Cardiac Consequences Of Atheroma

Question 1

What is an atheroma?

Answer 1

Located at the centre of a large plaque formed by nodular accumulation.

Question 2

What are the modifiable risk factors for coronary heart disease?

Answer 2

Smoking
Diabetes mellitus
Hypertension
Obesity and lipids

Question 3

What are the non-modifiable risk factors for coronary heart disease?

Answer 3

Family History
Gender
Age
Ethnicity

Question 4

How does atherosclerosis form?

Answer 4

Endothelial dysfunction with high circulating LDL allows LDL to enter. Endothelial cells release reactive oxygen species, causing LDL to become oxidised, attracting macrophages to engulf it and become foam cells, forming a fatty streak.

This releases IGF-1 and induces smooth muscle migration from the tunica media to the plaque and collagen formation, creating a fibrocartilagenous plaque with a necrotic core. This narrows the lumen so it undergoes remodelling.

The fibrocartilagenous plaque is pro-inflammatory and will eventually rupture through the endothelium and cause thrombus formation, resulting in vessel occlusion and eventual myocardial infarction.

Question 5

What is stable angina?

Answer 5

Chest pain typically crushing and radiating to the left arm and jaw due to commonly an atherosclerotic plaque with a coagulating necrotic centre or hypertrophy of the heart. It is typically worse during exercise and better with rest.

It is more common in women where the coronary arteries spasm and worse at night, with relief using a nitrate spray.

Question 6

What is a stress test?

Answer 6

Evaluation of the pump function of the heart and blood flow through physical exertion or pharmacological stimulation. It is not a highly sensitive or specific diagnostic tool.

Question 7

What does an exercise ECG show?

Answer 7

Patients with coronary heart disease will show ST segment depression, indicating ischaemia or myocardial infarction.

ST segment is the time between ventricular depolarisation and repolarisation.

Question 8

What does a stress ECHO show?

Answer 8

Using an echocardiogram which takes an ultrasound image of your heart before and after exercise.
Healthy patients show increased cardiac muscle size and contractility.
Unhealthy patients show increased cardiac muscle size BUT decreased contractility.

Question 9

What does a myocardial perfusion scan show?

Answer 9

Injection of radioactive isotope into patient shortly after exercise and also during prolonged rest to assess dispersion of oxygenated blood flow. Unhealthy patients will show insufficient perfusion to certain areas of the heart.

Question 10

What is acute coronary syndrome?

Answer 10

Medical emergency due to disruption of blood flow to cardiac muscle where patient experiences:
Crushing central chest pain which radiates to the jaw and left arm, with impending doom, vomiting and diaphoresis (sweating)

This includes STEMI and Non-STEMI.

Question 11

What are the differentials for acute coronary syndrome?

Answer 11

Myocardial infarction
Pericarditis and endocarditis
Anxiety
Pericardial effusion
Pulmonary embolism
Oesophageal rupture

Question 12

What is a STEMI?

Answer 12

Complete and prolonged occlusion of the coronary artery due to the rupturing and thrombus formation of an atherosclerotic plaque which typically occurs in the left anterior descending artery.

It is diagnosed with an ECG, showing ST elevation and T wave peak. Papillary muscles can become damaged and lead to mitral valve regurgitation or prolapse.

Question 13

What is a Non-STEMI?

Answer 13

Partial/temoprary occlusion of the coronary artery with ischaemia due to atherosclerotic plaque with a thrombus, resulting in a subendocardial infarct.

Patients will have a normal ECG, or minor T wave inversions or ST depression. It is diagnosed using troponin I and troponin T markers.

Question 14

What are the bio markers for heart attack?

Answer 14

Elevated troponin levels, which are responsible for regulating muscle contractions and high levels indicates cardiac muscle damage. There must be a rise or fall in Troponin, measured a few hours apart.

It is a sensitive but NOT specific marker of heart attack.

Question 15

What is the structure of troponin?

Answer 15

Consists of:
Troponin C which regulates Ca2+
Troponin I which stops myosin binding to actin on relaxed muscle
Troponin T for attachment to tropomyosin.

Question 16

What are causes for high troponin, unrelated to myocardial infarction?

Answer 16

Pulmonary embolism
Hypertension
Septicaemia
Subarachnoid haemorrhage

Question 17

What is unstable angina?

Answer 17

Chest pain occurring at rest. This is due to partial occlusion of the coronary artery as a result of an unruptured plaque which results in ischaemia. Unstable angina do not present with abnormal ECG apart from mild T inversion and can typically progress to NON-STEMI if untreated.

Typically no change to the cardiac enzyme markers.

Question 18

Which coronary artery is dominant?

