTIVES

The objectives of this study were to evaluate the independent association between sleep-disordered breathing (SDB) using overnight polysomnography and left ventricular (LV) scar using cardiac magnetic resonance (CMR) with late-gadolinium enhancement in a community-based cohort of the Multi-Ethnic Study of Atherosclerosis.

METHODS

Our analytical sample includes 934 participants from the fifth examination of the Multiethnic Study of Atherosclerosis who underwent both polysomnography and CMR. SDB was categorized as follows: no-SDB (apnea-hypopnea index [AHI] < 5 events/h), mild SDB (5 events/h ≤ AHI < 15 events/h), and moderate-severe SDB (AHI ≥ 15 events/h). LV scar was considered present if there was presence of scar on CMR (late-gadolinium enhancement > 0%). Logistic regression with multivariable adjustment for confounders (age, sex, race/ethnicity, body mass index, and cardiometabolic risk factors) was used to examine the independent association of SDB with LV scar. Confounders were identified using directed acyclic graphs.

RESULTS

The mean age of our sample was 67.0 ± 8.5 years (SD), with 49% (n = 461) females and a prevalence of SDB (AHI ≥ 5 events/h) of 63% (n = 590). LV scar was more prevalent in individuals with SDB (9.5%) versus those without SDB (3.8%; P < .01), and 88% of all LV scars were clinically unrecognized. After multivariable adjustment, both mild SDB and moderate-severe SDB were independently associated with LV scar (odds ratio, 2.53; 95% confidence interval, 1.13-5.64 and odds ratio, 2.31; 95% confidence interval, 1.01-5.24, respectively).

CONCLUSIONS

In a community-based cohort, SDB (including mild) is independently associated with a more than 2-fold increase in the odds of LV scar presence measured using CMR with late-gadolinium enhancement. Most LV scars were clinically unrecognized. The impact of SDB treatment on subclinical myocardial infarction needs to be investigated in future studies.

Effects of sleep apnea hypopnea syndromes on cardiovascular events: a systematic review and meta-analysis

PURPOSE

Previous studies suggest that sleep apnea hypopnea syndrome (SAHS) is an independent risk factor that contributes to certain cardiovascular events. However, there are studies arguing that patients with SAHS had lower peak troponin levels when suffering cardiovascular events compared to patients without SAHS, which indicates that there may potentially be a protective effect of SAHS. This meta-analysis aimed to assess the impact of SAHS on cardiovascular events.

METHODS

Databases were searched for studies that examined cardiac biomarkers or reported angiographic data when patients with SAHS experienced cardiovascular events. The data about peak cardiac biomarkers and angiographic coronary lesion were extracted and then used to compute the pooled standardized mean difference (SMD) and 95% confidence interval (95% CI).

RESULTS

Among 26 studies included in the meta-analysis, there was not a definite difference between the SAHS group and the control group for troponins (SMD, 0.05; 95% CI, [- 0.16, 0.26]), creatine kinase (SMD, - 0.08; 95% CI, [- 0.38, 0.22]), and CK-MB (SMD, - 0.11; 95% CI, [- 0.51, 0.29]). However, patients with SAHS revealed worse coronary lesion condition grading via both Gensini score (SMD, 0.63; 95% CI, [0.31, 0.95]) and SYNTAX score (SMD, 0.99; 95% CI, [0.31-1.67]).

CONCLUSIONS

Ischemic preconditioning induced by the intermittent hypoxia at the early stage could generate a cardiac protection effect, which would then benefit SAHS patients encountering a major adverse cardiovascular event.

The impact of obstructive sleep apnoea severity on cardiac structure and injury

BACKGROUND

Obstructive sleep apnoea (OSA) is an important factor in the development and progression of heart failure (HF). The prevalence of OSA is higher in patients with HF than in the general population. We sought to test the hypothesis that OSA severity was predictive of ventricular function and cardiac injury [as assessed by high-sensitivity cardiac troponin I(hs-cTnI)].

