Cardiac CT (an approach)

Cardiac CT can be a more or less frequent examination faced in daily practice also depending on the institution and the CT scanner technology available. With technological advances and improved dose reduction techniques in the last decade, cardiac CT has become increasingly popular.

What is presented below is a “basic approach” for how to organize findings within a radiological report of a cardiac CT without claim for completeness. This does not cover all facets and the workup of every clinical question and every cardiac problem that might be investigated.

Recommendations, given in the Coronary Artery Disease - Reporting and Data System (CAD-RADS) document, created and published in 2016 as a collaborative effort by the Society for Cardiovascular Computed Tomography (SCCT), American College of Radiology (ACR), and North American Society for Cardiovascular Imaging (NASCI) has been taken into consideration by this approach.

Indications 

Similar to other organ-specific examinations it is important to understand that depending on the indication the acquisition protocol can vary but will include a coronary CTA in most circumstances.

Typical indications of cardiac CT include evaluation of the following:

• coronary anomalies 
• preoperative assessment in the setting of non-coronary cardiac surgery
• coronary artery disease (in patients with low to intermediate pretest probability)
  • stable angina
  • acute coronary syndrome without ECG changes and negative troponin
  • surgical or interventional planning of chronic coronary occlusions
  • visualization of aortocoronary bypass grafts in symptomatic individuals
  • coronary artery calcium quantification
• visualization of cardiac veins
• visualization of pulmonary veins
• aortic disease
• ascending aortic/aortic root aneurysm
  • aortic dissection (Stanford A)
  • aortic valve disease
• preprocedural planning and postprocedural follow-up of structural heart disease
  • transcatheter aortic valve implantation
• imaging of cardioembolic disease
• congenital heart disease

Systematic review

The most common indication of cardiac CT consists of the assessment of the coronary arteries and thus a systematic evaluation should be included in every examination even if the respective clinical question for the cardiac CT is different.

A systematic review is essential and should comprise a meticulous inspection of the cardiac chambers, left ventricular outflow tract and coronary arteries including origin, course and variant anatomy as well as the cardiac veins on thin slice axial and multiplanar reformations, if possible also curved reformations.

Morphology

Visual assessment

The visual morphological assessment includes the following ^1-8:

• cardiac situs, position, cardiac chambers and connections 
• congenital anomalies (e.g. atrial and ventricular septal defects)
• cardiac chamber morphology
  • cardiac tumors
  • myocardial crypts, left ventricular diverticulum
  • myocardial infarction/left ventricular aneurysm/left ventricular pseudoaneurysm
• coronary artery morphology
  • coronary dominance
  • other variant anatomy (shepherd crook)
• coronary anomalies
  • absent or hypoplastic coronary artery
  • anomalous coronary ostium, ectopic origin, split origins, single coronary artery
  • anomalous course 
    • right coronary artery: interarterial, subpulmonic, intraseptal, intra-atrial, retroaortic
    • left coronary artery: interarterial, prepulmonic
  • anomalous posterior descending artery (PDA) from the left anterior descending artery (LAD)
  • myocardial bridging
  • coronary arteriovenous fistula, coronary cameral fistula
• coronary artery disease
  • stenosis grading in vessels >1.5 mm in diameter
    • based on luminal diameter stenosis (SCCT classification)
    • none, minimal, mild, moderate, severe, occlusion
    • location based on the AHA 15 segment model ²
  • plaque morphology
    • calcified
    • vulnerable or high-risk plaque
  • coronary artery stents
  • non-diagnostic segments
• additional coronary findings
  • coronary artery aneurysm
  • diffuse or partial arterial mural thickening
  • coronary pseudotumor formation
• cardiac veins
  • stenosis/occlusion
  • anomaly
• aortic root and ascending aorta
  • aortic aneurysm
  • acute aortic syndrome (e.g. Stanford A aortic dissection)
  • mycotic aneurysms, aortic root abscess
  • aortic atheroma/aortic plaques
• valvular heart disease
  • cuspidity
  • valvular and subvalvular calcifications (absent, mild, moderate, severe)
  • valvular vegetations
  • mitral annular calcification
• other cardiac findings
• pericardial disease
  • pericardial effusion, pericardial thickening, pericardial calcification
• extracardiac findings (adjacent mediastinal and pulmonary structures)

Quantitative assessment

Quantitative measurements usually depend on and are tailored to the clinical question. They can include the following measurements ^6,7:

• left and right ventricular size including diameter
• atrial chamber size
• coronary arteries
  • coronary artery calcium quantification
  • semiautomatic stenosis quantification
• aortic root (at least systolic phase)
  • aortic root/sinus dimensions (cross-sectional area, circumference, derived diameters)
  • annulus dimensions (cross-sectional area, circumference, derived diameters)
  • height of coronary ostia
  • determination of fluoroscopic viewing angles
• aortic valve
  • aortic valve calcification (in patients with a discordant result on echocardiography)
  • aortic valve area (AVA), regurgitant orifice area (ROA)
• left atrial appendage ostium

Cardiac function

A left ventricular functional analysis can be only conducted on a retrospective gated cardiac CT and is more an optional part of the analysis:

• contraction pattern: synchronous/dyssynchronous

Quantitative assessment

A quantitative assessment and depending on the clinical question may include the following:

• end-diastolic diameter 
• end-diastolic volume index (EDVI) [mL/m²]
• end-systolic volume index (ESVI) [mL/m²]
• stroke volume index (SVI) [mL/m²]
• ejection fraction (EF) [%]
• left ventricular mass index [g/m²]*
• regional wall motion abnormalities: localization according to the 17 segment model

Cardiac perfusion

A myocardial perfusion analysis can be only conducted after a respective acquisition preferably on a scanner with a wide detector row coverage during pharmacological stress hyperemia similar to SPECT/PET or MRI.  

A quantitative myocardial attenuation analysis can then be performed in a semiautomatic fashion and depicted as perfusion maps and correlated to previously detected coronary lesions ⁷.

Common pathology

• coronary artery disease
• coronary anomalies
  • coronary arteriovenous fistula, coronary cameral fistula
• ischemic heart disease/myocardial infarction
  • cardiac vein pathology (cardiac vein stenosis or occlusion)
  • pulmonary vein pathology (pulmonary vein stenosis or occlusion)
• valvular heart disease
• cardiac tumors or cardiac thrombi
• pericardial disease
  • pericardial effusion/pericarditis
  • constrictive pericarditis
  • pericardial tumors/pericardial cyst
• congenital heart disease
  • atrial or ventricular septal defects
  • aortic coarctation
  • tetralogy of Fallot
  • transposition of the great arteries
  • partial anomalous pulmonary venous return
  • Ebstein anomaly
  • single ventricle morphology
• heart transplantation
  • transplant rejection
  • coronary vasculopathy
• and many more….

See also

• cardiac CT