JFMS CLINICAL PRACTICE 459
C L I N I C A L R E V I EW
Journal of Feline Medicine and Surgery (2012) 14, 459–470
Virginia Luis Fuentes
Risks, realities and a rational first-line approach
Practical relevance: Feline arterial thromboembolism (ATE) is a common but devastating complication of myocardial disease, often necessitating euthanasia. A combination of endothelial dysfunction and blood stasis in the left atrium leads to local platelet activation and thrombus formation. Embolisation of the thrombus results in severe ischaemia of the affected vascular bed.
With the classic ‘saddle thrombus’ presentation of thrombus in the terminal aorta, the diagnosis can usually be made by physical examination.
The prognosis is poor for cats with multiple limbs affected by severe ischaemia, but much better where only one limb is affected or motor function is present.
Patient group: Cats with left atrial enlargement secondary to cardiomyopathy are typically predisposed, although cats with hyperthyroidism, pulmonary neoplasia and supravalvular mitral stenosis may also be at risk.
Management: Analgesia is the main priority, and severe pain should be managed with methadone or a fentanyl constant rate infusion. Congestive heart failure (CHF) requires treatment with furosemide, but tachypnoea due to pain can mimic signs of
CHF. Thrombolytic therapy is not recommended, but antithrombotic treatment should be started as soon as possible. Aspirin and clopidogrel are well tolerated.
Evidence base: Several observational studies of
ATE have been reported. No randomised, blinded, controlled studies have been reported in cats at risk, for either treatment or prevention of ATE, although such a study comparing aspirin and clopidogrel in cats is currently under way.
Virginia Luis Fuentes
MA VetMB PhD CertVR DVC MRCVS
DipACVIM DipECVIM-CA (Cardiology)
Department of Veterinary Clinical Sciences,
The Royal Veterinary College,
Hawkshead Lane, North Mymms,
Hatfield, Hertfordshire AL9 7TA, UK
Cats and ATE
Arterial thromboembolism (ATE) occurs when a thrombus formed in one part of the circulation embolises to a peripheral artery (Figure 1).
Arterial blood flow is decreased to tissues distal to the thrombus as a result of mechanical obstruction and vasoconstriction of the collateral blood supply. In cats, the source of the thrombus is generally the left auricular appendage (LAA) (Figure 2). Cats are particularly prone to ATE in comparison with other species, which is partly (but not entirely) explained by their high prevalence of myocardial disease.
Most cats presenting with ATE have underlying cardiac disease.1,2 Males are over-represented, but this probably reflects the male predisposition to myocardial disease.3 Hypertrophic cardiomyopathy (HCM) is the most common underlying condition associated with
ATE (being the most common type of myocardial disease), but cats with any form of cardiomyopathy (other than arrhythmogenic right ventricular cardiomyopathy) can be presented with ATE. The risk of ATE appears to be greatest with more severe forms of cardiomyopathy, irrespective of the specific type of myocardial disease. Cats with secondary myocardial disease are also at risk, which includes euthyroid cats with treated hyperthyroidism.1 Some congenital heart defects such as supravalvuDOI: 10.1177/1098612X12451547 © ISFM and AAFP 2012
Figure 1 Thrombus (arrow) present in the terminal aorta in a cat presented with ATE
Two video recordings are included in the online version of this article at
DOI: 10.1177/1098612X12451547 at TEXAS SOUTHERN UNIVERSITY on December 13, 2014jfm.sagepub.comDownloaded from 460 JFMS CLINICAL PRACTICE lar mitral stenosis have been associated with
ATE, but this is an uncommon cause.1 There is also a risk of systemic thromboembolism with septic emboli in infective endocarditis, but this is also rare.
The most common non-cardiac cause of
ATE in cats is pulmonary neoplasia, although this is caused by tumour emboli rather than a true thrombus.1 Rarely, no underlying condition is found.
ATE is probably one of the most distressing conditions encountered in feline practice, particularly as there is often no advance warning.
Owners experience the initial trauma of finding their cat paralysed and in pain, only to face the subsequent devastating news of the poor prognosis. Owners of affected cats are often advised that their pet may not survive the initial episode; or, even if it survives to discharge, may succumb to a future bout of thromboembolism. While both of these statements may be true, it is also true that some cats will regain completely normal motor function following an initial ATE episode, and ATE survivors are more likely to die of congestive heart failure (CHF) than ATE.1
Fortunately, only a minority of cats with cardiomyopathy will go on to develop ATE, but
HCM is sufficiently prevalent that ATE is still a commonly encountered problem in feline practice.
The true prevalence of ATE is not known, as most reports originate from referral institutions. Smith et al reported an overall prevalence of ATE of less than 0.6% of cats seen at
REV IEW / Feline ATE
Figure 2 Echocardiographic image showing a thrombus (arrow) in the left auricular appendage in a cat with HCM and left atrial enlargement. This is a right parasternal short axis view.
Ao = aortic valve, LA = left atrium
The risk of ATE appears to be greatest with more severe forms of cardiomyopathy, irrespective of the specific type of myocardial disease. the Veterinary Teaching Hospital of the University of Minnesota.1 The reported prevalence in cats with HCM varies from 12–21%,4,5 although these are biased population samples that probably reflect a particularly high proportion of symptomatic cats. Recent studies of apparently healthy cats suggest that the prevalence of subclinical HCM may be much higher than previously thought (potentially up to 15% of adult cats),6,7 so the prevalence of ATE in cats with HCM is probably much lower than 12%, as ATE is usually seen only in cats with the most advanced cardiomyopathies. Conversely, many cats presenting with ATE in first opinion practice are euthanased, and are therefore not accounted for in prevalence estimates based on referral populations.