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Basics ⬇

Basics

Definition

Ventricular rhythm associated with loss of organized ventricular activity resulting in cardiac muscle fibrillation.

ECG Features

  • Rapid, chaotic, irregular rhythm with bizarre waves or oscillations. Oscillations may be large (coarse fibrillation) or small (fine fibrillation).
  • No P waves.
  • No QRS complexes.

Pathophysiology

Loss of organized ventricular activity results in acute and profound drop in cardiac output, usually followed by death.

Systems Affected

  • Cardiovascular
  • All organ systems affected by loss of perfusion

Genetics

N/A

Incidence/Prevalence

Unknown

Signalment

Species

Dog and cat

Breed Predilections

None

Mean Age and Range

Unknown, but probably more common in old animals

Signs

Historical Findings

  • Severe systemic illness or cardiac disease in many patients
  • Previous cardiac arrhythmias in some patients

Physical Examination Findings

  • Cardiac arrest
  • Collapse
  • Death

Causes

  • Anoxia
  • Aortic stenosis
  • Autonomic imbalances, especially high sympathetic tone or administration of catecholamines
  • Cardiac surgery
  • Drug reactions-e.g., anesthetic agents, especially halothane and ultrashort-acting barbiturates, digoxin
  • Electrical shock
  • Electrolyte and acid-base imbalances
  • Hypothermia
  • Myocardial injury
  • Myocarditis
  • Shock

Risk Factors

Any severe systemic illness or heart disease

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

Rule out ECG artifact. Reapply ECG clips and ensure good skin contact and adequate alcohol applied to leads. Check pulse.

CBC/Biochemistry/Urinalysis

Abnormalities generally relate to the underlying metabolic problem that causes ventricular fibrillation.

Other Laboratory Tests

N/A

Imaging

N/A

Pathologic Findings

N/A

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

  • Rapidly fatal rhythm requiring immediate, aggressive treatment.
  • Patient will probably die without electrical cardioversion.

Direct Current Defibrillation

  • Immediate defibrillation is recommended when the duration of cardiopulmonary arrest caused by ventricular fibrillation is 4 minutes or less; otherwise, a 2-minute cycle of chest compressions before defibrillation is recommended. The dose of energy for initial defibrillation is 2–4 J/kg (biphasic defibrillator) or 4–6 J/kg (monophasic defibrillator).
  • If an initial shock is not successful, CPR is resumed for 2 minutes before defibrillation is attempted again. A 50% escalation in the energy delivered may be considered for subsequent defibrillation attempts.
  • If no access to electrical defibrillator, administer a precordial thump. Apply a sharp blow with your open fist to the chest wall over the heart. Rarely successful, but you have nothing to lose.

Nursing Care

Treat any problems such as hypothermia, hyperkalemia, and acid-base disorders.

Client Education

If the patient is converted back to a sinus rhythm, warn the owner that the patient is at high risk for recurrence of the arrhythmia in the immediate post-resuscitation period.

Surgical Considerations

N/A

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

  • Institute CPCR.
  • Epinephrine-the low dose (0.01 mg/kg) of epinephrine is recommended because high-dose therapy has not been associated with increased survival. A shortcut to calculate low-dose epinephrine volume for administration is 0.1 mL/10 kg. The dose may be repeated at 3- to 5-minute intervals.
  • Vasopressin-there is evidence that this drug may be equivalent to or even superior to epinephrine is some situations. The dose of vasopressin is 0.8 units/kg (dogs and cats), and the dose may be repeated at 3- to 5-minute intervals.
  • Once animal is successfully converted, administer intravenous lidocaine or amiodarone to lower the risk of refibrillation or development of ventricular tachycardia.
  • Lidocaine-the dose of lidocaine is 2 mg/kg (dogs, IV, IO, IT), and a shortcut to calculate the dose for the 2% (20 mg/mL) solution is 1 mL/10 kg.
  • Amiodarone-the dose of amiodarone is 5–10 mg/kg (dogs, IV), and it is diluted in 5% dextrose before administration. Hypotension is a common occurrence during amiodarone administration.

Precautions

Lidocaine raises the fibrillation threshold but makes defibrillation more difficult.

Alternative Drug(s)

Chemical conversion can be attempted if no access to electrical defibrillator. Administer 1 mEq potassium/kg and 6 mg acetylcholine/kg IC; rarely successful.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

  • CBC, urinalysis, biochemistry profile, arterial blood gases, and acid–base status.
  • If primary cardiac disease is suspected-echocardiogram and thoracic radiographs.
  • Monitor ECG closely and frequently.

Prevention/Avoidance

Careful monitoring of critically ill patients to prevent and correct acid–base disturbances, hypotension, and hypoxemia.

Possible Complications

  • Death
  • DIC and multiorgan failure

Expected Course and Prognosis

Most patients die because of either the arrhythmia or the underlying disease.

Miscellaneous ⬆

Miscellaneous

Age-Related Factors

None

Pregnancy/Fertility/Breeding

N/A

Abbreviations

  • CPCR = cardiopulmonary cerebral resuscitation
  • DIC = disseminated intravascular coagulation
  • ECG = electrocardiogram
  • IC = intracardiac
  • IL = intralingual
  • IT = intratracheal

Author Francis W.K. Smith, Jr.

Consulting Editors Larry P. Tilley and Francis W.K. Smith, Jr.

Suggested Reading

Cole SG, Otto CM, Hughes D: Cardiopulmonary cerebral resuscitation in small animals: a clinical practice review, part I. J Vet Emerg Crit Care 2002, 12:261–267.

Cole SG, Otto CM, Hughes D: Cardiopulmonary cerebral resuscitation in small animals: a clinical practice review, Part II. J Vet Emerg Crit Care 2003, 13:13–23.

Fletcher DJ, Boller M, Brainard BM, et al: RECOVER evidence and knowledge gap analysis on veterinary CPR. Part 7: Clinical guidelines. J Vet Emerg Crit Care 2012, 22:S102–131.

Kraus MS, Gelzer ARM, Moise S. Treatment of cardiac arrhythmias and conduction disturbances. In: Smith FWK, Tilley LP, Oyama MA, Sleeper MM, eds., Manual of Canine and Feline Cardiology, 5th ed. St. Louis, MO: Saunders Elsevier, 2015 (in press).

Tilley LP, Smith FWK, Jr. Electrocardiography. In: Smith FWK, Tilley LP, Oyama MA, Sleeper MM, eds., Manual of Canine and Feline Cardiology, 5th ed. St. Louis, MO: Saunders Elsevier, 2015 (in press).

Thawley JT, Drobatz KJ. Cardiopulmonary Arrest and Resuscitation. In: Smith FWK, Tilley LP, Oyama MA, Sleeper MM, eds., Manual of Canine and Feline Cardiology, 5th ed. St. Louis, MO: Saunders Elsevier, 2015 (in press).

Waldrop JE, Rozanski EA, Swanke ED, et al. Causes of cardiopulmonary arrest, resuscitation management, and functional outcome in dogs and cats surviving cardiopulmonary arrest. J Vet Emerg Crit Care 2004, 14:22–29.