Key result
Left 6th intercostal space ILR placement yields higher sensing amplitudes than pectoral and ventral positions.
Why the study?
Auscultation and ECG have low sensitivity for detecting sporadic cardiac arrhythmias in horses, prompting investigation into implantable loop recorders to detect atrial fibrillation across different anatomical implant sites.
Does anatomical location influence the signal quality and ability of implantable loop recorders to detect atrial fibrillation in horses?
Does anatomical location influence the signal quality and ability of implantable loop recorders to detect atrial fibrillation in horses?
p-value: p=<0.0001
Implantable loop recorders can be used to accurately detect atrial fibrillation in horses at rest, with the left 6th intercostal space providing the optimal signal quality.
ILRs enable reliable resting AF detection in horses; hypothesis-generating for veterinary use pending further validation.
BACKGROUND: Cardiac arrhythmias in horses are diagnosed by auscultation or electrocardiogram (ECG), which results in a low sensitivity for detecting arrhythmias that occur sporadically. Implantable loop recorders (ILRs) are small ECG devices placed subcutaneously, to automatically detect arrhythmias in human patients. OBJECTIVES: To test ILRs ability to detect atrial fibrillation (AF) in horses. Furthermore, we hypothesised that anatomical location of the implant site might influence signal quality. Signal quality was evaluated both during exercise and over time. STUDY DESIGN: Experimental study. METHODS: In five Standardbred mares, eleven ILRs were implanted subcutaneously in up to three different positions (Front: pectoral region, Left-6: sixth left intercostal space and Ventral: xiphoid region) and AF induced. The R- and T-wave amplitudes were measured in all positions over time during AF. AF burden automatically registered by the ILRs over a 2-month period was compared with selected Holter ECG recordings. RESULTS: All three positions had stable R- and T-wave amplitudes during the study period and were of sufficient quality to allow AF detection at rest. The position Left-6 showed significantly higher R- and T-wave amplitudes compared with the other positions. During submaximal exercise only the Left-6 position was able to record ECG signals of diagnostic quality. No position yielded diagnostic signals at maximum exercise due to artefacts. MAIN LIMITATIONS: Few horses and ILRs included and no spontaneous AF episodes were studied. CONCLUSIONS: This preliminary study indicates that ILRs can be used for AF detection in horses, but the anatomical location is important for optimal ECG quality. Despite insufficient quality during exercise, ILRs were suitable for AF detection at rest. Therefore, the ILR may be a valuable diagnostic tool for detecting paroxysmal AF in horses.
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Buhl et al. (2020) studied Atrial fibrillation in horses (n=5). Implantable loop recorder (ILR) vs. Alternative implant positions was evaluated on R-wave and T-wave amplitudes for detection of atrial fibrillation (p=<0.0001). The left 6th intercostal space position yielded significantly higher R-wave and T-wave amplitudes compared to pectoral and ventral positions (P<0.0001), allowing reliable atrial fibrillation detection at rest.
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