ICD vs AICD: There is No Clinical Difference
ICD (Implantable Cardioverter-Defibrillator) and AICD (Automatic Implantable Cardioverter-Defibrillator) are the same device—these terms are used interchangeably in clinical practice. The term "AICD" was originally a brand name from the early devices but has become synonymous with ICD in general medical terminology 1, 2.
Understanding the Terminology
The confusion arises from historical naming conventions:
- ICD is the current standard medical terminology used in contemporary guidelines and literature
- AICD was the original brand name when these devices were first implanted in humans in 1980 2
- Both terms refer to devices that automatically detect and treat life-threatening ventricular arrhythmias (ventricular tachycardia and ventricular fibrillation) through pacing or shock therapy
The 2017 AHA/ACC/HRS guidelines consistently use "ICD" as the standard nomenclature when discussing these devices 3.
What You Actually Need to Know: Types of ICDs
Rather than ICD vs AICD, the clinically relevant distinction is between different types of ICDs:
Transvenous ICD (Standard ICD)
- Leads placed through veins into the heart
- Capabilities:
- Defibrillation for VT/VF
- Bradycardia pacing
- Antitachycardia pacing (painless VT termination)
- Can provide cardiac resynchronization therapy (CRT)
- Complications: Pneumothorax, hemothorax, cardiac tamponade, lead-related infections 3
Subcutaneous ICD (S-ICD)
- Lead placed entirely under the skin, no venous access required
- Capabilities:
- Defibrillation for VT/VF
- Limited post-shock bradycardia pacing only
- Cannot provide: Bradycardia pacing, antitachycardia pacing, or CRT 3
- Advantages: Lower infection risk, avoids vascular complications 3
- Critical limitation: Requires pre-implant ECG screening—not all patients have adequate QRS-T morphology for proper sensing 3
Clinical Decision Algorithm
Use Transvenous ICD when:
- Patient needs bradycardia pacing
- Patient needs CRT
- Patient requires antitachycardia pacing for VT termination 3
Use Subcutaneous ICD when:
- Patient has inadequate vascular access (e.g., ESRD) 3
- High infection risk (prior device infection, diabetes, immunosuppression) 3
- No need for pacing functions
- Patient passes ECG screening for adequate sensing 3
Contraindication for S-ICD: Do not implant if patient needs any form of pacing therapy—this causes harm 3.
Quality of Life Consideration
Both device types deliver painful shocks when awake, negatively impacting QOL 3. However, transvenous ICDs can terminate many VTs painlessly through antitachycardia pacing, while subcutaneous ICDs cannot, potentially resulting in more painful shock experiences 3.