Mitigating the risk of stroke, heart failure, and death when treating patients with atrial fibrillation requires a careful consideration of patient characteristics and management options.
Unlike treating most conditions in medicine, in which physicians balance risk with benefit, atrial fibrillation requires weighing risks.
“In atrial fibrillation, it’s the risk of stroke vs. the risk of bleeding,” said Arnold J. Greenspon, MD, FACP, professor of medicine and director of Clinical Cardiac Electrophysiology at Thomas Jefferson University Hospital in Philadelphia, PA, during a presentation at the American College of Physicians Internal Medicine 2014 annual meeting held in Orlando, FL.
The incidence of atrial fibrillation, currently the most common arrhythmia seen in clinical practice, is expected to increase dramatically as the country’s population ages. Projections indicate the prevalence will double in the next 10 years.
The condition results in substantial morbidity and is associated with stroke, heart failure, and death. Treatment aims to mitigate those risks, taking steps to prevent stroke and control symptoms.
Not only does atrial fibrillation increase the chance of having a stroke, atrial fibrillation patients who have a stroke have larger strokes and worse outcomes. Paroxysmal atrial fibrillation does not lower the risk, Greenspon said. Anticoagulation is effective but underutilized.
“It’s important to identify patients who are at risk and treat,” he added. “Patients at risk for stroke do better on warfarin. But warfarin is difficult to use, and we don’t do well.”
Warfarin has a narrow therapeutic window: too low and it’s not effective at preventing stroke and too high, the risk of intracranial bleeding goes up. A variety of studies show that patients treated with warfarin achieve the target international normalized ration (INR) only two-thirds of the time in clinical trials and 57% of the time in clinical practice.
“Newer agents are superior to warfarin [for stroke prevention] and better with bleeding,” Greenspon said. “Aspirin is a loser. Stroke risk is high, and bleeding is about the same.”
Newer anticoagulants (dabigatran, apixaban, rivaroxaban, and edoxaban) also present management challenges. No tests exist to monitor the level of anticoagulation. Several drugs, including antibiotics, can interfere with the newer anticoagulant agents, but no means exist to measure the effect. There are no guidelines for adjusting dose related to known interactions, just for renal function. No reversal agents exist. There have been no head-to-head comparisons of the newer drugs to determine which is most effective with fewest risks.
2014 Guidelines from the American College of Cardiology, American Heart Association and the Heart Rhythm Society recommend using the CHA2DS2-VASc score for assessing risk. It includes whether the patient has heart failure, hypertension, age, diabetes mellitus, a prior stroke or transient ischemia attack, vascular disease, and female gender, all of which increase the chance of a stroke.
All moderate- and high-risk patients should receive anticoagulant therapy, which should not be stopped even if the heart rate returns to a normal sinus rhythm, he said.
“Select out the lowest-risk patients and do not treat,” Greenspon advised.
In addition to stroke prevention, treatment includes managing symptoms, controlling heart rate and rhythm. Problems persist with all of the antiarrhythmic drugs.
“They are poison with beneficial side effects,” Greenspon declared.
In clinical trials comparing controlling rate with rhythm, no difference was noted in mortality. In fact, patients treated with antiarrhythmics experienced more strokes. Greenspon hypothesized that it may have been because the patients had been taken off of anticoagulation, thinking the risk was reduced with a more normal rhythm.
“Patients treated with antiarrhythmics must be on warfarin,” Greenspon said. “Anticoagulation is extremely important for patients at high risk of stroke.”
Nonpharmacologic options for treating atrial fibrillation includes ablation and pacing for rate control, surgery and radiofrequency catheter ablation to isolate the pulmonary vein, based on the belief that atrial fibrillation has a focal activation with the trigger in the pulmonary vein. Ablation is increasingly considered as a treatment for highly symptomatic patients.