Discussion
The major findings in the present study were (1) the lowest LAP in
sedated patients dropped to less than the atmospheric pressure in
approximately 73% of patients, (2) ASV increased the lowest LAP value
to positive in 81% of the patients who had a negative lowest LAP value
before the ASV support, (3) there were no significant differences
regarding the patient characteristics including the prevalence of OSA,
BMI, and a male gender between the patients with and without a negative
lowest LAP value after the ASV support.
A drop in the LAP of less than the atmosphere pressure during the PVI
increases the risk of massive air intrusion during the procedure. The
hemostasis valve of the sheath plays an important role in the prevention
of air intrusion into the vasculature through a long sheath. However,
the valve could become open to the atmosphere while inserting a catheter
into the sheath via the valve, especially when inserting catheters with
complicated tip shapes such as circular mapping catheters or multipolar
catheters2, 6. If the timing of the insertion of the
catheter is synchronized with a drop in the LAP to less than atmospheric
pressure, a massive air embolism is prone to occur. The continuous
maintenance of the LAP above the atmospheric pressure during the
procedure could absolutely decrease the risk of air intrusion. The
present study confirmed that the majority of the sedated patients
undergoing AF ablation had a negative LAP during the procedure, and to
the best of our knowledge, this is the first clinical study that has
demonstrated the efficacy of the ASV in the prevention of an LAP drop to
less than the atmospheric pressure. Although the present study evaluated
the LAP in patients undergoing a cryoballoon PVI, this result could be
applicable to all kinds of percutaneous catheter procedures which
require access into the LA.
In addition to providing a supply of positive expiratory pressure, ASV
has a unique algorithm that automatically supplies positive inspiratory
pressure according to an analysis of the patient‘s breathing effort. It
could provide a stable respiration pattern. Although bronchial
intubation could certainly more effectively reduce the risk of air
intrusion and contribute to a stable LAP, it is invasive and requires
general anesthesia, however, the ASV treatment is easy to start and
finish. Therefore, an evaluation of the impact of ASV on the LAP could
be worthwhile.