The Revolution in Cardiac Monitoring

Article Citation:

Jay Sengupta, Elizabeth Hoffman, Daniel Melby, and Charles Gornick (2017) The Revolution in Cardiac Monitoring. Journal of the Minneapolis Heart Institute Foundation: Fall/Winter 2017, Vol. 1, No. 2, pp. 136-137.

Editorial

Jay Sengupta, MD

Elizabeth Hoffman, PA

Daniel Melby, MD

Charles Gornick, MD

Minneapolis Heart Institute® at Abbott Northwestern Hospital, Minneapolis, MN

Address for correspondence:
Jay Sengupta, MD
Minneapolis Heart Institute®
920 E 28th Street, Suite 400
Minneapolis, MN 55407

E-mail: jay.sengupta@allina.com

INTRODUCTION

The Holter monitor, named after Norman J. Holter, has been a mainstay of ambulatory electrocardiography monitoring for more than 50 years (Figure 1). Recently, advances in cardiac telemetry have progressed exponentially as external cardiac monitors have transitioned beyond cumbersome boxes, wires, and electrodes to individual patches and insertable cardiac monitors. Implantable cardiac monitors (ICMs), previously the size of a universal service bus (USB) drive, are now the same size as a small piece of chewing gum (Figure 2). In this edition of the Journal of the Minneapolis Heart Institute Foundation, we present data from our institution on utilization of the new generation of ICMs, bringing to light many advantages over the older model, but also creating awareness about changing practice patterns and the need for more data to guide appropriate use.

FIGURE 1
Courtesy of Smithsonian National Museum of American History. Model 445, Mini-Holter Recorder, illustration from brochure, 1976.

FIGURE 2
Size comparison of the 2 models of ICMs. a. Reveal XT: 61 × 19 × 8 mm, 15.0 g. b. Reveal LINQ: 44.8 × 7.2 × 4.0 mm, 2.5 g.

Dramatic Increase in ICM Utilization

Our implantable cardiac monitor program has grown considerably with the release of the next-generation Medtronic Reveal LINQ monitor. More than 500 patients with LINQ devices are actively followed at our institution, with the vast majority of new devices implanted by the electrophysiology advanced practice providers (nurse practitioners and physician assistants) who have been credentialed after completing a rigorous mentoring process. The procedure was previously performed in the electrophysiology laboratory and is now performed in a hospital outpatient procedure area. While patients received conscious sedation in the past, local anesthetic is now usually adequate. Despite these transitions, our data show fewer complications associated with LINQ implants than with the earlier generation Reveal XT monitor. Implants are safe, and the patient experience is more favorable.

The fastest-growing population receiving the LINQ monitors has been cryptogenic stroke patients. The CRYSTAL AF1 study demonstrated fewer recurrent stroke and transient ischemic attacks in patients who were monitored with ICMs compared to standard Holter monitoring post cryptogenic stroke. This was a result of increased atrial fibrillation detection and subsequent use of anticoagulation. In partnership with Dr. Mark Young and Sherilyn Milner from Abbott Northwestern Hospital’s stroke team, LINQ implantation is now an integral part in the evaluation of cryptogenic stroke patients. As specified in this journal, of the 156 stroke patients receiving LINQs during the study period, 17.2% had atrial fibrillation detected, and most of these patients were started on oral anticoagulation. The majority of detections occurred after one month of monitoring. Thus, it appears that initial LINQ implant in this patient population may be preferable over Holter and external cardiac monitors that are more limited in the duration of monitoring. It is important to note, however, that a primary LINQ implant in cryptogenic stroke patients is considered investigational under many insurance policies.

LINQ monitors were also more frequently implanted for indications of palpitations and atrial fibrillation monitoring. There were fewer subsequent device implants such as pacemakers and defibrillators among patients with LINQ devices compared to the earlier XT model, and this may indicate a lower threshold to implant a LINQ based on the ease of the procedure. While the indication for an ICM was previously broad, national coverage determination2 now specifies that an implantable cardiac monitor be considered medically necessary in a subset of patients who experience at least 2 episodes of recurrent, infrequent, and unexplained symptoms of presyncope, syncope, or tachycardia with severe symptoms of hemodynamic instability, when the following criteria are met: cardiac arrhythmia is suspected as the cause of the symptoms and a prior trial of Holter monitor and other external ambulatory monitors has been unsuccessful in determining a definitive diagnosis.

There is also the challenge of monitoring the higher volume of LINQ patients in the device clinic. We have now transitioned to having a device clinic nurse dedicated solely to addressing remote transmissions and patient concerns. This includes adjudicating arrhythmias on LINQ electrogram transmissions, counseling patients on the correlation with their symptoms, and advising them on the appropriate monitoring and treatment strategy. Despite improvements in arrhythmia detection accuracy, the workflow in the device clinic is determined primarily by the sheer volume of patients who currently have LINQ devices and the patient-activated events reported. As a result, we have attempted to develop new guidelines for when to continue monitoring after multiple patient activations or transmissions do not demonstrate an arrhythmic basis for symptoms.Future Directions in Cardiac Monitoring

While Medtronic manufactures the most commonly used ICMs, other medical device companies are releasing their own monitoring tools. The current ICM can be thought of as a device that offers remote follow-up, but newer technology will essentially allow remote monitoring at an instant as information from the implantable device will be immediately transmittable through portable handheld devices. Clinics will need to continuously adapt to the vast amounts of information received and allocate resources to appropriately manage this growing data collection and determine follow-up.

While ICMs garner much attention due to the advent of newer technology and increase in utilization, the next revolution in cardiac monitoring is underway and in the hands of the individual patient. Heart rate monitoring via smartphone applications and wearable watches, for example, has been around for some time, but we are soon to see a range of personal, portable heart rhythm monitors on the market. Already, one can record and transmit a high quality electrocardiogram rhythm strip recording with minimal artifact, obtained by simply placing one’s fingers on an electrode interface connected wirelessly to a watch or smartphone. It is only a matter of time until these devices become more portable and universal. With an average of 90,000 heartbeats per day, imagine patients recording and transmitting all of this data electronically to a device clinic or by text or e-mail. We will be in need of much-improved automated rhythm analysis and algorithms to help with arrhythmia detection and classification. People will have personal control over reporting their heart rhythm, and it won’t be long before we are asked to view and interpret this data to make clinical decisions on a continual basis.

REFERENCES

1.Sanna T. Diener H. Passman RS.et al. Cryptogenic stroke and underlying atrial fibrillation. N Engl J Med. 2014;370:2478–2486. [Crossref] [Google Scholar]
2.Centers for Medicare & Medicaid Services. Medicare National Coverage Determinations (NCD) Manual. Available at: https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/Internet-Only-Manuals-IOMs-Items/CMS014961.html. Accessed September 26,2017. [Google Scholar]
Print ISSN: 
2475-0190
eISSN:
2475-0204