Cardiovascular Anatomy And Radiology

Pericardium, Heart and Great Vessel I

• Pericardium: fibroserous membrane sac that covers the heart. The pericardium consists of two layers:
- Fibrous pericardium: tough external layers that is continuous with the central tendon of the diaphragm
- Serous pericardium: layer of membrane composed mainly of mesothelium with parietal pericardium lining the internal surface of the fibrous pericardium and is reflected onto the heart at the great vessels as visceral pericardium.
• Fibrous pericardium: protects the heart against sudden overfilling
- Continuous superiorly with tunica adventitia of great vessels
- Attached anteriorly to the posterior surface of the sternum by the sternopericardial ligament
- Bound by loose connective tissue to structures in the posterior mediastinum
- Continuous inferiorly with central tendon of the diaphragm.
• Serous pericardium: the visceral pericardium makes up the epicardium of the heart wall and extends to the beginning of the great vessels, becoming parietal pericardium where aorta and pulmonary trunk leave the heart and where the SVC and IVC and pulmonary veins enter the heart.
• Transverse pericardial sinus: large passage in the pericardial cavity that lies between the afferent and efferent great vessels when these are brought closer together during cardiac folding.
• Oblique pericardial sinus: the pericardial reflection/recess posterior to the heart where the serous pericardium folds back on itself at the pulmonary veins and IVC. The sinus can be entered inferiorly admitting several
• Arterial supply of pericardium: slender branch of their internal thoracic artery called the pericardiacophrenic artery contribute primarily to the pericardium along with other smaller vessels such as musculophrenic artery, bronchial, esophageal and superior phrenic artery, coronary arteries
• Venous drainage of pericardium: pericardiacophrenic veins and variable tributaries of azygos venous system
• Nerve innervation:
- Phrenic nerves (C3 –C5, these also supply skin of the shoulder so pain signal from the heart is interpreted as pain from the shoulders. This is called referred pain)
- Vagus nerves
- Sympathetic trunks
• Walls of the heart: three layers
- Endocardium: a thin layer of membrane made up of endothelium and connective tissue, which lines the internal surface of the heart along with its valves
- Myocardium: thick helical middle layer composed by cardiac muscle
- Epicardium: thin external layers of mesothelium formed by the visceral layer of serous pericardium
• Fibrous skeleton of the heart: framework of dense collagen that forms the structural foundation of the heart with 4 rings around the valves
- Keeps the orifice of the AV and semilumar valves patent and non-distended
- Attachment of the leaflet and cusps of valve
- Attachment for myocardium which, when uncoiled, forms a continuous ventricular myocardial band
- Forms an electrical insulator by separating the myenterically conducted impulses of atria and ventricles hence allowing them to contract independently.
• Fibrous trigone: triangular mass of fibrous tissues, part of the fibrous skeleton, that connects the margins of the rings. Left trigone connects left AV ring with aortic ring while right trigone connects right AV ring with aortic ring.
• Structural features of the heart: The trapezoidal heart is situated obliquely with two thirds on the left of the median plane and lies behind the sternum, costal cartilage and anterior ends of the 3 – 5th left ribs
- External demarcations: atria from ventricles by the atrioventricular (coronary) groove, ventricles are separated by anterior and posterior interventricular grooves
- Apex: formed by the inferolateral part of the left ventricle and lies posterior the left 5th intercostals space. It is the location where mitral valve sound (apex beat) is most clearly heard.
- Base: formed by the left atrium with some right atrium and faces toward the bodies of T6 – T9 with the oesophagus, aorta and pericardium in between. Superior boundary is the bifurcation of pulmonary trunk while inferiorly the coronary groove.
• Surface of the heart:
- sternocostal surface: right ventricle
- diaphragmatic surface: left ventricle and partly right ventricle
- right pulmonary surface: right atrium
- left pulmonary surface: left ventricle forming the cardiac impression of the left lung
• Borders of the heart:
- Right border: slightly convex formed by right atrium and extending between SVC and IVC
