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Chapter 5 Programmable Parameters
Evia HF / HF-T Technical Manual
PAGE 53
• The algorithm is designed to respond appropriately to fusion beats. In order to discriminate non-
capture from fusion, a capture confirmation algorithm varies the AV delay after detection of non-
capture in the dual chamber pacing modes. First, fusion is diminished by extending the AV delay. If
a second non-capture is detected, the AV delay is returned to the programmed AV delay. If a third
consecutive non-capture is detected, loss of capture is confirmed and a Signal Analysis and
Automatic Threshold Search are initiated. If the first event was truly fusion, the extended AV delay
could allow intrinsic conduction. The AV delay will not return to the normal programmed value until
ventricular pacing is required. In case the capture confirmation continues to detect non-captures
without detecting 3 consecutive non-captures, the algorithm shortens the AV delay (50 ms after an
atrial paced event and 15 ms after an atrial sensed event for up to 2 paced cycles) to confirm the
occurrence of non-capture. When VCC and CLS are both enabled, the AV delay is extended after
detection of non-capture and then capture confirmation is temporarily disabled while CLS performs
an AV Hysteresis Scan.
5.13.3.1 Algorithm Suspension, Abort and Disabling
The VCC feature is inactive until the first SA and CV after programming is completed successfully.
The SA/CV sequence is unsuccessful when the SA or CV fail or are aborted. In addition, an SA/CV
sequence can be postponed and CV can be temporarily suspended.
The SA/CV sequence will fail when the following events occur:
• Non-capture during SA: non-capture occurs twice in the second through fifth cycles of the SA (at
the maximum voltage amplitude setting).
• High polarization artifact during SA: the polarization artifact measured during the SA is too high.
• No non-capture during CV: the threshold search decreases the output to 0.1 V without detecting
non-capture.
An ongoing SA/CV sequence will abort when the following events occur:
• Mode Switch: Mode switch has a higher priority than the SA/CV. If Mode switch aborts an SA/CV,
the device will be set to high output. After reversion back to the programmed mode, a new SA/CV
will be initiated.
• Programmer Wand application: An ongoing SA/CV aborts when a magnet (programmer wand) is
applied and the device is then set to high output. After removal of the magnet, a new SA/CV is
started.
• Search timer expiration (120 seconds): if the SA/CV takes longer than 120 seconds to be completed
(e.g. due to sensing), the SA/CV will be aborted and the device will be set to high output.
• Noise detection: if excessive noise is detected, the initial SA/CV will be aborted and the device will
be set to high output.
A SA/CV sequence will be postponed when the following events occur:
• Mode switch is ongoing: If Mode switch is ongoing when an SA/CV is scheduled, the SA/CV will be
postponed until reversion back to the programmed mode.
• The presence of a magnet is detected: A scheduled SA/CV is postponed when a magnet
(programmer wand) is detected. After removal of the magnet, the SA/CV is started.
• The ventricular rate is higher than 110 bpm: A scheduled SA/CV is postponed when the ventricular
rate is higher than 100 bpm. When the ventricular rate drops below 10 bpm, the SA/CV is started.
The continuous capture control (CV) will be suspended and the ventricular pacing amplitude is set to
high output when the following events occur: