Discussion
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.
Figure 1. Study Design Schematic