JC 06 (Medicine) - Ischaemic heart disease, Angina pectoris Flashcards
(48 cards)
6 pathophysiological processes that cause MI
- Critical coronary stenosis
- Vascular Inflammation
- Coagulopathies
- Vasospasm
- Microvascular dysfunction
- Endothelial dysfunction
Explain the pathophysiological changes in epicardial coronary arteries that lead to myocardial ischemia
Insufficient oxygen supply to myocardial tissue by 2 mechanisms:
- Atherosclerotic disease
- Stable plaque > Reduction in CFR > Demand ischaemia +/- angina
- Vulnerable plaque > Plaque rupture > Thrombosis > Acute coronary syndrome/ Infarction - Vasospastic disease
- Focal/ transient vasospasm > Prinzmetal angina
- Persistent vasospasm > Myocardial infarction
Explain the pathophysiological changes in coronary microcirculation that lead to myocardial ischemia
Microvascular dysfunction
> impairs coronary physiology and myocardial blood flow
> myocardial ischaemia in CAD and Cardiomyopathies
> Severe acute ischaemia
Mechanism of ischemic chest pain (referred pain)
Ischemic episodes
> excite chemosensitive and mechanosensitive receptors in heart
> Release adenosin, bradykinin, cytokines
> Excite sensory sympathetic and vagal afferent fibers
> Upper thoracic sympathetic ganglia and thoracic roots of spinal cord
> cardiac sympathetic afferents impulses converge with somatic thoracic structures
> Chest pain
Mechanism of silent myocardial ischaemia
Long term diabetes
> Reduced nerve growth factor
> failed development of cardiac sensory system
> failed afferent signal to thoracic ganglia and impulse convergence with somatic nerve fibers
> no chest pain
Prevalence of angina
Typical presentations
> 60 years old = 25-37% men and 16-23% women
50% present with angina pectoris
50% with acute coronary syndrome
Primary cardiac causes of IHD
- Coronary artery abnormalities:
- Spasm, arteritis, dissection, malformation, myocardail bridging - Valvular
- Aortic stenosis - Structural
- Hypertrophic cardiomyopathy, Dilated cardiomyopathy
Primary non-cardiac causes of IHD
- Decrease oxygen delivery - hypoxemia
- Anemia, Sickle cell disease, carbon monoxide poisoning - Endocrine
- Hyperthyroidism (thyrotoxic AF), Pheochromocytoma
Effect of LDL levels on onset of IHD
Reduce LDL cholesterol = delay onset of IHD
Familial hypercholesterolemia greatly decreases age of IHD onset
Pathogenesis of atherosclerotic plaque formation
- Atherophil (modified smooth muscle cells or macrophages) proliferate
> Atherocyte phagocytizes lipids
> Lipid-laden atherocytes die and release lipids
> Other atherocytes engulf lipid content under sufficient oxygen
> Increasing platelet and fibrin blocks O2 diffusion and astrocytes cannot engulf lipid content
> extra-cellular lipid accumulates, internal elastic membrane fractures and stiffens
> Pathological intimal thickening - Fibrophils (modified fibroblasts or histocytes) produce fibrous tissue and accelerate calcium deposition
> Fibroatheroma formation
> > Formation of atherosclerotic plaque in intima layer
Define risk factors of coronary artery disease
□ Modifiable: abdominal obesity, BP, cholesterol, cigarette smoking, alcohol, diet, DM, lack of exercise, cocaine abuse
□ Non-modifiable: family Hx of CVD, male gender, advanced age
Define stable, unstable angina
Define myocardial infarction
□ Stable angina: ischaemia due to fixed stenosis
□ Unstable angina: ischaemia due to dynamic obstruction (e.g. ruptured atherosclerotic plaque, acute thrombosis)
□ Myocardial infarction: myocardial necrosis due to acute occlusion
Typical presentation of stable angina (ESC Guidelines)
