Long term prognosis of moderate or severe left-sided cardiac valvular regurgitations in horses

Mitral and aortic regurgitations (MR and AR) are common in horses. Unlike mild valvular regurgitations, long-term prognosis of moderate or severe MR and AR is suspected to be guarded since they might induce congestive heart failure (CHF). The aim of this study is to perform a long-term follow-up of horses with moderate or severe MR and/or AR to confirm this prognosis.
Firstly medical files of horses with moderate or severe MR and/or AR that had a follow-up, were retrospectively reviewed over a 15-years period (2000-2015). Clinical and echocardiographic data of 25 horses with moderate or severe MR (16/25) or AR (8/25) or both (1/25) were considered. All horses had undergone 2 or more echocardiographic exams 6 months to 10 years apart. Eight horses developed CHF (4 MR and 4 AR) and all died/were euthanized. Diastolic left ventricular internal diameter, left atrial diameter and pulmonary artery diameter were/became above reference values in 17/25 horses but no significant difference was observed between the first and the follow-up measurements (Student's t-test, p<0.05).
Secondly follow-up data of additional horses with moderate or severe MR was collected by telephone survey. Owners of 27 horses agreed to answer the survey 1 to 6 years after diagnosis. Ten horses with CHF had died, 3/27 had developed CHF, 10/27 had remained clinically stable and 4/27 had died of non-cardiac causes.
Results of this study confirm that moderate or severe MR and AR carry a guarded to poor long-term prognosis as 40% (21/52) of the studied horses developed CHF.