Ventricular Fibrillation

Ventricular Fibrillation

Basic Information image

Definition

Fatal ventricular tachyarrhythmia attributable to reentry, causing ventricular activation to be so rapid and uncoordinated that contractile function is lost. Cardiac output is essentially zero.

Epidemiology

Risk Factors

• Any cause of severe electrolyte imbalance (eg, ruptured bladder)

• Severe cardiac disease

• Hypoxia

• Severe systemic disease

Clinical Presentation

History, Chief Complaint

• Weakness, collapse

• Signs of cardiac failure

• Suspicion of intoxication (cardiac glycosides)

• Electrical cardioversion

• Sudden death

Physical Exam Findings

• Physical examination findings immediately before the onset of ventricular fibrillation (VF)

image Signs of ventricular ectopy: Ventricular premature complexes (VPCs) or ventricular tachycardia (VT)
image Signs of severe cardiac disease
image Signs of severe systemic disease
image Signs of bladder rupture

• Physical examination findings when VF occurs (Figure 1)

image Instantaneous collapse with no palpable pulse. A weak pulsation may occasionally be observed in the jugular vein caused by atrial contractions.
image Death within seconds to minutes; always fatal.
image

FIGURE 1 Ventricular fibrillation in a horse with oleander intoxication. P waves can still be identified immediately after the onset of fibrillation.

Etiology and Pathophysiology

• Ventricular ectopy (VPCs or VT) usually precedes VF and is caused by enhanced automaticity or triggered activity because of cardiac disease, electrolyte imbalances, systemic disease, drugs, or toxicity.

• Ventricular ectopy during the vulnerable period of the ventricular myocardium (ie, during the T wave) may suddenly initiate reentry, which results in VF. This reentry phenomenon can be initiated by:

image A single VPC during the vulnerable period
image Deterioration of ventricular tachycardia or ventricular flutter into VF
image Deterioration of torsades de pointes
image Electrical cardioversion

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Ventricular Fibrillation

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