- Inferior border: mainly the right ventricle and partly by of the left ventricle
- Left border: mainly by the left ventricle and slightly by the left auricle
- Superior border: right and left atria and auricle. Aorta and pulmonary trunk emerges here and SVC enters on the right side. Posteriorly is the inferior boundary of the transverse pericardial sinus.
• Right atrium: chamber of the heart that receives venous blood from SVC, IVC and coronary sinus and pumps them into the right ventricle.
- Right auricle: muscular pouch that projects from this chamber to increase capacity of atrium.
- Sinus venarum: smooth thin-wall posterior portion of the right atrium in which the great vessels empty poorly oxygenated blood into.
- Anterior portion is rough and muscular composed of pectinate muscle.
- Right AV orifice: opening in which the deoxygenated blood passes to enter the right ventricle
- Sulcus terminalis: external shallow vertical groove that separate the smooth and rough parts of the atrial wall
- Crista terminalis: internal vertical ridge that demarcates atrium to auricle
• Features of right atrium:
- SVC opens into the superior part of the RA at level of 3rd right costal cartilage
- IVC opens into the inferior part of the RA at the level of 5th costal cartilage
- Opening of coronary sinus is between right AV orifice and SVC orifice
- Oval fossa is a remnant of oval foramen located in the interatrial septum
• Right ventricle: chamber of the heart that receive venous blood from the right atrium and pumps it to the lung (pulmonary circuit)
- Conus arteriosus: a funnel-shaped infundibulum located superiorly of the right ventricle that leads into the pulmonary trunk
- Trabeculae carneae: irregular muscular elevations on the interior of the right ventricles
- Supraventricle crest: thick muscular ridge that separates the smooth muscular wall of the inflow part from the conus arteriosus (outflow part).
- AV orifice: passageway for blood from right atrium to ventricle, located posterior to the body of sternum in level with the 4th and 5th intercostal space.
• Interventricular septum: muscular and membranous partition between the right and left ventricles and forms the wall for each.
- Muscular part: as thick as the remainder of the wall of the left ventricles.
- Membranous part: thin membrane, a part of the fibrous skeleton of the heart, situated superiorly and posteriorly. As the tricuspid valve is attached to this membrane, it provides the boundary for the interventricular and atrioventricular septum.
• Septomarginal trabeula: curved muscular bundle carrying the right branch of the AV bundle that traverses the right ventricular chamber from inferior part of IVS to base of anterior papillary muscles.
• Left atrium: chamber of the heart that receives oxygenated blood from pulmonary vessels and pumps it into the left ventricle.
- Left auricle: tubular muscular pouch where its walls are trabeculated with pectinate muscles and overlaps the root of the pulmonary trunk. It is the remains of the primordial atrium.
- Semilunar depression: depression in the interatrial septum indicates the floor of the oval fossa. The ridge surrounding the oval fossa is the valve of the oval fossa.
• Features of the left atrium:
- Predominantly smooth wall and small rough auricle
- Four pulmonary veins enters its smooth posterior wall
- Slightly thicker wall than right atrium
- Interatrial septum slopes to right and posteriorly
• Left ventricle: large chamber responsible oxygenated blood to the body (systemic circuit).
- Trabeculae carneae: rough muscular meshwork that are finer and more numerous than those of the right ventricle
- Aortic vestibule: smooth-walled non-muscular outflow part of the left ventricle located superoanteriorly leading to the aortic orifice.
- Aortic orifice: entrance into the aorta that lies in its right posterosuperior part of the ventricle surrounded by a fibrous ring
• Features of the left ventricle:
- Muscular walls are 2-3 times thicker than that of the right ventricle
- Conical cavity that is longer than right ventricle
- Anterior and posterior papillary muscle are larger than those in the right ventricle
• Blood supply of the heart: network of coronary arteries and cardiac veins carry blood to and from the myocardium. The endocardium receives oxygen and nutrients by diffusion or microvasculature directly from the chambers of the heart.
• Coronary supply to heart: dominance is defined by which artery gives rise to the posterior descending artery and is typically right coronary artery.

