Unit 6 - Cardiovascular system 6 Flashcards
What is myocardial oxygen balance?
Ratio of oxygen supply to oxygen demand
What is oxygen supply increased by?
Either increasing arterial oxygen content or increasing coronary blood flow
What is an increase in blood pressure or heart rate met with?
A proportionate increase in coronary blood flow
When does myocardial ischaemia develop?
When blood supply to the myocardium is inadequate to meet the metabolic demands of the tissue
- absolute reduction at rest
- supply ischaemia
- relative reduction in face of increased muscle work
- demand ischaemia
What percentage of cases is myocardial ischaemia associated with critical stenosis of one or more coronary arteries?
95%
- practically unknown in absence of coronary artery disease
What is chronic stable angina?
Critical stenosis (narrowing) of one or more epicardial coronary arteries due to atherosclerosis
- advanced and stable plaques in one or more multiple locations
- fixed stenosis
What is the main symptom of chronic stable angina?
Typical pattern of demand ischaemia
- angina pain develops on exertion
reproducibly relieved by rest or nitrovasodilator
What is the characteristic pain pattern of chronic stable angina?
Referred pain
referred pain to the chest and upper left arm
What is silent ischaemia?
Evidence of myocardial ischaemia in the absence of chest discomfort
What percentage of transient ischaemic episodes in stable coronary artery disease are NOT associated with pain?
70%
Which group of patients is silent ischaemia particularly seen in?
Diabetic patients
- sensory neuropathy
What can be used to diagnosis silent ischaemia?
Exercise or stress testing along with ambulatory ECG
- Holter monitor
What are the three other types of ischaemia?
- Prinzmetal’s (variant) angina
- cardiac syndrome X
- unstable (crescendo) angina
What is Prinzmetal’s (variant) angina?
Occurs at rest due to coronary artery spasm/constriction
- rare
What is Cardiac syndrome X?
Angina without epicardial coronary arteries
- more likely to be a microvascular disease
- more common in women
What is unstable (crescendo) angina?
Sudden onset - at rest - exercise An acute coronary syndrome - thrombosis leads to occlusion at site of plaque
What can chronic coronary disease lead to?
Cardiomyopathy resulting in reduced left ventricle output
What does chronic hypoperfusion lead to?
Reduced output in viable myocardium
- hibernating myocardium
Reversible with revascularisation
What is an acute coronary syndrome?
Umbrella term
- blood supply to the heart is suddenly blocked
- unstable angina
- acute myocardial infarction (AMI)
What is the difference between unstable angina and acute myocardial infarction?
Unstable angina - obstruction typically incomplete
Acute myocardial infarction - usually fully occluded vessel
- rendering distal myocardium ischaemic
What process precipitates coronary thrombosis?
Fissuing
Atheromatous plaque rupture
What is a coronary thrombosis?
Formation of a blood clot in a coronary artery
What can the formation of a coronary thrombosis be related to?
Increase in emotional or physical stress Circadian rhythm - sympathetic nervous system - temperature changes - heart rate in the morning
What are the symptoms of acute coronary syndromes?
Chest pain - tightness - pressure - discomfort Pain or discomfort in one or both arms Shortness of breath Feeling dizzy or lightheaded Nausea and/or diaphoresis Anxiety Symptoms steadily worsen - unrelieved by rest or nitrates
