What is the clinical evidence from this study?

Study design: Cohort. Population: Paroxysmal atrial fibrillation (n=244). Intervention: High-normal free thyroxine (FT4) level (highest quartile) vs. Lowest free thyroxine (FT4) quartile. Primary outcome: Recurrence of atrial fibrillation (HR 3.31, 95% CI 1.45-7.54, p=0.004).

January 1, 2010Open Access

High-Normal Thyroid Function and Risk of Recurrence of Atrial Fibrillation After Catheter Ablation

Key Result

Patients in the highest quartile of normal free thyroxine levels had a significantly increased risk of atrial fibrillation recurrence after catheter ablation compared to the lowest quartile (HR 3.31).

Study Design

Type

Cohort (n=244)

Multicenter

Structured PICO

Does a high-normal level of FT4 increase the risk of AF recurrence after catheter ablation in euthyroid patients with paroxysmal AF?

Population

244 patients (mean age 56, 27.5% female) with paroxysmal atrial fibrillation undergoing catheter ablation, free of prior or current thyroid dysfunction, followed for a mean of 416 days.

Exposure

High-normal serum free thyroxine (FT4) level (highest quartile, >18.4 pmol/L)

Comparator

Lower serum free thyroxine (FT4) levels (lowest quartile, <13.4 pmol/L)

Outcome

Recurrence of atrial fibrillation (defined as the occurrence of confirmed atrial tachyarrhythmia documented by ECG or Holter recordings beyond 3 months after the index catheter ablation while off antiarrhythmic medication)hard clinical

High-normal thyroid function (FT4) is an independent predictor of atrial fibrillation recurrence following catheter ablation in euthyroid patients.

Main Result

Hazard Ratio: 3.31 (95% CI 1.45–7.54)

Absolute Event Rate: 38.7% vs 14.8%

p-value: p=0.004

Limitations

Exact mechanism of higher AF recurrence rates remains to be investigated
Whether elevated FT4 increases pulmonary vein reconnection was not identified
Data on non-pulmonary vein foci were not available
Potential underestimation of asymptomatic AF recurrence due to reliance on symptoms, ECG, and Holter
Small sample size of approximately 60 patients per quartile

Abstract

BACKGROUND: It has been shown that the concentration of serum free thyroxine (FT(4)) is independently associated with atrial fibrillation (AF), even in euthyroid persons. This study investigated the effect of a high-normal level of FT(4) on recurrence after catheter ablation of AF. METHODS AND RESULTS: The 244 consecutive patients with paroxysmal AF and who underwent circumferential pulmonary vein isolation (PVI) were prospectively enrolled. Exclusion criteria included prior or current thyroid dysfunction on admission, amiodarone medication for 3 months before admission. After a mean follow-up of 416+/-204 (91-856) days, the recurrence rates were 14.8%, 23.0%, 33.3%, 38.7% from the lowest FT(4) quartile to the highest FT(4) quartile, respectively (P=0.016). After adjustment for age, sex, left atrial diameter, and PVI, there was an increased risk of recurrence in the subjects with the highest FT(4) quartile compared with those with the lowest quartile (hazard ratio 3.31, 95% confidence interval 1.45-7.54, P=0.004). As a continuous variable, FT(4) was also an independent predictor of recurrence (hazard ratio 1.10, 95% confidence interval 1.02-1.18, P=0.016). CONCLUSIONS: Patients with high-normal thyroid function were at an increased risk of AF recurrence after catheter ablation.

KI fragen

Bookmark

View Full Paper