Rate-Adaptive Pacing

he Omnisense™ sensor, an accelerometer, uses a mass fixed to a diving board-like structure, which is fixed to the pacemaker circuit. Movements of the body during activity trigger a displacement of the mass, which allows measuring of linear acceleration.

Sensor Threshold

Determines the amount of activity required to initiate or trigger sensor activity.

• a level of activity below the threshold will be ignored and will not have any effect on the pacing rate
• a lower Threshold setting allows the sensor to respond to lower levels of activity, while a higher setting makes the sensor respond only to higher activity levels
• programmable from 1 to 7 (the lower the value, the more sensitive the threshold) or automatic
• auto: the device automatically adjusts the threshold parameter above or below the Measured Average Sensor (MAS) value, a calculation of the patient’s activity over the previous 18 hours; the MAS is continually updated; the MAS value appears under the Threshold button; for instance, a setting of Auto (+1.0) automatically sets the Threshold parameter to 3.0 if the MAS value is 2.0
• in patients with low activity: use a more sensitive threshold (Auto -0.5)

 Sensor slope

Determines the level of response of the device to the signals of the sensor. The slope determines how much the pacing rate will be increased compared to the base rate depending on the level of activity sensed by the accelerometer.

• programmable from 1 to 16 (the higher the value, the more important the rate increase) or automatic
• lower settings (flatter responses) limit the response to activity to small increases in the pacing rates
• higher settings (steeper responses) allow the rate to increase to higher pacing rates
• the Auto settings allow the device to automatically adjust the Slope parameter above or below the Measured Auto Slope, which is a calculation of the patient’s activity over the previous seven days

Maximum Sensor Rate

Determines the fastest pacing interval allowed by the rate-responsive pacing. It is also the fastest Sensor-indicated rate that can be recorded when the Sensor parameter is set to Passive.

Reaction Time

Determines the time needed to go from the base rate to the sensor-indicated rate.

• controls how quickly the sensor-indicated rate occurs
• must be fast if the patient is not very active
• must be slow for very active patients (to avoid inopportune accelerations for sudden moves that are not a sustained activity)

Recovery Time

Determines the time needed to go from the sensor-indicated rate to the base rate.

• controls how quickly decreases in the Sensor-indicated rate occur

Programmable settings

• sensor: On/Passive/Off
• threshold: Auto (-0.5), Auto (+0), Auto (+0.5), Auto (+1), Auto (+1.5), Auto (+2), 1 to 7
• slope: Auto (-1), Auto (+0), Auto (+1), Auto (+2), Auto (+3), 1 to 16
• max Sensor Rate: 80, …, 130,…, 180 bpm
• reaction Time: Slow/Medium/Fast/Very Fast
• recovery Time: Slow/Medium/Fast/Very Fast