Cardioversion (for atrial fibrillation or atrial flutter)

Wilson Cui, MD PhD, Matt Dudley, MD

Cardioversion Draft, 8/2014 

PROCEDURE


Cardioversion (for atrial fibrillation or atrial flutter)

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 patients usually have some underlying heart disease such as hypertension, coronary artery disease, mitral valve disease (including rheumatic heart disease), or heart failure. The association with hyperthyroidism, pulmonary embolism, obstructive pulmonary diseases, and heavy alcohol use are also well documented.

Atrial flutter (AFL) is rare in young adults with incidence rates range from 5 in 100,000 (< 50 years old) to 587 in 100,000 (> 80 years old). It is often associated with underlying heart disease. Many diseases that cause AF can also cause AFL, and AFL can also be a side effect of anti-arrhythmic agents used to suppress AF. Common risk factors for developing AFL include male gender, advanced age, heart failure and chronic obstructive lung disease. Lastly, both AF and AFL can occur after cardiac and thoracic surgeries.

In general, cardioversion is performed in those patients who are symptomatic. Thromboembolic disease is a major cause of morbidity and mortality in patients with AF or AFL. The use of transesophageal echocardiography can rule out any intracardiac thrombus, especially in the left atrial appendage, and facilitate earlier cardioversion.

DISEASE BACKGROUND AND PROCEDURAL DESCRIPTION

In AFL, the likely etiology is a single macro-reentrant atrial circuit. So called “typical” flutter involves a region of cardiac tissue that connects the tricuspid valve annulus and the inferior vena cava (IVC), which is the main target in electrophysiologic study and catheter ablation. In the absence of this ridge of tissue, it is called an “atypical” flutter, and the reentrant circuit can be elsewhere in the right atrium (RA) or infrequently left atrium (LA). On ECG, AFL usually shows the typical sawtooth wave (atrial depolarization at around 300 bpm) with a regular ventricular response at a ratio of 1:2 or 1:4, although odd ratio or variable AV conduction is possible. Patients with AFL will choose watchful waiting as this arrhythmia may spontaneously revert to sinus. On the other hand, catheter ablation is highly successful in eliminating typical aflutter. Those patients who are waiting for ablation may undergo electrical cardioversion.

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. Besides emergency cardioversion in hemodynamically unstable patients, elective cardioversion is usually performed in patients with new onset AF, persistent AF who is symptomatic, or those initiating long term anti-arrhythmic agents such as sotolol or dofetilide. For this last group, UCSF typically admit these patients for the initiation of the anti-arrhythmic drug, which can have serious side effects including QT prolongation, ventricular arrhythmia and heart failure, and schedule a cardioversion preemptively in case they do not revert to sinus after 48 - 72 hours, which they often do.

The energy of the cardioversion will be determined by the EP physician. Typically AFL will require less energy than AF for successful conversion. The placement of the external patch is usually posterior- anterior, but in cases of pre-existing pacemaker or internal cardioverter-defibrillator, the EP physician will use a safe alternative.

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 there is a risk for airway obstruction during TEE insertion and examination. 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. 

• Anti-platelet agents and anticoagulants should be noted. Given the risk of thromboembolism associated with AF or AFL and the noninvasive nature of cardioversion, they are not stopped. However, the echocardiographer may be appropriately concerned if INR is significantly above the therapeutic range due to the risk of airway trauma and bleeding during probe insertion. 


PRE-OPERATIVE PREPARATION 


• EP Work flow will sometime prefer to have the cardioversion take place in the nook at the far end of the holding room thus eliminate the need to use the EP lab and the subsequent room turn over and cleaning. Ultimately the anesthesia provider makes the decision. 

