All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor ----------------------------------------------------------- December, 2000 - A-fib and atrial flutter often occur after heart surgery. It happens in as many as 40% after bypass surgery and 60% after valve surgery. Most a-fib episodes happen in the first few days after surgery, with peak episodes on days 2 to 3. A-fib after surgery increases complications, length of ICU stay, length of hospitalization, and medical costs. In 3,855 heart surgery patients, a-fib after surgery was linked to: 1) longer ICU stay: 3.6 days with a-fib versus 2 days without it 2) more likely ICU readmission: 13% versus 4% 3) higher risk for heart attack while still in the hospital: 7.4% versus 3.4% 4) persistent heart failure: 4.6% versus 1.4% 5) greater need for ventilator: 10.6% versus 2.5% In another study, the increase in hospital stay linked to a-fib in heart surgery patients was 5 days, with an increased hospital cost of $10,000. ------------------------------------------------------------ Hypokalemia = low potassium levels. Hypokalemia after heart surgery is linked to a-fib. One study of 2,402 patients found that blood a potassium level under 3.5 mEq/liter almost doubled risk for a-fib. Hypomagnesemia = low magnesium levels. Blood magnesium level often falls after surgery. Giving 2 grams of IV magnesium chloride after bypass surgery was studied in a double-blind, placebo-controlled trial of 100 heart surgery patients. Risk of after-surgery a-fib was reduced in patients with normal magnesium levels by 17% and by 37% in patients with low magnesium levels. ------------------------------------------------------------ A-fib usually happens one to 5 days after heart surgery and usually goes away on its own. Over 90% of patients with post-surgery a-fib who have no history of it are in normal rhythm 6 to 8 weeks after surgery. In 2,972 patients with post-surgery a-fib, it had no impact on early stroke but was linked to later stroke, only when accompanied by low heart output (4% stroke rate in a-fib patients versus 2% in non-a-fib patients). ------------------------------------------------------------ MINIMALLY INVASIVE SURGERY One report of 75 patients found little difference in post-surgery a-fib between patients having minimally invasive bypass surgery (26%) versus conventional bypass surgery (33%). Results were similar in another study of 110 patients. Rate of a-fib was 24% for less invasive versus 20% for regular bypass surgery. In contrast, 34 patients who had minimally invasive surgery showed less a-fib (12%) than 747 patients having standard bypass surgery (26%). A-fib was much less with minimally invasive surgery in another study of 137 patients (12% versus 32% for standard bypass surgery). ------------------------------------------------------------ PREVENTING A-fib AFTER HEART SURGERY Due to the high rate of post-surgery a-fib, it is recommended that therapy be given before surgery to help prevent a-fib from occurring. BETA-BLOCKERS The most effective prevention is beta-blocker use, with or without digoxin (Lanoxin). Studies have shown that these drugs lower a-fib risk from 40% to 20% in post-bypass surgery patients and from 60% to 30% in valve surgery patients. One study found an a-fib risk of 34% without and 9% with beta-blocker use. Another study found an a-fib risk of 20% without and 10% with beta-blockers. This benefit is seen when beta-blockers are started before or just after surgery. DIGOXIN Digoxin, given before or right after surgery, has helped patients in some - but not all - studies. Two studies found that digoxin alone did not prevent post-surgery a-fib. However, giving digoxin may make beta-blockers more effective. One study showed lower risk of post-surgery a-fib with digoxin plus a beta-blocker, than with digoxin or a beta-blocker alone. SOTALOL Sotalol is a class III anti-arrhythmic drug with beta-blocking activity. It reduces risk of post-surgery a-fib. Oral sotalol works when started 24 to 48 hours before surgery. Sotalol may be more effective than a regular beta-blocker for preventing after-surgery a-fib. One study gave 191 patients after surgery either 160 mg BID sotalol or 75 mg metoprolol per day. Risk of a-fib was lower with sotalol (16%) versus metoprolol (32%). AMIODARONE Amiodarone given by IV or as pill, is also effective to prevent post-surgery a-fib. One study gave 124 patients either amiodarone or placebo, started at least 7 days before surgery. A-fib was seen in 25% of amiodarone patients versus 53% of placebo patients. Amiodarone patients stayed in the hospital 6.5 days versus 7.9 days for placebo patients, lowering hospital costs by $8,000. NOTE: There are some concerns with this trial. There was a high rate of a-fib in the placebo group despite many patients already being on a beta-blocker, which should have prevented at least 50% of post-surgery a-fib according to every other trial ever done. Another trial of 140 patients given IV amiodarone started 3 days before surgery and continued 5 days after surgery showed a-fib in 12% of amiodarone patients versus 34% of placebo patients. There are drawbacks to amiodarone before surgery, including the need to identify high risk patients a week before their surgery, risk of slowing heart rate too much - especially in the