User's Manual

80
Rate Adaptation
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The pacemaker evaluates the dynamics of the myocardial contraction
quickly after ventricular contraction. Impedance is measured via a
ventricular lead and is largely dependent on the specific conductivity of
a small volume of tissue surrounding the electrode tip.
Changes in impedance are characteristic of ventricular contraction and
are directly proportional to heart stress. The pacemaker calculates the
necessary pacing rate by measuring the current impedance and
comparing it with impedance data that was measured at rest. CLS is
able to immediately respond to exertion by using contractility as input
for rate adaptation. There is therefore no need to combine CLS with
accelerometer-based rate adaptation.
Closed Loop Stimulation is self-calibrating and automatically adjusts to
the patient's situation within just a few minutes. Typically, there is no
need to manually fine-tune the system. Automatic fine-tuning
continually occurs throughout the entire service time of the
pacemaker.
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It may be necessary to adjust the CLS in individual cases, as when a
patient is extremely active or inactive.
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Among other things, the baseline impedance curves used for comparison are regularly
updated by pacing cycles with extended or reduced AV delays.