METHODS

A total of 60 patients were recruited after evaluation for sleep disturbances using the Jenkins Sleep Questionnaire (JSQ) and Epworth Sleepiness Scale (ESS). Subsequently, they underwent polysomnography thus confirming the diagnosis of OSA and were equally divided into three groups according to OSA severity grade. Following polysomnography, the next morning patients underwent venous blood sampling and echocardiography.

RESULTS

We observed a statistically significant association (P = 0.009) between diastolic dysfunction grades and severity grades of OSA. All the three diastolic dysfunction variables E/A ratio, deceleration time and E/e' ratio had a significant association(P < 0.05) with severity grades of OSA. There was a marginally significant positive correlation (ρ = 0.3244, p = 0.04) between AHI events per hour and mitral E/e' ratio. There was a statistically significant association(P < 0.001) between hs-cTnI value among different severity grades of OSA.

CONCLUSIONS

Here in our study, we found OSA a potential risk factor for development of myocardial injury and diastolic dysfunction. Severe grades of OSA are associated with higher grades of diastolic dysfunction and circulating levels of hs-cTnI. These data are consistent with the notion of a vicious cycle of frequent apnoea's or hypoxemia and recurrent myocardial injury, which could increase the risk of heart failure especially diastolic dysfunction in OSA.

Untreated Obstructive Sleep Apnea Is Associated With Myocardial Injury Independent of Blood Pressure Control in Hypertension

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) and hypertension are independent risk factors of cardiovascular morbidities. This study aims to investigate the relationship between OSA, blood pressure (BP) control, and myocardial injury in patients with difficult-to-control hypertension.

METHODS

Patients with hypertension who required three or more medications were prospectively recruited at a tertiary referral center. In-laboratory polysomnography, followed by blood tests for fasting glucose, glycated hemoglobin, lipids, high-sensitivity troponin I (hsTnI), B-type natriuretic peptide (BNP), C-reactive protein, and advanced oxidation protein products were performed. After polysomnography, 24-hour ambulatory BP monitoring was arranged.

RESULTS

A total of 98 participants were analyzed, with mean age 51 ± 9 years and body mass index 30 ± 5 kg/m². Previously undiagnosed severe OSA (apneahypopnea index [AHI] ≥ 30 events/h) was present in 51 patients (52%). hsTnI was negatively correlated with nocturnal dip in systolic BP (r = -.205, P = .048). After controlling for confounders, including BP control, AHI and oxygen desaturation index (ODI) were positively correlated with hsTnI (r = .282, P = .009 and r = .279, P = .010, respectively) and C-reactive protein (r = .302, P = .005 and r = .285, P = .008, respectively), but not with BNP or advanced oxidation protein products. Age, ODI, and loss of nocturnal systolic BP dip were significant determinants of hsTnI level (β = .225, P = .022; β = .293, P = .003; and β = -.215, P = .029; R² = .151). Age, female sex, 24-hour mean diastolic BP, and metabolic syndrome, but not indices of apnea severity, were predictors of BNP level.

CONCLUSIONS

Unrecognized severe OSA was common in patients with difficult-to-control hypertension, and OSA severity was associated with myocardial injury, independent of BP control with medications.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov, Title: A Cross-sectional Study of the Occurrence and Effect of Obstructive Sleep Apnea in Subjects With Resistant Hypertension, Identifier: NCT00843583, URL: https://clinicaltrials.gov/ct2/show/NCT00843583.

The association between circulating adiponectin levels, lung function and adiposity in subjects from the general population; data from the Akershus Sleep Apnea Project

BACKGROUND

Circulating adiponectin (ADPN) levels are inversely associated with disease severity in patients with chronic obstructive pulmonary disease (COPD), while studies assessing the relationship between ADPN and lung function in subjects from the general population have shown diverging results. Accordingly, we hypothesized that ADPN would be associated with lung function in a population-based sample and tested how abdominal adiposity, metabolic syndrome, and systemic inflammation influenced this association.

