Clinical Impact Analysis
To assess the downstream clinical impact of selecting a subset of EGMs for review, the following primary measures were calculated for each arrhythmia type:
(1a) Total EGM burden reduction (count of key EGMs, as a percent of all EGMs). (1b) EGM burden reduction per patient per month (count of key EGMs, as a percent of all EGMs, calculated per patient per month of transmission history). (1c) TP day reduction (patient-days with at least one TP key EGM, as a percent of all patient-days with at least one TP EGM). (1d) Proportion of patients with no diagnostic delay (count of patients in which a TP key EGM occurred on the first day that any TP EGM was exhibited, as a percent of all patients with at least one TP EGM).
While the total EGM burden reduction may be translated to clinics with large patient populations, the per patient EGM burden reduction can help characterize the EGM volume distribution across the population.
As expected, reviewing fewer EGMs comes with the risk of potentially neglecting diagnostically valuable TP EGMs. However, multiple, redundant TP EGMs captured on the same day may not speed up the diagnosis. Therefore, the risk of reviewing fewer EGMs was quantified by the loss of patient-days when at least one TP EGM was prioritized for review and, thus, a diagnosis could have occurred (i.e., TP day reduction), rather than directly quantifying the reduction in total TP EGM count.
The clinical impact of lost TP days, however, ultimately depends on their distribution across the population and within each patient. In other words, if a patient’s diagnosis is assumed to occur on the first TP day at the earliest, failing to prioritize any TP EGM that day would delay that diagnosis. In contrast, prioritizing a TP EGM on the first day a TP EGM exists (i.e., the first TP day), but skipping subsequent TP days for that patient, would not delay the diagnosis. In addition to the proportion of patients with no diagnostic delay, the following secondary measures were calculated for patients with a diagnostic delay introduced by selecting key EGMs:
(2a) Proportion of patients experiencing a diagnostic delay(count of patients in which a TP EGM was eventually prioritized for review, but not on the first day a TP EGM was exhibited, as a percent of all patients with at least one TP EGM). (2b) Diagnostic delay value (for all patients with a diagnostic delay, the number of days between the first TP EGM exhibited and the first TP key EGM).
Schematics illustrating the EGM reduction, TP day reduction, and potential diagnostic delay resulting from key EGM selection are provided in Figure 1 .
To further explore the clinical impact of selecting key EGMs for review, the above metrics were also calculated for the subpopulation of “high EGM-volume patients”, defined as the subgroup of patients in the top 25th percentile of EGMs/patient/month (EGMs/pt/mo) for each arrhythmia type.