Karim, Shahid

Sleep is an active period of profound autonomic fluctuation, cycling between the parasympathetic dominance of nonrapid eye movement sleep and the sympathetic/parasympathetic volatility of rapid eye movement sleep. Sleep-disordered breathing, a spectrum of disorders marked by recurrent ventilatory instability and intermittent hypoxia during sleep, particularly obstructive sleep apnea, pathologically amplifies this volatility, transforming sleep into a nightly cascade of severe autonomic and hemodynamic stress. The cardinal features of sleep-disordered breathing, intermittent hypoxia, recurrent arousals, and marked intrathoracic pressure swings, act synergistically to drive chronic, 24-hour sympathetic overactivity, chemoreflex sensitization, and maladaptive neuroplasticity. These effects are mediated at a cellular level by oxidative stress, systemic inflammation, endothelial dysfunction, and neuroendocrine dysregulation. This persistent autonomic reset provides a direct mechanistic link to cardiovascular consequences. It is likely a primary driver of hypertension, blunting the nocturnal blood pressure dip and promoting sustained 24-hour sympathoexcitation. It fosters a proarrhythmic substrate for atrial fibrillation through mechanical stress, which drives atrial remodeling and autonomic conflict. Furthermore, sleep-disordered breathing contributes to myocardial ischemia by increasing myocardial oxygen demand and promoting a prothrombotic state. Beyond chronic disease, sleep-related autonomic shifts can act as acute triggers for malignant arrhythmias in individuals with vulnerable substrates, such as inherited channelopathies, a risk that may be significantly amplified by comorbid sleep-disordered breathing. This review delineates the critical neural and cellular pathways connecting sleep, autonomic dysregulation, and cardiovascular risk.

ABSTRACT Background and Purpose White matter hyperintensities (WMH) are a core neuroimaging marker of cerebral small vessel disease (CSVD). Sleep apnoea (SA) is a recognized vascular risk factor, but its associations with regional WMH burden, short‐interval WMH change and cognitive performance in population‐based cohorts remain incompletely defined. We examined these associations in the UK Biobank imaging cohort. Methods We conducted cross‐sectional analyses with an exploratory longitudinal subset in propensity score–matched cohorts excluding major neurologic and cerebrovascular disease before imaging. SA was identified from hospital records and self‐reports prior to brain magnetic resonance imaging (MRI). Head‐size–normalized WMH volumes were analysed on the log1p scale using multivariable linear regression with robust standard errors. Total WMH was the primary outcome; periventricular WMH (PWMH), deep WMH (DWMH) and cognitive measures were secondary outcomes. Mediation analyses evaluated WMH as a mediator of SA–cognition associations. Results In cross‐sectional analyses ( N = 12,890; mean age, 67.4 years; 27.2% women), SA was associated with greater WMH burden. Total WMH volume was 10.7% higher among participants with SA (95% CI, 5.0%–16.6%; p < 0.001). PWMH and DWMH volumes were 10.0% (95% CI, 4.7%–15.7%; q < 0.001) and 15.7% (95% CI, 7.1%–25.1%; q < 0.001) higher, respectively. SA was associated with modestly worse cognitive performance, with effect estimates attenuated after adjustment for WMH burden and cardiometabolic conditions. Mediation analyses indicated that WMH burden, particularly PWMH, mediated associations between SA and cognitive performance. In the longitudinal subset ( N = 698; median follow‐up, 2.26 years), no significant between‐group differences were observed in annualized WMH change. Conclusions In this large population‐based imaging cohort, SA was associated with higher WMH burden, a key neuroimaging marker of CSVD. Cognitive differences were modest, but WMH burden, particularly PWMH, consistently mediated associations between SA and cognitive performance. Longer term studies are needed to clarify temporal relationships and potential treatment effects.

Establishes a robust long-term human adipocyte organoid culture system maintained for over 90 days. Recapitulates key features of OSA-related intermittent hypoxia in human adipocytes in vitro. Demonstrates IH-induced adipocyte aging, including ultrastructural damage and epigenetic reprogramming. Identifies impaired adipogenesis and insulin signaling under intermittent hypoxia. Provides a physiologically relevant platform for mechanistic studies and drug screening.

Abstract Background Obstructive sleep apnea (OSA) is a risk factor for hypertension and some evidence suggests this risk may not be mitigated with positive airway pressure. Low-intensity statin therapy can modestly reduce blood pressure (BP). In this exploratory analysis, we examined if six months of high-intensity statin therapy could lower resting or ambulatory BP in patients with OSA. Methods 39 patients with OSA (13F, age = 49 ± 9yrs, body mass index = 32.9 ± 4.2kg/m2, apnea-hypopnea index = 22.2 ± 12.4 events/hour) were randomized to high-intensity atorvastatin or placebo. BP was assessed using seated, “office” measurements and in 20-minute intervals over 24 consecutive hours at three timepoints (baseline, three- and six-months post-randomization). Participants maintained a diary denoting sleep and wake times for analysis. Changes (Δ) in BP from baseline were assessed and adjusted for adherence to participants’ intervention (atorvastatin or placebo) as well as to their treatment for OSA (yes or no). Results There were no between-group differences in baseline BP variables (P = .09-.96). At three months, the changes in resting (P = .74-.87), 24 hour mean (P = .54-.96), daytime (P = .70-.96), nor nighttime (P = .74-.96) BP did not differ between groups. Similarly, the changes in resting (P = .23-.92), 24 hour mean (P = .51-.82), daytime (P = .17-.78), and nighttime (P = .51-1.00) BP did not differ between groups following six months of their respective intervention. Conclusions Our data suggest that high-intensity atorvastatin does not lower resting or ambulatory BP in patients with OSA relative to a placebo. Thus, it does not appear that atorvastatin is a viable adjunct intervention for BP reduction in patients with OSA. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03308578.

