Dilated cardiomyopathy with endocardial fibroelastosis in a juvenile Pallas cat

Clinical and necropsy evaluation of endocardial fibroelastosis in a mixed-breed cat with left side heart failure

A two-month-old, male intact, mixed-breed cat weighing 0.6 kg was presented with respiratory distress and anorexia. From the transthoracic echocardiographic, reduced fractional shortening (FS) and increased endocardial echogenicity were recognised with severe congestive heart failure (CHF). The kitten was administered an antibiotic and pimobendane under oxygen supplementation in an ICU cage. However, the respiratory condition worsened and the cat died the next day, and the subsequent necropsy and histopathology examinations confirmed endocardial fibroelastosis (EFE). There is a lack of information regarding the antemortem cardiac function evaluated by tissue Doppler imaging (TDI) in EFE cases. We report on the echocardiographic findings including the TDI in the EFE cat with a concomitant necropsy and histopathology confirmation in this paper. The echocardiographic findings showed presence of a ventricular false tendon within the left ventricle, a decrease in the left ventricular contractility (FS 11.1%, and a marked CHF). In this case, the echocardiographic findings were consistent with the human counterpart. However, these findings were like those of dilated cardiomyopathy and, hence, non-specific to EFE. As a result, veterinarians should keep in mind that endocardial fibroelastosis might be a possible reason for respiratory distress resulting from CHF with a low fractional shortening in young cats.

The Feline Cardiomyopathies: 3. Cardiomyopathies other than HCM

Practical relevance:

Although feline hypertrophic cardiomyopathy (HCM) occurs more commonly, dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), left ventricular noncompaction (LVNC) and cardiomyopathy – nonspecific phenotype (NCM; formerly unclassified cardiomyopathy) are all recognized in domestic cats.

Patient group:

Any adult domestic cat, of either sex and of any breed, can be affected.

Diagnostics:

The non-HCM cardiomyopathies are rarely suspected in subclinically affected cats, so most are first identified when a cat presents with signs of heart failure or systemic thromboembolic disease. The definitive clinical confirmatory test for these other feline cardiomyopathies is echocardiography.

Key findings:

‘Cardiomyopathy – nonspecific phenotype’ is a catch-all term that groups hearts with myocardial changes that either do not meet the criteria for any one type of cardiomyopathy (HCM, RCM, DCM, ARVC, LVNC) or meet the echocardiography criteria for more than one type. RCM is characterized by diastolic dysfunction due to fibrosis that results in a restrictive transmitral flow pattern on Doppler echocardiography and usually marked left or biatrial enlargement. DCM is characterized by decreased myocardial contractility and is rare in cats. When it occurs, it is seldom due to taurine deficiency. However, since taurine-deficient DCM is usually reversible, a diet history should be obtained, whole blood and plasma taurine levels should be measured and taurine should be supplemented in the diet if the diet is not commercially manufactured. ARVC should be suspected in adult cats with severe right heart enlargement and right heart failure (ascites and/or pleural effusion), especially if arrhythmia is present. Feline LVNC is rare; its significance continues to be explored. Treatment of the consequences of these cardiomyopathies (management of heart failure, thromboprophylaxis, treatment of systemic arterial thromboembolism) is the same as for HCM.

Conclusions:

While these other cardiomyopathies are less prevalent than HCM in cats, their clinical and radiographic presentation is often indistinguishable from HCM. Echocardiography is usually the only ante-mortem method to determine which type of cardiomyopathy is present. However, since treatment and prognosis are often similar for the feline cardiomyopathies, distinguishing among the cardiomyopathies is often not essential for determining appropriate therapy.

Areas of uncertainty:

The feline cardiomyopathies do not always fit into one distinct category. Interrelationships among cardiomyopathies in cats may exist and understanding these relationships in the future might provide critical insights regarding treatment and prognosis.

Endocardial fibroelastosis in a dog with congestive heart failure

In a 6-month-old, intact female, Japanese spitz presenting with severe dyspnea, lung ultrasonography revealed confluent B lines associated with severe echocardiographic left sided volume overload and systolic dysfunction. A congenital shunt or valvular dysplasia was not demonstrable. On electrocardiogram, there was a constant sinus rhythm, respectively sinus tachycardia. Cardiac troponin I was normal. Within 2 days of admission, the dog died of heart failure. On macroscopic postmortem examination, the left ventricle and atrium were markedly dilated, and the left ventricular endocardium had a mild diffuse whitish appearance. Histopathology revealed moderate to severe thickening of the left ventricular endocardium, composed mostly of abundant elastic fibers and fewer collagen fibers, diagnostic for endocardial fibroelastosis. In addition, there were mild degenerative changes of the atrioventricular valves. Endocardial fibroelastosis is a rare congenital disease and should be considered in a young dog if more common causes of echocardiographic dilated cardiomyopathy phenotype are ruled out.