What is the correct placement for an anterior-posterior (AP) pad with a lateral pad anterior in defibrillation and cardioversion procedures?

Anterior-Posterior Pad Placement with Lateral Pad Anterior for Defibrillation

For anterior-posterior (AP) pad placement with a lateral pad anterior, the anterior pad should be placed to the left of the sternum (anterior position) while the posterior pad should be positioned between the scapulae behind the heart (posterior position), ensuring both pads have direct skin contact to maximize defibrillation effectiveness. 1

Optimal Pad Positioning

Anterior Pad Placement

• Place the anterior pad to the left of the sternum 2, 1
• Ensure the pad is directly against the chest wall 2
• For patients with breasts, place the pad under rather than over breast tissue 2, 1
• For large-breasted individuals, position the pad lateral to or underneath the left breast 2, 1

Posterior Pad Placement

• Position the posterior pad in the infrascapular region behind the heart 1
• Place between the scapulae for optimal positioning 1
• Ensure direct contact with the skin (no clothing in between) 2

Evidence Supporting AP Placement

The AP electrode configuration has demonstrated superior efficacy compared to anterior-lateral placement:

• Higher overall success rates (87% vs 76%) 2, 1
• Lower energy requirements for successful cardioversion 2, 1
• Particularly beneficial when pathology involves both atria (e.g., atrial septal defects or cardiomyopathy) 2, 1

Techniques to Improve Effectiveness

1. Minimize electrical resistance:

   • Use electrolyte-impregnated pads 2, 1
   • Ensure good skin contact with no air gaps 1
   • Consider removing excessive chest hair if necessary 2

2. Optimize current flow:

   • For patients with emphysema, placing the anterior electrode to the left of the sternum reduces the amount of pulmonary tissue between the pad and heart 2, 1
   • Deliver shocks during expiration when possible 2
   • Apply firm pressure to manual paddles if used (reduces transthoracic impedance) 3

3. Pad size considerations:

   • Use pads with a diameter of 8-12 cm 2
   • The American Heart Association recommends a pad size greater than 8 cm 2

Common Pitfalls to Avoid

• Placing pads over breast tissue instead of underneath 2, 1
• Excessive electrode separation, particularly in patients with emphysema 2, 1
• Placing pads directly over implanted devices (maintain at least 8 cm distance) 1
• Poor skin contact that increases impedance 1
• Failing to apply sufficient pressure with manual paddles 3

Special Considerations

• For patients with implanted cardiac devices (pacemakers/ICDs), position pads at least 8 cm away from the device 1
• For patients with high body surface area, higher energy selection may be required due to increased transthoracic impedance 4
• Biphasic waveform shocks are more effective than monophasic shocks and require less energy 2

The evidence strongly supports that proper AP pad placement with the anterior pad positioned to the left of the sternum and the posterior pad between the scapulae provides optimal current flow through the heart for effective defibrillation and cardioversion.