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amplitude. If the operating amplitude is below the target, the device adjusts it to the target
immediately. The lower limit is set by the programmed RV Minimum Adapted Amplitude. If
the operating pulse width has a value different from 0.4 ms, the device adjusts it to that
value.
Upper limit for adjustments – The device adjusts the RV Amplitude to 5.0 V and the RV
Pulse Width to 1.0 ms if the amplitude threshold is greater than 2.5 V or the target amplitude
is greater than 5.0 V.
7.5.4.4 Stopping an RV pacing threshold search in progress
The device stops a pacing threshold search immediately if there are sudden changes in the
patient’s heart rate or if other device features take precedence over the search.
When a pacing threshold search cannot be completed, the device automatically schedules
another search within 30 min. If 5 more search attempts are stopped during a day, the pacing
threshold test is suspended until the following day. Whenever this happens, a device check
occurs again, and the process is repeated. The reasons for stopping a pacing threshold
search are noted in the Capture Threshold trends diagnostic (see Section 7.5.7).
7.5.5 Programming considerations for Capture Management
Warning: Capture Management does not program right ventricular or atrial outputs above
5.0 V or 1.0 ms. If the patient needs a pacing output higher than 5.0 V or 1.0 ms, you must
program Amplitude and Pulse Width manually.
Caution: Epicardial leads have not been determined appropriate for use with RVCM
operation. Program this feature to Off if implanting an epicardial lead.
Conditions that may influence threshold measurements – In a small percentage of
patients, the following conditions may influence thresholds measured by RVCM:
●
With poor lead fixation, modulations in pacing timing and rate could influence
thresholds.
●
In rare instances, combinations of morphology and rhythm may result in a low threshold
measurement. This may occur if the pacing threshold search is unable to differentiate
between myocardial contractions caused by the pacing pulse and those caused by
physiologic means.
High threshold measurements with RVCM – In rare instances, the device may not detect
the waveform created by the contracting myocardium immediately following a pacing pulse.
In such instances, a high threshold measurement may result.
Medtronic
PROTECTA™ XT DR D314DRG
Clinician Manual
247
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