Non-thyroidal illness syndrome in patients with cardiovascular diseases: A systematic review and meta-analysis.

BACKGROUND: Non-thyroidal illness syndrome (NTIS) is characterized by decreased serum triiodothyronine level without increased thyroid-stimulating hormone level during critical illness. The summary data on the prevalence of NTIS in cardiovascular patients are lacking, and its prognostic role in cardiovascular patients is also unclear.

METHODS: We performed a systematic review and meta-analysis to comprehensively determine the prevalence and the prognostic role of NTIS in cardiovascular patients. The prevalence of NTIS was pooled using random-effect meta-analysis and the hazard ratios (HRs) for all-cause mortality, cardiac mortality and major adverse cardiovascular events (MACE) were also pooled.

RESULTS: Forty-one studies were finally included. The pooled prevalence of NTIS in cardiovascular patients was 21.7% (95% CI 18.4%-25.3%). Subgroup by the types of cardiovascular diseases showed the prevalence of NTIS was highest in patients with heart failure (24.5%), followed by acute myocardial infarction (18.9%) and acute coronary syndrome (17.1%). Meta-analysis of studies using strict diagnostic criteria of NITS showed that the pooled prevalence of NTIS in cardiovascular patients was 17.6% (95% CI 14.5%-21.2%). NTIS was independently associated with increased risks of all-cause mortality (HR=2.52, 95% CI 1.87-3.40, P<0.001) and cardiac mortality (HR=2.06, 95% CI 1.58-2.69, P<0.001) in cardiovascular patients. NTIS was also an independent predictor of MACE in cardiovascular patients (HR=1.73, 95% CI 1.32-2.26, P<0.001).

CONCLUSION: NTIS is very common in patients with cardiovascular diseases. NTIS is an independent prognostic factor in cardiovascular patients and is associated with increased risks of all-cause mortality, cardiac mortality and MACE.