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 defibrillator (S-ICDTM ), several patients had inappropriate shocks from TWOS during exercise. This prompted some operators to perform routine treadmill exercise test 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-ICDTM implantation is warranted. Methods Patients undergoing S-ICDTM implantation during 10/2012 to 12/2016 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 87 patients with complete treadmill exercise test data were included in the final analysis. Majority of the patients received S-ICDTM for primary prevention. 9 % of the included patients had hypertrophic obstructive cardiomyopathy. During treadmill exercise, there was significant increase in the heart rate from rest (77 BPM ± 14) to peak exercise (133 BPM ± 14; P= < 0.0001). There was no significant difference between R-wave amplitude at rest (2 mV ± 0.77) and peak exercise (1.88 mV ± 0.94; p =0.36). Similarly, there was no significant difference between T-wave amplitude at rest (0.27 mV ± 0.19) and peak exercise (0.33 mV ± 0.23; p = 0.06). The incidence of TWOS during exercise was zero. Conclusion With current screening and detection algorithms for S-ICDTM , routine treadmill exercise does not result in additional discrimination of patients susceptible to TWOS.