Purpose: Diagnosing atrial fibrillation (AF) is highly relevant, as specific secondary prevention is of high importance. Recently, insertable cardiac monitors (ICMs) have been introduced for continuous monitoring to detect asymptomatic episodes of AF. The detection of AF remains challenging due to a relevant incidence of artifacts. This study aimed to compare the effectivity of ICM when placed in a subcutaneous or in a submuscular localization, respectively.
Methods: We retrospectively analyzed data from 30 patients undergoing pulmonary vein isolation (PVI) for AF and consecutive ICM implantation. ICMs were implanted in two locations: either subcutaneously and parasternally (SC) or under the left major pectoral muscle (SP). Interrogations were continuously retrieved using remote monitoring and during repeated visits in our outpatient clinic. The transmission protocols were scanned for detected AF, and it was ruled by two blinded investigators, if detection was correct or incorrect.
Results: Mean age was 67 ± 10 years, 56% men, 50% paroxysmal AF. In 14 of the patients, the ICM was implanted at a SC localization and in 16 patients subpectorally. R-wave amplitude was significantly higher in patents with SP implantation. There were 670 transmitted protocols including 1024 episodes detected as AF. Of these, 54% were correctly recognized as AF in the SC group. In the SP group, 85% of the recorded episodes were correctly recognized as AF (p = 0.03). The remaining episodes in both groups showed sinus rhythm with misinterpreted artifacts.
Conclusions: To improve effectiveness of detecting AF episodes, it is useful to implant subpectorally.