Following an initial acute ischemic stroke, a search for the cause must be undertaken – for small vessel vasculitis, atherosclerotic emboli, thrombi from the systemic circulation, and so forth, beyond the domain of the Emergency Physician. However, what the Emergency Physician does encounter is the sequelae of this search, in the form of oral anticoagulants.
These two articles from the New England Journal of Medicine, on their own, seem to reflect advances in diagnostic yield following acute ischemic stroke or transient ischemic attack. The authors point out approximately 25% of patients suffering AIS and half of those suffering TIA never receive an ultimate identified etiology for stroke – and are classified as “cryptogenic”. The authors in each of these studies suppose this may be due to the paroxysmal nature of atrial fibrillation, and that short-term electrocardiographic monitoring is missing this diagnosis. In each study, some type of long-term monitoring technology is utilized, and, ultimately, the rate of diagnosis for paroxysmal atrial fibrillation jumps from 1-3% in each cohort to 8-12% in each cohort.
The catch – scads of authors for each report conflict-of-interest with both manufacturers of novel oral anticoagulants, or device manufacturers likely related to continuous ambulatory monitoring. There is clear benefit to each of these parties, considering potential expanded indication for both monitoring and for anticoagulation. These articles will likely be used to support both activities, despite not measuring any patient-oriented benefit. How much of a primary or recurrent stroke risk is attributable to these very-infrequent paroxysms of atrial fibrillation? Do they benefit equally from anticoagulation?
Given the conflict-of-interest enshrined in these articles, I am certain the advertised presumption will be they do. They may, of course, be right – or, this may turn into yet another example of overdiagnosis and high-cost, low-yield medicine.
“Atrial Fibrillation in Patients with Cryptogenic Stroke”
http://www.nejm.org/doi/full/10.1056/NEJMoa1311376
“Cryptogenic Stroke and Underlying Atrial Fibrillation”
http://www.nejm.org/doi/full/10.1056/NEJMoa1313600