124 Stratos LV/LV-T Technical Manual

To determine the threshold, the ECG must be observed continuously. Based on the measured threshold, the pulse amplitude for the permanent program should be adjusted. Please consult the pertinent medical literature for specific recommendations regarding necessary safety margins.

NOTE:

With successful biventricular pacing of patients with congestive heart failure, the QRS complex should be visibly shortened.

5.2P/R Measurement - Testing the

Sensing Function

Stratos CRT-Ps provide a P-/R-wave test for measuring the amplitude of intrinsic events during follow-up examination. The test determines the minimum, mean and maximum amplitude values over a programmable period of time. In addition, these values may be printed out.

To permit evaluation of the sensing function, the pacing rate must be lower than the patient's intrinsic rate. In demand pacing, the proper sensing function can be recognized if the interval between intrinsic events and the following pacing pulse equals the basic interval (if no Hysteresis is programmed).

For evaluation of the sensing function, the CRT-P features an intracardiac electrogram (IEGM) with marker signals to indicate sensed and paced events. In addition, triggered pacing modes can be selected which, synchronously to the detection of an intrinsic event, emit a pacing pulse and mark the sensed event and its timing on the ECG.

Especially with unipolar sensing functions, the selected sensitivity level should be checked for possible interference from skeletal myopotentials. If oversensing is observed, the programming of a lower sensitivity (higher value), or bipolar sensing function, if the implanted lead is bipolar, should be evaluated.