Atrial fibrillation: common, and more dangerous than we thought

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Atrial fibrillation (AF) occurs when the heart s upper chambers the atria no longer contract in a regular, organized fashion, but merely flutter, almost vibrate, unpredictably. There are many causes of AF, and often no specific cause is detected. The fibrillating chambers directly result in two problems: the number and rate of electrical signals transmitted down to the heart s main pumping chambers, the ventricles, is irregular, and therefore so is the heartbeat (pulse), which may be too fast or too slow; and since the blood in the atria is not being forcefully ejected with each beat (since there are none), blood tends to pool there and clot, forming small mobile clots, or emboli. (Afib is not at all the same as ventricular fibrillation, which is a lethal arrhythmia requiring emergency counter-measures, including CPR and DC shock).

So AF is a major public health problem, and is becoming even more common as our population ages. Heightened concern is due to its increasing prevalence and strong association with devastating outcomes, most predominantly sudden death and stroke. Patients with AF have 4 to 5 times the risk of stroke and about double the risk of mortality compared to those without AF.

Heart attacks (myocardial infarction, MI) are an established risk factor for AF, with AF occurring in 6% to 21% of patients with MI. A new study published in JAMA Internal Medicine finds that the reverse is also true: AF is a risk factor for MI.

Researchers led by Dr. Elsayed Soliman of Wake Forest School of Medicine studied almost 24,000 subjects free of evidence of coronary heart disease over the course of almost 7 years to determine MI events and the factors possibly contributing to that risk. After adjustments for any confounding conditions, they determined that among patients with AF, the risk of MI was almost double. Women and black patients had well over two-fold the risk, but surprisingly the increased risk from AF did not depend on age of the patient. Further, while blacks and women had elevated risk, white men did not. Those taking the anticoagulant warfarin also did not have an elevated MI risk.

An accompanying editorial written by two UCSF cardiologists supports the reliability of the study s data and conclusions. They speculate upon the reasons why AF might cause MI: one possibility is a common link to inflammation, and another more obvious possibility, ie embolism of tiny clots to the coronary arteries.

ACSH s Dr. Gilbert Ross added, The days are surely long past when clinicians regarded AF as an almost routine part of aging, not worthy of much concern other than to control the heart rate. Over the past decade-plus, the major increased risk of embolic stroke has been recognized and a plethora of new, safer anticoagulants has been developed and approved to help AF patients stay on their lifesaving medication without too much risk of serious bleeding.