Treating Atrial Fibrillation
In normal sinus rhythm (NSR), the heart beats regularly at 60 to 100 times per minute with organized atrial and ventricular contraction. Atrial fibrillation (AF) is an abnormally rapid heart rhythm characterized by uncoordinated and chaotic atrial electrical activation. This disorganized electrical activity leads to deterioration of atrial mechanical function and blood pooling in the left atrium, one of the four chambers of the heart, which increases the risk of stroke.
Already the most frequently encountered arrhythmia in clinical practice, affecting an estimated 3 million Americans, the incidence and prevalence of AF appear to be on the rise. Census based projections estimate that by the year 2050, the US prevalence of AF will increase to 12–15 million. Atrial fibrillation is associated with a 2-7 fold increased risk of stroke and a twofold increase in mortality. AF also results in a decreased quality of life with symptoms ranging from none to shortness of breath, chest discomfort, palpitations, decreased exercise tolerance, fatigue, etc. The prevalence of AF almost doubles with each decade of life: increasing from 0.5% at age 50-59 years to 5-7% or greater in those aged 70-79 years. The average age of a patient with AF in the United States is 75 years. Because the elderly represent the fastest growing portion of our population, AF is increasingly becoming a major public health burden highlighting the need for further investigation into predisposing conditions, preventive strategies and more effective treatments.
In the United States, the greatest risk factors for the development of atrial fibrillation are hypertension and structural heart disease. These conditions, as well as the normal aging process, are associated with the development of left atrial stretching and replacement of muscular tissue with fibrous tissue, which then leads to AF. Patients who are 65 years and younger, with no history of hypertension or other predisposing risk factors for atrial fibrillation are classified as having “lone AF”. For patients with lone AF or with minimal structural heart disease, atrial fibrillation is believed to emanate most commonly from triggers at the left atrium-pulmonary vein junction.
AF is classified as paroxysmal, persistent and permanent. Paroxysmal atrial fibrillation starts and stops on its own with episodes usually lasting less than 24 hours. Persistent atrial fibrillation consists of AF lasting greater than seven days and usually requires an intervention such as electrical or chemical cardioversion to restore normal sinus rhythm. Permanent atrial fibrillation describes those patients who are in longstanding atrial fibrillation and for whom restoration of sinus rhythm has either been unsuccessful or deemed unnecessary.
AF is increasingly becoming a major public health burden highlighting the need for further investigation into predisposing conditions, preventive strategies and more effective treatments.
The treatment of atrial fibrillation entails two important concepts: The first is to define a patient’s risk for developing a stroke (CVA) from atrial fibrillation. Based on a patient’s risk factors, physicians may choose to place patients on aspirin or Warfarin to protect them from stroke. Recently, a new anticoagulant called Dabigatran was approved for treatment of patients with atrial fibrillation and risk factors for CVA. The American College of Cardiology and American College of Physicians both have detailed guidelines on how to assess an AF patient’s risk for CVA and who may be treated with aspirin or anticoagulants.
The second important aspect of treating AF addresses patient symptoms and choosing between a rate control and rhythm control strategy. When employing a rate control strategy, physicians and patients agree to accept the presence of AF and to use medical therapy to keep the heart rate at an acceptable range. AV nodal blocking agents (which slow the heart rate) such as beta-blockers, calcium channel blockers and Digoxin can be used to control a patient’s heart rate and symptoms. The rhythm control strategy is generally used for patients who have symptoms from atrial fibrillation despite adequate rate control or whose heart rate cannot be controlled with AV nodal blocking agents. In the rhythm control strategy, medications and ablation therapy are used to restore and maintain sinus rhythm. The medications are called anti-arrhythmics – they suppress abnormal rhythms of the heart. Ablation therapy uses energy directed through a catheter to small areas of the heart muscle that causes the abnormal heart rhythm. This energy “disconnects” the pathway of the abnormal rhythm. The use of anti-arrhythmic agents should be reserved for cardiologists and cardiac electrophysiologists who have a detailed understanding of the effects of atrial fibrillation and how the drugs work and interact in the body.
At St. Luke’s Hospital & Health Network, we provide comprehensive and cutting-edge therapy for patients with atrial fibrillation. The goal of St. Luke’s Atrial Fibrillation Program is to tailor medical therapy to the individual patient’s needs. Each patient is evaluated for underlying conditions that can contribute to or cause atrial fibrillation with the goal of modifying those predisposing factors. Patients are educated about their condition so they can become active participants in their medical care. We work with these patients to define a treatment strategy that will minimize their symptoms, improve their quality of life, and reduce their risk of stroke.
For many patients, treating their AF may simply require finding the right cocktail of AV nodal blocking medications to control their heart rate and of course providing protection from stroke. We frequently use Class I and Class III anti-arrhythmic agents (Flecainide, Propafenone, Dofetilide, Dronedarone, Amiodarone) to keep patients in normal sinus rhythm. This requires detailed knowledge of how the drugs work and interact in the body so that patients can be maintained in normal sinus rhythm without suffering from drug-related side effects.
For patients whose AF cannot be controlled with medical therapy or who do not tolerate medication, St. Luke’s offers catheter ablation of atrial fibrillation.(We have extensive experience in performing this procedure.) The success rate for maintaining normal sinus rhythm with an atrial fibrillation ablation varies depending on the pattern of atrial fibrillation present and the extent of structural heart disease, but approaches 80% in patients with paroxysmal AF and normal hearts. Factors that may contribute to the success of an atrial fibrillation ablation include the duration of a patient’s AF prior to the procedure, the size of a patient’s left atrium and other co-existing medical conditions such as congestive heart failure and obesity.
Atrial fibrillation can be a debilitating disease for many patients. Fortunately there continues to be advancements made in both medical therapy and ablation therapy for AF. The cardiac electrophysiology team at St. Luke’s Hospital & Health Network is dedicated to providing comprehensive, state of the art care for patients with AF.
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Darren Traub, DO, holds board certifications in cardiac electrophysiology, cardiology, comprehensive adult echocardiology and internal medicine. James P. Hummel, MD holds board certifications in cardiac electrophysiology and cardiology. Both physicians’ clinical expertise is in electrophysiology, an area of cardiology that specializes in diagnosing and treating conditions that affect the electrical impulses of the heart.