Introduction

A 74-year-old man with symptomatic severe aortic stenosis is deemed a poor surgical candidate for aortic valve replacement surgery and is referred for trans-catheter aortic valve implantation (TAVI). He undergoes a trans-apical procedure and has a short run of atrial fibrillation (AF) on the first day post-op. The episode of AF is entirely asymptomatic but is captured on telemetry and lasts for 2 hours. What is the optimal management strategy with respect to rhythm control and anti-coagulation?

Discussion

Trans-catheter aortic valve implantation is a new technique that has been shown to be a viable alternative to surgical aortic valve replacement in high-risk patients with symptomatic severe aortic stenosis.^{(1, 2)} Trans-femoral and trans-apical approaches are used for these trans-catheter implants. Two types of devices are manufactured, the CoreValve and the Edwards SAPIEN, the later being the device utilized in the landmark PARTNER trials. The number of TAVI procedures performed worldwide is expected to rise exponentially in the next few years. As such, an understanding of the incidence and consequences of peri-procedural complications is important in providing optimal clinical care of patients undergoing TAVI. With regard to rhythm disturbances, pacemaker implantation (within 30 days of the procedure) is necessary in one-third of patients receiving the CoreValve prosthesis whereas less than 5% of those with a SAPIEN valve required a pacemaker.^(1-4)

Recently, AF has been identified as a relatively common dysrhythmia post-TAVI, as it occurs in almost one-third of patients with no prior history of AF.⁽⁵⁾ The pathophysiology of post-procedural AF in patients undergoing TAVI is likely to be similar to the underlying processes that drive AF following cardiac surgery. These factors include peri-procedural systemic inflammation, direct pericardial inflammation (with trans-apical approach), and a hyper-adrenergic state related to stress of surgery and post-operative pain.

The work by Amat-Santos, et al, is a retrospective cohort study of 138 consecutive patients with no prior history of AF undergoing TAVI (SAPIEN valve) at a single center.⁽⁵⁾ Continuous rhythm monitoring was performed from the immediate post-procedural period through to discharge from the hospital. The trans-apical approach and increasing left atrial size were identified as risk factors for post-procedural AF. Motloch, et al, published similar findings that also demonstrated an increased risk of post-procedural AF in patients undergoing the trans-apical approach in their series of 84 patients.⁽⁶⁾ Their overall rate of AF, however, was much lower, at 6%. This may, in part, be explained by less intensive rhythm monitoring (continuous monitoring was mandated for 72 hours only). Another portion of this discrepancy can be explained by the percentage of cases performed via the trans-apical approach -- the Amat-Santos cohort had 73% trans-apical whereas the Motloch cohort was more evenly split with 51% trans-apical.

Overall, the incidence of post-procedural AF after TAVI in the Amat-Santos cohort was comparable to published rates of post-operative AF after cardiac surgery⁽⁷⁾ and much higher than that seen after non-cardiac surgeries.⁽⁸⁾ In adjusted analyses, mortality did not differ between patients with post-procedural AF and those without; however, patients with post-procedural AF had a higher incidence of stroke/systemic embolus and longer hospital stays.

The high incidence of stroke in the Amat-Santos cohort for patients who had post-procedural AF was striking, approaching 14%. Patients that developed post-procedural AF were significantly more likely to have stroke/systemic embolism than those that did not have AF (13.6% vs. 3.2%). Of note, among patients with post-procedural AF, the rate of stroke/systemic embolism was only 3% in those that were immediately anti-coagulated. In this study, the decision of whether to anti-coagulate the patients with short-lived AF (defined as AF lasting less than 12 hours) was left to the discretion of the treating physician, who withheld immediate therapeutic anti-coagulation in 10 out of 25 such patients (due to the presence of an epidural catheter or estimated high risk of bleeding). The risk of stroke in these patients who were observed to only have a single brief episode of AF was sobering. None of the 15 patients in this group who received immediate anti-coagulation had cardio-embolic events, while 4 of the 10 patients that did not receive immediate anti-coagulation suffered cardio-embolic events.

These data argue strongly that anti-coagulation should be immediately administered when post-procedural AF is documented. Importantly, dual anti-platelet therapy (aspirin and clopidogrel) is given routinely for 6 months following TAVI. In those patients that are therapeutically anti-coagulated (whether for AF or for other reasons), a scaling back of the anti-platelet regimen should be considered to decrease bleeding risk.

Given the high frequency with which patients develop AF after TAVI (and the association between AF and worse outcomes), pharmacologic prophylaxis for AF should be considered. Strong evidence exists for the efficacy of amiodarone⁽⁹⁾ and, to a lesser extent, beta-blockers⁽¹⁰⁾ and statins,⁽¹¹⁾ in the prevention of AF after cardiac surgery. Randomized controlled trials are needed to evaluate the impact and cost-effectiveness of using routine pharmaco-prevention for post-procedural AF in patients undergoing TAVI.

The current literature examining AF, as a post-procedural complication of TAVI, has limitations. These include small sample sizes (potentially leading to regression model overfitting), a lack of pre-procedural rhythm monitoring to evaluate for silent AF prior to TAVI, and the fact that the studies are single center with significant inter-institution variability in post-TAVI rhythm monitoring protocols. Multi-center studies with standardized rhythm surveillance protocols and consistent definitions are needed to better characterize post-procedural AF after TAVI.

Conclusions

AF is a common post-TAVI dysrhythmia, particularly when the trans-apical approach is employed and when patients have baseline left atrial enlargement. Thromboembolic events are frequent in patients developing post-procedural AF and aggressive anti-coagulation is imperative for their prevention, regardless of the duration of the AF episode. Studies of strategies to prevent AF (including pharmacological prophylaxis) are warranted, particularly in patients at highest risk for developing post-procedural dysrhythmia.

Returning to our patient that was presented in the introduction, the current literature would suggest that he should be therapeutically anti-coagulated in the absence of an absolute contraindication. Concomitant scaling back of anti-platelet therapy should be considered. The addition of anti-arrhythmic medications in the short term is reasonable, though there are no data to support their use, and risks and benefits should be weighed on a case-by-case basis.

References

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2. Smith CR, Leon MB, Mack MJ, Miller DC, Moses JW, Svensson LG, et al. Transcatheter versus surgical aortic-valve replacement in high-risk patients. N Engl J Med 2011;364:2187-98.
3. Guetta V, Goldenberg G, Segev A, Dvir D, Kornowski R, Finckelstein A, et al. Predictors and course of high-degree atrioventricular block after transcatheter aortic valve implantation using the CoreValve Revalving System. Am J Cardiol 2011;108:1600-5.
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9. Mitchell LB, Exner DV, Wyse DG, Connolly CJ, Prystai GD, Bayes AJ, et al. Prophylactic Oral Amiodarone for the Prevention of Arrhythmias that Begin Early After Revascularization, Valve Replacement, or Repair: PAPABEAR: a randomized controlled trial. JAMA 2005;294:3093-100.
10. Halonen J, Loponen P, Jarvinen O, Karjalainen J, Parviainen I, Halonen P, et al. Metoprolol versus amiodarone in the prevention of atrial fibrillation after cardiac surgery: a randomized trial. Ann Intern Med 2010;153:703-9.
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Keywords: Amiodarone, Aortic Valve, Arrhythmias, Cardiac, Cardiac Surgical Procedures, Prostheses and Implants

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