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Diagnosing PAF in Patients With Cryptogenic Stroke

 

 

 

By Mark Abrahams, MD
Reviewed by Philip Green, MD, Assistant in Clinical Medicine, Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York, New York

Published: 08/22/2012

 

 

 

 

In approximately 25% of cases of ischemic stroke, the cause remains unknown despite comprehensive evaluation, resulting in a default diagnosis of cryptogenic stroke.1 Atrial fibrillation (AF) is a known risk factor for ischemic stroke, and part of the workup for any patient presenting with ischemic stroke is a history and ECG to assess for AF. However, because AF is frequently asymptomatic and/or paroxysmal, it may remain undetected. In such cases, guidelines recommend antithrombotic therapy with antiplatelet agents such as aspirin. In contrast, in cases where AF is definitively diagnosed, oral anticoagulation is recommended and is known to have superior stroke prevention properties compared to antiplatelet agents.1,2

In patients presenting with ischemic stroke, any diagnostic approach that would increase the ability to accurately diagnose paroxysmal AF (PAF) and intervene with an appropriate stroke prevention strategy would be of clear value. This article examines the insidious nature of PAF, how the diagnosis is often missed in patients with cryptogenic stroke, and evidence suggesting that prolonged ECG monitoring may significantly increase diagnostic yield.

PAF is known to carry a stroke risk equivalent to that of persistent AF forms—implying that accurate diagnosis (and subsequent stroke prevention therapy) has clear benefit.2 While a one-time or repeated 12-lead ECG has long been a standard diagnostic tool, its limitations in the diagnosis of PAF are substantial. A survey of multiple study results demonstrates the ability of prolonged continuous ECG monitoring to increase diagnostic sensitivity.

In one such study in patients with an index cryptogenic stroke, 7-day Holter monitoring resulted in a significantly higher AF detection rate of 12.5% versus 4.8% for 24-hour monitoring and 6.4% for 48-hour monitoring.3

Two studies have demonstrated the ability of event recorders to significantly increase diagnostic yield above and beyond that of a 12-lead ECG and 24-hour Holter monitoring. In these two studies, event recording of 4 to 7 days’ duration revealed AF in 14.3% and 5.7% of patients with normal ECGs and 24-hour Holter monitoring.4

Similarly, Mobile Cardiac Outpatient Telemetry (MCOT) of 21 days’ duration has been shown to accurately diagnose AF in an additional 23% of patients who would have otherwise not been so diagnosed.4

Given the above evidence, the use of prolonged ECG monitoring in patients with cryptogenic stroke in order to rule out AF may be justified.

While the optimum monitoring duration and method of AF detection after cryptogenic stroke are unknown, one ongoing multicenter study in 450 patients is investigating this issue. In the CRYSTAL AF (CRYptogenic STroke And underLying AF) study, patients with cryptogenic stroke are being randomized to either standard arrhythmia monitoring (as determined by local hospital protocol) or 6 months of continuous monitoring using an implantable cardiac monitor. The results of this study promise to be informative.1

Although, over time, the use of ambulatory ECG monitoring to diagnose AF has increased, there are presently no clear recommendations to guide clinicians. The last official comment on this topic from the American College of Cardiology/American Heart Association was in 1999—but this document seems outmoded because of advances in the relevant technology since then.3 In 2007, the Heart Rhythm Society stated that (for patients undergoing catheter or surgical ablation of AF), “The more intensively a patient is monitored and the longer the period of monitoring, the greater the likelihood of detecting both symptomatic and asymptomatic AF.”5

Moving forward, advances in implantable cardiac devices may improve our ability to diagnose and monitor AF. Given the proven ability of appropriate oral anticoagulation to prevent stroke in these patients, this would be truly positive progress.

 

 

References:

  1. Sinha AM, et al. Cryptogenic Stroke and underlying Atrial Fibrillation (CRYSTAL AF): design and rationale. Am Heart J. 2010;160:36-41.
  2. Camm AJ, et al. Usefulness of continuous electrocardiographic monitoring for atrial fibrillation. Am J Cardiol. 2012;110:270-276.
  3. Stahrenberg R, et al. Enhanced detection of paroxysmal atrial fibrillation by early and prolonged continuous holter monitoring in patients with cerebral ischemia presenting in sinus rhythm. Stroke. 2010;41:2884-2888.
  4. Ustrell X, et al. Cardiac workup of ischemic stroke. Curr Cardiol Rev. 2010;6:175-18
  5. Mittal S, et al. Ambulatory external electrocardiographic monitoring: focus on atrial fibrillation. J Am Coll Cardiol. 2011;58:1741-1749.
  6. source:medpagetoday
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September 22, 2012 - Posted by | Uncategorized

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