Sleep Apnea Syndrome and Large Artery Subclinical Damage: Targeting Thoracic Aortic Dilatation

AIM

Whether obstructive sleep apnea (OSA) actually represents an independent risk factor for aortic dilation in the general population is unclear. We investigated this issue through a review and a meta-analysis of cardiac imaging studies that provided data on this vascular phenotype measured at the root or ascending tract level.

DESIGN

A computerized search was performed using Pub-Med, OVID, EMBASE, and Cochrane library databases from inception up to 30 November 2021. Studies were identified by using the following search terms: "aortic root," "ascending aorta," "vascular damage," "echocardiography," "computed tomography," "magnetic resonance imaging," "obstructive sleep apnea," "sleep disordered breathing."

RESULTS

Eleven studies including a total of 1,860 patients with OSA (without aortic aneurysms and connective tissue diseases) and 233 non-OSA controls were considered. Aortic diameter was significantly higher in patients with OSA than in non-OSA controls (standard means difference [SMD] = 0.73 ± 0.08, confidence interval [CI]: 0.57-0.88, P < 0.0001). This was also the case for patients with severe OSA as compared with their counterparts with mild OSA (SMD = 0.42 ± 0.07, CI: 0.28-0.56, P < 0.0001).

CONCLUSIONS

Our findings suggest an association between OSA and aortic enlargement and particularly in the severe OSA setting. However, this conclusion must be taken with caution in relation to 2 types of factors: (i) the paucity of available data, and (ii) the limits deriving from the methodological differences of the various studies. Larger prospective and carefully designed studies are needed to shed light on this relevant public health topic.

QTc prolongation is associated with severe desaturations in stroke patients with sleep apnea

Background

Obstructive sleep apnea (OSA) is associated with vascular diseases from which stroke and sudden cardiac death are the most significant ones. It is known that disturbances of the autonomic nervous system and electrocardiographic changes are seen in patients with a previous cerebrovascular event. However, the pathophysiological cascade between breathing cessations, autonomic regulation, and cardiovascular events is not fully understood.

Methods

We aimed to investigate the acute effect of desaturation on repolarisation in OSA patients with a previous stroke. We retrospectively analysed heart-rate corrected QT (QTc) intervals before, within, and after 975 desaturations in OSA patients with a stroke history and at least moderate sleep apnea (apnea–hypopnea index ≥ 15 events/h, n = 18). For the control population (n = 18), QTc intervals related to 1070 desaturation were analysed. Desaturations were assigned to groups according to their length and duration. Groupwise comparisons and regression analyses were further executed to investigate the influence of desaturation features on repolarization.

Results

In the stroke population the QTc prolonged at least 11 ms during 27.1% of desaturations, and over 20 ms during 12.2% of desaturations. QTc was significantly prolonged during longer (> 30 s, p < 0.04) and deeper (> 7%, p < 0.03) desaturations. Less severe desaturations didn't influence QTc. In median, QTc prolonged 7.5 ms during > 45 s desaturations and 7.4 ms during > 9% deep desaturations. In the control population, QTc prolongation was observed but to a significantly lesser extent than in stroke patients. In addition, desaturation duration was found to be an independent predictor of QTc prolongation (β = 0.08, p < 0.001) among all study patients.

Conclusions

We demonstrated that longer (> 30 s) and deeper (> 7%) desaturations prolong QTc in patients with stroke history. A significant proportion of desaturations produced clinically relevant QTc prolongation. As it is known that a long QTc interval is associated with lethal arrhythmias, this finding might in part explain the pathophysiological sequelae of cardiovascular mortality in OSA patients with a history of stroke.

Aortic Root Diameter in Hypertensive Patients With Various Stages of Obstructive Sleep Apnea

BACKGROUND

Obstructive sleep apnea (OSA) is a risk factor of several cardiovascular diseases. We investigated the association between aortic root diameter and hypoxia-related parameters in hypertensive patients with OSA.

