379

CH20

ATR

iAl FibR

illATio

n

Prevention of postoperative AF, if possible, is the preferred approach; β-blocking agents have consistently been shown to reduce postoperative AF and should be started preoperatively and continued postoperatively.144 Amiodarone, ideally in conjunc-tion with β-blockers, seems to be superior to β-blockers alone, but the long half-life of the drug is such that it is best started several days before cardiac surgery.145,146 Because many patients go to cardiac surgery urgently, the optimal use of prophylactic amioda-rone is limited to elective patients. The drug also has significant side effects, including postoperative bradycardia and, occasionally, postoperative pulmonary damage. Neither digoxin nor calcium channel antagonists have been shown to prevent postoperative AF, and they should not be used for this indication.144 Interestingly, despite uncertain value in postcardioversion prophylaxis, statin therapy started preoperatively appears to reduce the risk of post-operative AF.147,148

If a patient develops postoperative AF, the risks of anticoagula-tion with recent surgery must be carefully weighed against poten-tial benefits of thromboembolism prophylaxis. No prospective trials have evaluated postoperative anticoagulation as part of the treatment of postoperative AF. Consensus guidelines suggest that heparin should be limited to patients with postoperative AF who are deemed to be at higher risk of thromboembolism, particularly those who have had a prior stroke or TIA. For patients with arrhyth-mia that has persisted for at least 48 hours, warfarin anticoagula-tion is recommended, without heparin overlap, with an aim to continue the drug for approximately 4 weeks after restoration of sinus rhythm.149 Naturally, extreme care needs to be taken in adjust-ing anticoagulation in this patient population, and a significant proportion of patients may be deemed to be at a higher than average risk of bleeding, for whom anticoagulation is considered inadvisable.

The post–cardiac surgery patient may be hemodynamically unstable; consequently, ventricular rate control in AF is important. On the other hand, many patients already have a relatively well-controlled ventricular response because they are on β-blocking agents; the concern for ischemia is relatively low because those with coronary artery disease will have had coronary revascularization.

Pericardioversion AnticoagulationThe pericardioversion period represents a special situation in terms of thromboembolic risk. After restoration of sinus rhythm, atrial mechanical function may be diminished, and LAA emptying velocities may be even lower than they were during AF.137 Several antiarrhythmic drugs with negative inotropic properties, including propafenone and sotalol, have been shown to worsen postcardio-version atrial function; thus they have the potential for promoting thromboembolism.138 The return of atrial function generally occurs within 7 to 14 days after restoration of sinus rhythm, a period of high thromboembolic risk. Thus, anticoagulation is mandated during this time, even if a TEE showed no thrombus immediately prior to cardioversion and even in patients who are deemed not to need long-term warfarin for AF (i.e., those with lone AF; Figure 20-2).139,140 Current data suggest no clinical benefit to early transesophageal-guided cardioversion followed by warfarin over a strategy of 3 to 4 weeks of warfarin before cardioversion and con-tinued after cardioversion, although there may be some modest cost savings.141-143

Atrial Fibrillation Following Cardiac SurgeryAF in the post–cardiac surgery setting represents a unique situa-tion. AF develops in 30% to 60% of cases and is more likely to occur with valvular surgery than with isolated bypass surgery. As with other types of AF, older age is a major risk factor. AF most often develops within the first 72 hours after surgery and may be asymp-tomatic, or it may be associated with rapid rates and significant symptoms. Unlike most other types of AF, postoperative AF tends to be self-limited and rarely recurs more than 4 weeks after surgery.

The approach to postoperative AF comprises four steps: the first is perioperative pharmacologic prophylaxis; if that fails, anticoagu-lation, electrical or pharmacologic therapy, and/or ventricular rate control is appropriate. In addition, several intraoperative measures have been investigated for their effect on prophylaxis of postopera-tive arrhythmia.

FIGURE 20-2  Algorithm  for anticoagulation pericardioversion. AF, atrial fibrillation; CV, cardioversion;  INR,  International Normalized Ratio; TEE,  transesophageal echocardiography. 

AF �48 hr

Cardiovert

Anticoagulate acutelywith heparin if INR

�2.0 then cardiovert

Consider aspirin inpresence of structural

heart disease

Continue warfarin/dabigatrananticoagulation for at

least 1 month dependingon risk factors

Yes

NoRisk factors present?

AF �48 hror unknown

duration

TEE

No thrombuspresent

Thrombuspresent

Cardiovert, warfarin/dabigatranfor at least 1 month; if

risk factors present, thenanticoagulate for life

Warfarin/dabigatran for 4weeks after which consider

TEE, or proceed to CV

Warfarin/dabigatranfor 3-4 weeks Cardiovert

Warfarin/dabigatran forat least 4 weeks, for life

if risk factors presentYes

Heparin ifINR �2.0

No

AFtolerated?