Patient Selection and Preprocedural Considerations

Vascular and left atrial access

To reduce vascular complications, central venous access should be obtained with real-time ultrasound guidance; this reduces the number of attempts, time to access, and risk of arterial puncture. Moreover, an arterial line for hemodynamic monitoring should not be placed routinely, given the higher risk of hematomas in anticoagulated patients. Noninvasive intermittent blood pressure monitoring every 2 to 5 minutes is generally sufficient. For LA access, two separate transseptal punctures are performed (one for the ablation catheter, the other for the circular mapping catheter [CMC]), preferably under intracardiac echocardiography (ICE) guidance. The goal is to cross into the LA along the posterior interatrial septum, such that the left-sided PVs are in clear view ( Fig. 14.1 ; Video 14.1 ). Although a second transseptal sheath can be introduced via wire exchange, a separate transseptal puncture minimizes sheath-to-sheath interaction. LA access can be obtained using a variety of transseptal sheaths. In our center we prefer sheaths with a moderate primary curve and no secondary curve (such as the SL-0 for the ablation catheter and a LAMP-90 for the circular mapping catheter), which allow easier catheter maneuverability in the posterior aspect of the LA.

Intracardiac echocardiographic image of the left pulmonary veins. LSPV , Left superior pulmonary vein; LIPV , left inferior pulmonary vein.

Techniques and Results of Pulmonary Vein Isolation

Triggers from the PVs represent the dominant mechanism of initiation of AF. The initial description of PV trigger ablation consisted of focal ablation within the PVs. This approach had minimal long-term benefit and was associated with a significant risk of PV stenosis. Subsequent evolution of the procedure involved segmental ablation at the anatomic ostium of the PVs, as defined by angiography or ICE, to isolate muscle sleeve connections between the PV and LA electrically, an approach commonly referred to as segmental ostial PVI. In addition to ostial PVI, initial attempts targeted only the PVs with evidence of arrhythmogenic activity. However, it was rapidly realized that empirical isolation of all PVs was necessary to increase the procedural success, as the majority of patients presented multiple arrhythmogenic PVs. In addition, symptomatic PV stenosis remained an important risk with ostial PVI, and AF triggers localized in the more proximal antral region were not addressed with such strategy. The technique further evolved targeting the LA tissue more proximal to the PV ostium, in a region defined as the PV antrum.

To achieve antral PVI, multiple approaches have been described. The approach currently adopted in our institution is a wide PV antrum isolation (encompassing the LA posterior wall between the PVs) guided by a CMC and ICE ( Fig. 14.2 ). The importance of a wider antral isolation is the empirical elimination of triggers arising from the LA posterior wall, which should be considered as an extension of the PVs from an embryologic, anatomic, and electrophysiologic standpoint. Compared with ostial PVI, wide antral PVI is associated with a significantly lower rate of arrhythmia recurrence, driven by a reduced rate of AF at follow-up without increasing the rate of periprocedural complications. This approach has been demonstrated to be superior to other ablation techniques in studies of direct comparison, and is one of the most reproducible and standardized techniques to achieve PVI. Circumferential PV ablation without confirmation of electrical isolation with a CMC has been demonstrated to be ineffective in achieving long-term arrhythmia control. Moreover, adopting a CMC-guided approach also offers the potential advantages of shortening the procedural time, limiting the delivery of RF energy to discrete areas showing the earliest potentials (segmental approach). By contrast, in a circumferential PV ablation approach, contiguous lesions are created without necessarily achieving complete conduction block, and postincisional reentrant atrial tachycardias are not uncommon.

Antral pulmonary vein isolation (PVI) with posterior wall isolation; left , intracardiac echocardiographic image of the circular mapping catheter and ablation catheter at the level of the left superior pulmonary vein antrum; right , posterior view of the left atrium showing voltage before and after antral PVI.

Although not necessary, the use of a 3-dimensional electroanatomic mapping system, such as EnSite NavX Velocity/Precision (St. Jude Medical, St. Paul, Minn) and CARTO 3 (Biosense Webster, Diamond Bar, CA) can facilitate PVI significantly, allowing efficient registration of ablation sites and documentation of the extent of antral ablation ( Fig. 14.3 ). They allow real-time display of any cardiac catheter during ablation; most importantly, their ability to display the CMC allows for very rapid creation of a LA volume map and facilitates the direction of the ablation catheter toward the desired poles. While maneuvering the CMC, care should be taken not to displace it anteriorly, as this can result in its entrapment in the mitral valve apparatus, a rare complication that might result in valve damage requiring open heart surgery. The use of ICE during mapping facilitates locating the four PVs ( Video 14.2 ). The left-sided PVs can be seen with clockwise rotation of the ICE catheter a few degrees past the left atrial appendage (LAA) and the mitral valve annulus, whereas to image the right PVs, the ICE catheter is advanced slightly and further rotated clockwise. Moreover, ICE has been shown to reduce PV stenosis, compared with PV angiography. The LAA can be recognized by a high amplitude signal on the superior-anterior aspect of the LA.

