Low Thyroid Hormone Levels Linked to Increased Risk of Adverse Events in Hypertrophic Cardiomyopathy Patients

Hypertrophic cardiomyopathy (HCM) is a common genetic heart disorder known for its association with sudden cardiac death and progressive heart failure. Concurrently, thyroid dysfunction has been linked to heightened cardiovascular risks. A recent study published in Clinical Cardiology by Chao-Jie and colleagues found out that low T3 levels were linked to increased risk of complications in individuals with HCM.

The study involved a cohort of 782 patients diagnosed with HCM who had baseline data on thyroid hormones and were admitted to the Affiliated Hospital of Jiaxing University.

Patients were categorised into two groups based on their levels of free triiodothyronine (fT3): those with normal fT3 levels and those with low triiodothyronine (T3) syndrome.

Low T3 syndrome was defined as having fT3 levels below 2.43 pmol/L while maintaining normal thyroid-stimulating hormone (TSH) levels. Patients with abnormal TSH levels were excluded from the study.

The primary endpoint of the study was the occurrence of sudden cardiac death (SCD), while the secondary endpoint included a composite of worsening heart failure (WHF) events, encompassing heart failure-related death, cardiac decompensation, hospitalisation for heart failure, and HCM-related stroke.

Survival analysis was conducted using Kaplan–Meier and Cox regression methods.

• After a median follow-up of 52 months, the study recorded 75 SCD events and 134 WHF events.
  
• Kaplan–Meier survival curves revealed that patients with low T3 syndrome had a significantly higher cumulative incidence of SCD events and WHF events (log-rank p = .02 and log-rank p = .001, respectively).
• Multivariate Cox regression analysis showed that low T3 syndrome emerged as a strong predictor of both SCD events and WHF events, with adjusted hazard ratios (HR) of 1.53 (95% confidence interval [CI]: 1.13–2.24, p < .01) and 3.87 (95% CI: 2.91–4.98, p < .001), respectively.

The study's findings suggest that low T3 syndrome is prevalent among HCM patients and is independently associated with a higher risk of sudden cardiac death and worsening heart failure events. Routine assessment of serum fT3 levels may prove valuable in risk stratification for individuals with HCM. These results could potentially influence clinical practice and help identify patients at greater risk of adverse cardiovascular events.

Reference:

He, C.-J., Zhu, C.-Y., Fan, H.-Y., Qian, Y.-Z., Zhai, C.-L., & Hu, H.-L. (2023). Low T3 syndrome predicts more adverse events in patients with hypertrophic cardiomyopathy. Clinical Cardiology. https://doi.org/10.1002/clc.24156