By Rebecca Malakoff, DVM, DACVIM (Cardiology)
Ten percent of dogs presenting to primary veterinary care have heart disease, and 75% of these patients have chronic valvular disease. In 2009, a panel of veterinary cardiologists published a consensus statement in the Journal of Veterinary Internal Medicine to provide guidance in the diagnosis and treatment of canine chronic valvular heart disease. One of the most useful tools to emerge from the consensus statement is a new classification system, categorizing dogs affected with chronic valvular disease. Many cardiologists have adopted this system into the diagnosis section of their echocardiographic reports (including the Angell Cardiology team), and the article below will aid primary care veterinarians in understanding the new system and terminology.
The Need for a New Classification System
Previous classification systems for describing patients with chronic valvular disease existed, but limitations were identified with their use. The schemes most familiar to veterinarians were the modified New York Heart Association (NYHA) and the International Small Animal Cardiac Health Council (ISACHC) systems. Both of these are functional classification systems, which divide patients according to severity of clinical signs. For example, the modified NYHA classification system is described as:
Class I: patients with asymptomatic heart disease
Class II: patients having symptoms only during strenuous activities
Class III: patients having clinical symptoms with routine activities
Class IV: patients with heart disease causing severe symptoms even at rest
Functional classification systems are based on relatively subjective assessments of clinical signs, and treatments may not differ substantially across the functional classes. Another limitation of both the modified NYHA and ISACHC systems is that they fail to make any distinction between patients who have never had congestive heart failure (and are asymptomatic without the use of medications), and those whose congestive symptoms have been resolved and controlled with the use of diuretics and other cardiac medications. The ACVIM panel members therefore created a new system, with the goal of more objectively categorizing patients and linking severity of signs to appropriate treatments at each stage of heart disease. In the new scheme, patients are expected to advance from one stage to the next, and they will never revert to an earlier stage, even with control of congestive symptoms by medications. The panel’s classification system, now referred to as the ACVIM/ECVIM Consensus classification system (or ACVIM Consensus classification system), describes four basic stages of heart disease and failure:
| Echocardiographic still of a right parasternal long-axis view demonstrating chronic degenerative mitral valve disease, with significant mitral regurgitation (green color Doppler jet flowing into the left atrium).
Stage A: patients at high risk for developing heart disease, but with no current identifiable lesions.
(For example, a Cavalier King Charles Spaniel, without a heart murmur or echocardiographic evidence of degenerative mitral valve changes, would be considered a Stage A patient based on the breed predisposition for chronic valvular heart disease.)
Stage B: patients with structural heart disease, who have never had clinical signs of heart failure. This stage is further subdivided into Stage B1 and B2.
Stage B1: patients without radiographic or echocardiographic evidence of cardiac remodeling in response to chronic valvular disease (no evidence of left atrial or left ventricular enlargement).
Stage B2: patients with radiographic and/or echocardiographic evidence of left-sided heart enlargement (indicating hemodynamically significant valve regurgitation).
Stage C: patients with past or current clinical signs of congestive heart failure.
(The inclusion of the patients with past congestive heart failure signs means the patients can only advance through this classification system — once they are a Stage C patient, they will never revert to a Stage B2 patient.)
Stage D: patients with end-stage disease and clinical signs of congestive heart failure that are refractory to standard therapy, and require specialized treatment to remain comfortable.
The new ACVIM classification system is user-friendly, and quickly provides clinically relevant information about the severity of chronic valvular heart disease in a particular patient.
If you have any questions about the new system, or questions about your patients with cardiac disease, please feel free to contact the Angell Cardiology team at email@example.com or 617 541-5038. Dr. Malakoff can also be reached at firstname.lastname@example.org.
1. Atkins C, Bonagura J, Ettinger S, et al. Guidelines for the Diagnosis and Treatment of Canine Chronic Valvular Heart Disease. J Vet Intern Med 2009;23:1142–1150.