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

Mechanisms and Management of Thyroid Disease and Atrial Fibrillation: Impact of Atrial Electrical Remodeling and Cardiac Fibrosis

Atrial fibrillation (AF) is the most common cardiac arrhythmia associated with increased cardiovascular morbidity and mortality. The pathophysiology of AF is characterized by electrical and structural remodeling occurring in the atrial myocardium. As a source of production of various hormones such as angiotensin-2, calcitonin, and atrial natriuretic peptide, the atria are a target for endocrine regulation. Studies have shown that disorders associated with endocrine dysregulation are potential underlying causes of AF. The thyroid gland is an endocrine organ that secretes three hormones: triiodothyronine (T3), thyroxine (T4) and calcitonin. Thyroid dysregulation affects the cardiovascular system. Although there is a well-established relationship between thyroid disease (especially hyperthyroidism) and AF, the underlying biochemical mechanisms leading to atrial fibrosis and atrial arrhythmias are poorly understood in thyrotoxicosis. Various animal models and cellular studies demonstrated that thyroid hormones are involved in promoting AF substrate. This review explores the recent clinical and experimental evidence of the association between thyroid disease and AF. We highlight the current knowledge on the potential mechanisms underlying the pathophysiological impact of thyroid hormones T3 and T4 dysregulation, in the development of the atrial arrhythmogenic substrate. Finally, we review the available therapeutic strategies to treat AF in the context of thyroid disease.

The Association Between Subclinical Thyroid Dysfunction and Recurrence of Atrial Fibrillation After Catheter Ablation

Objective

The aim of this study was to evaluate the association between subclinical thyroid dysfunction and the recurrence of atrial fibrillation (AF) after radiofrequency catheter ablation (RFCA).

Methods

We examined the association between subclinical thyroid dysfunction and the recurrence of AF at a large university-affiliated cardiac arrhythmia center in China. Data were collected from consecutive patients who underwent RFCA for AF, excluding those with a history of hypothyroidism, hyperthyroidism, or ongoing medical treatment for hypothyroidism or hyperthyroidism, biochemically defined overt thyroid disease, and long-term use of amiodarone before admission. The primary end point was the recurrence of AF in a time-to-event analysis. We compared outcomes in patients who had subclinical hyperthyroidism or hypothyroidism with those who had euthyroid state, using a multivariable Cox model with inverse probability weighting and propensity score matching.

Results

In all, 93 patients were excluded from 435 consecutive patients who underwent RFCA for AF. Of the remaining 342 patients for the analysis, the prevalence of subclinical hyperthyroidism and subclinical hypothyroidism were 26 (7.6%) and 41 (12.0%), respectively; during a median follow-up of 489 days, 91 patients (26.6%) developed a primary end point event. In the main analysis of the multivariable Cox model, only subclinical hyperthyroidism [hazard ratio: 3.07, 95% confidence interval (CI): 1.54–6.14] was associated with an increased risk of end point event after adjusting for potential confounders. However, the association between subclinical hypothyroidism and the end point event was not significant (hazard ratio: 0.66, 95% CI: 0.31–1.43). Results were consistent either in multiple sensitivity analyses or across all subgroups of analysis. Compared with individuals with free triiodothyronine (fT3) in the lowest quintile, those with fT3 in the highest quintile had an HR of 2.23 (95% CI: 1.16–4.28) for recurrence of AF. With the increase of thyroid-stimulating hormone (TSH), a reduction in the risk of recurrence of AF was detected in the adjusted model, and the hazard ratio (HR) per standard deviation (SD) increase was 0.82 (95% CI: 0.68–0.98).

Conclusion

In this retrospective cohort study involving patients who underwent RFCA for AF, patients with subclinical hyperthyroidism were associated with a markedly higher prevalence of recurrence of AF, whereas patients with subclinical hypothyroidism had a similar recurrence rate of AF compared to those with the euthyroid state.

Higher FT4 level within the normal range predicts the outcome of cryoballoon ablation in paroxysmal atrial fibrillation patients without structural heart disease

Background

Accumulated evidence has indicated that a high‐normal FT4 level is an independent risk factor for the clinical progression of AF. However, the association between elevated FT4 concentration within the normal range and AF recurrence after cryoballoon ablation in China is unknown.

Methods

This retrospective and observational study included 453 AF patients who underwent cryoballoon ablation from January 2016 to August 2018. Patients were classified into quartiles based on preprocedural serum FT4 concentration. The clinical characteristics of the patients and the long‐term rate of AF recurrence after ablation were assessed.

