Chronic Degenerative Valve Disease

Michael Luethy, DVM, DACVIM (Cardiology)

September 23, 2013

Chronic degenerative valve disease (CDVD), also known as myxomatous degeneration of the mitral valve, endocardiosis, and warty valve disease; is the most common cause of CHF in the canine population. While well recognized as a severe problem of small breed dogs such as the Cavalier King Charles spaniel, Maltese, and Chi hua hua, the disease commonly affects large breeds such as the German shepherd, Airedale terrier, Doberman pinscher, and Dalmatian with > 1/3 of the canine population affected after 10 years of age.

The onset of the disease is typically heralded by the presence of a classic “plateau character” systolic murmur that is typically most prominent over the left side of the cardiac apex. The Cavalier King Charles spaniel will frequently develop a systolic click over the mitral valve region prior to the onset of heart murmur. Frequently noted clinical signs include decreased energy and stamina, syncope, coughing, tachypnea, and dyspnea.

Small breed dogs that are classically affected by CDVD are also the breeds most commonly affected by chronic bronchitis and tracheal collapse. Differentiating the cough and respiratory signs associated with CDVD from those associated with primary airway disease can be difficult. Additionally, the cardiomegaly associated with CDVD may lead to airway compression and prominent coughing without the presence of CHF. The use of resting respiratory rate monitoring provides a useful tool that may help owners and the managing DVM interpret the individual patient’s CHF status. Dogs without CHF typically have a resting respiratory rate of < 30 breath per minute, and individual dogs have a consistent baseline resting respiratory rate over time. Owners can be trained to obtain their dog’s normal resting respiratory rate and to notify the DVM if an increase above that baseline occurs when clinical signs such as coughing or dyspnea are appreciated. Screening thoracic radiographs remain the "gold standard" for detecting the presence of CHF. BNP testing may be helpful in differentiating between patients with respiratory distress secondary to primary airway disease and patients with respiratory distress secondary to CHF, but the normal range still needs to be better defined, and the lack of an in hospital test limits the utility. Echocardiography provides useful staging information and is valuable for making some treatment decisions and providing prognostic information, but it does not differentiate between patients with non-cardiac respiratory signs and patients with CHF. Maintaining good body condition and providing regular physical activity should be emphasized in patients with mild CDVD as beginning medical therapy early in the disease process has not been shown to provide clinical benefit. There is no consensus on interpreting results from multiple studies evaluating the use of ACE inhibitors prior to the onset of CHF, and the use of pimobendan prior to the onset of CHF is being evaluated in an ongoing study. A general rule of thumb for initiating medical therapy in dogs with CDVD is that all patients with CHF should be started on medical therapy, and patients deemed at high risk for developing CHF during the next 3 to 6 months may benefit from medical therapy. The classic treatment strategy when initiating medical therapy for CHF in dogs with CDVD involves the use of "triple therapy" with furosemide, pimobendan, and an ACE inhibitor. Common add on therapies may include spironolactone, digoxin, hydrochlorothiazide, vasodilators, and antiarrhythmic medications. The CVSG cardiology service is proud to be participating in a funded clinical trial evaluating the efficacy of a new drug combination for managing patients with CDVD that have experienced an episode of CHF. Qualifying patients may be of any age, breed, or sex, and must weight > 5.5 lb. A grade 3/6 or > left sided heart murmur consistent with mitral regurgitation must be present and patients must have had radiographic evidence of pulmonary edema within 7 days of enrolling in the study. Exclusion criteria include treatment for heart disease/heart failure prior to 7 days before potential enrollment, concurrent forms of heart disease other than CDVD, and severe or uncontrolled concurrent non-cardiac conditions (e.g. cancer). If you have a patient that you believe may qualify for the study, or any questions about the study, please contact the cardiology service (773-281-7110) and ask to speak to one of the cardiology technicians.

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