• Routine checks of emergency airway equipment, oxygen, suction and resuscitation medications are imperative. At UCSF, a glidescope is located outside the EP control room. The EP staff, as a rule, will call the anesthesia technician to bring an anesthesia machine and a cart if the cardioversion is planned in the holding room. In some circumstances (e.g. cardioversion without TEE in a patient with a benign airway exam) the anesthesia provider may feel comfortable providing a brief MAC while monitoring using the EP monitors and charting vital signs and medications manually on APEX without the anesthesia machine. 


ACCESS/FLUIDS 


• At UCSF, the EP nurse will start a peripheral IV in the pre-op holding area.

MONITORS

• Standard ASA monitors: In the holding room, the anesthesia provider may choose to connect monitors to 
the anesthesia machine or rely on the monitors placed by the EP staff as long the vital signs can be either automatically imported to the APEX record (by selecting the right device) or manually entered without affecting patient care. Rarely, the irregularity of pulses can frustrate the non-invasive BP cuff. 

• If invasive arterial monitor is needed in a hemodynamically unstable patient, then perhaps the ICU would be a better place for the cardioversion. 


ANESTHETIC TECHNIQUES 


• Anxiolytic premedication should not be given routinely until the patient has been consented by the following: the EP fellow/attending, the echocardiography fellow (if TEE is planned) and the echocardiography attending (separate from the fellow).
• Broncho-dilator, anti-reflux medication and antacid should be given as indicated by the anesthetic plan and the patient’s co-morbidities, but is rarely necessary for MAC cases. 

• The anesthetic of choice for cardioversion, even with TEE, is MAC. The anesthetic goal is to provide sedation and comfort during TEE exam and ensure amnesia for the jolt of electricity. The most stimulating portion is usually the TEE probe insertion. Most echocardiographers prefer to topicalize the airway as they typically do for patients in the echo lab. However, some anesthesia providers are concerned about blunted airway reflexes and the risk of airway obstruction after the procedure, and the topicalization step can be skipped. A small propofol bolus will usually facilitate the passing of the probe. The use of GA should be determined by the patient’s cardiopulmonary co-morbidities and airway assessment. 

• The emergence after MAC should be straight forward, which involves discontinuing the sedation and monitoring for any airway obstruction before either leaving the EP lab or handing off the patient to the EP nurse if already in the holding room. Patients after GA will recover in the 4th floor PACU. 


KEY PROCEDURE-RELATED POINTS 


• The insertion of the TEE probe is most stimulating and stressful portion of the procedure as the patient may buck, cough, obstruct and/or desaturate during this time. Jaw thrust, and turning the head to one side or the other by the anesthesia provider may be helpful. Remember to have suction available.

POTENTIAL COMPLICATIONS

• Airway obstruction and desaturation, especially with TEE. Airway trauma with potential bleeding. 

• Unsuccessful cardioversion. While most patients revert to sinus rhythm after a single shock, this may not be the case in patients with underlying structural heart disease, such as those with large atria, or those with long standing history of AF. Additional shockS with higher energy may be used. The EP team will decide when to stop. 

• Arrhythmia or conduction abnormality is sometime observed after cardioversion, but is often transient. 

• Stroke is a known complication, even in weeks after restoring sinus rhythm. Patients are instructed to 
continue their anti-coagulation medications. 

• Skin burn 


SPECIAL ERGONOMIC CONSIDERATIONS 


• If done in the holding room, there is limited space to accommodate an EP nurse with his 12-lead ECG 
machine and monitors, the anesthesia provide(s) with an anesthesia machine, monitors and a cart, a two- member EP team, and a two-member echocardiography team with the TEE machine. If in the EP lab, patient can remain on the gurney. 

• Ensure the patient is positioned properly and arms and other body parts are protected as they may move and be injured during the shock. 

• Stay clear of the patient prior to the delivery of synchronized shock.

DURATION 5 – 45 minutes 


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.

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

Granada J, Uribe W, Chyou PH, Maassen K, Vierkant R, Smith PN, Hayes J, Eaker E, Vidaillet H. Incidence and predictors of atrial flutter in the general population. J Am Coll Cardiol. 2000;36(7):2242.