How can the short‑axis view be used to assess left ventricular ejection fraction and determine the percentage contribution of each coronary artery?

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Short-Axis View Assessment of Ejection Fraction and Coronary Artery Territory Contribution

The short-axis view cannot directly determine the percentage contribution of individual coronary arteries to ejection fraction, but it can assess regional wall motion abnormalities that correspond to specific coronary territories, which indirectly reflects their functional contribution.

Understanding the Relationship Between Short-Axis Views and Coronary Territories

The short-axis view provides a cross-sectional perspective of the left ventricle at different levels (base, mid-papillary, and apex), allowing you to evaluate regional wall motion in segments supplied by different coronary arteries 1. However, ejection fraction itself is a global measure of left ventricular systolic function—it represents the percentage of blood ejected from the entire ventricle, not individual arterial contributions.

How to Use Short-Axis Views for Regional Assessment

Standard Segmentation Model

The left ventricle is divided into segments at three short-axis levels 1:

  • Basal level: 6 segments
  • Mid-papillary level: 6 segments
  • Apical level: 4 segments

Coronary Territory Distribution in Short-Axis View

Each segment corresponds to a coronary artery territory:

  • LAD (Left Anterior Descending): Anterior and anteroseptal segments, plus the apex
  • LCx (Left Circumflex): Lateral and posterolateral segments
  • RCA (Right Coronary Artery): Inferior and inferoseptal segments

Calculating Ejection Fraction from Short-Axis Views

For accurate EF calculation, use the Simpson's method with short-axis images 1. The formula is:

LVEF = ([EDV - ESV] / EDV) × 100

Where:

  • EDV = End-diastolic volume
  • ESV = End-systolic volume

The short-axis method involves planimetry of endocardial borders at multiple levels, then summing the volumes 2, 3. Research demonstrates that short-axis-based calculations show better correlation with reference standards compared to long-axis methods 2.

Assessing Regional Contribution Through Wall Motion Scoring

To estimate how much each coronary territory contributes to overall function:

Wall Motion Score Approach

Assign scores to each segment based on contractility 4:

  • Normal = 60% (score 1)
  • Hypokinetic = 40% (score 2)
  • Akinetic = 10% (score 3)
  • Dyskinetic = 0% (score 4)

A simplified approach using mid-parasternal short-axis (PSAX-MID) combined with apical 4-chamber view provides excellent correlation (r² = 0.90) with standard 16-segment analysis 4. This method averages segmental EF based on contractility to derive global LVEF.

Calculating Territory-Specific Contribution

  1. Identify which segments are abnormal in the short-axis views
  2. Map these to coronary territories using the standard distribution
  3. Calculate the proportion of dysfunctional segments per territory
  4. Estimate relative contribution by comparing normal vs. abnormal segments in each territory

Important Clinical Caveats

Limitations of Short-Axis Assessment

  • Geometric assumptions: Short-axis methods assume the LV is a prolate ellipsoid, which becomes inaccurate with dilated or asymmetrically remodeled ventricles 1
  • Measurement errors are cubed: Since linear dimensions are raised to the power of 3, small errors significantly impact calculated volumes 1
  • Requires good image quality: Proper orientation without oblique planes is essential 1

Common Pitfalls to Avoid

  • Off-axis imaging: Beam orientation must be perpendicular to the LV long axis 1
  • Papillary muscle inclusion: Consider papillary muscles as part of the LV cavity, not myocardium 1
  • Single-level assessment: Using only one short-axis level underestimates regional dysfunction—always evaluate base, mid, and apex 4

Practical Clinical Algorithm

  1. Obtain three short-axis levels (basal, mid-papillary, apical)
  2. Trace endocardial borders at end-diastole and end-systole
  3. Calculate global LVEF using Simpson's method
  4. Assess wall motion in each segment at all three levels
  5. Map abnormal segments to coronary territories
  6. Quantify the number of abnormal segments per territory to estimate relative contribution

The key insight: You cannot directly calculate "percentage contribution" of each artery to EF, but you can determine which territories have reduced function and by how much, giving you a functional map of coronary perfusion territories 1, 4.

References

3
Research

Comparison of long and short axis quantification of left ventricular volume parameters by cardiovascular magnetic resonance, with ex-vivo validation.

Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance, 2011

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.