Atrial fibrillation ablation (left sided)/Pulmonary vein isolation (PVI)

Matthew Dudley, MD, Wilson Cui, MD PhD

AF Ablation/PVI Draft, 8/2014

PROCEDURE


Atrial fibrillation ablation (left sided)/Pulmonary vein isolation (PVI)

PATIENT DEMOGRPAHY
The prevalence of atrial fibrillation (AF) increases with age and is rare in adults younger than 55 who do not have structural heart disease. In older population, the incidence of new cases ranges from 2 or 3 per 1000 population per year in the age group of 55-64 years to 35 in patients older than 85. AF may be an independent risk factor for death after adjustment for other risk factors.

There is ongoing debate regarding ablation versus rate control for patients in AF refractory to electrical or chemical cardioversion. Primary indication for catheter ablation is the presence of symptomatic AF that is refractory or intolerant to at least one class 1 or class 3 antiarrhythmic drug, and ablation may be appropriate in selected, symptomatic patients with heart failure, a reduced ejection fraction, or both.

DISEASE BACKGROUND AND PROCEDURAL DESCRIPTION
In AF, the rapid atrial rate is initiated by a single focus of abnormal activity, most commonly near one of the pulmonary vein ostia in the LA. Once initiated, the fibrillation is maintained by multiple micro- reentrant circuits in the atria. New onset AF is usually self-limiting and sinus rhythm is restored spontaneously. However, over time the atria of patients with AF remodel—atria dilate, undergo fibrosis and inflammation, and the electrical property of the atrial tissue becomes altered—thus paroxysmal AF becomes persistent AF. Due to the competing micro-reentrant circuits, the ECG will not show distinct P wave or the saw tooth pattern but rather small amplitude oscillations. Ventricular response varies. Paroxysmal and persistent AFs are often amenable to ablation. The ectopic foci for AF in most patients are usually located in the four pulmonary vein ostia of the left atrium (LA).

Several methods for procedural rhythm control are possible:

  • Ablation of the Atrioventricular Node and Implantation of a Pacemaker
  • The Maze Procedure is performed by a cardiac surgeon that aim to electrically isolate the ectopic foci and prevent the propagation of the aberrant impulse to the AV node, either with 

  • Full thickness incisions of both atria (necessitating sternotomy and cardiopulmonary bypass) OR
  • Cryoablation of the LA surrounding the pulmonary veins (usually done thorocoscopically).
  • Focal ablation of ectopic foci/pulmonary vein ostia isolation (PVI, the procedure discussed here). Ablation of cardiac/vascular tissue is performed most commonly with radiofrequency (RF) energy to induce a transmural heat injury, which later scars to isolate the electrical propagation of impulses. Other methods include cryoablation via catheter or balloon and laser ablation via balloon. Catheters are typically introduced into the right atrium from the femoral vein up the iliac vein and vena cava. Each catheter has multiple electrodes along its tip capable of recording electrogram with the exception that the most distal electrode can also stimulate and pace. In order to access the LA where the PVI is performed, the catheter either crosses a pre-existing patent Foramen Ovale (PFO) or via a trans-septal puncture. Catheters are guided with fluoroscopy, intracardiac echocardiography, and with the assistance of various mapping systems that help locate the ectopic foci, identify the depolarization pattern, position the ablation catheter, and evaluate ablation results. The ablation of cardiac tissue is performed most commonly with radiofrequency (microwave) energy to induce a transmural heat injury (60 to 70 degree Celsius at the catheter tip), which scars to isolate the electrical propagation of impulses. The tip is actively cooled with saline irrigation to avoid over-heating and the undesirable formation of coagulum. Coagulum prevents effective tissue lesion, and the catheter needs to be withdrawn to remove the coagulum.

PRE-OPERATIVE ASSESSMENT

  • Standard ASA NPO guidelines should be followed for this elective procedure. 

  • A thorough assessment of the patient’s airway and respiratory status is essential since the airway will be far from the anesthesia provider with potential obstacles such as the fluoroscopic equipment and drapes. History of reactive airway disease, COPD, OSA, GERD, pleural effusion, or pulmonary edema from acute heart failure may affect the anesthetic management. 

  • In addition to the arrhythmia, the overall cardiovascular and functional status of the patient should be assessed. Other etiologies of AF may have significant cardiovascular and systemic manifestations. The patient may be frail from chronic de-conditioning, have reduced ventricular function due to tachycardia- induced cardiomyopathy, or have other structural heart diseases. LA enlargement is often associated with AF, which may present additional challenges during mapping/ablation. It is important to note the patient’s symptoms during atrial fibrillation, rapid rates, or other arrhythmias. 

  • Anti-platelet agents and anticoagulants should be noted. Anti-platelet agents are usually not stopped. Warfarin is usually not stopped as long as patient has been on chronic, stable, therapeutic dose. Other agents are stopped at the proceduralist’s discretion. Regardless, this may increase the risk of bleeding or hematoma during and after the procedure, by anesthesia and the proceduralist. 

  • Patient with chronic renal insufficiency or end-stage renal disease will need to have their electrolytes and fluid status assessed carefully. The team should be mindful of exposure to nephrotoxic contrast agents in patients with reduced GFR; however, EP stuides do not commonly expose the patient to contrast. 

  • Patients who suffer from chronic back or leg pain may not tolerate spending extended periods in a supine position without proper positioning, padding and analgesia. 

  • It is important to set proper expectation for the patient. He should be warned that he may wake up feeling the Foley catheter and significant pressure in his groin area (for hemostasis), and despite that, he needs to remain still.

PRE-OPERATIVE PREPARATION

  • Routine checks of anesthesia machine, extension circuit, emergency airway equipment, suction and 
resuscitation medications are imperative because access to additional equipment and anesthesia providers are limited. Usually, two infusion pumps and an invasive pressure transducer are available in each lab. At UCSF, a glidescope is located outside the EP control room. Contact the off-site anesthesia technician if you need any additional equipment. 

  • Blood products: are usually not required, but a blood type and antibody screen should be current. 

  • Antibiotic is not indicated for this percutaneous procedure. 


ACCESS/FLUIDS

  • At UCSF, the EP nurse will start a peripheral IV in the pre-op holding area, usually 18 or 20 gauge (left arm). 

  • An additional 18 gauge IV is recommended. However, remember that the introducer sheaths placed by the proceduralist may be used for central venous access. As a heparin infusion is necessary prior to transseptal puncture, the EP team would use the right IJ sheath so the EP nurse cab draw ACT samples 
from the femoral sheath without contamination. In the absence of RIJ access, the heparin can be infused through the PIV (some anesthesia provider prefer a separate PIV).
  • Anticipated blood loss is minimum, usually associated with initial access and flushing of the sheaths. 

  • Continuous irrigation of ablation catheters (1 to 2 L total) and sheath (30 mL/hour each), may add significant volume and may prompt diuretic use at request of the proceduralist. 


MONITORS

  • Standard ASA monitors: The EP staff will assist you in placing radiolucent ECG leads to ensure that they 
do not interfere with the fluoroscopic images or the rest of electrophysiology monitors. Sometimes, the anesthesia ECG leads can be connected to the mapping system directly. 

  • Invasive arterial monitor is placed due to concerns of perforation during PVI. The patient’s cardiopulmonary co-morbidities should determine whether pre-induction arterial catheter is necessary. 

  • Temperature in patients having LA ablations should have esophageal temperature probe placed near the posterior wall of the LA to monitor for excessive heat injury and the risk of atrial perforation. Its position can be confirmed by fluoroscopy. A lower body forced-air warming blanket will be used. 

  • Urinary bladder catheter is placed due to the length of the procedure. 


ANESTHETIC TECHNIQUES 


  • Anxiolytic premedication should not be given routinely in the holding area as most ambulating patients 
(at UCSF) are expected to walk into the EP lab and position themselves up-right on the table while monitors and patches are placed. 

  • Broncho-dilator, anti-reflux medication and antacid should be given as indicated by the anesthetic technique and the patient’s co-morbidities. 

  • The anesthetic of choice for PVI performed at UCSF is GA, due to the length of the procedure and lower incidence of pulmonary vein reconnection. Induction of GA and secure the airway with ETT according to the patient’s history and exam. In the absence of any contraindication, either succinylcholine or a non- depolarization agent can be used. 

