Ventricular Sense Response (VSR) Feature
Optimal CRT therapy for heart failure patients requires that they recieve biventricular pacing for as much of the time as possible. Biventricular pacing may be interrupted by ventricular sensed events and fast ventricular rates related to AF. Interruption of biventricular pacing may lead to patient symptoms and may diminish the overall effectiveness of the therapy. Ventricular Sense Response (VSR) is designed to help the device maintain CRT pacing in the presence of ventricular sensing.
This feature can be found in some Medtronic CRT-P and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
Ventricular Sense Response is nominally On in Medtronic’s CRT-D and CRT-P devices. It can be programmed On or Off by selecting Params -> Pacing… -> Arrhythmia/Post Shock… -> V. Sense Response.
The maximum allowed pacing rate can be programmed by selecting “Additional V Settings…” from the Arrhythmia Interventions screen.
Ventricular Sense Response is available in both nonatrial tracking (DDIR, VVI, etc.) and atrial tracking pacing modes (DDDR). In a nontracking mode, a sensed right ventricular event below the maximum rate triggers an immediate ventricular pacing pulse. In a tracking mode, a sensed right ventricular event during the AV interval triggers an immediate ventricular pacing pulse. Ventricular Sense Response pacing pulses are delivered based on the current programmed CRT parameters.
If the ventricular interval measured from the preceding ventricular event is shorter than the programmed Maximum Rate interval, no Ventricular Sense Response pacing pulse is delivered. Because of the close proximity of the ventricular sensed event and the Ventricular Sense Response pacing pulse, the Biventricular (BV) annotation is not printed on the real-time ECG strip. The VS and BV are shown on Ventricular Sensing Episodes stored in the device.
- Ventricular Sense Response pacing pulses are not included in interval calculations for tachyarrhythmia detection.
- A ventricular sense that results in a Ventricular Sense Response pace is included in the count of consecutive sensed events to detect a ventricular sensing episode. The Ventricular Sense Response pace is not included in the count of consecutive paced events to detect the termination of a ventricular sensing episode.
- Ventricular sensing for the Ventricular Sense Response feature occurs via the RV lead only.
- Ventricular Sense Response operation is suspended during tachyarrhythmia therapies, system tests, EP study inductions, manual therapies, and emergency fixed burst, cardioversion, and defibrillation therapies.
- When both Ventricular Sense Response and Ventricular Safety Pacing are programmed to On, Ventricular Safety Pacing operation takes precedence during the Ventricular Safety Pacing interval.
Ventricular Sense Response Diagnostic
Ventricular Sensing Episodes can be reviewed by selecting Data > Clinical Diagnostics > Ventricular Sensing Episodes. Episodes are nominally collected if there is consecutive ventricular sensing greater than 30 seconds. Episodes terminate if three consecutive ventricular paces occur. These collection settings can be changed under Params > Data Collection Setup…. > V Sensing Episodes….
If the longest Ventricular Sensing Episode since the last session is greater than 60 seconds, an observation will also appear on the Quick Look II™ screen, and the VSR episode log can be accessed directly by highlighting the observation and clicking the Quick Link.
A patient with a Medtronic CRT-D device comes to the clinic. Upon device interrogation, it is discovered that the patient has been in atrial fibrillation for several days. Loss of biventricular pacing occurs because of rapid ventricular conduction during AT/AF. By viewing the VSR episodes, the clinician can see that when the ventricular rate falls below the maximum VSR rate, a VSR pace occurs. Conducted AF Response can also help maintain CRT when patients are in AT/AF. In this case, rhythm and rate control management should be addressed to increase the likelihood of the patient receiving CRT.
Sources: Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual.