This week I had the opportunity to meet with Dr. Mervyn Forman, a distinguished Cardiologist and innovator in metro Atlanta. Dr. Forman’s medical practice covers the spectrum of cardiovascular disease prevention and long-term management, while his research has focused on reducing heart muscle damage after a heart attack. He is currently developing a drug coated guidewire for use during stent insertion.
Dr. Forman sees a number of patients on a daily basis with obstructive sleep apnea that may be complicating their cardiac disease. I sought Dr. Forman’s perspective on sleep apnea, as he in fact has daily hands-on experience treating the cardiovascular end-effects in his patients. Our Q&A session is below, revised into a more printer-friendly format. Dr. Forman can be reached at his medical practice in the Atlanta area on Northside Hospital campus: 960 Johnson Ferry Rd NE, Suite 530, (404)446-1900. He also consults in East Cobb county.
WHAT ARE THE CARDIOVASCULAR COMPLICATIONS OF OBSTRUCTIVE SLEEP APNEA?
Obstructive sleep apnea (OSA) is a common chronic disorder with a major effect on morbidity and mortality. Sleep encompasses about one third of one’s life and induces physiological changes in the human body to rest the cardiovascular, respiratory, and metabolic systems. OSA is now recognized as an important risk factor for cardiovascular disease. Hypertension, coronary artery disease, heart failure, heart rhythm (fast and slow) abnormalities, cerebrovascular disease, and diabetes have all been shown to be linked to sleep disorders. OSA is therefore one of the most prevalent and dangerous cardiac risk factors we know of.
WHAT ARE THE CHANGES THAT OCCUR WITH OSA THAT AFFECT THE CARDIOVASCULAR SYSTEM?
Repetitive closure of the upper airway during sleep results in a number of hemodynamic and biochemical derangements which effect the cardiovascular systems.
1.) Exaggerated swings in the pressure in the chest which impairs filling on the left ventricle (pumping chamber) results in decreased blood pumped to the organs of the body.
2.) Activation of the portions of the nervous system that affect heart rate and blood pressure (arterial and in the lung circulation).
3.) Activation of tissue chemical factors which result in the formation of numerous inflammatory mediators and oxygen free radicals which promote damage to blood vessels, activate the blood clotting system and promote cholesterol (plaque) deposits in the blood vessel walls.
CAN UNTREATED OSA AFFECT MY BLOOD PRESSURE (BP) AND WILL TREATMENT IMPROVE THE CONTROL AND REDUCE THE NUMBER OF BP MEDICATIONS?
There is strong evidence that OSA is an important factor in hypertension (high blood pressure). This occurs in both sexes, all age groups, all ethnic groups and in obese and non-obese people. OSA increases both systolic (top) and diastolic (lower number) pressure. OSA also results in the loss of normal decrease in blood pressure that occurs at night. It is estimated that 50% of OSA patients have hypertension and OSA often plays a role in patients whose BP is refractory to BP medications. Treatment with continuous positive airway pressure (CPAP, a therapy for OSA) results in significant decreases in day and nighttime BP, improves control of refractory hypertension and reduces the number of medications required to achieve a normal BP.
CAN OSA CONTRIBUTE TO CORONARY ARTERY DISEASE (CAD) AND INDUCE A HEART ATTACK?
There is a strong correlation between OSA and the development of CAD and acute coronary syndromes (heart attack). 65% of patients admitted to the hospital with a heart attack were found to have OSA. Patients who suffer a heart attack in the early hours of morning (midnight to 6 am) are more likely to have OSA (32%) verses those without OSA (7%). This is due to OSA producing stress on the heart secondary to the increase heart rate and BP and by increasing the propensity of the blood to form clots. The co-existence of CAD and OSA worsens the prognosis resulting in 70% increase in death, stroke and heart attack. Patients with OSA undergoing stent insertions also have a higher risk of death (38%), stent narrowing (70%), and heart attack and stroke (12%). Nocturnal angina (chest pain) is associated with OSA and CPAP diminishes the frequency of chest pain attacks. There is also evidence that treatment of OSA may prevent heart attacks and delay progression of plaque buildup in the heart blood vessels.
CAN OSA PRODUCE AND EXACERBATE HEART FAILURE?
OSA affects almost half of heart failure patients. While the relationship is complex, OSA essentially induces the risk factors that lead to the development or exacerbation of heart failure (hypertension, CAD, diabetes, pulmonary hypertension). Furthermore heart failure can cause and worsen obstructive and central sleep apnea initiating a potentially devastating cycle. Treatment with CPAP has been shown to significantly improve pump function (ejection fraction), reduce heart size and BP, and improve quality of life.
CAN OSA LEAD TO HEART RHYTHM ABNORMALITUES AND CAUSE SUDDEN CARDIAC DEATH?
OSA results in low blood oxygen, abnormalities of autonomic nervous system and changes in the structure of heart muscle which predispose to heart rhythm abnormalities. OSA is strongly associated with the common heart rhythm abnormality, atrial fibrillation, occurring in 40-70% of patients. Atrial fibrillation (AF) is an important cause of stroke and heart failure. OSA is responsible for 25% greater risk of AF recurrence following catheter ablation procedure. OSA is also linked to other cardiac rhythm abnormalities including a slow heart rate, heart block, fast heart rhythm abnormalities and malignant ventricular arrhythmias. People with OSA have a dramatically increased risk of sudden cardiac death during sleep. Treatment with CPAP decreases nocturnal rates of slow heart rate and cessation of electrical pacemaker activity, atrial fibrillation, and dangerous fast heart rhythm abnormalities.
WHY IS WEIGHT LOSS IMPORTANT TO REDUCE THE CARDIOVASCULAR COMPLICATIONS OF OSA?
Obesity is the single most important risk factor in the development of OSA. A 10% increase in weight gain is associated with a 6-fold increase in the odds of developing OSA. Obesity and OSA often coexist with more than 40% of obese patients having significant OSA and 70% of OSA patients being obese. The link between obesity and cardiovascular disease has been well established. Obesity induces numerous and similar mechanisms to OSA that can lead to cardiovascular disease including hypertension, heart failure, coronary artery disease, atrial fibrillation, diabetes, and sudden cardiac death. Therefore the pressure of OSA in obese patients would be expected to place them at higher risk for cardiovascular events than obese patients without OSA. Aggressive weight reduction programs in addition to treatment of OSA with CPAP is essential to reduce cardiovascular complications of OSA.
I want to thank Dr. Forman for his kind and thorough collaboration on this post, and I encourage you to visit Dr. Forman for further assessment of your cardiovascular disease risk.