Heart and great vessels
Heart, valves, great vessels and coronary arteries on imaging
The heart is judged by its borders and size on the chest film, and by chambers, valves and coronary arteries on echo, CT and MRI. CPSP asks which chamber forms each border, how chambers enlarge, coronary anatomy and variants, and arch anomalies.
One of the most tested topics in past papers
Surfaces, borders and size
| View | Border | Chamber |
|---|---|---|
| PA film | Right border | Right atrium (SVC above) |
| PA film | Left border | Aortic knuckle, pulmonary trunk, left atrial appendage (normally flat), left ventricle |
| Lateral film | Anterior | Right ventricle (also the main sternocostal surface) |
| Lateral film | Posterior | Left atrium above (the base, in front of the oesophagus), left ventricle below |
- Cardiothoracic ratio is reliable only on a PA film: an AP film magnifies the heart, which is further from the detector. In late pregnancy the heart is pushed up and left.
- On a lateral film, a line from the carina to the anterior costophrenic angle has the aortic valve above it and the mitral valve below. The pulmonary valve lies highest.
- Because the left atrium lies directly in front of the oesophagus, transoesophageal echo shows its appendage best, and a giant left atrium causes dysphagia and hoarseness.
| Enlarged chamber | Signs |
|---|---|
| Left atrium (mitral stenosis) | Double density behind the right heart border, splayed carina, elevated left main bronchus, bulging appendage on the left border, posterior oesophageal indentation |
| Right ventricle | Upturned apex, retrosternal space filled on lateral film |
| Left ventricle | Apex displaced down and out |
| Pulmonary trunk | Bulge below the knuckle: post-stenotic dilatation in valve stenosis; trunk wider than the aorta in pulmonary hypertension |
- An ASD gives plethoric lungs and a large right heart but a normal left atrium, because the left atrium decompresses through the defect.
- LV aneurysm after anterior infarction: apical bulge of thin scar, sometimes with mural thrombus.
Valves, sounds and valve disease
| Area | Site |
|---|---|
| Aortic | Right 2nd intercostal space at the sternal edge |
| Pulmonary | Left 2nd intercostal space |
| Tricuspid | Left lower sternal edge, 4th–5th space; right-sided murmurs louder on inspiration |
| Mitral | Apex, left 5th space in the midclavicular line |
- S1 is mitral and tricuspid closure; S2 is aortic and pulmonary closure at the start of isovolumetric relaxation, higher pitched than S1 and splitting more on inspiration. S3 comes from ventricular wall vibration during rapid passive filling (when about two-thirds of filling occurs).
| Valve lesion | Pathology and imaging |
|---|---|
| Rheumatic mitral stenosis | Thickened leaflets that dome in diastole, fish-mouth orifice from fusion of the commissures, short fused chordae; balloon valvotomy splits the commissures |
| Calcific aortic stenosis (elderly) | Heavy nodular calcium on the aortic side of three cusps, no commissural fusion (age-related degeneration); bicuspid valves calcify a decade or two earlier |
| Ebstein anomaly (maternal lithium) | Septal tricuspid leaflet displaced towards the apex, atrialised right ventricle, huge box-shaped heart, oligaemic lungs; WPW often coexists |
| Marfan aortic root | Pear-shaped root dilatation with loss of the sinotubular waist; cystic medial degeneration (fragmented elastic fibres, mucoid matrix); lens dislocates upwards (downwards in homocystinuria) |
Chamber identity
- Morphological right ventricle: moderator band (carries the right bundle branch), coarse trabeculation, tricuspid valve inserted more apically on the septum, muscular infundibulum (from the conus cordis). Morphological left atrium: narrow finger-like appendage; the right appendage is broad and triangular.
- Venae cordis minimae (Thebesian veins) drain myocardium straight into the chambers, including the left heart, adding a little desaturated blood to arterial blood (part of the normal anatomical shunt).
- Right atrium: crista terminalis with the SA node near the SVC; coronary sinus opening between the IVC and tricuspid orifice, with the AV node close by (at risk in tricuspid repair).
Pericardium
- Fibrous and serous layers; the parietal layer is supplied by the phrenic nerve (shoulder-tip pain); the visceral layer is insensitive.
