Medically Refractory Graves’ Disease (GD) with Wolff-Parkinson-White (WPW) Syndrome: A Therapeutic Challenge

Reported cases of coexistent GD and WPW syndrome are limited in medical literature. Beta blocker therapy is the first line rate controlling agent in thyrotoxicosis with or without atrial fibrillation (AF). Beta blockers need to be used cautiously in pre-excited syndromes.

Case Description :

A 61-year-old male developed a supraventricular tachycardia (SVT) while undergoing lower gastrointestinal endoscopy. ECG revealed regular wide complex tachycardia probably antidromic in nature which was treated with beta blockers terminating the tachycardia. Thyroid functions were arranged as he had loss of weight and a fine tremor for several months.  Despite initial rate control, he had a brief episode of fast paroxysmal AF which terminated spontaneously. The ECG revealed WPW syndrome as signified by pre-excitation and short PR interval. His TSH was < 0.0025 mIU/L (0.4-4) while free T3 >20 pg/dL (1.6- 3.9) and free T4 3.52 pg/dL (0.7-1.7). GD was diagnosed with a high thyrotropin receptor antibody level of 8.4 IU/L ( < 2). As he had WPW syndrome, beta blockers were not prescribed for rate control of thyrotoxicosis. It was decided that the best approach at that point was to ablate the accessory pathway. He underwent successful curative radiofrequency ablation (RFA) of the left sided accessory pathway.

 He continued to have a severe toxic state with medically refractory GD with high doses of thioamides, cholestyramine and lithium carbonate. Persistent tachycardia and post-procedure AF was treated with beta blockers. Ultimately his toxic state was brought under control with radioactive ¹³¹I therapy. 

Discussion :

There is no established relationship of GD and WPW. Thyrotoxicosis precipitates tachyarrhythmias by direct action of thyroid hormone on cardiac conduction system. SVT in thyrotoxicosis is successfully treated with adequate beta blockade. Even in WPW syndrome the cardiac conduction occurs through the atrioventricular node (AVN). When the AVN is blocked with beta blockers due to unopposed conduction via the accessory pathway, atrioventricular re-entrant tachycardia (AVRT) can be made worse and more rapid which can lead to fatal ventricular tachyarrhythmia. The risk is higher in antidromic conduction than in orthodromic conduction. Direct current cardioversion is the treatment of choice for acute therapy for antidromic AVRT. Beta blockers are better avoided in that context.  Beta blockers are contraindicated in pre-excited AF. The best treatment option in this context is RFA and beta blockers can be safely prescribed for GD following a successful procedure.