Background: The effects of furosemide on left atrial pressure (LAP) in dogs with mitral regurgitation (MR) have not been documented in a quantitative manner and between different routes of administration.

Objective: To document LAP and echocardiographic parameters in MR dogs administered furosemide IV or PO, in order to document changes in LAP after furosemide treatment.

Animals: Five healthy Beagle dogs (3 males and 2 females; aged 2 years) were used.

Methods: Experimental, cross-over, and interventional study. LAP was measured before the administration of furosemide, and 30 minutes, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, and 24 hours after administration. Furosemide 1, 2, or 4 mg/kg IV, PO or placebo was administered.

Results: LAP was significantly decreased with all administrations of furosemide but not after placebo (P < .05, respectively). The max reduction was observed 1 hour (1 mg/kg IV, 15.04 ± 7.02 mmHg), 3 hours (2, 4 mg/kg IV, 13.28 ± 8.01, 9.23 ± 4.92 mmHg), 4 hours (1 mg/kg PO, 14.68 ± 11.51 mmHg), and 5 hours (2, 4 mg/kg PO, 13.19 ± 10.52, 10.70 ± 7.69 mmHg). E wave and E/Ea were significantly decreased corresponding to the reduction of LAP after administration of 2 and 4 mg/kg (P < .05, respectively).

Conclusions and Clinical Importance: LAP was decreased in proportion to the dosage of furosemide, which did not significantly differ between IV and PO of the same dosages. E wave and E/Ea might be useful for the treatment evaluation of furosemide.

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