New-onset arrhythmia associated with patients hospitalized for thyroid dysfunction

Thyroid dysfunction has been associated with cardiovascular dysfunction in the literature. However, the frequency of new-onset arrhythmias associated with thyroid disease hospitalization is unknown. Hence, we analyzed frequency, in-hospital outcomes, and resource utilization of new-onset arrhythmias associated with thyroid dysfunction hospitalizations.

The patients who were admitted with the primary reason of thyroid dysfunction were included using appropriate international classification of disease, ninth revision, clinical modification (ICD-9-CM) codes. We then identified new-onset arrhythmias using appropriate ICD-9-CM codes. We utilized the "present on admission" variable to exclude arrhythmias that were present on admission.

Among the eligible patients with thyroid dysfunction, only 3% (n=12,111) developed a new-onset arrhythmia. Atrioventricular block (1.49%) is the most frequent followed by atrial fibrillation (0.92%), ventricular tachycardia (0.47%), atrial flutter (0.23%), supraventricular tachycardia (0.1%) and ventricular fibrillation (0.07%). Patients with new-onset arrhythmias were older (mean age 76.7±12.5 years), more predominantly white (n=9008, 74.4%), higher females (n= 7632, 63%), and had a higher frequency of comorbidities. In-hospital mortality occurred in 827 (6.8%) patients with new-onset arrhythmias and 8632 (2.2%) patients without new-onset arrhythmias (P-value <0.001). The medical length of stay and cost of hospitalization was also higher in these patients.

Thyroid dysfunction is not associated with significantly higher rates of new-onset arrhythmias while inpatient. However, when developed, these arrhythmias are associated with higher mortality and resource utilization. The patients admitted to the hospital should have thyroid function checked when found to have an arrhythmia.