• Courses and distribution:
- Right coronary artery: arises from right aortic sinus running in the coronary groove and turns left and continues to the posterior aspect of the heart within the coronary groove.
- Sinuatrial nodal branch: emerge from the RCA near the origin which ascends and supply the SA node
- Right marginal branch: arises from the RCA when it descends the coronary grove and supplies the right ventricle. Artery runs toward but (does not reach) the apex.
- Atrioventricular nodal branch: given off at the crux of the heart (junction of the septa) and it supplies the AV node
- Posterior descending artery: arise from the RCA and descends in the posterior IV groove toward apex of the heart. It supplies adjacent area of both ventricles and sends perforating interventricular septal branches into the IV septum.
- Left coronary artery: initiates from the left aortic sinus and passes from between left auricle and left side of the pulmonary trunk into the coronary groove. At the superior end of the anterior IV groove, LCA bifurcates.
- Anterior IV branch: right branch of the LCA that passes along the IV groove to the apex where it turns around the inferior border. Supplies 2/3 of IVS and left and right ventricle
- Lateral diagonal branch: branch of the LAD that descends on the anterior surface of the heart
- Left marginal artery. A branch of the circumflex branch follows the left border of the heart and supplies the left ventricle.
- Smaller circumflex branch: follows the coronary groove around the left border of the heart to posterior surface.
• Anastomoses:
- Posterior IV with anterior IV at apex
- Right coronary with circumflex of left coronary
• Venous drainage of the heart: veins drain the blood into the coronary sinus and partly by small vein that empty into the right atrium.
- Coronary sinus: main vein of the heart running from left to right in the posterior coronary groove. It receives three cardiac vein along with the left posterior ventricular vein and left marginal vein.
- Great cardiac vein: main tributary of the coronary sinus. Its first part, the anterior IV vein, ascends from apex and upon reaching the coronary groove, turns left and the second part circles to the back with the circumflex branch of LCA to reach the coronary sinus. Great cardiac vein drains areas supplied by LCA
- Middle cardiac vein: the posterior IV vein accompanies the posterior IV artery
- Small cardiac vein: counterpart of right marginal branch of RCA
- Oblique vein of left atrium: small vessel that descends over the posterior wall of left atrium and combines with greater cardiac vein to become the coronary sinus (remnant of the embryonic left SVC)
- Anterior cardiac veins: cross the anterior surface of ventricle and end directly in the right atrium
- Smallest cardiac vein: minute vessels that communicate with the atria from the capillary beds of myocardium.
• Cardiac plexus: autonomic nerve innervation of the heart that lies in the bifurcation of the trachea.
- Sympathetic nerve supply: efferent fibers of T1-T5 (or T6) of spinal cord innervate the heart myocardium, coronary arteries and conduction system (SA and AV nodes). Stimulation will increase heart rate (rapid depolarization and AV conduction) and force of contraction and coronary artery dilation.
- Parasympathetic nerve supply: efferent fibers are from the vagus nerve and stimulation slows heart rate and reduce force of contraction and constrict coronary arteries.
- Afferent fibers: pain sensation travels with postganglionic sympathetic to enter the paravertebral sympathetic chain and then spinal nerve while cardiovascular reflexes travel with preganglionic parasympathetic fibers of vagus to reach the brainstem.