Ablation lesions delivered to obtain antral pulmonary vein isolation. LIPV , Left inferior pulmonary vein; LSPV , Left superior pulmonary vein; RIPV , right inferior pulmonary vein; RSPV , right superior pulmonary vein.

The CMC is used as a roving catheter for mapping and directing the ablation catheter throughout the procedure ( Fig. 14.4 ). It should be small enough to move within the chamber easily, but of a large enough diameter that it does not readily fall deep inside the PVs. In most adults, a 20-mm, 10-pole CMC provides a balance between maneuverability and size. RF energy delivery with open-irrigation catheters is the standard of care in performing PVI. Open-irrigation catheters allow the use of greater power without a significant increase in temperature and clot formation, enabling more efficient and predictable energy delivery, resulting in larger ablation lesion sets. The main disadvantage of using open irrigation catheters is a higher risk of steam pops. There is a high discrepancy between the recorded tip temperature and the actual tissue temperature, thus steam pops might occur even with normal tip temperature. These can be minimized with appropriate titration of energy delivery, as guided by monitoring tip temperature, impedance drop, and if available, contact force. Our catheter of choice is a unidirectional open-irrigated 3.5-mm tip with an F curve. A smaller curve may be considered in the minority of patients with a very small LA, whereas a J curve is necessary for patients with a larger LA.

Circular mapping catheter (CMC)-guided antral pulmonary vein isolation; the roving CMC is sequentially placed along the pulmonary vein antra and posterior wall.

Using an irrigation-tip catheter, a power of 40 W is typically used. Occasionally, on the anterior aspect of the PVs (for example, a thick ridge), a higher power is needed to achieve potential abatement, but we generally do not exceed 45 W. With contact force sensing ablation catheters, this can be obtained by optimizing contact during radiofrequency (RF) energy delivery (at 40 W, our target contact force lies between 7 and 15 g). RF energy is delivered for approximately 20 seconds per lesion site or until the electrical signals have diminished. In areas near the esophagus, energy delivery should be limited to up to 10 seconds per lesion site, and keep moving the catheter to different areas during ablation to prevent esophageal heating. It is very important to monitor the esophageal temperature closely, frequently readjusting the esophageal probe so that it is close to the ablation area. A rapid rise in temperature is often noted, and when this happens, the ablation catheter should be moved away or RF delivery stopped, independently of the absolute value of esophageal temperature recorded. Despite movement of the catheter, a delayed rise in esophageal temperatures is often observed. As a general rule, esophageal temperatures greater than 38°C to 39°C should be avoided to minimize the risk of deep tissue injury. It is also important to note that the esophagus is wider than the temperature probe ( Fig.14.5 ); therefore sometimes no or minimal temperature change is recorded, despite ablating over the esophagus, as assessed by ICE ( Fig. 14.6 ). If ICE is not available, it is important to move quickly whenever ablating in the posterior wall regardless of the location of the esophageal probe.

Relationship between the esophageal probe and esophagus.

Intracardiac echocardiographic image of the esophagus behind the left atrial posterior wall.

We usually begin with ablation of the electrical potentials surrounding each PV. The end point of PVI is complete PV electrical isolation, as confirmed by entrance and exit block ( Table 14.1 ). Entrance block is confirmed by the absence of electrical signals where these signals had been previously observed. Occasionally, dissociated PV potentials can be recorded ( Fig. 14.7 ) to confirm exit block. In addition, pacing from within the PV can be performed to confirm exit block, although this is not necessary. Once PVI is achieved, we focus on the remaining antral areas. The CMC is particularly useful for identifying additional electrical potentials along the posterior wall and roof of the LA (see Fig. 14.4 ). The procedural end point is to eliminate all electrical activity in the antrum and roof of the LA (see Figs. 14.2 & 14.8 ). After PV antral isolation, with patients in sinus rhythm, 20 to 30 mcg per kg per minute of isoproterenol are infused to assess for PV reconnection and elicit non-PV triggers. If consistent (repetitive premature atrial contractions [PACs], PACs triggering atrial flutter/AF, and focal atrial tachycardia), their sites of origin are further targeted with ablation. We do not routinely use adenosine to test for acute PVI.

