Utility and feasibility of intra-pocket mapping technique for optimal subcutaneous implantable cardioverter defibrillator implantation positioning for R-wave detection: a case series

Figures

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  Figure 1. Examinations of Patient 1. (A) Venogram showing stenosis of the superior vena cava (arrow) where the transvenous leads were passed. (B) Fifteen-lead electrocardiogram showing complete right bundle branch block, low R-wave amplitude, and negative T-wave inversions in leads V1–4. (C) Computed tomography image after a subcutaneous implantable cardioverter defibrillator implantation. The cardiac anatomical axis is determined as the line connecting the summit of the inferior pyramidal space (circle) and the apex of the left ventricular apex (star). Subcutaneous implantable cardioverter defibrillator generator relocation to the slightly antero-inferior position improved the detected R-wave amplitude owing to the secondary vector proximity to the cardiac anatomical axis.

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  Figure 2. Schematic diagram of intra-pocket electrical mapping and secondary vector electrograms of Patient 1. First, we implanted a generator at Position 4. However, a sensing test failed because of low R-wave amplitude and R/T ratio. We tried intra-pocket electrical mapping at six generator implantation positions. Finally, the highest R-wave amplitude and an R/T ratio were obtained at Position 1. Manually measured R-wave amplitude and R/T ratio at Position 1 were higher than those at Position 4.

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  Figure 3. Chest X-rays of postero-anterior and lateral views after subcutaneous implantable cardioverter defibrillator implantation. The subcutaneous implantable cardioverter defibrillator generators are implanted anterior (A: Patient 1) and posterior (B: Patient 2) from the mid-lateral line (vertical line), respectively. According to the generator positions, the PRAETORIAN scores are different between Patients 1 (120) and 2 (60).

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  Figure 4. Examinations of Patient 2. (A) Intracardiac electrogram of the transvenous implantable cardioverter defibrillator records right ventricular lead noises (arrows) when the patient shook his arms. (B) Fifteen-lead electrocardiogram showing a short QTc interval of 330 ms and a high T-wave amplitude. (C) Computed tomography image after subcutaneous implantable cardioverter defibrillator implantation. The cardiac anatomical axis is determined as the line connecting the summit of the inferior pyramidal space (circle) and the apex of the left ventricular apex (star). Subcutaneous implantable cardioverter defibrillator generator relocation to the slightly antero-inferior position improved a detected R-wave amplitude owing to the primary vector proximity to the cardiac anatomical axis. RV, right ventricular.

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  Figure 5. Schematic diagram of intra-pocket electrical mapping and primary and secondary vector electrograms of Patient 2. First, we implanted a generator at Position number 3. However, the sensing test failed due to T-wave over-sensing. We tried intra-generator pocket mapping at five positions using an analyser cable and a pacemaker programmer (Medtronic Inc.). For the evaluation, red-coloured positive clip of the analyser cable was connected to proximal (primary vector) and distal (secondary vector) parts. The black-coloured negative clip of the analyser cable was connected to the serratus anterior muscle of each position numbered from 1 to 5, and the R-wave amplitude and R/T ratio were measured. Finally, an acceptable R/T ratio was obtained, and automatic setup using an S-ICD programmer (Boston Scientific) was passed only at Position number 1 (primary vector).