Mediastinum Radiology

• Mediastinum: central compartment of the thoracic cavity
- Boundaries: superiorly the thoracic aperture, inferiorly to diaphragm, sternum and costal cartilage anteriorly, thoracic vertebrate posteriorly
• Features of mediastinum:
- Mobility due to its occupation by hollow visceral structures connected with loose connective tissue and fat.
- Covered on each side by mediastinal pleura along with elastic lung to accommodate volume/pressure change with breathing, and pulsation of large vessels.
• Anatomic divisions of mediastinum:
- Superior mediastinum: superior thoracic aperture to horizontal plane of sternal angle
- Inferior mediastinum: sternal angle plane to the diaphragm. Further divided into anterior, middle and posterior compartment.
- Anterior mediastinum: space anterior to the heart
- Middle mediastinum: space occupied by the heart
- Posterior mediastinum: space posterior to the heart
• Content of mediastinum:
- Superior mediastinum: greater vessels, trachea, oesophagus, lymphatics and part of thymus
- Anterior mediastinum: lymph nodes, lymphatics and nerves, thymus
- Middle mediastinum: heart, great vessels
- Posterior mediastinum: thoracic aorta, thoracic duct, lymph nodes, azygos, hemi azygos vein, oesophagus, vertebrate and autonomic nerve supplies
• Radiographic abnormalities and distinctions: based on structures visible on chest radiography. Middle features are marked by paratracheal stripe and azygoesophageal recess.
- Superior: common abnormality is a goitre which is the swelling of the neck from an enlarged thyroid gland due to iodine deficiency. When the thyroid enlarged, it can only extend to anterior mediastinum.
- Anterior: common problem include lymphadenopathy due to lymphoma, and thymic neoplasms. Other anterior mediastinal masses in young men relate to germ cell tumour such as teratomas
- Middle: also includes oesophagus and carina of trachea in radiology and involves predominantly cardiac abnormalities. Effusion due to surgery, infection, renal failure etc is common. Lymphadenopathy is the most common non-cardiac abnormality and due to lymphoma or metastases. Other include oesophageal diverticulae and dilatation and bronchogenic cyst
- Posterior: most common are neural tumours as the compartment contains sympathetic nerves and splanchnic nerves
• Universal mediastinum abnormalities:
- Infections: post surgical complications and oesophageal perforations, e.g. mediastinitis
- Adjacent abnormalities: lung neoplasms and obstructive lung disease can secondarily affect mediastinum. Cancer invade any compartment
• Distinguish mediastinal from pleural:
- Mediastinal masses form obtuse angles and lung lesion form acute angles
- Projections over hilum, the pulmonary vessel is visible called “hilum overlay”
- Lung masses more likely to show air bronchograms
• Modalities: chest X-Ray is the most important to identify the presence and location of an abnormality while CT and MRI is used to further characterize an abnormality and its extent.
• Vascular problems:
- Features: can be congenital (aortic arch abnormality) or acquired (aortic dissection in catheters or aneurysms and coronary vessel disease)
- Signs: pain
- Radiology feature: large white out of the widening mediastinum from effusion
• Trauma: iatrogenic causes usually involving central line or tube placement. Misplaced line causes haematoma formation and fluid effusion within the mediastinum and commonly pneumothorax
- Blunt trauma: mobile accident presents as large white area of bleeding in the mediastinum with gray area over the lungs.
- Barotrauma: rupture of bronchi due to high intra-alveolar pressure as an result of asthma etc causes pneumomediastinum
- Oesophageal rupture: widening of the mediastinum with signs of chest pain. Causes due to excessive abrasion and vomiting, e.g. hangover from over drinking.
• Neoplasms: tumour of the mediastinum arises from metastasis to mediastinal nodes from lung cancer etc. Thymic tumours, thyroid tumours.
- Superior mediastinum: goitre extends above the levels of the clavicle and displaces trachea shown as a bulge out of the white tubule structure.
- Anterior mediastinum: lateral film usually very helpful. White lumpy patch on the x-ray occupied most of the middle of the thoracic cavity are usually large lymphomas. On a CT, the anterior portion of the section is gray that extends into pleural cavity. The main problems are lymphoma (terrible), thyroid, teratoma, thymic tumour
- middle mediastinum: oesophageal hernia is visible as the air-fluid levels is next to the heart. Oesophageal diverticulum appears as a little gray pouch to the right pleura from the inferior of the heart. Bronchogenic cyst presents as multimodal white masses around the heart. Achalasia is seen as air fluid level is near the top of the oesophagus
- Posterior mediastinum: neurogenic tumours such as neuroblastoma can be shown by CT scan as white mass next to the vertebrate body

