ACHD Anatomic–Physiologic (AP) Classification
Definition
The ACHD Anatomic–Physiologic (AP) classification system assigns every adult with congenital heart disease two independent scores: an anatomic complexity tier (I–III) and a physiological stage (A–D). The combined AP class guides follow-up intensity, procedure location, specialist involvement, and risk counselling.
Key Concepts
Anatomic Complexity Tiers
- Class I (Simple): Secundum ASD, patent ductus arteriosus, VSD, pulmonary stenosis
- Class II (Moderate Complexity): Bicuspid aortic valve, coarctation of the aorta, AVSD, Ebstein anomaly, tetralogy of Fallot, d-TGA after arterial switch, partial/total APVC, vascular ring/sling, subaortic stenosis, supravalvar aortic stenosis
- Class III (Great Complexity): Fontan physiology, CCTGA, d-TGA after atrial switch (Mustard/Senning), d-TGA after Rastelli, truncus arteriosus, double-outlet RV, pulmonary atresia (all forms), single-ventricle anatomy (including HLHS), unrepaired or partially palliated cyanotic CHD
sources/ACHD-AHA-2025 — very high
Physiological Stages
| Stage | Key Features |
|---|---|
| A | No symptoms; no hemodynamic or anatomic sequelae; no sustained arrhythmias; normal exercise capacity; normal pulmonary pressure |
| B | Arrhythmia not requiring new treatment in past 12 months; mild native valve dysfunction or normal prosthetic valve; mild ventricular dysfunction or enlargement; permanent pacemaker/ICD without therapy in past 12 months; trivial shunt |
| C | BNP/NT-proBNP ≥2× ULN; hemodynamically significant shunt; mild–moderate chronic hypoxemia (SpO₂ 86–92%); moderate/greater valve dysfunction; moderate/severe ventricular dysfunction; low-risk PAH; sustained/high-burden tachyarrhythmia in past 12 months requiring treatment |
| D | HF hospitalization in past 12 months; endocarditis in prior year; Eisenmenger syndrome; NYHA III–IV; recurrent hemodynamically significant/refractory arrhythmias; severe hypoxemia (SpO₂ ≤85%); intermediate/high-risk PAH |
| sources/ACHD-AHA-2025 — very high |
Key Rules and Constraints
- Patients with Fontan circulation, systemic RV, or truncus arteriosus cannot be in Stage A — their anatomy precludes "no sequelae" status
- A patient is classified by the highest relevant anatomic or physiological feature
- Physiological stage can improve after successful intervention (e.g., valve replacement) or worsen with new arrhythmia or organ dysfunction
- NT-proBNP ≥2× ULN and endocarditis in past year are new additions to the 2025 classification (not in 2018 version)
sources/ACHD-AHA-2025 — very high
Clinical Utility of AP Class
- AP IA: At least 1 ACHD cardiologist evaluation to develop plan; can be followed by general cardiologist
- AP IB–D, IIA–D, IIIA–D: Managed by or in collaboration with ACHD cardiologist
- AP IC–D, IIB–D, IIIA–D: Noncardiac surgery requires ACHD cardiologist pre/post-procedure and congenital-trained anesthesiologist
- AP IC–D, IIA–D, IIIA–D: Invasive cardiac procedures require ACHD cardiologist involvement pre- and post-procedure
- Higher AP class → worse surgical outcomes, greater maternal/fetal pregnancy complications, higher short- and long-term mortality
sources/ACHD-AHA-2025 — very high
Hemodynamically Significant Shunt (Stage C Definition)
An intracardiac shunt is hemodynamically significant if: evidence of chamber enlargement distal to the shunt AND/OR sustained Qp:Qs ≥1.5
PAH Staging Within AP Classification
- PAH defined as mPAP ≥20 mmHg + PCWP ≤15 mmHg + PVR ≥2 Wood units (right heart catheterization)
- Low-risk PAH = Stage C; Intermediate/high-risk PAH = Stage D (using 3-strata risk score calculator)
Contradictions / Open Questions
- The AP classification is imperfect for short- and long-term mortality risk assessment largely due to population heterogeneity; disease-specific risk scores may be more accurate for individual conditions (e.g., PREVENTION-ACHD for TOF, PACES score)
- Whether thresholds for intervention should be modified based on AP class remains incompletely defined for many lesion types
sources/ACHD-AHA-2025 — very high
Connections
- Related to concepts/Tetralogy-of-Fallot
- Related to concepts/Fontan-Circulation
- Related to concepts/Eisenmenger-Syndrome
- Related to entities/Pulmonary-Hypertension — PAH staging within AP class