Ischaemic Heart Disease Flashcards
Define ischaemic heart disease
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 (acute coronary syndrome) 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
Summarise the epidemiology of ischaemic heart disease
COMMON
Prevalence: > 2 %
More common in males
Annual incidence of MI in the UK ~ 5/1000
Explain the aetiology/risk factors of ischaemic heart disease
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
Atherosclerosis pathophysiology
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
Risk Factors
Male
Diabetes mellitus
Family history
Hypertension
Hyperlipidaemia
Smoking
Recognise the presenting symptoms of ischaemic heart disease
ACS
STABLE ANGINA
ACS
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
Stable Angina
Chest pain brought on by exertion and relieved by rest
Recognise the signs of ischaemic heart disease on physical examination
Stable Angina
-Check for signs of risk factors
ACS
- 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)
Identify appropriate investigations for ischaemic heart disease
Bloods ecg CXR Exercise ecg Radionuclide Myocardial Perfusion Imaging (rMPI) Echocardiogram Pharmacological Stress Testing Cardiac Catheterisation/Angiography Coronary Calcium Scoring
Bloods
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)
ECG
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
CXR
Check for signs of heart failure
Exercise ECG
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
