Prevalence and Impact of Subclinical Thyroid Dysfunction on Mortality among Patients Presenting with Cardiovascular Events

Abstract

Objective. This study aims to determine the prevalence of subclinical thyroid dysfunction among cardiac patients at the Philippine General Hospital, and its association with mortality.Methodology.163 adult cardiac patients were screened for subclinical thyroid dysfunction, [subclinical hyperthyroidism (SCT), subclinical hypothyroidism (SCHO), non-thyroidal illness syndrome (NTIS)]. Demographic and clinical characteristics were analyzed using ANOVA and Fisher's exact test. Outcome considered were hospital duration, need for mechanical ventilation, inotropic support and mortality. Crude association between subclinical thyroid dysfunction and outcomes was evaluated using relative risk.Results. Prevalence of subclinical thyroid dysfunction was 32.5% (5.5% SCT, 5.5% SCHO, and 21.5% NTIS). The risk of necessitating mechanical ventilation was about twofold higher in subclinical thyroid dysfunction compared to euthyroid patients (RR=2.64), and was highest in SCHO (RR=3.71). The risk of inotropic support was about twofold higher (RR=2.70) in SCHO compared to euthyroid patients. Overall death rate was higher in subclinical thyroid dysfunction (RR=1.86), and highest in SCHO (RR=2.47) compared to euthyroid patients. Conclusion.There is a significant prevalence of subclinical thyroid dysfunction among hospitalized patients with cardiac disease at 32.5%. Cardiovascular risk factors are not statistically significant. We observed a trend of increased risk of requiring mechanical ventilation, inotropes and overall mortality in SCHO.