Clinicians in first-opinion practice commonly diagnose congestive heart failure (CHF) in small breed dogs with myxomatous mitral valve disease (MMVD) that do not have CHF. To improve the accuracy of CHF diagnosis, we developed an initial algorithm based on historical, physical and radiographic findings that might help a clinician in first opinion practice to more accurately diagnose CHF in these dogs. We then sought to refine and validate the algorithm by determining which of these historical, physical and radiographic findings help discriminate dogs with MMVD into CHF and "not CHF" groups.

We collected the following historical and physical examination information on 52 small-breed dogs presenting for evaluation of a cough, murmur, or suspicion of CHF to the referral clinician: presence or absence of coughing, duration of coughing, recent worsening of cough, presence of loud crackles, murmur intensity, presence of sinus arrhythmia, heart rate, in-clinic respiratory rate, presence or absence of dyspnea, sleeping respiratory rate, response to a diuretic trial (if considered necessary by the referral clinician) and radiographic evaluation of left atrial size. Additionally, all dogs underwent echocardiographic evaluation. The diagnosis of "CHF" or "not CHF" was made by each investigator on their own cases, using all required diagnostic tests and treatment, and not validated by other investigators.

Historical and physical variables that excluded a diagnosis of CHF included presence of a sinus arrhythmia (never identified in CHF dogs), a murmur that was "less than loud", a heart rate <120 bpm, an in-clinic RR <35 breaths/min, less-than-moderate left atrial enlargement on radiographs. A positive diuretic trial which alleviated dyspnea confirmed a diagnosis of CHF. Twenty out of 21 coughing dogs with CHF showed a recently worsening cough.

Based on these findings, we refined our algorithm so that detection of either a sinus arrhythmia, a soft murmur, a sinus rate <100 bpm, or an in-clinic RR<30 breaths per minute excludes a diagnosis of CHF. Presence of a cough or crackles does not help, but a recently worsening cough warrants increases the suspicion of CHF. In cases where CHF is suspected, a resolution of dyspnea with appropriate diuresis strongly supports the diagnosis of CHF. How well the refined algorithm performs with first opinion clinicians remains to be determined.

Disclosures

Disclosures to report.
Dr. Rishniw is currently funded for a study evaluating laryngeal paralysis (ACVIM Foundation Grant) and has provided continuing education talks for general practitioners over the last 4 years, for which he has received honoraria. Dr. Rishniw is a paid employee of Veterinary Information Network.