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.