Nighttime Blood Pressure: A Target for Therapy?

Hypothalamic Oxytocin Neuron Activation Attenuates Intermittent Hypoxia-Induced Hypertension and Cardiac Dysfunction in an Animal Model of Sleep Apnea

BACKGROUND

Obstructive sleep apnea is a prevalent and poorly treated cardiovascular disease that leads to hypertension and autonomic imbalance. Recent studies that restore cardiac parasympathetic tone using selective activation of hypothalamic oxytocin neurons have shown beneficial cardiovascular outcomes in animal models of cardiovascular disease. This study aimed to determine if chemogenetic activation of hypothalamic oxytocin neurons in animals with existing obstructive sleep apnea-induced hypertension would reverse or blunt the progression of autonomic and cardiovascular dysfunction.

METHODS

Two groups of rats were exposed to chronic intermittent hypoxia (CIH), a model of obstructive sleep apnea, for 4 weeks to induce hypertension. During an additional 4 weeks of exposure to CIH, 1 group was treated with selective activation of hypothalamic oxytocin neurons while the other group was untreated.

RESULTS

Hypertensive animals exposed to CIH and treated with daily hypothalamic oxytocin neuron activation had lower blood pressure, faster heart rate recovery times after exercise, and improved indices of cardiac function compared with untreated hypertensive animals. Microarray analysis suggested that, compared with treated animals, untreated animals had gene expression profiles associated with cellular stress response activation, hypoxia-inducible factor stabilization, and myocardial extracellular matrix remodeling and fibrosis.

CONCLUSIONS

In animals already presenting with CIH-induced hypertension, chronic activation of hypothalamic oxytocin neurons blunted the progression of hypertension and conferred cardioprotection after an additional 4 weeks of CIH exposure. These results have significant clinical translation for the treatment of cardiovascular disease in patients with obstructive sleep apnea.

Speckle tracking echocardiography in heart failure development and progression in patients with apneas

Obstructive (OA) and central apneas (CA) are highly prevalent breathing disorders that have a negative impact on cardiac structure and function; while OA promote the development of progressive cardiac alterations that can eventually lead to heart failure (HF), CA are more prevalent once HF ensues. Therefore, the early identification of the deleterious effects of apneas on cardiac function, and the possibility to detect an initial cardiac dysfunction in patients with apneas become relevant. Speckle tracking echocardiography (STE) imaging has become increasingly recognized as a method for the early detection of diastolic and systolic dysfunction, by the evaluation of left atrial and left and right ventricular global longitudinal strain, respectively. A growing body of evidence is available on the alterations of STE in OA, while very little is known with regard to CA. In this review, we discuss the current knowledge and gap of evidence concerning apnea-related STE alterations in the development and progression of HF.

The Role of Nocturnal Blood Pressure and Sleep Quality in Hypertension Management

The accurate measurement, prediction and treatment of high blood pressure (BP) are essential to the management of hypertension and the prevention of its associated cardiovascular (CV) risks. However, even if BP is optimally controlled during the day, nocturnal high blood pressure may still increase the risk of CV events. The pattern of circadian rhythm of BP can be evaluated by ambulatory BP monitoring (ABPM). Night-time ABPM is more closely associated with fatal and nonfatal CV events than daytime ambulatory BP. However, the use of ABPM is limited by low availability and the fact that it can cause sleep disturbance, therefore may not provide realistic nocturnal measurements. Home blood pressure monitoring (HBPM) offers an inexpensive alternative to ABPM, is preferred by patients and provides a more realistic assessment of BP during an individual’s daily life. However, until recently, HBPM did not offer the possibility to measure nocturnal (sleep time) BP. The development and validation of new BP devices, such as the NightView (OMRON Healthcare, HEM9601T-E3) HBPM device, could overcome these limitations, offering the possibility of daytime and night-time BP measurements with minimal sleep disturbance.

The dilemma of nocturnal blood pressure

During the past decades, blood pressure (BP) measurement technique has evolved rapidly from the traditionally manual measuring to fully automatic monitoring. In terms of management of BP, there have been tremendous changes from the controlling of daytime BP, nondipping pattern to nocturnal BP (NBP). Since the focus has turned to NBP, a number of dilemmas of NBP measurement have gradually emerged in clinical practice and research settings, including methods for monitoring NBP, different period definition of nocturnal time, different diagnostic thresholds of abnormal NBP, whether to control abnormal NBP, and how to manage abnormal NBP. Currently, these issues have hindered progress in the appropriate management of hypertensive patients. Therefore, the purpose of this review is to concisely discuss the dilemmas of NBP.