Page 227 - Cote clinical veterinary advisor dogs and cats 4th

98 Atrial Rupture

Chronic Treatment • It is generally not recommended to use PROGNOSIS & OUTCOME
Calcium channel blockers: calcium channel blockers in conjunction with Depends on underlying cause and cardiac
VetBooks.ir to maximum of 4 mg/kg) PO q 8h (dog), Possible Complications disease
beta-blockers due to combined negative
• Diltiazem (Cardizem): 0.5-2 mg/kg (titrated
effects on blood pressure and contractility.
7.5 mg/dose PO q 8-12h (cat)
• Diltiazem-sustained release (Dilacor-XL,
Cardizem-CD): 1.5-6 mg/kg PO q 12-24h • Calcium channel blockers, beta-blockers: PEARLS & CONSIDERATIONS
(dog), 30-60 mg/dose PO q 12-24h (cat) much more likely to cause complications Comments
• Verapamil: 0.5-3 mg/kg PO q 8h (dog) with IV use. Use repeated small doses with The absence of a P′ wave cannot always dif-
Beta-blockers: monitoring instead of single large dose. ferentiate a VPC from an APC. The P′ wave
• Atenolol (start low, titrate to effect): ○ Negative inotropism (especially verapamil before an APC may be superimposed (hidden)
0.5-1 mg/kg PO q 12-24h or start at and beta-adrenergic blockers) (use with in the preceding complex. Additionally, if a
6.25-12.5 mg q 12-24h and up-titrate to caution with left ventricular systolic VPC is only mildly premature a sinus P wave
effect (dog); 6.25-12.5 mg/dose PO q 12-24h dysfunction) may be identified.
(cat) ○ Hypotension (lesser risk with beta-blockers
Digoxin: 0.005-0.01 mg/kg PO q 12h, not to compared to calcium channel blockers) Technician Tips
exceed 0.25 mg PO q 12h (or 0.00425 mg/ ○ Severe bradycardia or asystole APCs are differentiated from ventricular pre-
kg q 12h for elixir) (dog); 0.03125 mg/dose ○ Gastrointestinal (GI) signs with oral mature complexes on ECG based on a narrow
(one quarter of 0.125-mg tablet) PO q 48-72h calcium channel blockers QRS appearance, which is similar to the normal
(cat) • Chronic beta-blocker therapy should not be sinus beats.
Combination therapy is sometimes necessary abruptly discontinued (risk of excessive
(see Drug Interactions). catecholamine-mediated tachycardia). SUGGESTED READING
• Digoxin Tilley LP: Analysis of common canine cardiac
Drug Interactions ○ GI signs related to toxicity (anorexia, arrhythmias. In Tilley LP, editor: Essentials of canine
• Simultaneous administration of digoxin with vomiting, diarrhea) and feline electrocardiography, Philadelphia, 1992,
verapamil, amiodarone, or quinidine can ○ AV block, other arrhythmias Lippincott Williams & Wilkins, pp 127-207.
increase digoxin serum concentrations and AUTHOR: Rebecca L. Malakoff, DVM, DACVIM
potentially cause digoxin toxicosis. Recommended Monitoring EDITOR: Meg M Sleeper, VMD, DACVIM
• There are many potential drug interactions • Serial ECGs
associated with digoxin, and the patient’s • Digoxin: measure trough (6-8 hours after
complete medication regimen should be dose) digoxin serum level 7-10 days after
reviewed. starting therapy or adjusting dose

Atrial Rupture Client Education
Sheet

BASIC INFORMATION • Ruptured chordae tendineae • Pale mucous membranes
• Chronic mitral valve degeneration (mitral • Loud systolic murmur at left apex
Definition regurgitation due to myxomatous valve • If hemopericardium is present, there may
Partial- or full-thickness endomyocardial split- disease) be signs of cardiac tamponade (p. 773).
ting that occurs occasionally in dogs with severe
mitral valve disease, marked left atrial enlarge- ASSOCIATED DISORDERS Etiology and Pathophysiology
ment, and elevated left atrial pressure • Congestive heart failure • Left atrial rupture is caused by increased
• Hemopericardium wall tension associated with marked left
Synonyms atrial enlargement and elevated left atrial
Endomyocardial split of the left atrium, left Clinical Presentation pressure.
atrial tear, left atrial split DISEASE FORMS/SUBTYPES • These changes usually are due to chronic
• Nonperforating endocardial splits are found mitral valve disease with valve incompetence
Epidemiology only at necropsy. and coexisting endocardial degeneration, but
SPECIES, AGE, SEX • Perforating endomyocardial splits cause endocardial splitting also may occur in young
• Most often seen in older dogs hemopericardium or acquired atrial septal dogs with patent ductus arteriosus and
• More common in males defects. marked left atrial enlargement.
• Multiple splits are usually present, and a
GENETICS, BREED PREDISPOSITION HISTORY, CHIEF COMPLAINT deep endomyocardial split may fully perforate
More common in Cavalier King Charles • Long-standing mitral insufficiency the left atrial wall, resulting in hemoperi-
spaniels and other chondrodystrophic breeds • Dyspnea cardium or an acquired atrial septal defect,
such as cocker spaniels, dachshunds, and • Acute collapse depending on its location.
miniature poodles • Healed, endothelialized splits are often
PHYSICAL EXAM FINDINGS present in dogs with fresh thrombus-covered
RISK FACTORS • Nonspecific acute collapse splits.
• Left atrial enlargement due to long-standing • Tachycardia • Dogs with acquired atrial septal defects
mitral regurgitation • Weak pulses usually have otherwise healed splits.

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