METHODS

We measured total ADPN in serum, forced vital capacity (FVC) and forced expiratory volume during the 1st second (FEV1) in 529 participants (median 50 years, 54.6% males) recruited from the general population. We assessed the association between ADPN and lung function by multivariate linear regression analyses and adjusted for age, gender, height, smoking habits, weight, body mass index, waist-hip ratio, metabolic syndrome, obstructive sleep apnoea (OSA) and C-reactive protein.

RESULTS

The median (interquartile range) level of serum ADPN was 7.6 (5.4-10.4) mg/L. ADPN levels were positively associated with FVC % of predicted (beta 3.4 per SD adiponectin, p < 0.001)) in univariate linear regression analysis, but the association was attenuated in multivariate analysis (standardized beta 0.03, p = 0.573)). Among co-variates only WHR significantly attenuated the relationship. ADPN levels were also associated with FEV1% of predicted in bivariate analysis that adjusted for smoking (beta 1.4, p = 0.042)), but this association was attenuated and no longer significant in multivariate analysis (standardized beta -0.06, p = 0.254)).

CONCLUSION

In this population-based sample no association between ADPN and lung function was evident after adjustment for covariates related to adiposity.

Stable Breathing in Patients With Obstructive Sleep Apnea Is Associated With Increased Effort but Not Lowered Metabolic Rate

Study objectives

In principle, if metabolic rate were to fall during sleep in a patient with obstructive sleep apnea (OSA), ventilatory requirements could be met without increased respiratory effort thereby favoring stable breathing. Indeed, most patients achieve periods of stable flow-limited breathing without respiratory events for periods during the night for reasons that are unclear. Thus, we tested the hypothesis that in patients with OSA, periods of stable breathing occur when metabolic rate (VO2) declines.

Methods

Twelve OSA patients (apnea-hypopnea index >15 events/h) completed overnight polysomnography including measurements of VO2 (using ventilation and intranasal PO2) and respiratory effort (esophageal pressure).

Results

Contrary to our hypothesis, VO2 did not differ between stable and unstable breathing periods in non-REM stage 2 (208 ± 20 vs. 213 ± 18 mL/min), despite elevated respiratory effort during stable breathing (26 ± 2 versus 23 ± 2 cmH2O, p = .03). However, VO2 was lowered during deeper sleep (244 to 179 mL/min from non-REM stages 1 to 3, p = .04) in conjunction with more stable breathing. Further analysis revealed that airflow obstruction curtailed metabolism in both stable and unstable periods, since CPAP increased VO2 by 14% in both cases (p = .02, .03, respectively). Patients whose VO2 fell most during sleep avoided an increase in PCO2 and respiratory effort.

Conclusions

OSA patients typically convert from unstable to stable breathing without lowering metabolic rate. During sleep, OSA patients labor with increased respiratory effort but fail to satisfy metabolic demand even in the absence of overt respiratory events.

Repercusiones cardiovasculares del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS)

En la población de sujetos con síndrome de apnea-hipopnea obstructiva del sueño se describen entidades clínicas cardiovasculares asociadas con esta entidad y que afectan su curso y pronóstico. Dentro de estas se encuentran hipertensión arterial, arritmias, enfermedad coronaria, insuficiencia cardíaca, hipertensión pulmonar y tromboembolismo venoso. Del mismo modo, se describen los mecanismos fisiopatológicos de estas asociaciones, su prevalencia e impacto. Dado que afectan el curso de la enfermedad y, por tanto, la severidad de la misma, estas entidades juegan un papel muy importante en la toma de decisiones al momento de ofrecer el mejor manejo en cada caso, el cual debe ser abordado de forma multidisciplinaria.

