Porter Health

Understanding CAC Score and CCTA: Advanced Heart Imaging

A Patient's Guide to Coronary Artery Calcium Scoring and CT Angiography

What Are These Tests?

CAC score and CCTA are advanced CT scans that look inside your heart arteries to detect coronary artery disease before symptoms appear. These tests help you and your doctor understand your true heart attack risk and guide treatment decisions.

Two Types of Heart CT Scans:

CAC Score (Coronary Artery Calcium Scoring)

What it measures: Amount of calcium (hardened plaque) in coronary arteries

Key features: Quick (5 minutes), no IV contrast, low radiation

CCTA (Coronary CT Angiography)

What it measures: Detailed view of all plaque types and blockage severity

Key features: More detailed (15-20 minutes), requires IV contrast dye

Why These Tests Matter:

See the invisible: Detect plaque buildup years before symptoms
Refine risk: Traditional calculators (PREVENT, Framingham) predict population risk - these tests show YOUR arteries
Guide treatment: Determine if you need aggressive therapy (statins, aspirin, lifestyle changes)
Motivate change: Seeing plaque in your arteries is powerful motivation to act

CAC Score (Coronary Artery Calcium Scoring)

What Is CAC Scoring?

A CAC score measures the amount of calcium in your coronary arteries using a special CT scan (computed tomography). Calcium in arteries = atherosclerosis (plaque buildup). More calcium = more plaque = higher heart attack risk.

How the Test Works:

You lie on CT scanner table
Electrodes attached to chest (to synchronize scan with heartbeat)
Hold your breath for 10 seconds while scanner takes images
No IV, no contrast dye, no injections - completely non-invasive
Entire scan takes 5-10 minutes
Computer calculates calcium score (Agatston score)

Interpreting Your CAC Score:

CAC Score = 0

EXCELLENT

No detectable plaque. Very low risk of heart attack in next 5-10 years.

Note: Score of 0 doesn't mean zero risk - you can still have soft (non-calcified) plaque not visible on CAC

CAC Score 1-99

MILD PLAQUE

Mild plaque buildup. Increased heart attack risk. Time to optimize lifestyle and consider statin.

1-10: Very minimal plaque
11-100: Mild plaque, moderate risk

CAC Score 100-399

MODERATE PLAQUE

Moderate to moderately high plaque burden. Clear evidence of coronary disease.

Action: High-intensity statin, aspirin (if no bleeding risk), aggressive lifestyle changes

CAC Score ≥400

SEVERE PLAQUE

Extensive plaque burden. Very high risk of heart attack. May have severe blockages.

Action: Cardiology evaluation, stress test or CCTA, maximum medical therapy, consider advanced imaging

Percentile Rankings (Age/Sex Adjusted):

Your CAC score is also compared to people your age and sex:

<25th percentile: Below average calcium for your age/sex - good news!
25-75th percentile: Average calcium for your age/sex
75-90th percentile: Above average - increased risk
>90th percentile: Much higher than peers - high risk, aggressive treatment needed

Example: 55-year-old man with CAC = 120 is 75th percentile (higher than 75% of men his age)

CCTA (Coronary CT Angiography)

What Is CCTA?

CCTA is a more detailed CT scan that uses IV contrast dye to create 3D images of your coronary arteries. It shows ALL types of plaque (calcified and non-calcified), measures blockage severity, and can rule out significant coronary artery disease.

How the Test Works:

IV line placed in arm
May receive beta blocker to slow heart rate (<60 bpm for best images)
Nitroglycerin spray under tongue to dilate coronary arteries
Lie on CT scanner, electrodes attached
Contrast dye injected through IV (warm sensation)
Hold breath for 5-10 seconds while scanner takes detailed images
Entire procedure takes 15-20 minutes

What CCTA Shows (Beyond CAC Score):

Plaque Composition

Soft, calcified, or mixed plaque

Stenosis Severity

Percentage of artery narrowing (0-100%)

Plaque Location

Which arteries affected (LAD, RCA, LCx)

High-Risk Features

Vulnerable plaque, positive remodeling

Coronary Anomalies

Abnormal artery origins or course

Bypass Graft Patency

If you've had CABG surgery

CAD-RADS Reporting System:

CCTA results use the CAD-RADS (Coronary Artery Disease - Reporting and Data System) score:

CAD-RADS 0

(Zero)

No plaque, no stenosis - normal arteries

CAD-RADS 1

(Minimal)

1-24% stenosis - mild plaque, very low risk

CAD-RADS 2

(Mild)

25-49% stenosis - non-obstructive disease, medical therapy

CAD-RADS 3

(Moderate)

50-69% stenosis - may need stress test or FFR-CT

CAD-RADS 4

(Severe)

70-99% stenosis - likely needs catheterization/stent

CAD-RADS 5

(Occlusion)

100% blocked - total occlusion, needs intervention

Special CCTA Analysis: FFR-CT

Fractional Flow Reserve CT (FFR-CT): Advanced computer analysis of CCTA images that predicts if a blockage is causing reduced blood flow (ischemia). Helps avoid unnecessary cardiac catheterization.

FFR-CT <0.80 = Blockage is causing ischemia → May need stent. FFR-CT >0.80 = Blockage not limiting flow → Medical therapy OK.

CAC Score vs. CCTA: Which Test Do You Need?

Feature	CAC Score	CCTA
What it shows	Calcified plaque only	All plaque types + stenosis %
IV contrast needed?	No	Yes (iodinated contrast)
Scan time	5-10 minutes	15-20 minutes
Radiation dose	Low (1-2 mSv)	Moderate (3-5 mSv)
Cost (typical)	$100-$400	$500-$1,500
Insurance coverage	Often not covered (screening)	Covered for chest pain/symptoms
Best for	Risk stratification, screening	Chest pain, rule out CAD
Limitations	Misses soft plaque	Contrast allergy, kidney disease

Which Test Is Right for You?

