Proper QRS for EMBLEM S-ICD Across Micra Recipients-Pilot Study.

It was already known that approximately 6.6% to 11% of individuals initially receiving an implantable cardioverter-defibrillator (ICD) eventually require pacing due to significant bradycardia development over subsequent years. Clinical populations requiring leadless pacemakers (LP) and subcutaneous implantable cardioverter-defibrillators (S-ICD) frequently overlap because of shared comorbidities like heart failure or advanced age. Integrating these two distinct technologies offers a potential hybrid solution for complex cardiac management without the risks associated with transvenous leads. Current medical technology lacks a commercially available, sufficiently validated interconnected system combining these specific devices for widespread clinical use. Clinicians must ensure that the electrical signals from the pacemaker do not interfere with the sensing capabilities of the defibrillator to prevent inappropriate shocks. The interaction between the intraventricular pacing stimulus and the subcutaneous sensing vectors remains a primary concern for patient safety. This absence of evidence motivated a prospective investigation into how paced rhythms influence the eligibility for subcutaneous defibrillation systems.

Researchers evaluated the feasibility of using the EMBLEM subcutaneous implantable cardioverter-defibrillator in patients already utilizing a Micra leadless pacemaker to ensure sensing compatibility. The investigation focused on identifying specific clinical variables or electrocardiographic patterns that predict successful device screening in this unique patient cohort. Investigators sought to determine if the morphology of the paced QRS complex dictates the compatibility between these two cardiac devices during various physical activities. The team examined whether the physical position of the leadless pacemaker within the heart affects tricuspid valve function or leads to mechanical complications. This pilot study aimed to establish a predictive framework for clinicians considering hybrid pacing and defibrillation therapy for their patients. Identifying these predictors helps streamline the patient selection process for dual-device implantation while minimizing the risk of sensing failures. The study also sought to clarify if patient-specific factors like body mass index or age influenced the screening success rate.

This single-center prospective observational study enrolled 32 pacing-dependent individuals who had previously undergone Micra leadless pacemaker (LP) implantation for various indications. Each participant underwent screening for the EMBLEM subcutaneous implantable cardioverter-defibrillator (S-ICD) using the EMBLEM Automated Screening Tool to assess signal quality. Technicians performed these assessments on both the left and right sides of the sternum while patients remained in supine and standing positions to capture postural variations. A positive screening required at least one successful vector in both physical orientations to ensure sensing reliability across different physiological states. The research team analyzed various clinical parameters and the specific morphology of the paced QRS complex to find correlations with screening outcomes. Echocardiographic evaluations of the tricuspid valve occurred before and after pacemaker placement to monitor for worsening regurgitation or structural damage. Statistical frameworks were applied to calculate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of various QRS axis deviations.

Successful screening for the subcutaneous defibrillator occurred in only 31.25% of the study population, representing 10 out of 32 patients who met the criteria. Right axis deviation (RAD) of the paced QRS complex emerged as a powerful predictor of positive screening results with a sensitivity of 90% and specificity of 100%. Positive polarity in the inferior leads, specifically leads II, III, and aVF, demonstrated 100% sensitivity for passing the automated screening process in this group. Negative polarity of the paced QRS in the inferior leads consistently predicted a failure to meet the screening criteria during the evaluation. Statistical analysis revealed no significant correlation between standard clinical variables like age or gender and the likelihood of a successful screening outcome. The placement of the leadless pacemaker did not cause a significant increase in tricuspid regurgitation among the participants according to the echocardiographic data. These findings highlight that the electrical vector of the paced rhythm is more significant than patient demographics for device compatibility.

Specific electrocardiographic markers such as right axis deviation and positive QRS polarity in inferior leads effectively identify candidates for hybrid device therapy involving leadless systems. Clinicians can utilize these QRS morphology patterns to predict the compatibility of the EMBLEM system with existing leadless pacing before attempting implantation. The findings suggest that the intraventricular position of the Micra device does not negatively impact valvular integrity or cause significant tricuspid regurgitation. Future research should focus on validating these predictors in larger, multi-center cohorts to refine patient selection algorithms for hybrid cardiac rhythm management. These results provide a foundation for developing integrated pacing and defibrillation protocols in high-risk cardiac populations who cannot tolerate transvenous leads. Understanding these electrical interactions is essential for the safe implementation of leadless hybrid technologies in modern electrophysiology practice. The study confirms that while compatibility is limited, specific electrocardiogram (ECG) features can reliably guide clinical decision-making for these complex patients.