Effects of Pimobendan for Mitral Valve Regurgitation in Dogs

Abstract

ABSTRACT. Pimobendan has a dual mechanism of action: it increases myocardial contractility by increasing calcium sensitization to troponin C and it promotes vasodilation by inhibiting PDEIII. This study examined the effects of pimobendan on cardiac function, hemodynamics, and neurohormonal factors in dogs with mild mitral regurgitation (MR). The dogs were given 0.25 mg/kg of pimobendan orally every 12 hr for 4 weeks. With pimobendan, the heart rate and stroke volume did not change, but the systolic blood pressure gradually decreased and the degree of mitral valve regurgitation tended to decrease. Renal blood flow was significantly increased and the glomerular filtration rate was slightly increased at 2 and 4 weeks. Furthermore, over the 4-week period, the plasma norepinephrine concentration decreased significantly, the systolic index increased slightly, the left atrial diameter and the left ventricular diameters decreased significantly, and the heart size improved. Given these results, pimobendan appears to be useful for treating MR in dogs. However, further long-term studies of pimobendan involving a larger number of dogs with mild and moderate MR are needed to establish the safety of pimobendan and document improvements in quality of life. KEY WORDS: canine, mitral regurgitation, pimobendan.

Effect of Pimobendan on Echocardiographic Values in Dogs with Asymptomatic Mitral Valve Disease

“…Despite these assumptions and the inodilator properties of PIMO, no significant reduction in the severity of the MR (RV, RF, VTI, and EROA) or significant change in indicators of the severity of the MR (LA/Ao, VHS) were detected in this study. This is contrary to the observations of Kanno et al 6 after introduction of PIMO over a 4‐week period of time in a canine experimental MR model. These investigators actually found a significant reduction of blood pressure, LV diameters, LA : Ao ratio and RV, as well as an increase of FS and EF after introduction of the medication in 4 treated dogs 6 .…”

“…This is contrary to the observations of Kanno et al 6 after introduction of PIMO over a 4‐week period of time in a canine experimental MR model. These investigators actually found a significant reduction of blood pressure, LV diameters, LA : Ao ratio and RV, as well as an increase of FS and EF after introduction of the medication in 4 treated dogs 6 . However, no control group was included in this study, and none of the dogs were treated concomitantly with ACEI and PIMO.…”

“…There is evidence of clinical improvement of the quality of life of these dogs and 2 recent trials also reported a beneficial effect on survival 2–5 . Finally, a recent evaluation in an experimental model of asymptomatic MVD has shown a significant decrease in the MR volume, left atrial and ventricular diameters as well as plasma nor epinephrine concentration after qintroduction of PIMO 6 . However, this experiment was a short‐term study and no histopathologic examination was performed.…”

The Effect of Pimobendan on Left Atrial Pressure in Dogs with Mitral Valve Regurgitation

“…There are reports on echocardiographic values of MR dogs after administration of pimobendan . However, there have been few reports evaluating preload after administration of pimobendan.…”

“…Pimobendan has increased CO in previous reports . Similarly, in the present study, pimobendan increased CO, but did not affect BP, presumably as a result of the combination of pimobendan's positive inotropic and arterial dilatory effects.…”