Left Axillary Implantation of Loop Recorder versus the Traditional Left Chest Area: A Prospective Randomized Study

The Evolving Role of Insertable Cardiac Monitors in Patients with Congenital Heart Disease

Insertable cardiac monitors (ICMs) have been used more frequently and in a wider variety of circumstances in recent years. ICMs are used for symptom-rhythm correlation when patients have potentially arrhythmogenic syncope and for less traditional reasons such as rhythm surveillance in patients with genetic arrhythmia syndromes or other diseases with high arrhythmia risk. ICMs have good diagnostic yield in pediatric patients and in adults with congenital heart disease and have a low rate of complications. Implantation techniques should take patient-specific factors into account to optimize diagnostic yield and minimize risk.

Changes in R-wave amplitude at implantation are associated with gender and orientation of insertable cardiac monitor: observations from the confirm Rx™ body posture and physical activity study

Background

Insertable cardiac monitors (ICMs) are small subcutaneously implanted devices that detect changes in R-wave amplitudes (RWAs), effective in arrhythmia-monitoring. Although ICMs have proven to be immensely successful, electrical artefacts are frequent and can lead to misdiagnosis. Thus, there is a growing need to sustain and increase efficacy in detection rates by gaining insight into various patient-specific factors such as body postures and activities.

Methods

RWAs were measured in 15 separate postures, including supine, lying on the right-side (RS) or left-side (LS) and sitting, and two separate ICM orientations, immediately after implantation of Confirm Rx™ ICM in 99 patients.

Results

The patients (53 females and 46 males, mean ages 66.62 ± 14.7 and 66.40 ± 12.25 years, respectively) had attenuated RWAs in RS, LS and sitting by ~ 26.4%, ~ 27.8% and ~ 21.2% respectively, compared to supine. Gender-based analysis indicated RWAs in RS (0.32 mV (0.09–1.03 mV), p < 0.0001) and LS (0.37 mV (0.11–1.03 mV), p = 0.004) to be significantly attenuated compared to supine (0.52 mV (0.20–1.03 mV) for female participants. Similar attenuation was not evident for male participants. Further, parasternally oriented ICMs (n = 44), attenuated RWAs in RS (0.37 mV(0.09–1.03 mV), p = 0.05) and LS (0.34 mV (0.11–1.03 mV), p = 0.02) compared to supine (0.48 mV (0.09–1.03 mV). Similar differences were not observed in participants with ICMs in the 45°-relative-to-sternum (n = 46) orientation. When assessing the combined effect of gender and ICM orientation, female participants demonstrated plausible attenuation in RWAs for RS and LS postures compared to supine, an effect not observed in male participants.

Conclusion

This is the first known study depicting the effects on RWA due to body postures and activities immediately post-implantation with an overt impact by gender and orientation of ICM. Future work assessing the cause of gender-based differences in RWAs may be critical.

Trial registration: Clinical Trials, NCT03803969. Registered 15 January 2019 – Retrospectively registered, https://clinicaltrials.gov/NCT03803969

Revisiting where to apply preimplant mapping to improve P-wave sensing of insertable cardiac monitors

Background

Insertable cardiac monitors (ICMs) are used for long-term cardiac rhythm monitoring. They have proven useful in diagnosing arrhythmias. They are conventionally inserted at the 4th intercostal space without preimplant mapping.

Method

We develop a new method, VisP, that finds an optimal insertion position by applying the lightweight preimplant mapping to nine candidate positions beyond the conventional ones. We retrospectively analyze consecutive 60 patients who underwent ICM insertion (Reveal LINQ™) between April 2019 and March 2021 and compare the two groups with and without VisP.

Results

After 9 patients were excluded because of ectopic atrial rhythms or atrial fibrillation, 51 patients were analyzed. Thirty-one patients underwent the conventional insertion (non-mapping), whereas 20 patients underwent VisP. VisP achieved large P-wave amplitudes while retaining the R-wave amplitude for all patients; in contrast, P waves were not detected for 11 patients out of the 31 patients in the non-mapping group (35%). On average, the P-wave amplitude was 0.065 mV for VisP, compared to 0.029 mV for the non-mapping group (p-value< .001). The average R-wave amplitude was 0.69 mV for VisP and 0.71 mV for non-mapping (p-value = .88), indicating the R-wave difference is insignificant between the two groups. VisP selected the 4th, 3rd, and 2nd intercostal spaces for 7, 11, and 2 patients, respectively, meaning that 13 out of the 20 cases (65%) fell out of the conventional insertion location of the 4th intercostal space.

