Ischaemic Heart Disease Flashcards
What part of the heart does the LAD supply?
The anterior part of the LV, the anterior part of the RV and the anterior 2/3rds of the IV septum
What part of the heart does the circumflex artery supply?
The lateral LV
What part of the heart does the posterior descending artery supply?
Inferior part of the LV, inferior part of the RV and posterior 1/3rd of the IV septum
What does the oxygen supply to the heart depend on?
oxygen content of blood and myocardial blood flow
What determines myocardial blood flow?
Perfusion pressure (pressure inside aorta), vascular resistance (effected by external pressure)
In which part of the cardiac cycle does myocardial blood flow occur?
Diastole
Why is subendocardial muscle most susceptible to ischaemia?
Because it is subjected to the greatest pressure potentially impairing blood flow
Why does the heart need increased blood flow with increased demand?
Because under normal conditions the heart will take almost all the oxygen out of the blood so to get more oxygen need more flow
How do you get increased supply?
vasodilation via adenosine, lactate, hydrogen ions, prostacyclin, NO and innervation
What does myocardial oxygen demand depend on?
ventricular wall stress (hypertrophy), heart rate, contractility
What is ischaemic heart disease?
A group of conditions where there is an imbalance between myocardial oxygen supply and demand including angina and MI - either chronic or acute
What part of coronary arteries does atherosclerosis mostly effect?
Epicardial parts
What percentage of narrowing will cause angina?
70%
What causes stable angina?
A stable plaque
What is the result of an unstable plaque?
unstable angina, sudden cardiac death, myocardial infarction
What causes the pain in a heart attack?
Anerobic production of ATP which causes acidosis and a build up of metabolic products which accumulate locally
What is sudden cardiac death?
An unexpected fatal event within 1 hour of the beginning of symptoms in an apparently healthy subject
What is the most usual cause of sudden cardiac death?
coronary atherosclerosis leading to ventricular fibrillation
What happens to myocardial cells in myocardial infarction?
ATP depletion, generation of ROS, altered calcium homeostasis
What are the different types of myocardial infarctions in terms of site and size?
full thickness regional infarction, regional subendocardial infarction, circumferential subendocardial infarction
What are the cardiac markers of a myocardial infarction?
myoglobin, cardiac troponins T and I and the MB fraction of creatine kinase
Which cardiac marker appears the earliest?
myoglobin
Which cardiac marker persists for the longest?
troponins
Which are the most sensitive and specific cardiac markers?
Troponins
Which cardiac marker is the least specific?
myoglobin
What are the immediate consequences of myocardial infarction?
arrhythmias (VT, VF, conduction defects, AF), acute cardiac failure, pulmonary oedema, cardiogenic shock
What are the delayed consequences of myocardial infarction?
cardiac failure, rupture, thrombus formation, arrhtyhmias, infarct expansion, fibrinous pericarditis, papillary muscle dysfunction
What factors influence complications?
Size, site and transmural extent of infarct
What are other causes of ischaemic heart disease apart from atherosclerosis?
Thromboemboli, immune disorders of vessels, aortic dissection, LVH, tachycardia, hypoxaemia, shock
What is the management for ischaemic heart disease?
lifestyle modification, pharmacological intervention, stents, coronary artery bypass
