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FACULTY DISCLOSURE STATEMENT
In accordance with the Accreditation Council for Continuing Medical Education (ACCME) Standards for Commercial Support, educational programs sponsored by Indiana University School of Medicine (IUSM) must demonstrate balance, independence, objectivity, and scientific rigor. All faculty, authors, editors, and planning committee members participating in an IUSM-sponsored activity are required to disclose any relevant financial interest or other relationship with the manufacturer(s) of any commercial product(s) and/or provider(s) of commercial services that are discussed in an educational activity.
COMMITTEE AND AUTHOR DISCLOSURE
Statements of Disclosure of Relevant Financial Relationships have been obtained from Jeffrey Mossler, MD. Dr. Mossler has disclosed that he has no relevant financial relationships with any commercial interests.
After reading this article, the reader should be able to:
• Identify the major risk factors for atrial fibrillation (AF).
• Describe the ways in which AF is diagnosed.
• Understand the factors to consider when prescribing an anticoagulant for a patient with AF.
•Discuss the treatments for reestablishing normal sinus rhythm in AF.
• Outline the benefits and risks of using radiofrequency ablation for AF.
Date of original release: August 2014
Date of expiration: August 2015
Note: While it offers CME credits, this activity is not intended to provide extensive training or certification in the field.
Overview of Atrial Fibrillation
Atrial fibrillation, or AF, the most common cardiac arrhythmia, is a supraventricular tachyarrhythmia with uncoordinated atrial activation resulting in ineffective atrial contraction.1 AF affects more than 2.5 million American adults and accounts for approximately one-third of hospitalizations for cardiac rhythm disturbances.2
The greatest threat to patients with AF is stroke. Blood pooling, usually in the left atrial appendage, creates atrial thrombi, thus increasing the risk of stroke or peripheral thromboembolism and requiring patients with AF to maintain regular anticoagulant therapy.1 The hemodynamic instability caused by AF can result from a combination of ventricular rate control that is either too rapid or too slow, loss of coordinated atrial contraction, beat-to-beat variability in ventricular filling, and activation of the sympathetic nervous system.1
The most common symptom experienced by patients is fatigue. Other symptoms include dyspnea, hypotension, syncope, or heart failure. Some patients experience no symptoms at all. The most common risk factor for AF is age, and primary care physicians are increasingly diagnosing AF in their aging Baby Boomer patients. Medical experts expect that its incidence and prevalence is likely to rise until 2030.3 Other risk factors for AF include hypertension, diabetes, and heart attack (Table 1).
A 55-year-old full-time driver for a package delivery company develops recurring episodes of a racing heart along with shortness of breath and lightheadedness. He has hypertension but no other cardiac problems. The patient is diagnosed with paroxysmal atrial fibrillation, a condition in which upper chambers of the heart—the atria—no longer follow normal, regular rhythm but instead develop multiple random and frequently fast rhythms.
Diagnosis for Clinicians
Electrocardiographic documentation is the gold standard in establishing a diagnosis of AF. In addition to the ECG, diagnosis is based on the patient’s clinical history and physical examination. Ambulatory rhythm monitoring (e.g., telemetry, Holter monitor, event recorders), implanted loop recorders, pacemakers or defibrillators, or, in rare cases, electrophysiological study can also help confirm the diagnosis.1
In early 2014, the American Heart Association, American College of Cardiology, and the Heart Rhythm Society released the 2014 Guideline for the Management of Patients with Atrial Fibrillation. The Guideline, last updated in 2011, was developed after experts reviewed and synthesized the most recent and accurate research available. According to the Guideline, AF is classified into five types (Table 2).
Case Study (cont.)
The AF patient is initially treated with medications and cardioversion. The patient says he felt better when his heart was in normal sinus rhythm, but he continues having problems with a racing heart, which interferes with his work. His heart rhythm problem evolves into atrial flutter, a “sister” rhythm to AF that is difficult to control but possible to treat with a catheter-based procedure called radiofrequency (RF) ablation. The flutter is terminated with a successful ablation, but a persistent AF continues to be a problem, and the patient again requires cardioversion.