Lecture 8: Pericardium, Heart and Great Vessel II
• Chordae tendineae: cord-like tendons that connect the apices of the papillary muscles to the free edges of the mitral and tricuspid cusps.
• Papillary muscles: conical muscular projections from the ventricular wall that acts as anchors for the AV valves.
- Function: contraction before systole to tighten the tendinous cords and drawing the cusp together to prevent backflow of blood into the atria.
• Triscupid valve: three leaflet valve that guards the right AV orifice (right atrium to ventricle). Base of the valve are attached to the fibrous ring of fixed diameter allowing the cusp to make contact (close) with each heart beat.
- Cusps: anterior, posterior and septal
- Papillary muscles: anterior papillary is the largest arising from anterior wall and the cords attach to both anterior and posterior cusp. Posterior papillary arise from inferior walls and connects to posterior and septal cusp. Septal papillary muscles arise from interventricular septum and its cords attach to anterior and septal cusp.
• Mitral valve: two cusp valve guards the left AV orifice (left atrium to ventricle). It is located at the level of 4th costal cartilage posterior to the sternum. Reversal of blood occurs near the anterior cusp.
- Cusp: anterior and posterior
- Papillary muscles: more than one papillary muscles supply the cusp and these help the valve resist pressure of the left ventricle.
• Semilunar valve: a type of valve whose cusp are shaped like a cup to catch and prevent the backflow of blood from the greater vessel to the ventricles.
- Pulmonary valve: valve that occupy the pulmonary orifice (right ventricle to pulmonary trunk) with anterior, left and right cusps. Location is the left 3rd costal cartilage
- Aortic valve: valve located at the aortic orifice (left ventricle to aorta) with posterior, right, left cusps. The level is the 3rd intercostals space posterior to the sternum.
• Features of semilunar valve:
- Concave valves with no tendinous cord and smaller area of than cusps of AV valves
- Ventricular contract force the valve to open into the artery and during recoil, the valve closes.
• Conducting system of heart: co-ordinate the cardiac cycle through regulating and facilitating the conduction of action potential from the pacemaker to the rest of the heart.
- Sinuatrial node: collection of nodal tissue located anterolaterally just deep to the epicardium at the junction of SVC and right atrium. This location initates the electric impulses.
- AV node: smaller collection of nodal tissue at the posteroinferior region of the interatrial septum near the opening of the coronary sinus. It receives AP from myogenic conduction from the SA
- AV bundle: bundle of conducting fibers that provide the only bridge from the atrial to ventricular myocardium. Sympathetic stimulate speeds up conduction while parasympathetic slows down.
- Purkinje fibers: conducting branches that are derived from the left and right division of the AV bundle (at the crux of the heart) and they proceed deep to the endocardium and extend into the walls of respective ventricles.
• Distribution of ventricles:
- Right branch: stimulate muscles of the IVS, anterior papillary muscles through moderator band and walls of right ventricle
- Left branch: divides near origin into six smaller tracts to stimulate IVS, anterior and posterior papillary muscles and wall of the left ventricle.

