Ventricular Fibrillation & Sudden Death

Essentials of Diagnosis

• Most patients with sudden cardiac death have underlying coronary heart disease

• In the absence of reversible cause, implantable cardioverter defibrillator (ICD) is recommended

General Considerations

• Sudden cardiac arrest: defined as the successful resuscitation of ventricular fibrillation, either spontaneously or via intervention (defibrillation)

• Sudden cardiac death: defined as unexpected nontraumatic death in clinically well or stable patients who die within 1 hour after onset of symptoms; the causative rhythm in most cases is ventricular fibrillation

• A disproportionate number of sudden deaths occur in the early morning hours; this suggests that there is a strong interplay with the autonomic nervous system

• Prompt evaluation to exclude reversible causes of sudden cardiac arrest should begin immediately following resuscitation

• Underlying coronary heart disease

  • Cause of sudden cardiac death in approximately 70% of cases

  • May be the initial manifestation of sudden cardiac death in up to 20% of patients

• Initiating arrhythmia in most patients is unknown, but is presumed to be

  • Sustained monomorphic ventricular tachycardia

  • Polymorphic ventricular tachycardia

  • Primary ventricular fibrillation (especially in the setting of acute ischemia)

• Complete heart block and sinus node arrest may also cause sudden death

• Other forms of structural heart disease can predispose to sudden cardiac death including

  • Idiopathic cardiomyopathy

  • Hypertrophic cardiomyopathy

  • Valvular heart disease (aortic stenosis, pulmonic stenosis)

  • Congenital heart disease

  • Arrhythmogenic right ventricular cardiomyopathy

  • Myocarditis

• Five to ten percent of cases of sudden cardiac death are primarily arrhythmic and occur in the absence of structural heart disease; etiologies include

  • Long QT syndrome

  • Brugada syndrome

  • Catecholaminergic polymorphic ventricular tachycardia

  • Wolff-Parkinson-White syndrome

• Laboratory testing

  • Should be performed to exclude severe electrolyte abnormalities (particularly hypokalemia and hypomagnesemia), acidosis, and to evaluate cardiac biomarkers

  • Abnormalities may be secondary to resuscitation and not causative of the event; use caution in attributing cardiac arrest solely to an electrolyte disturbance

• A 12-lead ECG should be performed to evaluate for ongoing ischemia or conduction system disease

• Echocardiography should be done to evaluate ventricular function

• Coronary arteriography should be performed to exclude coronary disease as the underlying cause, since revascularization may prevent recurrence

• Intervention is required unless ventricular fibrillation

  • Occurs shortly after myocardial infarction

  • Is associated with ischemia

  • Is seen with a correctable process (eg, electrolyte abnormality or medication toxicity)

• Hypothermia protocol should be initiated rapidly and continued for 24–36 hours after cardiac arrest

• ICD is generally indicated in patients who survive sudden cardiac arrest

• Sudden cardiac arrest in the setting of acute ischemia or infarct should be managed with prompt coronary revascularization

• Wearable defibrillator vest

  • Alternative to implantation of a prophylactic ICD in patients early after myocardial infarction

  • May be used until recovery of ventricular function can be assessed by echocardiogram 6–12 weeks following myocardial infarction or coronary intervention

Prognosis

• Survivors of cardiac arrest have improved long-term outcomes if a hypothermia protocol is rapidly initiated and continued for 24–36 hours after cardiac arrest

When to Refer

• All survivors of sudden cardiac arrest should be referred to a cardiologist or cardiac electrophysiologist