Aggressive Outpatient Heart Monitoring Needed
In nearly one third of all people who suffer from a stroke, the underlying cause of the injury is not readily evident to doctors. Atrial fibrillation (AF), or an irregular heartbeat, is believed to be a significant factor in many of these cases.
Stroke researchers at Allegheny General Hospital (AGH) in Pittsburgh today are reporting in the journal Neurology that a new diagnostic approach that extends the monitoring of patients' hearts after hospital discharge greatly improved their ability to detect AF and treat it appropriately.
Led by Ashis Tayal, M.D., a stroke neurologist and medical director of AGH's Comprehensive Stroke Center, the AGH team explored the use of mobile outpatient cardiac telemetry over a period of 2-3 weeks to monitor patients who have experienced a stroke or a transient ischemic attack (TIA) of unknown cause.
Atrial Fibrillation was diagnosed in 23% of the study participants where conventional diagnostic protocols had failed.
"Stroke is an extremely challenging disease to treat and prevent when we know the cause or an individual's specific risk factors. That so many patients actually leave the hospital without a precise reason for their injury is a very frustrating scenario for physicians and one that has potentially devastating implications for patients and their families," Dr. Tayal said.
The nation's third leading cause of death, stroke is the number one cause of serious, long-term disability.
"If we can indeed identify AF more promptly in these cases, our ability to treat patients and perhaps prevent a second, more catastrophic injury would be significantly enhanced," he said.
Atrial fibrillation is the most common heart rhythm abnormality that people develop. During AF the heart's two upper chambers (the atria) beat chaotically and irregularly. The condition causes poor blood flow and the development of blood clots within the heart which can subsequently release into the arteries of the brain and cause a stroke.
Dr. Tayal said the conventional approach to evaluating stroke patients is an extensive in-hospital diagnostic work-up that includes neurological imaging such as MRI and angiography and cardiovascular studies, such as telemetry and holter monitoring, that assess the heart's rhythm.
"Intermittent AF becomes more common as we grow older and as a known risk factor for stroke, the current standard of care when the cause of injury is unclear is to monitor patients with telemetry for several days in the hospital. Unfortunately, our probability of detecting AF in this brief window of time is less than 1%," Dr. Tayal said.
Using a newer, mobile telemetry system called CardioNet, Dr. Tayal and his AGH colleagues evaluated 56 patients with stroke of unknown etiology and no previous history of AF for a period of three weeks post-discharge. Hospital based telemetry and holter monitoring results for all were normal.
The CardioNet System requires no patient interaction. Via three leads attached to a lightweight sensor worn on a neck strap or belt clip, the monitor analyzes a patient's heart rhythm in real time during normal daily activities. When the system identifies an abnormal rhythm, the data is automatically transmitted to the medical team.
Over the course of three weeks, thirteen of the 56 patients in AGH's study were found to have either prolonged or brief episodes of AF. For those with prolonged incidents -- a clear indication of stroke cause -- the discovery prompted immediate therapeutic intervention with medication designed to better protect the patient from a repeat stroke.
Dr. Tayal said the results are equally important relative to those found to have brief episodes of AF.
"AF of relatively short duration -- 10, 15 seconds or so -- does not place a patient at imminent risk of a blood clot or stroke, but it may be a maker of those who are prone to a more dangerous, prolonged episode that does. Knowing that someone is predisposed to AF substantially alters our approach to treating them and may ultimately improve outcomes," Dr. Tayal said.