Atrial Fibrillation – [Heart Disease] Partial Listing
New treatment for atrial fibrillation
Atrial fibrillation is an abnormal heart rhythm originating in the atria (top chambers of the heart). Instead of the impulse traveling in an orderly fashion through the heart, many impulses begin and spread through the atria, causing a rapid and disorganized heartbeat.
At one time, atrial fibrillation was thought to be a harmless annoyance. However, now it is known that chronic atrial fibrillation is associated with heart failure, blood clots, a five to sevenfold increase in stroke, and increased mortality from heart disease.
Conventional therapy of atrial fibrillation includes medications, electrical cardioversion, ablation of the atrioventricular node (AV node) followed by a pacemaker, and various surgical procedures.
New medications: Tikosyn
Tikosyn (Dofetilide) is a new medication that is used to convert atrial fibrillation to normal sinus rhythm (NSR). Clinical trials have shown Tikosyn to be effective in converting patients to NSR in about 70 to 80 percent of cases. Tikosyn is an effective new drug, however there is risk of inducing more life-threatening arrhythmias when first beginning the drug and when changing doses. Therefore, Tikosyn is only available to hospitals whose physicians have received the proper training in initiation and dosing of the drug. Also, all patients who begin Tikosyn or have changes in dosing must be placed in the hospital for a minimum of three days for careful monitoring.
Improved safety during cardioversion: use of transesophageal echo:
Electrical cardioversion of patients with atrial fibrillation (AF) to normal sinus rhythm is frequently performed to relieve symptoms, improve cardiac performance and reduce the risk of stroke. If the patient has a preexisting thrombus (clot) inside the left atrial appendage of the heart, there is a risk of stroke during the procedure. In order to decrease this risk, patients undergoing electrical cardioversion are usually treated with anticoagulation medications (blood-thinners) for three weeks before and four weeks after the procedure. The trial studied the use of transesophageal echocardiography (TEE), with short-term anticoagulation, to lower the risk of stroke and bleeding for these patients. The study concluded that certain patients benefit from the TEE-guided strategy, allowing earlier cardioversion and less bleeding complications.
The Maze procedure (Cox-Maze procedure), developed by Dr. Jim Cox, began the surgical approach to treatment of atrial fibrillation. The surgery involves creating precise incisions in the right and left atria to interrupt the conduction of abnormal impulses and to direct normal sinus impulses to travel to the atrioventricular node (AV node) as they normally should. The Maze procedure has been very successful with a 95 % success rate. A number of surgeons have altered the traditional Cox-Maze procedure to focus mainly on the left atrium.
The success of the modified Maze procedures has supported the notion that the isolation of the pulmonary veins and portions of the left atrium can eliminate atrial fibrillation. This has encouraged surgeons to seek out other methods of isolation rather than cutting and sewing. Three alternative energy sources have been used surgically to treat atrial fibrillation: radiofrequency, microwave and cryothermy. The goal of all three is to produce lesions and ultimately scar tissue to block the abnormal electrical impulses from being conducted through the heart and promote the normal conduction of impulses through the proper pathway
Radiofrequency ablation uses radiofrequency energy to heat the tissue and produce lesions on the heart, eliminating the incisions necessary in the Maze procedure. A variety of surgical techniques related to the type of catheter used are common, the dose of energy, and the types of lesions created. Radiofrequency surgical ablation has proved to be successful in 80% of cases. The greatest risk of this procedure is damage to surrounding structures, such as the esophagus.
Cryothermy (also called cryoablation) uses very cold temperatures through a probe (called a cryoprobe) to create lesions. This technique is used commonly during arrhythmia surgery to replace the incisions made during the Cox-Maze procedure. This technique cures atrial fibrillation in close to 80% of people.
Microwave technology uses a special catheter (the Flex-4 catheter) to direct microwave energy to create several lesions on the heart. The lesions block the conduction of abnormal electrical beats and restore a normal heartbeat. The benefit of microwave radiation in comparison to other surgical ablation techniques, is that the depth and volume of heated tissue is more controlled and precise lesions are created, and less charring of the heart’s surface occurs, decreasing the risk of blood clots that may travel to the brain or other organs. Microwave energy cures atrial fibrillation in about 80% of people.
DISCLAIMER: The information provided here is for general informational purposes only, and is provided as a supplement for students enrolled in Meditec’s medical career training courses. The information should NOT be used for actual diagnostic or treatment purposes or in lieu of diagnosis or treatment by a licensed physician.