Posted on November 16, 2005 at 11:45 a.m.
DALLAS, TX — Full-night sleep studies and echocardiography may need to be incorporated into routine assessments of patients with difficult-to-treat high blood pressure, suggested UAB (University of Alabama at Birmingham) researcher Monique Pratt-Ubunama, M.D., during a presentation yesterday (Tuesday, November 15) at the annual meeting of the American Heart Association.
“And, those who are resistant to treatment and found to have sleep apnea may potentially benefit from mineralocorticoid receptor antagonists, since levels of aldosterone were high in study patients, and continuous positive airway pressure (CPAP) should be encouraged,” she said.
Ubunama’s suggestions are based on results from the study, “Severity of Sleep Apnea Correlates With Endothelial Dysfunction and Left Ventricular Mass in Patients With Resistant Hypertension” [Abstract 2596], funded by the National Heart, Lung and Blood Institute.
“We were trying to figure out the link between sleep apnea, endothelial dysfunction and left ventricular remodeling in patients with resistant high blood pressure,” Ubunama said. “We found a direct relationship between the severity of sleep apnea and cardiovascular changes associated with high blood pressure.”
Ubunama and colleagues with the UAB Hypertension Program found that the severity of sleep apnea is directly related to endothelial changes, measured using an index of blood flow through the brachial artery, and left ventricular remodeling — or thickening of the heart muscle walls in the left ventricle — ascertained by measuring ventricle dimensions using echocardiography. Both endothelial dysfunction and left ventricular remodeling are changes researchers found to be associated with sleep apnea severity in resistant hypertension patients.
The findings are consistent with previous studies that have shown a correlation between untreated sleep apnea and cardiovascular disease. “However,” Ubunama said, “we did not expect to find endothelial impairment to this degree, and our findings of elevated urinary aldosterone levels and high sleep apnea prevalence in these treatment-resistant hypertension patients also were surprising.”
Ubunama said in treatment-resistant hypertension patients, the relationship between sleep apnea and heart disease appears to be related to increased levels of the hormone aldosterone, which may become elevated during hypoxic (lack of oxygen) episodes that occur in sleep apnea. Patients with sleep apnea experience episodes during sleep when they momentarily stop breathing, which lowers the oxygen-saturation levels in the blood. “Consequently, the decreased oxygen appears to stimulate aldosterone release, which, in turn, influences endothelial dysfunction, or damage of the lining of the blood vessels, and contributes to the mechanisms of ventricular remodeling, or thickening of the heart muscle walls.”
Previous studies have shown that treating sleep apnea patients with CPAP, a device that provides sufficient pressure to keep the airway open and improve oxygenation during sleep, improves endothelial dysfunction. “CPAP should also improve blood pressure and the progression of LV remodeling. Based on this data, doctors should be encouraged to screen for and treat sleep apnea in patients with hypertension.”
Sleep apnea is very under-diagnosed, according to Ubunama, particularly among patients with high blood pressure, and doctors rarely ask about their patients’ sleep habits. However, in UAB hypertension clinics, researchers have found the prevalence of sleep apnea in the population of resistant hypertension patients, specifically those who continue to experience uncontrolled high blood pressure on three or more medications, is approximately 85 percent.
“These findings could potentially prompt doctors to unmask a significant amount of undiagnosed sleep apnea in patients with treatment-resistant high blood pressure, even among those who don’t experience symptoms associated with sleep apnea.”