Altered cardiovascular vagal responses in nonelderly female patients with subclinical hyperthyroidism and no apparent cardiovascular disease

Abstract

Subclinical hyperthyroidism affects cardiovascular autonomic balance in otherwise apparently healthy nonelderly females by blunting vagal responses.

Impaired functional and hemodynamic response to graded exercise testing and its recovery in patients with subclinical hyperthyroidism

“…(9), evaluating time and frequency domain measures of heart-rate variability (24-h holter recordings) observed that SCH patients showed cardiac parasympathetic withdrawal compared to healthy controls, but such alteration was less severe when SCH patients were compared to patients with overt hyperthyroidism. In another study, nonelderly female SCH patients who were submitted to the tilt test with electrocardiographic record at rest, during espiratory sinus arrhythmia (RSA) maneuvers and after tilting, presented reduced vagal reserve at RSA maneuvers and blunted vagal response to sympathetic stimulus (7).…”

“…Thyroid hormones have relevant effects on the cardiovascular and ANS systems (5,7,8). Overt hyperthyroidism is associated with alterations in cardiac function and structure such as left ventricular hypertrophy, increased systolic function, diastolic dysfunction, impaired exercise capacity, tachycardia and sympathovagal imbalance (5,22).…”

“…The most common functional cardiac alterations include decreased diastolic function, enhanced left ventricular mass, elevated heart rate (HR), and decreased exercise performance (5,6). In addition, SCH is related to autonomic imbalance characterized by attenuated vagal activity and increased sympathetic activity (7,8). All those manifestations, however, seem to be less severe in SCH patients when compared to those with overt hyperthyroidism (9).…”

Autonomic Nervous System Function in Chronic Exogenous Subclinical Thyrotoxicosis and the Effect of Restoring Euthyroidism

“…Altered autonomic nervous system function in subclinical hyperthyroidism is also less well defined. Petretta (9), Goichot (11), and Portella (12) et al, using measures of heart rate variability, found evidence that in patients with endogenous subclinical hyperthyroidism, a reduction of cardiac parasympathetic control is present, and this is supported by findings on heart rate turbulence by Osman et al (13). However, in the study by Goichot et al (11), there were no differences in the heart rate variability measure (the ratio of low frequency power over high frequency power) that is commonly used to characterize the balance between vagal and sympathetic influences in these patients.…”

Syncope in patients with drug-resistant epilepsy without apparent cardiovascular disease

“…Protocol for implementation of IT: The software used to collect and analyze signals was the Biopotentials Uptake System developed by Barbosa et al 14,15 , which was validated for reproducibility and used in other studies 16,17 . The patients were instructed to avoid drinking autonomic nervous system stimulants such as coffee and tea, not to perform strength exercises, and to avoid smoking and/or taking any drugs for at least 24 hours before the test.…”