Why STEMI patients undergoing PCI should be tested for subclinical hypothyroidism

Subclinical hypothyroidism (SCH) is associated with worse in-hospital outcomes among STEMI patients undergoing percutaneous coronary intervention (PCI), according to a new analysis published in the Journal of Clinical Medicine. For this reason, the authors recommended evaluating the thyroid function of all STEMI patients before PCI takes place.

The research team behind the study explored data from more than 1,500 STEMI patients who were treated with primary PCI from October 2007 to August 2017 at a single facility. The median patient age was 61 years old, 82% were male and 4.2% demonstrated SCH when they were first admitted to the cardiac intensive care unit.

Patients with SCH, the authors added, were more likely to be smokers and to be men.

Overall, 9% of patients with SCH died within 30 days of admission. That figure was 3% for patients without SCH. SCH was associated with short-term modality, a regression analysis revealed, as was being over the age of 60 and left ventricular ejection fraction (LVEF) levels of 40% or less.  

Looking at long-term mortality, the team found that 24% of patients with SCH died over a median follow-up period of more than four years. That figure was 13% for patients without SCH. SCH, being over the age of 60, hypertension, a previous myocardial infarction and LVEF levels of 40% or less were all associated with long-term mortality.

“Potential mechanisms for these findings in SCH patients include oxidative stress in mitochondria due to increased plasma inflammatory markers, insulin resistance, activation of thrombosis and hypercoagulability, endothelial dysfunction, delayed diastolic filling, impaired left ventricular systolic function, and increased vascular resistance,” wrote lead author Elena Izkhakov, MD, Tel Aviv Sourasky Medical Center in Israel, and colleagues. “In the current study, SCH was associated with an increased risk of acute kidney injury compared to euthyroid patients. These findings concur with various associations that have been documented between thyroid dysfunction and impaired kidney function, including in the setting of cardiovascular disease.”

While some studies have found that hormone replacement therapy can help patients with SCH, the topic remains “controversial.” In fact, recent guidelines—representing the work of an international team of researchers—found that there is not enough of a benefit to recommend the administration thyroid hormones to adult patients with SCH.

Izkhakov et al. concluded their study by suggesting healthcare providers start testing all STEMI patients for unknown SCH to help them make informed care decisions.

"Thyroid function tests are not routinely performed during hospitalization, and the current findings indicate that the information obtained from them on in-hospital outcomes and short- and long-term mortality is highly relevant to the planned performance of PCI,” the authors wrote. “Therefore, routine testing of thyroid function before performing PCI should be considered, and prospective studies are warranted to clarify the optimal management for STEMI patients with SCH who are planned for PCI.”

Read the full analysis here.