Results

After a mean follow‐up period of 17.4 ± 9.0 months, 91 (20.1%) patients suffered from AF recurrence. The AF recurrence rate by FT4 quartile was 17.7%, 19.0%, 21.4%, and 22.3% for participants with FT4 in quartile 1, 2, 3, and 4, respectively (p < .001). On multivariate Cox regression, FT4 concentration (HR: 1.187, 95% CI: 1.093–1.290, p < .001) and left atrial diameter (HR: 1.052, 95% CI: 1.014–1.092, p = .007) were significant predictors of AF recurrence. When stratifying for AF type, the rate of postoperative recurrence was independently increased as FT4 concentration increased in paroxysmal AF, but not in persistent AF (p < .001 in paroxysmal AF and p = .977 in persistent AF).

Conclusion

Higher FT4 level within the normal range predicted the outcome of cryoballoon ablation in Chinese paroxysmal AF patients without structural heart disease.

High-Normal Thyroid Function and Recurrence of Atrial Fibrillation after Catheter Ablation: A Prospective Observational Study

BACKGROUND

Thyroid function is increasingly recognized as an important modifiable factor for atrial fibrillation (AF); however, it is unclear if the changes in thyroid hormones, even within the normal range, are associated with AF recurrence after catheter ablation.

METHODS

Consecutive paroxysmal AF patients who underwent catheter ablation were enrolled. Patients with abnormal thyroid hormones or previous thyroid illnesses were excluded. Patients were followed for 12 months or until they presented with the first episode of atrial tachyarrhythmia after a blanking period.

RESULTS

The study included 448 patients with a mean age of 61 (14) years, and 46% were women. After a 1-year follow-up, 104 (23.2%) patients experienced atrial tachyarrhythmia recurrences after an ablation procedure. Recurrence was significantly different among quartile groups of thyroid function, with highest FT4 and FT3 levels associated with the greatest risk of recurrence (p < 0.001 and p = 0.024, respectively). FT4 and FT3 levels were independent predictors of atrial tachyarrhythmia recurrence (hazard ratio 1.07 per 1 pmol/L increase in FT4, 95% confidence interval [CI] 1.01-1.15, p = 0.036 and 1.31 per 1 pmol/L increase in FT3, 95% CI 1.01-1.71, p = 0.032).

CONCLUSIONS

High-normal FT3 and FT4 levels are associated with AF recurrence after catheter ablation in this Chinese population. Attention to thyroid hormones could be valuable to assist in the management of AF.

Pro-Arrhythmic Signaling of Thyroid Hormones and Its Relevance in Subclinical Hyperthyroidism

A perennial task is to prevent the occurrence and/or recurrence of most frequent or life-threatening cardiac arrhythmias such as atrial fibrillation (AF) and ventricular fibrillation (VF). VF may be lethal in cases without an implantable cardioverter defibrillator or with failure of this device. Incidences of AF, even the asymptomatic ones, jeopardize the patient's life due to its complication, notably the high risk of embolic stroke. Therefore, there has been a growing interest in subclinical AF screening and searching for novel electrophysiological and molecular markers. Considering the worldwide increase in cases of thyroid dysfunction and diseases, including thyroid carcinoma, we aimed to explore the implication of thyroid hormones in pro-arrhythmic signaling in the pathophysiological setting. The present review provides updated information about the impact of altered thyroid status on both the occurrence and recurrence of cardiac arrhythmias, predominantly AF. Moreover, it emphasizes the importance of both thyroid status monitoring and AF screening in the general population, as well as in patients with thyroid dysfunction and malignancies. Real-world data on early AF identification in relation to thyroid function are scarce. Even though symptomatic AF is rare in patients with thyroid malignancies, who are under thyroid suppressive therapy, clinicians should be aware of potential interaction with asymptomatic AF. It may prevent adverse consequences and improve the quality of life. This issue may be challenging for an updated registry of AF in clinical practice. Thyroid hormones should be considered a biomarker for cardiac arrhythmias screening and their tailored management because of their multifaceted cellular actions.

Association of peak atrial longitudinal strain with atrial fibrillation recurrence in patients with chronic lung diseases following radiofrequency ablation

BACKGROUND

Strain was shown associated with atrial fibrillation (AF) recurrence after radiofrequency ablation (RFA), but data on AF patients complicated with chronic lung diseases (CLD) were rare.

AIM

This study was designed to evaluate the relationship of baseline atrial function with AF recurrence in these patients using speckle-tracking echocardiography.

