This document addresses the use of both standard external and implantable ambulatory event monitors (AEMs) for the detection of abnormal heart rhythms that cannot be detected by other means.  This document does not address the use of AEMs equipped with cellular telecommunications equipment for real time physician notification. For information related to these devices, refer to MED.00051 Real-Time Remote Heart Monitors. Also, this document does not address continuous 24-48 hour Holter monitoring.

Medically Necessary: 

The use of external ambulatory event monitors is considered medically necessary as a diagnostic alternative to Holter monitoring in individuals who experience infrequent symptoms (less frequently than once every 48 hours) suggestive of cardiac arrhythmias. 

The use of implantable ambulatory event monitors is considered medically necessary only in the small subset of individuals who experience recurrent symptoms so infrequently that a prior trial of Holter monitor or an external ambulatory event monitor are not likely to be successful. 

Not Medically Necessary:

Other uses of ambulatory event monitors and telemetry are considered not medically necessary including, but not limited to, the following clinical situations:

• Monitoring effectiveness of antiarrhythmia therapy and detection of myocardial ischemia by detecting ST segment changes;
• Following catheter or surgical ablation of atrial fibrillation;
• Monitoring for the presence of atrial fibrillation in individuals with cryptogenic stroke.

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy.  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

Ambulatory event monitors (AEMs) were developed to provide longer periods of EKG monitoring, compared to ambulatory Holter electrocardiography, which is limited to 24 to 48 hours.  With AEM, the recording device is either worn continuously or activated only when the individual experiences symptoms.  The recorded EKGs are then either stored for future analysis or transmitted over telephone lines to a receiving station, e.g., a doctor's office, hospital, or to a cardiac monitoring service.

Newer AEM devices have the capacity to transmit data to a monitoring station via cellular telephone connections in real time. These devices are not addressed in this document and are the subject of MED.00051 Real-Time Remote Heart Monitors.

Implantable AEMs are also available for those instances where individuals experience such infrequent symptoms that extended monitoring is needed.  These devices are inserted just under the skin in the chest area during an outpatient surgical procedure.  The device may remain implanted for over one year.  Implantable loop recorders have the ability to record events either automatically (auto activated) or by manual activation (self-activated).

In 1999, the American College of Cardiology (ACC), in conjunction with other organizations, published clinical guidelines for ambulatory electrocardiography with the following Class I recommendations: (Crawford 1999)

• Individuals with unexplained syncope, near syncope, or episodic dizziness in whom the cause is not obvious;
• Individuals with unexplained recurrent palpitation;
• To assess antiarrhythmic drug response in individuals in whom baseline frequency of arrhythmia has been characterized as reproducible and of sufficient frequency to permit analysis.

There were two Class IIa recommendations as follows: 

• To detect proarrhythmic responses to antiarrhythmic therapy in individuals at high risk;
• Individuals with suspected variant angina.

These guidelines describe both Holter monitors and ambulatory event monitors, but the recommendations do not distinguish between the different types of monitors.  These guidelines also predate the commercial availability of external loop recorders with autotriggered capability or implantable loop recorders.  However, these guidelines are helpful to define the indications for ambulatory ECG in general, with the choice of specific device used dependent on the frequency of symptoms.  Of the Class I and IIa recommendations listed above, only the assessment of unexplained symptoms, such as syncope and palpitation would occur infrequently enough to warrant the use of an ambulatory event monitor.  The other indications could be adequately assessed with short term monitoring with a Holter monitor.  Additionally, in 2001, the ACC published a clinical competence statement on ECG and ambulatory ECG (Kadish, 2001) that stated that the indications for ambulatory ECG were addressed in the 1999 clinical guidelines (Crawford, 1999).  The competence statement noted:

There are no specific guidelines that distinguish patients for whom it is appropriate to perform continuous monitoring, (i.e., Holter monitor) from those for whom intermittent ambulatory monitoring is adequate. However, when monitoring is performed to evaluate the cause of intermittent symptoms, the frequency of the symptoms should dictate the type of recording (Kadish, 2001).

In 2006, the American Heart Association (AHA), in conjunction with other organizations, published a scientific statement on the evaluation of syncope (Strickberger, 2006).  This scientific statement did not provide specific recommendations, but reviewed the role of "non-invasive ECG monitoring" in different clinical situations.  Ambulatory event monitoring was specifically identified as an accepted technique in individuals with syncope with an otherwise normal history and physical exam, as follows:

The type and duration of ambulatory ECG monitoring is dictated by the frequency of symptoms.  A Holter monitor is appropriate for episodes that occur at least every day.  Event monitoring is ideal for episodes that occur at least once a month.  An implantable loop monitor allows the correlation of symptoms with the cardiac rhythm in patients in whom the symptoms are infrequent (Strickberger, 2006).

