Achieving Quadri-Directional Block for Pulmonary Vein Antral Isolation

Introduction

Pulmonary vein antral isolation (PVAI) is currently the standard of care for both paroxysmal and persistent atrial fibrillation (AF) ablation.¹ The success rate for PVAI is still modest, about 70%-75% with the first procedure and improving to 80%-85% with multiple procedures in patients with paroxysmal AF.^2,4

Reconnection to the pulmonary vein is the most common cause of recurrence of AF. The ability to achieve a durable PVAI with transmural lesions can be difficult. Various modalities have been done to improve outcome, including injection of adenosine to look for latent conduction, pacing on the antral line, and further ablation for areas of capture. Contact mapping has improved our understanding of lesion formation, with care to apply enough power and time for contact.³ However, despite these efforts, we still have a moderate rate of recurrence. 

Achieving a bidirectional block (BDB) is currently the standard of care for typical atrial flutter ablation. Achieving bidirectional cavotricuspid isthmus conduction block has revolutionized our understanding and improved our outcomes for atrial flutter ablation. Currently, success rates for atrial flutter ablation are close to 95% when BDB is achieved.⁵

In 2005, Verma et al compared PV conduction in patients undergoing second PVAI for AF recurrence to patients cured of AF.² They found that patients who maintained sinus rhythm with no AF recurrence had substantial atrial to PV conduction delay compared to patients who fail PVAI. They also noted that patients who had a longer delay are more likely to maintain sinus rhythm with or without antiarrhythmics. 

Therefore, we hypothesized that if we are able to achieve this delay prospectively in the first procedure in both antral lines prior to complete isolation of the veins, this may lead to more favorable effects on outcome. Pulmonary vein antral lines are circular lines, and thus, it is possible to pace both sides of each line and look for conduction delay prior to closing the circle. We performed pacing from the distal coronary sinus while watching for delay in the left upper pulmonary vein (LUPV), with the aim of achieving a long delay comparable with those delays seen on flutter lines with BDB before complete isolation of the antral line. This is done by leaving a small gap in the superior aspect of the line (by the roof) and only closing this gap after achieving enough delay, preferably >135 ms, in the line (Figures 1 and 2). Likewise, for the right-sided antral line, we paced from the proximal coronary sinus while watching for signal delay in the spiral catheter inserted in the right upper pulmonary vein (RUPV). 

Case Description

A 60-year-old female with a history of paroxysmal atrial fibrillation (PAF) was put on sotalol for rhythm control; the patient also had sick sinus syndrome, for which a permanent pacemaker was implanted. She continued to be symptomatic with significant burden of AF (up to 14 hours per day) despite being on sotalol, and agreed to undergo AF ablation. Echocardiogram and cardiac CT were normal.

After informed consent with detailed information was given to the patient about the procedure, she was brought into the EP lab. Standard venous access using three 8 French (Fr) sheaths were inserted into the right common femoral vein using ultrasound guidance. Nine Fr sheaths were inserted into the left common femoral vein and 7 Fr sheaths were inserted into the right internal jugular vein.

Transesophageal echocardiogram (TEE) was done prior to the procedure as well as a 64-slice CT scan. Anatomy obtained from both modalities were integrated with electroanatomical mapping using the EnSite Velocity System (St. Jude Medical). (Figure 1)

Anticoagulation was done by keeping the patient on warfarin. Target INR was between 2 and 3 before the procedure as well as after the procedure. Periodic INRs were done before and after the procedure.

General anesthesia with hemodynamic monitoring was done by the anesthesia team. The arterial line was inserted through the radial artery to confirm hemodynamic stability.

An 8 Fr ACUSON AcuNav ultrasound catheter (Siemens Healthcare USA) was inserted into the left common femoral vein and placed into the right atrium. It was used to monitor transseptal puncture as well as confirm catheter stability and position; it was also used to evaluate catheter contact during ablation and provide safety guards for early detection of complications.

Duo-decapolar catheters were inserted through the right internal jugular vein into the coronary sinus with the proximal poles in the high right atrium. 

Two transseptal punctures were performed using the ACross™ Transseptal Access System (St. Jude Medical). This was done under intracardiac echo as well as fluoroscopy guidance. Monitoring was also continued with hemodynamic guidance. The SafeSept™ Transseptal Guidewire (Pressure Products) was used to avoid through-and-through puncture.

A spiral catheter was used to obtain electroanatomical mapping of the left atrium, which was later merged with CT imaging.

An esophageal temperature probe was advanced into the esophagus and intermittently repositioned in close proximity to the ablation catheter. It’s important to evaluate change in temperature during ablation; any significant rise of more than 0.5° was enough to consider lowering the wattage output or moving to another area. Power was titrated at 20 watts with an irrigation catheter in areas close to the esophagus.

