Advances in Ambulatory Diagnostic ECG Monitoring

EP Lab Digest talks with Dr. Robert Schwarzberg and Jose Joglar, MD, about the advances in Ambulatory Diagnostic ECG Monitoring. Dr. Schwarzberg, a leader in the telemedicine industry since 1989, authored a patent on a hybrid smart event recorder. Dr. Joglar is the Assistant Professor of Internal Medicine at the UT Southwestern Medical Center in Dallas, Texas.

RJS: Our newest family of intelligent event recorders, coupled with our 24/7 monitoring center, now offers physicians the ambulatory equivalent of hospital telemetry. Auto triggers for atrial fibrillation (any ventricular rate), tachycardias, bradycardias and pauses assure capture of clinically important events, even in asymptomatic patients. Our patented looping memory captures the transition from normal to abnormal in single or simultaneous three-lead recordings. The data is immediately accessible over the telephone and reviewed by our experienced cardiac technicians with physician notification if predetermined criteria are met. For electrophysiologists, this provides the kind of information that is invaluable in determining both etiology of a problem and the preferred therapeutic intervention.

RJS: Traditional benchmark testing required for FDA approval demonstrated 93% episode sensitivity and 80% positive predictivity of events on the LifeStar AF Express ® monitor. The LifeStar AF+ ® monitor was also tested in the traditional manner and by a group in Texas. At the University of Texas Southwestern Medical Center, the LifeStar AF+ atrial fibrillation algorithm was independently evaluated by Dr. Jose Joglar et al., in preparation for an upcoming clinical investigation. They found a sensitivity of 89% and specificity of 71%.

JJ: We did the study to test the product and to look closely at 150 patients who were asymptomatic at the time (atrial fibrillation with stable rates.) The device had a sensitivity that was about 89%, which is very good. Most likely, if they had kept the device for a month, we would have had an even better sensitivity. When you have this kind of technology and you re looking to prevent catastrophic events, you want a lot of sensitivity. Sensitivity in this setting doesn't waste money. The memory on the device can be unloaded and reloaded easily. There's no downside to the patient, except making an extra phone call. In addition, by detecting more of the arrhythmias, we can help patients because stroke victims have a 20% chance of a second stroke within 1-5 years of the first one. If we can detect those patients who have atrial fibrillation when it wasn't apparent that they had it, then we can offer medications that have been proven to work and have been effective.

RJS: We released two monitors last summer. The LifeStar AF Express is a sophisticated version of the gold standard, Instromedix® King of Hearts Express®. Many physicians are familiar with it and its operation, and we felt it would be useful in many patients. It is simple to initiate, put on 2 electrodes, and begin monitoring with the patient being alerted to any arrhythmia that occurs. It has the option of manual activation, of course. The LifeStar AF+ offers more features, including 1 or 3 channels of ECG recording, extended memory and programming options, and a contact test which is lead quality verification at hookup and after each event so pauses can be accurately assessed. There have been limited attempts with auto trigger devices in the past. The frequency of false positives from artifact was so high they were not widely used. We designed and implemented several technical as well as clinical improvements in the devices and in our monitoring center to reduce the false positives considerably.

RJS: We have had numerous physician notifications resulting in immediate intervention. A 60-year-old woman had a 6-second pause and passed out as she was leaving the doctor s office. The device, which also has a visual ECG screen, was key in this immediate diagnosis. A pacemaker was implanted the same day. In fact, most of our notifications result from asymptomatic events patients would have never realized, about 33%.

RJS: LifeWatch was founded in 1993 and is a leading provider of transtelephonic monitoring services. Through mergers and acquisitions it has grown to be one of the largest service providers in the United States. One of the most interesting things about LifeWatch is that we developed and patented some of the technology that other companies are using today. LifeWatch is very technology driven and we continue to develop and patent looping monitor technology with our parent company, Card Guard ® and our sister company, Instromedix. LifeWatch provides service to about 20,000 patients a month. Our clinical staff and field sales representatives are the most dedicated, patient- and customer-friendly folks in the industry. We have two full-service, 24-hour, 7 day a week monitoring centers with state-of-the-art call center technology. We are never interrupted by adverse weather, staffing or technology issues.

RJS: Since we introduced the technology last year, we have monitored over 10,000 patients. We manage our patients very carefully. A review of our experience with the LifeStar AF auto trigger technology demonstrated the following: We looked at the first 3,030 consecutive patients enrolled at the beginning of this year, and 626 (21%) had auto triggered events with asymptomatic arrhythmias which met criteria for immediate physician notification. Fifty-three percent of those patient transmissions were asymptomatic auto-trigger events that met the same criteria for immediate physician notification. Technology to capture atrial fibrillation without patient activation has begun to change the way we look for irregular rhythms in our patients. Looping monitors are not new, and auto trigger monitors for bradycardia and tachycardia have been around for a long time. Since the introduction of our technology with patent-pending algorithms to capture symptomatic and asymptomatic AFIB and pauses, we have had higher diagnostic yield and quicker time to treatment.

