The risk of failure of subcutaneous implantable cardioverter defibrillator therapy: from PRAETORIAN score to clinical practice.

AIMS: The subcutaneous implantable cardioverter defibrillator (S-ICD) is an alternative to traditional ICDs. The PRAETORIAN score, based on chest radiographs, has been validated to predict the probability of successful S-ICD defibrillation testing by assessing factors like fat thickness between the coil and sternum and generator placement. This study evaluated the correlation between the PRAETORIAN score and clinical characteristics, as well as implantation variables.

METHODS AND

RESULTS

We retrospectively analysed data from 1253 patients who had undergone implantation of an S-ICD across 33 centres. The intermuscular positioning of the pulse generator was adopted in all patients. Post-implantation posterior-anterior and lateral chest radiographs were analysed to calculate the PRAETORIAN score. A total of 95.7% of patients had a PRAETORIAN score < 90, indicative of a low risk of conversion failure. Body mass index (BMI) was the only independent predictor of a score ≥ 90, and all patients with BMI < 25 kg/m2 (normal weight or underweight) had a score < 90. The intermuscular positioning technique resulted in optimal posterior placement of the device in all patients and significant sub-generator fat in only 3% of cases. A shock impedance value > 88 Ohm enabled to detect a PRAETORIAN score ≥ 90 with 98% (95% CI 97-99%) negative predictive value.

CONCLUSION

In contemporary practice, the PRAETORIAN score can be simplified. By adopting an intermuscular approach, two of the three steps of the score-evaluating the adequate posterior positioning of the generator and measuring the sub-generator fat-become superfluous, and impedance may serve as a reliable surrogate of sub-coil fat thickness. Furthermore, our data suggest that for non-obese patients, a favourable PRAETORIAN score is assured, making the score evaluation potentially unnecessary.

CLINICAL TRIAL REGISTRATION: URL: http://clinicaltrials.gov/ Identifier: NCT02275637.