The Relationship between Nocturnal Hypoxemia and Left Ventricular Ejection Fraction in Congestive Heart Failure Patients

Left Ventricular Non-compaction Cardiomyopathy: Delayed Diagnosis and Deleterious Outcomes

Cardiomyopathy and associated heart failure have uncommon etiologies, which when diagnosed reduce patients’ morbidity and mortality. One such entity is left ventricular non-compaction cardiomyopathy (LVNC). Still, a relatively uncommon entity, the manifestation of LVNC may range from asymptomatic to left ventricular dysfunction, congestive heart failure, ventricular tachycardia, sudden cardiac death, and thromboembolic complications. If not pursued as a possible etiology of non-ischemic cardiomyopathy, patients may have significantly increased morbidity prior to eventual diagnosis. Patients are often predisposed to ventricular arrhythmias requiring implantable cardiac defibrillator placement. Additionally, due to the depth of trabeculations, there is an associated thromboembolic risk requiring therapeutic anticoagulation. We present the case of a 41-year-old man with progressively worsening heart failure due to undiagnosed LVNC and the associated deleterious manifestations and outcomes.

ST2 silencing aggravates ventricular remodeling and chronic heart failure in rats by mediating the IL-33/ST2 axis

Heart failure appears to be a severe public health problem affecting millions of people worldwide. Knowledge of the molecular mechanism contributing to ventricular remodeling would allow for earlier prevention of heart failure. Evidence exists reporting the involvement of IL-33 and ST2 and in heart remodeling. Thus, this study aims to delineate the effects of ST2 on chronic heart failure (CHF) via the IL-33/ST2 axis. Coronary artery ligation was employed to simulate CHF in rats, which were characterized by transthoracic echocardiography for cardiac function. After that, ST2 silencing and IL-33 overexpression were induced in rat models to evaluate apoptosis and pathological alterations in myocardial tissues and serum levels of biochemical indices. It was revealed that cardiac function was impaired in response to ST2 silencing. Furthermore, ST2 knockdown suppressed the activities of the mitochondrial respiratory chain and accelerated cardiomyocyte apoptosis via blockade of the IL-33/ST2 axis. These findings suggest an inhibitory role of ST2 silencing on the IL-33/ST2 axis, which consequently increases the risk of cardiac dysfunction, accelerates ventricular remodeling, and aggravates heart failure in rats. This study highlights that ST2 silencing may be a novel potential preventive or therapeutic target for CHF.

Skeletal Muscle Fiber Type in Hypoxia: Adaptation to High-Altitude Exposure and Under Conditions of Pathological Hypoxia

Skeletal muscle is able to modify its size, and its metabolic/contractile properties in response to a variety of stimuli, such as mechanical stress, neuronal activity, metabolic and hormonal influences, and environmental factors. A reduced oxygen availability, called hypoxia, has been proposed to induce metabolic adaptations and loss of mass in skeletal muscle. In addition, several evidences indicate that muscle fiber-type composition could be affected by hypoxia. The main purpose of this review is to explore the adaptation of skeletal muscle fiber-type composition to exposure to high altitude (ambient hypoxia) and under conditions of pathological hypoxia, including chronic obstructive pulmonary disease (COPD), chronic heart failure (CHF) and obstructive sleep apnea syndrome (OSAS). The muscle fiber-type composition of both adult animals and humans is not markedly altered during chronic exposure to high altitude. However, the fast-to-slow fiber-type transition observed in hind limb muscles during post-natal development is impaired in growing rats exposed to severe altitude. A slow-to-fast transition in fiber type is commonly found in lower limb muscles from patients with COPD and CHF, whereas a transition toward a slower fiber-type profile is often found in the diaphragm muscle in these two pathologies. A slow-to-fast transformation in fiber type is generally observed in the upper airway muscles in rodent models of OSAS. The factors potentially responsible for the adaptation of fiber type under these hypoxic conditions are also discussed in this review. The impaired locomotor activity most likely explains the changes in fiber type composition in growing rats exposed to severe altitude. Furthermore, chronic inactivity and muscle deconditioning could result in the slow-to-fast fiber-type conversion in lower limb muscles during COPD and CHF, while the factors responsible for the adaptation of muscle fiber type during OSAS remain hypothetical. Finally, the role played by cellular hypoxia, hypoxia-inducible factor-1 alpha (HIF-1α), and other molecular regulators in the adaptation of muscle fiber-type composition is described in response to high altitude exposure and conditions of pathological hypoxia.

Heart failure and sleep-disordered breathing

PURPOSE OF REVIEW

Sleep-disordered breathing, which includes both obstructive and central sleep apnoea (OSA and CSA, respectively), is highly prevalent in patients with heart failure. In this review, we outline our current understanding of the bidirectional relationship between these disorders and heart failure. We also explore the role of recent advances in therapeutics.

RECENT FINDINGS

Although early studies suggest promise of adaptive servoventilation in treating sleep-disordered breathing, particularly CSA with associated Cheyne-Stokes respiration, the recent clinical trial in the heart failure patient population has demonstrated worse cardiovascular outcome in symptomatic patients.

SUMMARY

Both OSA and CSA are highly prevalent in patients with heart failure. Effective treatment of OSA with continuous positive airway pressure can improve cardiovascular outcome in these patients. However, recent evidence suggests that adaptive servoventilation cannot be safely recommended as a therapy for CSA in the context of heart failure, as a result of increased risk of cardiovascular mortality.