- Transverse sinus: behind the aorta and pulmonary trunk, in front of the atria (clamp passed here). Oblique sinus: behind the left atrium, bounded by pulmonary veins and IVC. The superior pericardial recess is a fluid crescent behind the ascending aorta, not a node or dissection.
- The pericardial stripe between the fat lines on a lateral film is up to 2 mm. About 200–250 mL of fluid is needed before the heart shadow enlarges. On echo pericardial fluid lies in front of the descending aorta.
Coronary arteries and veins
| Artery | Course and supply |
|---|---|
| Right coronary | From the right aortic sinus, in the right AV groove; conus artery, SA nodal (about 60%), AV nodal, posterior descending in about 70% (right dominance) |
| Left anterior descending | Anterior interventricular groove; anterior two-thirds of the septum (septal branches, the first used for alcohol septal ablation), anterior wall and apex; V1–V4 changes |
| Circumflex | Left AV groove; lateral and posterior left ventricle |
| Ramus intermedius | Third branch when the left main trifurcates |
- Dominance depends on which artery gives the posterior descending artery. The RCA usually supplies the AV node, so inferior infarction causes heart block.
- Veins: great cardiac with the LAD, middle cardiac with the posterior descending artery, both into the coronary sinus; anterior cardiac veins enter the right atrium directly.
- Dangerous variants: an anomalous coronary running between the aorta and pulmonary trunk (exercise syncope or death); left coronary from the pulmonary trunk, which becomes symptomatic as pulmonary resistance falls and flow reverses. A myocardial bridge covers a short tunnelled segment.
- Coronary CT: nitrate dilates the arteries; calcium is counted above 130 HU. The left internal thoracic artery to the LAD is the best graft; vein grafts are reversed because of their valves.
- Perfusion and MRI: a defect at stress but not rest is ischaemic viable muscle. Late gadolinium in a coronary territory is infarct; patchy mid-wall suggests sarcoidosis. Diffuse global subendocardial enhancement with a dark blood pool means amyloid (for example in myeloma): thick walls on echo but low QRS voltages, because the walls are infiltrated, not muscular.
- Adenosine stress: adenosine dilates normal coronary arterioles and steals flow from stenosed beds. Bronchospasm is reversed by aminophylline, a methylxanthine adenosine-receptor blocker; caffeine is avoided before the test for the same reason. Inferior wall defects may be diaphragm attenuation artefact.
Great vessels and their anomalies
| Finding | Explanation |
|---|---|
| Bovine arch | Common origin of brachiocephalic and left common carotid; commonest variant |
| Aberrant right subclavian | Last arch branch, passes behind the oesophagus (oblique posterior indentation); right laryngeal nerve non-recurrent |
| Double aortic arch | Persistent right dorsal aorta; ring round trachea and oesophagus |
| Right arch with mirror-image branching | Tetralogy of Fallot (upturned apex, oligaemic lungs) or truncus |
| Pulmonary sling | Left pulmonary artery from the right, passing between trachea and oesophagus |
| Persistent left SVC | Vein lateral to the arch draining into a dilated coronary sinus |
| Egg on its side, narrow pedicle | Transposition: aorta from the right ventricle in front of the pulmonary trunk, because the aorticopulmonary septum failed to spiral; severe cyanosis from birth |
| Figure-of-eight heart | Supracardiac total anomalous pulmonary venous drainage |
| Small right lung, heart shifted right, curved tubular shadow widening down beside the right heart border | Scimitar syndrome: anomalous right pulmonary vein draining into the IVC |
- Fetal three-vessel view, left to right: pulmonary trunk, aorta, SVC.
- Aortic dissection: Stanford A involves the ascending aorta wherever the tear begins (rupture into the pericardium causes tamponade); type B spares it. Intramural haematoma: hyperdense wall crescent on plain CT, no flap. A smooth ductus diverticulum at the isthmus is not a tear.
