The 17-Segment Model & Coronary Territories
The standardized LV segmentation and its mapping to coronary arteries
Quick Answer
The 17-segment model is the standardized division of the left ventricle used across cardiac imaging (SPECT/PET MPI, echo, CMR) so that findings are described consistently and mapped to coronary territories (LAD, LCx, RCA). It divides the LV into basal (6), mid (6), apical (4), and the apical cap (1) = 17 segments, displayed as a bull's-eye (polar) map. Naming the coronary territory of a defect is what makes a perfusion report clinically actionable.
Why a Standard Model
A shared segmentation lets perfusion, wall-motion, and viability findings be compared across modalities and over time, feeds the summed-score quantification (SSS/SRS/SDS), and translates a defect location into the likely culprit artery — the information a cardiologist needs for revascularization planning.
The 17 Segments
| Ring | Segments | Count |
|---|---|---|
| Basal | anterior, anteroseptal, inferoseptal, inferior, inferolateral, anterolateral | 6 (1–6) |
| Mid | anterior, anteroseptal, inferoseptal, inferior, inferolateral, anterolateral | 6 (7–12) |
| Apical | anterior, septal, inferior, lateral | 4 (13–16) |
| Apex | apical cap | 1 (17) |
(The older 20-segment model used a maximum score of 80; the 17-segment maximum is 17 × 4 = 68.)
Coronary-Territory Assignment
| Territory | Typical segments |
|---|---|
| LAD | anterior and anteroseptal walls + apex (1, 2, 7, 8, 13, 14, 17) |
| LCx | lateral wall (5, 6, 11, 12, 16) |
| RCA | inferior wall + basal/mid inferoseptum (3, 4, 9, 10, 15) |
Territory boundaries vary with coronary dominance and individual anatomy — the apex (17) and apical segments in particular have variable supply — so multivessel patterns and apical involvement should be described rather than force-fit to a single artery.
Where It's Used
- Perfusion scoring: each segment scored 0–4 at stress/rest → SSS, SRS, SDS and % myocardium (see MPI interpretation & grading).
- Wall motion / thickening: gated SPECT/PET, echo, CMR.
- Viability: perfusion–metabolism mismatch mapped segment by segment.
- Bull's-eye (polar) maps: compress the 3D distribution into one comparable display.
Common Pitfalls
- Force-fitting an apical or boundary defect to a single artery despite variable supply/dominance.
- Confusing the 17-segment (max 68) with the older 20-segment (max 80) scoring.
- Mislabeling walls (anteroseptal vs inferoseptal) — orientation errors change the territory.
Board Pearls
The LV divides into basal (6) + mid (6) + apical (4) + apex (1) = 17 segments, mapped to LAD (anterior/anteroseptal + apex), LCx (lateral), and RCA (inferior + basal/mid inferoseptum). Naming the coronary territory of a defect is what makes a perfusion report actionable.
Each segment is scored 0–4 and summed to SSS/SRS/SDS and % myocardium (17 × 4 = 68 max); the older 20-segment model used a maximum of 80.
Territory boundaries vary with dominance and individual anatomy — the apex (segment 17) and apical segments especially have variable supply — so describe multivessel/apical patterns rather than force-fitting them to one artery. Consistent wall labeling (anteroseptal vs inferoseptal) and the bull's-eye display keep serial and cross-modality comparison valid.
Related Pages
- Protocols: MPI interpretation & grading (SSS/SRS/SDS, TID), MPI SPECT.
- Calculator: summed-score tool.
- Pitfalls: Pearls, pitfalls & normal variants (attenuation vs territory defects).
Figure / Diagram Suggestions
- A 17-segment bull's-eye with segment numbers and wall labels.
- A coronary-territory overlay (LAD/LCx/RCA color map) on the polar plot.
- A 17- vs 20-segment comparison (max 68 vs 80).
Self-Check (Board-Style)
Q1. How many segments are in each ring of the 17-segment model, and what is the maximum summed score?
Answer: Basal 6, mid 6, apical 4, apex 1 = 17; with each scored 0–4, the maximum is 17 × 4 = 68 (the older 20-segment model used 80).
Q2. A perfusion defect involves the anterior wall, anteroseptum, and apex. Which coronary territory?
Answer: LAD (anterior/anteroseptal walls plus the apex).
Q3. Why should apical defects be described rather than assigned to a single artery?
Answer: The apex and apical segments have variable coronary supply (depends on dominance/anatomy), so rigid single-artery assignment can be inaccurate.
Q4. Which walls/segments correspond to the RCA territory?
Answer: The inferior wall and basal/mid inferoseptum (segments 3, 4, 9, 10, 15).
Evidence & sources
https://nuc.med/seventeen-segment-model/ Report an issue