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→Diagnosis
== Diagnosis ==
== Diagnosis ==
===History and Physical Examination===
Asymptomatic (occult) phase
* Soft, systolic heart murmur
* Arrhythmia with pulse deficits
Overt clinical phase
* History may include: exercise intolerance, lethargy, anorexia, muscle wasting (cardiac cachexia), syncope, abdominal distension (ascites)
* Systolic heart murmur
* Arrhythmia with pulse deficits
* Increased respiratory rate and effort, increased bronchovesicular sounds, pulmonary crackles (left-sided congestive heart failure)
* Weakness
* Jugular venous distension and/or jugular pulsation, hepatomegaly, ascites (right-sided congestive heart failure)
===Thoracic Radiographs===
Radiographs are performed in the clinical phase to diagnose congestive heart failure and monitor response to treatment.
===Electrocardiography (ECG)===
A normal ECG does not rule out the presence of DCM, but is the test of choice for detecting arrhythmias. In the occult phase, arrhythmias may be the first indication of disease. The following are associated with a high index of suspicion for occult DCM:
* One or more VPC in an at-risk breed
* Atrial fibrillation appears to be an early sign of disease in Irish Wolfhounds, whereas other breeds develop atrial fibrillation in advanced disease.
* 24 hour Holter ECG recording:
** Greater than 100 VPCs is suggestive of DCM or ARVC
** Between 50 and 100 VPCs in an at-risk breed is suspicious. Holter recording should be repeated in 3-6 months.
During the clinical phase, the following may be detected:
* Occasional VPCs or superventricular premature complexes (SVPCs)
* Ventricular tachycardia
* Atrial fibrillation
* Left bundle branch block morphology
Echocardiography will show a hypokinetic left ventricle (i.e. reduced fractional shortening therefore reduced contractility), reduced ejection fraction (i.e. % end diastolic volume ejected at systole), decreased ventricular wall thickness, left atrial enlargement and mitral regurgitation.
===Echocardiography===
Echocardiographic changes may include left ventricular dilation (increased left ventricular end-diastolic diameter), systolic dysfunction (reduced myocardial contractility), mitral regurgitation secondary to dilation of the mitral annulus and atrial enlargement.
===Blood Tests===
Changes on serum biochemistry analysis may include [[azotemia]], this is common in dogs receiving diuretic therapy and is usually pre-renal in nature. Electrolyte abnormalities, such as mild hyponatraemia and hypokalaemia, are also common in dogs with congestive heart failure.
Taurine deficiency may contribute to a DCM phenotype in the American Cocker Spaniel, Dalmatian, Labrador Retriever and Golden Retriever. Most dogs with taurine-deficient DCM will have plasma taurine levels <25nmol/L. This is important to recognize, as in these cases cardiac function and prognosis can be substantially improved by taurine supplementation.
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