Subclinical hypothyroidism (SCH) is associated with impaired left atrium (LA) dysfunction, and assessment of LA function may aid in identifying patients with SCH at increased risk for heart failure, according to study results published in the Journal of Clinical Endocrinology and Metabolism.
Previous studies suggested an association between SCH and increased risk for heart failure, but the underlying mechanism is not entirely clear. As left ventricular global longitudinal strain (LVGLS) and LA phasic strain are potential predictors of heart failure, the objective of the current study was to determine the link between SCH and subclinical left heart dysfunction in patients without overt cardiac disease.
The study enrolled 1078 (mean age, 62±12 years; 56% men) patients who underwent extensive cardiovascular health checkups, including laboratory tests and 2-dimensional speckle-tracking echocardiography, to assess LVGLS and LA reservoir, conduit, and pump strain, as part of the Subclinical Cardiac Dysfunction in General Population study, which focused on subclinical cardiac dysfunction. Of these, 78 (7.2%) participants were diagnosed with SCH, defined as elevated serum thyroid-stimulating hormone level with normal free thyroxine concentrations.
Speckle-tracking analysis indicated LA reservoir (37.1% vs 39.1%, respectively; P =.011) and conduit strain (17.3% vs 19.3%, respectively; P =.012) were significantly reduced in patients with SCH compared with patients who had normal thyroid function; however, left ventricular ejection fraction, LA volume index, LVGLS, and LA pump strain did not differ among the groups.
On multivariable linear regression analyses, SCH was associated with impaired LA reservoir strain, independent of traditional cardiovascular risk factors and laboratory and echocardiographic parameters, including LVGLS (standardized β, −0.054; P = .032).
The study had several limitations, including the cross-sectional design and limited number of patients with severe SCH (thyroid-stimulating hormone levels >10 mIU/L).
“This study demonstrated a significant association between SCH and subclinical LA dysfunction in a large sample of the general population without overt cardiac disease,” concluded the researchers. “This finding may be of importance in the explanation of the underlying pathophysiological mechanism for the higher incidence of HF in individuals with SCH.”
Nakanishi K, Daimon M, Yoshida Y, et al. Subclinical hypothyroidism as an independent determinant of left atrial dysfunction in the general population. Published online October 13, 2020. J Clin Endocrinol Metab. doi: 10.1210/clinem/dgaa730