Role of exercise electrocardiogram to screen for T-wave oversensing after implantation of subcutaneous implantable cardioverter-defibrillator

Abstract

Background: During early experience with subcutaneous implantable cardioverter-defibrillators (S-ICD), several patients had inappropriate shocks from T-wave oversensing (TWOS) during exercise. This prompted some operators to perform routine treadmill exercise tests after implantation of S-ICD to screen for TWOS. Meanwhile, improvements have been made in the detection algorithms by the manufacturer.

Objective: To assess whether routine treadmill exercise post S-ICD implantation is warranted.

Methods: Patients undergoing S-ICD implantation from October 2012 to December 2016 who were able to complete a treadmill exercise were included in the study. The amplitude of R and T waves as assessed by the device programmer at rest and peak exercise was calculated and incidence of TWOS recorded.

Results: Eighty-seven patients with complete treadmill exercise test data were included in the final analysis. The majority of the patients received S-ICD for primary prevention. Nine percent of the included patients had hypertrophic obstructive cardiomyopathy. During treadmill exercise, there was significant increase in the heart rate from rest (77 ± 14 beats per minute) to peak exercise (133 ± 14 beats per minute; P < .0001). There was no significant difference between R-wave amplitude at rest (2 ± 0.77 mV) and peak exercise (1.88 ± 0.94 mV; P = .36). Similarly, there was no significant difference between T-wave amplitude at rest (0.27 ± 0.19 mV) and peak exercise (0.33 ± 0.23 mV; P = .06). The incidence of TWOS during exercise was zero.

Conclusions: With current screening and detection algorithms for S-ICD, routine treadmill exercise does not result in additional discrimination of patients susceptible to TWOS.

Keywords: Defibrillator; Exercise electrogram; Subcutaneous defibrillator; Sudden cardiac death; T-wave oversensing.