The effect of cardiac catheterization on thyroid functions in infants with congenital heart diseases: a prospective observational study.

Unlabelled: This study aims to determine the incidence, clinical course, and risk factors of hypothyroidism following cardiac catheter (CC) in infants with congenital heart diseases (CHD). This prospective study involved 115 patients with CHD, all aged 3 years or younger, who underwent CC, as well as 100 healthy age- and sex-matched controls. Baseline thyroid function tests (TFTs) were conducted for both the patients and controls. In the CHD cohort, TFTs were reassessed 4 weeks after the CC, and for those with abnormal TFT values at this time, the tests were repeated after 2 weeks. Levothyroxine was started for patients with persistent abnormal TFTs, at 4 weeks and 6 weeks assessments after CC. Four weeks after CC, 12% of the studied group exhibited hypothyroidism. Univariate analysis identified significant predictors of hypothyroidism following CC: aortic stenosis (RR = 10.0 (1.49-66.99), P = 0.018), duration of fluoroscopy during CC (RR = 2.12 (0.99-4.26), P = 0.05), and total iodinated contrast media (iCM) during CC (RR = 2.5 (1.35-3.55), P = 0.019). Multivariate analysis indicated that iCM dose was the sole significant predictor of developing hypothyroidism (RR = 2.10 (1.01-3.23), P = 0.04). ROC curve analysis showed that the cut-off point of iCM dose for prediction of hypothyroidism evolution is 8.7 gm/kg, (sensitivity: 83%, specificity: 65%), while the cut-off point of fluoroscopy duration which predicts the development of hypothyroidism is 24 min (sensitivity: 83%, specificity: 66%). Acquired hypothyroidism after CC persisted in 4% of this cohort for 6 months.

Conclusion: Higher doses of iCM and longer duration of fluoroscope during CC are risk factors for the evolution of hypothyroidism post-CC. We recommend assessing thyroid profile 4 weeks after CC, particularly in patients who received an iCM dose greater than 8.7 gm/kg and/or exposed to fluoroscopy for more than 24 min.

What Is Known: • The use of excess iodine leads to transient inhibition of thyroid hormones biosynthesis via the Wolff-Chaikoff effect. • Infants with congenital heart diseases (CHD) are more prone to hypothyroidism due to higher frequency of abnormal thyroid morphology and routine exposure to supraphysiological doses of iodine.

What Is New: • Exposure to a total dose of iodinated contrast media more than 8.7 gm/kg and a fluoroscopy duration more than 24 min during cardiac catheter are risk factors for the evolution of thyroid hypofunction following cardiac catheter.