Atrial Fibrillation after Cardiac Surgery
Cardiac surgery is performed on hundreds of thousands of patients a year, and can have an important beneficial impact on the outcomes of patients with coronary and valvular heart diseases. Despite the favorable recovery of most patients, some will have th
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Gregory K. Feld, MD, University of Caiifornia, San Diego, CA 1. Introduction Atrial arrhythmias, such as atrial fibrillation (AFIB), atrial flutter (AFL) and atrial tachycardia (AT) are relatively common following cardiac surgery [1-2]. Patients undergoing cardiac surgery may be particularly prone to develop atrial arrhythmias for a variety of reasons, including the type of surgery performed, the presence of underlying heart disease and other associated medical conditions such as hypertension, hemodynamic instability or congestive heart failure, pulmonary insufficiency, associated pericardial inflammation, and the increased sympathetic and vagal nervous system activity that accompanies such surgery [1-2], Post-operative atrial arrhythmias may cause significant symptoms including palpitations, shortness of breath, chest pain and even syncope due to the hemodynamic instability that often exists in this setting. If associated with a rapid ventricular response, post-operative atrial arrhythmias may cause ischemia or congestive heart failure, and in the case of atrial fibrillation thromboembolic stroke may even occur. The treatment, and perhaps more importantly the prevention of atrial arrhythmias following cardiac surgery is therefore critical. Fortunately, through extensive experimental and clinical studies significant progress has been made towards delineating the mechanisms and possible treatments for most atrial arrhythmias, including those that occur in the post-operative period following cardiac surgery. For example, clinical studies in man have demonstrated that reentry is the electrophysiologic mechanism underlying many atrial arrhythmias, including AFIB, AFL and most forms of AT. In AFIB multiple reentrant circuits propagate throughout
both the left and right atria [3-4], whereas in AFL a single reentrant circuit is confined to the right atrium [5-6], and in AT reentry circuits may develop around surgical incisions or prosthetic patch materials [7-8]. The delineation of these electrophysiologic mechanisms has been made possible in part by the use of percutaneous, catheter-based, multi-electrode mapping techniques [9-14], and in part by the use of intra-operative multi-electrode mapping techniques [15-16]. However, due to the invasive nature of the techniques required to study arrhythmias in man, animal models have also been created to better understand arrhythmia mechanism(s) and to develop safer and more effective treatments. These animal models, including several anatomical and functional reentry models of AFL and AT [17-25] and the pacing-induced models of AFIB [26-29], have electrophysiologic characteristics that are similar to human atrial arrhythmias, including those that occur following open-heart surgery for acquired or congenital heart disease. This chapter will briefly review the relevant electrophysiologic characteristics of AFIB, AFL and AT, atrial arrhythmias that commonly occur in humans following cardiac surgery, and then describe in detail the experimental arrhythmia models that have been dev
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