Atrial Fibrillation Cardioversion ================================= þ Anticoagulation After Cardioversion: If the patient is cardioverted there is one little problem with this: the LA remains thrombogenic after cardioversion for a variable period of time due to atrial stunning. Embolism may occur days or weeks after sinus rhythm is restored and thus the rationale for 4 weeks of anticoagulation after conversion. The presence of atrial EMD after restoration of sinus rhythum has been well documented by TEE (1). To what extent this is a problem after pharmacologic conversion is not clear to me but appears to be less of a concern. The use of TEE to select out those at reduced risk for embolism by anticoagulating only those with documented LA thrombus has been proposed (3). The occurence of atrial stunning renders this something less than a foolproof method of avoiding embolism, however (2,4). Other than increased risks of embolism when conversion is delayed beyond 48 hours there is one other compelling reason to perform it in as timely a fashion as possible. That is, the single strongst predictor of sucessful conversion (pharmacologic or electrical) is the duration of a fib. H. Louzon MD (1) Conti CR Atrial fibrillation, transesophageal echo, electrical cardioversion, and anticoagulation [editorial] [see comments] Clin Cardiol 1994 Dec;17(12):639-40 Although successful electrical cardioversion is accomplished in most cases without any evidence of embolic stroke, a few patients have experienced this catastrophe. The current thinking is that when electrical energy is applied to the chest wall, the atrium, although it returns to sinus rhythm, is stunned. It is not known how long this stunning lasts in the individual patient nor whether high energy produces stunning and low energy does not. Nor is it known whether chemical conversion of atrial fibrillation to sinus rhythm affects the atrium in the same way. However, the atrium seems to recover more quickly in patients with a short duration of atrial fibrillation and these patients may not require the usual four weeks of postcardioversion anticoagulation. Based on what we know, or more precisely what we don't know, it seems reasonable to ensure that every patient with atrial fibrillation is anticoagulated during and after DC cardioversion to sinus rhythm. Of course, this is easy to do with intravenous heparin, but that requires hospitalization. Perhaps subcutaneous heparin in high doses would suffice until the patient can be anticoagulated with coumadin. From the research perspective it might be interesting to perform serial echo/Doppler studies on these patients to identify when the individual patient's atrial function returns to normal. This might provide a clinical rationale for discontinuing anticoagulation. Comparing the time to return of normal atrial function (as measured by Doppler echo) between patients undergoing pharmacologic cardioversion versus electrical cardioversion and studying the relationship of the amount of electrical energy required for cardioversion versus the duration of stunning would be clinical research projects of interest to clinicians. (2) Fatkin D, Kuchar DL, Thorburn CW, Feneley MP Transesophageal echocardiography before and during direct current cardioversion of atrial fibrillation: evidence for "atrial stunning" as a mechanism of thromboembolic complications. J Am Coll Cardiol 1994 Feb;23(2):307-16 OBJECTIVES. The purpose of this study was to evaluate the usefulness of transesophageal echocardiography before electrical cardioversion in patients with atrial fibrillation and to determine the mechanism of thromboembolism after cardioversion. BACKGROUND. Thromboembolic complications after electrical cardioversion of atrial fibrillation have been attributed to the dislodgment of preexistent left atrial thrombus during the resumption of atrial contraction. Transesophageal echocardiography has been proposed as a method of screening patients for left atrial thrombus before cardioversion. METHODS. Seventy transesophageal echocardiographic studies were performed in 66 patients, predominantly with nonvalvular atrial fibrillation, before direct current cardioversion. In addition, transesophageal echocardiography was performed during the cardioversion procedure in 15 patients and immediately after in 1 patient. RESULTS. Left atrial thrombus was detected in one patient (1.4%), and cardioversion was cancelled. Thromboembolic complications occurred in 4 patients, none of whom had evidence of left atrial thrombus before cardioversion. Within 10 s of successful cardioversion, left atrial spontaneous echo contrast appeared in five patients, increased in one patient and was unchanged in nine patients. Patients with new or increased spontaneous echo contrast had more impaired atrial contraction and slower initial heart rates after cardioversion than those without. Left ventricular contraction was also impaired transiently by cardioversion. CONCLUSIONS. Transesophageal echocardiographic detection of left atrial thrombus before direct current cardioversion is important but infrequent in patients with predominantly nonvalvular atrial fibrillation. The occurrence of thromboembolic complications in the absence of demonstrable left atrial thrombus and the new development of spontaneous echo contrast in association with the transient atrial dysfunction ("stunning") caused by cardioversion suggest that cardioversion may promote new thrombus formation, in which case all patients should receive full anticoagulant therapy at the time of cardioversion. (3) Leung DY, Grimm RA, Klein AL Transesophageal echocardiography-guided approach to cardioversion of atrial fibrillation. Prog Cardiovasc Dis 1996 Jul-Aug;39(1):21-32 In patients with atrial fibrillation, electrical cardioversion is often performed to relieve symptoms, to improve left ventricular function, and to decrease thromboembolic risks. However, cardioversion of atrial tachyarrhythmias is associated with an increased embolic risk, with an event rate of up to 5.6%. The American College of Chest Physicians recommend 3 weeks of systemic anticoagulation before elective cardioversion and 4 weeks of systemic anticoagulation afterwards. Expulsion of preexisting left atrial (LA) thrombi with resumption of sinus rhythm has traditionally been considered the mechanism for this increased embolic risk associated with cardioversion. The advent of transesophageal echocardiography (TEE) has allowed accurate detection of LA thrombus. Moreover, recent studies using TEE have identified a state of atrial "stunning" immediately after cardioversion, which is considered a thrombogenic milieu in which new thrombus formation and increased or de novo appearance of LA spontaneous echocardiographic contrast have been observed. Furthermore, embolic events have been reported after cardioversion despite exclusion of preexisting LA thrombus by TEE. These studies strongly suggest an alternative mechanism for embolism after cardioversion, ie, atrial stunning with worsened atrial appendage function and enhanced thrombogenesis. Recent studies have shown the safety of a TEE-guided anticoagulation approach in which exclusion of preexisting LA thrombus by TEE enables early cardioversion without the need for the standard 3 weeks of systemic anticoagulation. The importance of maintaining therapeutic anticoagulation has been further emphasized. Although preliminary observational studies of TEE-guided cardioversion are encouraging, there has been no prospective, randomized trial comparing the two strategies of anticoagulation management. The Assessement of Cardioversion Utilizing Transesophageal Echocardiography (ACUTE) pilot study randomized 126 patients from 10 sites and showed the feasibility and safety of the larger scale study. A larger multicenter, prospective randomized trial is now underway and is expected to randomize a total of 3,000 patients. The results of the ACUTE study will definitively establish the safest and the most cost-effective way to manage anticoagulation for elective cardioversion. (4) Missault L, Jordaens L, Gheeraert P, Adang L, Clement D Embolic stroke after unanticoagulated cardioversion despite prior exclusion of atrial thrombi by transoesophageal echocardiography. Eur Heart J 1994 Sep;15(9):1279-80 Recent studies in patients with atrial fibrillation, not on anticoagulation, suggest that if transoesophageal echocardiography (TEE) excludes the presence of thrombi, early cardioversion can be performed safely without the need for anticoagulation before the procedure. Immediately after successful cardioversion, however, left atrium or left atrial appendage stunning may be present, potentially carrying a risk for de novo thrombus formation. Furthermore, the presence of spontaneous contrast is considered as a contraindication for unanticoagulated cardioversion since it has been associated with postcardioversion thromboembolism. We present a case in which stroke developed in relation to unanticoagulated cardioversion regardless of careful prior evaluation with TEE.