24
and shocking the patient with high-voltage pulses delivered from the pulse
generator, through the defibrillation electrodes of the lead, to the heart.
Baseline measurements should fall within the recommended values listed in
the Recommended threshold and sensing measurements table (Table 3
Recommended threshold and sensing measurements on page 21).
CAUTION:
Following an unsuccessful high-energy shock, miscounting of
cardiac rate, delayed detection, or nondetection due to low amplitude VF
signals, it may be necessary to reposition the lead.
WARNING:
Always have external defibrillation equipment available during
implant and electrophysiologic testing. If not terminated in a timely fashion, an
induced ventricular tachyarrhythmia can result in the patient's death.
Reliable conversion of VF should be demonstrated at an energy level less than
the maximum energy setting of the pulse generator. Consider the following:
•
It is recommended that multiple induction conversion tests of VF be
performed to determine conversion reliability and the patient’s defibrillation
threshold (DFT).
•
It is a matter of clinical judgment as to what constitutes a demonstration of
reliable conversion. Since the result of any single test is subject to
statistical variation, a one-time conversion of a rhythm disturbance at a
particular energy level does not necessarily predict future conversion
energy levels.
•
Refer to the applicable pulse generator physician's manual for conversion
testing guidelines.
•
Weigh the probability of reliable conversion in the ambulatory state against
the availability of the pulse generator energy settings and the patient’s
ability to tolerate multiple arrhythmia inductions.
•
If a patient’s arrhythmia(s) cannot be reliably converted with the lead,
supplementary implantation of an alternate lead system will require
additional conversion testing.
WARNING:
Do not use any component of the lead system to assist in
delivery of external-source rescue shocks or extensive tissue damage
could occur.
•
The decision to implant any pulse generator lead system in any
configuration should be based on demonstration of adequate safety
margins at the programmed shock energy as determined by DFT and
cardioversion energy requirement (CER) testing. Refer to the applicable
pulse generator physician’s manual for DFT and CER testing
requirements.
•
Clinical study indicates that a programmed safety margin of 9–10 J above
the patient’s DFT was used in the majority of patients. If a 9–10 J safety
margin cannot be obtained, consider placing an alternative defibrillation
lead system.
NOTE:
If, after prolonged and repeated inductions of VF, a thoracotomy
is to be performed, consider performing it at a later date.