  • The advantage of succinylcholine is that, in the case of left atrial (appendage) thrombus discovered on the TEE exam, the patient can be awoken quickly without residual paralysis.
  • The advantage of a non-depolarizing agent is that the patient will be paralyzed and this decreases the risk of bucking or biting during TEE probe insertion. Usually the TEE exam is comprehensive and takes 15 to 45 minutes, which is enough time for twitch to appear and the muscle relaxation reversed.
  • Alternatively, the TEE can be performed under MAC, if the suspicion of thrombus is high and the patient is sick, before deciding if GA and ablation are indicated.
  • The choice of maintenance of anesthesia is up to the anesthesia provider. The local anesthetic infiltration decreases the amount of pain of the vascular access, so minimal intra-operative opiate is needed. The goal is to maintain hemodynamic stability. The choice of agent has little effect on the procedure itself. Repeat neuromuscular blockade is avoided in order to detect phrenic never stimulation. Consider utilizing IV acetaminophen. 

  • Emergence: Following anti-coagulation reversal, removal of the venous sheaths, and manual hemostasis, most patients are extubated in the procedure room. Special caution should be made to avoid excessive 
 coughing, vomiting, and bending at the waist during extubation immediately following hemostasis. EP staff often applies additional manual compression during extubation. Attention to suctioning the oropharynx and ET tube, prophylactic antiemetic treatment. Alternatively, in the absence of contra- indications, deep extubation is an option.
  • Recovery after GA will be in the 4th floor PACU. Patients who had MAC may be recovered in the EP holding room unless the anesthesia provider feels that additional monitoring is necessary in the PACU or ICU due to co-morbidities or intra-operative events, or if the recovery is expected to exceed the hours of EP staff. Depending on the size of the sheath and the use of anti-coagulation, the patient will need to remain supine with the hips straight for 4 to 6 hours because of risk of bleeding.

KEY PROCEDURE-RELATED POINTS

  • Often, a post-intubation, pre-ablation TEE is performed to rule out intra-cardiac thrombus, especially in 
the left atrial appendage. The EP may bypass a TEE if the patient is in sinus rhythm, has consistently therapeutic INR with warfarin, or is on a direct anti-Xa or anti-thrombin inhibitor for more than 30 days without a missed dose. Here at UCSF, TEE is performed by the echocardiography team. Both the echo fellow AND the echo attending have to consent the patient SEPARATELY (another reason to avoid midazolam). 

  • Access is primarily through sheaths placed in the femoral veins by the proceduralist. Local anesthetic is used even for patient under GA. This is performed by the EP fellow, usually prior to attending time out. 

  • Trans-septal access increases the risk of thromboembolism, and requires heparinization. The anesthesia provider will be asked to give the bolus dose, while the EP staff will manage the infusion and check ACT. 

  • Hemodynamic fluctuation is often seen, usually associated with tachy- or brady-cardia, and pacing. The changes are often self-limiting, but may require treatment. 

  • Infusion of isoproterenol, a non-selective beta agonist with chronotropic, dromotropic, inotropic and vasodilatory effects, is commonly used for elicit/evaluate tachyarrythmias and is administered by the EP nurse. Phenylephrine infusion is commonly used to counteract the vasodilation effect. 

  • AF during the procedure may require direct current cardioversion.
  • To avoid phrenic nerve injury, pacing is performed before any energy delivery. Diaphragm movement 
would indicate phrenic nerve capture, and the catheter will be repositioned.

POTENTIAL COMPLICATIONS

  • Arrhythmia that is hemodynamically significant is always a risk. 

  • Vascular complications at the access site are not uncommon and range from self-limited site hematoma to retroperitoneal bleeding requiring urgent/emergent vascular surgery interventions. Resuscitation with fluids, blood products, and vasoactive medications may be necessary. 

  • Aortic perforation is a relatively rare complication that can occur during trans-septal puncture with a specialized needle (Brockenbrough) and the advancement of trans-septal sheath (Mullins). 

