The authors describe the case of a 79-year-old man with prior mitral valve repair and a maze procedure who developed recurrent atrial fibrillation, in whom transesophageal echocardiography revealed an accessory lobe of the left atrial appendage in sinus rhythm when the remaining body of the left atrial appendage was in atrial fibrillation or flutter. Electrophysiology confirmed dissociated rhythm within the left atrium. This case emphasizes the need for careful Doppler interrogation of the left atrial appendage and its lobes to look for dissociated atrial rhythm.
Transesophageal echocardiography (TEE) is routinely performed to exclude left atrial appendage thrombus and assess appendage function by pulsed-wave (PW) Doppler prior to electrical or chemical cardioversion or ablation for atrial fibrillation or flutter. We describe a patient who on TEE had an unusual anatomy of the left atrial appendage, with a long accessory lobe that was in sinus rhythm while the other parts of the left and right atria were in atrial flutter on PW Doppler. Intracardiac recordings during electrophysiologic study showed electrical dissociation within the left atrium, confirming dissociated electrical rhythm found on TEE.
Case Presentation
A 79-year-old man with a history of atrial fibrillation and flutter, coronary artery disease status post percutaneous coronary intervention, prior mitral valve and tricuspid valve repair for severe regurgitation, and a surgical maze procedure 8 months previously was admitted for cardioversion for refractory atrial fibrillation. During a prior endocardial maze procedure, radiofrequency ablation lines were created around the left and right pulmonary veins and between the right and left veins down to the mid mitral position. The left ventricular ejection fraction was 45%, and there was mild mitral regurgitation and trace tricuspid regurgitation after the maze procedure. Beta-blocker therapy was continued and amiodarone was started.
Three months later, the patient developed transient complete heart block and underwent dual-chamber pacemaker placement. He was admitted 3 months later for ablation of atrial flutter and fibrillation. TEE showed a severely enlarged left atrium (anteroposterior diameter, 6.6 cm), mitral annuloplasty ring, moderate mitral regurgitation, and marked right atrial enlargement ( Figure 1 ). Evaluation of the left atrial appendage revealed an abnormally elongated lobe of the appendage arising from its body ( Figure 2 , Video 1 ). This was directed anterosuperiorly toward the aortic root and ending close to the origin of left main coronary artery ( Figures 3 A and 3 B, Videos 2 and 3 ). Fast and irregularly timed Doppler waves were seen within the main appendage body ( Figure 4 A), whereas regular slower Doppler velocities were noted on PW Doppler assessment of the cavity of the accessory lobe ( Figure 4 B), as well as tissue Doppler of the wall of the accessory lobe ( Figure 4 C). No thrombus was noted in the body of the appendage or its accessory lobe. Intracardiac electrograms before ablation showed atrial flutter that was twice the cycle length in the portion of the left atrium near the location of left atrial appendage compared with the remaining left atrium or right atrium. After ablation, the patient continued to have atrial flutter with dissociated cycle lengths in the right atrium (290 ms) and left atrium (150 ms). Atrioventricular node ablation was therefore performed.
