Use of Rheolytic Thrombectomy in the Treatment of Feline Distal Aortic Thromboembolism

The Feline Cardiomyopathies: 1. General concepts

PRACTICAL RELEVANCE

The feline cardiomyopathies are the most prevalent type of heart disease in adult domestic cats. Several forms have been identified (see Parts 2 and 3), with hypertrophic cardiomyopathy (HCM) being the most common. Clinically the cardiomyopathies are often indistinguishable. Cats with subclinical cardiomyopathy may or may not have characteristic physical examination findings (eg, heart murmur, gallop sound), or radiographic cardiomegaly. Cats with severe disease may develop signs of heart failure (eg, dyspnea, tachypnea) or systemic arterial thromboembolism (ATE; eg, pain and paralysis). Sudden death is possible. Treatment usually does not alter the progression from subclinical to clinical disease and often the treatment approach, once clinical signs are apparent, is the same regardless of the type of cardiomyopathy. However, differentiating cardiomyopathy from normal variation may be important prognostically.

PATIENT GROUP

Domestic cats of any age from 3 months upward, of either sex and of any breed, can be affected. Mixed-breed cats are most commonly affected but certain breeds are disproportionately prone to developing HCM.

DIAGNOSTICS

Subclinical feline cardiomyopathies may be suspected based on physical examination findings, thoracic radiographs and cardiac biomarker results but often the disease is clinically silent. The definitive clinical confirmatory test is echocardiography. Left heart failure (pulmonary edema and/or pleural effusion) is most commonly diagnosed radiographically, but point-of-care ultrasound and amino terminal pro-B-type natriuretic peptide (NT-proBNP) biomarker testing can also be useful, especially when the stress of taking radiographs is best avoided.

KEY FINDINGS

Knowledge of pathophysiological mechanisms helps the practitioner identify the feline cardiomyopathies and understand how these diseases progress and how they manifest clinically (heart failure, ATE). Existing diagnostic tests have strengths and limitations, and being aware of these can help a practitioner deliver optimal recommendations regarding referral.

CONCLUSIONS

Several types of feline cardiomyopathies exist in both subclinical (mild to severe disease) and clinical (severe disease) phases. Heart failure and ATE are the most common clinical manifestations of severe cardiomyopathy and are therapeutic targets regardless of the type of cardiomyopathy. The long-term prognosis is often guarded or poor once overt clinical manifestations are present.

AREAS OF UNCERTAINTY

Some cats with presumed cardiomyopathy do not have echocardiographic features that fit the classic cardiomyopathies (cardiomyopathy - nonspecific phenotype). Although no definitive treatment is usually available, understanding how cardiomyopathies evolve remains worthy of investigation.

Surgical embolectomy in a cat with cardiogenic aortic thromboembolism

A seven-year-old, spayed female, domestic longhair cat was referred for management of a sudden aortic thromboembolism (ATE). Echocardiography showed hypertrophic cardiomyopathy with severe left atrial enlargement. Ultrasonography of the abdominal aorta confirmed a large thrombus at the level of the aortic trifurcation, involving both iliac arteries. Considering the recent onset and bilateral involvement of the iliac arteries, the cat underwent emergent surgical embolectomy (SE) of the aortoiliac embolus. A standard caudal celiotomy was performed and the abdominal aorta was identified. Vessel loops with tourniquets were placed around the abdominal aorta proximal to the thrombus and on both iliac arteries distal to the thrombus. A full-thickness incision was made in the ventral surface of the aorta. The aortic thromboembolus was removed. The trifurcation was subsequently flushed with sterile saline. The SE resulted in a good outcome, with both clinical and ultrasound signs of complete reperfusion of the rear limbs within a few hours. Long-term treatment included antiplatelet drugs, furosemide and benazepril. Eighteen months after surgery, the cat was free of clinical signs, without recurrence of ATE or congestive heart failure. Based on the present case, SE could be considered as a feasible alternative to traditional conservative treatment in cats with a very recent onset of bilateral ATE.

