Understanding CT Coronary Calcium Score vs. CT Heart Without Contrast
CT coronary calcium score and "CT heart without contrast" are essentially the same examination when referring to calcium scoring—both are non-contrast CT scans that quantify coronary artery calcification using the Agatston scoring method. 1
Technical Specifications
Both examinations use identical imaging protocols:
- ECG-gated multidetector computed tomography without contrast material 1
- Low radiation exposure (0.37-1.5 mSv) 1
- Calcific lesions defined as CT density >130 Hounsfield units with area >1 mm² 1
- Results reported as Agatston score quantifying total coronary calcium burden 1
Terminology Clarification
The American College of Radiology recommends ordering this study as "CT Coronary Artery Calcium Score" or "Cardiac CT for Calcium Scoring"—these are interchangeable terms for the same procedure. 1 The phrase "CT heart without contrast with coronary CT score" is simply a more descriptive way of stating the same examination.
What This Examination Measures
Coronary calcium scoring quantifies atherosclerotic burden but has critical limitations:
- Definitively establishes presence of atherosclerosis (calcification only occurs in atherosclerotic lesions) 1
- Cannot detect non-calcified or low-attenuation plaque 2
- Provides no detail about anatomical degree of coronary artery stenosis 2
- Poor specificity for diagnosing obstructive coronary artery disease 1
Diagnostic Performance in Intermediate-Risk Patients
In symptomatic patients with intermediate pre-test probability:
- Calcium score of 0 has 95.3% sensitivity and 98.2% negative predictive value for obstructive CAD 3
- However, 1.8% of patients with calcium score 0 still had obstructive CAD on CT angiography 3
- Among patients with zero calcium score, 3.5% had ≥50% stenosis and 1.4% had ≥70% stenosis 1
No patients with calcium score of 0 experienced cardiac events during 26-month follow-up in one study, supporting its excellent negative predictive value. 4
Clinical Applications
The American College of Cardiology/American Heart Association guidelines recommend calcium scoring for:
- Asymptomatic adults aged 40-75 years with intermediate (7.5-20%) or borderline (5-7.5%) 10-year ASCVD risk 2, 1
- Risk stratification when decisions about preventive interventions are uncertain 1
- NOT appropriate for low-risk patients (<5% 10-year risk) 5
Prognostic Value
Cardiovascular risk increases proportionally with calcium scores: 1, 6
- Calcium score 0: 2.1% 3-year MACE rate 6
- Calcium score 1-100: 12.9% 3-year MACE rate 6
- Calcium score 101-400: 16.3% 3-year MACE rate 6
- Calcium score >400: 33.8% 3-year MACE rate 6
Annual event rate for hard cardiac events in patients with calcium score 0 is only 0.027%. 7
When Additional Testing Is Needed
In presence of coronary calcium, CT angiography with contrast provides incremental value:
- Area under ROC curve improves from 0.82 with calcium score alone to 0.93 when adding CT angiography 6
- Patients at intermediate CAD risk without coronary calcium do not need further evaluation with longer and higher-radiation-dose protocols 4
- In presence of coronary calcium, CT angiography is useful to further stratify patients 4
Common Pitfalls
Critical limitations to recognize:
- Calcium scoring should not be used in symptomatic patients as primary diagnostic tool—7-38% of symptomatic patients with calcium score 0 have obstructive CAD 1
- Sensitivity drops to only 82.3% in patients <45 years of age, requiring full CT angiography for safe exclusion of obstructive CAD 3
- Cannot be used as surrogate for angiographic disease detection 1
- Radiation exposure (1.5 mSv) cannot be justified in low-risk patients 5