How can we identify the best implantation site for an ECG event recorder?

The aim of this study was to show how to find the preferable implantation site for an ECG event recorder (ECG-ER). We compared the quality of bipolar ECG recordings (4-cm electrode distance, vertical position) in 65 patients at the following sites: left and right subclavicular, left and right anterior axillary line (4th-5th interspace), left and right of the sternum (4th-5th interspace), heart apex, and subxyphoidal. The results were compared to the standard ECG lead II. In 30 patients, an additional comparison between vertical and horizontal ECG registrations was done using the same sites. ECG signals in five patients were compared positioning the electrodes towards the skin with turning them towards the muscle during ECG-ER implantation. The best ECG quality (defined as highest QRS amplitude, best visible P wave and/or pacemaker spike, best measurable QRS duration, and QT interval) and best agreement with the standard lead II was found in 68% on the left of the sternum, significantly less often (P < 0.001) on the right of the sternum (14.1%), left subclavicular (6.9%), apical (5.5%) and subxyphoidal (4.2%). A significantly higher QRS amplitude was measured and the P wave was more often visible in the vertical electrode position than in the horizontal position. In all five ECG-ER patients, there was a good agreement between the bipolar surface ECG at the implantation site and ECG-ER stored signals. A significant noise signal occurred in all five patients when the ECG-ER was implanted with electrodes towards the muscle. A P wave was visible in only three of those patients, but there was an insignificantly higher QRS amplitude than in ECG-ERs implanted with electrodes towards the skin. From these results, it can be concluded that the best implantation site for an ECG-ER is right or left of the sternum, positioning the electrodes vertically and towards the skin.

[Where should the implantable ECG event recorder be placed?]. / An welcher Stelle soll ein implantierbarer EKG-Event-Recorder plaziert werden?

Aim of our study was the comparison of bipolar ECG quality (with a 4 cm lead distance) at different sites within the anterior thorax to find the preferable implantation site for an ECG event recorder (ECG-ER). In 70 patients a bipolar ECG with a short electrode distance and in the vertical position was registered at the following sites: left and right subclavicular, left and right parasternal (4th-5th ICR), left and right anterior axilla (4th-5th ICR), at the heart apex and subxiphoidal. Then it was compared to the standard lead II. In 34 patients, an additional comparison between vertical and horizontal ECG registration was performed at the above mentioned sites. During implantation of an ECG-ER in 5 patients, ECG signals were compared with electrodes placed towards the skin or towards the muscle. The best ECG quality (greatest QRS amplitude, visible P-wave and pacemaker spike, measurable QT period and bundle-branch block) and the best agreement with standard lead II was found in 67% left parasternal, significant less often (p < 0.001) right parasternal (14.3%), left subclavicular (7.1%), apical (5.7%), and subxiphoidal (4.3%). In a vertical electrode position a significantly higher QRS amplitude and a more often visible P wave was found in comparison to a horizontal electrode position. In all cases, there was good agreement between bipolar surface ECG at the implantation site and ECG-ER stored signals. When the ECG-ER is positioned with electrodes towards the muscle, significant noise-signal occurred in all 5 patients. Only in 3 patients was a P wave visible, but with a slightly greater QRS amplitude than in ECG-ERs positioned with electrodes towards the skin. From these results, it is recommended to implant ECG-ERs vertically with electrodes towards the skin and in the parasternal position.