Mediastinum I

• Superior mediastinum: superior to the transverse plane of the sternal angel. Arranged from anterior to posterior the contents are thymus, greater vessels, cervical viscera the trachea and oesophagus with related nerve, thoracic duct and lymphatic trunk.
• Thymus: a primary lymphoid organ located in the anterior part of the superior mediastinum (below neck). Part of it extends down into the anterior mediastinum anterior to the pericardium.
- Arterial supply: anterior mediastinal branches of the internal thoracic arteries
- Vein drainage: drains into left brachiocephalic, internal thoracic and inferior thyroid vein
• Greater vessels: the veins and arteries that empties or exits directly from the heart along with their derivatives.
• Brachiocephalic veins:
- formed posterior to SC joint by the internal jugular and subclavian veins
- at the level of the inferior border of 1st right costal cartilage, empties into SVC
- Left brachiocephalic vein: twice as long as right vein because it needs to cross over while passing over anteriorly to the three major branches of the aorta. Drains blood from head, neck and left upper limb.
• Superior vena cavae: large vein that returns blood from all structures superior to the diaphragm, except the lungs and heart.
- Empties into the right atrium at the level of 3rd costal cartilage
- It lies on the right side of the superior mediastinum, anterolateral to trachea and posterolateral to ascending aorta.
- Its terminal half is located in the middle mediastinum beside the ascending aorta forming the posterior boundary of transverse pericardial sinus
• Ascending aorta: the major artery of the body arising directly from the left ventricle beginning at the aortic orifice.
- Intrapericardial and hence part of the middle mediastinum
- Only branches are the coronary arteries
• Arch of aorta: curved continuation of the ascending aorta. Three major branches are the brachiocephalic trunk, left common carotid artery and left subclavian artery
- Begins posterior to the 2nd SC joint at the sternal angle and arches posteriorly, inferiorly and to the left
- Ascends anterior to the right pulmonary artery and bifurcation of the trachea, peaking at the left side of the oesophagus and down posterior the left bronchi.
- Becomes the descending aorta at the 2nd left SC joint
• Brachiocephalic trunk: the first and largest branch of the arch of the aorta located anterior to the trachea and posterior to the left brachiocephalic vein
- Ascends superolaterally to reach the right side of the trachea and divides into right common carotid and right subclavian arteries.
• Left common carotid artery: the second branch of the arch of aorta
- Slightly posterior to brachiocephalic trunk
- Ascends anterior to left subclavian and trachea then passing to its left
- Passes posterior the left SC joint as it enters the neck
• Left subclavian artery: third branch of the arch arising from the posterior part of the aorta just posterior to the left common carotid.
- Ascends lateral to the trachea through he superior mediastinum
- Passes posterior to the left SC joint as it enters the neck
• Nerves of the superior mediastinum:
- Vagus nerve: exits the cranium and descend through the neck posterolateral to the common carotids arteries.
- Right recurrent laryngeal: hooks around the right subclavian artery and ascends between the trachea and oesophagus.
- Left recurrent laryngeal: passes inferior to the arch of aorta lateral to the ligamentum arteriosum and ascends to larynx between trachea and oesophagus.
- Phrenic nerves: supply the diaphragm and also pericardium and mediastinal pleura. Phrenic passes anterior to the roots of the lungs which is an important distinction from the vagus nerve.
• Right vagus nerve: enters the thorax anterior to the right subclavian artery and gives rise to the right recurrent laryngeal nerve. The nerve then runs posteroinferiorly through the superior mediastinum on the right side of the trachea passing behind SVC, right brachiocephalic vein, and right bronchus.
- Contribute to right pulmonary plexus and pass to the oesophageal nerve plexus
- Also gives nerve that forms the cardiac plexus
• Left vagus nerve: descend posterior to the left common carotid artery. When it reaches the left side of arch of the aorta, the nerve diverges posteriorly from the left phrenic nerve. As it curves medially at the inferior border of the aorta it gives off the left recurrent laryngeal nerve. The nerve continues inferiorly posterior to the roots of the left lung.
- Contribute to the left pulmonary plexus and then pass as a single branch to the oesophageal plexuses
• Right phrenic nerve: pass along the right brachiocephalic vein, SVC over the right atrium and descends on the right side of the IVC to the diaphragm in which it pierces near the caval opening.
• Left phrenic nerve: descends between the left subclavian and left common carotid arteries. It crosses the left surface of the arch and descends anterior to the root of the left lung and over the left atrium. Distribution occurs at the inferior surface of the diaphragm
• Trachea: descends anterior to the esophagus and enters superior mediastinum. Posterior surface of the trachea is flat. The trachea divides at the sternal angle into right and left main bronchi.
• Oesophagus: fibromuscular tube extends from the pharynx to the stomach. Enters the superior mediastinum between trachea and vertebral column and lies anterior to the bodies of T1 – T4.
- Initially inclines to the left but deviated back to median plane by arch of aorta and then afterwards to left again. Later it is compressed by the root of the left lung.
• Thoracic duct: lies on the left side of the oesophagus deep to the arch of the aorta.

