Thyroid Diseases/complications

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Editorial

Subclinical Thyroid Dysfunction was not Associated with Cardiac Arrhythmias in the Cross-Sectional Analysis of the ELSA-Brasil Study

Brazil lacks large cohort studies with analyses of incidence and prevalence of diseases in all areas. In this context, the ELSA-Brasil study was an important milestone for the evaluation of cardiovascular diseases in the country. This study shows a very detailed means of exposing relevant facts to the occurrence or not of arrhythmogenic electrocardiographic manifestations in patients with subclinical thyroid hormone disorders. This issue is extremely relevant, has biological plausibility and generates several doubts regarding the patient.

The study included a relevant sample of 13,341 patients in total, with a mean age of 51 years. The data collection, electrocardiographic specifications and laboratory tests were protocolized according to predetermined and uniform specifications in all patients. Moreover, they were comprehensively evaluated, from arrhythmias supposedly more frequent in thyroid disorders such as atrial fibrillation, plus basal heart rate, presence of extrasystoles and conduction intervals.

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Original Article

Subclinical Thyroid Dysfunction was not Associated with Cardiac Arrhythmias in a Cross-Sectional Analysis of the ELSA-Brasil Study

Kamilla Maria Araújo Brandão Rajão et al. Antônio Luiz Pinho Ribeiro Valéria Maria Azeredo Passos Isabela Judith Martins Benseñor … Pedro Guatimosim Vidigal Cleber Pinto Camacho Maria de Fátima Haueisen Sander Diniz

Abstract

Background:

The association of subclinical thyroid dysfunction (STD) with cardiac arrhythmias remains controversial, particularly in the non-elderly population.

Objective:

To investigate whether STD was associated with cardiac arrhythmias in a cohort of middle-aged and older adults.

Methods:

Baseline data of the Longitudinal Study of Adult Health, ELSA-Brasil (35-74 years) were collected from 2008 to 2010. After exclusion of clinical hypothyroidism and hyperthyroidism, participants were categorized as euthyroidism (TSH = 0.4-4.0 µU/mL), subclinical hypothyroidism (TSH > 4.0 µU/mL; FT4 = 0.8-1.9 ng/dL), and subclinical hyperthyroidism (TSH < 0.4 µU/mL; FT4 = 0.8-1.9 ng/dL). The prevalence rates of tachycardia (HR > 100) and bradycardia (HR < 60), atrial fibrillation/flutter, conduction disorders, extrasystoles, low QRS voltage, prolonged QT intervals, and persistent supraventricular rhythms were compared between groups after adjusting for age, sex, comorbidities, lifestyle, body mass index and medications.

Results:

The HR data of 13,341 participants (52% female; median age, 51 years) and the electrocardiogram readings of 11,795 were analyzed; 698 participants (5.23%) were classified as subclinical hypothyroidism, 193 (1.45%) as subclinical hyperthyroidism, and 12,450 (93.32%) as euthyroidism. The prevalence of rhythm and conduction disorders was similar, as were HR medians, even in the subgroups with TSH 10.0 UI/mL or in older adults. Conduction disorders were less prevalent in older adults with subclinical hypothyroidism (adjusted OR = 0.44; 95% CI 0.24 to 0.80).

Conclusion:

In this large, multicenter and cross-sectional study, STD was not associated with cardiac arrhythmias, but a longitudinal assessment is necessary.