Atrial fibrillation is a cardiac arrhythmia observed in horses characterized by irregular and often rapid heart rhythms. This condition arises from disorganized electrical signals in the atria, leading to ineffective atrial contractions. Atrial fibrillation can affect a horse's performance and may be detected through clinical signs such as exercise intolerance, irregular heartbeat, and sometimes respiratory distress. Diagnosis typically involves electrocardiography to identify the irregular electrical activity. Management and treatment strategies vary based on the underlying cause and the horse's intended use. This page compiles peer-reviewed research studies and scholarly articles that explore the pathophysiology, diagnosis, and management of atrial fibrillation in equine patients.
Meijler FL, Kroneman J, van der Tweel I, Herbschleb JN, Heethaar RM, Borst C.RR interval sequences during spontaneous atrial fibrillation in eight horses were analyzed as in previous studies in patients and dogs using histograms and serial auto-correlograms. In patients and dogs with spontaneous atrial fibrillation, ventricular rhythms were always random. In the horses, the histograms were skewed with median RR intervals of approximately 1,000 ms. A striking finding in these animals was the presence of long RR intervals up to 5,000 ms in duration. The shortest RR intervals lasted 400 to 600 ms. In contrast to findings in dogs and patients, the serial autocorrelograms s...
Muir WW, McGuirk SM.Hemodynamic measurements were obtained from 17 horses with atrial fibrillation or flutter. Eight horses had atrial fibrillation of unknown duration. In 7 horses, atrial fibrillation developed during anesthesia. Atrial flutter developed during recovery from anesthesia in 2 horses. Hemodynamic measurements were considered normal in 7 of 8 conscious horses with atrial fibrillation. Cardiac output was decreased and pulmonary arterial blood pressure and right atrial pressure were increased in 1 conscious horse which had signs of congestive heart failure. Arterial blood pressure decreased in 5 of 7 ...
Morris DD, Fregin GF.Seventy-seven horses with atrial fibrillation (AF) were treated orally with quinidine sulfate (QS) at the University of Pennsylvania, School of Veterinary Medicine, Thirty-seven horses (48%) had adverse reactions to QS, the most common of which were nasal mucosal edema, anorexia, colic, and diarrhea. The mean highest daily QS dose was slightly greater in horses showing toxicity (P less than 0.1) and their conversion rate was less (P less than 0.05). A schedule of gradually increasing QS dose was time consuming, costly and not associated with fewer adverse reactions. Horses were compared by the...
Wingfield WE, Miller CW, Voss JL, Bennett DG, Breukels J.Echocardiography is a non-invasive, safe means of assessing intracardiac structures and their motion. In the normal motion of the mitral valve there is anterior motion noted during atrial systole. In 3 horses with atrial fibrillation the mitral valve motion had no anterior motion to correspond with atrial contractions. Quinidine returned the electrocardiogram of one horse to a sinus rhythm after which echocardiography demonstrated the reappearance of the anterior motion of the mitral valve.
Wingfield WE, Miller CW, Voss JL, Bennett DG, Breukels J.Echocardiography is a non-invasive, safe means of assessing intracardiac structures and their motion. In the normal motion of the mitral valve there is anterior motion noted during atrial systole. In 3 horses with atrial fibrillation the mitral valve motion had no anterior motion to correspond with atrial contractions. Quinidine returned the electrocardiogram of one horse to a sinus rhythm after which echocardiography demonstrated the reappearance of the anterior motion of the mitral valve.
Schwarzwald CC, Bonagura JD, Luis-Fuentes V.Quinidine is effective for treatment of atrial fibrillation (AF) in horses, but often accelerates ventricular response rate. Diltiazem effectively controls heart rate response to AF in other species. This investigation determined the effects of diltiazem on cardiac rate and rhythm, left ventricular (LV) function, central hemodynamics, and peripheral blood flow in normal, standing, nonsedated horses. A dose-finding study was performed. Afterward, 8 healthy horses were treated with diltiazem IV every 30 minutes to achieve cumulative dosages of 0 (saline control), 1, 1.5, and 2 mg/kg. Plasma dilt...
Peters ST, Hopkins A, Stewart S, Slack J, de Solis CN.To describe the clinical findings and management of myocardial injury secondary to blunt thoracic trauma and rib fracture in an adult horse. Methods: A 6-year-old Warmblood gelding presented for treatment of blunt thoracic trauma. Sonographic examination of the thorax revealed a complete, mildly comminuted fracture of the left 5th rib with a fragment overlying the left atrium and coronary artery, hemothorax, and subjective left ventricular dyskinesis. Evidence of myocardial injury included atrial fibrillation, ventricular ectopy, and increased plasma cardiac troponin I concentration. The rib f...
Ferlini Agne G, Kapusniak AE, Wooldridge AA, Jung SW.In this case report, a high dose of torsemide (6mg/kg, every 12 hours for 3 days followed by 12mg/kg, every 12 hours for 4 days) was administered orally to a horse with congestive heart failure (CHF) and atrial fibrillation. Blood samples for measurement of plasma torsemide concentrations were obtained one hour after each drug administration. Pharmacodynamic effects of oral torsemide were evaluated by daily physical examination, electrocardiography, and serum biochemistry. The horse tolerated administration of torsemide. A decrease in ventral oedema and venous congestion was subjectively noted...
Vernemmen I, Van Steenkiste G, Decloedt A, Meert H, Walser U, van Loon G.Implantable loop recorders (ILRs) are increasingly used in equine cardiology to detect arrhythmias in the context of collapse, poor performance or monitoring for recurrence of atrial fibrillation (AF). However to date, the ILR has never been reported to be used with a remote monitoring functionality in horses, therefore the arrhythmia is only discovered when a clinician interrogates the ILR using dedicated equipment, which might delay diagnosis and intervention. This case report describes the use of an ILR with remote monitoring functionality in a horse with recurrent AF. The remote monitoring...
