Background Suitability for the subcutaneous implantable cardioverter-defibrillator (S-ICD) depends on a pre-implant electrocardiogram (ECG) screening to ensure appropriate sensing of electrical cardiac signals. Screening is performed positioning electrodes guided by chest surface anatomical landmarks. Case summary We report a case of a patient with an initially negative conventional automatic screening for S-ICD, who underwent a modified screening guided by cardiac silhouette position, as seen under fluoroscopy, resulting in eligibility for the S-ICD. Discussion The S-ICD reduces endovascular infection risk, providing therefore a potentially safer alternative in patients with prosthetic valves. It might be reasonable to perform a pre-implant ECG screening guided by fitting the cardiac silhouette in the shock vector, as this modified screening position could increase eligibility in patients who may benefit from S-ICD therapy such as the one presented.

Aims: The subcutaneous implantable cardioverter-defibrillator (S-ICD) requires screening prior to implantation. Surface anatomical landmarks (SAL) guide the screening. The heart silhouette shows variations, therefore, these landmarks may differ. We aimed to determine the concordance between SAL and fluoroscopy guided screening, and analyze discordance predicting factors. Methods: We performed a conventional SAL guided screening (CS) in left and right parasternal electrode position (LPP/RPP) to candidates for S-ICD. Subsequently, we performed a fluoroscopy guided screening (FGS) according to cardiac silhouette. Screenings in which at least the result of one sensing vector did not coincide were considered “discordant”. A comparison was done between discordant vs. concordant cases. A simple binary logistic regression analysis was performed to assess the risk of being discordant individually for each of the variables. Results: The results of CS and FGS were compared in 110 patients (220 comparisons: 110 LPP and 110 RPP). 90 (40.91%) were discordant in at least one sensing vector (46 in LPP and 44 in RPP). In 3 patients (2.73%) the indication of which type of defibrillator was implanted changed according to the FGS. There were no significant differences between the discordant and concordant screening patients. Conclusion: There is a level of discordance between CS and FGS. There were no analyzed factors that were able to predict discordance between these two screening methods. It might be reasonable to perform FGS before implant.

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