Cardiovascular disease 1 Flashcards
What is the definition of ischeamic heart disease?
Inadequate blood supply to the myocardium due to any imbalance in supply vs. demand
For what 2 main reasons could someone have inadequate blood supply to the myocardium?
1) Reduced coronary blood flow - usually atheroma - with or without thrombus
2) Myocardial hypertrophy, usually due to systemic hypertension
Why does diastolic insufficiency occur in IHD?
Most perfusion of the heart occurs during diastole when the aortic valve is closed and there is a degree of back flow into the cusps - in IHD during diastole is when the relative O2 deficit is at its worst
What is loss of autoregulation in IHD, at what percentage of occlusion does it occur?
Autoregulation of the vessels is dilation and constriction according to demand, vessels lose autoregulation when they cannot dilate sufficiently to allow enough blood through - this happens at >75% occlusion
At what percentage of stenosis is blood supply to the heart insufficient at rest?
> 90%
In which type of IHD is low diastolic flow particularly apparent?
Sub endocardial
How many seconds of ischemia are possible before function of the myocardium is lost?
60 secs
What happens to the myocardium if ischaemic for more than 60 secs?
Get myocyte dysfunction and death from ischemia
After how many minutes of ischemia is the damage to the myocardium irreversible?
20-30 mins
Name 4 common ischemic heart disease syndromes?
1) Angina pectoris
2) Acute coronary syndrome
3) Sudden cardiac death
4) Chronic ischaemic heart disease
What are the 3 types of angina?
1) Typical/stable - fixed obstruction, predictable relationship to exertion
2) Variant/Prinzmetal - coronary artery spasm
3) Crescendo/ unstable - often due to plaques disruption and small emboli, pain is getting worse and more unpredictable
Which of the 3 types of angina is a red flag and requires urgent treatment?
Crescendo/unstable angina
What classifies a cardiac infarct?
Loss of myocytes
What are the 2 acute coronary syndromes?
1) Acute myocardial infarction (+/- ECG ST elevation)
2) Crescendo/unstable angina
Why does a subendocardial myocardial infarction commonly occur without any acute coronary occlusion?
1) The subendocardial myocardium is relatively poorly perfused in normal conditions (far from coronary vessels and far from heart chamber for direct diffusion)
2) If there is a stable angina or an acute hypotensive episode…
3) The subendocardial myocardium can infarct without any acute coronary occlusion
Subendocardial MIs are different to your typical MIs
What is a transmural myocardial infarction?
Severe occlusion of the coronary vessel leads to death of myocytes across all layers of the myocardium
What would be the gross and microscopic appearance of an infarct less than 24 hours old?
Microscopic - necrosis and neutrophils
Gross - normal/dark
What would be the gross appearance of an infarct which was:
a) 1-2 days old
b) 3-7 days old
c) 1-3 weeks old
d) 3-6 weeks old
Gross appearance 1-2 days = yellow infarct center 3-7 days = hyperaemic border, yellow center 1-3 weeks = red/grey 3-6 weeks = scar
What would be the microscopic appearance of an infarct which was:
a) 1-2 days old
b) 3-7 days old
c) 1-3 weeks old
d) 3-6 weeks old
1-2 days = more necrosis and neutrophils (than
What are the 5 blood markers of cardiac myocyte damage?
1) Troponins T and I
2) Creatine kinase MB
3) Myoglobin
4) Lactate dehydrogenase isoenzyme 1
5) Aspartate transaminase
Which blood marker is most commonly used post MI, when does it peak, for how many days is it raised?
Troponin
Detectable after 2-3 hours, peaks at 12 hours and detectable for up to 7 days
In what 3 other conditions is troponin raised?
1) heart failure
2) Myocarditis
3) PE
Creatine Kinase MB is detectable how may hours post MI and peaks when, when can you detect it til?
Detectable 2-3 hours post MI for up to 3 days
Peaks at 10-24 hours
Myoglobin peaks when post MI, why is it not the most useful?
Peaks at 2 hours
Less useful as also released from skeletal muscle
Lactate dehydrogenase isoenzyme 1 peaks how many days post MI and is detectable for how many?
Peaks at 3 days, detectable for up to 14 days
Why is aspartate transaminase a less useful blood marker of cardiac myocyte damage?
Because its also present in the liver
What are the 3 subtypes of creatine kinase, where is each mostly found?
1) CK MM - muscle (cardiac and skeletal)
2) CK BB - brain, lung
3) CK MB - mainly cardiac, also skeletal muscle
On the basis of what 3 factors is a diagnosis of MI made?
1) Clinical
2) ECG
3) Blood cardiac proteins