Dissociated firing in the left superior pulmonary vein.

Electrical silence in the left atrial posterior wall.

As mentioned, the majority of the studies investigating the role of PVI for the long-term maintenance of sinus rhythm have predominantly enrolled patients with paroxysmal AF; thus far the role of PV triggers in patients with nonparoxysmal AF has not been investigated in a systematic fashion. In addition, few data support the benefit of PVI in paroxysmal patients, also at the very long-term follow-up. However, the authors’ experience suggests that some of the patients will develop non-PV triggers over times that are responsible for arrhythmia recurrence at long term. The clinical experience with PVI in patients with nonparoxysmal AF has consistently shown worse results compared with paroxysmal patients, and PVI alone is largely insufficient to achieve satisfactory long-term arrhythmia-free survival in this cohort. Thus far the approach of most institutions is to provide extensive ablation targeting the LA substrate and areas demonstrating non-PV triggers, either spontaneously or after induction with drug challenges (e.g., isoproterenol) or pacing. However, the amount of additional ablation necessary in these patients to increase the procedural success is still a matter of controversy and goes beyond the scope of this chapter.

Complications of Pulmonary Vein Isolation

Because patients are anticoagulated, the most common complications are vascular (hematomas, pseudoaneurysm, and arteriovenous fistulas). These can be easily prevented using real-time ultrasound when obtaining central venous access.

Hemodynamic and temperature monitoring during the ablation procedure allows early detection and avoidance of the most serious complications of PVI: cardiac tamponade and atrial-esophageal fistula. A blood pressure drop, both sudden and gradual, should be evaluated carefully. A vagal response to ablation near the ganglionic plexi may result in transient sudden hypotension, usually associated with bradycardia (sinus arrest or atrioventricular block). If there is no immediate recovery, cardiac tamponade should be assumed until proven otherwise. Suspicion should be higher after a difficult transseptal puncture, a steam pop, or inadvertent application of excess pressure in the LAA or the roof of the LA. To determine early diagnosis of cardiac tamponade, it is important not to delay pericardiocentesis. A quick assessment to check for the presence of pericardial effusion can be easily and accurately performed with ICE ( Video 14.3 ). If this is not available, fluoroscopy usually demonstrates a reduction in the excursion of the cardiac silhouette, better appreciated in the LAO view. Of note, especially after extensive ablation, it is not uncommon to detect mild pericardial effusion without hemodynamic compromise following the procedure. Most of these asymptomatic effusions can be managed conservatively.

PVI involves extensive burning near the esophagus, and atrial-esophageal fistulas can present in the weeks following ablation. Although exceedingly rare, they are frequently fatal; therefore prevention and early diagnosis/treatment (surgical repair) are important to reduce mortality. During ablation, temperature monitoring as well as limitation of the duration of energy delivery when ablating in the posterior aspect of the LA (down to the CS) is vital to avoid excessive heating of the esophagus. A short course of prophylactic proton pump inhibitors and sucralfate can be prescribed. During follow-up, patient and physician awareness is the key. Patients should be instructed to immediately contact the electrophysiology service if fever, chest pain, neurologic symptoms, dysphagia, hematemesis, or melena occur.

Thermal injury can also result in phrenic nerve (PN) injury. This can be right sided when ablating in the right superior PV or performing isolation of the superior vena cava (SVC), or left sided when ablating inside the LAA. To prevent PN injury, it is important to avoid ablation inside the PVs or LAA, and to perform PN mapping when isolating the SVC. Patients with PN paralysis are usually asymptomatic, but they can present with dyspnea on exertion. There is no treatment, but the condition is usually transient, so observation is all that is needed. Dyspnea, with or without cough or hemoptysis, is also a presenting symptom of severe PV stenosis, which is a rare occurrence after true PVI, because RF energy is not delivered ostial or inside the PVs. PV stenosis is diagnosed with CT imaging, and if severe or symptomatic might require intervention (venoplasty and stenting).

To reduce periprocedural thromboembolic events, the procedure should be performed under uninterrupted oral anticoagulation and heparin administered transseptal access with goal ACT 350 seconds or more. To prevent air embolism, transseptal sheaths should be continuously flushed with 2 to 4 mL per minute of heparinized-saline using pressure bags set at 300 to 400 mm Hg.