The Importance of Mobile Cardiac Outpatient Telemetry (MCOT) Monitoring for the Detection of Cardiac Arrhythmias

Approximately one year earlier, the patient had an episode of atypical chest discomfort that was ultimately diagnosed as a muscular strain. As part of his work-up, he underwent a cardiac stress test and echocardiogram, both of which were read as normal. His past medical history was otherwise unremarkable except for several episodes of syncope as a teenager and young adult, but these were always associated with vasovagal events such as seeing blood or standing in a hot church. At the time of his most recent presentation, he was on no medications and denied having any allergies. There was no family history of premature coronary disease, cardiac arrhythmias or sudden death, and his social history was also benign. On physical examination the patient was normotensive without orthostasis. The head and neck exam was unremarkable, and there was no carotid hypersensitivity. His cardiac exam was regular in rhythm with normal heart sounds and no murmur or gallop. The remainder of his physical exam was normal as well, and the neurological exam was nonfocal. His resting ECG showed sinus rhythm with no conduction or repolarization abnormalities. In view of the patient's recent normal cardiovascular work-up, a neurocardiogenic etiology for the patient's lightheadedness and syncope was considered, but the severity of his symptoms was concerning enough to warrant further evaluation. An electrophysiology study was felt to be of too low a yield due to his normal cardiac function, and head-upright tilt table testing too nonspecific. Several options of long-term cardiac monitoring were considered, including Holter monitoring, event monitoring and looping event recorders. Because of the infrequency and short duration of his symptoms, the patient was referred for two weeks of mobile cardiac outpatient telemetry (MCOT). During his monitoring, an asymptomatic episode of very rapid ventricular tachycardia was recorded (Figure 1). The patient subsequently underwent an electrophysiology study, which demonstrated inducible ventricular tachycardia; therefore, a cardioverter-defibrillator was implanted. Mobile Cardiac Outpatient Telemetry The MCOT system, developed by CardioNet^®, is like Hospital Telemetry outside the hospital, monitoring patients in real-time during normal daily activities, using built-in detection algorithms and cellular technology. With 96 hours worth of memory, the system allows doctors to capture significant arrhythmic events, even when no symptoms are experienced. It has three non-invasive/stick-on electrodes that connect to a sensor, which can be worn as a pendent or on a belt clip. The sensor detects every heartbeat and relays the information via radiofrequency to the monitoring device (monitor). When detected, events are automatically transmitted to the monitoring center without patient intervention via built-in wireless cellular technology; an unlimited number of events can be recorded and transmitted. The system also allows users to quickly report any symptoms using a touch screen on the monitor. This information is reviewed by CCT-certified technicians, and then sent to the doctor via fax or Internet. For life-threatening arrhythmias, the monitoring center can immediately contact both the patient and physician. Furthermore, patient noncompliance can be remotely detected and immediately corrected. In fact, our hospital was recently involved in a large, prospective, randomized study to compare the effectiveness of MCOT with standard looping event recorders.¹ This study involved 17 enrolling centers and 300 patients presenting with symptoms suggestive of a cardiac arrhythmia who had a previous negative or inconclusive 24-hour Holter monitor. Patients were randomized to either MCOT or cardiac looping event recorders for a 30-day period. The primary endpoint of this study was the confirmation or exclusion of a probable cardiac arrhythmia as the cause of the patient's symptoms. Overall, MCOT either confirmed or excluded an arrhythmia in 88 percent of patients, compared with 75 percent of patients in the loop recorder group. In a sub-group analysis of sites using cardiac loop event recorders with an auto-detection algorithm, MCOT again was significantly better. The results of this study also showed that MCOT was almost three times more effective in detecting and diagnosing clinically significant arrhythmias compared to the frequently prescribed cardiac loop event recorder. MCOT detected clinically significant arrhythmias in 41 percent of patients, compared to the cardiac loop event recorder, which detected arrhythmias in just 15 percent of patients (p < 0.001). Similarly, in the patients with syncope or near syncope, MCOT detected clinically significant arrhythmias in 52 percent of patients, compared to 16 percent of cardiac loop event patients. In our experience, we have realized several patient and physician advantages with the MCOT system. These include a high patient compliance due to daily reporting, lack of patient dependence in capturing events, the ability to contact patients at the time of a detected arrhythmia, and having patients remain active and mobile. In addition, MCOT has been very useful in monitoring the heart rate control and burden of atrial fibrillation. In the previously mentioned trial, clinically significant atrial fibrillation was more likely to be detected in MCOT patients (23%), compared with loop recorder patients (8%). The 24-hour monitoring and two-way communication with the patient allows the physician to not only know if the patient had an episode of atrial fibrillation, but also the duration of the episode, whether or not there were any symptoms and how well the heart rate was controlled. Summary Over the past 50 years, ambulatory cardiac monitors have evolved in their sophistication, resulting in improved care and better outcomes for cardiac arrhythmia patients. Mobile cardiac outpatient telemetry is the latest advancement in this field and offers a reduction in patient error and enhanced diagnostic accuracy. MCOT has proven to be superior in the detection of clinically significant arrhythmias, with a shorter time to diagnosis, and should be considered as a first-line diagnostic tool when monitoring patients for clinically significant arrhythmias.