Masses and pulmonary vascular disease
| Finding | Diagnosis |
|---|---|
| Several echogenic masses in fetal ventricular walls; later infantile spasms and ash-leaf patches | Rhabdomyomas of tuberous sclerosis; most regress, so no early surgery |
| Atrial septum thickened by fat (about −95 HU), dumbbell shape sparing the fossa ovalis, obese elderly patient | Lipomatous hypertrophy of the interatrial septum; benign, may cause arrhythmia |
| Left atrial mass on a stalk from the fossa ovalis | Myxoma |
| Eccentric wall-adherent clot, webs, enlarged bronchial arteries, mosaic lungs after a past embolus | Chronic thromboembolic pulmonary hypertension; potentially curable by endarterectomy |
| Saddle embolus with right ventricle wider than left, septum bowed left, contrast reflux into hepatic veins, hypotension | Acute right ventricular pressure overload: the dilated RV pushes the septum into the LV and cuts LV filling, so output falls; large fluid boluses can worsen it |
Remember On the PA film the right border is right atrium and the left border is mostly left ventricle; the right ventricle is the front and the left atrium the back.
Exam trap Cardiothoracic ratio from an AP film overestimates heart size.
Exam trap Dominance is decided by the origin of the posterior descending artery, not by which artery is larger.
How FCPS asks about this
- Right heart border on a PA film: right atrium; left border mostly left ventricle.
- Where the tricuspid valve is heard: left lower sternal edge.
- Fish-mouth mitral valve: rheumatic commissural fusion.
- Marfan aortic root: cystic medial degeneration.
- Thick walls with low ECG voltage and diffuse subendocardial enhancement: cardiac amyloidosis.
- Transposition of the great arteries: failed spiralling of the aorticopulmonary septum.
- Scimitar vein drains into: inferior vena cava.
Test yourself on this topic
5 of the 101 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
A 78-year-old man has exertional syncope and an ejection systolic murmur. At valve replacement, the excised aortic valve has three cusps with heavy nodular calcification on their aortic surfaces and no fusion of the commissures. What is the pathology?
Answer: Age-related calcific degeneration
Calcific aortic stenosis of the elderly develops on a normal three-cusp valve after years of mechanical stress, lipid deposition and inflammation, resembling atherosclerosis. Calcium nodules form on the outflow (aortic) surfaces of the cusps at their bases, stiffening them, while the commissures stay separate. Rheumatic disease fuses the commissures and usually affects the mitral valve as well. A bicuspid valve has two cusps and calcifies earlier, in the 50s and 60s.
Calcific aortic stenosis
- Elderly, three-cusp valve
- Nodules on aortic side of cusps
- Commissures not fused
- Bicuspid valves calcify earlier
Remember Old man, tricuspid valve, no commissural fusion: degenerative.
Exam trap Do not assume every calcified aortic valve is rheumatic; commissural fusion is the clue.
Why the other options are wrong
- Rheumatic aortic valve disease Causes commissural fusion and usually mitral disease too.
- Congenital bicuspid aortic valve Has two cusps and presents younger.
- Infective endocarditis Shows vegetations and destruction rather than nodular calcium.
- Myxomatous degeneration Affects mainly the mitral valve with floppy leaflets.
Three months after a large anterior myocardial infarction, a 60-year-old man has persistent ST elevation in V1–V4 and a localised, thin-walled, dyskinetic bulge at the left ventricular apex. What forms the wall of this bulge?
Answer: Thin fibrous scar of the ventricular wall
A true left ventricular aneurysm develops weeks to months after a large transmural infarct, usually in the LAD territory at the apex and anterior wall. The necrotic muscle is replaced by collagenous scar that thins and bulges outwards in systole (dyskinesia), and its wall may calcify. ST elevation persists over the area. A false aneurysm (pseudoaneurysm) follows rupture of the wall and is contained only by pericardium and haematoma. Granulation tissue is seen at one to two weeks, not three months.
True LV aneurysm
- After large anterior transmural MI
- Wall of fibrous scar, may calcify
- Persistent ST elevation
- Risks: thrombus, failure, VT
Remember Old anterior MI with a bulging calcified apex: true aneurysm.
Exam trap A narrow-necked bulge suggests a false aneurysm, which can rupture and needs surgery.
Why the other options are wrong
- Organised haematoma bounded by pericardium Describes a false aneurysm after contained rupture.
