Re: Utility of Routine 24-Hour Electrocardiographic Holter Monitoring for Detecting Atrial Fibrillation in Patients Admitted With Acute Stroke Syndromes

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Dear Editor,

We read with interest the retrospective, single-centre observational study by Al-Busaidi et al. published in SQUMJ, in which the accuracy of 24-hour electrocardiography (Holter) in detecting atrial tachyarrhythmias, particularly atrial fibrillation, in patients admitted for acute ischaemic stroke (AIS) or transient ischaemic attack (TIA) was examined.1 Atrial fibrillation was detected in 4.4% of the 460 patients examined. Predictors for the detection of atrial fibrillation by Holter monitoring were advanced age, peripheral vascular disease, left ventricular diastolic dysfunction and chronic kidney disease. The authors concluded that Holter monitoring has a low clinical yield in detecting atrial fibrillation.

First, we disagree with the view that further investigation of paroxysmal atrial fibirllation in AIS patients should be reserved for high-risk patients. All patients with AIS or TIA should undergo continuous electrocardiogram (ECG) monitoring to determine whether permanent or paroxysmal atrial fibrillation was the cause of the AIE that led to hospitalization.

Second, the included patients were generally not admitted to a stroke unit. Stroke units have the advantage that AIS patients are continuously monitored for potential risk factors for AIS, including atrial fibrillation, arterial hypertension, diabetes and heart failure. Another advantage of a stroke unit is that AIS patients can be assessed for complications of thrombolysis or thrombectomy, and ECG and other vital signs can be continuously monitored, with a high detection rate of atrial fibrillation as a cause of AIE.2

Third, not all included patients underwent multimodal magneitc resonance imaging (MRI) to assess whether the stroke pattern on MRI indicates embolic stroke, stroke due to atherosclerosis or stroke due to systolic dysfunction. If the stroke pattern indicates an embolic stroke, an investigation for atrial fibrillation should be initiated.

Fourth, atrial fibrillation may not only be the cause of AIS or TIA, but also the consequence of AIS.3 Therefore, AIS patients should be monitored longer for arrhythmias, not only to identify the underlying cause, but also to prevent future AIS caused by newly occurring atrial fibrillation.

Fifth, the study did not state how many of the included patients already had atrial fibrillation before enrolment and how many of the included patients were anticoagulated because of it. Knowing how many of them were anticoagulated for atrial fibrillation prior to AIS is crucial to adjust the anticoagulant regimen appropriately.

Finally, the study was retrospective in nature; retrospective studies are associated with several disadvantages. They allow only limited control over the sample of the population and only limited control over the type and quality of the predictor variables. In addition, the relevant predictors may not have been recorded in the medical record, and it may be difficult or impossible to identify confounding variables and causality. Furthermore, it may be inevitable that some information is missing, as the data are based on the review of medical records that were not originally intended for the collection of data for research purposes. Selection and recall errors also affect the results.4

In summary, patients with AIS should be admitted to a stroke unit not only for proper detection of atrial fibrillation as a possible cause, but also for detection of other risk factors and to improve the overall outcome.