Patients with obstructive sleep apnea have enlarged and thickened hearts that pump less effectively, but the heart abnormalities improve with use of a device that helps patients breathe better during sleep, according to a new study in the April 4, 2006, issue of the Journal of the American College of Cardiology.
"Not only are the shape and size of the heart affected, the right side of the heart was dilated and the heart muscle on the left side was thicker in patients with obstructive sleep apnea, but the pump function was also reduced. The changes were directly related to the severity of the problem. Treating the problem brought significant improvements in the affected parameters, as well as in symptoms, in a relatively short period of time of six months," said Bharati Shivalkar, M.D., Ph.D. from the University Hospital Antwerp in Antwerp, Belgium.
Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder associated with increased risk of cardiovascular disease. The OSA syndrome is characterized by repeated partial or complete closure of the pharynx, gasping episodes, sleep fragmentation, and daytime sleepiness. Previous studies have shown that sleep apnea is associated with high blood pressure and other cardiovascular risks, including stroke, ischemia, arrhythmias, or sudden death.
This study included 43 patients (32 men and 11 women) with obstructive sleep apnea. Sleep lab studies measured the severity and frequency of complete or partial interruptions of airflow. The shape and pumping action of the participants' hearts was measured using ultrasound. The researchers also examined 40 similar control subjects who were healthy and did not report any symptoms that would indicate sleep apnea.
Compared to the control subjects, the hearts of the sleep apnea patients were significantly enlarged on the right side and had thickened walls between the pumping chambers. The hearts of sleep apnea patients also pumped less blood per beat, and the velocity of wall motion was slower for both the left and right compared to the control subjects. The sleep apnea patients also had higher blood pressure and faster heart rates than the control subjects. The severity of the heart abnormalities was correlated with the severity of obstructive sleep apnea.
The sleep apnea patients were then given continuous positive airway pressure (CPAP) devices to treat their breathing problems. An air pump that is connected by a tube to a face mask helps keep the patient's airways open during the night. CPAP is a common sleep apnea treatment that often helps patients sleep better and then remain alert during the day.
In this study, the 25 sleep apnea patients who were evaluated after six months of CPAP treatment were not only sleeping better, and were more alert during the day, but there were significant improvements in the size, shape and pumping action of their hearts.
"From a cardiovascular standpoint, OSA still remains an important under-diagnosed and under-treated problem. Our study highlights that the changes in the shape and function of the heart can be assessed quite easily in a non-invasive manner and can alert the physician of impending cardiac problems. Most importantly, treatment can cause substantial improvement in a relatively short time. We hope that this paper will contribute towards improved awareness of cardiovascular and general physicians of a fairly common problem in the western society," Dr. Shivalkar said.
She said clinicians should also address issues such as alcohol and sedative use, which can affect sleep, as well as weight loss. However, she noted that not all sleep apnea patients are obese.
In her own clinical experience, Dr. Shivalkar said she has seen several patients who had high blood pressure that was not adequately controlled with medication. In many cases, she discovered these patients had obstructive sleep apnea.
"After treatment with CPAP, the antihypertensive medications could usually be substantially reduced. I am sure there are a lot of my cardiovascular colleagues out there who are often faced with such scenarios of difficult to treat hypertension. There should be a multidisciplinary approach to this problem, with a close association with cardiovascular physicians and sleep doctors in diagnosing and treating this problem," she said.
Eighteen of the 43 sleep apnea patients in this study did not complete the six months of CPAP treatment. Dr. Shivalkar said that although CPAP is a simple and noninvasive solution, a number of patients do not tolerate having the face mask on during the entire sleeping period at night. Some sleep apnea patients are treated with surgery, but Dr. Shivalkar said there is no long term data available on the effects of surgical treatment for these patients.
Ian Wilcox, M.B., Ph.D. from the Royal Prince Alfred Hospital Medical Centre in Newtown, Australia, who was not connected with this study, said earlier studies had produced some mixed data, and now these results move the field forward.
"This study brings it all together, particularly the treatment arm. In earlier treatment studies, patients didn't use CPAP the whole night. Here they used it almost seven hours a night, and showed quite nicely reduced septum thickness, along with improved performance and stroke volume," Prof. Wilcox said.
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