Page 308 - Feline Cardiology

316 Section H: Arterial Thromboembolism

Initiating anticoagulant therapy in cats with symptomatic or asymptomatic heart disease

Is there documented evidence of previous aortic thromboembolism?
No or not sure
Yes
Thoracic radiographs Not available or
and/or echocardiogram not possible

Is there spontaneous echocardiographic Yes
contrast (“smoke”) in any cardiac chamber?
No or not sure
(e.g., if no echo)
Is there left atrial enlargement? CONSIDER ANTICOAGULATION
• Radiographic Yes • Benefit unproven; must be
and/or weighed against drawback ANTICOAGULATE
• Echocardiographic (LA:Ao > 1.9:1) of daily administration (usually daily for life)
• Also minimize risk of
trauma/bleeding
Arterial Thromboembolism Optional: are there 2 or more • No demonstrable benefit • Clopidogrel 18.75 mg PO q 24h, or
(e.g., keep indoors)
No or
No or
NO BASIS FOR
not sure
not sure
ANTICOAGULATION
• Potential for harm if poor compliance
(tachycardia/fractiousness if cat
resists pilling), interference with
other disease processes, owner
• Aspirin 81 mg PO q 48–72h, or
markers of hypercoagulability?
frustration
• Aspirin 5 or 20 mg PO q 24h, or
• ↑ plasma [fibrinogen]
• ↑ Factor VIII coagulant activity
• Enoxaparin 1.5 mg/kg SC q 6h, or
• ↓ antithrombin III activity
• Dalteparin 150 IU/kg SC q 4h, or
• ↑ thrombin-antithrombin complex
• Clopidogrel + aspirin
• ↑ plasma [d-dimer] No • Warfarin 0.5–1 mg PO q 24 titrated to PT, or
Yes
Figure 20.11. An algorithm for describing the decision-making process for initiating anticoagulant therapy in symptomatic and asymp-
tomatic cats.
and high dose (≥40 mg/cat q 24 hours, n = 18) aspirin Clopidogral and Abciximab
therapy in recurrence of ATE (a total of 11 (25%) cats
had ATE recurrence) in a large retrospective study and Clopidogrel is a thienopyridine derivative which irre-
fewer adverse effects were noted with the lower dose versibly antagonizes ADP receptors on platelet mem-
(Smith et al. 2003). No studies evaluating platelet func- branes, thereby interfering with primary and secondary
tion were performed in either group. Twenty-two percent platelet aggregation. It has no direct effects on arachi-
of the cats receiving high-dose aspirin exhibited gastro- donic acid metabolism. Clopidogrel also inhibits the
intestinal signs compared to 4% of the cats in the low ADP-induced conformational change of the glycopro-
dose aspirin group (Smith et al. 2003). Using a dose of tein IIb/IIIa receptor and reduces myointimal prolifera-
5 mg/cat requires compounding which adds an addi- tion in vascular smooth muscle (Hogan et al. 2004). In
tional owner expense. Using one-quarter of a baby vitro, there is a reduced response to vasoactive sub-
aspirin every 3rd day does not require compounding stances, including serotonin. The drug is used exten-
and is a reasonable option (1/4 baby aspirin corresponds sively in human medicine and results from several small
to 20.25 mg aspirin). Aspirin use requires no specific feline studies are encouraging that it will find a place for
anticoagulation monitoring and adverse effects (par- veterinary use as well. One small feline study demon-
ticularly with the low dose) are uncommon. Aspirin strated that clopidogrel administration compared to
does not have the prothrombotic effects of warfarin and placebo resulted in improved motor and neurologic
therefore overlapping of therapy with heparin is not function during recovery in a feline embolic model
necessary. (Hogan et al. 2006) but not change in collateral perfu-