Tradition has dictated in-office application of ambulatory ECG monitors. However, there are a few studies demonstrating efficacy of tele-ambulatory ECG monitoring. A previous study in adults comparing mail-out ambulatory ECG devices to those placed in clinic demonstrated no statistically significant difference in signal noise magnitude, which is a measure of overall quality [8]. Another study made a similar comparison in ambulatory monitors picked up from lockers, self-fitted, and compared these to those placed in clinic. The quality between the two settings were not described, however patients were surveyed and 84.4% of patients self-fitted expressed satisfaction with the protocol [9]. However, to date, no study has performed an analysis in the pediatric population.
There is sparse published literature in comparing quality of ambulatory ECG tracings in pediatrics [5, 10]. However, to our knowledge there is no published data comparing the quality between in-clinic vs at-home application using the same ambulatory ECG monitoring device in pediatrics. Our study demonstrated no significant difference in artifact, based upon IRhythm’s proprietary system, between the in-clinic and mail-home Zio Patches. Additionally, the difference in percent artifact was also not statistically significant when adjusted for patient age. The average age of IC application was approximately one year older when compared to MH, though this difference in age is statistically significant, the clinical significance of this is less relevant.
An interesting finding of this study was that the percent artifact in both groups decreased with as the patients’ age increased (Fig. 1). After controlling for location, we did find lower overall rates of percent artifact with increased patient age (Fig. 2). This may be related to a number of factors, including more continuous physical activity or movement over a 24-hour period or simply less chest wall surface for the device to be placed on for infants and toddlers when compared to older children and adolescents who, excluding athletes, may be more stationary during the day with fewer waking hours overnight.
To gather a sense of missed opportunities for diagnosis in addition to financial burden, we were additionally interested in Zios that were unaccounted for due to not being returned which we simply classified as “missing”, in addition to those that went on to be repeated. We found no significant difference between the number of Zios that were missing or repeated in either the IC or MH groups. This simple fact highlighted that there is no major financial risk to the medical system or company in mailing the Zios directly to the patient.
The major limitation to our study includes that due to intellectual property constraints, the authors of this study were not privy to the specific criteria used by iRhythm to determine what signals were defined as artifact. Another limitation was that our MH cohort was not age-matched to our control group. Additionally, our internal database of all Zios prescribed did not contain data on gender, as this information would have been ideal for sex-matched controls as well. Differences in artifact between genders could theoretically be attributed to the additional breast tissue present in adolescent females. A future study could potentially add these variables to the analysis, in addition to including the ECG tracings for quality in the repeat Zio group for analysis.