Provoking and relieving factors
Retrosternal chest discomfort with typical quality (dull, constricting) and duration (<30min)
→ ± radiation to arms, shoulder, jaw
Provoked by exertion or emotion
Relieved by rest or sublingual nitrate ≤5min
Clinical grading of angina pectoralis
CCS grading of angina pectoralis 0 – asymptomatic I – angina with strenuous exertion II – angina with moderate exertion (slight limitation of ordinary activities) III – angina with mild exertion (great limitation) → indicated for Tx IV – angina at rest
Patterns of pain radiation in angina pectoris
Neck/ throat tightness Lower jaw Left shoulder or arm in ulnar distribution Interscapular Epigastrium Back
Sometimes to right arm
Associated non-chest pain manifestations of myocardial ischemia
Dyspnea:
- rest or exertional
- Paroxysmal nocturnal dyspnea
Abdomen:
- Atypical, sharp pain
- RUQ pain (mimic pancreatitis or gallbladder disease)
- Nausea and vomiting
Psychologial:
- Intense Fear
Diaphoresis
Weakness, syncope, coma
Signs of risk factors of coronary artery disease
- BP: >15mmHg arm BP disparity
- > 30 BMI
- Lipid
- Cutaneous xanthomas, xanthelesma, corneal arcus - DM:
- acathosis nigricans, skin tags - Others:
- Franks sing (ear lobe crease)
- Tar stains, teeth stains
- Wheezing, prolonged expiration (COPD)
Signs of coronary artery disease complications
- CHF:
- Increase JVP
- Abnormal heart sounds
- Displaced apex
- Low-output cardiac failure - Arrhythmia
- PAD:
- Peripheral pulse absence
- Carotid bruit
- Trophic signs
Baseline investigations for suspected coronary artery disease (4 tests)
Blood tests
12-lead ECG:
- Evidence of MI, myocardial damage
Echocardiogram:
- LVEF (prognostic)
- Structural heart diseases
- Regional wall motion abnormalities
CXR:
- Pulmonary cause or complications
Outline full spread of blood test metrics for suspected coronary artery disease
Blood:
- CBC
- Thyroid function test
- Fasting glucose, HbA1c, OGTT > DM
- Fasting lipid profile > Hyperlipidaemia
- RFT/ Creatinine (prognostic)
- LFT, CK (statin)
Markers:
- High-sensitivity C-reactive proteins
- Brain natriuretic peptide (BNP)
- hs- TNT
List diagnostic investigations for suspected coronary artery disease
→ Anatomical test: CT coronary angiography
→ Functional test: exercise tolerance test (ETT), stress echo
→ Myocardial perfusion scintigraphy
→ Cardiac MRI
Modalities of cardiac stress tests (3)
□ Exercise: bicycle ergometer, treadmill test
□ Vasodilators, eg. adenosine, dipyridamole → based on ‘coronary steal phenomenon’
□ Inotropes, eg. dobutamine
Conducted with 12-lead ECG, BP, ECHO
Positive = horizontal or down-sloping ST depression of >0.1mm
Positive ECHO = regional wall motion abnormality, LV dysfunction
Outline the selection process of diagnostic investigations for suspected coronary artery disease
- Contraindicated for stress testing / Clinical findings warrant coronary imaging»_space; CT Coronary angiography
- No contraindication for stress testing + unable to exercise»_space; Pharmacological stress test
- No contraindication for stress test + able to exercise»_space; Exercise stress test
- No contraindication for stress test + able to exercise + no previous revascularization/ resting ECG normal»_space; Exercise tolerance test with ECG
2,3,4 may require follow-up coronary imaging if high risk or inadequate information for diagnosis
Direct indications for coronary angiogram
- Unacceptable angina despite medical therapy
- Non-invasive test results with high-risk features
- Angina or risk of CAF with depressed LVEF
- Unclear non-invasive test results and prognosis
