Atrial Fibrillation Represents the Single

Atrial fibrillation represents the single most common form of cardiac arrhythmias and is identified in 5% of all people above the age of 69, affecting an estimated 2.2 million people in the U.S. alone. [Lawrence Rosenthal, (2009)] it is a tachy arrhythmia with diverse triggers ('including sympathetic and parasympathetic stimulation') that initiate an episode and favorable substrates that maintain it. Currently, the exact causes that trigger an AF episode are not totally understood but multiple mechanisms are found to be in play. One such theory is the 'multiple wavelet theory' that suggests that the 'fractionalization of waves' that travel along the atrium leads to 'daughter wavelets' that results in multiple wavelet reentry. This theory proposes that the number of daughter wavelets maybe determined by different factors including the reduction in 'atrial conduction velocity', decreased 'atrial refractory period' and atrial mass. [Lawrence Rosenthal, (2009)] More recent studies have implicated ectopic sites in the pulmonary vein and the vena caval junctions as potential triggers of AF. This theory has been attested by cases of patients recovering after radio frequency ablation of the vena caval junctions. [Maurits et.al 2001]

Typically, during an AF episode, the atrium may beat up to 300 times per minute while the ventricles may beat up to 175 times per minute . During AF, the conduction signal may originate in a different location of the atria (other than the usual SA node) or may be originating from the adjacent left pulmonary vein. This results in abnormal contractions of the atrium that significantly affects ventricular filling.. The result is pooling of blood in the atria that may lead to formation of clots. These clots may dislodge from the atrium and travel to other parts of body and pose a high risk for stroke. Also, the abnormal electrical impulses that arrive via the AV node cause the ventricles to beat much faster leading to inefficient pumping of blood. [NIH]

There are some symptoms associated with the hemodynamic instability caused by AF. The rapid and inefficient contractions of the ventricles affect the regular supply of blood to the lungs and other parts of the body. Typical symptoms of AF include palpitation (feeling of a fast beating heart), shortness of breath, fatigue, chest tightness, confusion, etc. [NIH]. Besides the general physical examination to check the heart beat and blood pressure and the blood tests to check for hyperthyroidism, there are special diagnostic tools available to detect AF. One of the most common tests is the EKG (electrocardiogram) test that measures the electrical activity of the heart. There are two different types of EKG namely the Holter monitor and the Event monitor. The Holter monitor is also known as ambulatory EKG. It is a small electronic device fitted with a few electrodes that are attached to the chest region and worn by the patient for a day or two to record the electrical activity of the heart during the normal activities of the patient. The patient is also asked to record the time and duration of abnormal events, which can later be cross-referenced by the doctor with the Holter readings. Event monitor, on the other hand is a similar device that records the electrical activity by the push of a button so that the patient can record his cardiac condition when he senses the symptoms. Echocardiogram is another important non-invasive diagnostic tool for AF. This test uses sound waves to produces an image of the heart and helps the cardiologist observe the different regions of the heart and assess their performance. [NIH]

Treatment for AF involves different approaches and may also be decided by the cardiologist depending on the nature of the AF. Paroxysmal AF, which lasts for a short duration (maximum few days) is usually treated with drugs that aim to control the sinus arrhythmia while cases of persistent AF maybe treated either for rhythm control or ventricular rate control. Drugs such as digoxin, (increases contraction and reduces rate) beta-blockers such as atenolol, metoprolol and calcium channel blockers such as verapamil are some of the avilable medications that try to improve the atrial refractory period to control AF. [Josephson, 2003]

Restoration of cardiac rhythm by means of electrical cardioversion is the most common intervention for patients. Since thromboembolism is one of the high risk factors in an AF episode, anticoagulation therapy is part of the treatment. In cases of patients presenting with AF episode lasting more than 12 hours or in whom the duration of arrhythmia is unknown it is advisable to administer anticoagulation therapy for 3 weeks before cardioversion. In cases of emergency, transoesophageal echocardiography prior to cardioversion is a common procedure to check for any thrombi formation in the atrium. A course of anticoagulation therapy should be continued after cardioversion to eliminate the risk of stroke. [Vias Markides, 2003]