The goal of treatments for AF is to control symptoms so patients can return to their previous level of activities and reduce risk of stroke. According to Jeffrey R. Mossler, MD, service line chief of cardiology and senior electrophysiologist with IU Health Physicians, choosing the correct treatment for AF depends on several factors: “Clinicians need to determine how long patients have been in AF, how symptomatic they are and to what degree symptoms interfere with their daily lives, and if their hearts have structural abnormalities or chronic conditions that could precipitate or complicate AF.”
Most patients in the U.S. with AF are treated with rate control.6 But the goal of most electrophysiologists, including Dr. Mossler, is to convert patients back to normal sinus rhythm, or NSR. Methods to achieve NSR include cardioversion with direct current, antiarrhythmic drugs, and radiofrequency catheter ablation.
“A patient who presents to the ED with a first episode of AF may be an appropriate candidate for direct-current cardioversion,” says Dr. Mossler. “If the patient achieves NSR but then converts back to AF, then trying an antiarrhythmic usually is the next logical step.”
“Choosing the correct antiarrhythmic medication is challenging due to the fact that all of the antiarrhythmics have serious side effects and interactions that can further damage organs already compromised by chronic disease such as diabetes,” explains Dr. Mossler. “Drugs such as sotalol, flecainide, or propafenone are less toxic but also less likely to be effective. Amiodarone is one of the most successful drugs at putting hearts back into rhythm, but it also has more serious side effects.”
How long a patient remains on a particular drug depends on how well it is tolerated and how often the patient reverts back to AF. “A patient may be able to tolerate going back into AF every couple of years, but every couple of months is unreasonable,” states Dr. Mossler.
Rate Control Medications
Dr. Mossler believes that for most patients an initial attempt to restore and maintain NSR is appropriate. But for other patients, particularly the elderly, rate control is a reasonable option to control AF.
Rate control is frequently used in the U.S. for patients who are elderly and/or having multiple comorbidities and whose symptomology does not interfere with daily living.6 The most commonly used medications to achieve rate control are beta blockers, such as atenolol, metoprolol, and carvedilol, followed by non-dihydropyridine calcium channel blockers. Other drugs that can be used are digitalis glycosides.
Most patients with AF need anticoagulation based on an evaluation of their risk for stroke. Risk is determined by assessing factors such as age; gender; liver, kidney, or heart disease; and hypertension. The Guideline recommends using the more sophisticated thromboembolic risk calculator called CHA2DS2-VASc, which is included in the updated Guideline, rather than the simpler CHADS2 calculator.
Another significant change in the Guideline is the recommendation of three new drugs for use as valid options to standard warfarin, especially in the treatment of nonvalvular AF when an appropriate international normalized ratio, or INR, cannot be maintained with warfarin. The drugs are the direct thrombin inhibitor dabigatran and the Xa inhibitors rivaroxaban and apixaban.
The benefits of the new oral anticoagulants over warfarin include more predictable pharmacologic profiles, fewer drug-drug interactions, the absence of dietary restrictions for patients, and reduced risk of intracranial bleeding.2 The major drawback is that patients cannot miss even one dose. Doing so could leave the patient without protection from thromboembolism, even if just for a short time.1 Individuals who cannot maintain an INR with warfarin may benefit from these new anticoagulants.4
The use of aspirin to prevent strokes falls out of favor in the new Guideline, stating that the evidence for the use of aspirin is weak.
Case Study (cont.)
The patient eventually decides he wants a more permanent therapy that would improve his quality of life and allow him to continue working. He undergoes catheter-based AF ablation. This complex procedure is designed to isolate the sites of randomly generated rhythms to allow the normal heart rhythm to pace the heart without disruptions.
Dr. Mossler explains that an ablation is often considered when the first antiarrhythmic fails and the patient does not want to try a second drug. “The longer patients have been in AF, the more likely a single ablation will be insufficient,” he says. “Some patients are eager to try an ablation but need to understand that, although the incidence is low, an ablation carries major risks, such as air embolism, cardiac tamponade or perforation, and atrial-esophageal fistula. Other patients may prefer not to pursue an ablation initially, but may waiver when symptoms become more difficult to tolerate.”