METHODS

Average strain values (median: 2 days before RFA) were calculated for 87 AF patients (Mean age: 61.91 years, male: 71.26%) with CLD undergoing RFA from 2013 to 2014. Of these patients, 25 (28.74%) experienced AF recurrence during a mean follow up of 10.3 months.

RESULTS

Peak right atrial longitudinal strain (R-PALS) was associated with peak left atrial longitudinal strain (L-PALS, Standardised β = 0.45, P < 0.001) in multivariate linear regression. Multivariate Cox regression analysis showed R-PALS was associated with AF recurrence (hazard ratio, 0.86; 95% confidence interval (CI), 0.78-0.96, P = 0.005) in CLD. Patients with R-PALS ≥14.69% had higher AF free rate compared with R-PALS<14.69% using Kaplan-Meier analysis (log-rank, P < 0.001). R-PALS had similar C-index compared to L-PALS (difference: 0.03, 95%CI: -0.06-0.12, P = 0.53) and combined R-PALS and L-PALS (difference: 0.005, 95%CI: -0.04-0.05, P = 0.84) associated with AF recurrence in CLD.

CONCLUSION

R-PALS, L-PALS and combined R-PALS and L-PALS are important factors associated with AF recurrence following RFA in patients with CLD.

U-shaped association between serum free triiodothyronine and recurrence of atrial fibrillation after catheter ablation

PURPOSE

Thyroid dysfunction affects the outcomes of atrial fibrillation (AF) catheter ablation. However, it remains unclear if the variations in thyroid function, especially in the triiodothyronine levels, are associated with AF recurrence in euthyroid subjects. This study investigated the associations of thyroid hormone levels with arrhythmia recurrence after AF catheter ablation in euthyroid patients.

METHODS

A total of 1115 consecutive AF patients who underwent catheter ablation were prospectively enrolled and had their thyroid function measured prior to the procedure. The serum free triiodothyronine (FT₃), free tetraiodothyronine (FT₄), and thyroid-stimulating hormone (TSH) levels were assessed as predictors of recurrence and were adjusted for potential confounders. The subjects were divided into five quintile groups according to the FT₃, FT₄, and TSH levels, respectively.

RESULTS

After a median follow-up of 723 days (interquartile range, 180-1070), 47.2% of patients experienced recurrence. After multivariate adjustment, subject in the lowest and highest FT₃ quintiles showed increased risk of recurrence (hazard ratio [HR] 1.60, 95% confidence interval [CI] 1.26-2.03, P < 0.01, and HR 1.47, 95% CI 1.16-1.87, P < 0.01, respectively), compared to the median quintile of FT₃ levels. Regarding the FT₄ level, the highest quintile group showed a higher risk of recurrence (HR 1.27, 95% CI 1.01-1.60, P = 0.04). The TSH levels were not associated with AF recurrence.

CONCLUSIONS

Both high and low FT₃ levels were associated with AF recurrence after catheter ablation. High-normal FT₄ levels were also related to AF recurrence; however, no association was found between normal TSH levels and AF recurrence.

Prevalence of right atrial non-pulmonary vein triggers in atrial fibrillation patients treated with thyroid hormone replacement therapy

BACKGROUND

Thyroid hormone (TH) is known to enhance arrhythmogenicity, and high-normal thyroid function is related with an increased recurrence of atrial fibrillation (AF) after catheter ablation. However, the impact of thyroid hormone replacement (THR) on AF ablation is not well known.

METHODS

This study evaluated 1163 consecutive paroxysmal AF patients [160 (14%) on THR and 1003 (86%) without THR] undergoing their first catheter ablation. A total of 146 patients on THR and 146 controls were generated by propensity matching, based on calculated risk factor scores, using a logistic model (age, sex, body mass index, and left atrium size). The presence of non-pulmonary vein (PV) triggers was disclosed by a high-dose isoproterenol challenge (up to 30 μg/min) after PV isolation.

RESULTS

Clinical characteristics were not different between the groups. When compared to the control, non-PV triggers were significantly greater in the THR patients [112 (77%) vs. 47 (32%), P < 0.001], and most frequently originated from the right atrium (95 vs. 56%, P < 0.001). Other sources of non-PV triggers were the interatrial septum (25 vs. 11%, P = 0.002), coronary sinus (70 vs. 52%, P = 0.01), left atrial appendage (47 vs. 34%, P = 0.03), crista terminalis/superior vena cava (11 vs. 8%, P = 0.43), and mitral valve annulus (7 vs. 5%, P = 0.45) (THR vs. control), respectively. After mean follow-up of 14.7 ± 5.2 months, success rate was lower in patients on THR therapy [94 (64.4%)] compared to patients not receiving THR therapy [110 (75.3%), log-rank test value = 0.04].

