Heart disease is a very broad health term, which can sometimes create some confusion. But for this dicussion, we’ll highlight the ways sleep apnea is connected to heart disease, as it can cause complications for the artieries, heartbeat, and even trigger heart attacks.
Typically, arteries become blocked when cholesterol, fat, and fibrin come togther to form plaque fragments. Since this is just a fixed blockage, additional inflammatory mediators may sometimes form more significant plaques by attracting other particles. This results in a complete blockage of the artery, and ultimately a heart attack. But a person who is suffering from obstructive sleep apnea and cannot adequately move air into their lungs, may also suffer from lower oxygen levels in the blood. Similarly, when this person breathes in, it too can cause an inflammatory response that causes a clot, resulting in a complete blockage and later causing a heart attack.
It has been shown that sleep apnea may independently put someone at risk for dangerous plaque formation in the arteries. In obstructive sleep apnea, there is another concern about the lack of breathing that decreases the amount of oxygen traveling to blood cells. When this drop happens repeatedly, as it usually does in those with apnea, it results in re-oxygenation. This is the body’s way of rushing oxygen back to cells, but it may form radicals, as well as inflammatory particles that cause harmful clots to the heart.
When we sleep, it’s natural for our breathing volume and heart rate to go down. This helps our body preserve energy and shift all the work to the most active organ of sleep, the brain. And when the heart contracts to pump blood during sleep, it doesn’t have to overcome much resistance, since our blood pressure naturally lowers as well.
If a person has sleep apnea, the muscle that pulls air into the lungs has to work harder to overcome the resistance, due to the blocked airway. This creates negative pressure that takes its toll on the heart. Imagine an athlete trying to run forward while there is a rubber belt around his waist and attached to the wall pulling him back. Sleep apnea creates a similar negative pressure force and resistance on the heart.
This increased pressure on the walls of the heart during obstructive apnea eventually causes the wall to struggle to contract and form a regular heartbeat. The pacemaker of the heart, known as the sinus, will fail to set a regular rhythm, causing causes an irregular rhythm in the heart known as Atrial Fibrillation.
Sleep apnea and the pumping action of the heart
If the previous two conditions become combined (increased negative pressure in the chest with higher blood pressure of the arteries), the heart becomes deficient in pumping blood forward. This results in a back-up of fluid in the lungs, and ultimately, congestive heart failure.
This is most likely to happen in those already suffering from heart disease. What is most scary is that often they sleep through these events and won’t notice. In this case, doctors may also go on not knowing and won’t order a study unless he or she directly suspects a problem.
What are the consequences of these events? If you have sleep apnea, or have experienced any of these events, be aware of heart attack risk. Statistics show that the most common hours for a sudden death cardiac event are between 6 am and 12 noon. If you have sleep apnea, most of your episodes occur between midnight and 6 am.
The good news is that these serious events are preventable and can be avoided with the treatment that involves use of a CPAP machine. How do we know this? Valuable data was obtained from a large multicenter study called The Sleep Heart Health Study. Stay tuned for my next sharepost on that topic.
Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music. Find him on Twitter @Lung_doctor.