Abstract
IntroductionAtrial fibrillation (AF) is the most common cardiac dysrhythmia. Current guidelines recommend obtaining thyroid-stimulating hormone (TSH) levels in all patients presenting with AF. Our aim was to investigate the utility of TSH levels for emergency department (ED) patients with a final diagnosis of AF while externally validating and potentially refining a clinical decision rule that recommends obtaining TSH levels only in patients with previous stroke, hypertension, or thyroid disease.MethodsWe conducted a retrospective, cross-sectional study of consecutive patients who presented to an ED from January 2011 to March 2014 with a final ED diagnosis of AF. Charts were reviewed for historical features and TSH level. We assessed the sensitivity and specificity of the previously derived clinical decision rule.ResultsOf the 1,964 patients who were eligible, 1,458 (74%) had a TSH level available for analysis. The overall prevalence of a low TSH (<0.3μIU/mL) was 2% (n=36). Elevated TSH levels (>5μIU/mL) were identified in 11% (n=159). The clinical decision rule had a sensitivity of 88.9% (95% CI [73.0–96.4]) and a specificity of 27.5% (95% CI [25.2–29.9]) for identifying a low TSH. When analyzed for its ability to identify any abnormal TSH values (high or low TSH), the sensitivity and specificity were 74.4% (95% CI [67.5–80.2]) and 27.3% (95% CI [24.9–29.9]), respectively.ConclusionLow TSH in patients presenting to the ED with a final diagnosis of AF is rare (2%). The sensitivity of a clinical decision rule including a history of thyroid disease, hypertension, or stroke for identifying low TSH levels in patients presenting to the ED with a final diagnosis of atrial fibrillation was lower than originally reported (88.9% vs. 93%). When elevated TSH levels were included as an outcome, the sensitivity was reduced to 74.4%. We recommend that emergency medicine providers not routinely order TSH levels for all patients with a primary diagnosis of AF. Instead, these investigations can be limited to patients with new onset AF or those with a history of thyroid disease with no known TSH level within three months.
Highlights
Atrial fibrillation (AF) is the most common cardiac dysrhythmia
The sensitivity of a clinical decision rule including a history of thyroid disease, hypertension, or stroke for identifying low thyroid-stimulating hormone (TSH) levels in patients presenting to the emergency department (ED) with a final diagnosis of atrial fibrillation was lower than originally reported (88.9% vs. 93%)
When elevated TSH levels were included as an outcome, the sensitivity was reduced to 74.4%
Summary
Atrial fibrillation (AF) is the most common cardiac dysrhythmia. Current guidelines recommend obtaining thyroid-stimulating hormone (TSH) levels in all patients presenting with AF. Validation of a Rule for Selective TSH Screening causes and contributors to the condition, including thyroid dysfunction.[7,8,9] Atrial fibrillation has long been observed to be a sequela of hyperthyroidism This relationship has been described in both clinical and subclinical hyperthyroidism, with overt hyperthyroidism conferring up to a five-fold increase in the relative risk of developing AF.[10,11,12] Patients with subclinical hyperthyroidism or even high normal thyroid function have been shown to be significantly more likely to develop AF, with as much as a three-fold increase in risk.[13,14] More controversial is the relationship of hypothyroidism and AF. While early studies suggested an association between the two conditions,[15,16,17] others have indicated that hypothyroidism might be protective against developing AF.[18]
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