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AN EVERYDAY APPROACH TO CANINE DEGENERATIVE MITRAL VALVE DISEASE | View the Guidelines for the Diagnosis and Treatment of Canine Chronic Valvular Heart Disease (2009) at onlinelibrary.wiley.com/ doi/10.1111/j.1939-1676.2009.0392.x/full. Thoracic Radiography Measuring heart size is extremely useful in assessing severity of DMVD (Figure). Thoracic radiography is a relatively simple and cost-efficient tool for assessing heart size and identifying the presence of pulmonary venous distention or edema. Measurement systems, such as the vertebral heart size (VHS) system, are useful in reducing inter- observer variability and tracking longitudinal changes in a patient's heart size. The VHS technique has been well-described.2 Normal VHS size in dogs is < 10.7; severe heart enlargement and hence, severe DMVD, is usually considered to be > 12. I recommend performing baseline thoracic radio- graphs to assess heart size on every dog with a newly discovered murmur. Baseline radiographs establish the initial degree of disease severity and assess rate of disease progression during subsequent follow- up (recheck radiographs should be performed 6–12 months after initial detection and are often repeated every 3–12 months depending on rate of progression). Electrocardiography & Echocardiography The value of electrocardiography (ECG) and echocar- diography (echo) in the diagnosis and monitoring of DMVD varies from case to case. Clearly, ECG is the gold standard for assessment of arrhythmias, but ECG criteria for heart enlargement (eg, increased R wave amplitude indicating left ventricular enlargement) are relatively insensitive. Echo is the gold standard for assessment of cardiac structure and function, but in most cases of DMVD, especially those that are relatively mild, the information obtained by echo rarely adds to what was already known from the physical examination and thoracic radiographs. While echo is helpful in some cases to detect concurrent cardiac disease, such as tricuspid regurgitation or pul- monary hypertension, lack of echo should not affect the ability to make an initial assessment of disease severity based on radiographic heart size. In most cases of DMVD, appropriate diagnostic, mon- itoring, and therapeutic decisions can be made without echo provided that radiographs are performed. MONITORING PROGRESSION OF DMVD It is reassuring to remember that most dogs with DMVD will not develop enough MR to cause conges- tive heart failure or clinical signs.3 Classifying Patients By performing longitudinal examinations of heart size, clinicians can gradually stratify dogs into (1) those that have slowly progressive disease and are unlikely to develop signs versus (2) those with more rapidly progressing disease that are at risk for future heart failure. In general, it is very uncommon for dogs to develop congestive heart failure with VHS < 11.5. High-Risk Patients Once VHS t 11.5, both absolute VHS and rate of increase in VHS are linked to risk of heart failure. In these patients, more frequent rechecks and increased owner vigilance for subtle signs of early heart failure, such as mild increase in respiratory rate or effort while at rest, decreased activity tolerance, or lethargy, is recommended. Previous studies4 have shown that a rate of VHS increase > 0.25 vertebra over a 3-month period suggests that risk for heart failure is high. SLOWING PROGRESSION OF DMVD Unfortunately, there are no proven interventions that slow the rate of DMVD progression or significantly delay the onset of heart failure in preclinical DMVD. Role of Ace Inhibitors While 2 large studies5,6 failed to demonstrate that ACE inhibitors significantly affected the primary endpoint of first-onset heart failure, the majority of cardiolo- gists and members of the consensus panel on DMVD recommend ACE inhibitors prior to onset of heart failure, after cardiac enlargement is detected.7 contrast, most cardiologists do not advocate use of furosemide prior to onset of congestive heart failure. Monitoring & Prompt Therapy Other medications are being assessed in ongoing clinical trials, but until these trials are completed, I recommend that dogs at high risk for heart failure are simply monitored more closely, both by the clinician and owner. Detection of subtle signs of heart failure as previously mentioned followed by prompt initiation of conventional therapy can prevent development of severe and life-threatening heart failure that requires emergency visits, intravenous treatment, and pro- longed hospitalization. The preclinical course of disease can be many years and only a minor- ity of dogs will progress to the point of heart failure. TREATMENT OF DMVD Clinical Signs In dogs with severe DMVD, progressive MR and chronic neurohormonal activation ultimately leads to congestion in the form of pulmonary edema. Dogs often present for respiratory signs, ranging from: UÊ il`ÊinVÀi>ÃiÊinÊÀiëiÀ>ÌoÀÞÊÀ>Ìi UÊ nVÀi>Ãi`ÊivvoÀÌÊÜiÌhÊ>L`omin>lÊVom«oninÌÊ UÊ Õlmin>nÌÊÀiëiÀ>ÌoÀÞÊ`iÃÌÀiÃÃ°Ê Coughing is often considered a sign of heart failure, yet most dogs with the isolated complaint of cough July/August 2012 Today's Veterinary Practice 23 In