Continuous outpatient monitoring of a patient’s heart rhythm was initiated in 1949 with the invention of the Holter monitor by Norman J Holter. The early systems were bulky, recorded the heart’s rhythm for 24 or 48 hours onto a tape or cassette, and required that the data be analyzed by a technician after completion of the recording. As technology advanced, smaller devices (event recorders) were developed to allow patients to record their rhythms when they had symptoms. These could be used for longer periods of time, but were limited in that the patient had to place the monitor onto his or her skin to make a recording, so brief episodes of palpitations or episodes of syncope could not be captured. Patient-activated loop recorders (LOOPs), devices which continually record a patient’s rhythm via electrodes attached to the skin, were able to capture brief episodes of palpitations or episodes of syncope, but depended on the patient to activate them and could not detect asymptomatic episodes of arrhythmia. Mobile cardiac telemetry (MCT) is a relatively new technology, first approved in 2002 by the US Food and Drug Administration (FDA), which provides continuous realtime outpatient electrocardiographic monitoring for extended periods of time. MCT allows detection of both symptomatic and asymptomatic arrhythmias and has been proven to provide superior diagnostic capability for patients with palpitations, syncope, and pre-syncope.1–3 It also allows accurate monitoring of a patient’s rhythm during outpatient drug titration, as well as detection of both symptomatic and asymptomatic atrial fibrillation (AF) after cardiac ablation. Since recording of the rhythm is continuous, monitoring of a patient’s heart rate (as well as specific documentation of the initiation and termination of arrhythmias) is possible. This article will focus on how the use of MCT can improve diagnostic accuracy and, when combined with the use of a monitoring service that integrates the patient’s tracings within an electronic medical record (EMR), can also improve the efficiency of care given to patients.
The patient, a 56-year-old male, had a history of palpitations with documented runs of both supraventricular tachycardia (SVT) and AF. He was started on flecainide (a class Ic antiarrhythmic drug) for control of his arrhythmias and discharged home with an MCT device. The patient’s monitor triggered for SVT at a rate of 162 bpm at 4:50 am while he was doing his morning aerobic workout (see Figure 1).
It was unclear whether the tachycardia was an atrial tachycardia or sinus tachycardia. Review of the daily histograms (see Figure 2) revealed a slow onset and offset to the tachycardia that was consistent with sinus tachycardia. This rhythm (sinus tachycardia) does not require treatment with medications or cardiac ablation.
This would have been impossible to determine with a standard loop recorder (a cardiac event monitor), which would not have had the capability to view the slow onset and offset of the tachycardia, a feature that is only available with the MCT device. This could have potentially led to unnecessary invasive procedures or medication trials.
Mobile Cardiac Telemetry versus Standard Loop Event Monitoring
Rothman et al.1 studied a total of 266 patients in a 17-center prospective randomized trial examining the ability of a LOOP or Mobile Cardiac Outpatient Telemetry™ device (MCOT™, a trademarked name for one of the MCT monitors available) to confirm or exclude a probable arrhythmic cause of symptoms of syncope, pre-syncope, or severe palpitations after patients had undergone a non-diagnostic 24-hour Holter monitor. A diagnosis was made in 88 % of MCOT subjects compared with only 75 % of LOOP subjects (p=0.008). In a subset of patients presenting with syncope or pre-syncope, a diagnosis was made in 89 % of MCOT subjects compared with only 69 % of LOOP subjects (p=0.008). The MCT device was found to be superior in confirming the diagnosis of clinically significant arrhythmias, detecting such events in 55 of 134 patients (41 %) compared with 19 of 132 patients (15 %) in the LOOP group (p<0.001). It was clear from this study that the MCT device provided a significantly higher diagnostic yield than standard LOOPs in patients with symptoms suggestive of a significant cardiac arrhythmia.
Mobile Cardiac Telemetry for the Diagnosis of Palpitations, Syncope, and Pre-syncope
The key to diagnosing the etiology of palpitations, syncope, and near-syncope is to document the underlying rhythm at the time of symptoms. Historically, Holter monitors and event recorders have been used to attempt to make the diagnosis, but the diagnostic yields have been quite low, especially for the diagnosis of syncope, with yields in the 6–31 %4 range for event recorders and even lower for Holter monitors. This is understandable, since these events can occur infrequently and, for some event recorders, require activation of the device by the patient when symptoms occur.
MCT is ideal for the diagnosis of palpitations, syncope, and near-syncope, given the prolonged periods of monitoring that are possible and the ability of the device to auto-activate for changes in the patient’s rhythm. Olson et al.3 reviewed the records of 122 consecutive patients who were evaluated using an MCT monitor (in this case, the MCOT device) for palpitations, pre-syncope, or syncope, or to monitor the efficacy of an antiarrhythmic therapy. Ten of 17 patients (59 %) studied for pre-syncope/syncope had a diagnosis made. Eight of the 17 patients had a previous negative evaluation for pre-syncope/syncope and five had an event correlated with the heart rhythm during the monitoring period. Nineteen patients monitored for palpitations or pre-syncope/syncope were asymptomatic during the monitoring period, but had a prespecified arrhythmia detected. When MCOT was used as the first ambulatory monitoring system to evaluate palpitations (n=18), 73 % of patients correlated their symptoms with the underlying rhythm. MCOT was used to evaluate the efficacy of antiarrhythmic therapy in 29 patients—21 for medication titration and eight after radiofrequency ablation. The authors found the MCT device especially useful for outpatient titration of rate-controlling agents in patients with AF and an uncontrolled ventricular response.
