Cardiology Resident University of Florida Small Animal Hospital Gainesville, Florida, United States
Abstract: Background – The relative importance of vascular responses to pimobendan in dogs with congestive heart failure (CHF) are incompletely studied.
Hypothesis/Objectives – We hypothesized that if pimobendan reduces systemic vascular resistance, femoral arterial flow (estimated by Doppler velocity-time integral) will increase and arterial resistive index will decrease after a single dose of pimobendan in dogs with CHF.
Animals – Ten client-owned dogs with myxomatous mitral valve degeneration undergoing treatment for acute onset of CHF were studied.
Methods – Prospective, within-subjects study design. Duplex Doppler ultrasonography (DDU) was used to quantify femoral arterial volumetric flow and calculate resistive index at baseline and two hours after a single oral dose of pimobendan (0.3 mg/kg). DDU recordings were measured offline by an operator blinded to treatment. Measurements pre-and post-pimobendan administration were compared using paired t-tests or Wilcoxon’s signed-rank test.
Results – Mean dose (±SD) of furosemide at enrollment was 2.616 mg/kg (±1.56). Total VTI estimating flow over the cardiac cycle was unchanged from baseline to treatment (3.24 cm ±1.82 vs. 3.24 cm ±1.50). Resistive index at baseline (1.21 ±0.16) was not different from pimobendan (1.30 ±0.07, p=0.105), although peak systolic velocity was 0.22 cm/s higher (p=0.026) and minimal velocity 0.12 cm/s lower (p=0.011) after pimobendan. Mean systolic blood pressure measurements were 126.5 mmHg ±20.13 and 131.0 mmHg ±19.97) pre- vs. post-pimobendan (p=0.568).
Conclusion – A single dose of pimobendan following administration of furosemide did not produce measurable vasodilation or increased peripheral blood flow based on DDU in dogs with acute congestive heart failure.