During catheter ablation, a series of thin, flexible catheter wires are threaded into the heart. Electrodes, based at the tip of the catheters, stimulate the heart and record its electrical activity (Figure 1). An intricate process of creating an electroanatomic map detailing the source of the abnormal heartbeats is completed. A defined energy source, such as radiofrequency, is then used to send energy through the catheter to the mapped areas. “The energy safely destroys the small areas of heart tissue, creating a scar line that results in a barrier. When effectively established, this barrier can resolve up to 80 percent of recurrent AF,” describes Dr. Mossler.
Catheter ablation is an interventional procedure to consider in patients with AF who do not respond to medications or continue to have breakthrough episodes of AF.5 While the procedure can be highly successful in appropriate patients, it also has serious risks. Catheter ablation is used judiciously after a thorough discussion of the benefits and risk with patients.
But now that clinicians are gaining more experience with the procedure, the use of catheter ablation is increasing. “There is a consensus from experts on the subject to perform ablation earlier on,” asserts Dr. Mossler. Indeed, one of the most notable changes in the 2014 Guideline is the recommendation to use ablation for symptomatic paroxysmal AF refractory or intolerant to at least one class I or III antiarrhythmic medications (see Guideline for classification of medications) when the goal is to achieve rhythm control.
Case Study (cont.)
The ablation is successful. Although the patient continues to have a limited and decreasing number of palpitations for a few months during his initial recovery, his heart rhythm returns to stable normal sinus rhythm. An EKG performed on the patient a year later shows the patient’s heart is in normal sinus rhythm with a rate of 90 beats per minute. He is able to discontinue medications to thin his blood. Now, at age 61, the patient remains free of palpitations. He continues to take his medications for hypertension, but no longer has to deal with unpredictable episodes of a racing heart.
“The longer patients have been in AF, the more likely a single ablation will be insufficient. Some patients are eager to try an ablation but need to understand that, although the incidence is low, an ablation carries major risks, such as air embolism, cardiac tamponade or perforation, and atrial-esophageal fistula.”
In an ongoing effort to advance the care of patients with AF, IU Health is conducting a study of focal impulse and rotor mapping (FIRM)-guided ablation in paroxysmal AF. This strategy for enhanced targeting has the potential for improving success rates and lowering the risk of complications.
But now that clinicians are gaining more experience with the procedure, the use of catheter ablation is increasing. “There is a consensus from experts on the subject to perform ablation earlier on,” asserts Dr. Mossler.
Dr. Mossler received his medical degree from Indiana University School of Medicine and completed an internship and residency in internal medicine at Indiana University Medical Center. He completed a fellowship on cardiovascular diseases and a senior fellowship on electrophysiology, both at IU School of Medicine, Krannert Institute of Cardiology. His clinical areas of interest are congestive heart failure, electrophysiology, arrhythmia management, pacemaker and ICD implants, syncope evaluation, and cardiac resynchronization.
Dr. Mossler is a member of the American College of Cardiology, the Heart Rhythm Society, and the Boston Scientific Midwest Advisory Board. He is board certified in internal medicine, cardiology, and electrophysiology.
January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2014.
Heart Rhythm Society. Atrial fibrillation (AFid) awareness. Available at: http://www.hrsonline.org/News/Atrial-Fibrillation-AFib-Awareness #axzz319RKNhXt.
Colilla S, Crow A, Petkun W, Singer DE, Simon T, Liu X. Estimates of current and future incidence and prevalence of atrial fibrillation in the U.S. adult population. Am J Cardiol. 2013;112(8):1142-1147.
Zuccotti G, Pflomm, J-M. Rethinking warfarin for atrial fibrillation. JAMA. 2014;311(12):1226.
Hunter RJ, Berriman TJ, Diab I, et al. A randomized controlled trial of catheter ablation versus medical treatment of atrial fibrillation in heart failure (the CAMTAF trial). Circ Arrhythm Electrophysiol. 2014;7(1):31-38.
Steinberg BA, Holmes DN, Ezekowitz MD, et al. Rate versus rhythm control for management of atrial fibrillation in clinical practice: results from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) registry. Am Heart J. 2013;165(4):622-629.