What is ventricular standstill?

Ventricular Standstill

Ventricular standstill is a potentially fatal arrhythmia characterized by the absence of ventricular activity or contraction, resulting in sudden loss of cardiac output and requiring immediate intervention to prevent death. 1

Definition and Mechanism

Ventricular standstill is an electrophysiological phenomenon with two primary mechanisms:

1. Lack of impulse formation in ventricles (absence of idioventricular automaticity)
2. Failure of impulse transmission to ventricles (conduction disturbance) 1, 2

On ECG, ventricular standstill appears as:

• Visible P waves (atrial activity)
• Complete absence of QRS complexes (no ventricular activity)
• No effective cardiac output during the episode 2

Clinical Presentation

Ventricular standstill typically manifests with:

• Sudden loss of consciousness/syncope (if prolonged)
• Signs of cardiac arrest (unresponsiveness, absence of pulse)
• Rarely may be asymptomatic in brief episodes 3

The condition is immediately life-threatening as it represents a form of cardiac arrest with no effective cardiac output 4.

Causes and Risk Factors

Common causes include:

• Severe bradyarrhythmias progressing to complete heart block
• Profound vagal tone 3
• Electrolyte disturbances (particularly hypokalemia) 5
• Drug toxicity (especially digoxin) 4
• Post-cardiac surgery (particularly congenital heart disease repair) 2
• Severe myocardial ischemia or infarction 4
• Conduction system disease

Diagnosis

Diagnosis is made by:

• ECG showing P waves with absence of QRS complexes
• Clinical presentation of sudden hemodynamic collapse
• Cardiac monitoring during the event

Management

Ventricular standstill requires immediate treatment as a cardiac arrest:

1. Immediate CPR and ACLS protocols should be initiated 4

2. Transcutaneous pacing should be started immediately if available 4

3. Treat underlying causes:

   • Correct electrolyte abnormalities (particularly potassium)
   • Discontinue offending medications
   • Administer digoxin-specific Fab antibodies if digoxin toxicity is suspected 4
   • Administer atropine for vagally-mediated cases

4. Definitive treatment:

   • Temporary transvenous pacing for acute management
   • Permanent pacemaker implantation for recurrent or persistent cases 3

Special Considerations

• Digoxin toxicity: Ventricular standstill can occur with severe digoxin overdose, which may also present with hyperkalemia. Treatment includes digoxin-specific Fab antibodies for severe intoxication 4.

• QT-prolonging medications: Medications that prolong QT interval can precipitate torsades de pointes and potentially ventricular standstill. Temporary pacing is highly effective in managing recurrent episodes 4.

• Fist pacing: In emergency situations without immediate access to defibrillation or pacing equipment, fist pacing (rhythmic thumps to the precordium) has been reported as a temporizing measure, though with very limited evidence of effectiveness 4.

Prognosis

Without immediate intervention, ventricular standstill is fatal. Survival depends on:

• Rapid recognition and treatment
• Addressing underlying causes
• Timely implementation of pacing
• Prevention of recurrence through definitive treatment of the underlying condition

Permanent pacemaker implantation is typically required for patients with recurrent episodes or persistent conduction system disease 3.