ECG technology has come a long way since the early 1900s when five people were needed to operate the first 600-pound machines and patients placed each limb in a bucket of salt water. The first breakthrough in mobility came in 1949 with Holter continuous monitoring device and was followed by even less cumbersome patient-activated intermittent event monitoring systems.
The early 2000s ushered in another new technology -- the mobile cardiac telemetry (MCT) system, which features a small sensor and lightweight monitor that patients wear throughout the day and provides continuous data to physicians for up to 30 days.
Although the MCT systems are patient-friendly and perform well, many physicians continue to prescribe Holter and event monitors. According to a retrospective analysis of claims data for more than 200,000 patients, the diagnostic yield of patients monitored with MCT devices is 61% compared to only 24% for patients using a Holter monitor and 23% for those using an event monitor. The study’s authors concluded that “the use of MCT devices instead of event or Holter monitors leads to better outcomes regarding diagnostic yield, management of arrhythmia through the use of antiarrhythmic drugs, and cost savings in the hospital for ablation, CABG, heart/pericardium, and valve/septa procedures.”
Market analysts expect that the use of MCT devices will grow rapidly, due to an aging population and increasing demand for more cost-effective cardiac monitoring in home care settings. This briefing paper will examine why, despite their convenience to patients and higher diagnostic yield, many electrophysiologists and cardiologists often do not select MCT systems for remote cardiac monitoring. It will also discuss the latest technological advances that address MCT systems’ limitations by providing a continuous, complete picture of the patient’s AF and other arrhythmia burden.
MCT Systems: Diagnostic Accuracy Limited by Small Sampling Size
MCT systems are essential for certain procedures and situations requiring longer term patient monitoring. The devices typically transmit 30-second samples of ECG activity, called “trending strips,” every 10 minutes and use a simple, continuous ECG interpretation algorithm to create AF and other arrhythmia burden trends.
Despite the aforementioned study showing that this method compares favorably to Holter and event monitors, other scientists have raised the issue of whether the quantitative information provided by MCT systems may be misleading to the interpretative physician. Since the basis for calculations are the trending strips, this means that the quantitative trending information is extrapolated from only a fraction of the actual ECG signal. From a statistical analysis standpoint, this small sampling size causes a sampling condition that generally makes it impossible to discern an unambiguous signal.
For example, if the 30-second ECG sample used for creating one value of the trend contains AF with HR above 180 bpm, the assumption will be that 10 minutes of the data contain constant AF with a rate of 180 bpm. In reality, however, the duration of the episode may have been only 30 seconds.
A limited sample size and simple rate-based ECG interpretation algorithm means that MCTs are not capturing all ventricular and supraventricular arrhythmias. One study of patients who had a heart attack as well as severely reduced heart function found that most dangerous arrhythmias were started by a PVC heartbeat. In addition, sampling does not provide information on the onset or offset of arrhythmia episodes.
Attributes of an Ideal Arrhythmia Diagnostic Tool
As ambulatory arrhythmia monitoring technologies have evolved over the last 70 years, each new method has had both unique benefits and inherent drawbacks. Clearly, what’s needed is a hybrid solution in a single device that combines the best features of today’s three most commonly used monitoring technologies:
- The continuous, online monitoring capabilities and convenience of lightweight MCT systems
- The quantitative reporting of measured findings and continuous storage of ECG data typical of Holter monitoring systems
- The symptom-reporting capabilities typical of event monitoring applications
Ideally, this device would automatically collect information that would enhance compliance with ACC/AHA/ESC guidelines for the management of patients with AF. Lastly, it would provide prescribing physicians with reports featuring easily interpreted statistical ECG analysis summaries supported by detailed, comprehensive data on patients’ heart activity.
PocketECG: Analyzing Every Heart Beat to Give You the Complete Picture
Such considerations were the impetus for the development of a new kind of diagnostic system, the PocketECG -- the only FDA-approved device that records and annotates every QRS complex and recognizes its morphology and streams the continuous ECG signal. Unlike other online diagnostic methods that capture the ECG at infrequent intervals and extrapolate potential arrhythmia statistics and features from limited signal samples, the PocketECG provides continuous, online ambulatory arrhythmia diagnosis information with arrhythmia detection efficacy comparable to the most effective Holter system.
The PocketECG transmits, discloses, and labels every heartbeat using algorithms that run full statistical analyses and send the full disclosure ECG signal to service centers staffed with cardiac technicians. And, unlike the offline Holter system applications, this device features a patented self-learning ECG interpretation algorithm that detects QRS complexes and classifies heart beats’ morphology, which can be viewed online by doctors and nurses.
Continuous monitoring enables the device to detect all ventricular and supraventricular arrhythmias, including individual PVCs or PACs, and provides access to the onset and offset for every arrhythmia episode. By providing an unmatched level of statistical analysis, the Pocket ECG makes precise diagnosis possible, even for the toughest arrhythmia cases.
New Feature Monitors Patients’ Physical Activity
According to ACC/AHA/ESC recommended guidelines for managing patients with persistent or permanent AF, a patient’s heart rate should be measured both at rest and during exercise before using rate-controlling medication. Yet until now, physicians have had to rely on patients to manually log their physical activity during arrhythmia monitoring to be able to roughly correlate these activities with heart rate changes.
To address this issue, PocketECG now includes a built-in accelerometer that continuously and objectively monitors patients’ physical activity. The device also enables patients to report their symptoms such as chest pain, dizziness, or heart palpitations with the touch of a screen. These features make it easy for health care professionals to differentiate between heart rate changes triggered by physical activity and those triggered by an arrhythmia. The new feature also allows healthcare professionals to determine the correlation between patient’s physical activity, patients’ symptoms and various types of arrhythmia.
Robust Reports, Easily Interpreted
Physicians and nurses can use an online portal for instant access to the PocketECG’s daily and event-driven urgent reports. An End of Study (EoS) report published after the conclusion of monitoring features:
- Results reported in a numerical format similar to Holter applications with a front-page summary analysis of hundreds of thousands of heartbeats
- Full statistical reporting that includes PVC count, PAC count, AF and sinus rhythm
- Extreme values for each type of arrhythmia
- A chart showing all symptomatic and asymptomatic events
- A calendar view of trends for symptoms, atrial fibrillation, ventricular arrhythmia, supraventricular arrhythmia, and sinus bradycardia, which can be used to correlate HR, patient triggered symptoms, and rhythm changes with the patient’s weekly activity
Get the Full Story on Your Patients’ Heart Activity
Many cardiac conditions cannot be diagnosed with a single ECG test or by using standard diagnostic methods of arrhythmia detection. New technology however, is allowing cardiologists and electrophysiologists to see and do more. Devices like PocketECG make precise diagnosis possible, combining continuous online monitoring capabilities, high quality quantitative analysis and reporting, and direct correlation between physical activity, symptoms and arrhythmia.
As the population in many countries ages, there will be an increasing demand for cost-effective cardiac monitoring in home care settings. Electrophysiologists and cardiologists should feel confident that MCT is an effective option for remote cardiac monitoring.