Page 412 - Feline Cardiology

436 Section Q: Which Drug for Which Disease?

(e.g., <160 beats/minute despite being in congestive • Warfarin (0.25–0.6 mg/cat PO q 24h, adjusted to
heart failure) or cat is hypotensive, in which case beta maintain prothrombin time between 1.5 and 2.5
blocker may be contributing and discontinuation is times highest normal value); or
recommended. • Low molecular weight heparin (dalteparin: 150 IU/
Calcium-channel blocker: May have less negative ino- kg SC q 4h; enoxaparin 1.5 mg/kg SC q 6–8 h); phar-
tropic effect compared to beta blockers, so an ideal macokinetics in the cat require short dosage inter-
choice for treatment of supraventricular tachyar- vals, which may be impractical for many owners; or
rhythmias in patients with heart failure and myocar- • Clopidogrel (18.75 mg/cat PO q 24h with food)
dial failure, but it will be ineffective for ventricular (Hogan and Ward 2004; Hogan et al. 2004)
arrhythmias.
Nitrates: nitroglycerin topical ointment acceptable irre- SYSTEMIC HYPERTENSION
spective of cause of CHF (venodilator); nitroprusside As defined by objective guidelines (Brown et al. 2007),
is a potent balanced arterial and venous dilator and is systemic hypertension warranting treatment in cats con-
contraindicated in cases of hypertrophic obstructive sists of systolic blood pressure, accurately measured and
cardiomyopathy, because arteriodilation may increase with the least possible level of patient anxiety, that
left ventricular outflow tract obstruction (LVOTO), exceeds 180 mm Hg. A gray zone exists between 160 and
or in hypotensive patients. 180 mm Hg, where treatment is warranted if target organ
Oxygen supplementation: (40–50% FiO2; or high damage is observed or considered to be imminent:
oxygen flow rate in a modified oxygen cage).
Acceptable provided it can be given without compro- • Amlodipine 0.625–1.25 mg/cat PO q 24h. Safe and
mising monitoring or causing hyperthermia or hyper- efficacious. Goal is reduction of arterial blood pres-
carbia, as has occurred in closed oxygen cages.
sure by 10–20% (ideally to high-normal levels), and
improvement in target organ damage, if any has
AORTIC THROMBOEMBOLISM
occurred (Henik et al. 1997; Elliott et al. 2001).
Acute treatment consists of parenteral administration of • Benazepril, enalapril. No demonstrable efficacy as
drugs to delay (anticoagulants) or actively lyse (throm- antihypertensives in cats, but may be considered as an
bolytics) blood clots, analgesics, plus supportive care. additional medication in cats not adequately respond-
Both approaches have their proponents, with favor gen- ing to high dose amlodipine. May be used in hyper-
erally falling to a more conservative (anticoagulant) tensive cats that have proteinuria secondary to protein
approach due to the lower incidence of catastrophic losing nephropathy, and can be used in conjunction
adverse effects and high cost of thrombolytic therapy with amlodipine while carefully monitoring blood
coupled with the same short-term survival rate. pressure.
Chronic treatment consists of anticoagulation to • Atenolol. No demonstrable efficacy as an antihyper-
reduce the risk or rethrombosis/reembolization and spe- tensive in cats, but may be useful in markedly tachy-
cific therapy for the underlying heart disease/heart cardic cats with inadequate blood pressure reduction
failure if present. on high-dose amlodipine, added to the amlodipine
(not as a substitute).
Thrombolysis: requires 24-hour intensive care monitor-
ing for emergency treatment of life-threatening reper- CONGENITAL HEART DISEASE
fusion syndrome or hemorrhage
Because congenital heart malformations may be identi-
• Streptokinase (90,000 IU IV, then 45,000 IU IV CRI). fied early through auscultation of a heart murmur in an
Incidence of bleeding and reperfusion injury matches asymptomatic cat/kitten, the first goal of treatment
or exceeds benefits in cats. Not recommended in cats. should be to cure the patient with surgical repair of the
Which Rx? 1.5–5h). Similar effects and results as streptokinase. lesion.
• Tissue plasminogen activator (5 mg/cat IV CRI over
Surgical correction of congenital cardiovascular
Not recommended in cats.
following:
Anticoagulation: defects can realistically be accomplished with the
• Acceptable treatments (none has been shown to be • Patent ductus arteriosus (coil embolization or thora-
superior to any other, nor superior to no treatment): cotomy and ligation)
• Aspirin, regular dose (81 mg/cat PO q 3d); or • Vascular ring anomaly (thoracotomy for ligation and
• Aspirin, low-dose (5 or 20 mg/cat PO q 3d); or division of ligamentum arteriosum)