BOSTON — Physicians must be more aggressive in the way they use warfarin to treat patients with atrial fibrillation, even if most fibrillation episodes are of relatively short duration.
“If a patient with atrial fibrillation has risk factors for stroke, I recommend that they take warfarin unless there is a strong reason not to” and even when the fibrillation episodes are short duration, Dr. Albert L. Waldo said at an international symposium on atrial fibrillation sponsored by Massachusetts General Hospital.
Patients who usually have fibrillation episodes of just a few minutes can also have episodes that sometimes last several hours, he noted, and even short episodes can produce a clot.
“How long does it take blood to clot?” said Dr. Waldo, professor of cardiology and medicine at Case Western Reserve University in Cleveland.
Despite the importance of oral anticoagulation for patients with atrial fibrillation, many patients never get warfarin treatment.
Dr. Waldo cited evidence that he and his associates recently compiled by reviewing the records of 945 atrial fibrillation patients who were treated at 38 hospitals in 28 states.
All hospitals participated in the National Anticoagulation Benchmark and Outcomes Report program.
Patients were seen during 2002 at 37 hospitals and during July 2000-December 2002 at one hospital. In 2001, the most recent guidelines for management of atrial fibrillation were published by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology; these guidelines highlighted the need for warfarin treatment in virtually all atrial fibrillation patients, especially those at high stroke risk.
Among the 814 patients reviewed who met the criteria for having a high risk of stroke, 45% did not receive warfarin (and 25% received aspirin but no warfarin). Warfarin was also withheld from 46% of the moderate-risk patients and from 60% of low-risk patients.
The records were also reviewed for reasons these patients were considered to have high bleeding risk and therefore did not get warfarin. No explanation was found in the records of 43% of the patients not on warfarin. A risk for falls was cited for 42%—“not a good reason to withhold warfarin,” according to Dr. Waldo. Other reasons were neuropsychiatric impairment, a past bleeding episode, or peptic ulcer disease.
The patients with the highest risk of stroke were those with a history of stroke, transient ischemic attack, or systemic embolic event. Of the 196 patients in this group, 39% received no warfarin (21% received aspirin but no warfarin).
Age is another risk factor for stroke. In the analysis, 48% of patients aged 75 or older did not get warfarin, a striking divergence from the treatment guidelines, which call for warfarin for all patients in this age group.
“Many physicians base warfarin treatment on their own impressions and intuition rather than on the guidelines,” Dr. Waldo said at the symposium, also sponsored by the Academy of Health Care Education.
Significant predictors of warfarin use were assessed in a logistic-regression model. In this analysis, a perceived or actual bleeding risk reduced the likelihood that a patient would get warfarin by about 28%, and age older than 80 years reduced use of warfarin by about 34%.
Patients with persistent or permanent atrial fibrillation were 80% more likely to get warfarin, and those with a history of a stroke, transient ischemic attack, or embolic event were 59% more likely to get warfarin.
Catheter ablation of atrial fibrillation cannot be presumed to eliminate a patient's risk of stroke and need for oral anticoagulation, because a significant number of patients have recurrences following ablation, said Dr. Waldo. He recently sent a survey to 353 physicians who treat patients with atrial fibrillation; most of the physicians were members of the Heart Rhythm Society. He received 151 replies, of which 134 were from physicians who perform catheter ablations.
Virtually all responders said they would eventually stop treatment with warfarin in patients with no other risk factors for stroke. The time frame for stopping treatment varied, but most responders said they would halt warfarin if no recurrences appeared by 6 months after treatment.
But for patients at high risk for stroke because of their age or clinical history, most responders said they would not stop warfarin treatment, Dr. Waldo said.