Differing Effects of Obstructive and Central Sleep Apneas on Stroke Volume in Patients With Heart Failure
Is there a difference in stroke volume (SV) among systolic heart failure patients who experience obstructive (OSA) versus central (CSA) apnea events?
The validity of noninvasive measurement of stroke volume by digital photoplethysmography (DPP), was first measured by DPP and echocardiographic SV during various maneuvers in five healthy subjects: average age was 28 years and body mass index (BMI) was 24.6 kg/m2. Both men and women with ischemic and nonischemic cardiomyopathy were included, with an ejection fraction (EF) of 45% or less. Patients were excluded if they had heart failure class IV, treated sleep apnea, a prior ischemic event within the previous 3 months, paced rhythm, or atrial fibrillation. All subjects underwent overnight polysomnography. Subjects slept in the supine position to maintain constant position of the DPP, which measured SV continuously. Change in SV from before to the end of obstructive and central respiratory events was calculated and compared between these types of events.
A total of 40 patients were studied, 30 had predominantly OSA (i.e., >50% obstructive events), of whom 80% were men. Mean age was 56.5 (±10.3) years, BMI was 29.8 (±6.5) kg/m2, and EF was 33.4 (±9.2)%. Changes in SV were assessed during 252 obstructive and 148 central respiratory events. Whereas SV decreased by 6.8 (±8.7)% during obstructive events, it increased by 2.6 (65.4)% during central events (p < 0.001). For obstructive events, reduction in SV was associated independently with left ventricular EF, duration of respiratory events, and degree of oxygen desaturation.
In heart failure with reduced EF, obstructive and central respiratory events have opposite hemodynamic effects: Whereas OSA appears to have an adverse effect on SV, CSA appears to have little or slightly positive effects on SV measured by DPP.
These findings suggest greater potential for improvement in cardiovascular function, through treatment of OSA than of CSA in patients with heart failure. However, to date, there have been no long-term randomized trials evaluating whether treating OSA by positive airway pressure in patients with heart failure will improve morbidity and mortality.
Keywords: Photoplethysmography, Heart Failure, Stroke Volume, Sleep Apnea Syndromes, Echocardiography
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