Thyroid dysfunction in HCM predicts risk for sudden cardiac death, worsening HF
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Key takeaways:
- Low free triiodothyronine (T3) levels in patients with hypertrophic cardiomyopathy (HCM) may predict risk for sudden cardiac death and worsening HF.
- Low free T3 was common among adults with HCM.
Adults with hypertrophic cardiomyopathy who had lower levels of free triiodothyronine were 53% more likely to experience sudden cardiac death and were at nearly fourfold greater risk for worsening HF, data show.
“Low triiodothyronine (T3) syndrome, also known as nonthyroidal illness syndrome or euthyroid sick syndrome, is characterized by decreased plasma free T3 concentrations without elevated thyroid‐stimulating hormone (TSH) levels,” Hui‐Lin Hu, MD, of the department of cardiology in the Affiliated Hospital of Jiaxing University in Zhejiang, China, and colleagues wrote in the study background. “Lower serum free T3 levels may be detrimental to cardiovascular homeostasis because of its crucial role in regulating cardiac contractility, maintaining mitochondrial integrity and cardiac function, modulating systemic vascular resistance and post-ischemic left ventricular remodeling.”
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Hu and colleagues analyzed data from 782 patients with hypertrophic cardiomyopathy (HCM) who had baseline data on thyroid hormone level; all were admitted into the Affiliated Hospital of Jiaxing University. The mean age of patients was 49.9 years; 58.4% were men. Researchers stratified patients by normal (85.7%) and low (14.3%) serum levels of free T3. Researchers defined low T3 syndrome as a free T3 less than 2.43 pmol/L with a normal TSH level. Patients with an abnormally high or abnormally low TSH were excluded.
The primary endpoint was sudden cardiac death events; the secondary endpoint was a composite of worsening HF events, including HF death, cardiac decompensation, HF hospitalization and HCM‐related stroke.
The findings were published in Clinical Cardiology.
After a median follow‐up of 52 months, there were 75 sudden cardiac death events and 134 worsening HF events.
Kaplan-Meier survival curves showed the cumulative incidence of sudden cardiac death and worsening HF events were higher among patients with low T3 syndrome (log‐rank P = .02 and log‐rank P = .001, respectively). In Cox regression analysis, researchers found that low T3 was a strong predictor of sudden cardiac death and worsening HF events, with adjusted HRs of 1.53 (95% CI, 1.13-2.24; P < .01) and 3.87 (95% CI, 2.91-4.98; P < .001), respectively.
In the analyses, researchers adjusted for depression status, a known risk factor for adverse events in HCM and a condition often linked to thyroid dysfunction.
“Depression, by contrast, correlates with a 1.89 HR for sudden cardiac death events and a 1.76 HR for worsening HF events,” the researchers wrote.
The researchers noted that thyroid status was only measured at baseline and may have changed during follow-up.
“Low T3 syndrome is highly prevalent among patients with HCM and was associated with sudden cardiac death events and worsening HF events,” the researchers wrote. “Routine assessment of free T3 levels may provide risk stratification in this population.”
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