And the beat goes on, sort of

Tuesday, February 17, 2009

Mike Hampton was ready for he Houston Astro’s training camp but it seems that this heart needed an extra couple of days to prepare. A routine physical exam found Hampton’s heart beating irregularly in a rhythm called atrial fibrillation or A Fib. Fortunately for him, his heart’s electricity decided returned to normal and for now, Hampton’s baseball career is back on track. Still, atrial fibrillation is a heart rhythm that causes stealth problems. It’s safe, in that the heart won’t stop beating, but there are complications.

The heart is a two stage electrical pump. The upper chambers of the heart, or the atria, collect blood from the body and pump it to the lower chambers. The ventricles then pump back to the body. The pumping action is coordinated by the heart’s electrical system. Normally, the heart’s pacemaker generates an electrical impulse that causes the atrium to contract. There is then a slight delay in the electrical conduction to allow blood to fill the ventricle. The electrical impulse continues down to ventricles causing them to contract. It’s the lub-dub beat of the heart.

In atrial fibrillation, there are many cells that begin generating electrical impulses in the atrium and a coordinated beat cannot be generated. Instead the atrium just sits there and jiggles. The ventricle responds to some of the impulses and beats irregularly and may be fast, slow or normal, so that people may not be able to feel any problem. The issue isn’t with the heart beat; instead it’s with the jiggling that allows blood to hang out in the atrium and potentially clot.

Blood clots in the atrium run the risk of breaking loose and flowing to blood vessels in the brain causing strokes. It takes 24-48 hours for those clots to form, so there is a window of opportunity to return the heart to a normal rhythm with medication or electricity. If the atrial fibrillation is long standing or recurrent, a decision has to be made to use warfarin (coumadin) to anticoagulate or thin the blood and prevent a stroke from happening. There are down sides to anticoagulation including blood tests and dose adjustments since it takes trial and error to get the warfarin dosing just right. And then there is always the risk of bleeding from minor bumps.

The risk of stroke for younger, healthy patients is about 1% per year but for those a little older who may have other underlying medical conditions, it could be as high as 8-9% per year. The bleeding complications of anticoagulation run about ½ % per year, so a risk-reward discussion needs to happen with patients to decide if blood thinning is for them.

Symptoms of A Fib may also include palpitations from the irregular and sometimes rapid heart beat. This fast heart rate may cause shortness of breath, lightheadedness and weakness. Medication may be needed to keep that heart rate under control and often atrial fibrillation is an acceptable, safe rhythm as long as the rate is not too fast or too slow.

Atrial fibrillation affects more than 2 million people in the US and while most are older, it is not just a geriatric illness. Some patients can go years between episodes and studies have shown that up to 90% of people with A fib don’t even know they have it. And that’s the story of Mike Hampton. He walks into training camp, is told he has a problem, goes home and the problem fixes itself. Now all he has to do is walk out to the mound and throw out the first pitch.

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