Therefore, the ACC guidelines and clinical competence statement and the AHA scientific statement on evaluation of syncope are consistent with the medical necessity indications included in this document.

More recently, there has been interest in the use of event monitors to further characterize atrial fibrillation in the following clinical situations:

• Detection of atrial fibrillation in individuals with cryptogenic stroke;
• Following catheter or surgical ablation for the treatment of atrial fibrillation to detect persistent or recurrent atrial fibrillation.

Neither of these indications is included in the recommendations of the ACC practice guidelines addressing the management of individuals with atrial fibrillation (Fuster, 2006).  Both of these indications will be discussed below, based on a review of other relevant disease specific guidelines and a literature search for controlled clinical trials focused on the clinical utility of ambulatory event monitoring in these clinical situations.

Detection of Atrial Fibrillation in Individuals with Cryptogenic Stroke -
As its name implies, cryptogenic stroke describes stroke without an identifiable cause.  Specifically, a cardioembolic source, such as a patent foramen ovale or atrial fibrillation (AF), has been ruled out during an initial workup consisting of various imaging studies and ECGs.  It is estimated that some 36% of stroke survivors have cryptogenic stroke.  It has been suggested that additional monitoring may identify AF in stroke initially categorized as cryptogenic (Tayal, 2008).  The presence or absence of AF has a significant impact on post-stroke management.  For example, the AHA and the American Stroke Association (ASA) jointly published guidelines for the prevention of stroke in individuals with a prior ischemic stroke or transient ischemic attack (TIA). (Sacco, 2006)  These guidelines recommend that individuals with cryptogenic stroke take aspirin for secondary stroke prevention, while the ACC guidelines addressing AF recommend careful consideration of warfarin, due to its superior efficacy for stroke prevention (Fuster, 2006).  Guidelines published by the American College of Chest Physicians (ACCP) also recommend anti-platelet therapy, (e.g., aspirin) in individuals with cryptogenic stroke, while anticoagulation therapy is recommended in individuals with AF (Albers, 2008). However, none of these guidelines specifically recommend extended ECG monitoring in individuals with cryptogenic stroke.

A literature search, focusing on clinical trials, did not identify any studies of ambulatory event monitors in individuals with cryptogenic stroke.  A broader search identified a systematic review of noninvasive cardiac monitoring in the post-stroke setting (Liao, 2007).  The authors specifically sought to determine the frequency of occult AF detected by noninvasive methods of continuous cardiac rhythm monitoring in consecutive individuals with ischemic stroke; a total of five prospective case series were included in the analysis.  Five studies evaluated Holter monitoring for 24 to 72 hours in the inpatient setting and are not considered further.  The two studies that focused on loop recorders, following a negative Holter monitor, are relevant to this discussion (Barthelemy, 2003; Jaboudon, 2004).  New AF was identified in 5.7% and 7.7% of subjects, respectively.  In the study by Jaboudon, oral anticoagulation was started in two of the seven subjects with new onset AF.  The authors concluded that increased duration of monitoring appears to be associated with increased rates of detection of AF, however, the authors also comment that it is uncertain whether any type of monitoring, including Holter monitoring, should be routinely performed given the low incidence of AF.

An additional literature search focused on studies published since the 2007 systematic review.  No clinical trials were identified.  One retrospective study of mobile cardiac outpatient telemetry (MCOT) in individuals with cryptogenic stroke was identified (Tayal, 2008).  While MCOT is addressed in a separate document, this study can also be applied to ambulatory event monitors, in general.  The study included 56 subjects with cryptogenic stroke; all subjects had undergone an admission ECG, inpatient cardiotelemetry and 24 hour Holter monitoring without evidence of AF.  Subjects underwent additional ambulatory event monitoring for a mean of 21 days; 27 episodes of AF were detected in 13 subjects (23%).  In three subjects, AF lasted longer than 30 seconds; there were four episodes of AF lasting from 4 to 24 hours.  The authors note that there has been no prospective study evaluating prolonged arrhythmia monitoring methods in cryptogenic stroke.  This study also raises the issue of the clinical significance of short episodes of AF, specifically whether or not this finding should warrant long-term anti-coagulation therapy, which is associated with its own risks and benefits.  The predominant finding in this study was brief episodes of AF lasting less than 30 seconds.  The authors note that the natural history of these brief episodes remains poorly understood, and the optimal management of individuals with brief runs of AF has not been established.

