Overview
This lecture introduces the cardiovascular imaging modalities used in clinical practice and the strengths and weaknesses that decide which one is chosen. The common modalities are ECG (covered in Physiology and Integrated Cases), chest X-ray (covered in the Gross Anatomy of the Heart lab), echocardiography, cardiac CT and invasive coronary angiography; cardiac MRI is the less common modality. Each is presented as a trade-off across access, cost, spatial resolution, temporal resolution, physiological information and how much non-cardiac anatomy it shows, and the trade-offs are then pulled together in a summary comparison table. Three cases run through the lecture — an acute inferior ST-elevation presentation taken to invasive angiography, a chest pain presentation with equivocal non-invasive testing taken to CT coronary angiography, and a young patient with a very high troponin assessed by cardiac MRI — showing how the choice of test follows the clinical question.
Objectives and scope
- Introduction to the different cardiovascular imaging modalities used in clinical practice.
- Introduction to the strengths and weaknesses of those modalities.
Modalities covered:
- Common: ECG (covered in Physiology and Integrated Cases), chest X-ray (covered in the Gross Anatomy of the Heart lab), echocardiography, cardiac CT, invasive coronary angiography.
- Less common: cardiac MRI.
- Plus strengths and weaknesses, and case presentations.
Chest X-ray
- Advantages: cheap; portable; gives some information about the rest of the thorax.
- Disadvantages: limited spatial resolution; no physiological information.
The case CXR is a frontal radiograph (annotated “Mobile”, “AP Erect”, “85kv 2.5mas 1.8m”, side marker “L”) showing both lung fields and the cardiac silhouette, with ECG monitoring leads overlying the chest and line/tubing at the lower right.
The CXR image carries no diagnostic labels or captions — the slide does not state what the film shows.
Invasive coronary angiography
A procedural, catheter-based test performed in a fluoroscopy suite (cardiac catheter laboratory): operator and staff in lead gowns at a draped patient table with an angiography C-arm, a sterile draped vascular access site with catheter and tubing, and a monitor bank displaying live coronary angiographic images alongside haemodynamic traces.
- Advantages: allows percutaneous therapy to be delivered (emphasised on the slide); high spatial resolution of the coronary arteries; allows advanced assessment of the arteries.
- Disadvantages: invasive (emphasised on the slide); radiation; limited information about non-coronary anatomy.
Case application — right coronary artery occlusion: the angiogram is shown as four fluoroscopic still frames in different projections, alongside photographs of a coronary artery cast/heart model in which an arrow points to the vessel running in the right atrioventricular groove (the right coronary artery), and a specimen pot containing a cross-sectioned artery.
On the angiogram frames the occlusion site is not legible at the rendered resolution, and the model and specimen photographs carry no printed labels — only the slide title identifies the lesion as a right coronary artery occlusion.
Echocardiography
- Advantages: portable; moderate cost; fast; physiological information; real-time imaging.
- Disadvantages: operator dependent; patient dependent.
Echo is performed at the bedside with a hand-held transducer on the chest, the patient monitored with ECG electrodes and the machine alongside showing the live cardiac image.
Parasternal short-axis view
- How it is obtained: transducer placed on the left parasternal chest wall with the patient in the left decubitus position; the scan plane cuts transversely through the ventricles (right atrium, right ventricle and left ventricle indicated on the orientation schematic).
- Two levels are shown:
- Mitral valve level — the mitral valve sits in the centre of the left ventricular cavity.
- Papillary muscle level — the LV cavity with, arranged around it, the interventricular septum (IVS), anterior wall, papillary muscles and inferior wall.
- Each level is shown as a normal image beside an inferior MI image, with arrows on the inferior MI images pointing to the region of the inferior wall. [The slide does not state in words what abnormality to look for, and the small labels in the orientation schematic are only partly legible.]
Apical four-chamber view
- How it is obtained: transducer held at the apex with the pointer directed posteriorly; the scan plane passes through all four chambers, the beam directed from the apex towards the heart.
- Chambers labelled on the normal image: right ventricle (RV) and left ventricle (LV) above, right atrium (RA) and left atrium (LA) below.
- Shown beside a case of severely impaired LV in the same view. [The slide gives no text description of the features that distinguish the severely impaired LV from normal; the chambers are not labelled on that image.]
Transoesophageal echo (TOE)
- Principle: the probe is passed through the mouth and down the oesophagus so the transducer sits directly behind (immediately posterior to) the heart, with the beam directed forwards onto it. [A “LAA” label appears beside the illustration but its leader line cannot be traced to a structure, so the labelled target is not identifiable.]
- Example use: assessment of mitral valve anatomy. The mitral valve is viewed en face from the left atrium (“surgeon’s view”), allowing segment-by-segment assessment:
- Anterior leaflet scallops: A1, A2, A3.
- Posterior leaflet scallops: P1, P2, P3.
- Orientation landmarks: aortic valve (AV) anteriorly, left atrial appendage (LAA) to one side, interatrial septum (IAS) on the opposite side.
- The same en face view is shown with colour Doppler overlaid, showing a large multicoloured turbulent flow signal across the valve area. [The slide does not state in text what the colour Doppler image demonstrates.]
Cardiac CT angiography (CCTA)
Performed with the patient on the table of a CT scanner moved into the gantry.
- Advantages: best non-invasive test for anatomical coronary artery assessment; excellent for cross-sectional anatomy.
- Disadvantages: expensive; radiation; hard to see through calcium; limited physiological information; extra-cardiac findings.
Cross-sectional anatomy on axial CT
Four axial slices from superior to inferior, with the structures visible at each level:
- Aorta and main pulmonary artery (MPA).
- Left coronary artery and left atrium.
- Right coronary artery and right atrium on one side; left anterior descending, right ventricle and circumflex on the other.
- Right coronary artery and, on the other side, left anterior descending and circumflex; the four chambers annotated within the slice as RV, RA, LV and LA.
These are cross-referenced against an anatomical illustration of the thorax/mediastinum and a 3D volume-rendered CT reconstruction of the heart and coronary vessels, with dotted lines marking the body level of each axial slice. [Labels within the anatomical illustration are too small to read at the rendered resolution.]
Curved multiplanar reconstruction
The coronary artery can be displayed laid out along its length (curved multiplanar reconstruction), as shown for the LAD with a red marker line drawn across the vessel at the level of interest. [The plaque itself is not separately labelled — only the red line marks the level.]
Cardiac MRI
- Advantages: best for quantifying function; physiological information; tissue characterisation.
- Disadvantages: very expensive; technically demanding; patient dependent; ICA or CCTA better for coronaries; echo better for valve stenosis.
Performed with a surface coil array over the chest and the patient positioned at the bore of the scanner. Colour flow/velocity information can be overlaid on the greyscale image, so MRI supplies physiological as well as anatomical data.
MRI views and regional anatomy
- Four-chamber view: RV and LV above the atrioventricular valves, RA and LA below, with the myocardium and surrounding thoracic structures visible.
- Short-axis view through the ventricles: anterior wall, lateral wall and inferior wall around the LV cavity; interventricular septum (IVS) between LV and RV; two papillary muscles projecting into the LV cavity. This is the same regional wall segmentation seen on short-axis echo, imaged by MRI.
Tissue characterisation — late gadolinium enhancement
MRI allows the myocardium itself to be assessed, not just chamber size and function. Late gadolinium enhancement highlights abnormal myocardium as areas of bright signal.
The examples show bright enhancing signal along the outer/epicardial aspect of the lateral left ventricular wall on a long-axis view (four arrows), on a second long-axis view (one arrow), and along the outer edge of the LV wall on a short-axis view (one arrow).
The images are labelled only "Late gadolinium enhancement" — the slide does not name a diagnosis or state the pattern of enhancement in text, and the arrows are unlabelled.
Summary comparison of modalities
| Modality | Access | Cost | Spatial resolution | Temporal resolution | Physiology information | Other anatomy |
|---|---|---|---|---|---|---|
| ECG | Easy | $ | Very low | High | Limited | None |
| CXR | Easy | $ | Low | Low | None | Moderate |
| Echo | Variable | $$ | Moderate | Very high | Very high | Limited |
| Cardiac CT | Variable | $$$ | High | Moderate | Limited | High |
| Cardiac MRI | Limited | $$$$ | High | Moderate | High | Moderate |
| Invasive angiogram | Limited | $$$$ | Very high | High | High | Limited |
Key points for scanning:
- Cheapest and easiest access: ECG and CXR.
- Highest temporal resolution and highest physiology information: echo.
- Highest spatial resolution: invasive angiogram.
- Most “other anatomy”: cardiac CT.
- Most expensive / most limited access: cardiac MRI and invasive angiogram.
Case presentations
Case 1 — “chest pain”
- 68-year-old woman, ex-smoker, no cardiac history.
- Woke at 3am with pain between the shoulder blades, radiating to neck and jaw.
- ECG: inferior ST elevation.
- Imaging path: chest X-ray, then invasive coronary angiogram showing a right coronary artery occlusion.
Case 2 — ?coronary artery disease
- 69-year-old woman with chest pain.
- Two negative troponins.
- Exercise stress echo: echo normal but borderline ECG changes.
- Imaging path: CCTA, showing non-obstructive mixed plaque. Outcome: medical therapy, home.
Case 3 — chest pain with ECG changes
- 18-year-old with chest pain.
- Borderline ST elevation, troponin >20,000. Mother present.
- Imaging path: cardiac MRI, including late gadolinium enhancement for tissue characterisation. [The slide does not state a final diagnosis.]
Self-test
- List the advantages and disadvantages of the chest X-ray as a cardiovascular imaging test.
- List the advantages and disadvantages of invasive coronary angiography.
- Explain why invasive coronary angiography is the appropriate test in a patient with acute inferior ST elevation, referring to the advantage the slides emphasise.
- List the advantages and disadvantages of echocardiography.
- Describe how the parasternal short-axis view is obtained, and name the two levels shown.
- List the structures labelled around the LV cavity on the papillary-muscle-level short-axis view.
- Describe how the apical four-chamber view is obtained, and name the chambers labelled on the normal image.
- Explain the anatomical principle that underlies transoesophageal echocardiography.
- List the mitral valve segments and the three orientation landmarks labelled on the en face TOE “surgeon’s view”.
- List the advantages and disadvantages of cardiac CT angiography.
- Name the cardiac structures identified at each of the four axial CT levels, from superior to inferior.
- Explain what a curved multiplanar reconstruction shows about a coronary artery.
- List the advantages and disadvantages of cardiac MRI.
- Explain what late gadolinium enhancement adds beyond assessment of chamber size and function.
- Name the left ventricular regional structures labelled on the MRI short-axis view.
- Distinguish cardiac CT from cardiac MRI in terms of what each is best suited to, using the disadvantages the MRI slide lists.
- Using the summary table, state which modality has the highest spatial resolution and which has the highest temporal resolution.
- Using the summary table, explain why echo is often the first-line test at the bedside despite only moderate spatial resolution.
- A 69-year-old woman has chest pain, two negative troponins, and an exercise stress echo that is normal apart from borderline ECG changes. Describe the next imaging test used, the finding, and the management.
- An 18-year-old presents with chest pain, borderline ST elevation and a troponin over 20,000. Explain which modality is used to assess the myocardium itself and by what technique.
- Integrative: a patient needs both definitive assessment of a coronary lesion and immediate treatment of it. Explain why invasive coronary angiography is preferred over CCTA, and what is given up by that choice.
Answers
Reveal answers
- Advantages: cheap, portable, gives some information about the rest of the thorax. Disadvantages: limited spatial resolution, no physiological information.
- Advantages: allows percutaneous therapy to be delivered, high spatial resolution of the coronary arteries, allows advanced assessment of the arteries. Disadvantages: invasive, radiation, limited information about non-coronary anatomy.
- Because it allows percutaneous therapy to be delivered at the same sitting — the coronary occlusion (here a right coronary artery occlusion) can be both imaged at high spatial resolution and treated.
- Advantages: portable, moderate cost, fast, physiological information, real-time imaging. Disadvantages: operator dependent, patient dependent.
- Transducer placed on the left parasternal chest wall with the patient in the left decubitus position, giving a plane that cuts transversely through the ventricles. The two levels shown are the mitral valve level and the papillary muscle level.
- Interventricular septum (IVS), anterior wall, papillary muscles and inferior wall, arranged around the LV cavity.
- Transducer held at the apex with the pointer directed posteriorly, so the plane passes through all four chambers. Labelled: right ventricle (RV) and left ventricle (LV) above, right atrium (RA) and left atrium (LA) below.
- The probe is passed through the mouth into the oesophagus, which lies immediately posterior to the heart, so the transducer sits directly behind the heart and images it from there.
- Anterior leaflet segments A1, A2, A3 and posterior leaflet segments P1, P2, P3; landmarks are the aortic valve (AV) anteriorly, the left atrial appendage (LAA) to one side and the interatrial septum (IAS) on the opposite side.
- Advantages: best non-invasive test for anatomical coronary artery assessment; excellent for cross-sectional anatomy. Disadvantages: expensive, radiation, hard to see through calcium, limited physiological information, extra-cardiac findings.
- (1) Aorta and main pulmonary artery; (2) left coronary artery and left atrium; (3) right coronary artery and right atrium on one side, left anterior descending, right ventricle and circumflex on the other; (4) right coronary artery on one side and left anterior descending plus circumflex on the other, with RV, RA, LV and LA annotated in the slice.
- It lays the vessel out along its length in a single image, so a segment of the artery (for example the LAD) can be inspected along its course; in the case shown a marker line indicates the level of interest where non-obstructive mixed plaque was found.
- Advantages: best for quantifying function, physiological information, tissue characterisation. Disadvantages: very expensive, technically demanding, patient dependent, ICA or CCTA better for coronaries, echo better for valve stenosis.
- It allows the myocardium itself to be assessed — abnormal myocardium is highlighted as bright (enhancing) signal, so tissue is characterised rather than only chamber size and function. (The slide does not name a diagnosis or describe the pattern in text.)
- Anterior wall, lateral wall and inferior wall around the LV cavity; the interventricular septum between LV and RV; and two papillary muscles projecting into the LV cavity.
- Cardiac CT is the best non-invasive test for anatomical coronary artery assessment and is excellent for cross-sectional anatomy; MRI is best for quantifying function and for tissue characterisation, but the MRI slide states that ICA or CCTA are better for the coronaries and echo is better for valve stenosis.
- Highest spatial resolution: invasive angiogram (very high). Highest temporal resolution: echo (very high).
- It is portable, fast, of only moderate cost, and per the table has very high temporal resolution and very high physiological information, so it gives real-time functional data at the bedside; the trade-off is moderate spatial resolution, limited other anatomy, and dependence on operator and patient.
- CT coronary angiography (CCTA). It showed non-obstructive mixed plaque. She was managed with medical therapy and discharged home.
- Cardiac MRI, using late gadolinium enhancement, which highlights abnormal myocardium as areas of bright signal and so characterises the myocardial tissue itself.
- Invasive angiography has very high spatial resolution of the coronary arteries, allows advanced assessment of them, and uniquely allows percutaneous therapy to be delivered at the same time. What is given up: it is invasive, involves radiation, has limited access, is at the most expensive end of the table, and gives limited information about non-coronary anatomy (whereas CT is non-invasive and rates high for other anatomy).