elderly - and a rare risk of post-surgery breathing failure. IV amiodarone given right after surgery reduces post-surgery a-fib without much risk. This was shown in the ARCH trial, which gave 300 patients placebo or one gram of IV amiodarone over 24 hours. IV amiodarone reduced risk of a-fib by 35% versus 47% for placebo, but did not reduce length of hospital stay. CCBs (CALCIUM CHANNEL BLOCKERS) Calcium channel blockers are not very effective for this purpose. CHF patients should not usually take these drugs. CLASS ONE ANTI-ARRHYTHMIC DRUGS Using these drugs to prevent post-surgery AF is not well studied. PACING (PACEMAKERS) Atrial pacing has been studied. Although single and multiple site atrial pacing helps paroxysmal a-fib, we don't know if it helps post-surgery a-fib. One pilot study of 61 patients given either no pacing, right atrial pacing, or bi-atrial pacing, found no difference in post-surgery a-fib between the 3 groups. Another study of 100 patients given either right atrial pacing or no pacing showed similar results. Other studies have found that post-surgery "overdrive" atrial pacing was effective. In one study, 154 patients were given either no pacing; or right atrial, left atrial, or bi-atrial pacing for 72 hours. Beta-blockers were given to all patients. Compared to no pacing, a-fib risk was lower in every paced group. Pacing reduced length of hospital stay from 8 to 6 days. Other studies have found that bi-atrial pacing is more effective than single site atrial pacing. One study of 132 patients given either biatrial, left atrial, right atrial, or no pacing for 5 days found that a-fib risk was lowest with bi-atrial pacing. Bi-atrial pacing reduced hospital stay by almost 3 days over no pacing. RECOMMENDATIONS TO PREVENT POST-SURGERY A-fib Beta-blockers are clearly most useful. If possible, they should be given as soon as possible after heart surgery. Best amount of time to continue beta-blocker use to prevent post-surgery a-fib is unknown. However, since many heart surgery patients have a need for continued beta-blocker use anyway (for coronary artery disease, previous heart attack, high blood pressure or CHF), indefinite beta-blocker use should be considered. ------------------------------------------------------------ TREATING POST-SURGERY A-fib Despite preventive therapy, many patients still have a-fib after heart surgery. Treating this a-fib is similar to regular a-fib treatment but there is usually no need for long-term therapy. This kind of a-fib usually reverts to normal rhythm on its own in 2 months or less in more than 90% of patients. Treatment may be rate control, or conversion using drugs or electric conversion. RATE CONTROL Given the temporary nature of this kind of a-fib, controlling ventricular rhythm and giving anti-coagulation (blood thinner) therapy is a pretty safe strategy. Rate control is best done with beta-blockers. IV esmolol, a beta-blocker with a short half-life, can be given for immediate rate control if there is risk of too-slow heart rate, too-low blood pressure, or spasms in the lungs. Other drugs that block the AV node, such as digoxin, can control ventricular rate in a-fib, but are not more effective than beta-blockers. ELECTRICAL CARDIOVERSION This is not usually done if post-surgery a-fib is well tolerated. However, cardioversion may be necessary for patients with strong symptoms. There are 2 options when the a-fib does not respond to normal cardioversion : 1) Internal, low-energy defibrillation using electrodes or wires that were placed during surgery. 2) A "double defibrillator" technique in which 2 pairs of properly placed external electrodes are fired at once. CARDIOVERSION USING DRUGS A-fib drug cardioversion can be done with class 1A, 1C, or class 3 anti-arrhythmic drugs, given orally or by IV. If a patient's breathing difficulties make anesthesia for electrical cardioversion risky, drugs should be tried instead. The effectiveness of anti-arrhythmic drugs for cardioverting post-surgery a-fib is about the same as using them for a-fib not related to surgery. Although beta-blockers don't often convert a-fib, they may help convert post-surgery AF. One study gave 30 patients with post-surgery a-fib either IV esmolol or IV diltiazem. In the first 6 hours, conversion to normal rhythm was more frequent with esmolol (67%) than with diltiazem (13%). ANTICOAGULATION (BLOOD TINNERS) Since post-surgery a-fib usually doesn't last long, one would expect risk of stroke from this a-fib to be low. However, some patients may be at increased risk for stroke with post-surgery a-fib. Given the potentially devastating effects of a stroke, anticoagulation with IV heparin and then Coumadin (warfarin) is recommended for a-fib after surgery. Even for patients who are converted to normal rhythm within 48 hours, continued Coumadin should be strongly considered. Risk of stroke in patients with post-surgery atrial flutter is unknown. As with a-fib, flutter usually doesn't last long and stroke risk is thought to be low. Just remember that there is an increased risk of bleeding in patients who have just had surgery, so anticoagulation must be given carefully. Title: Arrhythmias After Cardiac Surgery: Atrial Fibrillation and Atrial Flutter Authors: David Bharucha, Roger Marinchak, Peter R Kowey Source: UpToDate 2000