A novel use of a subcutaneous implantable cardioverter-defibrillator algorithm to detect bradycardia

Figures

• 

  Figure 1. SMART Pass algorithm. A: The SMART Pass algorithm includes an additional high-pass filter (corner frequency between 8 and 9 Hz) and a roll-off rate of 20 dB/decade designed to reduce cardiac oversensing while maintaining an appropriate sensing margin of QRS complexes. The algorithm reduces the amplitude of low-frequency T waves with minimal effect on QRS amplitude to avoid undersensing of low-amplitude ventricular arrhythmias. B: Example of pre– and post–SMART Pass algorithm electrograms with substantially reduced amplitude of low-frequency T waves and minimally reduced amplitude of QRS complexes. Adapted from Boston Scientific SMART Pass Algorithm Inservice CRM-413109-AB, August 201610 (with permission).

• 

  Figure 2. Subcutaneous implantable cardioverter-defibrillator electrograms at the time of SMART Pass algorithm deactivation. The device was sensing in the Secondary vector with adequate-amplitude QRS signals. The underlying rhythm is atrial fibrillation with irregular R-R intervals and without identifiable atrial activity. Owing to a period >10 seconds of no sensed QRS, the SMART Pass algorithm was deactivated and the electrograms were stored. The black line represents the 11.5 seconds without a sensed QRS complex. Electrograms are displayed at 25 mm/s speed and 5.0 mm/mV amplitude. S = sensed ventricular event.