How your sleep affects your heart

How your sleep affects your heart
I recently asked a patient about his compliance with therapy for obstructive sleep apnea and got an odd response.
“What does it matter to you if I use my CPAP?”
A CPAP (continuous positive airway pressure) is a mask worn at night to improve oxygen levels during sleep.
I understand his question. This is a sleeping problem, after all—not exactly in the realm of cardiology.  Why should I care if he starts his day refreshed or drags out of bed feeling hung over?
Other patients have expressed confusion (albeit less bluntly) about the relationship between OSA and heart function. To explain the connection, let’s start with a few basics about sleep.
A night’s slumber is composed of several periods where the brain drifts between various levels of consciousness. The deepest and most restorative stage is REM, the period during which your brain is most active.  Since your dreams can become pretty vivid, your body compensates by disconnecting your brain from your muscles. That way when you dream about trying to fly you don’t end up smacking your spouse as you flap your wings.
The problem is that the muscles in your neck — normally in a constant state of mild contraction during breathing — relax and allow the weight of your chin to press down on your airway, essentially choking you.
A person with OSA will fight violently in their sleep against a closed airway while trying to get a breath in, sucking but pulling in no air. This can go on for up to a minute before he/she succumbs to the stress of suffocation and exits REM sleep, not rousing enough to remember the episode but with sufficient sleep disruption that he spends the next day exhausted.  This pattern can repeat itself dozens of times during the night.
Obese men are at highest risk, but I’ve seen OSA in all types.  In my opinion, if a patient or spouse suspects OSA then it’s highly likely to be present.  A sleep study will confirm the diagnosis, and treatment will include wearing a CPAP that forces air into the lungs so the airway doesn’t collapse.
So how does OSA affect the heart?
  1. Nighttime breath-holding episodes lead to low oxygen levels, triggering constriction in the blood vessels that pass through the lungs.
  2. Night after night of this constriction scars the small vessels.
  3. The pressure required to push blood through the lungs gradually rises, causing the heart’s right ventricle to enlarge and weaken. Without an effective right ventricle, fluid builds up in the abdomen and legs.
  4. Your doctor might treat swelling with diuretics (water pills), which cause the kidneys to eliminate water in the urine.  For the kidneys to get rid of fluid, the blood must be effectively circulated to the kidneys. This doesn’t happen because of the weak right ventricle. Thus, the kidneys begin to fail.
  5. The patient is left with swelling resistant to medication, kidneys heading for dialysis, and an overall feeling of exhaustion.
  6. OSA can also lead to high blood pressure that is often refractory to standard doses of medications.
  7. Persistent strain on the right chambers of the heart frequently leads to heart rhythm disturbances such as atrial fibrillation.
So while I’d rather spend my office time discussing problems I can fix with catheters and pacemakers, I find that I’m frequently talking about sleep habits. Early use of the mask can lessen nearly all the adverse cardiac effects as well as return the patient to restorative sleep (this works even better when coupled with weight loss).
The first step in geting someone to try the mask is explaining why they need it.
I wish I could report that my patient listened to my reasoning.  In reality, I’m sure I’ll see him in the future, but by then the damage might be permanent.

No comments:

Post a Comment