Ventricular Rate Stabilization (VRS) Feature
When a patient experiences a PVC, it is often followed by a long pause in the cardiac cycle. This pause is sometimes associated with the onset of pause-dependent ventricular tachyarrhythmias. Ventricular Rate Stabilization (VRS) is a programmable feature designed to eliminate the long pause that commonly follows a premature ventricular contraction (PVC). VRS responds to a PVC by increasing the pacing rate, then gradually slowing it back to the programmed pacing rate or intrinsic rate.
This feature can be found in some Medtronic Pacemaker, ICD, 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.
VRS is nominally Off and is operational when the device is operating in the DDDR, DDD, DDIR, DDI, VVIR, or VVI mode.
Additional programming parameters include (nominal settings are shown in image below):
- Maximum Rate – Determines a minimum interval that limits the new calculated interval.
- Interval Increment – Adds to the previous V-V interval to calculate the new interval.
To program this feature in pacemakers, go to Params -> Arrhythmia Interventions.
To program this feature in ICDs, go to Params -> Pacing… -> Arrhythmia/Post Shock…
- In the DDIR or DDI mode, when Ventricular Rate Stabilization increases the pacing rate, Auto PVARP reduces the likelihood of competitive atrial pacing at high sensor-indicated rates.
- If a combination of Atrial Rate Stabilization, Atrial Preference Pacing, and Ventricular Rate Stabilization is enabled, the device uses the algorithm that produces the shortest escape interval.
- Rate Hysteresis and Ventricular Rate Stabilization cannot be enabled at the same time.
- If both Conducted AF Response and Ventricular Rate Stabilization are enabled in DDD or DDDR modes, CAFR operates during a Mode Switch, and VRS operates outside of Mode Switch. Conducted AF Response and Ventricular Rate Stabilization cannot both be enabled in DDI, DDIR, VVI and VVIR modes.
When VRS is enabled, it acts as a constant rate-smoothing algorithm by adjusting the ventricular intervals that may follow a PVC. Following each successive ventricular sense or ventricular pace event, the device calculates a new pacing interval by adding the programmed interval increment value to the previous pacing interval. The calculated interval lengthens, from beat to beat, until the device returns to the intrinsic rate or the programmed pacing rate, whichever occurs first. The pacing rate increase determined by VRS, however, does not exceed the maximum rate programmed for this feature.
An upper limit is placed on Ventricular Rate Stabilization operation because it is intended as a response to a premature ventricular beat. It does not respond to sustained fast heart rates.
On each ventricular event, the device calculates a new ventricular interval as:
New R-R interval = previous R-R interval + programmed Interval Increment value
(or a predetermined minimum interval* if it is larger than this sum)
If the calculated interval is shorter than the current pacing interval and no intrinsic ventricular event occurs, the device delivers a ventricular pace when the interval ends. The interval is then recalculated based on the last ventricular interval. The calculated interval lengthens, from beat to beat, by a value equal to the programmable Interval Increment.
If Ventricular Rate Stabilization is enabled while one of the following is in progress, no VRS pacing will occur for a minimum of 12 ventricular beats:
- ATP therapies
- Manual therapies
- Manual inductions
- System tests
Sources: Medtronic Adapta™/Versa™/Sensia™ Reference Guide; Medtronic Consulta™ CRT-P Clinician Manual;Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual.