When are heart computed tomography (CT) scans indicated?

When Are Heart CT Scans Indicated?

Heart CT scans are primarily indicated for evaluating suspected coronary artery disease in symptomatic patients with chest pain at low-to-intermediate risk, for coronary artery calcium scoring in asymptomatic intermediate-risk patients to guide preventive therapy decisions, and for pre-procedural planning before structural heart interventions.

Coronary CT Angiography (CCTA) Indications

Acute and Chronic Chest Pain

• CCTA is recommended for patients presenting with chest pain who have low-to-intermediate pretest probability of coronary artery disease (CAD) and inconclusive diagnostic assessment 1.
• In non-ST-elevation acute coronary syndromes, CCTA should be considered as an alternative to invasive coronary angiography when initial evaluation is inconclusive (Class IIa, Level A) 1.
• CCTA is appropriate for patients with stable chest pain and intermediate probability (5%-50%) of obstructive CAD 1.
• The high negative predictive value of CCTA makes it particularly useful for excluding obstructive CAD in symptomatic patients 1, 2.

Heart Failure Evaluation

• CCTA can be used to rule out obstructive CAD in patients with heart failure of undetermined etiology who have low-to-intermediate pretest probability 1.
• In patients with reduced left ventricular ejection fraction and low or intermediate pretest CAD probability, CT angiography is recommended 3.
• CCTA is useful when differentiating between ischemic and non-ischemic cardiomyopathy, though cardiac MRI with late gadolinium enhancement has superior diagnostic accuracy for this purpose 1.

Valvular Heart Disease

• CT plays a critical role in pre-procedural planning for transcatheter aortic valve replacement (TAVR), including assessment of aortic root dimensions, coronary ostia heights, and vascular access routes 1.
• CT is indicated for planning transcatheter interventions for structural heart disease beyond the aortic valve 1.
• CCTA can exclude CAD in low-risk patients candidate for valve surgery as an alternative to invasive angiography (Class IIa) 1.
• CT is useful when echocardiographic images are suboptimal for evaluating valve morphology and function 1.

Cardiac Device-Related Infections

• CT can assess larger vegetations in the right atrium, right ventricle, and tricuspid valve, though differentiation between vegetations, thrombi, and tissue ingrowth may be difficult 1.
• CT is helpful for assessing LVAD driveline infection and larger abscesses around LVAD components 1.
• Generator pocket infections may appear as fluid surrounding the device with rim enhancement, though metal artifacts limit diagnostic accuracy 1.

Coronary Artery Calcium (CAC) Scoring Indications

Risk Stratification in Asymptomatic Patients

• CAC scoring receives a Class IIa recommendation for asymptomatic adults aged 40-75 years at intermediate risk (7.5% to <20% 10-year ASCVD risk) when treatment decisions about statin therapy remain uncertain 3.
• CAC scoring is reasonable for selected borderline risk patients (5% to <7.5% 10-year ASCVD risk) with risk-enhancing factors such as family history of premature CHD, persistently elevated LDL-C, metabolic syndrome, chronic kidney disease, or inflammatory diseases 3.
• Low-risk patients with a family history of premature coronary heart disease may benefit from CAC scoring 3.

CAC Score Interpretation and Clinical Action

• A CAC score of 0 indicates excellent prognosis with very low risk (<1% annually) of cardiac death or myocardial infarction, and statin therapy can be withheld with reassessment in 5-10 years 3, 4.
• It is reasonable to initiate statin therapy for patients ≥55 years with CAC score 1-99 3.
• Statin therapy should be initiated for patients with CAC score ≥100 or ≥75th percentile for age and sex 3, 4.
• Patients with CAC >100 should be reclassified to high risk and treated more aggressively 3.

Symptomatic Patients

• In patients with stable chest pain and no known CAD, a zero CAC has high negative predictive value for excluding obstructive CAD and is associated with good medium-term prognosis 1.
• However, a zero CAC does not completely exclude obstructive stenosis in patients with high probability of CAD, as 7-38% of symptomatic patients with CAC = 0 have obstructive disease 5, 3.
• In patients with high CAC scores (≥400), the presence of myocardial ischemia on provocative testing occurred in 48.5% compared to 21.7% in those with scores 1-399 1.

Pericardial Disease

• CT is strongly recommended as second-level testing for diagnostic workup in pericarditis (Class I, Level C) 1.
• CT receives a Class I recommendation for diagnosis of constrictive pericarditis 1.
• CT is useful for depicting abnormal pericardial thickening and defining the extent of pericardial calcification 1.
• CT can assess size, location, and density of pericardial effusion when not fully demonstrated by echocardiography, and is useful for planning before pericardiocentesis 1.

Cardiomyopathies

• CT has a supportive role to cardiac MRI in evaluating hypertrophic cardiomyopathy when echocardiographic windows are inadequate 1.
• CT can provide assessment of ventricular morphology and function, though cardiac MRI is generally preferred for this indication 1.

Important Contraindications and Limitations

When NOT to Use CCTA

• CCTA is explicitly not recommended (Class III) when extensive coronary calcification makes good image quality unlikely 5.
• CCTA should not be used as a screening tool in asymptomatic individuals 3, 4.
• Repeat coronary calcium testing is considered inappropriate 3.
• CCTA is not appropriate for routine follow-up in patients with established CAD or high calcium scores without symptoms 4.
• In high-risk acute coronary syndrome patients with known high calcium scores, CCTA lacks supporting evidence 5.

Alternative Pathways for High Calcium Burden

• When CAC score is >400 and patient is symptomatic, skip CCTA and proceed directly to functional imaging (stress echocardiography, nuclear perfusion, or stress cardiac MRI) or invasive coronary angiography with FFR based on symptom severity 5, 4.
• If CCTA was already performed and shows extensive calcification with uncertain stenosis severity, functional imaging is mandatory before considering revascularization 5.
• Poor image quality and severe calcifications lead to overestimation of stenosis severity even with expert interpretation 5, 4.

Common Pitfalls to Avoid

• Do not order CAC scoring in patients where results would not change management decisions 3.
• CAC scoring is generally not recommended for men <40 years or women <50 years due to low prevalence of detectable calcium and radiation exposure concerns 3.
• A zero CAC score does NOT exclude non-calcified plaque or obstructive coronary disease in symptomatic patients 5, 3.
• Invasive coronary angiography is not recommended solely for risk stratification in asymptomatic patients, regardless of calcium score (Class III) 4.
• The presence of coronary calcification does not indicate plaque stability or instability 4.
• Estimated stenoses between 50-90% by visual inspection on CCTA are not necessarily functionally significant and do not always induce myocardial ischemia 4.