CRT-D devices features and algorithms

SonR is a specific sensor, located at the tip of the atrial lead (SonRtip) that picks up micro-accelerations of the heart walls to derive information pertaining to cardiac contractility. The SonR algorithm automatically determines the optimal VV and AV delays during rest and exercise by using the endocardial acceleration signal measured by the SonRtip lead. In addition, the SonR signal is recorded during tachyarrhythmia episodes to show acute variations of cardiac contractility.

The challenge for any device is to determine whether an elevated ventricular rate corresponds to a true ventricular tachyarrhythmia requiring device therapy or not (in the event that the elevated rate is not of ventricular origin). Throughout this article, we will explore how MicroPort detects arrhythmias in dual and triple chamber ICDs. Please refer also to the PARAD/PARAD+ Tech Corner article to learn how PARAD+ operates in the VT/Slow VT zones to discriminate VTs from other rhythms.

The proper detection of VT requires a specific algorithm (arrhythmia discrimination) to discriminate ventricular tachycardia from Supraventricular tachycardia (SVT) or sinus tachycardia (ST). The MicroPort core algorithms used for rhythms within the VT zone are called PARAD and PARAD+.

The fast VT zone offers the possibility to attempt painless ATP to terminate fast ventricular arrhythmias in a defined portion of the VF zone.

The ASC is an essential of sensing used in MicroPort Implantable Cardiac Defibrillators to ensure appropriate sensing for all ventricular rhythms at all rates. It dynamically adapts the sensitivity to the changing endocardial signal in an attempt to detect each and every R wave.

The WARAD is designed to monitor the atrial activity in order to discriminate pathological atrial waves (Atrial Fibrillation, Atrial Flutter, Atrial Tachycardias) from sinus P waves. This atrial discriminator uses atrial prematurity to trigger mode switching. Refer also to the Fallback Mode Switch Tech Corner article for more details on the Fallback Mode Switch algorithm.

The FMS function is designed to diagnose atrial arrhythmias and manage their occurrence using the WARAD (Window of Atrial Rate Acceleration Detection): in the event of atrial arrhythmia, FMS switches from DDD(R), SafeR™(R) or Dplus(R) pacing mode to an inhibited dual- chamber pacing mode DDI(R) to avoid prolonged ventricular pacing at a high rate for the entire duration of the sustained atrial arrhythmia.

Brady-Tachy Overlap (BTO) is a function which starts as soon as the pacing zone and the Slow VT detection zone overlap by programming the maximum pacing rate faster than the slow VT detection rate. It allows the patient to benefit from biventricular (CRT-D) and ventricular (ICD) pacing during exercise while maintaining slow VT detection and therapy if programmed.

In patients’ daily life, some clinical or device-related events need to be communicated to the physician or someone in the hospital or clinic’s team. Alerts are ALWAYS programmed through the programmer. They are triggered automatically by the device when the selected event occurs.

The Anti-PMT algorithm is intended to protect the patient from Pacemaker-Mediated Tachycardia (PMT) without reducing the atrial sensing capability of the device.

The Right Ventricular Autothreshold (RVAT) function allows automatic adjustment of the ventricular pacing amplitude, according to a threshold test performed automatically by the device at regular intervals. The aim is to maintain automatically and periodically the ventricular capture and to adapt the ventricular pulse amplitude in order to ensure safety and to save energy.

The Right Atrial Autothreshold (RAAT) function allows automatic adjustment of the atrial pacing amplitude, according to a threshold test performed automatically by the device every day. The aim is to maintain automatically and periodically the atrial capture and to adapt the atrial pulse amplitude in order to ensure safety and to save energy.

The Left Ventricular Autothreshold (LVAT) function allows automatic adjustment of the left ventricular pacing amplitude, according to a threshold test performed automatically by the device every day. The aim is to maintain automatically and periodically the left ventricular capture and to adapt the atrial pulse amplitude in order to ensure safety and to save energy.