Severe mitral regurgitation in horses: clinical, echocardiographic and pathological findings.

The research paper has studied 43 horses with mitral regurgitation and congestive heart failure, revealing significant alterations in heart size and rate, increases in pulmonary artery diameter, and various symptomatic presentations. Pathological and echocardiographic findings were corroborated, with pulmonary artery dilatation identified as a critical warning sign.

Research Background and Methodology

• This research was conducted on 43 horses diagnosed with mitral regurgitation (MR) and congestive heart failure. The techniques used for the examination included M-mode, two-dimensional real-time, and Doppler echocardiography.
• The researchers investigated various potential predisposing factors, including breed or sex, but found no significant correlation when compared to the general hospital population.

Findings and Observations

• The study found significant increases in the mean values for left ventricular chamber size, left atrial size, and heart rate in the horses with MR and congestive heart failure. This result was coupled with significant decreases in the interventricular septal and left ventricular free wall thickness.
• Within the same group, there was a notable increase in pulmonary artery diameter, compared to the aortic diameter.
• All the researched horses had a particular kind of murmur, known as the Grade 3-6/6 holosystolic or pansystolic, centered around the mitral to aortic valve area.
• Atrial fibrillation was detected in 24 horses, and various other abnormalities, such as ventricular premature contractions, were noted in other cases.

Signs, Symptoms, and Prognosis

• Common signs of MR and congestive heart failure in horses included exercise intolerance, respiratory symptoms, and fever.
• Using echocardiography, abnormal conditions like the thickening of the left atrioventricular valve leaflets, flail valve leaflets, rupture of a chorda tendineae, and mitral valve prolapse were identified.
• A significant feature noted was the pulmonary artery dilatation – an indication of severe pulmonary hypertension. This was found to be a serious prognostic indicator, possibly pointing towards an impending pulmonary artery rupture.
• All horses did not survive due to the severity of their MR and/or nonresponsiveness to therapy.

Post Mortem Findings

• Post mortem examinations were performed on 35 horses confirming pathological changes seen on the echocardiography.
• There was a significant association between the echocardiographic detection of a dilated pulmonary artery and its presence at post mortem examination, corroborating the suggestion that it’s a critical warning sign.

Implications of the Study

• The study highlights the need for using M-mode, 2-dimensional real-time, and Doppler echocardiography to accurately characterize the valvular abnormalities and assess the severity of mitral regurgitation in horses.
• It also emphasizes the value of recognizing pulmonary artery dilatation as a grave prognostic indicator, which could help in early diagnosis and prompt treatment.