ASV Effects on Myocardial Energetics and Sympathetic Nerve Function in Heart Failure and Sleep Apnea.

Obstructive sleep apnea (OSA), central sleep apnea (CSA) and heart failure (HF) are states of metabolic demand and sympathetic nervous system (SNS) activation. In patients with sleep apnea and HF, continuous positive airway pressure (CPAP) initially may reduce left ventricular (LV)stroke volume (SV) but subsequently improves and LV function. This may relate to an early beneficial effect on myocardial energetics through early reduction in metabolic demand that subsequently leads to improved efficiency of LV contraction. However, it is not clear whether long-term adaptive servo-ventilation (ASV) favorably affects cardiac energetics. Any such benefit may also relate to reduced sympathetic nervous system (SNS) activation. However its effect on myocardial SNS function is also not well studied. In a pilot study we demonstrated early (6 week) beneficial effects of CPAP in patients with OSA and HF. The current proposal (AMEND) is a unique substudy of the recently funded ADVENT-HF trial (Adaptive Servo Ventilation for Therapy of Sleep Apnea in HeartFailure) (NCT01128816; CIHR; D. Bradley, PI). We propose to evaluate the long-term (6 month) effects of ASV on daytime 1) oxidative metabolism; 2) the work metabolic index (WMI) as an estimate of mechanical efficiency; 3) myocardial sympathetic nerve (SN) pre-synaptic function; and 4) heart rate (HR) variability in patients with HF and coexisting OSA or CSA. In conjunction with echocardiographic measures of LV stroke work, positron emission tomography (PET) derived \[11C\] acetate kinetics will be used as a measure of oxidative metabolism, to determine the WMI. \[11C\] hydroxyephedrine (HED) retention will be used to measure cardiac SN pre-synaptic function. Primary Hypotheses: In patients with chronic stable HF and CSA or OSA without excessive daytime sleepiness (EDS), long-term (6-month) ASV therapy yields: 1. Beneficial effects on daytime myocardial metabolism leading to a reduction in the rate of oxidative metabolism as me