Mediastinum II

• Posterior mediastinum: located inferior to the sternal angle plane, anterior to the T5-T12 vertebrae and posterior to the pericardium and diaphragm. Content include thoracic duct, aorta, lymphatic trunks, posterior mediastinal lymph node, azygos and hemiazygos and oesophagus and oesophageal nerve.
• Thoracic aorta: continuation of the arch of aorta starting on the left side of the T4 vertebrate and pass down in the posterior mediastinum on the left sides of the vertebrate. As it descends, it approaches the median plane and displaces the oesophagus to the right. The thoracic aorta terminates at the aortic hiatus in the diaphragm.
• Branches of thoracic aorta: these course within three vascular planes
- Anterior midline plane of unpaired visceral branch to gut. Example of this is the oesophageal arteries
- Lateral planes of paired visceral branches serving viscera other than gut, e.g. bronchial arteries.
- Posterolateral planes of paired, segmental branches to the body wall, e.g. the nine posterior intercostals arteries.
- Exceptions: superior phrenic arteries are parietal branches that pass anterolaterally to the superior surface of the diaphragm instead of body wall. Pericardial branches that are unpaired from the anterior midline buy pass to the pericardium instead of gut.
• Oesophagus: oesophagus constitutes the primary posterior relationship of the base of the heart. It then deviates to the left and through the oesophageal hiatus. The oesophagus have three impressions:
- Arch of aorta
- Left main bronchus
- Diaphragm (best lateral view)
- These can be observes using barium meal.
• Thoracic duct: lies on the anterior aspect of the inferior 7 thoracic vertebrae. It is the largest lymphatic channel in the body and conveys lymph directly to the venous system.
- Originates from chyle cistern in the abdomen and ascending through the aortic hiatus
- Accompanied by the thoracic aorta on its left and azygos vein on its right and oesophagus anteriorly
- At sterna angle level, the thoracic duct crosses to the left of the oesophagus posteriorly
- Thoracic duct empties into the venous system near the union of left internal jugular and subclavian vein (origin of brachiocephalic vein).
• Azygos system: systems of veins that drain the blood back from the thoracoabdominal walls arising from the subcostal and lumbar veins. The origin, course, tributaries and anastomoses of this system show much variation.
- Azygos vein: collateral pathways between the IVC and SVC ascending close to the right sides of the inferior 8 thoracic vertebrae and arches over the superior aspect of the right bronchus to join the SVC. The azygos vein drains the 11 inferior-most right posterior intercostal veins along with mediastinal, esophageal, bronchial veins. Also communicates with vertebral venous plexuses that drain the back, vertebrae and vertebral canal.
- Hemiazygos vein: drains the left side of the body wall through the left subcostal and lumbar veins inferiorly from T9 downwards (9, 10, 11, 12). At the T9, it crosses to the right posterior to aorta, thoracic duct and oesophagus and joins the azygos vein.
- Accessory hemiazygos vein: begins at the medial end of the 4/5th intercostals space and descends on the left side of the vertebral column form T5 to T8. Drains 4th to 8th posterior intercostals vein and sometimes from left bronchial vein. Crosses at T8 vertebra to join the azygos vein.
• Left superior intercostals vein: drains the 1st to 3rd left intercostals spaces and empties into the left brachiocephalic vein. May communicate with accessory hemiazygos vein.
• Nerves of posterior mediastinum: sympathetic trunks and their ganglias
- Thoracic sympathetic trunk: continues with cervical and lumbar trunks. Thoracic trunks lie against the head of the ribs superiorly and the sides of vertebral bodies inferiorly.
- Lower thoracic splanchnic: composed of greater, lesser and least splanchnic nerves and supplies viscera inferior to the diaphragm. It consists of presynaptic fibres from 5th through the 12th sympathetic ganglia, which pass through the diaphragm supplies sympathetic innervation for most of the abdominal viscera
• Anterior mediastinum: smallest subdivision of the mediastinum lies between body of sternum and transverse thoracic muscle anteriorly and pericardium posteriorly. Its content includes loose connective tissue, fat, lymphatic vessels, branches of internal thoracic vessel.

