CVS HARC booklet

Question 1

Answer 1

Question 2

What is the features/differences in left and right atria?

Answer 2

Left atrium: receives the 4 pulmonary veins. Leads into the left ventricle via the mitral valve. Situated behind the right atrium.

Right atrium: receives the superior and inferior vena cava. Leads into the right ventricle via the tricuspid valve. Forms the right border of the heart.

Question 3

Compare the internal structure of the auricles and the atria. Why are they different? (Hint: refer to your knowledge of the embryology of the heart).

Answer 3

The atria are smooth walled whereas the auricles are ridged. The difference is due to embryological origin.

The right atrium is derived from the smooth walled sinus venosus and the left atrium derived from the pulmonary veins.

The atrial appendages are derived from the primitive atria which resemble the appearance of the ridged ventricles rather than the smooth walled veins.

On the right, the transition between the atrium and auricle is demarcated by the crista terminalis.

There is no obvious demarcation on the left, as the left atrium lacks a structure analogous to the crista terminalis.

Question 4

Answer 4

Question 5

: Compare the shape of the left and right ventricle cavities and the associated chamber walls. How are they different and what functional implication does this have?

Answer 5

The left ventricular cavity is much smaller and narrower than the right, and the left has a considerably thicker wall. The left ventricle can thus produce much greater ejection force and pressure – important in maintaining a suitable systemic blood pressure under different demands.

Question 6

What are the similarities between AV valves and SL valves?

Answer 6

• They all have multiple cusps, which when apposed prevent regurgitation of blood.
• Increased pressure of blood upstream to the valves allows them to open.

Question 7

What are the differences between AV valves and SL valves?

Answer 7

The anatomy of the cusps is very different.

• The AV valves have very large, thin, sheet-like cusps. The semilunar valve cusps are smaller, crescent shaped cusps.
• The semilunar valves generally take attachment to the vessel walls, whereas the AV valves are secured to a fibrous ring surrounding the AV orifice.
• The free margins of the superior edge of the semilunar valve cusps are thickened centrally to form nodules. The free margins of the AV valve cusps attach to papillary muscles via chordae tendinae. Chordae tendinae from at least two papillary muscles attach to each cusp, preventing separation of the cusps during contraction.
• The closure of the semilunar valves is a passive process, due to the pressure of blood starting to flow back as the heart relaxes. The closure of the AV valves is an active process, resulting from the contraction of the papillary muscles.

Question 8

Answer 8

Question 9

: What is the function of the papillary muscles?

Answer 9

Papillary muscles attach to the cusps of the atrioventricular valves via the chordae tendinae. When they contract, they pull on the chordae tendinae and therefore valve cusps preventing the valves from inverting when the ventricles contract. As each valve cusp is connected to two papillary muscles, the contraction of the papillary muscles draws the cusps togethe

Question 10

What is the cardiac skeleton and its importance?

Answer 10

This is a collection of dense, fibrous connective tissue in the form of four rings with interconnecting areas in a plane between the atria and the ventricles. The four rings of the cardiac skeleton surround the two atrioventricular orifices, the aortic orifice and opening of the pulmonary trunks.

The rings serve as a point of attachment for the valve leaflets and help to maintain the integrity of the orifices. The cardiac skeleton is also important in the conduction cycle of the heart

Question 11

: What is housed in the aortic sinuses?

Answer 11

The left and right aortic sinuses are found between the left and right aortic valve cusps and the wall of the ascending aorta. They are pocket-like spaces above the valve cusps that fill with blood and direct it to the left and right coronary arteries, the openings of which are found within the left and right aortic sinuses respectively.

Question 12

Answer 12

Question 13

What would be the effects of mitral valve insufficiency on ventricular anatomy and function?

Answer 13

Blood would regurgitate back into the left atrium from the left ventricle. This increases the pre-load (stretching of cardiac myocytes) leading to hypertrophy of the left ventricle hypertrophy, and dilatation of the left atrium, increased pulmonary pressure, and pulmonary oedema

Question 14

: What would be the effects of aortic stenosis on ventricular anatomy and function?

Answer 14

Aortic orifice narrowing due to stiffening of the aortic valve. This results in restricted blood flow from the left ventricle into the aorta. There is therefore a reduction in left ventricular emptying and reduced cardiac output. This causes pressure overload of the LV. The LV is forced to work harder to pump blood through the valve and the LV therefore undergoes concentric hypertrophy.

Question 15

How would a patient present with aortic stenosis?

Clinical intervention?

Answer 15

Patient may present with angina, shortness of breath (particularly during exercise), syncope, fatigue, oedema.

