Endocrine Abstracts

Background: The aim of this case report is to underline the possible etiological link between paroxysmal supraventricular tachycardia (PSVT) and hypothyroidism, although supraventricular arrhythmias are ordinary features of hyperthyroidism. We present the case of a patient with repetitive episodes of PSVT whose autoimmune hypothyroidism was diagnosed and thyroxin replacement therapy leaded to remission of arrhythmia.

Methods: A 47 year old women with a long history of smoking, coffee drinking and stressful environment presented two episodes of palpitation, dyspnea, dizziness and anxiety. The electrocardiogram revealed supraventricular tachycardia with 200 beats/minute (PSVT). The possible triggers of arrhythmia were investigated.

Results and discussion: In our patient, hypothyroidism was diagnosed (FT4=11.25 pmol/l (normal range: 12–22) and TSH=26.37 μUI/ml (normal range: 0.27–4.2)) as a result of chronic Hashimoto Thyroiditis (anti TPO>1/640). Laboratory analysis showed just a slightly increase of cholesterol level, with no electrolyte disturbances. Structural heart disease and systemic vasculitis were investigated and excluded. Thyroxin replacement therapy was started first 25 μg/day, then 50 μg/day. Clinical signs improved substantially and no other episode of PSVT was noted. Although we cannot deny the possible contribution of coffee, smoking and stress in revealing PSVT, the disappearance of the arrhythmia after restoration of euthyroidism suggests that hypothyroidism might serve as a trigger for PTSV.

Conclusions: Prolonged conduction, low voltage, sinus bradycardia and different atrio-ventricular or brunched blocks are classical sings of hypothyroidism, however, our case suggests that PSVT can also be part of the cardio-vascular anomalies during hypothyroidism. The mechanisms involved in the occurrence of tachyarrhythmia in hypothyroidism could be: alteration of myocyte-specific gene expression, interstitial oedema, myofibril swelling with loss of striation, increased arterial stiffness, endothelial dysfunction, premature atherosclerosis, disturbances of the sympathetic-vagal tone with a relative increase in sympathetic tone and autoimmunity.