Sleep-induced hypotension precipitates severe myocardial ischemia.
OBJECTIVE
Epidemiologic studies have shown a high frequency of major cardiac events at night in patients with coronary artery disease. This has been attributed to the sympathetic surges accompanying rapid eye movement (REM) sleep; the role of non-REM sleep, which comprises 80% of total sleep duration, has been largely neglected. Accordingly, we evaluated the effect of non-REM sleep on contractile function in a region of the left ventricular wall supplied by a flow-limiting coronary stenosis.


METHODS
Eight domestic pigs were chronically instrumented to measure regional left ventricular contractile function (wall thickening), coronary blood flow, and systemic hemodynamic variables. Measurements were obtained: (1) during wakefulness, i.e., conscious condition, prior to imposition of coronary stenosis; (2) during wakefulness following imposition of coronary stenosis (30% reduction of baseline coronary blood flow from 40 +/- 4 to 27 +/- 3 mL/min); and (3) during non-REM sleep with coronary stenosis maintained.


RESULTS
During wakefulness, coronary stenosis reduced wall thickening (from 23.3 +/- 3.4% to 15.7 +/- 2.0%), whereas mean arterial pressure and heart rate were unchanged. With coronary stenosis maintained, the onset of non-REM sleep caused 20% decreases in mean arterial pressure and coronary blood flow, accompanied by a cessation of regional wall thickening, i.e., akinesis (wall thickening = 0.2 +/- 2.8%), indicating severe myocardial ischemia.


CONCLUSIONS
The arterial hypotension, and associated reduction in coronary blood flow, during non-REM sleep precipitated severe myocardial ischemia in a region of the left ventricular wall supplied by flow-limiting coronary stenosis. Such episodes would occur repeatedly during the sleep cycle and could potentially set the stage for a major cardiac event during the sympathetic activation accompanying REM sleep or morning activities.
Kim
Song-Jung
SJ
Section of Cardiology, Advocate Illinois Masonic Medical Center Chicago, IL 60657, USA. kimso@uic.edu
Kuklov
Alex
A
Kehoe
Richard F
RF
Crystal
George J
GJ
D000818:Animals; D003326:Coronary Circulation / Q000502:physiology; D023921:Coronary Stenosis / Q000503:physiopathology; D005260:Female; D007022:Hypotension / Q000503:physiopathology*; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology*; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology*; D013552:Swine; D013564:Sympathetic Nervous System / Q000503:physiopathology; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*; D016277:Ventricular Function, Left / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
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