Biomarkers in Sleep Apnea and Heart Failure

PURPOSE OF REVIEW

Sleep-disordered breathing (SDB) is highly prevalent in heart failure (HF) and may confer significant stress to the cardiovascular system and increases the risk for future cardiovascular events. The present review will provide updates on the current understanding of the relationship of SDB and common HF biomarkers and the effect of positive airway pressure therapy on these biomarkers, with particular emphasis in patients with coexisting SDB and HF.

RECENT FINDINGS

Prior studies have examined the relationship between HF biomarkers and SDB, and the effect of SDB treatment on these biomarkers, with less data available in the context of coexisting SDB and HF. Overall, however, the association of SDB and circulating biomarkers has been inconsistent. Further research is needed to elucidate the relationship between biomarkers and SDB in HF, to evaluate the clinical utility of biomarkers over standard methods in large, prospective studies and also to assess the impact of treatment of SDB on these biomarkers in HF via interventional studies.

Accelerated tumor growth under intermittent hypoxia is associated with hypoxia-inducible factor-1-dependent adaptive responses to hypoxia

Mounting evidence has revealed a causative role of intermittent hypoxia (IH) in cancer progression in mouse models of obstructive sleep apnea (OSA), but most studies have focused on the effects of IH following tumor implantation using an exposure to single IH frequency. Thus, we aimed to investigate 1) the potential effect of IH on the initial tumor growth in patients with OSA without an interaction with other mechanisms induced by IH in mice and 2) the influence of the IH frequency on tumor growth, which were tested using pre-conditioning with IH (Pre-IH) and 2 different IH frequencies, respectively. Pre-IH was achieved by alternatively maintaining melanoma cells between normoxia (10 min, 21% O₂) and hypoxia (50 min, 1% O₂) for 7 days (12 cycles per day) before administering them to mice. The conditions for IH-1 and IH-2 were 90 s of 12% FiO₂ followed by 270s of 21% FiO₂ (10 cycles/h), and 90 s of 12% FiO₂ and 90 s of 21% FiO₂ (20 cycles/h), respectively, for 8 h per day. Tumor growth was significantly higher in the Pre-IH group than in the normoxia group. In addition, the IH-2 group showed more accelerated tumor growth compared to the normoxia and IH-1 groups. Immunohistochemistry and gene-expression results consistently showed the up-regulation of molecules associated with HIF-1α-dependent hypoxic adaptation in tumors of the Pre-IH and IH-2 groups. Our findings reveal that IH increased tumor progression in a frequency-dependent manner, regardless of whether it was introduced before or after in vivo tumor cell implantation.

Predictors of obstructive sleep apnoea in patients admitted for acute coronary syndrome

Identifying undiagnosed obstructive sleep apnoea (OSA) patients in cardiovascular clinics could improve their management. Aiming to build an OSA predictive model, a broad analysis of clinical variables was performed in a cohort of acute coronary syndrome (ACS) patients.

Sociodemographic, anthropometric, life-style and pharmacological variables were recorded. Clinical measures included blood pressure, electrocardiography, echocardiography, blood count, troponin levels and a metabolic panel. OSA was diagnosed using respiratory polygraphy. Logistic regression models and classification and regression trees were used to create predictive models.

A total of 978 patients were included (298 subjects with apnoea–hypopnoea index (AHI) <15 events·h−1and 680 with AHI ≥15 events·h−1). Age, BMI, Epworth sleepiness scale, peak troponin levels and use of calcium antagonists were the main determinants of AHI ≥15 events·h−1(C statistic 0.71; sensitivity 94%; specificity 24%). Age, BMI, blood triglycerides, peak troponin levels and Killip class ≥II were determinants of AHI ≥30 events·h−1(C statistic of 0.67; sensitivity 31%; specificity 86%).

Although a set of variables associated with OSA was identified, no model could successfully predict OSA in patients admitted for ACS. Given the high prevalence of OSA, the authors propose respiratory polygraphy as a to-be-explored strategy to identify OSA in ACS patients.