Importance Sleep disordered breathing (SDB) is a well-established contributor to cardiovascular morbidity, mediated by intermittent hypoxemia, autonomic dysregulation, and endothelial dysfunction. Patients with hypertrophic cardiomyopathy (HCM) may be especially at risk for SDB, but the clinical impact of SDB in this population remains unclear. Objective To define the prevalence and subtypes of SDB in HCM and examine their association with echocardiographic parameters and cardiac biomarker expression. Design, Setting, and Participants A prospective cohort study was conducted between April 18, 2018, and January 15, 2024, at a single tertiary referral center specializing in HCM care. Adults with HCM (left ventricular wall thickness ≥15 mm or pathogenic variants) were recruited from an institutional registry. Patients diagnosed with SDB or current pregnancy were excluded. Patients underwent polysomnography, with comparative assessment of echocardiographic, electrocardiographic, and biomarker indices. Observers were blinded to polysomnographic results. Data analysis was performed from April 11, 2024, to July 25, 2024. Exposures SDB classified via polysomnography using apnea-hypopnea index thresholds, with subtypes including obstructive sleep apnea and central sleep apnea and with event severity, hypoxemia, and sleep architecture disruption quantified. Main Outcomes and Measures Echocardiographic indices, cardiac biomarker expression, functional status, apnea-hypopnea index, and overnight hypoxemia. Results Among 154 patients (median [IQR] age, 60 [48-68] years; 102 [66.2%] male), 91 (59.1%) were diagnosed with SDB. Those with SDB, compared with those without SDB, had higher left ventricular mass index (median [IQR], 128 [107-161] vs 109 [96-134] g/m 2 ; P = .03), E/e′ ratio (median [IQR], 12.5 [10.0-15.0] vs 10.0 [8.3-14.5]; P = .04), and baseline troponin-T level (median [IQR], 0.013 [0.009-0.022] vs 0.011 [0.007-0.015] ng/mL [to convert to micrograms per liter, multiply by 1]; P = .04) and greater overnight troponin-T level increases (change in median [IQR], 0.0021 [−0.0029 to 0.0062] vs 0.0002 [−0.0022 to 0.0026] ng/mL; P = .02). New York Heart Association class II or III symptoms were more common in those with SDB (48 [52.7%] vs 17 [27.0%]; P = .005). Hypertension and diabetes were more prevalent among patients with SDB than without SDB (hypertension: 67 [73.6%] vs 36 [57.1%]; P = .03; diabetes: 14 [15.4%] vs 3 [4.8%]; P = .04), whereas rates of atrial fibrillation and prior myectomy did not differ significantly between groups. Conclusions and Relevance This study suggests that undiagnosed SDB is highly prevalent in patients with HCM and that SDB is associated with adverse myocardial remodeling, greater diastolic dysfunction, and elevated troponin-T levels, indicating subclinical myocardial injury. SDB may contribute to HCM pathophysiology and symptom burden, supporting the rationale for randomized clinical trials to determine the impact of treating SDB on symptoms and clinical outcomes in patients with HCM.

ABSTRACTBackgroundLate gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) imaging is a well‐established indicator of myocardial fibrosis in hypertrophic cardiomyopathy (HCM). However, its association with electrocardiographic (ECG) abnormalities and the risk of atrial fibrillation (AF) remains uncertain.ObjectivesTo investigate the association between the presence and burden of LGE with ECG characteristics, including precordial voltage, depolarization and repolarization abnormalities, and the incidence of AF in adults with HCM.MethodsWe conducted a retrospective cohort study of 144 adults with HCM with CMR and 12‐lead ECG within 30 days of each other. LGE was quantified as a percentage of LV mass and categorized as absent, < 5%, or ≥ 5%. ECG parameters, including QRS voltage, repolarization abnormalities, and LVH criteria, were analyzed. Incident AF was assessed during a median follow‐up of 6.6 years.ResultsLGE was present in 96 (67%) patients, with 21 (22%) having ≥ 5% LGE. There were no significant differences in precordial voltage between patients with and without LGE across Sokolow‐Lyon, Cornell, and Romhilt‐Estes criteria. However, T‐wave inversion was more common in leads I (41% vs. 19%, p = 0.009), aVL (50% vs. 31%, p = 0.033), and V4 (41% vs. 23%, p = 0.035) in patients with LGE. Patients with ≥ 5% LGE had a significantly lower median LVEF (64% vs. 74%, p = 0.003). Additionally, LGE presence was not associated with an increased risk of incident AF (HR 1.8, 95% CI 0.6–5.3, p = 0.308).ConclusionIn contrast to pediatric HCM, LGE is associated with specific ECG repolarization abnormalities, particularly T‐wave inversion in lateral leads, but does not significantly affect precordial voltage in adults.

