Patient preparation and procedure set-up
The patient can undergo CNA procedure under conscious sedation or general anesthesia. We have recently demonstrated that the autonomic nervous tone can be differentially affected by the level of conscious sedation (18). VR during GP ablation was defined on 3 levels: 1) R-R interval increase of >50% (level 1); 2) R-R interval increase of 20-50% (level 2); and 3) R-R interval increase of <20% (level 3). While ablation of the left superior GP caused a level 1 VR in 89.6% of cases in conscious sedation group, level 1 VR was seen in only 22.2% of cases in deep sedation group (p<0.0001). Similarly, percentage of patients with level 1 VR during ablation of the left inferior GP was significantly lower in deep sedation group. Once the cut-off for VR was decreased to level 2, the ratio of (+) VR during ablation of the left superior and inferior GPs was similar between groups. Thus, we concluded that R-R interval increase of >20% instead of >50% should be used for definition of VR in cases performed under deep sedation. In our current approach, in conscious sedation, patients receive a combination of fentanyl 50 μg and midazolam 0.02 to 0.06 mg/kg bolus, followed by a 3 to 5 mg/h continuous infusion. In deep sedation, patients receive a bolus injection of midazolam (0.02 to 0.06 mg/kg) over 30 s, followed a minute later by intravenous propofol infusion (1.0 to 2.5 mg/kg; infusion rate, 400-600 ml/h).
Furthermore, some anesthetic agents like ketamine, and mechanical ventilation, in particular positive end-expiratory pressure, may induce a shift in the sympathovagal balance toward sympathetic predominance, which may cause a blunting on VR characteristics during GP ablation (19). Awareness of anesthesia related differences may be important if GP ablation is performed by using VR characteristics during ablation.
A 6 French and one 8 French sheaths are placed in the right common femoral vein and a decapolar steerable catheter is placed in the coronary sinus (CS). Arterial line, urinary catheter or esophageal temperature probe are not routinely used. We start the procedure by performing a bipolar map of the right atrium with a multipolar (The Inquiry™ AFocusII™) or a high-density mapping catheter (Advisor™ HD Grid and PentaRay®). We delineate the inferior and superior vena cava, and the coronary sinus, and we tag the His potential and phrenic nerve capture sites with high-output pacing of 20mA.
Next, a single transseptal puncture is performed using an 8.5 Fr transseptal sheath (SL1, St. Jude Medical, Minneapolis, MN, USA) and a transseptal Brockenbrough needle (BRK, St. Jude Medical) under fluoroscopic guidance -. A 0.032-inch 200 cm guidewire is advanced to the left superior pulmonary vein and transseptal sheath is replaced with a deflectable sheath [VIZIGO™ (Biosense Webster, Johnson & Johnson Medical S.p.a., Irvine, CA, USA) or Agilis™ NxT (Abbott, Chicago, IL, USA)]. Then, a multipolar or a high-density mapping catheter is advanced through the deflectable sheath into the left atrium to perform a fast-anatomical mapping of the left atrium and the pulmonary veins. During fast-mapping, we particularly focus on acquiring contact points between the right superior pulmonary vein and the superior vena cava, and the septal part of lower left atrium and the coronary sinus ostium.