Amiodarone-Induced Thyrotoxicosis in Congenital HD
Amiodarone-Induced Thyrotoxicosis in Congenital HD
From a database collected in the Adult CHD Clinic at the Mayo Clinic, Rochester, Minnesota, we retrospectively identified the cohort of CHD patients treated with amiodarone for the period 1987–2009. The Adult CHD Clinic is an academic tertiary referral practice, and the database contained demographic information, diagnoses, and medication lists for all patients with CHD seen at the Mayo Clinic. We identified and studied all cases of thyrotoxicosis that occurred after a minimum of 3 months on amiodarone in patients without a prior history of hyperthyroidism or thyroidectomy. The data were collected retrospectively from the patients' electronic and paper records available at the Mayo Clinic and from the patients' local providers. Demographic data, AIT clinical presentation, diagnostic testing, treatment selection, response to treatment, duration of AIT episodes, and complications of AIT and its treatment were abstracted by two of the authors (M.N.S. and M.S.).
AIT was defined as suppressed thyroid-stimulating hormone (TSH) with elevated or normal thyroxine (T4) and/or triiodothyronine (T3) levels in the outpatient setting or as the same laboratory parameters in the inpatient setting with exclusion of sick euthyroid and/or drug effects (i.e., heparin, dopamine, glucocorticoids). We determined the type of AIT present according to whether or not criteria for AIT type 2 were met. These criteria were: (1) the absence of nodular goiter or presence of small diffuse goiter with negative thyroid antibodies; and (2) radioactive iodine (RAI) uptake <3% and low vascularity on thyroid Doppler flow (if only one investigation was available, it was accepted as sufficient). If one of the two criteria for AIT type 2 was not met, the AIT was defined as type 1. If there was not sufficient information to make this determination, the AIT was labeled as "undefined." AIT was considered to be "observed" if no intervention targeting pathophysiology was performed; beta-blockers were considered symptomatic therapy and did not change the observed status of a case. However, if an intervention targeting pathophysiology was performed after ≥1 week from the date the hyperthyroidism was diagnosed, that patient was considered to have been "initially observed." We considered the date of resolution of an episode to be: (1) the day of thyroidectomy; (2) the day the patient discontinued medical therapy if TSH was normal on subsequent testing; (3) midway between hyperthyroidism and normal TSH for those under observation; or (4) midway between hyperthyroidism and normal thyroid function by history if no other data were available and the above circumstances did not apply. Cyanotic CHD was defined as the presence of a congenital heart anomaly with a right-to-left shunt that either did not undergo surgical repair or had an incomplete or palliative repair prior to amiodarone therapy. We considered AIT complications to include recurrence of tachyarrhythmias, congestive heart failure, hospitalization for cardiovascular problems, weight loss, new edema development, or severe diarrhea.
Summary statistics for the continuous variables were expressed as the mean and SD or median with interquartile range (IQR), depending on the normalcy of the distribution. Categorical variables were summarized as percentages. Due to the small number of cases, either the Wilcoxon rank sum test (for continuous variables) or Fisher's exact test (for categorical variables) was used for all comparisons between groups. Commercially available software (JMP® software, version 8.0) was used for all statistical analyses. P values are reported with 3 significant digits for P <.1.
Methods
Database Used
From a database collected in the Adult CHD Clinic at the Mayo Clinic, Rochester, Minnesota, we retrospectively identified the cohort of CHD patients treated with amiodarone for the period 1987–2009. The Adult CHD Clinic is an academic tertiary referral practice, and the database contained demographic information, diagnoses, and medication lists for all patients with CHD seen at the Mayo Clinic. We identified and studied all cases of thyrotoxicosis that occurred after a minimum of 3 months on amiodarone in patients without a prior history of hyperthyroidism or thyroidectomy. The data were collected retrospectively from the patients' electronic and paper records available at the Mayo Clinic and from the patients' local providers. Demographic data, AIT clinical presentation, diagnostic testing, treatment selection, response to treatment, duration of AIT episodes, and complications of AIT and its treatment were abstracted by two of the authors (M.N.S. and M.S.).
Outcome Measures and Definitions
AIT was defined as suppressed thyroid-stimulating hormone (TSH) with elevated or normal thyroxine (T4) and/or triiodothyronine (T3) levels in the outpatient setting or as the same laboratory parameters in the inpatient setting with exclusion of sick euthyroid and/or drug effects (i.e., heparin, dopamine, glucocorticoids). We determined the type of AIT present according to whether or not criteria for AIT type 2 were met. These criteria were: (1) the absence of nodular goiter or presence of small diffuse goiter with negative thyroid antibodies; and (2) radioactive iodine (RAI) uptake <3% and low vascularity on thyroid Doppler flow (if only one investigation was available, it was accepted as sufficient). If one of the two criteria for AIT type 2 was not met, the AIT was defined as type 1. If there was not sufficient information to make this determination, the AIT was labeled as "undefined." AIT was considered to be "observed" if no intervention targeting pathophysiology was performed; beta-blockers were considered symptomatic therapy and did not change the observed status of a case. However, if an intervention targeting pathophysiology was performed after ≥1 week from the date the hyperthyroidism was diagnosed, that patient was considered to have been "initially observed." We considered the date of resolution of an episode to be: (1) the day of thyroidectomy; (2) the day the patient discontinued medical therapy if TSH was normal on subsequent testing; (3) midway between hyperthyroidism and normal TSH for those under observation; or (4) midway between hyperthyroidism and normal thyroid function by history if no other data were available and the above circumstances did not apply. Cyanotic CHD was defined as the presence of a congenital heart anomaly with a right-to-left shunt that either did not undergo surgical repair or had an incomplete or palliative repair prior to amiodarone therapy. We considered AIT complications to include recurrence of tachyarrhythmias, congestive heart failure, hospitalization for cardiovascular problems, weight loss, new edema development, or severe diarrhea.
Statistical Analysis
Summary statistics for the continuous variables were expressed as the mean and SD or median with interquartile range (IQR), depending on the normalcy of the distribution. Categorical variables were summarized as percentages. Due to the small number of cases, either the Wilcoxon rank sum test (for continuous variables) or Fisher's exact test (for categorical variables) was used for all comparisons between groups. Commercially available software (JMP® software, version 8.0) was used for all statistical analyses. P values are reported with 3 significant digits for P <.1.