Ischaemic Heart Disease and Hypoxia Flashcards
What ischaemic heart disease?
IHD is the term given to heart problems caused by narrowed heart (coronary) arteries that supply blood to the heart muscle.( Mismatch between demand and supply)
What are other names for IHD?
Coronary heart disease (CHD)/Coronary artery disease (CAD)
What are the signs and symptoms of IHD?
Angina Heart Rhythm problems Nausea Sweating Fatigue SOB Reduced exertional activity Leg swelling Diaphoresis
Describe the chest pain in IHD?
Aching, burning, fullness, heaviness, numbness, pressure, squeezing
Radiation in arms, back, jaw, neck, shoulder
High or low BP
Syncope
What are the rhythm problems in IHD?
Palpitations (irregular heartbeats or skipped beats)
Heart murmurs
Tachycardia (Acute coronary syndrome ACS, Acute myocardial infarction AMI)
Atrial fibrillation
Ventricular tachycardia or ventricular fibrillation
S4gallop: A common early finding of diastolic dysfunction
S3gallop: An indication of reduced left ventricular function and a poor prognostic sign
What is IHD often mistaken for?
Indigestion
Heartburn
What are the Non-modifiable risk factors for IHD?
Age Gender Family history of CVD Ethnicity Genetics Previous history of CVD
What are the modifiable risk factors?
High BP Total cholesterol HDL Smoking Diabetes Diet High BMI Alcohol Physical inactivity Stress Low socioeconomic state Medication
What is the percentage contribution of modifiable risk factors to IHD?
70%
When does IHD occur?
imbalance between the supply of oxygen (and other essential myocardial nutrients) and the myocardial demand for these substances
What are the two causes of IHD?
Coronary blood flow to a region may be reduces due to OBSTRUCTION
A general decrease of oxygenated blood flow to myocardium
What causes obstruction?
Atheroma Thrombosis Spasm Embolus Coronary ostial stenosis Coronary arteritis
What causes general decrease in blood flow?
Anaemia
Carboxyhaemoglobulinaemia
Hypotension causing decreased coronary perfusion pressure
What is atherosclerosis?
Complex inflammatory process
Accumulation of lipids
Macrophages
Smooth muscle cells
In the intimal plaques in the large and medium sized coronary arteries
The process is also called Atherogenesis
What triggers atherosclerosis?
Endothelial dysfunction
Mechanical sheer stresses (HTN)
Biochemical abnormalities (elevated and modified LDL, DM, elevated plasma homocysteine)
Immunological factors (free radicals from smoking)
Inflammation ( infection such as chlamydia, Helicobacter)
Genetic alteration
Summarise stages of atherosclerosis pathophysiology
Fatty streak phase
Plaque progression
Stable plaque
Vulnerable plaque
How does IHD present?
Can be asymptomatic
Chronic stable angina
Acute coronary syndromes
Heart Failure
What are acute coronary syndromes?
Unstable Angina
Non ST elevation MI
ST elevation MI
How do acute coronary occlusions occur?
Thrombus forms
Atherosclerotic plaque breaks through the endothelium
Direct contact with the flowing blood
blood platelets adhere to it
fibrin is deposited
Red blood cells entrapped to form a blood clot
The clot grows until the artery occludes the vessel
Why can you still get ACS in the presence of collaterals?
The collaterals can also get atherosclerosis or the damage become so extensive that even the collaterals can not help
Can cause weakening of the heart and hence heart failure
What is the role of collateral vessels?
After an acute episode
Collaterals that were collapsed before start opening due to hypoxic condition
Can supply normal coronary blood flow
What is myocardial infarction?
After an acute occusion the area of muscle that has either zero flow or so little flow that it cannot sustain cardiac muscle function is said to be infarcted
What is the pathogenesis of MI?
Small amount of collaterals open and blood seep into the infarcted area
Local blood vessels dilate and area becomes overfilled with stagnant blood
Muscle fibres use all the remaining oxygen, hemoglobin becomes totally deoxygenated giving bluish brown hue & blood vessels appear engorged despite lack of blood flow