The effect of pimobendan on left atrial pressure in dogs with mitral valve regurgitation.

BACKGROUND The effects of pimobendan on left atrial pressure (LAP) in dogs with mitral valve disease (MR) have not been documented in a quantitative manner. OBJECTIVE The objective was to document and study the short-term effects of pimobendan on LAP and echocardiographic parameters in MR dogs. ANIMALS Eight healthy Beagle dogs weighing 10.0-14.7 kg (3 males and 5 females; aged 2 years) were used. METHODS Experimental, cross-over, and interventional study. Dogs with surgically induced MR received pimobendan at either 0.25 mg/kg or 0.50 mg/kg p.o. q12h for 7 days and then, after a 7-day wash-out period, the other dosage. LAP was measured for 30 minutes at baseline and again on days 1, 2, 4, and 7 of pimobendan administration. RESULTS Mean LAP was significantly decreased after the administration of 0.25 mg/kg (15.81 ± 5.44 mmHg to 12.67 ± 5.71 mmHg, P < .001) and 0.50 mg/kg (15.76 ± 5.45 mmHg to 10.77 ± 5.23 mmHg, P < .001). Also, the 0.50 mg/kg group led to a significantly lower LAP (P < .01) compared with the 0.25 mg/kg group. Significant reduction was seen for the first time 4 days after the administration of 0.25 mg/kg and a day after the administration of 0.50 mg/kg. CONCLUSIONS AND CLINICAL IMPORTANCE Pimobendan decreased LAP in a dose-dependent manner in dogs with acute MR caused by experimental chordal rupture. This study did not evaluate adverse effects of high-dose pimobendan, and additional studies in clinical patients are warranted.