Abstract Introduction Obstructive sleep apnea (OSA) has been linked to metabolic syndrome, heart failure, atrial fibrillation, and hypertension. Although ethnic differences related to OSA have been reported, no studies have evaluated the impact of OSA among Greek-Americans. Methods This prospective cross-sectional study, in partnership with the Greek-American community, employed a community-based participatory research framework. Individuals who were of Greek descent and ≥18 years of age were recruited. Anthropometric measurements, Mallampati score, BMI, and adiposity (DEXA scan) were determined. All subjects were administered the Epworth Sleepiness Scale (ESS) and underwent home sleep apnea test (WatchPAT ONE), using a desaturation threshold of 4% as diagnostic. Descriptive statistics were computed to describe the study population and data were analyzed using the student t-test and chi-squared test. Results A 76 Greeks, 34 males (44.8%) and 42 females (55.2%), were enrolled in this study with a mean ± SD age and BMI of 42.6±17.5 years (p&lt; 0.01) and 27±6 kg/m2, respectively. A total of 22 (29%; 14 males and 8 females) individuals were diagnosed with OSA, of whom 13 (59.1%) had mild, 5 (22.7%) had moderate and 4 (18.2%) had severe OSA. Subjects with OSA were older (58.8±11.9 vs 36.0±15.1 years, p&lt; 0.01), had higher BMI (32±7 vs 25±4 kg/m2, p&lt; 0.01), larger neck circumference (40±4 vs 35±4 cm, p&lt; 0.01) and higher waist-to-hip ratio (0.94±0.08 vs 0.84±0.07, p&lt; 0.01). Body fat percentage was significantly higher among those with versus without OSA (38.8±9.6 vs 34.0±9.2%; p=0.04) while Mallampati and ESS scores were similar. Conclusion This is the first study to assess sleep metrics of Greek-Americans suffering from OSA. Characteristics of those with OSA are similar to other populations. However, the commonly used ESS screening appears to have limited application in this cohort of subjects. Greek-Americans with elevated body fat percentage when associated with concurrent OSA, may be at higher risk of developing cardiometabolic adverse events. Additional studies are required to further elucidate the effect of sleep physiology, cardiometabolic dysfunction and health outcomes. Support (if any) This work was supported by a grant from Sleep Number Corporation to Mayo Clinic, by WatchPATs provided by Zoll Itamar, and by the National Institutes of Health HL160619.

Background: Sleep disordered breathing (SDB) is frequently observed in patients with cardiovascular disease, and is associated with intermittent hypoxia, sympathetic activation, oxidative stress, and endothelial dysfunction, all of which may facilitate the development and progression of cardiovascular disease. Objectives: We sought to determine the prevalence, subtypes, and clinical implications of comorbid SDB in patients with hypertrophic cardiomyopathy (HCM). Methods: In this prospective observational study, patients with HCM without prior diagnosis of SDB were recruited to undergo inpatient polysomnography between May 1 st 2018 and October 31 st 2022. Electrocardiographic and echocardiographic parameters, cardiac biomarkers, and symptoms were comparatively assessed in patients with and without comorbid SDB. Patients were assessed for the development of major adverse cardiovascular events (MACE) during follow-up (median 29, range 3-57 months). Results Among 154 participants, 91 (59.1%) were diagnosed with SDB of whom 38 (41.8%) had mild, 22 (24.2%) moderate, 18 (19.8%) severe obstructive sleep apnea, and 13 (14.3%) had central sleep apnea. SDB was associated with greater left ventricular mass (median [IQR]) (128 [107, 161] vs. 109 [96, 134] g/m 2 , p =0.034) and E/e’ ratio (12.5 [10, 15] vs. 10.0 [8.3, 14.5], p =0.039). Patients with HCM over the age of 50 years, with body mass index ≥ 30kg/m 2 , who described their sleep as “poor” were at particularly high risk of having comorbid SDB, as were those who were diabetic, hypertensive, or described greater exertional limitation (NYHA Class ≥II 53% vs. 27%, p =0.005). Importantly, subjects with SDB had elevated baseline Troponin T levels (14 ng/L vs 11 ng/L, p =0.030), and further substantial overnight troponin increases following untreated apneic sleep (2.1ng/L vs 0.2ng/L, p =0.009). Finally, patients with comorbid SDB experienced a significantly higher proportion of incident adverse cardiovascular events (MACE hazard ratio 5.3, 95% CI, 1.6, 17.2, p =0.006) than those without SDB. Conclusions: We report a particularly high burden of previously undiagnosed SDB in patients with HCM, particularly in older, heavier, male patients. Undiagnosed SDB in HCM is not benign and is associated with symptom progression, comorbidity, and a poorer prognosis, particularly in the case of central sleep apnea. These important new findings provide rationale for heightened vigilance and routine screening for SDB in patients with HCM.