Key result
Right ventricular pacing significantly decreased the median R:T ratio from 7.8 at baseline to between 1.9 and 2.4 across various pacing sites (p<0.001), increasing the theoretical risk of T-wave oversensing.
Why the study?
The effect of pacing on S-ICD sensing is not well studied, with pacing hypothesized to alter R:T ratios and increase the risk of T-wave oversensing and inappropriate shocks.
Does right ventricular pacing at different sites alter the R:T ratio perceived by an S-ICD in patients undergoing electrophysiological studies?
Observational (n=47)
No
Does right ventricular pacing at different sites alter the R:T ratio perceived by an S-ICD in patients undergoing electrophysiological studies?
p-value: p=<0.001
Right ventricular pacing significantly reduces the R:T ratio perceived by S-ICD vectors, increasing the theoretical risk of T-wave oversensing and inappropriate shocks when combining leadless pacemakers and S-ICDs.
RV pacing may raise T-wave oversensing risk with S-ICDs; hypothesis-generating for leadless pacemaker combinations.
BACKGROUND: Patients with an existing subcutaneous implantable cardiac defibrillator (S-ICD) may develop a pacing indication. When transvenous pacing is not feasible, combining an S-ICD and a leadless pacemaker (LP) can be a reasonable option. There are reports of concomitant use of both devices. However, the effect of pacing on the S-ICD sensing is not well studied. We hypothesise that pacing changes R and T-wave amplitudes, causing changes in R:T ratios as perceived by a S-ICD, increasing the risk for T wave oversensing (TWO) during paced rhythm with a subsequent risk of inappropriate shocks. METHODS: This is a prospective study in patients undergoing electrophysiological studies. Participants were fitted with a Holter®, and the leads were placed to correspond to the vectors of an S-ICD. The right ventricle was paced at four positions for 10 beats each at 8 mA/2 ms. The Holter® traces were analysed, using two-way analysis of variance (ANOVA) to assess the effect of pacing on the R:T ratio. RESULTS: Forty-seven patients (age 56.02 ± 16.02, 72% male) were enrolled (81% structurally normal heart, 15% dilated cardiomyopathy, 2% ischaemic cardiomyopathy, and 2% adult congenital heart disease). Age, sex, and aetiology had no effect on the R:T ratio. Pacing caused significant changes in the R:T ratio. There was no significant difference in the R:T ratios between the pacing sites (p < 0.001). CONCLUSIONS: Pacing alters the R:T ratio significantly in most patients, theoretically increasing the risk for TWO and inappropriate shocks. Tailored programming for both devices is important for concomitant use of LPs and S-ICDs.
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ElRefai et al. (2022) conducted an observational in Patients undergoing electrophysiological studies (n=47). Right ventricular pacing vs. No pacing (baseline) was evaluated on Median R:T ratio (p=<0.001). Right ventricular pacing significantly decreased the median R:T ratio from 7.8 at baseline to between 1.9 and 2.4 across various pacing sites (p<0.001), increasing the theoretical risk of T-wave oversensing.
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