  • Cardiac perforation may occur due to catheter manipulation, during Trans-septal puncture or as a result of ablation. This may result in pericardial effusion, and potentially causing tamponade. This is usually 
indicated by persistent hemodynamic instability unrelated to the induced arrhythmia and refractory to routine vasoconstrictors and fluid. The EP team should be informed when this is suspected. Blood products should be ordered immediately. Consider reversing anticoagulation in consultation with the proceduralist. One or more of the femoral sheaths can be used for volume resuscitation. The management of effusion varies:
  • “Wait-and-watch” approach when the effusion is small and self-limiting,
  • Emergent pericardial drain placement,

  • Rapid mobilization for surgical decompression of the tamponade.
  • Left atrial esophageal fistula is often a late complication that occurs after significant injury to the posterior wall of the LA. This injury is catastrophic. 

  • Stroke is possible due to the increased risk of thromboembolism with left sided catheter. In addition, the trans-septal access creates a temporary path for paradoxical embolism. 

  • Phrenic nerve injury. This is more common with cryoablation than the RF ablation commonly used at UCSF. 


SPECIAL ERGONOMIC CONSIDERATIONS

  • Extensions on breathing circuit, oxygen supply, IV tubing, and infusion tubing are necessary to allow the 
unobstructed movement of the fluoroscopy equipment. Consider consolidating and securing monitors, circuits, and tubing such that they clear the C-arm, biplane and avoid tangling. Tourniquets and blue clamps are often useful. The patient’s arms will be secured, padded and tucked, limiting our access. One should consider attaching two pre-flushed infusion lines that can be used for anesthetic agents such as propofol or remifentanil, and vasoactive agents. 

  • Hazards to the anesthesia provider
  • Equipment is in motion
  • Be aware of the c-arm when it is in motion as it can move quickly and endanger heads and shins and may snag loose wires and tubings.
  • Ionizing radiation
  • 
Consider time (limiting exposure), distance (inverse square law), and shielding (both garments and barriers) when in ionizing radiation environments. Particular attention should be granted to protecting the lens of the eye, thyroid, hematopoietic centers in long bones, and reproductive organs as these are particularly sensitive to ionizing radiation. The exposure is greatest as it exits the collimator (the part below the table) in path to the image intensifier (the part above the patient). However, scatter radiation is produced as the X ray encounters items in its path (the patient). Areas on the body that are often overlooked (“weak spots”) include neck, shoulder/arm pits, and back. Lead (radiation protective) garments should cover the neck to the knees and are designed to be worn when facing the source.
  • Magnetic fields
  • At UCSF, one of the EP rooms (EP1) is equipped with the Siemens Stereotaxis NIOBE® magnetic navigation system that can be used to manipulate wires and catheters in the patient’s body. The magnets are material and cannot be turned off, but the magnetic field is tempered when in the stored position. The magnetic field is not on par with the electromagnet used in MRI; however, MRI precautions are recommended.

DURATION 5 - 8 hours

REFERENCES

Benjamin EJ, Wolf PA, D’Agostino RB, Silbershatz H, Kannel WB, Levy D. Impact of atrial fibrillation on the risk of death: the Framingham Heart Study. Circulation 1998;98:946-52.

Camm AJ, Lip GY, De Caterina R, et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation: an update of the 2010 ESC Guidelines for the management of atrial fibrillation. Developed with the special contribution of the European Heart Rhythm Association. Eur Heart J 2012; 33:2719. 

Di Biase L, Conti S, Mohanty P, Bai R, Sanchez J, Walton D, John A, Santangeli P, Elayi CS, Beheiry S, Gallinghouse GJ, Mohanty S, Horton R, Bailey S, Burkhardt JD, Natale A. General anesthesia reduces the prevalence of pulmonary vein reconnection during repeat ablation when compared with conscious sedation: results from a randomized study. Heart Rhythm. 2011;8(3):368-72.

Falk RH. Atrial Fibrillation N Engl J Med. 2001 Apr 5;344(14):1067-78.


Malladi V, Naeini PS, Razavi M, Collard CD, Anton JM, Tolpin DA. Endovascular ablation of atrial fibrillation.Anesthesiology. 2014;120(6):1513-9.


Wazni O1, Wilkoff B, Saliba W. Catheter ablation for atrial fibrillation N Engl J Med. 2011 Dec 15;365(24):2296-304.

 

 

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This information is meant to serve as an educational resource. Clinicians should use their own professional judgment in the care of any individual patient as the guidance contained in this document may not be appropriate for all patients or all situations.