Accepted Manuscript Comparison of two ambulatory patch ECG monitors: The benefit of the P- wave and signal clarity Robert Rho, Mark Vossler, Susan Blancher ARNP, Jeanne E. Poole PII: S0002-8703(18)30106-6 DOI: doi:10.1016/j.ahj.2018.03.022 Reference: YMHJ 5661 To appear in: Received date: 27 September 2017 Accepted date: 19 March 2018 Please cite this article as: Robert Rho, Mark Vossler, Susan Blancher ARNP, Jeanne E. Poole, Comparison of two ambulatory patch ECG monitors: The benefit of the P- wave and signal clarity. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Ymhj(2018), doi:10.1016/j.ahj.2018.03.022 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Comparison of two ambulatory patch ECG monitors: The benefit of the P- wave and signal clarity Robert Rho MD #, Mark Vossler + MD, Susan Blancher * ARNP, and Jeanne E. Poole, MD Τ Overlake Medical Center #, Bellevue WA, Virginia Mason Heart Institute*, Seattle WA, Evergreen Health + Medical Center, Kirkland WA, University of Washington Medical Center Τ, Seattle WA Key Words: ECG, Holter, Ambulatory ECG Monitor, Syncope, Palpitations, Arrhythmias Address correspondence to: Robert W. Rho, MD FHRS FACC Overlake Hospital and Medical Clinics 1135 116 th Avenue NE, Suite 600 Bellevue, WA 98004 Robert.rho@overlakehospital.org Fax: 425-455-2620
INTRODUCTION The ambulatory ECG monitor (AEM) is integral to the diagnosis and management of cardiac arrhythmias. Direct comparison between proprietary AEM monitors have observed variations in diagnostic yield, even when the arrhythmia occurs during identical monitoring periods. 1,2 We compared the ECG signal quality and diagnostic utility of two single vector patch AEMs. METHODS This study compared two FDA approved monitors: the ZioPatch TM Monitor, Zio-XT (irhythm Technologies, Inc, San Francisco, CA) and the Carnation TM Ambulatory Monitoring, CAM TM (BDx, Inc., Seattle, WA), Figure 1. The primary outcomes of this prospective comparative study were to compare the ECG signal clarity and to determine whether there were differences in rhythm types diagnosed between the two monitors. Secondary endpoints were whether variances in the findings on the CAM or Zio-XT resulted in differences in clinical decision making and assessment of the ease of use and comfort of each monitor and. Thirty consecutive patients referred to a community cardiology practice were enrolled. Each patient had both AEMs placed at the same visit with the intent of recording for 7 days. At the end of the monitoring period, the monitors were removed at the same visit and returned to the manufacturer s reading center for processing and preparation of their standard ECG reports. Intentionally, neither company reading center was made aware that the recordings were being used in a research trial to simulate clinical realities. Rhythm adjudication AEM reports were prepared and provided to the physicians according to the standard operating procedures of each reading center. In the first phase of review, the AEM reports were reviewed by 3 cardiologists (1 cardiologist and 2 electrophysiologists) who adjudicated the Zio-XT reports in a batch then adjudicated the CAM reports in a batch. Each reviewer took an inventory of all distinct arrhythmias detected on each individual ECG report. These were then summed as totals for all CAM or all Zio reports. Arrhythmia types counted in the inventory included first degree AV block, premature atrial contractions (PACs), ectopic atrial rhythm, nonconducted PACs, PVCs, atrial tachycardia (AT), AT with 2 or more P wave morphologies, atrial flutter, junctional rhythm, nonsustained VT, SVT unknown, WCT unknown, accelerated idioventricular rhythm (AIVR), ventricular paced rhythm, AV block, and atrial fibrillation. A narrow complex arrhythmia that could not be further classified more specifically was categorized as supraventricular tachycardia (SVT) unknown. Similarly, a wide complex arrhythmia that could not be classified as VT or SVT with aberrancy was categorized as WCT unknown. Sinus tachycardia and sinus bradycardia were not counted as an arrhythmia for the purposes of this study.