CONCLUSIONS

Right atrial non-PV triggers were more prevalent in AF patients treated with THR. Elimination of non-PV triggers provided better arrhythmia-free survival in the non-THR group.

Impact of Free Thyroxine on the Outcomes of Left Atrial Ablation Procedures

The prevalence of atrial fibrillation (AF) is increased in hyperthyroidism. The degree to which thyroid hormones affect the outcomes of left atrial (LA) ablation is still unclear. From September 2010 to September 2013, 1,095 patients who underwent LA ablation (59.7% paroxysmal AF, 32.3% persistent AF, and 8.0% LA tachycardia) had their serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels measured in the 48 hours before the procedure. Patients were followed until they presented the first AF relapse after a blanking period of 3 months. TSH and FT4 were assessed as predictors of arrhythmia relapse and were adjusted for possible confounders. During a mean follow-up of 12.5 ± 7.9 months, 28.9% of patients presented an atrial arrhythmia relapse. TSH was not a predictor of relapse. In contrast, after adjustment, FT4 (median = 11.8 ng/L and interquartile range 10.6 to 14.6 ng/L) remained a predictor of relapse with 15% increase per quartile (hazard ratio 1.15, 95% confidence interval 1.03 to 1.29, p = 0.014). In conclusion, FT4 levels influence the success rate of LA ablation procedures, even when in the normal range.

QTc Interval Prolongation Predicts Arrhythmia Recurrence After Catheter Ablation of Atrial Fibrillation in Patients With Hypertrophic Cardiomyopathy

BACKGROUND

In hypertrophic cardiomyopathy (HCM) patients complicated with atrial fibrillation (AF), catheter ablation has been recommended as a treatment option. Meanwhile, prolongation of QTc interval has been linked to an increased AF incidence in the general population and to poor outcomes in HCM patients. However, whether QTc prolongation predicts arrhythmia recurrence after AF ablation in the HCM population remains unknown.

METHODS AND RESULTS

Thirty-nine HCM patients undergoing primary AF ablation were enrolled. The ablation strategy included bilateral pulmonary vein isolation (PVI) for paroxysmal AF (n=27) and PVI plus left atrial roof, mitral isthmus and tricuspid isthmus linear ablations for persistent AF (n=12). Pre-procedural QTc was corrected by using the Bazett's formula. At a 14.8-month follow up, 23 patients experienced atrial tachyarrhythmia recurrence. Recurrent patients had longer QTc than non-recurrent patients (461.0±28.8 ms vs. 434.3±18.2 ms, P=0.002). QTc and left atrial diameter (LAD) were independent predictors of recurrence. The cut-off value of QTc 448 ms predicted arrhythmia recurrence with a sensitivity of 73.9% and a specificity of 81.2%. A combination of LAD and QTc (global chi-squared=13.209) was better than LAD alone (global chi-squared=6.888) or QTc alone (global chi-squared=8.977) in predicting arrhythmia recurrence after AF ablation in HCM patients.

CONCLUSIONS

QTc prolongation is an independent predictor of arrhythmia recurrence in HCM patients undergoing AF ablation, and might be useful for identifying those patients likely to have a better outcome following the procedure.

Prolonged PR interval and risk of recurrence of atrial fibrillation after catheter ablation

It has been demonstrated that a prolonged PR interval is associated with an increased risk of AF. However, the impact of a prolonged PR interval on recurrence of paroxysmal atrial fibrillation (AF) after catheter ablation is not clear. A total of 112 patients with a prolonged PR interval (PR > 200 ms) (PPR group) and 112 age- and gender-matched control patients (on a 1:1 basis) with a normal PR interval (NPR group) were included in this study. AF recurrence was defined as the occurrence of confirmed atrial tachyarrhythmia lasting more than 30 seconds beyond 3 months after catheter ablation in the absence of any antiarrhythmic treatment. During a mean follow-up period of 10.9 ± 5.5 months (range, 3-18 months), 61 patients (27.2%) developed recurrence of AF. The recurrence rate was higher in the PPR group than in the NPR group (33.9% versus 20.5%, respectively; P = 0.018). Cox regression analysis with adjustment for age, body mass index, valvular heart disease, left atrial diameter, and pulmonary vein isolation identified only a prolonged PR interval as an independent predictor of recurrence of AF (hazard ratio, 1.81; 95% confidence interval, 1.07-3.05; P = 0.027). Patients with a prolonged PR interval were at an increased risk of AF recurrence after catheter ablation.