False-Positive Patient Activations and Why Reviewing the Results of Ambulatory Monitoring With Patients is Critical

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EP LAB DIGEST. 2024;24(2):6.

Dear Readers,

After the development of Holter monitoring by Norman J Holter over 60 years ago, ambulatory monitoring has evolved considerably. We now have patch-based wireless ambulatory monitors that patients can wear for weeks and use post-acquisition signal processing based on deep learning to categorize the rhythm. Modern monitors are highly accurate and convenient to wear. Patients wear these monitors to detect clinically relevant arrythmias such as intermittent heart block, long sinus pauses, and atrial fibrillation (AF), to quantify a patient’s arrythmia burden (eg, the frequency of premature ventricular contractions [PVCs]), and to correlate symptoms with their rhythm. When ambulatory monitors are hooked up, patients are usually also given a diary for symptom entries. The diary is then used to temporally correlate their various symptoms, such as palpitations, dizziness, or syncope, with their rhythm at the time when processing the results. Current devices allow patients to manually activate the device by pressing a button on the monitor when he or she has any symptoms and log a Patient Activation Marker, which allows for more precise temporal annotation.

Ambulatory monitors collect information over a long period of time. This makes these devices different than most medical tests. And because only the electrograms are collected currently, it makes it difficult to know exactly what the patient was doing at the time that the rhythm was recorded. For example, when patients have heart block documented on their monitor, it can be difficult to determine if it is vagally mediated and benign, or pathological requiring treatment with a pacemaker. Clues that atrioventricular (AV) block found on a monitor is not pathological include the presence of AV nodal Wenckebach block around the same time, the absence of a bundle branch block, and concomitant sinus slowing associated with the heart block. Another useful piece of diagnostic information is whether the patient is sleeping at the time of heart block. This is usually not a diagnostic dilemma when the heart block is nocturnal, but how can it be determined that the patient was not taking a nap when they experienced heart block in the afternoon? For this reason, it is important to review the results of monitors with patients to determine exactly what they were doing at the time. It is possible that data from accelerometers may soon be added to the data collected from monitors to better determine if a patient was active at the time of the recording, but until then, the only way to know is to ask the patient to recall. Electrophysiologists are accustomed to this approach. For example, at times it is necessary to ask a patient with an implantable cardioverter-pacemaker or defibrillator who has evidence of electromagnetic interference recorded on their stored electrograms exactly they were doing at that moment, or what emitting objects they could have been near at the time, to help determine the source of the noise.

There are other times when it is important to review the results of ambulatory monitors with patients. Often, we rely on patient-activated events when interpreting the results of ambulatory monitoring. However, it is not uncommon that patient-activated events are accidental and erroneous. This is underappreciated. Ambulatory monitoring reports can indicate that the patient activated the device when they actually did not intentionally press the button. Recently, a 65-year-old patient with newly diagnosed paroxysmal AF was given a monitor to determine his burden and to correlate his symptoms with his rhythm. He had a very high burden of AF at 85% and 2 patient-triggered markers that correlated temporally with AF. However, when seen in clinic and asked about these events, he was very clear that he never pressed the activation button.

Although the incidence is unknown, false-positive patient activations do happen. It is possible that patients bump the button on the device during the day or roll over on it while sleeping. Therefore, it is crucial to go over the results of monitors with patients when the results are available. Otherwise, if an erroneous patient activation correlates with sinus rhythm, one might incorrectly conclude both that the patient had their symptoms while wearing the device and that the patient’s symptoms are not due to an arrhythmia. In other situations, one might erroneously conclude that a patient has symptomatic PVCs that were not symptomatic and lead to unnecessary therapy.

Despite improvements in ambulatory monitoring, it is still critical that findings be reviewed directly with the patient to accurately interpret the results and to correlate any symptoms with their rhythm at the time. Studies are needed to determine how often patients inadvertently press the activation button, how often erroneous conclusions are made based on false-positive patient-activated events, and how this limitation can be mitigated. 

Disclosures: Dr Knight has served as a paid consultant to Medtronic and was an investigator in the PULSED AF trial. In addition, he has served as a consultant, speaker, investigator, and/or has received EP fellowship grant support from Abbott, AltaThera, AtriCure, Baylis Medical, Biosense Webster, Biotronik, Boston Scientific, CVRx, Philips, and Sanofi; he has no equity or ownership in any of these companies.