Table 2.

Prognostic guidelines for performance of horses affected with mitral and aortic regurgitation.^a

	Excellent	Fair	Guarded to Poor
Mitral regurgitation
Arterial pulses	Normal	Normal	Weak
Valve lesion	None, mild MVP	Mild thickening, mild dysplasia	Severe thickening, RCT, flail leaflet, endocarditis, severe dysplasia
LA enlargement	Absent or mild	Mild to moderate	Moderate to severe or progressive
LA shape	Normal	Normal or slightly rounded	Might appear round and turgid
Interatrial septum	Normal	Normal	Might be bulging toward RA
LV volume overload	Absent	Mild	Moderate to severe
LV systolic function	Normal	Normal	Hyperdynamic, normal (less than expected) or decreased
Pulmonary vein enlargement	Absent	Absent	Usually present
PA enlargement	Absent	Absent	Present or developing
MR jetb	One or multiple small & narrow jets	One or more medium‐sized jets	Large single or large multiple jets
AF, PACs	Absent	Pre‐existing	Secondary
Aortic regurgitation
Arterial pulses	Normal	Normal or slightly bounding	Bounding or weak
Arterial blood pressure	Normal		Pulse pressure >60 mmHg
Valve lesion	None, parallel fibrous band, mild AVP	Nodular thickening, moderate AVP suspected fenestration	Severe thickening or AVP, flail leaflet, endocarditis, congenital malformation
Aortic root	Normal	Normal or mild enlargement	Mild to severe enlargement
LV volume overload	Absent or mild	Mild to moderate	Moderate to severe
LV systolic function	Normal	Hyperdynamic	Hyperdynamic or decreased
AR jetb	One or 2 small & narrow jets Long pressure half‐timec	One or more medium‐sized jets	Large single or large multiple jets Short pressure half‐timec
LA enlargement	Absent	Absent or mild	Mild to severe
Concurrent MR	Absent	Absent or pre‐existing	Secondary to AR
PA enlargement	Absent	Absent	Present
Ventricular arrhythmias	Absent	Absent	PVCs, VT
AF	Absent	Pre‐existing	Secondary
Age at onset	Older	Middle age	Young

^aCombined assessments are essential in accurately formulating a prognosis for life and performance and should include lesions detected, size of cardiac chambers, myocardial function, color Doppler assessment of jet, Doppler (CW)/hemodynamic estimates, age at onset, and intended use of horse.

^b“Jet” includes both the width of the regurgitant flow at the valve orifice (at the vena contracta) and the jet area relative to the receiving chamber area, in which case the “jet” likely includes entrained RBCs. Width of the jet at the valve orifice is difficult to measure accurately because of dynamic, nonuniform, three‐dimensional structure at the vena contracta. Jet area is highly dependent on technical factors including ultrasound beam angle, transducer distance from the region of interest, transducer frequency, 2D and color gain and filter settings, pulse‐repetition frequency, and image plane.

^cPressure half‐time cannot be accurately measured unless the interrogating beam is maintained at a constant angle with the regurgitant jet.

AF, atrial fibrillation; AR, aortic regurgitation; AVP, aortic valve prolapse; LA, left atrial; LV, left ventricular; MR, mitral regurgitation; MVP, mitral valve prolapse; PA, pulmonary artery; PAC, premature atrial complex; PVC; premature ventricular complex; RA, right atrium; RCT, ruptured chordae tendineae; VT, ventricular tachycardia.