During the second phase of review, two cardiac electrophysiologists rated the ECG clarity of the Zio-XT ECGs and, separately, the CAM ECGs. The ECG recordings were adjudicated as low, medium or high clarity. Low indicated that a specific rhythm could not be further diagnosed from a general category of SVT-unknown or WCT-unknown. Medium indicated that the physician reader considered the rhythm as more likely than not to be a specific SVT type, or that a WCT was more likely than not to be VT versus an SVT with aberrancy. High clarity indicated that the physician reader had a high degree of certainty in the specific rhythm diagnosis. User experience questionnaires At the time of patch application and removal, the responsible medical technician completed a questionnaire about their assessment of each device. A patient questionnaire was also administered to assess comfort and ease of use by the patient. Clinical decision making based upon AEM results The ECG diagnostic information provided by each AEM report was then reviewed by the managing physicians to assess its influence on clinical decisions. The managing physicians reported what clinical action they would recommend based upon each report for each patient. Study sponsorship and acknowledgements This was a physician-initiated study. The study was supported by an unrestricted grant from BDx. BDx also provided all of the CAMs for the study. The authors are solely responsible for the design and conduct of this study, all study analyses, and drafting and editing of the paper. RESULTS Patient Demographics Thirty consecutive patients consented to the study. Patient age was 73.1 ± 7.1 years (range: 52-87) with 20 men and 10 women. One patient was found to have no data recorded on the Zio-XT upon analysis by the Zio-XT reading center and therefore comparative ECG analysis was available for 29/30 patients. Arrhythmia inventory A total of 86.7±0.6 arrhythmias were inventoried from the Zio-XT AEM set and 121.7± 2.1 from the CAM AEM set, p<0.001. Please see Figure 2. Atrial tachycardia was the most common individual arrhythmia diagnosed and was diagnosed more frequently on the CAM than on the Zio-XT monitor (22.3±0.6 versus 8.7±3.2, p<0.001). Atrial flutter was
diagnosed more frequently on the CAM than on the Zio=XT (3±0 versus 0.67±0.58, p<=0.002). Atrial fibrillation was diagnosed in 5 patients on the CAM and in the same 5 patients on the Zio-XT. SVT unknown In a review of all of the narrow complex arrhythmias presented on the CAM reports, the physician reviewers were able to assign a specific rhythm diagnosis beyond SVT unknown. In contrast, the physician reviewers were unable to assign a specific rhythm diagnosis for SVT unknowns for one or more ECG strips on 15.7±2.2 patient Zio-XT reports. Non-sustained VT The diagnosis of NSVT was adjudicated more frequently on the CAM, 4.7±0.6 from the Zio-XT reports compared to 11.7±1.5 from the CAM reports, p<0.001. An example is shown in Figure 3. Clarity of rhythm diagnosis The ECG clarity was ranked as high in all 29 CAMs reports (100%) and on 4.5 (16%) of the Zio-XT reports (average of the 2 electrophysiologist reviewers), p<0.001. Medical Technician and Patient Questionnaires At the time of patch removal, both devices were considered user friendly. The CAM was slightly easier to attach and remove, was more stable, and was associated with less skin reaction. The patient experiences were comparable and favorable for both devices. Impact on clinical decisions When the managing physician was asked to recommend a specific clinical action based on the findings of each AEM separately, a difference in clinical decision making would have been made in 12 patients. DISCUSSION There are several important findings in our study. 1) The CAM recordings identified more episodes of atrial tachycardia, atrial flutter, and nonsustained VT compared to the Zio-XT monitor. 2) The CAM ECGs were ranked higher in clarity compared to the Zio-XT allowing physician reviewers more confidence in making a specific rhythm diagnosis. 3) Both monitors were generally easy to apply and remove and most patients had a good experience with both. 4). Differences in specific arrhythmias diagnosed between the two AEMs may result in differences in clinical decision making.
The importance of ECG clarity for specific rhythm diagnoses The ability to see the P wave is of paramount importance in making a specific rhythm diagnosis. The CAM was adjudicated to have higher ECG clarity compared to the Zio-XT. Better ECG clarity, often by virtue of being able to determine the P waves and their relationship to the QRS, led to a greater confidence in determining a specific rhythm diagnosis. Identification of specific arrhythmias is critical because important differences in clinical concerns and treatment strategies may exist. 3,4,5,6 Another finding was the difference in the number of wide complex tachycardias adjudicated as non-sustained ventricular tachycardia. An average of 7 NSVT episodes were diagnosed on the CAM reports that were not seen in any of the Zio-XT reports from the same patients. The observed difference in VT detection has important clinical implications. 7-12 Comparative data in the field. Comparative data on ECG monitors is limited. In one study, a Holter monitor detected 11 arrhythmia events that were not detected by the Zio-XT during the same 24 hour monitoring period. 1 The CAM monitor has been shown to outperform a Holter monitor during the same monitoring period threefold. 2 This is the first direct comparison study of two single vector patch AEMs. More comparative studies should be performed. Study limitations The patient sample size is small and a study with more patients may have had different results. Interpretation of ECGs is inherently subjective and accuracy is dependent upon the knowledge and experience of the individual reader. For this reason, we used multiple reviewers and averaged their rhythm adjudications. Additionally, the study could not be performed in a blinded fashion. The reporting format differs between the two monitors and identifies the source of the reports, negating blinding. To minimize unintended bias in comparisons, each physician adjudicator independently reviewed the data in separate scrambled AEM sets for each device. Company reading centers were purposefully made unaware of the research. CONCLUSIONS This study demonstrates that differences in specific rhythm diagnosis and ECG clarity may exist between commercially available patch ambulatory ECG monitors. In this study, we found higher rhythm specificity with a CAM AEM. Further comparative studies should be performed. For a more detailed description of the methods, results, and for more ECG examples from this clinical study, please refer to the electronic supplement accompanying this manuscript.