Anticoagulation was done with heparin bolus or drip to maintain an activated clotting time (ACT) of greater than 350 or less than 400. Frequent ACT was checked every 15 minutes, and heparin was readjusted until the ACT remained stable.
Left atrial pressure, as well as patient input and output, were continuously monitored throughout the procedure. Ablation was performed using saline irrigation catheters with power of 35 watts except for areas close to the esophagus or inside the veins, when it was titrated to 20 watts. Care was taken to avoid ablation inside veins and rather to isolate veins just outside the os.

Steps for achieving bidirectional block for pulmonary veins antral lines (Figures 1-7):

1. An electroanatomical map of the left atrium was obtained.
2. Two wide antral lines were drawn with small gaps left at the superior aspect of the line on each side, leaving the carina open.
3. Ablation was done on top of the drawn lines while pacing from the distal CS for the left antral line and proximal CS for right antral line.
4. Evaluation of the delay to PV potential was intermittently measured until we achieved a delay of at least 135 ms or more.
5. If the ablation was completed without achieving antral delay, we tried to look for gaps in the line and did further ablation in area of gaps or persistent signal.
6. If delay was still not achieved, we paced at the line for areas of capture and ablated at areas of capture or viable myocardium.
7. If delay was still not achieved, we then looked for signals inside the line and target areas with the narrowest delay as a sign of a gap.
8. Once we achieved the delay, we closed the gap at the superior aspect of each line.
9. We then paced from the spiral catheter inside each of the four veins to ensure exit block. 
10. We ensured entrance block by evaluation of absence of the signal inside the veins, or this was done with pacing in the left atrial appendage or right atrium to make sure that the remaining signals left were only far field.
11. We put lesions at the carina on each side for completion purposes. 

Isoproterenol was then started with decremented atrial pacing down to a cycle length of 200 for 6 seconds with no evidence of tachycardia or ectopy. Limited EP study was done with decremental pacing to evaluate AV conduction properties and to rule out other arrhythmias. Protamine 40 mg was given, and catheters were removed at the end of the procedure. Hemostasis was achieved by manual pressure at venous access sites. The patient then was transferred to the floor where they stayed overnight and was sent home the next day. 

Follow-up and Outcome

The patient was followed up with a device check every 3 months and with transmissions via the Merlin.net™ Patient Care Network (St. Jude Medical) every 3 months. Sotalol was discontinued 5 days prior to the procedure and never restarted. 

There was no recurrence of atrial fibrillation seen after the 3-month post-procedure waiting period, as evidenced by absence of mode switch (Figure 8). The patient was followed up with for 18 months, and experienced no complications.

Discussion

Through detailed mapping and pacing in a systematic way, we were able to achieve a significant conduction delay of PV antral lines comparable with delays seen on standard lines done for typical and atypical atrial flutter. We also demonstrated complete resolution of PAF, confirming the efficacy of this technique.

Our long-term outcome for PAF and persistent AF compare favorably with other centers of excellence for AF ablation, partly attributed to our improved understanding and development of this technique.

Other studies done to evaluate patients with conduction delay also noted that patients with significant conduction delay, as seen on the repeat procedures, were more likely to do better than those with no conduction delay.² This confirms our concept of the importance of prospectively achieving such delays.

Limitation

This is a single case report; therefore, it should be treated as such. We have not used contact force catheters, which may be helpful to ensure transmurality of the lesions, although care was taken to achieve a decrease in impedance with each lesion formation to ensure proper contact. Contact was also confirmed with intracardiac echo during the procedure.

Conclusion

We present what we believe to be the first case of achieving quadri-directional block for PVAI. This was done by achieving the standard exit and entrance blocks of the PVs added to our novel concept of achieving a BDB in the wide antral line prior to complete isolation. Further studies are needed to show the feasibility, efficacy, and safety of this new technique.

Disclosures: The authors have no conflicts of interest to report regarding the content herein. 

Editor’s Note: This article underwent peer review by one or more members of EP Lab Digest’s editorial board.

References

1. Dipen S. Electrophysiological evaluation of pulmonary vein isolation. Europace. 2009;11:1423-1433.
2. Verma A, Kilicaslan F, Pisano E, et al. Response of atrial fibrillation to pulmonary vein antrum isolation is directly related to resumption and delay of pulmonary vein conduction. Circulation. 2005;112:627-635.
3. Kumar S, Michaud GF. Unipolar electrogram morphology to assess lesion formation during catheter ablation of atrial fibrillation: successful translation into clinical practice. Circ Arrhythm Electrophysiol. 2013;6:1050-1052.
4. Essebag V, Wylie JV Jr, Reynolds MR, et al. Josephson bi-directional electrical pulmonary vein isolation as an endpoint for ablation of paroxysmal atrial fibrillation. J Interv Card Electrophysiol. 2006;17(2):111-117. 
5. Oral H, Sticherling C, Tada H, et al. Role of transisthmus conduction intervals in predicting bidirectional block after ablation of typical atrial flutter. J Cardiovasc Electrophysiol. 2001;12(2):169-174.