Echocardiographic evidence of left atrial mechanical dysfunction after conversion of atrial fibrillation to sinus rhythm in 5 horses.
BACKGROUND
Atrial contractile dysfunction occurs in some species after conversion of atrial fibrillation (AF) to normal sinus rhythm (NSR) but has not been reported in horses with naturally occurring AF.


OBJECTIVE
Transthoracic echocardiography allows detection of left atrial (LA) mechanical dysfunction in horses after conversion of AF to NSR.


METHODS
Five Standardbreds with AF and 6 healthy Standardbreds of similar age, weight, and athletic condition were included in this study.


METHODS
Four horses were treated pharmacologically (quinidine), and 1 horse was treated by means of transvenous electrical cardioversion. Echocardiographic examinations were performed in normal horses (once) and in AF horses (24 hours and 72 hours after conversion to NSR) by means of 2-dimensional echocardiography (2DE), transmitral flow Doppler, and tissue Doppler imaging (TDI) techniques. Echocardiographic indices of LA mechanical function were compared between normal horses and AF horses.


RESULTS
Two-dimensional echocardiography and TDI indices of LA mechanical function revealed significant decreases in LA contractile function and LA reservoir function 24 hours after cardioversion. This decrease was no longer statistically significant 72 hours after cardioversion, but changes in echocardiographic variables between 24 and 72 hours varied among horses.


CONCLUSIONS
LA contractile dysfunction can be evaluated in horses by use of 2DE, transmitral Doppler flow velocity profiles, and analyses of LA wall motion by TDI. The results of this study are consistent with AF-induced atrial remodeling, although residual treatment effects or influence of underlying primary myopathy cannot be excluded.
Schwarzwald
Colin C
CC
Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, OH 43210, USA. cschwarzwald@vetclinics.umizh.ch
Schober
Karsten E
KE
Bonagura
John D
JD
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000188:drug therapy*; D016279:Atrial Function, Left / Q000187:drug effects* / Q000502:physiology*; D004452:Echocardiography / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D008297:Male; D011802:Quinidine / Q000627:therapeutic use
D000889:Anti-Arrhythmia Agents; D011802:Quinidine