Possible interventions – initially intra-aortic balloon pump; ultimately valve replacement

Question 16

: Describe the anatomy of left-sided dilated cardiomyopathy (DCM).

Answer 16

Dilated cardiomyopathy is a disease of heart muscle where it becomes stretched and thin and unable to pump blood efficiently. It may be caused by an inherited genetic change or by heart valve disorders, viral infections, uncontrolled hypertension. With left-sided DCM, there is an increase in left ventricular end-diastolic and end-systolic volumes. The heart walls are thinned and there is a change in geometry to a more spherical, less elongated shape. It is usually associated with a continuous decline in ejection fraction. The heart is therefore less efficient and clinical features include fatigue, shortness of breath, exercise intolerance, oedema.

Question 17

DCM: What are the possible non-invasive and invasive interventions to help regain normal cardiac function?

Answer 17

Non-invasive treatment: ACE inhibitors, diuretics Invasive treatment: pacemaker, left ventricular assist device (LVAD), Batista procedure (removal of a segment of LV muscle but no longer recommended)

Question 18

Answer 18

Question 19

The ________ layer of pericardium is continuous with the tunica _______ of the great vessels superiorly and inferiorly its base is attached to the central tendon of the diaphragm. The _____ and _______ layers of serous pericardium are continuous around the roots of the great vessels.

Answer 19

The fibrous layer of pericardium is continuous with the tunica externa of the great vessels superiorly and inferiorly its base is attached to the central tendon of the diaphragm. The parietal and visceral layers of serous pericardium are continuous around the roots of the great vessels.

Question 20

: What are the functions of the pericardium?

Answer 20

The fibrous pericardium is tough and inelastic so helps to prevent the heart overfilling with blood, and also tethers the heart to surrounding structures to give it support. The serous fluid contained between the visceral and parietal layers of pericardium prevents friction.

Question 21

Where are the sternopericardial ligaments and pericardiophrenic ligaments located?

Answer 21

Sternopericardial ligaments are between the sternum and fibrous pericardium. Pericardiophrenic ligaments are between the diaphragm and fibrous pericardium.

Question 22

There are two points of reflection of pericardium (where the parietal and visceral serous layers are continuous:

What are they?

Answer 22

• One superiorly surrounding the arteries – aorta and pulmonary trunk
• One more posteriorly, surrounding the veins – superior and inferior vena cava and pulmonary veins

Question 23

the two points of reflection of pericardium result in the formation of two pericardial sinuses:

What are they

Answer 23

Transverse sinus

Oblique sinus

Question 24

What is transverse sinus?

Answer 24

: tunnel-shaped passage between the pericardial reflections around the arteries anteriorly and veins posteriorly. Its boundaries are the ascending aorta and pulmonary trunk anteriorly, the superior vena cava posteriorly, and the left atrium inferiorly.

Question 25

What is oblique sinus?

Answer 25

blind-ended passage formed behind the left atrium due to the reflection of pericardium between the heart and pulmonary veins.

Question 26

What is the significance of the transverse sinus surgically?

Answer 26

When the pericardium is opened anteriorly during surgery, a finger placed in the transverse sinus separates arteries from veins. Clamps or ligatures are placed in this area to allow for the use of a coronary bypass machine in order to perform open heart surgery.

Question 27

Answer 27

Question 28

: What is the nervous innervation of the pericardium?

Answer 28

Phrenic nerve (C3-C5)

Question 29

Using your knowledge of the root values of the nerve(s) involved, where would the pain be referred to?

nervous innervation of the pericardium

Answer 29

Supraclavicular region, ipsilateral side

Question 30

What is pericarditis?

Answer 30

Pericarditis is inflammation of the pericardium.

Question 31

Pericarditis: cause and presentation?

Answer 31

It may be caused by infection (viral, bacterial, fungal), systemic illness (e.g. chronic renal failure), following a myocardial infarction.

Patients may present with chest pain, usually central, that is relieved by sitting forward. Presence of a pericardial friction rub is a classic clinical sign due to the inflamed layers of pericardium rubbing against each other.

Question 32

What is pericardial effusion?

Answer 32

Pericardial effusion is a collection of fluid within the pericardial cavity. The normal volume of pericardial fluid is approximately 20-49ml.

Question 33

Percadial effusion cause?

Answer 33

Increased volume of pericardial fluid can accumulate due to an imbalance between production and reabsorption of serous fluid. This may be a complication of pericarditis due to an inflammatory disease or may occur with congestive heart failure.

Question 34

: What is cardiac tamponade?

Answer 34

As the fibrous pericardium is tough and inelastic, it cannot expand easily. It is a closed sac. Rapid accumulation of excess fluid in the pericardial cavity (pericardial effusion) can therefore compress the heart and this pressure hinders the function of the heart. The heart is unable to fill properly due to external pressure and cardiac output is therefore reduced.

Question 35

What are the clinical features of cardiac tamponade?

Answer 35

Clinical features include dyspnea, low BP, and distant heart sounds. It is usually confirmed with an ultrasound. Ewart’s sign is also a good indication – a dullness to percussion in the left subscapular region, due to the effusion being large enough to compress the left lower lobe of the lung.

Question 36

How is cardiac tamponade treated?

Answer 36

It is treated by pericardiocentesis, a large needle that is inserted into the pericardial cavity under ultrasound guidance to reduce pressure. The needle can be inserted into one of 2 places:

o Parasternal approach: through the left 5th or 6th intercostal space. Here the cardiac notch of the left lung means that the lung or pleura won’t be hit.

o Subxiphoid approach: to the left of the xiphoid process and direct the needle posterosuperiorly. This route passes through the diaphragm therefore avoiding the lung and pleura. Care must be taken to avoid the internal thoracic vessels.

If time allows, an emergency thoracostomy may be performed. This involves incising the pericardial sac to immediately relieve pressure.

Question 37

Answer 37

Question 38

Answer 38

Question 39

What is the role of the coronary sinus and what supplies it?

Answer 39

The coronary sinus receives deoxygenated blood from the cardiac veins that are draining the walls of the heart. The coronary sinus then returns the deoxygenated blood to the right atrium.

Question 40

Match the definitions to the type of heart dominance they are describing.

Answer 40

Question 41

: Which type(s) of coronary circulation do you think is preferable to survival?

Right dominance or left dominance or co dominance

Answer 41

Right dominance or co-dominance as the interventricular septum will have a blood supply from both coronary arteries. This means occlusion of one coronary artery would not prevent this area from being supplied with oxygen. In a left-dominant individual, the blood supply of the interventricular septum is solely from the left coronary artery, therefore an occlusion of the left coronary artery would result in rapid ischaemia of the entire interventricular septum and surrounding tissues. This would result in a massive myocardial infarction and likely death.

Question 42

: What is angina?

Causes?

Answer 42

Angina is ischaemia of the myocardium that falls short of inducing cellular necrosis that defines myocardial infarction.

It results from the narrowing of coronary arteries and therefore less oxygen being delivered to the myocardium. A reduction in oxygen availability results in lactic acid accumulation and pH is reduced in affected areas. Lactic acid stimulates pain fibres, and it is this that causes the pain felt with angina. The chest pain is described as heavy or tight and occurs on exertion (when there is increased demand for oxygen), but it is relieved at res

Question 43

Why are you more at risk from suffering angina pain after eating a large meal?

Answer 43

You are more at risk of suffering from angina pain after eating a large meal, as blood is diverted to the GI tract and thus is not available for coronary circulation to relieve the oxygen debt felt by the myocardial cells.

Question 44

How is angina treated?

Answer 44

Angina can be treated by sublingual nitro-glycerine. This dilates coronary arteries increasing blood flow to the heart and decreasing the workload of the heart (as there is less resistance in peripheral vessels). Angina is a warning sign that the coronary arteries are compromised and lifestyle changes need to be made to reduce the risk of myocardial infarction

Question 45

Why would slow progressive coronary artery disease have better outcomes than a sudden blockage of a coronary artery?

Answer 45

If the disease progresses slowly, collateral circulation has time to develop, as increasing volumes of blood are gradually diverted through it. When the affected artery is completely blocked, the collateral circulation may then be sufficient to adequately perfuse the myocardium thereby preventing a myocardial infarction

Question 46

A blockage may arise in one or more coronary arteries requiring a bypass. Draw in vessels on the handout provided to represent a triple heart bypass.

Answer 46

Question 47

Which vein is usually harvested for a coronary artery bypass and why?

Can you name an artery that is sometimes harvested?

Answer 47

Great saphenous vein is used because:

• Its diameter is equal to or greater than the coronary arteries.
• It can easily be dissected out of the lower limb.
• It has lengthy portions that don’t have any valves in, but even if a portion with a valve is used, reversing the implanted segment renders the valve functionless.

Radial artery

Question 48

What artery of the chest wall is sometimes anastomosed to the coronary vessels to replenish blood supply to the heart?

Answer 48

Internal thoracic artery (internal mammary artery). It runs closely to the anterior interventricular artery

Question 49

Answer 49

Question 50

What is tunica media?

Answer 50

Middle fibromuscular layer. Smooth muscle functions to regulate the vessel diameter. Elastic fibres allow the vessel to stretch thereby tolerating changes in pressure as the heart contracts.

