Major adverse cardiovascular and cerebral events in hypothyroid patients undergoing percutaneous coronary intervention

Zhang et al. (1) carried out a large prospective naturalistic study on patients who underwent percutaneous coronary intervention (PCI) evaluating the role of thyroid hypo-function on major clinical outcomes from in-hospital stay up to 10 years of follow up with a median observation of 3 years. The enrolled population was representative of adult patients (mean age of the whole cohort 64.6 years) with several traditional risk factors (previous cardiovascular events or coronary artery disease, hypertension, diabetes mellitus, obesity, dyslipidemia and smoking status), which accounted for high risk of cardiovascular events. The diagnosis of hypothyroidism, only defined by the presence of serum TSH level above 5 mIU/L at PCI time-point, was associated with underlying clinical features at baseline [age, female gender, history of myocardial infarction (MI), diabetes mellitus, heart failure (HF), hypertension, hyperlipidemia, arteriopathy as well as ACE/ARB and amiodarone administration] and a worse clinical composite outcome during follow up [cardiac death, MI, HF events, repeat vascularization (TRV) and stroke]. The risk of composite endpoint in hypothyroid patients remained significantly higher even after adjusting for several potential confounding factors, and accounted for about 30% of the increased risk. In detail, the greatest correlation between hypothyroidism and single endpoints was observed for MI, HF, TRV and stroke. By stratifying hypothyroid patients on the basis of serum TSH value (≥5<10 mIU/L and ≥10 mIU/L), the authors demonstrated that even a mild increase of serum TSH (≥5<10 mIU/L) was significantly associated to the composite endpoint and the occurrence of MI, although to a lesser extent as compared to patients with TSH ≥10 mIU/L, while the statistical significance was not reached for the other single endpoints. On the other hand, patients with a marked increase of serum TSH (≥10 mIU/L, defined as affected by overt hypothyroidism independently from analyzing the level of serum free thyroxin) presented a greater risk of either the composite endpoint or all the single endpoints as compared to euthyroid patients. It is noteworthy that patients receiving adequate L-thyroxin replacement therapy (TRT) showed a significant reduction of composite or single endpoints while, those with inadequate TSH target value (≥5 mIU/L) maintained a risk profile similar to hypothyroid patients not receiving any TRT. Finally, in a nested group of patients randomly selected with a ratio of 1/3 from the two cohorts (euthyroid and hypothyroid patients at baseline) and evaluated in single blind by coronary angiogram at follow-up, the authors documented a significant worsening of target vessel diseases in hypothyroid as compared to euthyroid patients.