18- Coronary Heart Disease, Mi And Embolism Flashcards
How does coronary heart disease present
Sudden cardiac death
o Acute coronary syndrome – Acute myocardial infarction – Unstable angina
o Stable angina pectoris o Heart failure
o Arrhythmia
What increases your risk of CHD
Tobacco use, physical inactivity, harmful use of alcohol, unhealthy diet accounts results in:
– Hypertension
– Obesity
– Diabetes mellitus – Hyperlipdaemia
What is myocardial ischaemia
Mismatch between myocardial oxygen supply and demand
• Primary reduction in blood flow
What are the 2 components of coronary arteries
the coronary arteries have an epicardial component and an intramyocardial component
What happens in epicardial stenosis
If you have stenosis in the epicardial compartment - the resistance in the epicardial component INCREASES
• This can be compensated to a degree by an increase in the diameter of the intramyocardial resistance vessels - thus decreasing the resistance in the intramyocardial component to maintain flow
What is coronary flow reserve
ability of the coronary circulation to adapt to
an increasing demand in the face of an increasing epicardial coronary stenosis
What is angina pectoris
It is a tight feeling in the chest which can diffuse across the jaw, shoulders,
back or arms
• It can be provoked by physical exertion, emotional stress or anxiety
• Use of an inorganic nitrate vasodilator (e.g. glyceryl trinitrate) - the nitrates act
as a vasodilator leading to reduced coronary resistance and increasing blood
flow thus reversing the supply and demand imbalance
• It can be relieved by rest
What are the 2 types of test for CHD
Functional - demonstrate that there is an imbalance between supply and demand
Anatomical - look at anatomical severity of the narrowing within the artery then make an inference about how it is compromising flow - some of these tests are invasive and others are not
Which imaging techniques can be used to diagnose CHD
Imaging techniques include: echocardiography, MRI or nuclear perfusion imaging
What are the 3 types of treatment strategy for CHD
Prevent atherosclerosis progression and risk of death/MI
– Education
– Lifestyle modification
– Aspirin, statins, ACE inhibitors
o Reduce myocardial oxygen demand
– HR (b blockers, Ca antagonists, If blockers) – wall stress (ACE inhibitors, Ca antagonists) – Metabolic modifiers
o Improve blood supply
– Vasodilators (nitrates, nicorandil, Ca antagonists) – Revascularisation (PCI, CABG)
What 3 ways can coronary arteries become blocked
Coronary plaque rupture
Coronary plaque erosion
Coronary dissection
What is Virchow’s triad
Abnormal Vessel Wall
• Abnormal Blood Flow
• Abnormal Blood Constituents (hypercoagulability)
What is the difference between a white and red thrombus
WHITE thrombus
Platelet rich
Common in arterial thrombosis (high pressure/turbulent circulation) Benefit from anti-platelet therapy
• RED thrombus
Fibrin rich with trapped erythrocytes
Common in venous or low pressure situations (stasis) Benefit from anti-coagulant or anti-fibrinolytic therapy
Where does tissue factor come from
Tissue factor can be made from the cellular constituents of the atherosclerotic plaque or by the ischaemic heart muscle itself
• Circulating inflammatory cells can also act as a humoural source of tissue factor that can promote the atherosclerotic process
• Tissue factors triggers a cascade of factor activation leading to coronary thrombosis
• Factor 10a and Factor 2a are important molecular targets
Was is acute MI
DEFINITION: Detection of a rise or fall in a biomarker (TROPONIN) with at least one value >99th percentile reference limit AND at least one of:
Symptoms suggestive of ischaemia
New or presumed new ST-T changes or LBBB on ECG
Development of pathological Q waves on ECG
Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
Identification of intracoronary thrombus or angiography or autopsy
What is cardiac troponin
There are THREE isoforms: I, T and C
• Troponin I and T are highly specific to cardiac muscle
• This troponin is released as a result of proteolytic cleavage during myocardial ischaemia
• So, troponin I and T can be related to cardiac cell death
• After the onset of symptoms, cardiac troponin levels rise and then fall after a period of time
What are the 2 types of acute coronary syndrome
Those who present with ST elevation have complete blockage of a coronary artery due to an occlusive thrombus
No ST elevation - partial occlusion which embolises distally into the microcirculation resulting in myocardial cell death and troponin elevation
What is Primary Percutaneous Coronary Intervention (PPCI) for ST Elevation Acute Coronary Syndrome (STEACS)
A guide wire is passed through the coronary thrombus and over the wire a balloon is passed and a stent is deployed which allows recanalisation of the vessel
How does an infarction develop
The myocardial necrosis zone will start at the inner layers of the myocardium and progress as a wave front to spread through the entire extent of the myocardium if the coronary artery wasn’t quickly recanalised
What is a reperfusion injury
The act of opening an artery can be associated with damage to the heart muscle - reperfusion injury
How much does reperfusion reduce infarction by and how can it be reduced further
By 40%
Cardio protection reduces by a further 25%
Describe post MI left ventricular remodelling
expansion of the heat muscle, thinning of the scar and impairment of heart function
• It is accompanied with an increased risk of heart failure and arrhythmias
How can left ventricular modelling be managed
Non-Drug Cardiac Resynchronisation Therapy (Pacemakers (P) or Defibrillators (D)) • Often written as CRT-P and CRT-D Progenitor cells • Drugs Beta blockers ACE inhibitors Angiotensin receptor blockers