Echocardiography and Cardiac CT

• Features of a LV function:
- Valid and accurate
- Reproducible
- Easy to perform and accessible
- Proven in large number of patients
- Clinically understood
- Able to detect meaningful change in an individual patient
• Anatomy test: can be used to check up on the left ventricle functions, e.g. systolic volume. These have to be valid and accurate, reproducible, easy to perform, evidence of success.
• Uses of different modalities: anatomy test needs to put into the context of functional test, e.g. exercise. In situations that required possible treatment, use invasive angiogram.
- X ray: basic test for heart and shape
• Angiograph: investigate coronary artery disease. Catheter into brachial artery and retrograde into the aortic arch (can’t see the effect of atherosclerosis) and but can see enroach into the lumen.
- Complication of angiography: tear down the medial wall of the artery. Block aorta and cause emboli
- In situations that required possible treatment, use invasive angiogram.
• CT coronary angiograms: cardiac 3D CT from multiple images. Need to be fast as heart is moving.
• Diastolic failure: inability to fill etc is the major drive behind the patients symptoms
• Echo sound: provides an image of one dimension of the heart, i.e. a line through the heart to monitor how components along the line will vary across time
- Dense material show up as white or gray while black is blood filled.
- Limited by lung around the heart (filled with air) and no indication of the shape of the heart
• Regional wall assessment: cross section view of the heart to map out locations of problems, e.g. ischemia. From here, depending on the area affect, the coronary artery that supply the area can be investigated for problems.
- CA stenosis requires stenting
• 3D echogram: 3 views of the heart to form a 3D image. No x-ray and non-invasive so safe mode of testing
- left atrial myxoma: commonly seen by echocardiography as a pedunculated mass attached to the interatrial septum
• Doppler assessment: ultrasound targeting a small area such as the flow of blood through a valve to assess stenosis and diastolic filling problems, also speed of movement of ventricle relative to apex etc.

Cardiac CT, Angiography and Stenting

• Angiography: picture of an artery using invasive catheter
- Access points: femoral, brachial, radial artery
• Advantages: cardiac rhythm does not affect angiograph
• Disadvantages:
- Very invasive and expensive
- No x-ray facilities so requires specialist location
- Renal impairment such as diabetics can cause hepatotoxicity as contrast is toxic
- Unpleasant and ionizing problem with X-ray
- Haematoma
- False aneurysm: outpouching of the blood vessel involving defect in the inner two layers.
- Arterial dissection: tear of the line of artery
- Stroke: embolism from angiography can block carotid artery
- death
• Coronary supply dominance:
- Right dominance is 95%, 2.5% for both sides and 2.5% for left dominance
• Widow maker: thrombosis forming at the distal main left coronary artery (instant kill). CABG is the only method of treatment
• Stenting: balloon angioplasty is used to clear the plaque (inflate the balloon). Chlorified wires in a metallic tube to keep the arteries open. However problems of stenting exists:
- Hard to pass the tubes and balloon through turns of the coronary artery
- Foreign body which causes clotting so needs anti-coagulant
- Clotting will cause blockage in 4-5 month if intimal cells does not grow over
- However intimal proliferation will lead to restenosis. After years, the intimal cells become concrete and impossible to remove.
• Grafting: artery is a better choice than vein
- Vein: valves needs to be ripped out for grafting. However vein occlude really quickly and clog up.
- Artery: can tolerate occlusion
• Aspiration catheter: removes the thrombosis
• Advantages of cardiac CT:
- Non-invasive
- Visualize other thoracic pathology
- Image vessel wall as well as lumen
- Pleasant
- Non-specialist facility
- Patient outpatient procedure
• Disadvantages of cardiac CT
- Slow regular (not for arrhythmia like atrial fibrillation)
- Require patient co-operation to lie still
- Contrast media same as angiography
- Problems with heavy calcification causing dense radiography and lumen appears smaller
- Difficult to interpret

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