Introduction

• Prevalence: rare.
• Spectrum of abnormalities: excessively long or short chordae tendinae; abnormal numbers + displacement of papillary muscles; abnormal location of valve annulus; thickened and/or distorted valve cusps. Occasionally mitral valve stenosis, especially Bull Terrier.
• Signs: valves usually incompetent - one or both may be affected → congestive heart failure - mitral regurgitation may lead to left-sided CHF; tricuspid regurgitation may lead to right-sided CHF.
• Diagnosis: echocardiography.
• Treatment: symptomatic.
• Prognosis: poor if CHF at young age.

Pathogenesis

Etiology

• Probably hereditary.

Predisposing factors

General

• Breed.

Pathophysiology

Mitral valve

• Malformation → valvular incompetence.
• Rarely, stenotic → greatly increased left atrial pressure.

Mitral dysplasia

• Mitral regurgitation → left atrial and left ventricular volume overload → left atrial and left ventricular dilation → increased left atrial pressures → pulmonary venous congestion → pulmonary edema (left-sided CHF).
• If left atrial enlargement is severe enough, arrhythmias such as atrial fibrillation Heart: atrial fibrillation may occur.
• If severe enough, mitral regurgitation can lead to decreased cardiac output, resulting in weakness or syncope.
• Severe increases in pulmonary venous pressure may result in pulmonary vasoconstriction → pulmonary hypertension Pulmonary Arterial Hypertension (PHT) and right sided failure secondary to increased afterload on right side of heart.

Tricuspid valve

• Malformation → valvular incompetence of the valve.
• Ebstein's anomaly → displacement of the AV leaflets and annulus towards the apex of the heart.

Tricuspid dysplasia 

• Tricuspid regurgitation → right atrial and right ventricular overload → right atrial and ventricular dilation → increased right atrial pressure → increased central venous pressure Tricuspid valve dysplasia:
  • → pleural effusion
  • → jugular distension and chronic venous congestion of liver → ascites → right-sided CHF.
• If tricuspid regurgitation is severe enough, it can lead to a decrease in chronic output and result in weakness or syncope.
• Superventricular tachycardias (including atrial fibrillation Heart: atrial fibrillation ) may be seen.

Timecourse

• Murmur from birth.
• Prognosis depends upon severity of the lesion.
• Patients with AV dysplasia may live years prior to the development of CHF.

Diagnosis

Treatment

Prevention

Outcomes