Using a New, Smaller Implantable Loop Recorder to Aid in Arrhythmia Detection and Anticoagulation Decisions After AF Ablation: One User’s Experience

Catheter ablation for atrial fibrillation (AF) has rapidly evolved over the past decade to become a common, safe, and effective treatment strategy for patients.¹ Now, many of those whom previously had to choose between the indefinite use of antiarrhythmic medications with modest efficacy and multiple side effects or continued symptoms of AF now have a third, potentially curable option. Patients can be liberated from the physical limitations imposed by AF and the medications used to control it. However, what about the anticoagulants that can prevent the devastation caused by a stroke, that most feared consequence of AF? As is all too common in electrophysiology, advances in technology and ablation techniques have grown more rapidly than we can collect outcome data, thus leaving us wondering how, if at all, we should change our practice. Nowhere in the treatment of complex arrhythmias is this more evident than in decisions regarding oral anticoagulation after an AF ablation. It is evident that we can cure atrial fibrillation with catheter ablation, but does this mean we also “cure” the need for anticoagulation? Is it safe to stop anticoagulation after a successful ablation? How do we know the ablation was indeed successful?

On the surface, it is easy to answer this question: if the patient on anticoagulants has an ablation, and if that ablation is successful, they no longer have an indication for oral anticoagulation, right? Despite the fact that this is a widely held assumption, the situation is much more complex. The HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of AF is clear that in the first two months, every patient, regardless of risk factors, should be anticoagulated.¹ But after two months, our understating of the risk of stroke and thromboembolism is far from complete. Therefore, the Writing Group has recommended continued indefinite oral anticoagulation in any patient who is at high risk of stroke based on the CHADS₂ or CHA₂DS₂VASc scoring systems.¹ This is based on the fact that recurrence, and in particular, asymptomatic recurrence of AF, is common after an ablation. In addition to this, the mechanism of stroke in the setting of AF may not be limited to the rhythm itself. In fact, a recent study of patients with dual-chamber pacemakers and continuous rhythm monitoring demonstrated that of the 40 patients that experienced a stroke, 29 (73%) did not have an episode of AF within 30 days of the event.² There are obviously other factors involved other than the rhythm, and these unknown factors may or may not be affected by ablation.

This is a real downer for patients! When I have tried to explain to patients that the ablation was a success, but they still need anticoagulation, they have a hard time reconciling these two seemingly contradictory statements. In response to their concerns, I often attempt to explain risk stratification with the CHADS₂ or CHA₂DS₂VASc scoring systems, but this generally forces their eyes to glass over in boredom and annoyance. It is important to keep in mind that an AF ablation is not a lifesaving or even life-prolonging procedure, but is meant to improve a patient’s quality of life. For many patients, oral anticoagulation has a substantial detrimental impact on quality of life. Whether it is diet restriction, frequent blood draws, inconvenience with regard to travel, or the variability we so often see with INR monitoring, anticoagulation can be very difficult for patients and providers. The new oral anticoagulants (NOACs) represent a substantial improvement in dosing convenience and safety, but they can be expensive. And even with these more reliable anticoagulants, the risk of bleeding is not negligible.³ For many of my patients, the inconvenience, risk, and fear of hemorrhage associated with anticoagulation is as concerning or even worse than the symptoms of AF. Indeed, oral anticoagulation is frequently discontinued after a perceived successful ablation,^4,5 even in high-risk patients.⁶ The risk of stroke after an ablation is not well defined. The ablation may in fact cause beneficial remodeling of the left atrium as well as reduce or eliminate the blood stasis associated with AF. This is supported by recent data suggesting that after an ablation, patients are at a lower risk of stroke,⁷ regardless of the CHADS₂ score.⁸ 

Despite this, guidelines remain quite conservative with regard to oral anticoagulation. Following the current guidelines and basing the decision regarding anticoagulation only on risk factors and ignoring the fact that the patient has had a potentially curative procedure could lead to over-anticoagulation, not to mention patient consternation. However, this must be balanced with the reality that the patient may still be at risk for stroke. 

Fortunately, there is a tool that can help us decide who can safely discontinue anticoagulation. An implantable loop recorder (ILR) can monitor patients for recurrence, providing about three years’ worth of continuous monitoring. Ambulatory ECG monitors are also commonly used to monitor for recurrence, but ILRs have been shown to be superior at detecting recurrence after ablation than repeat 30-day event monitoring.⁹

The first-generation ILRs have proved to be very useful tools. The implant procedure for these devices is safe and fairly easy to do. However, Medtronic’s new Reveal LINQ Insertable Cardiac Monitor (ICM) takes the ease of implant a step further. It takes only moments to implant, leaving behind a small, nearly imperceptible scar. This quick implant procedure can also easily be done while the patient is still on the table after the ablation. I now find myself frequently turning to this new ILR to guide my post-ablation anticoagulation therapy.