In summary, the available data suggest the clinical validity of prolonged monitoring in individuals with cryptogenic stroke. However, there are inadequate studies of the clinical utility of this technology, specifically the timing of monitoring post-stroke, the clinical significance of short runs of AF and the impact on the decision of whether or not to initiate anticoagulation therapy.

Following Catheter Ablation of Atrial Fibrillation (AF) -
Ablation, as a treatment of AF, is an option in individuals with symptomatic AF, in individuals who are refractory or intolerant to pharmacologic management, and in selected individuals with heart failure and/or reduced ejection fraction.  Catheter ablation of AF is addressed in MED.00064 Transcatheter Ablation of Arrhythmogenic Foci in the Pulmonary Veins as a Treatment of Atrial Fibrillation (Radiofrequency and Cryoablation).  In 2007, the Heart Rhythm Society (HRS), in conjunction with other organizations, published a consensus statement addressing the follow-up of individuals undergoing ablative therapy for AF (HRS, 2007).  This consensus statement pointed out that careful attention to anticoagulation therapy is needed, both before and after the ablative procedure, to avoid the occurrence of a thromboembolic event, which is considered one of the most serious complications of both AF and AF ablation procedures.  For example, early recurrences of AF are common during the first one to three months following ablation, due to remodeling and healing.  For this reason, monitoring to assess the efficacy of catheter ablation is typically delayed for at least three months, following the ablation.  The consensus statement notes that monitoring options include intermittent sampling using a standard ECG, or the use of an ambulatory event monitor.  However, the consensus does not indicate how this information is used in the management of the individual, specifically whether or not to discontinue anticoagulation therapy.  For example, the consensus statement provided the following recommendations for anticoagulation after ablation:  (These indications are not based on the presence or absence of AF.)

• "Warfarin is recommended for all patients for at least two months following an AF ablation procedure;
• Decisions regarding the use of warfarin more than two months following ablation should be based on the patient's risk factors for stroke and not on the presence or absence or type of AF;
• Discontinuation of warfarin therapy post-ablation is generally not recommended in patients who have a CHADS score* greater than 2." (HRS, 2007)

The ACC guidelines on the management of AF address the role of ablation techniques, and note:

The long term efficacy of catheter ablation to prevent recurrent AF requires further study.  Available data demonstrate 1 year or more free from recurrent AF in most (albeit, carefully selected) patients. It is important to bear in mind, however, that AF can recur without symptoms and be unrecognized by the patient or the physician.  Therefore, it remains uncertain whether apparent cures represent elimination of AF or transformation into an asymptomatic form of paroxysmal AF. The distinction has important implications for the duration of anticoagulation treatment (Fuster, 2006).

Therefore, at the present time, there is inadequate data to support the use of ambulatory event monitoring post-ablation therapy to determine the need for continued anticoagulation therapy.

*The CHADS (cardiac failure, hypertension, age, diabetes, stroke) score is a risk assessment tool that is based on a point system, in which 2 points are assigned for a history of stroke or TIA, and 1 point each is assigned for age over 75 and a history of hypertension, diabetes or recent heart failure.  The adjusted stroke rate can be assessed based on the CHADS score.  For example, a CHADS score of 2 is associated with an adjusted stroke rate of 4% per year (Fuster, 2006).

Peer Reviewed Publications:

1. Barthelemy JC, Feasson-Gerard S, Garnier P, et al. Automatic cardiac event recorders reveal paroxysmal atrial fibrillation after unexplained strokes or transient ischemic attacks. Ann Noninvasive Elctrocardiol. 2003; 8(3):194-199.
2. Jabaudon D, Szatjzel J, Sievert K, et al. Usefulness of ambulatory 7-day ECG monitoring for the detection of atrial fibrillation and flutter after acute stroke and transient ischemic attack. Stroke. 2004; 35(7):1647-1651.
3. Tayal AH, Tian M, Kelly KM, et al. Atrial fibrillation detected by mobile cardiac outpatient telemetry in cryptogenic TIA or stroke. Neurology. 2008; 71(21):1696-1701.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Agency for Healthcare Research and Quality (AHRQ). Remote cardiac monitoring. Technology Assessment. ECRI Evidence-based Practice Center (EPC). Contract No. 290-02-0019. Rockville, MD: AHRQ; December 12, 2007. Available at: http://www.cms.hhs.gov/determinationprocess/downloads/id51TA.pdf. Accessed on April 18, 2011.
2. Albers GW, Amarenco P, Easton JD, et al. Antithrombotic and thrombolytic therapy for ischemic stroke: American College of Chest Physicians evidence based clinical practice guidelines (8^th edition). Chest. 2008; 133(6 Suppl):630S-669S.
3. Blomstrom-Lundqvist C, Scheinman MM, Aliot EM, et al. European Society of Cardiology Committee, NASPE-Heart Rhythm Society. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary. A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the European Society of Cardiology Committee for practice guidelines (writing committee to develop guidelines for the management of patients with supraventricular arrhythmias) developed in collaboration with NASPE-Heart Rhythm Society. J Am Coll Cardiol. 2003; 42(8):1493-1531.
4. Brignole M, Vardas P, Hoffman E, et al. European Society of Cardiology (EHRA).  Position Paper:  Indications for the use of diagnostic implantable and external ECG loop recorders.  Europace. 2009; 11:671–687. 
5. Centers for Medicare and Medicaid Services. National Coverage Determination for Electrocardiographic (EKG) Services. NCD #20.15. Effective date: August 26, 2004. Implementation date: December 10, 2004. Available at:  http://www.cms.hhs.gov/mcd/viewncd.asp?ncd_id=20.15&ncd_version=2&basket=ncd%3A20%2E15%3A2%3AElectrocardiographic+%28EKG%29+Services. Accessed on April 18, 2011.
6. Crawford MH, Bernstein SJ, Deedwania PC, et al. ACC/AHA guidelines for ambulatory electrocardiography: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to revise the Guidelines for Ambulatory Electrocardiography). Circulation. 1999; 100(8):886-893.
7. Fuster V, Rydén LE, Cannom DS, et al. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Association and the Heart Rhythm Society. Circulation. 2006; 114(7):e257-e354. Available at: http://circ.ahajournals.org/cgi/reprint/114/7/e257. Accessed on April 19, 2011.
8. Heart Rhythm Society HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm. 2007; 4(6):816-861.
9. Kadish AH, Buxton AE, Kennedy HL, et al. ACC/AHA Clinical Competence Statement on electrocardiography and ambulatory electrocardiography: a report of the ACC/AHA/ACP-ASIM Task Force on Clinical Competence (ACC/AHA Committee to develop a clinical competence statement on electrocardiography and ambulatory electrocardiography). Circulation. 2001; 38(7):2091-2100.
10. Sacco RL, Adams R, Albers G, et al. Guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attack: a statement for healthcare professions from the American Heart Association and the American Stroke Association Council on Stroke. Circulation. 2006; 113(10);e409-e449. Available at: http://circ.ahajournals.org/cgi/reprint/113/10/e409. Accessed April 19, 2011.
11. Strickberger SA, Benson DW, Biaggioni I, et al. ACC/ACCF scientific statement on the evaluation of syncope: from the American Heart Association Councils on Clinical Cardiology, Cardiovascular Nursing, Cardiovascular Disease in the Young, and Stroke, and the Quality of Care and Outcomes Research Interdisciplinary Working Group; and the American College of Cardiology Foundation in collaboration with the Heart Rhythm Society. J Am Coll Cardiol. 2006; 47(2):473-484.
12. U.S. Food and Drug Administration (FDA). Center for Devices and Radiologic Health. Reveal^® Plus Insertable Loop Recorder (ILR) System. 510(k) No. K003667. Rockville, MD: FDA. February 14, 2001. Available at:  http://www.accessdata.fda.gov/cdrh_docs/pdf/K003667.pdf. Accessed on April 19, 2011.
13. U.S. Food and Drug Administration (FDA). Center for Devices and Radiologic Health. Sleuth^™ Implantable ECG Monitoring System. 510(k) No. K063035. Rockville, MD: FDA. October 1, 2007. Available at: http://www.accessdata.fda.gov/cdrh_docs/pdf6/K063035.pdf. Accessed on April 19, 2011.
14. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to develop guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death). Circulation. 2006; 114(10):1088-1132. Available at: http://circ.ahajournals.org/cgi/reprint/114/10/e385. Accessed on April 19, 2011.

Ambulatory Event Monitors
Cardiac Arrhythmias
Cardiac Event Monitors/Loop Recorders
Reveal^® Plus Insertable Loop Recorder
Sleuth ^™ Implantable ECG Monitoring System