Heart Rate Variability and Heart Rate Turbulence in Hypothyroidism before and after Treatment

Abstract

Hypothyroidism may cause cardiac autonomic dysfunction. Treating hypothyroidism with L-thyroxine therapy does not effectively restore cardiac autonomic function. HRV and HRT can be used as to help monitor cardiovascular-related risk in this population.

Discriminant function analysis of the occurrence risk of abnormal electrocardiogram in thyroidectomized differentiated thyroid carcinoma patients with short-term overt hypothyroidism

“…However, this drastic fluctuation of circulating thyroid hormones, from subtle difference from physiological levels to overt hypothyroidism, may cause several abnormal cardiovascular manifestations, one of the most important targets of thyroid hormones. These abnormal manifestations would be sensitively and timely reflected on the electrocardiogram (ECG) [9,20].…”

“…Its abnormalities in long-standing hypothyroidism have been reported to include sinus bradycardia, increased QT dispersion, prolongation of QRS, flat or inverted T wave, low voltage, heart block, right bundle-branch block, and infrequently ventricular arrhythmia and torsades de pointes, depending on the severity and duration of hypothyroidism [7,[9][10][11][16][17][18]. However, as far as we know, few studies have focused on the common forms of ECG abnormality and relevant risk factors of abnormal ECG in thyroidectomized DTC patients with short-term overt hypothyroidism.…”

“…The cardiovascular system is one of the most important targets of thyroid hormones, and it has various manifestations in long-standing overt hypothyroidism, including decreased exercise tolerance [7], impaired left ventricular diastolic and systolic functions, increased systemic vascular resistance [1,8,9], and even fibrous ventricular wall remodeling [7], infrequently pericardial effusion and heart failure [10,11], However, for short-term overt hypothyroidism, it has some subtle cardiovascular manifestations, such as left ventricular diastolic dysfunction [1,12], increased night-time systolic, diastolic and mean blood pressures [13,14], and sympathovagal imbalance [15].…”

Influência do exercício físico nas alterações cardiovasculares induzidas pelo hipotireoidismo

“…(12) Este aumento está associado com os níveis das catecolaminas plasmáticas e índice de dispersão do segmento QT. (11,25,(54)(55) Akcakoyun et al (10) investigaram a influên-cia do hipotireoidismo subclínico na resposta ao exercício físico em termos de recuperação da frequência cardíaca e competência cronotrópica. Eles observaram que sujeitos acometidos por esta doença se mostram significativamente deficientes quanto às variáveis estudadas.…”

“…Em hipotireoideos clínicos, Celik et al (25) indicam que esses sujeitos têm maior variabilidade da frequência cardíaca e após seis meses de terapia com reposição hormonal de levotiroxina esta disfunção parece ser revertida. Cacciatori et al (26) ao investigarem o balanço simpatovagal de hipotireoideos clínicos em resposta aos testes de sentar e levantar (protocolo adotado para verificar diferenças na atividade nervosa autonômica entre as posições sentado e em pé), verificaram que o componente de baixa frequência, correspondente a atividade nervosa simpática, encontrava-se significativamente elevado nos sujeitos hipotireoideos, quando se colocavam de pé.…”