BAFS: Asymptomatic AF understudied, placing patients at higher risk

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Asymptomatic atrial fibrillation (AF), compared with symptomatic patients, are more often older and at greater risk for thromboembolism and stroke, according to research presented by John Camm, MD, of the St. George’s University of London at the 15th annual Boston AF Symposium on Jan. 14.

Because "asymptomatic AF is rarely, if ever, distinguished from symptomatic AF in clinical trials," Camm offered propositions to aid in the study asymptomatic AF.

Asymptomatic AF: More common than you think
Asymptomatic AF is a “common condition” that yields a “degradation in quality of life” for patients, “even if they deny the specific symptoms," Camm said.

While asymptomatic AF occurs in less than 1 percent of the population, it is more common than realized. Data from a small European study by the Arrhythmia Alliance measured the pulse of 470 visitors to St. George’s during a five-day period. Of the 470 visitors, 33 had an irregular pulse and eight unknowingly had AF, Camm said.

"The likelihood of AF being asymptomatic is entirely dependent on the degree of monitoring that you undertake to review those patients," he said.

In addition, Camm referred to a study that examined 4,618 residents in Olmsted County, Minn. ( Circulation 2006;114:119-125). Of these participants, 23 percent of patients had AF with silent symptoms. Older age and lower heart rate are two of the most important characteristics that distinguish patients with asymptomatic and symptomatic AF, Camm said.

“We know that AF starts out often asymptomatically and becomes symptomatic," he said. "It becomes longer, more frequent, more difficult to manage, it comes persistent and then finally permanent. During this process cardiovascular endpoints begin to accumulate.”

Patients with asymptomatic AF have a 10 percent greater risk of stroke. Camm said this is likely due to the fact that the arrhythmia goes “undiscovered or isn’t discovered and is ignored." 

Prognosis of asymptomatic AF no different than symptomatic
Camm studied whether the prognosis of asymptomatic AF is different than symptomatic AF. Results of an AFFIRM trial that divided asymptomatic and symptomatic patients showed no significant difference in prognosis. After one-year of follow up, the rates of mortality, stroke and heart failure were similar. For stroke it was 17 versus 13 percent, which was not statistically different.

Dronedarone may benefit asymptomatic AF patients

The ATHENA trial included both asymptomatic and symptomatic AF patients. In regards to drug therapy, the double-blind trial that assessed the efficacy of dronedarone (Multaq, Sanofi-Aventis) in AF patients to reduce the risk of hospitalization and death found that the rate of cardio hospitalizations sat at 24 percent. Camm offered that dronedarone therapy "might be of beneficial value" to patients with asymptomatic AF.

Because modest research exists that examines both asymptomatic and symptomatic AF in patients, questions still remain, Camm said.

“Is the conversion from symptomatic to asymptomatic an adequate therapy … is the job done?”

Although antiarrhythmic drugs and ablation techniques are heavily used to treat AF, "there is still a high recurrence rate of AF. It is often at a slower rate, it is often a shorter duration and it is very often completely asymptomatic. But does the presence of asymptomatic AF bode badly for patients? We just do not yet know," he concluded.