Endocrine Abstracts (2006) 11 OC59

Tri-iodothyronine improves haemodynamic performance and is associated with improved myocardial protection post on-pump coronary artery bypass grafting

AM Ranasinghe1, DW Quinn1, TR Graham1, BE Keogh1, CJ Mascaro1, SJ Rooney1, IC Wilson1, D Pagano1, JA Franklyn2 & RS Bonser1


1University Hospital Birmingham NHS Trust, Birmingham, United Kingdom; 2University of Birmingham, Division of Medical Sciences, Birmingham, United Kingdom.


Objectives: Tri-iodothyronine (T3) can improve cardiovascular performance following cardiac surgery. Its effects on myocardial protection are unknown.

Methods: We performed two consecutive randomised double-blind placebo-controlled trials (identical management protocols) on patients undergoing first time isolated elective or urgent on-pump coronary artery bypass graft surgery (CABG). Between January 2000 and September 2004, 440 patients were recruited and randomised. Within this study population 160 patients were randomised to receive placebo (5% dextrose) and 63 to, T3 therapy (0.8 μg.kg−1 bolus, followed by 0.113 μg.kg−1.hr−1) (n=63). T3/placebo therapy was administered for a 6-hour period from removal of aortic cross clamp (AXC). Serial haemodynamic measurements were performed at baseline and up to 12 hours following removal of AXC along with cardiac troponin I (CTnI) levels.

Results: Results are summarised in the accompanying table (P values correspond to placebo compared with treatment group). Repeated measures ANOVA demonstrated that T3 therapy increased cardiac index (CI) versus placebo between 6 and 12 hours after AXC removal (P=0.01). CTnI release was significantly lower in all treatment groups at 6 hours following removal of AXC.

PlaceboT3
Baseline CI (l.min−1m−2)2.172.28 (P=0.157)
6 h post AXC CI (l.min−1m−2)2.72.86 (P=0.08)
12 h post AXC CI (l.min−1m−2)2.753.02 (P=0.002)
6 h CTnI (ng. ml−1)8.664.56 (P< 0.001)
12 h CTnI (ng.ml−1)6.663.37 (P=0.001)

Conclusions: Treatment with T3 improves haemodynamic performance and results in reduced CTnI release in patients undergoing on-pump CABG surgery. Precise mechanisms for these effects still remain to be fully elucidated.