Consider CAC Score if:

Intermediate risk (10-year ASCVD risk 5-20%) and unsure about statin
Family history of early heart disease
Want baseline measurement of plaque burden
No symptoms, screening purposes

Consider CCTA if:

Chest pain or other cardiac symptoms
CAC score 100-400 and want more detail
Abnormal stress test but no clear next step
Want to rule out significant coronary disease

Who Should Get CAC Scoring or CCTA?

2024 AHA/ACC Guidelines: CAC Score Recommended For:

Intermediate risk adults (10-year ASCVD risk 5-20%) uncertain about statin therapy
Family history of premature coronary disease (male <55, female <65)
Borderline risk (10-year ASCVD 5-7.5%) with risk enhancers (metabolic syndrome, chronic kidney disease, inflammatory disease)
Low to intermediate risk adults age 40-75 considering preventive therapy

CCTA Recommended For:

New chest pain or chest discomfort (low to intermediate risk)
Inconclusive stress test results
Young patients (<50) with chest pain and low pre-test probability
CAC score 100-400 and want to know stenosis severity
Rule out CAD before non-cardiac surgery

Do NOT Get CCTA If:

Severe kidney disease (eGFR <30) - contrast can worsen kidney function
Iodine contrast allergy (severe reaction)
Irregular heart rhythm (atrial fibrillation) - images too blurry
Very high heart rate (>100 bpm) that can't be controlled
Pregnancy - radiation exposure to fetus
Already know you have severe CAD - catheterization more appropriate

What Happens After Your Test: Treatment Implications

CAC Score = 0

Statin: Generally not needed (unless diabetes or very high LDL)
Aspirin: Not recommended for primary prevention
Lifestyle: Continue heart-healthy habits
Repeat CAC: Consider in 5-10 years

CAC Score 1-99

Statin: Strongly consider, especially if CAC >10 or risk enhancers present
Aspirin: Discuss with doctor (if low bleeding risk)
Lifestyle: Intensive lifestyle changes (diet, exercise, weight loss)
Repeat CAC: Consider in 3-5 years

CAC Score 100-399

Statin: High-intensity statin recommended (atorvastatin 40-80mg)
Aspirin: Consider (if no contraindications)
BP control: Target <130/80 mmHg
Lifestyle: Aggressive risk factor modification
Consider CCTA or stress test: To assess stenosis severity

CAC Score ≥400

Statin: High-intensity statin MANDATORY, target LDL <70 mg/dL
Aspirin: Strongly recommended (unless bleeding risk)
Cardiology referral: See cardiologist
Further testing: Stress test or CCTA to assess for severe blockages
Maximum medical therapy: Aggressive risk factor control

CCTA Results and Next Steps:

CAD-RADS 0-1: Low risk, lifestyle modifications, reassess in 3-5 years
CAD-RADS 2: Non-obstructive CAD, statin + aspirin, lifestyle changes
CAD-RADS 3: Moderate stenosis, consider stress test or FFR-CT
CAD-RADS 4-5: Severe stenosis, likely need cardiac catheterization ± stent

Limitations and Considerations

CAC Misses Soft Plaque

CAC score of 0 doesn't guarantee no plaque - you can have soft (non-calcified) plaque that's not visible. Young patients with acute MI often have CAC = 0.

Radiation Exposure

Both tests use ionizing radiation (1-5 mSv). Risk is low but cumulative. Not recommended for screening in young adults (<40) or frequent repeat scans.

CCTA Image Quality

Requires slow, regular heart rate (<60-70 bpm). Atrial fibrillation, obesity, or inability to hold breath can result in poor image quality.

Contrast Reactions

CCTA contrast can cause allergic reaction (rare), kidney damage (if pre-existing kidney disease), or thyroid dysfunction.

Overdiagnosis Risk

CCTA may find mild plaque that would never cause problems, leading to anxiety or unnecessary treatment (medicalization).

Not a Functional Test

CAC and CCTA show anatomy (plaque), not function (blood flow). A 50% blockage may or may not cause ischemia - stress test or FFR-CT needed.

Questions to Keep in Mind as You Discuss CAC/CCTA Testing with Your Porter Health Coach or a Member of Your Medical Care Team

Key Takeaways

CAC score measures calcified plaque; CCTA shows all plaque types + stenosis severity

CAC score = 0 is excellent news, but doesn't rule out soft plaque (especially in young patients)

CAC score ≥100 = strong indication for statin therapy and aggressive risk reduction

CCTA can rule out significant CAD and avoid unnecessary catheterization

CAD-RADS 0-2 = medical therapy; CAD-RADS 4-5 = likely needs catheterization

Best for intermediate risk patients (5-20%) uncertain about preventive therapy

CCTA requires IV contrast - not suitable for severe kidney disease or contrast allergy

Results guide treatment: CAC >100 or CCTA stenosis >50% → statin + aspirin + lifestyle

References:

Based on 2024 AHA/ACC Guidelines on the Management of Blood Cholesterol, 2021 ACC/AHA Chest Pain Guidelines, and Society of Cardiovascular Computed Tomography (SCCT) Guidelines. This guide translates clinical guidelines into patient-friendly language.

Hecht H, et al. 2016 SCCT/STR Guidelines for Coronary Artery Calcium Scoring. J Cardiovasc Comput Tomogr. 2017;11(1):74-84. | Cury RC, et al. 2022 CAD-RADS 2.0. JACC Cardiovasc Imaging. 2022;15(11):1974-2001.