Association between Subclinical Hypothyroidism and Cardiovascular Mortality in Patients Suffered from Heart Failure with Preserved Ejection Fraction

Background: Subclinical hypothyroidism (SCH) is underdiagnosed in patients (pts) with heart disease, however, there has been controversy surrounding whether it is a cardiovascular risk factor or not. To determine the prognostic significance of SCH in Heart Failure (HF) with Preserved Ejection Fraction (HFpEF) we followed a cohort of pts for 9 years. Methods: In this retrospective cohort, we queried our HF data base to identify HFpEF pts diagnosed in 2006 (registry initiation date) based on symptoms, BNP, and Echocardiogram with no history of hypothyroidism. Primary outcome was cardiovascular disease (CVD) mortality. Subjects divided into 2 groups based on presence or absence of SCH. SCH was defined as TSH of 5-10 mIU/L and normal free T4 in the absence of symptoms or hypothyroidism history. Results: We identified 249 eligible pts, of who 71 had SCH (28.5%). Mean age was 72.1 ± 13.4 years. Women constituted 56.6%. Follow up was for 8.75 ± 0.17 years. The CVD mortality rate for SCH pts was 29.6% versus 14.9 % for the others (P=0.008). The median survival time for SCH pts was significantly lower than pts with normal thyroid function, 99.9 ± 2.9 and 107.7 ± 1.5 months, respectively (P = 0.008 after adjustment forage, sex, hypertension, and other risk factors) (Figure 1). Conclusion: SCH is a significant predictor of mortality in HFpEF pts, despite controlling for some major risk factors. Therefore a mild asymptomatic elevation in TSH has a significant impact on outcome.