Pimobendan timing and dosing for a Cavalier in Stage B2 M...

Excellent question, and you've correctly identified the key threshold for intervention. An LA:Ao of 1.8 in a Cavalier with MMVD places this patient squarely in ACVIM Stage B2, and the evidence for starting pimobendan at this stage is robust.

The landmark EPIC trial demonstrated that initiating pimobendan in Stage B2 patients (defined by echocardiographic and radiographic cardiomegaly) prolonged the asymptomatic period by an average of 15 months. You are moving from monitoring to active management to delay the onset of congestive heart failure.

Recommendation:

Initiate Pimobendan: Start at the standard dose.

* Dose: 0.25-0.3 mg/kg PO every 12 hours.
* Timing: This is critical. Pimobendan must be given on an empty stomach (at least one hour before feeding), as food significantly decreases its bioavailability. This is a crucial point to emphasize to the owner.

Establish a Baseline Sleeping Respiratory Rate (SRR): This is the most important monitoring tool for the owner. Have them start tracking the SRR at home now, while the dog is asymptomatic. This gives you a reliable baseline. A sustained rate >30 breaths/minute is the earliest indicator of impending CHF.

Recheck Schedule: I would recommend a recheck, including blood pressure and echocardiogram, in 6 months to assess the rate of progression, or sooner if any clinical signs (cough, exercise intolerance, increased SRR) develop.

You are doing exactly the right thing by intervening at this stage. It's a key opportunity to significantly extend this dog's quality, asymptomatic life. No diuretics are indicated at this time, as there is no evidence of congestion.