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[Hyperthyroidism and atrioventricular block. Pathogenic hypothesis. Apropos of a case and review of the literature]
F Toloune1, A Boukili, D Ghafir
1Service de médecine B, hôpital militaire dínstruction Mohammed V, Rabat, Maroc.
Insights
Graves' disease can cause heart conduction problems like atrioventricular block (AVB). Treatment of hyperthyroidism resolved the patient's AVB, suggesting a link between thyroid hormones and cardiac autonomic function.
Area of Science:
- Cardiology
- Endocrinology
- Electrophysiology
Background:
- Graves' disease, an autoimmune disorder, leads to hyperthyroidism.
- Hyperthyroidism can affect cardiac function, including heart rhythm and conduction.
- Atrioventricular block (AVB) is a condition where the electrical signal between the heart's upper and lower chambers is delayed or blocked.
Observation:
- A 26-year-old male with Graves' disease presented with first-degree and intermittent second-degree (Lucciani-Wenckebach type) atrioventricular block.
- The AVB exhibited characteristics of a nodal block.
- Conduction abnormalities resolved following successful treatment of hyperthyroidism.
Findings:
- The study suggests a potential link between excessive thyroid hormone levels and the development of atrioventricular block.
- The observed AVB appeared to be nodal, indicating the block occurred in the atrioventricular node.
- Resolution of AVB after hyperthyroidism treatment supports the role of thyroid hormones in cardiac conduction.
Implications:
- This case highlights the importance of considering thyroid dysfunction in patients with unexplained heart conduction abnormalities.
- The findings support the hypothesis that excessive thyroid hormones may exacerbate autonomic nervous system activity, leading to conduction defects.
- Further electrophysiological studies are warranted to elucidate the precise mechanisms linking hyperthyroidism and atrioventricular conduction disorders.
Abstract:
The authors report the case of a 26-year old male patient who had Graves' disease with a first degree atrioventricular block (AVB) and intermittent episodes of a second degree AVB of the Lucciani-Wenckebach type. These disorders of conduction had features characteristic of a nodal block and disappeared after treatment of the hyperthyroidism. The pathogenesis of atrioventricular conduction disorders in hyperthyroidism remains controverted. The authors put forward the following hypothesis: under the influence of thyroid hormones in excessive amounts, the autonomic nervous system would act by reciprocal excitation and exacerbate a patent or latent hypervagotonia which was pre-existent to the hyperthyroidism. This hypothesis needs to be tested by intracardiac electrophysiological studies with atrial stimulation.