Originally loop recorders were usually implanted at the fourth intercostal space with the long axis ... read more ↘ of the loop recorder parallel to the midline of the body. This implant location would adequately detect R waves, but was often inadequate for recording P waves. In an effort to record better P waves we began implanting loop recorders at the third intercostal space with the long axis of the device oriented parallel to the long axis of the heart. We have found that this implant technique allows us to better visualize the P waves. Visualizing P waves is critically important in reaching the correct diagnosis in cases of paroxysmal tachycardia. It is even more important in avoiding false diagnoses of atrial fibrillation. Various rhythm disturbances such as frequent PACs, multifocal atrial tachycardia, and sinus arrhythmia may be falsely identified as atrial formulation by the detection algorithms used by implantable loop recorders. It is therefore critical to evaluate the electrocardiogram recordings, and to be able to adequately visualize P waves. Another cause for false diagnosis of atrial fibrillation by loop recorders is noise. Noise is most troublesome immediately after implant. One of the keys to avoiding a noisy signal is to have a pocket, which is very tight on the loop recorder. We have found that using the plastic handle of a disposable scalpel makes an ideal pocket. We implant at the third intercostal space just to the left of the sternal border. We implant the device, directed rightwards and superiorly. ↖ read less
