Initial Experience with the Reveal LINQ Insertable Cardiac Monitor

Case Description

Our patient is a 76-year-old woman with a history of hypertension and adult-onset diabetes. Recently she suffered a stroke that has left her with residual right-sided weakness. An extensive inpatient workup revealed no etiology for her stroke. This workup included MRI /MRA imaging, carotid arterial Doppler studies, and transthoracic and transesophageal echocardiograms. She was evaluated on telemetry for 72 hours which remained normal. She was discharged to home with a 30-day external loop recorder which was also normal. This is not uncommon — it is estimated that perhaps up to 25% of non-hemorrhagic strokes will be eventually classified as cryptogenic or stroke of unknown cause.¹ Recent evidence from the CRYSTAL-AF study presented at the International Stroke Conference 2014 demonstrated up to 30% of patients with cryptogenic stroke may have atrial fibrillation as the cause of their stroke (Figure 1). Continuous heart rhythm monitoring with an implanted cardiac monitor demonstrated superior detection of atrial fibrillation compared to standard follow-up methods (e.g., ECG, Holter monitor, external loop recorder) (Figure 1). Detecting atrial fibrillation in these patients allows us as to alter therapy to prevent further strokes (placing patients on oral anticoagulation).²

New Insertable Cardiac Monitor

In February of this year, the FDA approved Medtronic’s subcutaneous insertable loop recorder, the Reveal LINQ cardiac monitor. Like its predecessor, the Reveal XT, the LINQ maintains a three-year battery life and the ability to detect atrial fibrillation. However, LINQ has a number of revolutionary advancements. This new device is 87% smaller (about one-third the size of a triple A battery) (Figure 2). Enhanced atrial fibrillation detection algorithms, including P wave sensing algorithms, as well as increased memory are also new features with this device. Perhaps most importantly, the device is now capable of wireless communication to a cellular-based (provided to the patient) MyCareLink bedside monitor (Figure 3). This technology allows for daily downloads of alerts that have been triggered in the LINQ monitor. These alerts are programmed by the implanting physician and may be tailored to the individual patient’s needs. This alert notification allows physicians to be notified when an alert has been triggered, instead of waiting until the patient has symptoms or at the time of a monthly interrogation, as was the practice in previous generations of the device. Indications for use of the Reveal LINQ Insertable Cardiac Monitor include: 1) Patients with clinical syndromes or situations at increased risk for cardiac arrhythmias; and 2) Patients who experience transient symptoms such as dizziness, palpitation, syncope and chest pain, that may suggest a cardiac arrhythmia.

Discussion

Concerned that our patient could indeed have had atrial fibrillation as the source of her embolic stroke, I felt that continuous long-term monitoring was indicated in her case. On February 22, 2014, she underwent insertion of the LINQ monitor in one of the first implants in the United States. The implant procedure took only minutes, and she was discharged from the implant within about 10 minutes. A Steri-Strip was placed over the very small incision (less than half an inch). She required no sedation and only local anesthetic, describing no discomfort with the procedure. I received a Medtronic CareAlert notification 33 days after the implant; she had experienced a 10-hour episode of asymptomatic atrial fibrillation. Her treatment course was altered by placing her on oral anticoagulation. Given the CRYSTAL-AF data showing an average time to detect atrial fibrillation of 84 days (at the 12-month endpoint), her atrial fibrillation being found in 33 days was a much shorter time, but well beyond standard monitoring of 24-hour, 7-day or 30-day ambulatory monitoring. 

The LINQ monitor comes preloaded in an insertion tool, which allows for a simple insertion procedure (Figure 4). Other supplies needed to perform the implant are minimal, consisting mostly of those supplies needed for prep and drape of the implant site. The very small incision (less than half an inch) can be closed by Steri-Strip or DERMABOND skin adhesive. The smaller size of the device, ease of implant and lack of need to create a pocket for the device allows the implant procedure to be taken out of the EP lab. This patient’s LINQ implant and all those performed subsequently at Scripps have been performed in our cath lab pre-op holding area. 

As a clinician specializing in diagnosing, managing and treating heart rhythm disorders, the LINQ monitor is a tool that allows me to monitor patients for heart rhythm abnormalities on a continuous basis. Some of these patients may be at risk for stroke or recurrent stroke, syncope or sudden cardiac death. Patients with syncope due to a cardiac cause have a higher mortality.³ Implantable cardiac monitor use is supported by the most recent (2009) guidelines (Class 1 indication) in the evaluation of the syncope patient.⁴

Disclosure: The author has no conflicts of interest to report relative to the content herein. Outside the submitted work, Dr. Rogers reports consultancy, honoraria (as a speaker), payment for development of educational presentations including service on speakers’ bureau, and travel/accommodations expenses covered or reimbursed from Medtronic. 

References

1. Adams HP Jr, Bendixen BH, Kappelle LJ, et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke. 1993;24(1):35-41.
2. Camm AJ, Lip GY, De Caterina R, et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation: an update of the 2010 ESC Guidelines for the management of atrial fibrillation. Developed with the special contribution of the European Heart Rhythm Association. Eur Heart J. 2012;33(21):2719-2747.
3. Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med. 2002;347(12):878-885.
4. Task Force for the Diagnosis and Management of Syncope; European Society of Cardiology (ESC); European Heart Rhythm Association (EHRA); Heart Failure Association (HFA); Heart Rhythm Society (HRS), Moya A, Sutton R, Ammirati F, et al. Guidelines for the management and diagnosis of syncope (version 2009). Eur Heart J. 2009;30(21):2631-2671.