Left and Right Parasternal Sensing for the S-ICD in Adult Congenital Heart Disease Patients and Normal Controls

Background: This study investigated the impact of a right parasternal sensing electrode position on the R- and T-wave amplitudes and the R:T ratio in three subcutaneous implantable cardioverter defibrillator (S-ICD) vectors in patients with adult congenital heart disease (ACHD) and normal controls.

Methods: Conventional left parasternal sensing electrode position and right parasternal sensing electrode positions were used to collect 10-second electrograms, recorded through an 80-electrode body surface mapping technology (Prime ECG™ system, Heartscape Technologies Inc., now Verathon, Columbia, MD, USA). Recordings were made in the supine, prone, left lateral, right lateral, sitting, and standing positions in using both the standard electrode vector position and the right parasternal positions.

Results: Forty patients were recruited and 37 patients were used for analysis. Twenty-seven (73%) had complex ACHD; 10 patients had normal hearts and acted as controls. A total of 3,708 data points were analyzed. There were no significant differences in the R:T ratio when measured in ACHD patients in the right compared to the left parasternal lead position. In contrast, there were important differences in the magnitude of the R:T ratio when measured in control patients in the right compared to the left parasternal lead position; in the primary vector, the R:T ratio was greater in right than left by 2.99 (P = 0.0002; 95% confidence interval [CI]: 1.48-4.50) and in the secondary vector, the R:T ratio was smaller in the right than in the left by 0.77 (P = 0.004; 95% CI: -1.58-0.05).

Conclusion: In selected patients, a right parasternal lead position may provide a useful alternative sensing configuration for the S-ICD.