Restoration of sinus rhythm after mitral valve plasty with concomitant left atrial appendage excision in four small-breed dogs with myxomatous mitral valve disease and atrial fibrillation: a case series

Four dogs with mitral regurgitation (MR) secondary to myxomatous mitral valve disease (MMVD) were referred for mitral valve plasty (MVP). Electrocardiography revealed the absence of P waves and irregular RR intervals in all dogs, confirming atrial fibrillation (AF). Echocardiography showed mitral valve prolapse with regurgitation and enlargement of the left atrium (LA) and left ventricle. All dogs underwent MVP under cardiopulmonary bypass (CPB) with chordal reconstruction and annuloplasty, combined with left atrial appendage (LAA) excision as an adjunctive procedure to address potential LAA blood stasis, thrombus formation, and arrhythmogenic substrate. Postoperatively, episodes of AF or other supraventricular tachyarrhythmias occurred in all dogs; however, sinus rhythm (SR) was restored in all dogs and was documented on follow-up surface electrocardiograms (ECGs) more than 1 year after surgery, although AF later recurred in one dog. LA size decreased after surgery, although LA enlargement persisted at 3 months. These cases illustrate the postoperative rhythm changes following MVP with concomitant LAA excision and highlight the importance of longitudinal rhythm assessment. Larger comparative studies with systematic rhythm monitoring are needed to evaluate postoperative rhythm outcomes and the contributions of the individual procedures. Moreover, because all four dogs weighed less than 10 kg, these findings cannot be generalized to medium- and large-sized dogs.