Relation of subclinical hypothyroidism and mortality among ST segment elevation myocardial infarction patients undergoing percutaneous coronary intervention

Introduction: Subclinical hypothyroidism (SCH) is defined as a serum thyroid-stimulating hormone (TSH) level above the upper limit of normal, despite normal levels of serum free thyroxine (T4). We investigated the possible relation of SCH on short and long term outcomes in a large cohort of patients with ST elevation myocardial infarction (STEMI) treated with primary coronary intervention (PCI).

Material and methods: We evaluated TSH and free T4 levels of 1593 STEMI patients without known history of hypothyroidism or thyroid replacement treatment who were admitted to the coronary care unit between January 2008 and August 2017. The presence of SCH was defined as TSH levels ≥5 mU/ml in the presence of normal free T4 levels. Patients were assessed for short and long term outcomes.

Results and discussion: The presence of SCH was demonstrated in 68 (4.2%) of STEMI patients. Patients with SCH had significantly lower left ventricular ejection fraction (44±9 vs 47±8, p=0.014). Long term mortality was significantly higher among those with SCH than those without SCH (log rank p =0.002). Following the performance of a multivariable cox regression model, SCH was independently associated with both 30-day (HR 3.24, 95%CI: 1.22-8.63, p=0.02) and long-term mortality following STEMI (HR 2.17, 95%CI: 1.24-3.79, p=0.007).

Conclusion: Among STEMI patients treated with PCI, the presence of SCH is common and may serve as a significant marker for higher short and long term mortality.