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

<b>Background:</b> In total, 6.6% to 11% of patients with an initially implanted implantable cardioverter-defibrillator (ICD) will develop significant bradycardia and the need for pacing in subsequent years. As the leadless pacemaker (LP) and subcutaneous implantable cardioverter-defibrillator (S-ICD) population comorbidities are often similar, both groups would benefit from a hybrid solution. Unfortunately, currently, there is no commercially available and sufficiently validated interconnected set of S-ICD and LP. <b>Methods:</b> In this single-center, prospective observational study, 32 pacing-dependent patients after implantation of a Micra LP were screened for S-ICD on the left and right sides of the sternum using the EMBLEM Automated Screening Tool. At least one positive, both in the supine and standing positions, was considered a positive screening. The impact of various clinical variables and morphology of paced QRS on screening results was assessed. Moreover, the function of the tricuspid valve was evaluated before and after LP implantation to consider whether there is a relationship between paced QRS and worsening tricuspid regurgitation. <b>Results:</b> Patients with paced heart rhythm were divided into two groups based on screening results for S-ICD. The positive screening outcome was achieved in 10 patients (31.25%). No correlation between any clinical variable and screening results was found. However, right axis deviation [RAD] of paced QRS seems to be a strong predictor of positive S-ICD screening (RAD in 9/32 patients, sensitivity 90%, specificity 100%, PPV 100%, NPV 96% for passing screening), and negative polarity of paced QRS in inferior leads predicts negative screening results (positive polarity in II, III, and aVF in 12/32 patients, sensitivity 100%, specificity 90%, PPV 83%, NPV 100% for passing screening). <b>Conclusions:</b> Right axis deviation of the paced rhythm, positive QRS polarity of leads II, III, and aVF, and negative QRS polarity in leads I and aVL seem to predict a positive screening result for S-ICD. Such a position of LP does not seem to worsen tricuspid regurgitation.