Question 51

What is tunica externa / adventitia?

Answer 51

Outer connective tissue sheath, containing collagen and elastin. Typically blends with neighbouring tissues which acts to stabilise and anchor the blood vessel.

Question 52

What is tunica intima?

Answer 52

Innermost layer. Thin, composed of a single layer of endothelial cells. Acts as a barrier between the blood and the rest of the vessel (or tissue in capillaries).

Question 53

What is the general relative composition of each layer in a large artery, an arteriole, a capillary, and a large vein?

Answer 53

• Large artery: relatively thick tunica media due to the large presence of elastic fibres to withstand the changes in blood pressure.
• Arteriole: tunica media is composed of only 1-2 layers of smooth muscle cells. Arterioles are considered the primary site of vascular resistance and alter their diameter to help regulate BP, distribution of blood etc.
• Capillary: consists only of tunica intima, therefore capillary walls consist of a single layer of endothelial cells, surrounded by a supporting basal lamina of connective tissue. Important site of exchange between the blood and surrounding tissue cells.
• Large vein: large tunica externa to support the vessel and prevent collapse, as the veins have less smooth muscle in the tunica media.

Question 54

The diameter of blood vessels is regulated by the __________ division of the autonomic nervous system.

Answer 54

The diameter of blood vessels is regulated by the sympathetic division of the autonomic nervous system.

Question 55

Answer 55

Question 56

The aortic sinus and carotid sinus relay information regarding the stretch of the vessels to the cardiovascular centre (CVC) in the medulla and pons.

• The_____________ nerve carries the information to the CVC from the aortic sinus.
• The ______________nerve carries the information to the CVC from the carotid sinuses.

Answer 56

• The vagus nerve carries the information to the CVC from the aortic sinus.
• The glossopharyngeal nerve carries the information to the CVC from the carotid sinuses.

Question 57

BP: after the nerves are stimulated what happens next?

Answer 57

The CVC in the medulla then transmits information via the autonomic nervous system to the blood vessels to bring about the appropriate response (↑ blood pressure or ↓ blood pressure) necessary to maintain homeostasis.

Question 58

What is an aneurysm?

Answer 58

An aneurysm is a weakening of the arterial wall leading to a localised bulging. An aneurysm is most commonly caused by atherosclerosis but any abnormality that weakens the tunica media can predispose a patient to an aneurysm. Aneurysms may rupture, compress neighbouring structures, or lead to a thrombus or embolus.

Question 59

: Name the 3 types of aneurysm on the diagram below.

Answer 59

Question 60

Name 3 factors that facilitate venous return to the heart.

Answer 60

• Presence of valves to prevent backflow
• Neighbouring muscle contraction (“muscle pump mechanism”)
• Respiratory activity. During inspiration, negative intrathoracic pressure and a decrease in right atrial pressure promotes venous return. The opposite happens on expiration.
• Increased intra-abdominal pressure e.g. contraction of the diaphragm or abdominal wall muscles (related to respiration), Valsalva manoeuvre. Increased intraabdominal pressure compresses the IVC forcing blood upwards into the right atrium of the heart.
• Gravity. When a person stands up, pressure in the right atrium decreases and venous pressure in the limbs increases. This creates a pressure gradient that promotes venous return.

Question 61

What are varicose veins?

What causes varicose veins?

Answer 61

Varicose veins are swollen, tortuous veins that lie just beneath the skin, usually in the legs.

Varicose veins occur as veins become inelastic, which can cause their valves to become incompetent. The valves of the venous system may become incompetent when veins are overstretched by excess venous pressure lasting for an extended period e.g. during pregnancy or in someone who stands all the time. As the vein diameter increases but the size of the valve leaflets does not change, the valve leaflets can no longer meet completely. This results in blood not returning to the heart as efficiently and the veins become engorged with blood due to gravity. The veins dilate due to the pooling of blood, which further exacerbates the loss of elasticity of the vessel walls, stretching of the veins, and valve failure.

Question 62

Why does varicose veins occur more commonly in the superficial veins rather than the deep veins?

Answer 62

Superficial veins are more susceptible as they do not have neighbouring muscles to help “pump” blood back to the heart, therefore they are at an increased risk of blood pooling.

Question 63

Deep vein thrombosis (DVT) usually occurs in the lower limb, pelvis, or iliac veins.

• What are some of the risk factors for DVT?

Answer 63

Risk factors for DVT include varicose veins, prolonged immobility, surgery, pregnancy

Question 64

How can a clot in the lower limb cause death?

Answer 64

If DVT is untreated, death could occur due to a pulmonary embolus. Fragment of the blood clot in the vein of the lower limb breaks free and travels to the heart and lungs.