Case Study

Department: Cardiology

Clinicians: Nancy Laste, DVM, DACVIM (Cardiology), Rebecca Malakoff, DVM, DACVIM (Cardiology), Gregg Rapoport, DVM, DACVIM (Cardiology), Nevena Nikolajevic, DVM (Cardiology Resident)

Patient: A 9-year-old male intact Chihuahua

Presenting concern: The dog was brought to the Angell Animal Medical Center through the Emergency and Critical Care Service due to a new “hacking” cough.  No dyspnea was reported although increased panting had been noted.

Initial physical examination: Oral mucous membranes were slightly pale with a capillary refill time of 2 seconds.  Cardiac auscultation revealed a grade V/VI systolic heart murmur.  The heart rate was 120 beats per minute with a regular rhythm.  Pulmonary auscultation revealed bilateral pulmonary crackles.  There was panting with no apparent dyspnea.

Diagnosis/Treatment: Thoracic radiographs revealed cardiomegaly including a moderate degree of left atrial enlargement.  A mild diffuse bronchointerstitial pulmonary pattern was noted with an additional focal right cranioventral alveolar pattern.  Pulmonary vasculature was normal.  Mainstem bronchial compression was also noted.  Based on these findings, the interpreting radiologist recommended cardiac evaluation.

An electrocardiogram revealed a normal sinus rhythm with no ectopic complexes.  Systolic blood pressure was 140 mmHg.  Complete blood count, serum biochemistry profile, and urinalysis revealed normal renal values, mild hyperkalemia and hyperchloremia, and no other significant findings.

An echocardiogram revealed the following:  thickened mitral and tricuspid valve leaflets, severe left atrial dilation and mild right atrial dilation, mildly dilated left ventricle with normal contractile function, severe mitral regurgitation, and mild tricuspid valvular regurgitation.  The echocardiographic diagnosis was severe mitral and mild tricuspid valvular regurgitation secondary to chronic degenerative valvular disease (CDVD).

Based on the radiographic and echocardiographic findings, the working diagnosis was left-sided congestive heart failure (CHF) secondary to CDVD.  Hospitalization was recommended for initial treatment including injectable furosemide and oxygen supplementation.  Radiographs repeated prior to discharge from the hospital showed resolution of pulmonary edema.  The dog was discharged two days after admission with oral furosemide.

At the first recheck appointment, the dog’s owner reported reduced frequency of coughing and improved energy level.  Thoracic radiographs confirmed that the dog’s cardiac disease remained compensated (no evidence of CHF).  A renal profile revealed normal renal values, borderline hyperkalemia, and no other significant findings.  Oral furosemide was continued and enalapril was added to the ongoing treatment regime.  The recommended follow-up plan at that time included another recheck renal profile one week later (following addition of enalapril), and examination four to six weeks later with a renal profile +/- thoracic radiographs (latter depending on clinical condition).cardiogram

Key factors: Chronic degenerative valvular disease is the most common cause of cardiac symptoms and development of congestive heart failure in dogs.  Initial diagnosis of CHF is sometimes challenging.  While some degree of dyspnea is typically present, clinical signs are occasionally limited to coughing (as in this patient) and/or exercise intolerance.  Syncope, abdominal distension, weakness, lethargy, and other nonspecific clinical signs may also be noted.  Thoracic radiographs are the most important and often the only necessary test in establishing a diagnosis of CHF.  Echocardiography is helpful in corroborating this diagnosis, identifying the specific underlying condition, and providing baseline structural information for future comparison.

The standard of care for initial maintenance therapy for CHF includes furosemide and an angiotensin-converting enzyme inhibitor (enalapril used in this case).  A newer agent, pimobendan (brand name Vetmedin), has received much recent attention for treatment of CHF, although ongoing and future clinical investigation will be necessary to better define its clinical role.  Other medications (e.g. other diuretics, vasodilators, antiarrhythmics, digoxin) are sometimes added depending on specific circumstances.  Prognosis for dogs with CDVD prior to development of CHF is extremely variable, and data regarding survival time or time to CHF are not available for this reason.  Following development of CHF, prognosis remains variable but based on limited information in the veterinary literature, survival time is often estimated at less than one year for dogs with moderate to severe CHF (New York Heart Association classes III and IV).