Oral Triiodothyronine Supplementation Decreases Low Cardiac Output Syndrome After Pediatric Cardiac Surgery

Abstract

The oral triiodothyronine for infants and children undergoing cardiopulmonary bypass (OTICC) trial showed that Triiodothyronine (T3) supplementation improved hemodynamic and clinical outcome parameters. We tested the validity of low cardiac output syndrome (LCOS), derived using clinical parameters and laboratory data, by comparing the LCOS diagnosis with objective parameters commonly measured in a cardiac intensive care unit (CCU) setting. OTICC, a randomized, placebo-controlled trial included children younger than 3 years with an Aristotle score between 6 and 9. We used the existing trial data set to compare the LCOS diagnosis with echocardiographic hemodynamic parameters. Additionally, we determined if LCOS, prospectively assigned during a clinical trial, served as an early predictor of clinical outcomes. All LCOS subjects at 6 and 12 h after cross-clamp release later showed significantly lower pulse pressure, stroke volume and cardiac output, and higher systemic vascular resistance. These LCOS patients also had significantly longer time to extubation (TTE) and higher mortality rate. LCOS incidence was significantly lower in the T3 treatment group [n = 86 vs. 66, respectively, p < 0.001; OR (95% CI) 0.43 (0.36-0.52)] particularly at 6 h. Also, LCOS patients in the placebo group had significantly lower FT3 serum levels over time. These analyses confirm that early clinically defined LCOS successfully predicts cardiac dysfunction determined later by objective hemodynamic echocardiographic parameters. Furthermore, early LCOS significantly impacts TTE and mortality. Finally, the data support prior clinical trial data, showing that oral T3 supplementation decreases early LCOS in concordance with reducing TTE.

Keywords: Cardiopulmonary bypass; Congenital heart disease; Euthyroid sick syndrome; Low cardiac output syndrome; Thyroid hormone replacement.