Routine thyroid function testing among hospitalized patients with ST segment elevated myocardial infarction (STEMI) can identify previously unknown subclinical hypothyroidism and provide a prognostic marker for both short- and long-term outcomes in these patients undergoing percutaneous coronary intervention (PCI), according to research published in the Journal of Clinical Medicine.

Researchers conducted a retrospective, single-center observational study to examine the potential relationship between unknown subclinical hypothyroidism and both in-hospital outcomes and short- and long-term all-cause mortality among patients with STEMI who underwent PCI.

Participants were admitted to the Tel-Aviv Sourasky Medical Center between October 2007 and August 2017 with a diagnosis of acute STEMI. Those with unavailable data on thyroid-stimulating hormone and free thyroxine fraction levels were excluded, as well as those treated with amiodarone and those with a documented history of either hypo- or hyperthyroidism.

In total, 2234 patients were admitted during the study period; 1593 patients (median age, 61 years; 82% males) were eligible for inclusion in the final analysis. Patients with subclinical hypothyroidism were more likely to develop acute kidney injury and to have lower left ventricular ejection fraction (LVEF) levels, while new-onset atrial fibrillation development during hospitalization was similar between both groups.


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Within 30 days of hospital admission, 9% of patients with subclinical hypothyroidism died compared with 3% of patients without (P =.02). Results of a univariate logistic regression analysis demonstrated that having subclinical hypothyroidism, being age 60 years or older, and demonstrating an LVEF of 40% or greater were associated with short-term mortality. Similarly, a multivariate binary regression model adjusted for baseline variables showed that subclinical hypothyroidism was independently associated with short-term mortality (odds ratio, 3.2; 95% CI, 1.2-8.6; P =.02). Being older than 60 years of age, having an LVEF of 40 or less, and having a family history of coronary artery disease were also significantly associated with short-term mortality.

Over a median follow-up period of 4.2 years (interquartile range, 2.2-6.5 years), 24% and 13% of patients with and without subclinical hypothyroidism died, respectively (P <.001). Age 60 years or older, hypertension, previous MI, and LVEF of 40% or less were all factors associated with long-term mortality. Results of a multivariable Cox regression model indicated that subclinical hypothyroidism was independently associated with long-term mortality after STEMI (hazard ratio, 2.2; 95% CI, 1.2-3.8; P =.007).

Study limitations include the single-center, a nonrandomized design, the small number of patients with subclinical hypothyroidism, and the small number of events within that patient population. There is a possibility of residual confounding by other nonmeasured factors, and because the study included only those patients undergoing primary PCI, the results cannot be generalized.

“Unknown [subclinical hypothyroidism] is not uncommon among STEMI patients treated with PCI, and it may serve as a prognostic marker for poor in-hospital outcomes and elevated short- and long-term mortality,” the researchers concluded. “Thyroid tests are not routinely performed during hospitalization, and the current findings indicate that the information obtained from them…is highly relevant to the planned performance of PCI.”“[P]rospective studies are warranted to clarify the optimal management for STEMI patents with [subclinical hypothyroidism] who are planned for PCI,” they added.

Reference

Izkhakov E, Zahler D, Rozenfeld K-L, et al. Unknown subclinical hypothyroidism and in-hospital outcomes and short- and long-term all-cause mortality among ST segment elevation myocardial infarction patients undergoing percutaneous coronary intervention. Published online November 26, 2020. J Clin Med. doi: 10.3390/jcm9123829