Atrial fibrillation is a rapid uncoordinated generation of electrical impulses by the atria of the heart. Usually, the electrical impulse for contraction of the heart begins with an impulse from the sinoatrial (SA) node in the right atria of the heart, conducted via the atria to the atrioventricular (AV) node, and on to the ventricles of the heart. With atrial fibrillation, the AV node is activated irregularly and commonly very rapidly. At times, the rate of the AV node can be so rapid the ventricles cannot fill with blood prior to their contraction and the patient's blood pressure will drop. Symptoms can include fainting, feeling tired, and stroke. Excessive alcohol, thyroid disease, hypertension, ischemic heart disease and valvular heart disease can cause atrial fibrillation. At times, atrial fibrillation can be treated and the heart rhythm returned to normal, but many times this is not possible and a patient is left with chronic atrial fibrillation. The majority of atrial fibrillation cases occur during the ages of 55 to 85.

The most serious side effect of atrial fibrillation is stroke. Half of all strokes associated with atrial fibrillation are major and disabling. The association of stroke with atrial fibrillation has been known since 1658. Depending on the presence of additional risk factors, the rate of stroke from atrial fibrillation can exceed 8 percent per year. Currently, strokes are best prevented by the careful use of Coumadin® or warfarin. The warfarin dose must be carefully adjusted to maintain the proper amount of anticoagulation (commonly called blood thinning). The test for anticoagulation is an INR and the American Academy of Chest Physicians recommends a range of 2.0 to 3.0 for most patients. Properly maintained anticoagulation requires a commitment of patients and physicians for frequent blood monitoring. There is a small subgroup of patients for whom the risk of stroke is low and these patients do not require the risk of anticoagulation. To be in this subgroup, you must never have had high blood pressure (even if currently controlled), impaired heart function (by ultrasound testing), or a prior transient ischemic attack or stroke and you must not be a female more than seventy-five years old. When the risk of anticoagulation is too great, or patients are unwilling to undergo frequent blood monitoring, then aspirin is commonly used.

Dr. Loftus was a principal investigator for a study comparing warfarin to Exanta® (Ximelagatran) for the prevention of stroke in chronic atrial fibrillation. Drug approval is pending in the US and Europe at this time.