REFERENCES 1. Barrett PM, Komatireddy R, Haaser S, Topol S, Sheard J, Encinas J, Fought AJ, Topol EJ. Comparison of 24-Hour Holter Monitoring with 14-day Novel Adhesive Patch Electrocardiographic Monitoring. Am J Med. 2014; 127(1): 1-15. 2. Smith WM, Riddell F, Madon M, Gleva MJ. Comparison of diagnostic value using a small, single channel, P-wave centric sternal ECG monitoring patch with a standard 3-lead Holter system over 24 hours. Am Heart J 2017;185:67-73 3. Larsen BS, Kumarathurai P, Falkenberg J, Nielsen OW, Sajadieh A. Excessive Atrial Ectopy and Short Atrial Runs Increase the Risk of Stroke Beyond Incident Atrial Fibrillation. J Am Coll Cardiol. 2015; 66:233-241 4. AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation. Circulation. 2014;130:e199-e267. 5. Healey JS, Connolly SJ, Gold MR, et al. Subclinical atrial fibrillation and the risk of stroke. N Engl J Med. 2012; 366:120-129 6. Zado ES, Callans DJ, Gottlieb CD et al. Efficacy and Safety of Catheter Ablation in Octogenarians. J Am Coll Cardiol 2000;35:458-462 7. Baman TS, Lange DC IIg KJ, et al. Relationship between burden of premature ventricular complexes and left ventricular function. Heart Rhythm Journal. 2010; 7:865-869 8. Buxton AE, Lee KL, Fisher JD, Josephson M, Prystowski EN, Hafley, G for the MUSTT Investigators. A Randomized Study of the Prevention of Sudden Death in Patients with Coronary Artery Disease. N Engl J Med 1999; 341:1882-1890 9. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Journal of the American College of Cardiology. 2013;61:36-375. 10. Adabag AS, Casey SA, Kuskowski MA, et al. Spectrum and prognostic significance of arrhythmias on ambulatory Holter electrocardiogram in hypertrophic cardiomyopathy. Journal of the American College of Cardiology. 2005:45:697-704. 11. Monserrat L, Elliott PM, Gimeno JR, et al. Nonsustained ventricular tachycardia in hypertrophic cardiomyopathy: An independent marker of sudden death risk in young patients. Journal of the American College of Cardiology. 2003;42:873-879.
12. Marcus FI, McKenna WJ, Shrill D, et al. Diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia: Proposed modification of the Task Force criteria. Circulation. 2010;121:1533-1541
Figure Legends Figure 1 Zio-XT and CAM patch positions. (inset includes approximate location of CAM and Zio-XT overlaid on a CXR) Figure 2 Paired ECGs from the same patient s CAM and Zio-XT AEM respectively. (Note that the R-R interval/rate window spans 20 minutes before and 20 minutes after the event represented on the ECG. This is a 71 y/o male who had an AF ablation performed 6 months prior. He has normal LV function and has no symptoms on follow up. AEM was ordered to screen for asymptomatic atrial fibrillation. Figure 3 Paired ECGs from the Zio-XT and CAM reports are shown. Time stamp match and the observation of a paced beat (red asterisk) 8 beats after termination of the arrhythmia seen on both monitors confirm paired ECGs of the same event. Shown is a 23 beat run of a wide complex tachycardia in a 72 y/o male with CAD, remote myocardial infarction, sleep apnea, pacemaker programed VVI 60, and long standing persistent AF. All three physician readers adjudicated this rhythm as NSVT from the CAM report whereas none of the physicians adjudicated the rhythm as NSVT from the Zio-XT report. The annotations included on the top of the rhythm strips were those that were included in the reading center s report.
Figure 1
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