While Coronary CTA is primarily known for delineating the coronaries, advances in software algorithms and multi-detector technology allow for highly accurate, high-resolution functional and morphologic imaging of the cardiac chambers. Cardiac CT can evaluate left and right ventricular function, chamber volumes, and even parameters of diastolic dysfunction.
It is frequently a reliable alternative for functional quantification when echocardiography or cardiac MRI are nondiagnostic or contraindicated (e.g. due to indwelling pacemakers or defibrillators).
1 Image acquisition for functional assessment
To accurately evaluate cardiac function and wall motion, the scan must use a retrospective ECG-gated helical acquisition:
- Unlike prospective gating (which only captures a single snapshot in diastole), retrospective gating acquires data continuously throughout the entire cardiac cycle.
- This permits the reconstruction of multiphasic “cine” datasets at arbitrary time points — crucially capturing both end-diastolic and end-systolic phases required to calculate the ejection fraction.
- A triphasic contrast bolus is often utilized to fully opacify the entire heart and distinctly outline all chamber borders.
See Scan acquisition & gating for the radiation trade-off — retrospective gating delivers the highest dose of any cardiac protocol.
2 Evaluating wall motion
By reviewing the multiphasic cine reconstructions, reading physicians can dynamically assess global and regional ventricular function. Identifying regional wall-motion abnormalities is a key component in diagnosing acute or chronic MI and various cardiomyopathies.
| Category | Description |
|---|---|
| Hypokinesis | Reduced or sluggish myocardial wall thickening and motion. |
| Akinesis | A complete lack of wall motion. |
| Dyskinesis | Paradoxical outward bulging of the myocardial wall during systole — classically seen with true ventricular aneurysms following a transmural infarct. |
Map abnormal segments back to the supplying vessel using the 17-segment model and normal coronary territories.
3 Quantifying chamber volumes & mass
Volume-rendered multiphase CT datasets can accurately quantify:
- End-diastolic volume (EDV)
- End-systolic volume (ESV)
- Myocardial mass
- Global ejection fraction (EF)
CT provides excellent spatial resolution for identifying structural sequelae of heart failure — ventricular dilation (dilated cardiomyopathy) and generalized or asymmetric ventricular hypertrophy.
4 Normal chamber & wall measurements
Standard reference measurements when systematically evaluating chamber sizes and wall thickness:
| Measurement | Normal |
|---|---|
| LV wall thickness (diastole) | < 11 mm |
| LV wall thickness (systole) | < 15 mm |
| LV diastolic diameter | < 55 mm |
| RV wall thickness | < 3 mm (lower-pressure system) |
The “lucky number 40”: the upper limit of normal is 40 mm for the left atrium, the RVOT, and the aortic root (measured at the sinuses of Valsalva).
Thickened LV myocardium suggests left ventricular hypertrophy (e.g. from hypertension), hypertrophic cardiomyopathy, or infiltrative disorders.
5 Limitations of CT functional assessment
CCTA provides exceptional spatial resolution for anatomical detail — but in functional assessment:
- Temporal resolution (≈ 67–165 ms, depending on scanner generation) is inferior to both echocardiography (< 33 ms) and cardiac MRI.
- The retrospective ECG gating required to obtain wall-motion and EF data exposes the patient to higher radiation dose than standard prospectively triggered scans — reserve it for cases where echo/MR are unavailable or nondiagnostic.