Analysis of the determining factors of detectable P‐wave and amplitude of QRS complex sensed by implantable loop recorder

Background Determining factors for sufficient QRS amplitude and discernible P‐wave sensing in implantable loop recorder (ILR) are unknown. We aimed to investigate determining factors and ILR implantation angle that may improve QRS complex and P‐wave sensing in ILR. Methods We retrospectively reviewed 220 patients who underwent ILR implantation or follow‐up analysis. Patient demographic, clinical, echocardiography, electrocardiography, heart angle, and ILR angle data were collected as predictor variables. Associations between ILR QRS amplitude/P‐wave detectability and each predictor variable were investigated. Results Univariate linear regression showed that ILR QRS amplitude was significantly associated with age, height, ILR angle, and QRS amplitudes of 12‐lead electrocardiogram (ECG) (lead I, II, aVR [inverted aVR], aVF, V1–V6) and Holter ECG (lead V3, V5). Among discrete variables, only left ventricular hypertrophy (LVH) affected ILR QRS amplitude (P = .016). A multivariate linear regression analysis revealed that ILR angle (β = −0.008, P