In this study, we sought to evaluate the effect of single-dose intravenous dexamethasone on AF recurrence following RF catheter ablation. Patients in our study received 4 mg or 8 mg of dexamethasone at the time of AF ablation by anesthesia and were compared to controls which did not receive any intravenous steroids in a “blinded fashion” to the operator. Our main findings were that: 1) there was no significant difference in rates of documented AF recurrence, DCCV, or prescription of antiarrhythmic agents at 3 months or 1 year follow-up. These results were suggestive of the use of single-dose intravenous dexamethasone not being associated with early and late AF recurrence and thus of utility for PONV without affecting outcomes.
In a study of Paroxysmal AF patients, those randomized to colchicine experienced a significant reduction in early and late AF recurrence compared to those who received placebo3,4. The serum concentration of CRP and interleukin 6 were also significantly reduced after 4 days of treatment in the colchicine group, suggesting decreased systemic inflammation leading to reduced AF recurrence3. Single dose intravenous corticosteroids administered at the time of ablation did not reduce post-ablation recurrence after AF6,7. Notably in both studies methylprednisolone and hydrocortisone were administered at the time of ablation6,7.
The findings of our study are consistent with the findings of previous studies involving single-dose intravenous steroids at the time of catheter ablation. A prior study has shown that in 89 patients who received a single bolus injection of 100 mg hydrocortisone within 30 minutes of completing the pulmonary vein isolation procedure, there was no significant difference in immediate, early, and late AF recurrence rates6. A similar result was found when comparing the effects of low-dose intravenous steroids with 100 mg hydrocortisone and moderate-dose steroids with 125 mg methylprednisolone in a prior study7. It was felt that moderate-dose steroids were thought to decrease post-ablation inflammation, evidenced by a significant reduction in maximum body temperature and serum C-reactive protein levels compared to the low-dose steroid and control groups. However, there was no significant difference in immediate, early, or midterm atrial fibrillation recurrence7.
Catheter ablation using radiofrequency energy involves the delivery of high frequency alternating electrical current, which heats the incident tissue underlying the catheter tip in a resistive or ohmic manner11. Following catheter ablation, there are both localized and systemic inflammatory responses, as well as a continued myocardial injury which results in the maturation of the newly formed lesions1. From a histological perspective, in vivo ablation studies in animal models have demonstrated infiltration of necrotic myocardium by lymphocytes and macrophages, ultimately resulting in the replacement of coagulative necrotic myocardium with fibrosis12. This post-ablation inflammatory response typically occurs within the first 3 days after ablation and is evidenced systemically by elevation in serum C-reactive protein (CRP) levels1.
AF recurrence following catheter ablation is thought to be in part mediated by systemic inflammation. Interestingly, patients without early recurrence of AF within the first month have higher CRP levels compared to individuals that experienced early recurrence13. This suggests that increased systemic inflammation may somehow be protective against early AF recurrence. One possible explanation for this is that the degree of systemic inflammation is indicative of or proportional to the degree of local inflammation at the site of myocardial lesions. As such, a heightened local inflammatory response may lead to a more robust lymphocytic and macrophagic infiltration, yielding more fibrosis and durable lesion formation. Interestingly, there was no difference in CRP levels between individuals with and without late recurrence, suggesting that systemic inflammation affects recurrence more acutely and less so chronically12.
The underlying mechanism of myocardial lesion formation following catheter ablation may provide insight into the potential effects of steroids and other anti-inflammatory agents. If steroids reduce the acute post-ablation inflammatory response that is responsible for lesion maturation, then steroids may impair lesion maturation and promote the late recurrence of AF. In our study, we did not observe such a phenomenon as there was not a significant difference in AF recurrence between individuals that received intraoperative dexamethasone and those that did not. As we have discussed, there is some evidence in support of the alternative hypothesis which suggests a benefit to suppression acute post-ablation inflammation with steroids and anti-inflammatory agents, such as colchicine3-5. However, these studies were performed with relatively small study populations and there has yet to be a large multicenter randomized trial to investigate this question. A more extensive and in-depth investigation is needed to determine the true effects of steroids on AF recurrence, as well as to determine the potential role of systemic and local inflammation in AF recurrence.