Relation of Erectile Dysfunction to Subclinical Myocardial Injury

The circulating concentration of cardiac troponin I (cTnI) is an index of subclinical myocardial injury in several patient populations and in the general population. Erectile dysfunction is associated with greater risk for cardiovascular events, but the association with subclinical myocardial injury is not known. We aimed to test the hypothesis that the presence and severity of erectile dysfunction is associated with greater concentrations of cTnI in the general population. The presence and severity of erectile dysfunction was assessed by administering the International Index of Erectile Function 5 (IIEF-5) questionnaire to 260 men aged 30 to 65 years recruited from a population-based study. Concentrations of cTnI were determined by a high-sensitivity (hs) assay. Hs-cTnI levels were significantly higher in subjects with than in those without erectile dysfunction (median 2.9 vs 1.6 ng/l; p <0.001). Men with erectile dysfunction (i.e., IIEF-5 sum score <22) were also significantly older; had a higher systolic blood pressure, lower estimated glomerular filtration rate, higher augmentation index and N-terminal pro-B-type natriuretic peptide; and had a higher prevalence of hypertension, diabetes mellitus, and previous coronary artery disease than subjects without erectile dysfunction. These covariates were adjusted for in a multivariate linear regression model, yet the IIEF-5 sum score remained significantly negatively associated with the hs-cTnI concentration (standardized β -0.206; p <0.001). In conclusion, the presence and severity of erectile dysfunction is associated with circulating concentrations of hs-cTnI, indicating subclinical myocardial injury independently of cardiovascular risk factors, endothelial dysfunction and heart failure biomarkers.

High-Sensitivity Troponin T vs I in Acute Coronary Syndrome: Prediction of Significant Coronary Lesions and Long-term Prognosis

BACKGROUND

High-sensitivity cardiac troponin (hs-cTn) T and I assays are established as crucial tools for the diagnosis of acute myocardial infarction (AMI), as they have been found superior to old troponin assays. However, eventual differences between the assays in prediction of significant coronary lesions and long-term prognosis in patients with acute coronary syndrome (ACS) have not been fully unraveled.

METHODS

Serum concentrations of hs-cTnT (Roche), hs-cTnI (Abbott), and amino-terminal pro-B-type natriuretic peptide (NT-proBNP; Roche) in 390 non-ST-elevation (NSTE) ACS patients were evaluated in relation to significant coronary lesions on coronary angiography (defined as a stenosis >50% of the luminal diameter, with need for revascularization) and prognostic accuracy for cardiovascular mortality, all-cause mortality, as well as the composite end point of cardiovascular mortality and hospitalizations for AMI or heart failure.

RESULTS

The mean (SD) follow-up was 2921 (168) days. Absolute hs-cTnI concentrations were significantly higher than the hs-cTnT concentrations. The relationship between analyzed biomarkers and significant coronary lesions on coronary angiography, as quantified by the area under the ROC curve (AUC), revealed no difference between hs-cTnT [AUC, 0.81; 95% CI, 0.77-0.86] and hs-cTnI (AUC, 0.81; 95% CI, 0.76-0.86; P = NS). NT-proBNP was superior to both hs-cTn assays regarding prognostic accuracy for both cardiovascular and all-cause mortality and for the composite end point during follow-up, also in multivariate analyses.

CONCLUSIONS

The hs-cTnT and hs-cTnI assays displayed a similar ability to predict significant coronary lesions in NSTE-ACS patients. NT-proBNP was superior to both hs-cTn assays as a marker of long-term prognosis in this patient group.