When I implant the Reveal LINQ after an AF ablation, my protocol is to remove the catheters, then prep the chest while protamine is being administered to reverse the anticoagulation. The device is implanted at the level of the 4th or 5th intercostal space by making a small nick in the skin to the left of the sternum at a 45° angle to the sternum. If the device gets hung up during delivery, it is invariably at the skin level; therefore, I am sure to create a generous nick in the skin. A very small pocket is created using the tool provided with the device, and it is “injected” into the pocket with the provided delivery system. Pressure is held until hemostasis is achieved, then the incision is dressed. I generally use a thrombin-coated dressing and adhesive bandage. 

After a 2- to 3-month blanking period, one can check the device and make anticoagulation decisions based on the data that is obtained. It can also be checked remotely using Medtronic’s CareLink Network. Not only can I detect asymptomatic recurrence, but I can also use it to determine if less specific symptoms, such as fatigue or dyspnea, do indeed represent recurrence or not. In addition to guiding anticoagulation decisions, it also allows the electrophysiologist to monitor ablation outcomes and track success rates. 

My practice has begun to implant this device in patients with an intermediate risk of stroke, such as those with a CHADS₂ score of 2-3. If the patient is very low risk and long-term anticoagulation would not be indicated even in the setting of recurrence, I do not feel the device is useful. Likewise, if the patient is at high risk for stroke (e.g., patients that have already had a stroke), I generally anticoagulate regardless of the results of the ablation, so an ILR is not as useful for them. But for those patients in the middle, who represent the majority of my AF ablations, an ILR such as the Reveal LINQ can be very helpful. 

The field of AF ablation continues to evolve rapidly, and the standard of care can seem like a moving target. We rarely have definitive data indicating the “best” thing to do for patients, but a few things regarding post-ablation anticoagulation are clear: (1) most patients who have had a perceived successful ablation do not want to take anticoagulation; (2) it is often discontinued despite current recommendations; and (3) it may not be necessary after the ablation, particularly if the patient has no recurrent AF.^4-8 The Reveal LINQ ICM is a useful tool that provides the electrophysiologist with a minimally invasive and convenient method for detecting both symptomatic and asymptomatic recurrence after an AF ablation. In addition to guiding anticoagulation therapy, the device provides thorough data to track ablation outcomes. This may result in less overutilization of warfarin and NOACs, reduced cost overall, and increased patient satisfaction. 

Acknowledgement. Special thanks to Debi Smedlund, BS for her expert media support with this article.

Disclosure: Outside the submitted work, Dr. Latacha reports personal fees from Medtronic; he is also a faculty member for the Medtronic Arctic Front Masters course as well as a field educator.   

References

1. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Heart Rhythm. 2012;9(4):632-696.
2. Daoud EG, Glotzer TV, Wyse DG, et al. Temporal relationship of atrial tachyarrhythmias, cerebrovascular events, and systemic emboli based on stored device data: a subgroup analysis of TRENDS. Heart Rhythm. 2011;8(9):1416-1423.
3. van der Hulle T, Kooiman J, den Exter PL, et al. Effectiveness and safety of novel oral anticoagulants as compared with vitamin K antagonists in the treatment of acute symptomatic venous thromboembolism: a systematic review and meta-analysis. J Thromb Haemost. 2014;12(3):320-328.
4. Mardigyan V, Verma A, Birnie D, et al. Anticoagulation management pre- and post atrial fibrillation ablation: a survey of canadian centres. Can J Cardiol. 2013;29(2):219-223.
5. Nührich JM, Kuck KH, Andresen D, et al. Oral anticoagulation is frequently discontinued after ablation of paroxysmal atrial fibrillation despite previous stroke: data from the German Ablation Registry. Clin Res Cardiol. 2014 Dec 24. [Epub ahead of print]
6. Winkle RA, Mead RH, Engel G, et al. Discontinuing anticoagulation following successful atrial fibrillation ablation in patients with prior strokes. J Interv Card Electrophysiol. 2013;38(3):147-153. 
7. Ha AC, Hindricks G, Birnie DH, et al. Long-term oral anticoagulation for patients after successful catheter ablation of atrial fibrillation: is it necessary? Curr Opin Cardiol. 2015;30(1):1-7.
8. Bunch TJ, May HT, Bair TL, et al. Atrial fibrillation ablation patients have long-term stroke rates similar to patients without atrial fibrillation regardless of CHADS2 score. Heart Rhythm. 2013;10(9):1272-1277.
9. Kapa S, Epstein AE, Callans DJ et al. Assessing arrhythmia burden after catheter ablation of atrial fibrillation using an implantable loop recorder: the ABACUS study. J Cardiovasc Electrophysiol. 2013;24(8):875-881.