- Hypertrophied surviving myocardium Surviving muscle thickens; it does not bulge thinly.
- Granulation tissue with new capillaries Present at 1–2 weeks, replaced by scar by three months.
- Calcified mural thrombus alone Thrombus may line the aneurysm but does not form its wall.
A 28-year-old woman with a fixed split second sound has a large ostium secundum atrial septal defect. Her right atrium, right ventricle and pulmonary trunk are enlarged and her lungs plethoric, but her left atrium is normal in size. Why is the left atrium not enlarged?
Answer: It decompresses into the right atrium
In a secundum ASD, the extra blood returning from the lungs to the left atrium passes straight across the defect into the right atrium, which is more compliant. The left atrium therefore never holds the excess volume and stays normal in size, while the right atrium, right ventricle and pulmonary arteries carry the shunted volume and enlarge. This is a useful contrast with a VSD or PDA, where the left atrium does enlarge because the excess blood must pass through it and the left ventricle.
ASD haemodynamics
- Large RA, RV, pulmonary trunk
- Plethoric lungs
- Normal left atrium
- Shunt at atrial level
Remember Shunt with a normal left atrium: think ASD.
Exam trap Mitral stenosis with an ASD (Lutembacher) would enlarge the left atrium.
Why the other options are wrong
- The shunt flows from right to left The shunt is left to right until late pulmonary hypertension.
- The mitral valve is regurgitant Mitral regurgitation would enlarge the left atrium.
- Pulmonary venous return is reduced Pulmonary venous return is increased, not reduced.
- The left atrium is thick-walled The left atrium is thin-walled.
In a child with heterotaxy, where venous connections may be abnormal, which feature of an atrium most reliably identifies it as the morphological left atrium?
Answer: A narrow, finger-like appendage
The atria are best identified by their appendages, because venous connections can be abnormal. The morphological left atrial appendage is long, narrow and finger-like with a narrow junction, and its pectinate muscles are confined within it. The morphological right appendage is broad and triangular with a wide junction, and pectinate muscles extend round the vestibule of the tricuspid valve. Pulmonary veins can drain anomalously and the IVC can be interrupted, so venous connections mislead in heterotaxy.
Atrial appendages
- Left: narrow, finger-like
- Right: broad, triangular
- Right: pectinate muscles round vestibule
- Veins are unreliable markers
Remember Find the finger: that is the left atrium.
Exam trap In heterotaxy both appendages can be of the same type (isomerism).
Why the other options are wrong
- A broad, triangular appendage Marks the morphological right atrium.
- Receiving the pulmonary veins Pulmonary veins can drain anomalously, so this is unreliable.
- Receiving the inferior vena cava The IVC may be interrupted or drain abnormally in heterotaxy.
- Pectinate muscles round the vestibule Marks the morphological right atrium.
A 60-year-old man has had one heart valve replaced. On his lateral chest film, a line drawn from the carina to the anterior costophrenic angle passes below the prosthetic ring, which lies above and in front of it. Which valve has been replaced?
Answer: Aortic valve
On a lateral chest film, a line from the carina to the anterior costophrenic angle roughly divides the aortic from the mitral valve. The aortic valve lies above and in front of this line, in the centre of the heart, while the mitral valve lies below and behind it. On the frontal film the aortic valve sits higher and more medial than the mitral valve, which projects lower and to the left. The tricuspid valve lies further forward and to the right, and pulmonary valve replacements are rare and high.
Prosthetic valve position
- Lateral line: carina to anterior costophrenic angle
- Above: aortic
- Below: mitral
- Frontal: aortic higher and medial
Remember Above the line, aortic; below, mitral.
Exam trap Rotation of the film can move rings; confirm with the frontal view or echo.
Why the other options are wrong
- Mitral valve Lies below and behind the line.
- Tricuspid valve Lies lower and further forward, near the right heart border.
- Pulmonary valve Lies higher and more anterior near the outflow tract; seldom replaced.
- Eustachian valve Not a replaced valve; a fold at the IVC opening.
Where this sits in the CPSP syllabus
- Diagnostic Radiology, Paper 2: Thorax, Heart, great vessels and coronary arteries
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