Sleep apnea in total joint arthroplasty patients and the role for cardiac biomarkers for risk stratification: an exploration of feasibility

Obstructive sleep apnea (OSA) is highly prevalent in patients undergoing total joint arthroplasty (TJA) and is a major risk factor for postoperative cardiovascular complications and death. Recognizing this, the American Society of Anesthesiologists urges clinicians to implement special considerations in the perioperative care of OSA patients. However, as the volume of patients presenting for TJA increases, resources to implement these recommendations are limited. This necessitates mechanisms to efficiently risk stratify patients having OSA who may be susceptible to post-TJA cardiovascular complications. We explore the role of perioperative measurement of cardiac troponins (cTns) and brain natriuretic peptides (BNPs) in helping determine which OSA patients are at increased risk for post-TJA cardiovascular-related morbidity.

Natriuretic Peptide and High-Sensitive Troponin T Concentrations Correlate with Effectiveness of Short-Term CPAP in Patients with Obstructive Sleep Apnea and Coronary Artery Disease

The risk of cardiovascular complications is increased in patients with obstructive sleep apnea (OSA). Continuous positive airway pressure (CPAP) is the most effective way to treat clinically significant OSA. We hypothesized that the concentrations of the cardiac risk markers N-terminal brain natriuretic peptide (NT-proBNP) and high-sensitive troponin T (hs-TropT) correlate with the effectiveness of CPAP therapy in patients with OSA and coexisting coronary artery disease (CAD). Twenty-one patients with severe OSA and coexisting CAD (group 1) and 20 control patients with severe OSA alone (group 2) were treated with CPAP and monitored by laboratory-based polysomnography. NT-proBNP and hs-TropT levels were measured before and after CPAP. Apnea-hypopnea index (AHI) and oxygen desaturation were similar in both groups. In group 1, hs-TropT levels correlated with AHI and oxygen desaturation upon CPAP. Elevated NT-proBNP levels in group 1 were significantly reduced by CPAP. NT-proBNP levels correlated with AHI and showed negative correlation with ST-segment depression. No such correlations were found in group 2. CPAP has the potential to normalize elevated NT-proBNP serum levels in patients with severe OSA and coexisting CAD. Levels of NT-proBNP and hs-TropT correlated with AHI and oxygen desaturation.

Biomarkers of cardiovascular injury and stress are associated with increased frequency of ventricular ectopy: a population-based study

BACKGROUND

Asymptomatic ventricular arrhythmias are common and associated with increased risk of cardiovascular mortality. Cardiac troponins, natriuretic peptides and C-reactive protein (CRP) are also predictive of adverse cardiovascular events in the general population, but limited information is available on the relationship between these biomarkers and ventricular ectopy in a community-based population. The objectives were to evaluate the associations between ventricular ectopic activity and N-terminal pro-B-type natriuretic peptide (NT-proBNP), high sensitivity-troponin I (hs-TnI) and hs-CRP in a community-based setting.

METHODS

We performed a 24 h Holter-recording and blood sampling in 498 subjects. Premature ventricular complexes (PVC) were classified as frequent at >5/h and the presence of any bigeminy, trigeminy or non-sustained ventricular tachycardia were classified as complex ventricular ectopy. The associations between biomarkers and ventricular arrhythmias were investigated by univariate and multivariate logistic regression analyses.

RESULTS

Frequent PVC's and complex ventricular ectopy were detected in 46 (9%) and 47 (9%) participants respectively, and were associated with significantly (p < 0.001) higher concentrations of NT-proBNP and hs-TnI. The association between NT-proBNP and both frequent PVC's (p = 0.020) and complex ventricular ectopy (p = 0.001) remained significant after adjusting for conventional risk markers in multivariate analyses.

CONCLUSION

Increased level of NT-proBNP was independently associated with ventricular ectopy, whereas no independent association was observed between hs-TnI and hs-CRP levels and ventricular ectopy in this community-based sample.

