6.4.1 Clinical signs
The clinical signs associated with a ruptured chorda tendinea depend on whether the MV or TV is affected, and the contribution of the affected chorda to support of the valve. The larger the chorda involved, the more severe the clinical signs are likely to be. The rupture may or may not occur at a time of strenuous exercise.
Rupture of a major chorda to the MV usually results in signs of acute left-sided CHF. Because the pressure within the LA increases rapidly, the atrium and pulmonary veins do not have an opportunity to adapt to the increased pressure and the pulmonary venous pressure increases sufficiently to cause pulmonary oedema. This may result in a rapid deterioration with tachypnoea and coughing. Exercise intolerance, weakness and even syncope may occur during this period. Often this initial crisis is followed by a period during which signs of pure left-sided CHF decrease in severity.
In the long-term, pulmonary hypertension, right-sided pressure overload, TR and signs of right-sided CHF such as distended jugular veins> and dependant oedema develop. In some horses, clinical signs may not be observed immediately and these animals may be presented only later as a result of poor exercise tolerance, or right-sided CHF. Arrhythmias such as atrial fibrillation may result from distension of the atria. Rupture of the MV chordae tendineae may result in sudden death in some animals, although this is uncommon. However, a murmur of AV regurgitation due to ruptured chordae tendineae may be an incidental finding in animals which do not perform strenuous work.