Two possible mechanisms might include (1) cessation of aspirin prior to the procedure, and (2) pacing of the heart from the new ICD
. The latter explanation is more likely. Depending on how your ICD
is programmed, your heart may now be in a paced rhythm, which can be less efficient than your body's natural rhythm.
Another explanation (perhaps the most likely) is that the two events are unrelated.
Talk to your doctor, and good luck.