Obstructive sleep apnea and its effects on cardiovascular diseases: a narrative review

Obstructive sleep apnea (OSA) occurs in 5%-14% of adults but is often undiagnosed. Apneas cause acute physiological changes, including alveolar hypoventilation and pulmonary artery vasoconstriction; they also promote chronic vascular disease secondary to increased platelet adhesiveness, endothelial dysfunction, and accelerated atherosclerosis. The Sleep Heart Health Study demonstrated that OSA is a risk factor for stroke and that an increase of 1 unit in the apnea-hypopnea index increases stroke risk by 6% in men. Patients with OSA frequently have atrial fibrillation (AF). Patients with OSA and AF have an increased incidence of stroke compared with patients with only OSA. The treatment of OSA with CPAP reduces the incidence of stroke and decreases the recurrence rate of AF in patients undergoing pulmonary vein ablation procedures. Undertreated OSA has the potential to complicate the postoperative course of patients undergoing cardiac surgery and increase the frequency of arrhythmias and ischemic events. However, one prospective study demonstrated that OSA did not increase complications during the first 30 days following surgery but increased complications during the long-term follow-up. OSA is associated with increased atherosclerotic coronary disease and the development of coronary events and congestive heart failure. In summary, patients with OSA have an increased frequency of stroke and AF The treatment of these patients with CPAP reduces the frequency of stroke and AF recurrence rate in patients with AF undergoing either medical management or invasive procedures. However, well-designed clinical trials are necessary to answer critical questions regarding the management of OSA in patients with cardiovascular diseases.

A clinical approach to obstructive sleep apnea as a risk factor for cardiovascular disease

Obstructive sleep apnea (OSA) is associated with cardiovascular risk factors, cardiovascular diseases, and increased mortality. Epidemiological studies have established these associations, and there are now numerous experimental and clinical studies which have provided information on the possible underlying mechanisms. Mechanistic proof-of-concept studies with surrogate endpoints have been performed to demonstrate that treatment of OSA by continuous positive airway pressure (CPAP) has the potential to reverse or at least to attenuate not only OSA but also the adverse cardiovascular effects associated with OSA. However, no randomized studies have been performed to demonstrate that treatment of OSA by CPAP improves clinical outcomes in patients with cardiovascular risk factors and/or established cardiovascular disease and concomitant OSA. In the present review, we summarize the current knowledge on the role of OSA as a potential cardiovascular risk factor, the impact of OSA on cardiac function, the role of OSA as a modifier of the course of cardiovascular diseases such as coronary artery disease, atrial fibrillation, and heart failure, and the insights from studies evaluating the impact of CPAP therapy on the cardiovascular features associated with OSA.

Chronic Kidney Disease and Sleeping Disordered Breathing (SDB)

The outlines of the current manuscript are: 1. Re-establish the link between hypertension and SDB including prevalence, mechanism, and reversal of process (i.e. improvement in hypertension with improvement in SDB), why it is important-cardiovascular mortality with numbers. 2. Re-establish the link between hypertension and CKD including same points as above. Then ask if both CKD and SDB are combined, what happens to hypertension and cardiovascular mortality. 3. Lastly, talk about links between CKD and SDB on how each process feeds on the other and is a growing, common problem.

Sex-Specific Association of Sleep Apnea Severity With Subclinical Myocardial Injury, Ventricular Hypertrophy, and Heart Failure Risk in a Community-Dwelling Cohort: The Atherosclerosis Risk in Communities-Sleep Heart Health Study

BACKGROUND

Risk factors for obstructive sleep apnea (OSA) and the development of subsequent cardiovascular (CV) complications differ by sex. We hypothesize that the relationship between OSA and high-sensitivity troponin T (hs-TnT), cardiac structure, and CV outcomes differs by sex.

