converted to a normal rhythm with antiarrhythmic treatment, compared to those who have only rate control. af is associated with a reduced quality of life, and while some studies indicate that rhythm control leads to a higher quality of life, the affirm study did not find a difference. a further study focused on rhythm control in patients with af and simultaneous heart failure, based on the premise that af entails a higher mortality risk in heart failure. in this setting, too, rhythm control offered no advantage compared to rate control. in patients with a fast ventricular response, intravenous magnesium significantly increases the chances of successful rate and rhythm control in the urgent setting without significant side-effects. cardioversion cardioversion is a noninvasive conversion of an irregular heartbeat to a normal heartbeat using electrical or chemical means: electrical cardioversion involves the restoration of normal heart rhythm through the application of a dc electrical shock. chemical cardioversion is performed with drugs, such as amiodarone, dronedarone, procainamide, ibutilide, propafenone or flecainide. the main risk of cardioversion is systemic embolization of a thrombus (blood clot) from the previously fibrillating left atrium. cardioversion should not be performed without adequate anticoagulation in patients with more than 48 hours or unknown duration of af. anticoagulation is adequate if warfarin is given with target inr between 2 and 3 for three to four weeks prior to cardioversion, and continued for at least four weeks after cardioversion. cardioversion may be performed in instances of af lasting more than 48 hours if a transesophogeal echocardiogram (tee) demonstrates no evidence of clot within the heart. whichever method of cardioversion is used, approximately 50% of patients relapse within one year, although the continued daily use of oral antiarrhythmic drugs may extend this period. the key risk factor for relapse is duration of af, although other risk factors that have been identified include the presence of structural heart disease, and old age. rate control rate control is achieved with medications that work by increasing the degree of block at the level of the av node, effectively decreasing the number of impulses that conduct down into the ventricles. this can be done with: beta blockers (preferably the "cardioselective" beta blockers such as metoprolol, bisoprolol, atenolol) calcium channel blockers (i.e. diltiazem or verapamil) cardiac glycosides (i.e. digoxin) – have limited use, apart from in the sedentary elderly patient in addition to these agents, amiodarone has some av node blocking effects (particularly when administered intravenously), and can be used in individuals when other agents are contraindicated or ineffective (particularly due to hypotension). diltiazem has been shown to be more effective than either digoxin or amiodarone. drugs used to control the rate of af may cause side effects, especially fatigue and dyspnea. these are avoided by the more radical "ablate and pace" treatment (see below). maintenance of sinus rhythm the mainstay of maintaining sinus rhythm is the use of antiarrhythmic agents. recently, other approaches have been developed that promise to decrease or eliminate the need for antiarrhythmic agents. antiarrhythmic agents the anti-arrhythmic medications often used in either pharmacological cardioversion or in the prevention of relapse to af alter the flux of ions in heart tissue, making them less excitable, setting the stage for spontaneous and durable cardioversion. the agents work by prolonging the effective refractory period (erp) either by blocking sodium ions (class i drugs) or by blocking potassium ions (class iii drugs) or a mixture of both. these medications are often used in concert with electrical cardioversion. catheter ablation in patients with af where rate control drugs are ineffective and it is not possible to restore sinus rhythm using cardioversion, non-pharmacological alternatives are available. for example, to control rate it is possible to destroy the bundle of cells connecting the upper and lower chambers of the heart – the atrioventricular node – which regulates heart rate, and to implant a pacemaker instead. this "ablate and pace" technique has an important place in the treatment of af< as it is the only reliably effective method for relieving the symptoms of the arrhythmia and can be used when other methods have failed (as they do in up to 50% of cases of persistent af). although this procedure results in a regular (paced) heart rhythm it does not prevent the atria from fibrillating and therefore long-term warfarin anticoagulation may still be required. ablation (af ablation) is a method that increasingly is used to treat cases of recurrent af that are unresponsive to conventional treatments. radiofrequency ablation (rfa) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. other energy sources include laser, cryothermy and high intensity ultrasound. the energy emitting probe (electrode) is placed into the heart through a catheter inserted into veins in the groin or neck. electrodes that can detect electrical activity from inside the heart are also inserted, and the electrophysiologist uses these to "map" an area of the heart to locate the abnormal electrical activity before eliminating the responsible tissue. efficacy and risks of catheter ablation of af are areas of active debate. a worldwide survey of the outcomes of 8745 ablation procedures demonstrated a 52% success rate (ranging from 14.5% to 76.5% among centers), with an additional 23.9% of patients becoming asymptomatic with addition of an antiarrhythmic medication. in 27.3% of patients, more than one procedure was required to attain these results. there was at least one major complication in 6% of patients. death has been found to occur in 1 in 1000 people who undergo this procedure. a thorough discussion of results of catheter ablation was published in 2007; it notes that results are widely variable, due in part to differences in technique, follow-up, definitions of success, use of antiarrhythmic therapy, and in experience and technical proficiency. cox maze the cox maze procedure is an open-heart surgical procedure intended to eliminate af and was first performed at st. louis' barnes hospital (now barnes-jewish hospital) in 1987. "maze" refers to the series of incisions made in the atria, which are arranged in a maze-like pattern. the intention was to eliminate af by using incisional scars to block abnormal electrical circuits (atrial macroreentry) that af requires. this procedure required an extensive series of endocardial (from the inside of the heart) incisions through both atria, a median sternotomy (vertical incision through the breastbone) and cardiopulmonary bypass (heart-lung machine). a series of improvements were made, culminating in 1992 in the cox maze iii procedure, which is now considered to be the "gold standard" for effective surgical cure of af. the cox maze iii is sometimes referred to as the "traditional maze", the "cut and sew maze", or simply the "maze". minimally invasive maze procedures minimaze procedures are minimally invasive versions of the original cox maze procedure but without cardiac incisions. these procedures do not require a median sternotomy (vertical incision in the breastbone) or cardiopulmonary bypass (heart-lung machine). they use laser, cryothermy, radiofrequency, or acoustic energy to ablate atrial tissue near the pulmonary veins and make other required ablations to mimic the maze. minimally invasive surgical (endoscopic) maze procedures are now routinely conducted at hospitals around the us. this approach was developed in the early 2000s. the ex-maze is a minimally invasive procedure, first reported in 2007, that also creates a lesion pattern across both atria epicardially on the beating heart. as with other procedures off-bypass, the surgeon can confirm that af corrects to normal sinus rhythm during the procedure. laparoscopic instruments are used to access the pericardium through the diaphragm. like many heart-cauterizing instruments, the ex-maze device uses heat generated by a radiofrequency coil. the coil is inside a plastic tube that uses suction to maintain contact against the beating heart's surface. research two 2021 systematic reviews and meta-analyses concluded that more than 1 g/d marine omega-3 fatty acids is associated with an increased risk of atrial fibrillation (af).