Lecture 11 Ischaemic Heart Disease I Flashcards
What is meant by ischaemic heart disease
Ischaemic heart disease is a condition where the blood flow in the coronary arteries is restricted by an obstruction
What is the significance of IHD as a disease
It kills more people worldwide than any other disease
What is the ultimate cause of death in patients with IHD
Acute myocardial infarction
What causes IHD
Ischaemic disease occurs when a fatty/fibrous plaque called an atheroma blocks the coronary artery lumen. This means that blood flow to tissues is then restricted leading to ischaemia
What happens when ischaemia occurs
Oxygen demand to the myocardium exceeds supply
How does IHD usually present
Patients with IHD often present with chest pain. This chest pain can be due to angina or myocardial infarction
What is meant by the term angina
Cardiac-related chest pain
There are two classes of risk factors in IHD what are they
Modifiable and non-modifiable
Give some examples of non-modifiable risk factors in IHD
Age male personal history (positive family history usually 1st degree relative before the age of 65)
Give some examples of modifiable risk factors in IHD
Smoking diet/obesity renal disease high blood pressure and diabetes
What class of conditions are IHD patients susceptible to when the plaque ruptures
Acute coronary syndromes
What are the different types of acute coronary syndromes
Unstable angina non-ST elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI)
Which is the most severe form of acute coronary syndrome
STEMI
How are the three forms of acute coronary syndromes related
Unstable angina will progress to NSTEMI or potentially STEMI
Stable angina is a type of acute coronary syndrome T or F
F – it is not
How does stable angina present
Chest pain that occurs with increase physical activity or exertion but with a normal ECG
Use the diagrams below to explain the difference between stable and unstable angina
In stable angina the lipid core is often walled-off from the blood flow. In addition a large degree of healing has occurred so that the intimal layer separates and protects atheroma from the blood. This prevents progression to the ACS stage. However in unstable angina there is the addition of a platelet plug fibrous plaque and thrombus consisting of a matured fibrin clot. This has progressed to the stage at which most of the central core of the vessel is blocked
What is meant by a mural thrombus
This is where the complete core of the vessel is blocked by clot platelet plug and plaque
Anginal pain is always relieved by rest T or F
F – whilst this is true for most angina it is not the case in STEMI
Treatments used for angina based around knowing what type of angina the patients have T or F
T
How is stable and unstable angina treated
Stable angina patients are treated with nitrates and Ca2+ channel blockers to reduce the cardiac work. They are also treated for the underlying condition for example using statins in high cholesterol. Finally there is a degree of prophylactic treatment using anti-platelet therapy such as aspirin. Meanwhile unstable angina patients are treated as for a myocardial infarction. They are given dual anti-platelet therapy usually consisting of aspirin plus either clopidogrel or ticagrelor
Complete the table below distinguishing the acute coronary syndromes
See completed table below
Why does the ECG often appear normal in patients with angina
ECG will appear normal in stable and unstable angina unless there is a period of ischaemia at the time in which the ECG is being recorded
What is the issue with using troponin levels as an indication of heart attack
Troponin takes a while to rise during a heart attack. Hence if you measure it too early myocyte death may not have occurred yet
Which patients are sent straight to tertiary heart attack centres
STEMI
What are the broad aims of the treatment for ischaemia
Reopen blocked arteries (stenting) reduce the coagulability of blood (DAPT) control of risk factors and reduce myocardial oxygen demand
What is PCI
Percutaneous coronary intervention (PCI) is a non-surgical technique used to widen the artery using dilation from within
When is PCI used as the primary treatment
In STEMI patients
Why is it important to match the stent size to the size of the patients affected vessels
Important not to be oversized as overdilation will result in massive repair response and further narrowing of the vessel
How is the stenosis in the patient’s coronary arteries viewed during stenting
A dye is injected into patients and viewed under fluoroscopy
Which drugs are often used in drug eluting stents
Rapamycin and taxol are often used. Rapamycin is a cell cycle blocker that prevents progression between G1 and S phase. These drugs both act to inhibit regrowth of the vessel
What is the door-balloon time in STEMI patients
120minutes
Outline the mechanism of stenting
The stent is crimped down over a balloon connected to a wire. The balloon and stent inserted and navigated past the point of occlusion in the coronary artery. The balloon is then inflated to 8 atmospheres to extend the stent which is then placed against the vessel wall. Finally the balloon is deflated and removed with the stent remaining in place in the expanded vessel
What treatment is usually prescribed alongside stenting
DAPT
How many stents do the average patient receive
3-4 stents per person
What used to be a major problem in stenting and why
Stenosis was a major problem. This was because the artery walls react badly to foreign bodies. This causes a healing response that actually acts to further narrow the vessel
How can restenosis be prevented
Using drug eluting stents that inhibit the repair processes and proliferation of the vascular wall
What is the main problem with drug eluting stents
Incidence of stent thrombosis is a problem with drug eluting stents. This is a serious condition with adverse clinical outcomes that occurs due to delayed or incomplete endothelialisation. This is because drug eluting stents prevent some of the healing response which leads to exposure of the metal of the stent to the flow of blood. If part of the blood connects to the metal stent or underlying vessel wall then it is likely that a thrombus will form
What treatment is usually prescribed to override the problems with stent thrombosis seen in patients with drug eluting stents
DAPT - aspirin plus an anti-platelet or anti-clotting drugs such as clopidogrel or ticagrelor. This must be continued a long time after the stent is inserted up to 1 year after stenting
What are the additional benefits of DAPT
Has a pleiotropic effect on the neutrophils and can reduce incidence of subsequent pulmonary infections
Draw a diagram depicting and ST elevated ECG trace
See completed diagram below