Multicenter evaluation of signalment and comorbid conditions associated with aortic thrombotic disease in dogs

OBJECTIVE To assess signalment and concurrent disease processes in dogs with aortic thrombotic disease (ATD). DESIGN Retrospective case-control study. ANIMALS Dogs examined at North American veterinary teaching hospitals from 1985 through 2011 with medical records submitted to the Veterinary Medical Database. PROCEDURES Medical records were reviewed to identify dogs with a diagnosis of ATD (case dogs). Five control dogs without a diagnosis of ATD were then identified for every case dog. Data were collected regarding dog age, sex, breed, body weight, and concurrent disease processes. RESULTS ATD was diagnosed in 291 of the 984,973 (0.03%) dogs included in the database. The odds of a dog having ATD did not differ significantly by sex, age, or body weight. Compared with mixed-breed dogs, Shetland Sheepdogs had a significantly higher odds of ATD (OR, 2.59). Protein-losing nephropathy (64/291 [22%]) was the most commonly recorded concurrent disease in dogs with ATD. CONCLUSIONS AND CLINICAL RELEVANCE Dogs with ATD did not differ significantly from dogs without ATD in most signalment variables. Contrary to previous reports, cardiac disease was not a common concurrent diagnosis in dogs with ATD.

Is Treatment of Feline Hypertrophic Cardiomyopathy Based in Science or Faith?

Practical relevance Feline hypertrophic cardiomyopathy (HCM) is the most common cardiac disease of cats. Treatment of HCM is usually directed at controlling signs of congestive heart failure (CHF), preventing occurrence or recurrence of systemic thromboembolism or delaying/preventing/reversing progression of subclinical disease.

Study objective and design Despite the laudable goals of therapy, however, little objective evidence supporting therapeutic decisions has been published. We, therefore, hypothesized that cardiologists base their treatment strategies on information other than published clinically relevant science. To gain insight into therapeutic decisions that cardiologists and clinicians with an interest in cardiology (n = 99) make for cats with HCM, and on what information they base these decisions, we presented participants with, and asked them to select therapy for, 12 hypothetical scenarios of HCM (± CHF). Responses and justifications for treatment choices were compiled and compared with the results of a comprehensive literature search for published information about treatment of feline HCM.

Findings Evaluation of the therapeutic strategies chosen for these hypothetical cases of HCM suggests that cardiologists or clinicians with a strong interest in cardiology often prescribe treatments knowing that little documented evidence supports their decisions.

Prospective evaluation of tissue plasminogen activator in 11 cats with arterial thromboembolism

The purpose of this study was to evaluate the clinical response and side effects of tissue plasminogen activator (tPA) for the treatment of feline arterial thromboembolism (ATE). Previous reports of conservative and thrombolytic therapy were used to provide a historical control group of cats with ATE. The study was terminated due to a high frequency of adverse outcomes. tPA was administered to 11 cats with clinical signs of ATE for a median duration of 4.0 h (range 2-12h) prior to treatment. Pulses were restored in 40% of limbs within 4h and 53% within 24h. Motor function was restored to 33% of limbs within 24h. Adverse effects were seen in 11/11 cats following administration of tPA including azotemia (n=5), neurological signs (n=5), cardiac arrhythmias (n=5), hyperkalemia (n=4), acidosis (n=2) and sudden death in one cat. Ultimately, three cats (27%) were discharged alive from the hospital. While signs compatible with thrombolysis were noted in many cats following tPA administration, a high rate of side effects and low rate of hospital discharge were noted in this study.

Cardiogenic arterial thromboembolism causing non-ambulatory tetraparesis in a cat

A 1-year-old oriental cat was presented with a peracute onset of tetraparesis and vocalisation. Clinical findings were suggestive of multi-site thromboembolic disease, and this was confirmed on post-mortem examination. An echocardiogram showed severe restrictive cardiomyopathy and spontaneous echogenic contrast. To the author's knowledge, this is the first reported case of tetraparesis secondary to cardiogenic arterial thromboembolic disease. Thromboembolic disease should be included as a differential diagnosis for any cat presented with a peracute onset of paresis or paralysis, even if there is no history of cardiac disease.