Conclusions

VisP improves the diagnostic ability of ICMs by finding an optimal position that yields reliable sensing of P waves while keeping high R-wave sensing.

[Implantable ECG monitors]

Implantable loop recorders are a diagnostic tool for detecting cardiac arrhythmias and are independent of the patient's compliance. Automatic algorithms lead to a preselection of arrhythmic events that are transferred by telemonitoring to the cardiac specialists. This article describes the available loop recorders on the market, the respective implantation techniques, the indication, and reimbursement.

Advanced Cardiac Signal Recording

Implantable loop recorders allow prolonged and continuous single-lead electrocardiogram recording, with the pivotal addition of remote monitoring. They have significantly shortened time to electrocardiographic diagnosis and appropriate therapy of many bradyarrhythmias/tachyarrhythmias and proved helpful in arrhythmia burden definition, offering invaluable information in the diagnostic workup for syncope and atrial fibrillation. Advanced cardiac signal recording is also possible by transesophageal catheters. They have been used to orient diagnosis during wide and narrow QRS complex tachycardias and also to perform minimally invasive pacing. Intracardiac electrophysiologic study remains, however, essential for diagnosis of several arrhythmias in the perspective of curative catheter ablation.

[Indications for loop recorder implantation for syncope]

Implantable loop recorder with discontinuous ECG recording enables monitoring of heart rhythm over several years. Consequently, in patients with recurrent syncope it is possible to record an ECG during the next syncopal event to obtain symptom-ECG correlations. In patients with recurrent syncope of unknown origin, the implantation of a loop recorder leads to an earlier diagnosis and an asystole is more often detected as the cause of the recurrent syncope. In addition, the loop recorder identifies patients who will benefit from pacemaker implantation. An established indication for early implantation of a loop recorder is given in patients with recurrent syncope and no high-risk marker, e. g., reduced left ventricular function, valve disease, history of myocardial infarction or ECG findings such as bifascicular block, pre-excitation, long QT syndrome or an epsilon wave. These patients should receive a complete cardiological work-up with the aim of detecting the underlying heart disease. Patients with no conclusive findings should also receive a loop recorder. A relative indication is given for patients with recurrent syncope and injuries in order to predict the effect of pacemaker implantation. Possible indication is given for patients with transient loss of consciousness to rule out an arrhythmogenic origin.

Sensing performance, safety, and patient acceptability of long-dipole cardiac monitor: An innovative axillary insertion

BACKGROUND

The recommended location for implantable cardiac monitor (ICM) insertion is the left pectoral region. We tested whether an innovative left axillary implantation approach could be applicable for a new ICM, characterized by a long sensing dipole.

METHODS

We considered a series of 55 patients consecutively implanted with a long-dipole ICM (BioMonitor 2); the first 30 subjects underwent prepectoral location insertion, while the subsequent 25 received the ICM in the axillary region. Sensing performances collected at 1-month follow-up were compared between the two groups. During the visit, each patient was also asked to fill in a brief questionnaire to assess patient acceptability of the device.

RESULTS

All patients had a successful insertion of ICM. Mean R-wave amplitude was 0.87 ± 0.44 mV in the prepectoral group and 1.00 ± 0.45 mV in the axillary one, without any significant difference. The percentage of patients with visible P wave was also comparable between the two approaches (65.5% vs 68.2%, P = 0.84). None of the patients reported device-related issues or discomfort, and ICM was generally well accepted and tolerated by all the involved patients.

CONCLUSION

Axillary insertion may represent a valid alternative to the standard one for long-dipole ICM technology providing not only patient acceptability but also high-quality sensing performances.

The Role of Implantable Cardiac Monitors in Atrial Fibrillation Management

Continuous heart rhythm monitoring using implantable cardiac monitors (ICMs) for atrial fibrillation (AF) management is steadily increasing in current clinical practice, even in the absence of an established indication provided by international guidelines. The increasing use of such devices is mainly associated with recent technological improvements including miniaturization, easier implant procedures, and remote monitoring, all of which make this strategy continuously more appealing and promising. For these and other reasons, ICMs have been proven to be a safe and highly effective tool for detecting AF episodes. However, ICMs are not the best option for every patient, as limitations exist. Therefore, it is imperative to weigh the possible benefits against the potential limitations of using these devices when deciding individualized patient care.