Ventricular Fibrillation

Question 1

define ventricular fibrillation?

Answer 1

an irregular broad-complex tachycardia that can cause cardiac arrest and sudden cardiac death

MEDICAL EMERGENCY

Question 2

briefly outline the aetiology of ventricular fibrillation?

Answer 2

ventricular fibres contract randomly causing complete cardiac failure of ventricular function

most cases occur in patients with underlying heart disease

Question 3

what are the risk factors for ventricular fibrillation?

Answer 3

• Coronary artery disease – most common
• AF
• Hypoxia
• Ischaemia
• Pre-excitation syndrome
• Cardiomyopathy
• Drugs
• Electrolyte imbalance

Question 4

summarise the epidemiology of ventricular fibrillation?

Answer 4

• The MOST COMMON arrhythmia identified in cardiac arrest patients

Incidence of VF parallels the incidence of ischaemic heart disease

Question 5

what is the history of ventricular fibrillation?

Answer 5

chest pain

fatigue

palpitations

Question 6

what pre-existing conditions can cause ventricular fibrillation?

Answer 6

Coronary artery disease

Cardiomyopathy

Valvular heart disease

Long QT syndrome

Wolf- Parkinson-white syndrome

Brugada syndrome- genetic disorder where electrical activity of the heart is abnormal

Question 7

what drugs cause long QT syndrome?

Answer 7

Amiodarone

TCAs

Methadone

Chloroquine

Erythromycin

Haloperidol

Odanestron

Question 8

what are the causes of long QT syndrome?

Answer 8

abnormal ventricular repolarisation

congenital ( mutations in potassium channels)

FH of sudden death- NEED TO ASK-> can lead to torsade de pointes and so sudden collapse/ death

low K+/Mg2+

acute MI

Myocarditis

Hypothermia

subarachnoid haemorrhage

Drugs

Romano- ward syndrome

Question 9

what are the appropriate investigations for ventricular fibrillation?

Answer 9

• ECG: chaotic irregular deflections of varying amplitude, no identifiable P waves/QRS complexes/T waves
• Cardiac enzymes (e.g. troponins) - check for recent ischaemic event
• Electrolytes - derangement can cause arrhythmias, including VF
• Drug levels and toxicology screen - anti-arrhythmics can (ironically) cause arrhythmia, as can various recreational drugs (e.g. cocaine)

• TFTs - hyperthyroidism can cause tachyarrhythmias
Coronary angiography - if patient survives VF, to check the integrity of coronary arteries

Question 10

outline a management plan for ventricular fibrillation ?

Answer 10

• VF requires urgent defibrillation and cardioversion -> non-synchronised DC shock (high energy shock anywhere in the cycle)
• Patients who survive need full assessment of left ventricular function, myocardial perfusion and electrophysiological stability
• Most survivors will need an implantable cardioverter defibrillator (ICD)
• Empirical beta-blockers

• Some patients may be treated with radiofrequency ablation (RFA)
medical procedure in which part of the electrical conduction system of the heart is ablated using the heat generated from medium frequency alternating current (in the range of 350–500 kHz).

Question 11

what are the complications of ventricular fibrillation?

Answer 11

• Ischaemic brain injury due to loss of cardiac output
• Myocardial injury
• Post-defibrillation arrhythmias
• Aspiration pneumonia
• Skin burns (due to defib)
• Death

Question 12

summarise the prognosis for patients with VF?

Answer 12

• Depends on the time between onset of VF and medical intervention
• Early defibrillation is essential (ideally within 4-6 mins)

Anoxic encephalopathy is a major outcome of VF