Answer 18

Right coronary artery that gives off the posterior descending artery. The right coronary artery is the second most common site where myocardial infarctions occur, after the LAD in the left coronary artery.

Question 19

What is a complication of acute myocardial infarction?

Answer 19

Electrolyte imbalances and ischaemia that damages cardiac muscle can lead to:
->Death due to heart arrythmia from ventricular fibrillation
->Long term heart failure after the AMI.
-> Coagulative necrosis of cardiac tissue
-> Myocardial rupture

Question 20

How is an acute myocardial infarction treated?

Answer 20

Morphine for pain
Anti-platelets such as aspirin and clopidogrel
Low molecular weight heparin
Anti-ischaemic drugs such as beta blockers and nitrates

Question 21

What is the action of LMWH?

Answer 21

It activates anti-thrombin for inactivation of thrombin (factor IIa), factor Xa and factor IXa.

Question 22

What is a procedure to treat narrowing of coronary arteries in MI?

Answer 22

Primary Percutaneous coronary intervention, which is deploying a coronary stent to treat narrowing of the coronary arteries.
Intravenous infusion of thrombolytic drugs to dissolve the clot.

Question 23

What is myocardial rupture?

Answer 23

Rare complication that occurs within 2 weeks post-myocardial infarction, occurring in the area with the greatest sheer stress of blood flow. The weakened vessel wall is prone to tear and allow leakage of blood, with a hinge joint forming between functioning and non-functioning regions.

Question 24

What are the risk factors for myocardial rupture?

Answer 24

Female sex
Hypertension
First heart attack
Elderly
Diffuse atherosclerosis

Question 25

What happens when there is interventricular septum rupture?

Answer 25

High pressure/volume blood from the left ventricles moves to enter the low pressure/volume right ventricles that is pumping to the heart, resulting in pulmonary artery hypertension, oedema and right sided heart failure.

Question 26

What is the presentation of myocardial rupture of the interventricular septum?

Answer 26

Haemodynamic compromise: cardiogenic shock where hypotension is due to cardiac muscle damage following AMI.

Respiratory failure due to pulmonary artery hypertension causing right sided heart failure

Loud and harsh holosystolic murmur over the lower left and right sternal borders.

Question 27

What is the blood supply to the posteromedial papillary muscle?

Answer 27

Posterior descending artery, a branch of the right coronary artery.

Question 28

What is the blood supply to the anteromedial papillary muscle?

Answer 28

Left anterior descending artery and left circumflex artery.

Question 29

What happens when there is papillary muscle rupture?

Answer 29

Occurs more commonly in the posteromedial papillary muscle and results in mitral valve regurgitation, pulmonary oedema and cardiogenic shock. There is holosystolic murmur on auscultation.

Question 30

What is a holosystolic murmur?

Answer 30

Murmur due to mitral or tricuspid valve regurgitation.

Question 31

What is the presentation of left ventricular dysfunction?

Answer 31

Insufficient blood delivery to organs results in:
Orthopnoea and paroxysmal nocturnal dyspnoea
Shortness of breath
Peripheral oedema

Question 32

How does left ventricular dysfunction diagosed?

Answer 32

Left ventricular dysfunction is when the heart’s pumping ability is disrupted and is divided into systolic heart failure and diastolic heart failure. It can be diagnosed using an echocardiogram, stress test, ECG.

Question 33

What are the classifications of left ventricular dysfunction?

Answer 33

Based on appearance and severity symptom manifestation on exertion and rest.

Question 34

What is a left ventricular aneurysm?

Answer 34

Occurs following a myocardial infarction, malignant arrythmia or heart failure.

It begins as a region of dead cardiac muscle which creates a weakened bulge that herniates outward in systole. There is a risk of thrombus formation which may rupture and leakage of blood in the pericardial sac and result in cardiac tamponade so anticoagulant treatment is important.

Question 35

What is the cause of sudden cardiac death?

Answer 35

Loss of all heart activity within one hour of symptom onset, typically caused by an arrythmia such as Bradycardia or tachyarrythmia.

Question 36

What is associated with early/sudden cardiac death?

Answer 36

Occurs during STEMI, typically due to arrythmia of the ventricles, such as bradyarrythmia or tachyarrythmia.

Question 37

What causes late cardiac death?

Answer 37

Heart failure.

Question 38

How can the heartbeat be reformed in arrythmia?

Answer 38

Automatic implantable cardioverter-defibrillator: Delivers electrical impulses to the ventricles of the heart when sensing significant change in the heart’s rhythm, ideal for patients with left ventricular dysfunction.

Question 39

What is a pacemaker?

Answer 39

Corrects irregular heart rhythm by generating electrical impulses to act on the SAN.