Outpatient cardiac monitoring for 21 days may lead to better treatment options for patients with cryptogenic stroke.
NEW ORLEANS—Continuous cardiac telemetry monitoring for at least 21 days can detect a high rate of paroxysmal atrial fibrillation (PAF) in patients with cryptogenic stroke or transient ischemic attack (TIA), according to research presented at the 2012 International Stroke Conference.
In a study of 156 patients with cryptogenic stroke or TIA, Daniel J. Miller, MD, and colleagues, detected a 19.5% rate of PAF over 21 days of monitoring.
“PAF carries a very high risk of future strokes, and that’s why it’s of particular concern to us,” said Dr. Miller, Senior Staff Neurologist at the Department of Neurology at Henry Ford Hospital in Detroit. His team sought to confirm the results of two smaller studies, determine the ideal duration for cardiac monitoring, and identify factors that might predict detection of PAF.
Detecting PAF
The researchers retrospectively reviewed 18 months of a large, tertiary care hospital’s records for patients who were monitored with the Cardionet mobile cardiac outpatient telemetry (MCOT) device, a pocket-sized machine with three leads attached to the patient’s chest. The monitoring device continuously yields two-channel ECG.
All 156 patients (78 female; 76 African American) whose records were reviewed had a cryptogenic stroke or TIA within the six months prior to monitoring, with an average NIH Stroke Scale (NIHSS) score of 3.0. Of the total group, 35% had a history of prior stroke or TIA, and 87% had hypertension. Furthermore, 97% of patients were not taking anticoagulants, and 51% were not on a rate control medication.
Most patients underwent cardiac and radiologic testing, with 100% completing MRI or CT, 96.1% completing echocardiography, and 94% completing ECG.
Outpatient monitoring with the Cardionet MCOT device detected PAF in 27 of the 156 patients (17.3%), though researchers recorded a 19.5% rate after accounting for those who had been monitored for fewer than 21 days. The 19.5% rate “reflects the calculated rate if the entire group had been monitored for 21 days,” Dr. Miller told Neurology Reviews.
Of the detected PAF episodes, two-thirds were fewer than 30 seconds, 26% were greater than 30 seconds, and 7.5% were persistent. Patients experienced a statistically significant increase in PAF episodes over time—3.8% had PAF detected by 48 hours, 9% by seven days, 15.1% by 14 days, and 19.5% by 21 days.
Based on these intervals, a minimum of 21 days is the best duration of monitoring, said Dr. Miller, though “further study is needed to identify the optimal monitoring duration beyond 21 days and to investigate for the exact association of short episodes of atrial fibrillation and their risk for recurrent stroke in these patients.” At this time, “we just don’t know if these episodes of less than 30 seconds are associated with the same future stroke risk as those episodes greater than 30 seconds,” said Dr. Miller.
Risk Factors and Treatment
The investigators also identified risk factors for PAF detection, including female gender, increased left atrial diameter and decreased left ventricular ejection fraction, increasing NIHSS scores, and premature atrial complex on ECG, which was the strongest risk factor. “The risk factors were not completely unanticipated and have all been associated with atrial fibrillation in one way or another,” said Dr. Miller, “but there has still been only a limited amount of data in this specific population of cryptogenic stroke applied in this way…. These risk factors may help us further tailor our decision to monitor or not.”
Because approximately one-third of strokes are cryptogenic, a significant number of patients could potentially be monitored for PAF with the Cardionet MCOT device, according to Dr. Miller. The standard treatment for patients with cryptogenic stroke—aspirin—may not be ideal for those who have had PAF detected. “Warfarin has been proven to be superior to aspirin in many prior studies of patients with atrial fibrillation, and this effect is even greater in those with a history of stroke,” said Dr. Miller. He added that patients with PAF could potentially be treated with new, FDA-approved anticoagulation drugs as well.
Dr. Miller stressed the importance of reducing future stroke risk by monitoring stroke patients for the optimal amount of time. “The take-home message is that prolonged cardiac monitoring of at least 21 days is warranted to detect atrial fibrillation in those with cryptogenic stroke or TIA,” he concluded.
—Lauren LeBano