METHODS

Our study included 242 hypertensive patients with OSA (52 mild, 71 moderate, and 119 severe). All the patients underwent echocardiography for measuring aortic root diameter and polysomnography for measuring apnea–hypopnea index (AHI), oxygen desaturation index, and time spent with oxygen desaturation less than 90%.

RESULTS

The study patients included 19.8% women and had a mean (±SD) age of 49.9 ± 12.9 years, a mean aortic root diameter of 33.4 ± 2.6 mm, and a prevalence of echocardiographic aortic root dilation of 3.7%. Patients with mild, moderate, and severe OSA had similar echocardiographic left ventricular structure. However, patients with severe OSA had a significantly (P < 0.05) greater aortic root diameter (33.9 ± 2.4 mm vs. 32.4 ± 2.2 and 33.4 ± 2.9 mm, respectively) and higher prevalence of aortic root dilatation (5% vs. 1% and 3%, respectively) than those with mild and moderate OSA. Aortic root diameter corrected by body height was significantly (P < 0.001) associated with AHI, oxygen desaturation index and time spent with oxygen desaturation less than 90% (r = 0.23–0.33). After adjustment for various confounding factors, the associations between aortic root diameter and polysomnography parameters remained statistically significant (P < 0.05).

CONCLUSIONS

The severity of OSA was associated with the aortic root diameter. Patients with severe OSA had a greater aortic root diameter.

Potent hERG channel inhibition by sarizotan, an investigative treatment for Rett Syndrome

Rett Syndrome (RTT) is an X-linked neurodevelopmental disorder associated with respiratory abnormalities and, in up to ~40% of patients, with prolongation of the cardiac QT_c interval. QT_c prolongation calls for cautious use of drugs with a propensity to inhibit hERG channels. The STARS trial has been undertaken to investigate the efficacy of sarizotan, a 5-HT_1A receptor agonist, at correcting RTT respiratory abnormalities. The present study investigated whether sarizotan inhibits hERG potassium channels and prolongs ventricular repolarization. Whole-cell patch-clamp measurements were made at 37 °C from hERG-expressing HEK293 cells. Docking analysis was conducted using a recent cryo-EM structure of hERG. Sarizotan was a potent inhibitor of hERG current (I_hERG; IC₅₀ of 183 nM) and of native ventricular I_Kr from guinea-pig ventricular myocytes. 100 nM and 1 μM sarizotan prolonged ventricular action potential (AP) duration (APD₉₀) by 14.1 ± 3.3% (n = 6) and 29.8 ± 3.1% (n = 5) respectively and promoted AP triangulation. High affinity I_hERG inhibition by sarizotan was contingent upon channel gating and intact inactivation. Mutagenesis experiments and docking analysis implicated F557, S624 and Y652 residues in sarizotan binding, with weaker contribution from F656. In conclusion, sarizotan inhibits I_Kr/I_hERG, accessing key binding residues on channel gating. This action and consequent ventricular AP prolongation occur at concentrations relevant to those proposed to treat breathing dysrhythmia in RTT. Sarizotan should only be used in RTT patients with careful evaluation of risk factors for QT_c prolongation.

P-wave dispersion: an update

P-wave dispersion (PWD, Pd or Pdis) is a noninvasive electrocardiographic (ECG) marker for atrial remodeling and predictor for atrial fibrillation (AF). PWD is defined as the difference between the widest and the narrowest P-wave duration recorded from the 12 ECG leads. Increased P-wave duration and PWD reflect prolongation of intraatrial and interatrial conduction time with lack of a well-coordinated conduction system within the atrial muscles, with inhomogeneous, asynchronic, pro-inflammatory and anti-inflammatory effect mediated by interleukin-6 (IL-6) in patients with the CG + GG genotype IL-6 -634C/G polymorphism [1] and discontinuous propagation of sinus impulses mainly between the left and right atria, interstitial/extracellular fibroblast activation and collagen deposition with fibrosis (via TGF-β) in atrial tissue, insufficient blood supply, significant not isotropic myoelectric activity, and thin wall thickness and consequent expansion tendency all well-known electrophysiological characteristics in patients with atrial arrhythmias and especially paroxysmal atrial fibrillation (PAF) [2].