Ischaemic Heart Disease

Question 1

Myocardial ischaemia is?

Answer 1

It’s a pathological condition that occurs when there is insufficient blood flow to meet metabolic demands of the beating heart

Question 2

As myocardial oxygen demand increases, it must be paralleled by an?

Answer 2

By an increase in myocardial blood flow, because coronary arteriovenous oxygen extraction is near maximal at rest

Question 3

List major determinants of myocardial oxygen consumption

Answer 3

1. Heart rate
2. Left ventricular (LV) wall stress
3. Contractility

Question 4

Left ventricular wall stress is dependent on?

Answer 4

LV volume, and LV afterload or systolic blood pressure

Question 5

What increases determinants of oxygen consumption?

Answer 5

Exercise and emotional stress

Question 6

In a normal heart, coronary blood flow increases up to _____ to meet increased oxygen consumption demand.

Answer 6

May increase up to five fold

Question 7

When there is an _____ in a coronary artery, it may limit the ability of the coronary circulation to increase flow.

Answer 7

Atherosclerotic stenosis

Question 8

Flow limitation during exercise occurs when ____ of the lumen diameter is obstructed.

Answer 8

70%

Question 9

A stenosis of ____ will limit flow at rest.

Answer 9

90%

Question 10

Stenosis of ______ lumen diameter do not usually limit flow during exercise.

Answer 10

<50%

Question 11

Describe pathophysiology of angina (chest pain)

Answer 11

• Vasospasm fixed stenosis thrombus leads to decreased coronary blood flow which leads to angina (chest pain)
• Increased heart rate, increased contractility, increased afterload and increased preload leads to increased oxygen consumption, leading to angina (chest pain)

Question 12

Demand ischaemia typically occurs during exercise in patients with a coronary stenosis of ______ and is quickly relieved by rest.

Answer 12

70% or greater

Question 13

Supply iscahemia occurs when?

Answer 13

Occurs at rest when an artery occludes or suddenly develops a stenosis of 90% or greater

Question 14

Severe supply ischaemia with complete occlusion of an epicardial coronary artery for longer than 30 minutes will result in?

Answer 14

Myocardial infarction (myocardial cell death)

Question 15

Within a few seconds of ischaemia, metabolism switches from _____ to _____ with production of lactic acid.

Answer 15

From Aerobic utilisation of fatty acids to anaerobic glycolysis with production of lactic acid

Question 16

Anaerobic glycolysis (metabolism) occurring in ischaemia leads to a fall in?

Answer 16

Fall in high-energy phosphate production

Question 17

High-energy phosphate production decrease causes failure of?

Answer 17

Failure of both contraction and active relaxation , which results in elevation of LV-end-diastolic pressure and breathlessness

Question 18

Ischaemia-caused decrease of high-energy phosphate production and anaerobic glycolysis leads to less energy, which is needed for?

Answer 18

Needed for available for membrane sodium/potassium pump, potassium leaks out of cells, raising resting membrane potential and reducing action potential size and duration.

Question 19

ECG change in subendocardial ischaemia

Answer 19

ST segment depression

Question 20

ECG change in transmural ischaemia

Answer 20

ST segment elevation

Question 21

Elevation and depression of ST segments are relative to isoelectric segments in the?

Answer 21

In the TP and PQ periods

Question 22

A late event in myocardial ischaemia is the generation of?

Answer 22

Generation of chest pain (Angina pectoris)

Question 23

Pain-producing stimulus is probably _____ in myocardial ischaemia

Answer 23

Adenosine

Question 24

Sensation of pain is carried by sympathetic afferents which synapse between spinal segments __________ producing referred pain in the retrosternal area, typically radiating to left arm or neck.

Answer 24

C8 to T4

Question 25

Many attacks of ischaemia are not accompanied by?

Answer 25

Anginal pain (silent ischaemia)

Question 26

Peripheral vascular disease is a term used to describe?

Answer 26

Describes symptomatic chronic arterial occlusion, usually in the lower limbs

Question 27

Peripheral vascular disease is a disease that usually follows?

Answer 27

Follows a slowly progressive course from intermittent pain on walking to constant severe pain, ulceration, gangrene and limb loss

Question 28

Principal symptom of peripheral vascular disease?

Answer 28

Muscle pain due to intermittent claudication

Question 29

Which muscles are most commonly affected in early stage of peripheral vascular disease?

Answer 29

Calf muscles on running or walking, though depending on the anatomical distribution of the arterial occlusive disease, other sites such as buttock muscles or thighs may be the first to cause pain

Question 30

Arterial disease is usually due to?

Answer 30

Atherosclerosis

Question 31

Arterial disease pain typically does what?

Answer 31

Typically fades away when patient rests for several minutes, allowing the flow of oxygenated blood to better match the needs of the muscles to return to aerobic metabolism.

Question 32

As patient rests due to pain from peripheral vascular disease, describe what happens to blood pressure in the arteries distal to the obstruction:

Answer 32

BP has fallen in parallel with the onset of pain, rises again to the pre-exercise levels as the blood flow catches up with the metabolic requirements of the vascular bed.

Question 33

Pain may appear at rest as peripheral vascular disease becomes more severe. Why?

Answer 33

Large due to ischaemia of peripheral nerves. Patient may notice altered sensation in the feet and toes, worse after walking and burning numbness may become the dominant symptom as the nerves are subjected to constant ischaemia.

Question 34

Rest pain of peripheral vascular disease is worse at night and may be relieved for short periods by getting up and walking around. What is the final step/process of peripheral vascular disease?

Answer 34

Tissue loss secondary to minor trauma, infection or ischaemic gangrene completes the clinical course.

Question 35

Nature of the pain is best confirmed on a patient by?

Answer 35

Walking with the patient until the pain appears, and the examination repeated then.

Question 36

Careful physical examination including palpation and auscultation of the arterial tree of the lower limbs will demonstrate?

Answer 36

Demonstrate level of the proximal arterial occlusion or stenosis, and this is most commonly in the femoro-popliteal arterial segment.

Question 37

Which artery is the only artery blocked in the patient who presents with intermittent claudication?

Answer 37

Femoro-popliteal arterial segment

Question 38

Doppler pressure studies measures what?

Answer 38

They are most informative and accurate when coupled with treadmill exercise, with systolic measurements performed before and after exercise until the ankle arterial pressure returns to the pre-exercise level.

These may be compared with the brachial artery systolic pressure to generate a ratio called the ankle/brachial index

Question 39

Patent arterial segments is performed by?

Answer 39

Angiography by direct femoral puncture or via intra-arterial catheters

Question 40

Flow in open vessel assessment is performed by?

Answer 40

Arterial duplex scanning of the lower limb arteries.