Ischaemic Heart Disease

Question 1

What is the definition of ischaemic heart disease?

Answer 1

Characterised by decreased blood supply to the heart muscle resulting in chest pain (angina pectoris). May present as stable angina or acute coronary syndrome.

ACS can be further subdivided into:

• Unstable angina - chest pain at rest due to ischaemia but without cardiac injury
• NSTEMI
• STEMI - ST elevation with transmural infarction

NOTE: MI = cardiac muscle necrosis resulting from ischaemia

Question 2

What is the epidemiology of ischaemic heart disease?

Answer 2

COMMON

Prevalence: > 2 %

More common in males

Annual incidence of MI in the UK ~ 5/1000

Question 3

What is the aetiology of ischaemic heart disease?

Answer 3

Angina pectoris occurs when myocardial oxygen demand exceeds oxygen supply

This is usually due to atherosclerosis

Rarer causes of angina pectoris include coronary artery spasm (e.g. induced by cocaine), arteritis and emboli

Question 4

What is the pathophysiology of atherosclerosis?

Answer 4

Endothelial injury leads to migration of monocytes into the subendothelial space

These monocytes differentiate into macrophages

Macrophages accumulate LDL lipids and become foam cells

These foam cells release growth factors that stimulate smooth muscle proliferation, production of collagen and proteoglycans

This leads to the formation of an atherosclerotic plaque

Question 5

What are the risk factors for ischaemic heart disease?

Answer 5

Male

Diabetes mellitus

Family history

Hypertension

Hyperlipidaemia

Smoking

Question 6

What are the presenting symptoms of ACS?

Answer 6

Acute-onset chest pain

Central, heavy, tight, crushing pain

Radiates to the arms, neck, jaw or epigastrium

Occurs at rest

More severe and frequent pain that previously occurring stable angina

Associated symptoms:

• Breathlessness
• Sweating
• Nausea and vomiting
• SILENT INFARCTS occur in the elderly and diabetics

Question 7

What are the presenting symptoms of stable angina?

Answer 7

Chest pain brought on by exertion and relieved by rest

Question 8

What are the signs of ACS upon physical examination?

Answer 8

There may be NO CLINICAL SIGNS

Pale

Sweating

Restless

Low-grade pyrexia

Check both radial pulses to rule out aortic dissection

Arrhythmias

Disturbances of BP

New heart murmurs

Signs of complications (e.g. acute heart failure, cardiogenic shock)

Question 9

What are the signs of stable anginas?

Answer 9

Check for signs of risk factors

Question 10

What are the appropriate investigations for ischaemic heart disease?

Answer 10

• Bloods
• ECG
• CXR
• Exercise ECG
• Radionuclide Myocardial Perfusion Imaging (rMPI)
• Echocardiogram
• Pharmacological Stress Testing
• Cardiac Catheterisation/ Angiography
• Coronary Calcium Scoring

Question 11

What would you expect in the bloods of a patient with IHD?

Answer 11

FBC

U&Es

CRP

Glucose

Lipid profile

Cardiac enzymes (troponins and CK-MB)

Amylase (pancreatitis could mimic MI)

TFTs

AST and LDH (raised 24 and 48 hours post-MI, respectively)

Question 12

What would you expect in the ECG of a patient with IHD?

Answer 12

Unstable Angina or NSTEMI:
- May show ST depression or T wave inversion

STEMI:

• Hyperacute T waves
• ST elevation (> 1 mm in limb leads, > 2 mm in chest leads)
• New-onset LBBB

Later changes:

• T wave inversion
• Pathological Q waves

Relationship between ECG leads and the side of the heart

• Inferior: II, III, aVF
• Anterior: V1-V5/6
• Lateral: I, aVL, V5/6
• Posterior: Tall R wave and ST depression in V1-3

Question 13

What would you expect in the CXR of a patient with IHD?

Answer 13

Check for signs of heart failure

Question 14

What would you expect in the exercise CXR of a patient with IHD?

Answer 14

Indications
- Patients with troponin-negative ACS or stable angina with a high pretest probability of coronary heart disease
- Pretest probability is based on characteristics of chest pain, cardiac risk factors, age and gender
NOTE: digoxin is associated with giving a false-positive result

Results:
- Positive Test: > 1 mm horizontal or downsloping ST depression measured at 80 ms after the end of the QRS complex
- Failed Test: failure to achieve at least 85% of the predicted maximal heart rate (220-age) and otherwise negative findings (no chest pain or ECG changes)
NOTE: beta-blockers reduce heart rate and so should be stopped before the test
- Resting ECG Abnormalities: e.g. pre-excitation syndrome, > 1 mm ST depression, LBBB or pacemaker ventricular rhythm

Question 15

What would you expect in the rMPI of a patient with IHD?

Answer 15

Uses Technetium-99m sestamibi or tetrofosmin

Can be performed under stress or at rest

Stress testing shows low uptake in ischaemic myocardium

Question 16

What would you expect in the echo of a patient with IHD?

Answer 16

Measures left ventricular ejection fraction

Exercise or dobutamine stress echo may detect regional wall motion abnormalities

Question 17

What would you expect in the pharmacological stress testing of a patient with IHD?

Answer 17

This is used in patients who are unable to exercise

Pharmacological agents can be used to induce a tachycardia, such as:

• Dipyridamole
• Adenosine
• Dobutamine

These agents are used in conjunction with various imaging modalities (e.g. rMPI, echocardiography) to detect ischaemic myocardium

NOTE: Dypiridamole and adenosine are contraindicated in AV block and reactive airway disease

Question 18

What would you expect in the angiography of a patient with IHD?

Answer 18

Performed if ACS with positive troponin or if high risk on stress testing

Question 19

What would you expect in the coronary calcium scoring of a patient with IHD?

Answer 19

Uses specialised CT scan

May be useful in outpatients with atypical chest pain or in acute chest pain that isn’t clearly due to ischaemia