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

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 (77614 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.