METHODS AND RESULTS

Seven hundred fifty-two men and 893 women free of CV disease participating in both the Atherosclerosis Risk in the Communities and the Sleep Heart Health Studies were included. All participants (mean age, 62.5 ± 5.5 years) underwent polysomnography and measurement of hs-TnT. OSA severity was defined by using established clinical categories. Subjects were followed for 13.6 ± 3.2 years for incident coronary disease, heart failure, and CV and all-cause mortality. Surviving subjects underwent echocardiography after 15.2 ± 0.8 years. OSA was independently associated with hs-TnT among women (P=0.03) but not in men (P=0.94). Similarly, OSA was associated with incident heart failure or death in women (P=0.01) but not men (P=0.10). This association was no longer significant after adjusting for hs-TnT (P=0.09). Among surviving participants without an incident CV event, OSA assessed in midlife was independently associated with higher left ventricle mass index only among women (P=0.001).

CONCLUSIONS

Sex-specific differences exist in the relationship between OSA and CV disease. OSA, assessed in midlife, is independently associated with higher levels of concomitantly measured hs-TnT among women but not men, in whom other comorbidities associated with OSA may play a more important role. During 13-year follow-up, OSA was associated with incident heart failure or death only among women, and, among those without an incident event, it was independently associated with left ventricular hypertrophy only in women.

Markers of Myocardial Ischemia in Patients With Coronary Artery Disease and Obstructive Sleep Apnea: Effect of Continuous Positive Airway Pressure Therapy

BACKGROUND

Obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular complications. OSA and coronary artery disease (CAD) share the same risk factors and coexist in many patients. In previous studies, repeated nocturnal cardiac ischemic events in OSA patients with CAD have been reported.

HYPOTHESIS

We hypothesized that OSA may precipitate myocardial ischemia, evidenced by ST-segment depression and elevated N-terminal brain natriuretic peptide (NT-proBNP) and high-sensitivity troponin T (hs-TropT) levels in patients with severe OSA and concomitant CAD. We also aimed to evaluate if the effects could be reversed by continuous positive airway pressure (CPAP) therapy.

METHODS

Twenty-one patients with severe OSA (apnea-hypopnea index >15/h, nadir oxygen desaturation ≤ 80%), and coexisting CAD underwent in-hospital polysomnography at baseline and under CPAP. Blood samples for hs-TropT and NT-proBNP measurements were drawn prior and immediately after sleep. ST-segment depression was measured at the time of maximum oxygen desaturation during sleep.

RESULTS

CPAP significantly decreased elevated NT-proBNP levels from 475 ± 654 pg/mL before sleep to 353 ± 573 pg/mL after sleep and attenuated ST-segment depression during sleep. hs-TropT was not elevated and did not differ after nocturnal oxygen desaturation at baseline and after CPAP.

CONCLUSIONS

CPAP significantly reduced NT-proBNP in patients suffering from severe OSA and coexisting CAD. Repeated nocturnal myocardial ischemia did not cause myocyte necrosis evidenced by elevated hs-TropT or ST-segment depression.

Markers of Myocardial Ischemia in Patients with Obstructive Sleep Apnea and Coronary Artery Disease

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxia during sleep. We tested the hypothesis that nocturnal myocardial ischemia is detectable by ST segment depression and elevation of high sensitive troponin T (hsTrop T) and B-type natriuretic peptide (NT-proBNP) in patients with OSA and coexisting coronary artery disease (CAD). Twenty-one patients with OSA and CAD and 20 patients with OSA alone underwent in-hospital polysomnography. Blood samples for hsTrop T and NT-proBNP measurements were drawn before and after sleep. ST segment depression was measured at the time of maximum oxygen desaturation during sleep. The apnea-hypopnea-index (AHI), oxygen saturation nadir, and time in bed with oxygen saturation of ≤80% were similar in both groups. Levels of hsTrop T and NT-proBNP did not differ significantly before and after sleep but NT-proBNP levels were significantly higher in patients suffering from OSA and CAD compared to patients with OSA alone. No significant ST depression was found at the time of oxygen saturation nadir in either group. Despite the fact that patients with untreated OSA and coexisting CAD experienced severe nocturnal hypoxemia, we were unable to detect myocardial ischemia or myocyte necrosis based on significant ST segment depression or elevation of hsTrop T and NT-proBNP, respectively.