Automatic subcutaneous defibrillator screening in patients with intracardiac devices: comparative study depending on the point of pacing

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND/INTRODUCTION: Subcutaneous defibrillator (S-ICD) has been shown to be effective in the prevention of sudden cardiac death with the advantage of avoiding intravascular access. Although it should not be indicated when pacing indications exists, the need for pacing may arise in the course of underlying heart disease. Before implantation, it is necessary to screen the surface electrocardiogram (ECG) to avoid inappropriate shocks due to overdetection. Published studies so far show a drastic reduction in the percentage of patients eligible for screening with conventional pacing techniques (right ventricular apex, right ventricular outflow tract or resynchronisation with coronary sinus pacing). PURPOSE: The change in screening signal produced by cardiac pacing during is unknown. So far, no studies have been published comparing the outcome of S-ICD screening between different pacing sites, including conduction system pacing (CSP, his and left bundle branch pacing). Our aim is to analyse the success rate of screening and its predictors in patients with cardiac pacing according to the pacing point. METHODS: A total of 102 patients were screened for S-ICD and divided into 5 groups according to pacing type: His bundle pacing (HBP), left bundle pacing (LBP), right ventricular apex (RVA), right ventricular outflow tract (RVOT) and biventricular cardiac resynchronisation (CRT). There were no significant differences in any variable between the HBP and LBP group, so they were unified as the CSP group. We used a control group of 10 healthy patients with no implantable devices or ECG abnormalities. All patients underwent automatic screening with paced rhythm using the automatic algorithm (Boston Scientific). We considered a suitable screening when at least one vector (primary, secondary or alternative) was positive in both decubitus and standing position, in left or right parasternal position. RESULTS: Baseline characteristics by group are summarised in table1. Paced QRS width was lower in the CSP group (135 [120-160] vs 120 [106-120] p=0,001). All healthy controls passed the screening (100%). 39 (97.5%) CSP patients passed the screening, compared to 15 (71.4%) CRT, 14 (70%) RVOT and 4 (19%) RVA. The differences were statistically significant, p < 0.001 (image 1 A & B). In multivariate analysis, only pacing type was shown to be a predictor of positive screening (p 0.001), independent of paced QRS width. CONCLUSIONS: In our experience, the probability of obtaining a positive screening of the S-ICD is higher with conduction system stimulation than with the other pacing points (AVD, RVOT or CRT). [Figure: see text] [Figure: see text]