The commercial introduction of Reveal LINQ is part of the development of nanotechnologies with miniaturization of the device and the possibility of remote interrogation. The basics of operation do not significantly differ from previous platforms with automatic or patient-activated recordings. There are, however, a number of noteworthy developments. The reduction in size facilitates implantation possibilities in young children and represents a considerable cosmetic advantage with very limited scar size (<1 cm) and less noticeable lump.
The principal modification resides in the implantation technique. The device is delivered with a specific implant kit (the insertion tool is preloaded with the device) allowing a simplified mini-invasive procedure of limited duration. In short, the reduction in the size of the device allows envisioning implantation outside of traditional structures (operating room, implantation room for pacemakers). There are two optimal sites for implantation of the device allowing insertion without preoperative body surface mapping. Indeed, experience shows that these 2 positions allow sufficient tracing quality for a majority of patients.
As first choice, the recommended site is located at the fourth intercostal space, about 2 cm from the left side of the sternum at a 45° angle. If this site does not provide an acceptable tracing quality, a second site (at the fourth intercostal space, approx. 2 cm from the left side of the sternum but without an angle and therefore parallel to the septum) can be tested. The incision may be made at either end of these recommended insertion sites depending on physician preference, patient anatomy, comfort and cosmetic considerations. If for any reason (localized dermatological problem, for example) it is necessary to implant the device in a different site, it is then recommended to perform surface mapping prior to insertion in order to verify that the quality of the signal and the detection of R wave amplitude are acceptable. When an insertion site in the inframammary fold (angle 90 degrees to the sternum in the fifth intercostal space region) is proposed for cosmetic reasons, it is then necessary to validate the quality of the signals collected in pre-implantation. For this purpose, 2 ECG electrodes are positioned at 4 cm distance in order to match the electrode spacing of the device.
Once the device is positioned, it is necessary to verify the quality of the recordings. The aim is to obtain stable amplitude R waves with a minimum amplitude of 0.3 mV and a peak-to-peak R wave amplitude at least greater than twice the peak-to-peak amplitude of both T and P waves.
One of the improvements in the new implantable Holter platform (Reveal Lnq) is the increased storage capacity. In total, 57 minutes of recording can be stored with: 1) 30 minutes of patient-triggered recordings divided into 4 recordings of 7.5 minutes, three recordings of 10 minutes or two recordings of 15 minutes. Each stored symptomatic episode contains 6.5 minutes, 9 minutes or 14 minutes respectively of electrocardiograms recorded prior to activation by the patient and one minute after activation; 2) 27 minutes of automatic recordings with a maximum of 30 episodes classified as Brady, Pause or AT and AF, and up to 60 episodes classified as Tachy. When this number is reached, the data of the most recent episode will overwrite the data of the oldest episode provided that a minimum number of episodes of each type remain in memory. For each episode classified as Tachy, Brady or Pause, the device records 30 seconds of ECG prior to diagnosis and 27 seconds after diagnosis. For each episode classified as AT/AF, the device records an ECG of the first 2 minutes of the episode.
The device can automatically record 4 episode types: Tachy, Brady, Pause, AT/AF.
In order for an episode classified as Tachy to be recorded, the interval in Tachy must be shorter than the programmed interval (Interval) over a number of cycles at least equal to that programmed (Duration). In addition, very fast rates cause a Tachy episode to be recorded when 30 of the last 40 ventricular events display an interval < 260 ms. If the device shows very short intervals (<220 ms) with a very high frequency of recorded signals (number of times the signal crosses the baseline), it rejects the diagnosis of tachycardia on suspicion of the presence of noise (no episode stored in memory). The Tachy episode ends when one of the following criteria is met: a) 8 consecutive R-waves are detected with an interval greater than or equal to the programmed Tachy interval; b) the median ventricular interval is greater than or equal to the programmed Tachy interval over a 20-second period; c) no R-wave is detected over a 10-second period.
A bradycardia episode is identified when a programmable number of RR intervals is greater than a determined length (programmable). The bradycardia episode ends when one of the following criteria is met: a) four consecutive R-waves are detected with a ventricular interval less than or equal to the programmed interval; b) no R-wave is detected over a 10-second period.
The device detects a Pause (asystole) episode when the interval between 2 detected complexes exceeds the duration of the programmed pause (1.5, 3 or 4.5 seconds). The pause diagnosis is rejected if the device suspects an undersensing. When the sensitivity is programmed to 0.025 mV, 0.035 mV or 0.050 mV, a “Loss of signal” counter is incremented with each sensing of an R-wave of amplitude less than twice the programmed sensitivity, and is decremented if the Signal amplitude is greater. If the “Loss of Signal” counter is> 0 on the Vs beat before the pause is detected, the episode is rejected. A Pause episode ends after 12 detected ventricular events.
The device detects the occurrence of AT (atrial tachycardia)/AF (atrial fibrillation) episodes based on changes in ventricular rhythm using an automatic algorithm based on the sequence of variability of RR intervals during 2-minute periods. The difference between the consecutive RR intervals is plotted on a Lorenz curve. The difference between two consecutive RR intervals (ΔRRn) is plotted on the vertical axis while the difference between the previous RR intervals (ΔRRn-1) is plotted on the horizontal axis.
During an AF episode, the RR intervals are extremely irregular and uncorrelated whereas the RR interval sequences are more regular in an AT episode. The occurrence of frequent atrial or ventricular extrasystoles may cause an inappropriate recording of AF-diagnosed episodes in conjunction with a significant variability in RR cycles. Two specific algorithms can limit the number of inappropriate recordings in this setting: 1) the Ectopic Rejection algorithm seeks a density of points on the Lorenz curve evoking frequent ectopy (alternating short interval-long interval, “regular irregularities”; 2) a P-wave Presence algorithm searches for the presence of a P-wave between two R-waves. When the Ectopic Rejection algorithm is programmed to Nominal, the P-wave Presence algorithm is activated. When the Ectopic Rejection algorithm is programmed to Aggressive, the P-wave Presence algorithm and the Ectopic Rejection algorithm are activated. When the ectopic Rejection algorithm is programmed to Stop, the P-wave Presence algorithm and the Ectopic Rejection algorithm are disabled.
For tracings be sure to check our bookstore!