Mobile Cardiac Telemetry and Atrial Fibrillation
AF is a very common arrhythmia, affecting an estimated 5.1 million people in the US. Since the prevalence of AF increases with age and the population is aging, the number of people who will be affected by AF is increasing dramatically. It is estimated that between 15 and 16 million people in the US will be affected by AF by 2050.5 The risks of AF include thromboembolic risks such as stroke (four to five times increased risk), as well as the risk of tachycardia-induced cardiomyopathy and heart failure. The ratio of asymptomatic (‘silent’ AF) to symptomatic AF has been estimated at around 12:1, thereby making it critical to capture asymptomatic episodes in high-risk patients. MCT is perfectly suited to capture both symptomatic and asymptomatic episodes of AF and allow appropriate treatment with anticoagulants, if prescribed, as well as other interventions such as antiarrhythmic drugs or radiofrequency ablation to keep patients in normal rhythm. Pre-ablation utilization of MCT is useful to document the AF burden (percentage of time in AF), the ventricular response to AF, and any regular SVT (atrial tachycardia or atrial flutter) that could be initiating episodes of AF. Post-ablation utilization of MCT is useful to document freedom from AF, which may allow discontinuation of antiarrhythmic drugs and possibly also anticoagulation, if appropriate.
MCT has also been beneficial in documenting AF in patients who have had a stroke or transient ischemic attack (TIA) with no obvious etiology after a standard diagnostic evaluation. Tayal et al.2 analyzed 56 consecutive patients with cryptogenic stroke with a mean of 21 days of monitoring with an MCT device. The AF detection rate was 23 % (13/56) detected after a median of seven days of monitoring. There were 27 episodes of asymptomatic AF detected in the 13 patients, of which 85 % (23/27) were <30 seconds and 15 % (4/27) were 4–24 hours in duration. These brief episodes of AF could potentially be markers of more prolonged episodes in some of these patients and might provide an explanation for their cryptogenic stroke or TIA, as well as providing a rationale for anticoagulation and possible prevention of future events.
eCardio’s Academic Medicine Site
So far, this article has discussed how the diagnostic yield for detecting various arrhythmias and symptoms such as palpitations and syncope increases with the use of the MCT device, but the timely and accurate delivery of information to physicians is equally as important as the use of the device itself. eCardio Diagnostics has a uniquely designed academic medicine site (AMS), which enables physicians to see data as they become available at any time of day and view reports on an as-needed basis (see Figure 3). Physicians are then alerted to critical or serious arrhythmias via phone, fax, email, or text message. The types of alert received by the physician are completely customizable to the institution and the physician. The report is provided in a format that allows physicians to enlarge the image and clearly view the arrhythmia from any device that connects to the Internet. The AMS, a fully Health Insurance Portability and Accountability Act (HIPAA)-compliant site, also provides physicians with the ability to view the onset and offset of arrhythmias, improving their ability to specify a treatment modality such as ablations or antiarrhythmic drug therapies. Notifications to physicians occur based on an established protocol. When a critical or serious rhythm is identified through live realtime monitoring by certified cardiac technicians (CCTs), physicians receive a web-based report and are alerted based on the method of their choice within 15 minutes of a critical event (30 minutes for a serious event). This enables physicians to act quickly and potentially improve the patients’ outcomes.
The AMS is also uniquely designed so that physicians can add or change study comments and have them reflected within the reports. This is carried out through report regeneration, which enables physicians to read and sign off on a report electronically instead of printing out the report and dictating comments, thus saving valuable time. The AMS is configured for academic institutions to track fellowship participation in reading studies as well. The website can be configured to allow fellows to read and interpret the study and send it to an attending physician to confirm the study findings. Based on studies read, verified with a date/time stamp and the user’s credentials, eCardio can provide a log of how many studies were read by the fellow for reporting purposes. Finally, the website allows a Code of Federal Regulations (CFR) 21 part 11, HIPAA-compliant electronic signature to be placed on the study. Through an EMR integration, eCardio can push the study directly into the institution’s EMR system. This prevents the need for studies to be manually handled, thus reducing administrative overhead costs and increasing the efficiencies of physicians.
MCT is an advanced form of continuous monitoring of a patient’s rhythm on an outpatient basis that has been proven to provide superior diagnostic yield when compared with other types of outpatient cardiac monitoring including LOOPs. When used in combination with eCardio’s AMS, MCT provides physicians with immediate access to potentially dangerous cardiac rhythms. The combination also allows them to determine the onset and offset of an arrhythmia, detect asymptomatic runs of arrhythmias such as AF, and enables physicians to read, sign, and file their patient’s loop tracings in an EMR with the click of a few computer keys. The creative fusion of technologies between MCT and AMS gives physicians the tools necessary for providing efficient, accurate, and safer outpatient cardiac monitoring to patients.