RJS: There have not been any specific guidelines suggesting which device to use, continuous recorders (Holters) or intermittent event recorders with or without a memory loop. The most recent guideline was published in 1999 by ACC/AHA. It has been well documented that Holter monitors with 24- or 48-hour recording capability, have a high false negative rate secondary to sampling error and the frequency of the symptoms or arrhythmias being investigated. Event recorders have a substantially better yield as a result of the extended period of monitoring of 30 days. Event recorders provide a higher yield of concomitant recording of symptom and rhythm as well as almost immediate availability to the data 24/7. Traditionally, there have been 2 types of event recorders, loop and real time. They are differentiated by the loop memory which maintains a portion of the ECG in memory prior to patient activation. LifeWatch developed and patented the memory loop in event recorders, the LifeWatch a real time recorder in a watch, and most recently the auto trigger technology with patent-pending algorithm to detect atrial fibrillation. The question of asymptomatic arrhythmia has been a concern to many physicians when considering a choice of technology. When LifeWatch released our family of auto trigger event recorders, the choice became simpler. Auto trigger technology has all of the features of traditional looping event recorders, plus the intelligence to automatically capture clinically significant arrhythmias.

RJS: The monitors are programmable for rate and duration of each arrhythmia, including tachycardia, bradycardia, pauses (confirmed with verification of lead contact), and atrial fibrillation at any rate. Pacemaker spike detection is also available. We have several clinical advantages/indications: Syncope or near syncope: Extended monitoring period (30 days) with auto trigger for any clinically significant arrhythmia. Does not require patient activation which limited event recorders in this population before. Auto trigger without verification of the ECG contact may be false positive, secondary to lost contact. Capture asymptomatic but clinically valuable arrhythmias such as paroxysmal atrial fibrillation, patients with sick sinus syndrome, or those on anti-arrhythmic or negative chronotropic agents who may have recurring unidentified episodes of AF. Many of these patients are not anticoagulated and present with CVA. Demonstration of atrial fibrillation in patients on antiarrhythmics may suggest a change in therapy. Many patients with known paroxysmal atrial fibrillation push to discontinue anticoagulation because they are asymptomatic and don t believe they need it any longer. Monitoring the patients for 30 days with the auto trigger can help support the need for anticoagulation. Capture transition of arrhythmia. Newer therapies such as ablation are very successful at treating certain arrhythmias. Demonstration of the initiation of certain rhythms helps determine the etiology and appropriate therapy. The auto trigger technology with memory loop records the transition from normal rhythm to arrhythmia. Capture arrhythmias symptomatic or not in patients unable to activate event recorders in the time needed for traditional memory loop devices.

JJ: The capability of this technology has prompted several clinical trials to date involving the incidence of asymptomatic atrial fibrillation and the relationship of atrial fibrillation and CVA. The rapidly increasing experience nationally will certainly prompt additional studies. Our study results will be published soon. The LifeStar AF auto trigger event recorders are the most exciting technology to be offered for ambulatory monitoring in 20 years. We will continue to expand the clinical uses and functionality as we continue to provide our customers with the best technology and service in the industry.

JJ: About 25-30% of patients fail to use monitoring devices properly. Sometimes a patient will faint, or hit the floor, or be lethargic. Many things can happen during the onset of a cardiac event that would prevent them from properly recording the conditions. The auto trigger helps in accurately monitoring the patient s condition in those circumstances. What we also want to begin looking at is the monitoring of events that have not happened yet. Simple arrhythmias can lead to catastrophic consequences. For example, if you have atrial fibrillation that has not yet been detected, you can end up with a stroke. In about 12% of patients with atrial fibrillation, a stroke was the first indication of their condition. That s a very big number. What we are talking about here is progressive technology. I've been using event monitors since I was a medical student. This is technology that will enhance patient care. Using these automatic monitors enables us to get a better diagnosis from the patient. This progressive technology will allow us to not only diagnose actual events, but check for future possible occurrences before the patients are symptomatic.

RJS: Physicians, patients and payors benefit from the convenience of ambulatory ECG monitoring. Some physicians own equipment and provide service to their patients from their own offices, or they outsource to a national service provider. Patients benefit from the extended monitoring period due to infrequent symptoms and the convenience of transtelephonic data submission from their homes. Payors, Medicare or commercial, benefit from the ambulatory diagnostic capability versus a hospital stay, and the quicker diagnostic yield.

RJS: I think that it should have already. When you look at the indications for Holter, for the most part, you re looking at symptomatic patients. All of the screening criteria that they used for post bypass, and post MI, etc. to help classify higher risk patients didn't yield much. As a result, what you re using a Holter for is to try and document the symptoms that are already there. It is less effective when you consider the short time frame, the delay in getting the information to the physician, and the other limitations of Holter, which is really 40-year-old technology.

JJ: I agree. I think that Holters are a very old technology, and if you look at clinical studies, they tell you that Holters only diagnose about 8% of the patients who have arrhythmias that cause symptoms. That is really low yield.

RJS: Physicians should prescribe a device ideally suited to that patient s needs. Also, the patients should wear the device constantly until they experience one or multiple episodes of whatever they ve been symptomatic about in the past. This way, we monitor both asymptomatic and symptomatic events. We are having greater patient compliance and satisfaction with the auto trigger technology.

JJ: I think it will be useful for us to move away from technology of the sixties and eighties into the new era and take advantage of the technology we have for better patient care. What I'm interested in doing is taking a step ahead and then taking a step further by getting the arrhythmias before they even cause consequences.