HISTORY

A 1-year old Cairn Terrier male dog was referred for a cardiovascular exploration because of systolo-diastolic heart murmur detected six months ago. Physical examination showed a good body condition. The mucous membranes were normal. No cough nor dyspnoea was reported. Heart rate was 120 bpm without arrhythmia. A left apical grade II/VI systolic and diastolic heart murmur was detected. Thoracic radiographs revealed a left atrial dilation with venous congestion but no pulmonary oedema. A prolonged tall notched P wave was detected in lead II of the electrocardiogram. Two-dimensional echocardiography confirmed the enlarged left atrium (twice the normal size), and showed thickened mitral leaflets, with diastolic doming and with reduced opening on parasternal long axis views. Left chordae were also markedly thickened. M-mode echocardiography showed an increased E-F slope. Spectral Doppler of mitral inflow confirmed a high diastolic velocity flow profile (2,5 m/s) and a prolonged pressure half time (187 ms). Color-flow Doppler revealed a narrow aliased signal during diastole starting just at the level of the mitral valve orifice, associated with a mild mitral regurgitation.

The animal was first treated with benazepril, then an open heart surgery (mitral commissurotomy) was performed with extracorporeal blood circulation. After surgery, the animal was in very good condition. The diastolic heart murmur disappeared. Left atrium diameter was normal. Finally, spectral Doppler showed a significant decrease of the diastolic mitral flow velocity (1,49 ms) and of the pressure half time (105 ms).

DISCUSSION

Mitral valve stenosis (MVS) is defined as a narrowed mitral valve orifice. MVS is usually a congenital abnormality, rarely encountered in dogs and cats. As in this case, MVS may occur as a single entity, or may be associated with other defects such as a subaortic or pulmonary stenosis, patent ductus arteriosus or ventricular septal defect. Congenital MVS includes a variety of left atrioventricular valve abnormalities, i.e., abnormal thickened leaflets, hypertrophy of papillary muscles or chordae tendinae, the presence of a supravalvular ring and hypoplastic valves. As in this case, restriction of left ventricular filling results in an increased left atrial pressure leading to a left atrial dilation, and then left-sided heart failure. A low-grade diastolic heart murmur may be heard in the left apical area, but most often, especially in patients with a fast heart rate, no heart murmur is detected. As in this case, a systolic heart murmur may also be detected, when mitral regurgitation occurs concomitantly with MVS. As in this dog, the ante mortem diagnosis of MVS may be easily done using two-dimensional and M-mode echocardiography combined with spectral and colour-flow Doppler. Treatment of dogs and cats with MVS and moderate left-sided heart failure is generally medical, but in our case, open heart surgery ( mitral commissurotomy) was performed. To our knowledge, this is the only case reported in which we can see an improvement in spectral Doppler parameters and clinical signs shortly after surgery.