# Supraventricular Tachycardia Beyond the Heart: A Case of Undiagnosed Graves' Thyrotoxicosis Presenting as an Episode of Supraventricular Tachycardia

## TL;DR

A man with no obvious signs of hyperthyroidism was found to have Graves' disease after presenting with a rare heart rhythm issue.

## Contribution

Highlights an atypical presentation of Graves’ thyrotoxicosis as isolated supraventricular tachycardia without classic symptoms.

## Key findings

- SVT can be the sole presenting symptom of Graves’ thyrotoxicosis without typical systemic signs.
- Thyroid function testing should be considered in unexplained arrhythmias to avoid misdiagnosis.
- Treating the underlying thyrotoxicosis resolved the arrhythmia and improved outcomes.

## Abstract

Thyrotoxicosis is a hypermetabolic condition defined by elevated levels of triiodothyronine (T3) and/or thyroxine (T4) in the serum. While irregular heart rhythms like atrial fibrillation are commonly linked to this condition, other types such as supraventricular tachycardia (SVT) characterized by sudden onset, narrow QRS complexes, and regular RR intervals in the absence of structural heart disease are much less frequently reported and often overlooked.

We present a compelling case of Graves’ thyrotoxicosis in a middle-aged male patient, whose only presenting symptom was SVT, in the absence of typical systemic signs of hyperthyroidism or structural cardiac abnormalities. This case challenges the conventional diagnostic trajectory of thyrotoxicosis, emphasizing the importance of including thyroid function testing in the diagnostic workup of unexplained arrhythmias.

Early recognition of such atypical presentations is crucial, as appropriate treatment of the underlying thyrotoxicosis can lead to resolution of the arrhythmia and improved clinical outcomes.