MI and Ischaemic Heart Disease Flashcards
What is chronic stable angina?
Demand led ischaemia of the heart muscle due to a fixed stenosis
What is the recommendation for patients who have an angina attack and have stable angina?
Stop, sit and use GTN spray
When may angina commonly be felt?
- After a meal
- In cold air
Where does pain for angina commonly radiate?
- Jaw
- Back
- Epigastrium
- Left (and right) arm
What type of pain is felt with angina?
Heavy crushing pain with tightness
What are the two types of acute MI?
- STEMI
- NON-STEMI (NSTEMI)
Why does acute cornonary syndrome occur?
Development of an atheromatous plaque that develops a thrombosis and ruptures
Which steps lead to thrombosis occuring?
- Normal
- Fatty streak
- Atherosclerotic plaque
- Fibrous plaque
- Rupture/thrombosis
In what ways is chronic stable angina different to an acute coronary syndrome such as unstable angina?
- It has a fixed stenosis (not comple occulsion)
- Demand led ischaemia (not supply led)
- Predictable
- Safe
What are the three sub-stages of thrombosis formation?
- Initiation
- Adhesion
- Activation
Describe the initiation stage of thrombosis formation
There is vascular damage exposing the sub-endothelium, collagen and von Willebrand factor
Describe the adhesion stage of thrombosis formation ( two thinks platelets bound to)spells as v instead of w
Platelets recruit to the area and bind to the exposed collagen and von Willebrand factor forming a monolayer
Describe the activation stage of thrombosis formation
- Platelets become activated after adhesion and change shape from discs to star-like shapes
- Platelets release ADP and thromboxane A2 (generated by cyclooxygenase)
- ADP bind to receptors on circulating platelets allowing more activation to occur
- Activated platelets express adhesion sites for leukocytes (P-selectin and CD40 ligand)
- These processes contribute to the platelet cascade which causes acceleration of platelets activation and coagulation
What is the consequence of intraluminal coagulation?
Vascular blockage
Hence MI, stroke and death are all possible
What are key synptoms of MI?
- Severe crushing (10/10) pain not relieved by GTN and lasting a long time
- Pain occurs at rest
- Pain radiates to jaw, left (and right) arm, back and epigastric region
For a MI, where will the changes be seen on an ECG?
- ST elevation
- T wave inversion
- Q waves
How is a STEMI seen on an ECG?
- >/= 1mm ST elevation in 2 adjacent limb leads
- >/= 2mm ST elevation in at least 2 continous precordial leads
- New onset bundle branch block
How does the ECG change after an MI?
- Initially an ST elevation is present (a few hours)
- Q wave formation and T wave inversion follow (within a day)
- Finally, Q waves are present with or without T waves
In an inferior MI, which limb leads will be affected?
II, III, aVF
In an aterior MI which limb leads can be affected?
V1-6
In an anteroseptal MI, which limb leads are affected?
V1-4
In an anterolateral MI, which limb leads are affected?
I, aVL, V1-6
Which two urine tests can help in the diagnosis of MI?
- Creatinine kinase
- Troponin C
At what time will creatinine kinase levels peak in the urine after MI and what does this signify?
Within 24 hours
Creatinine kinase found in muscle and brain cells
Suggests muscle damage
What does the presence of troponin C in urine suggest?
Highly specific for cardiac muscle
It is a good indicator for myocardial necrosis
How is a STEMI immediately treated?
Clopidogrel - 300mg
Aspirin - 300mg
What is clopidogrel?
An inhibitor of ADP binding sites (P2Y12 receptor) which prevents activation of glycoprotein IIb/IIIa (fibrinogen receptors) on platelets
How does aspirin work?
Aspirin prevent cyclooxygenase (COX-1) activation in platelets
This prevents production of thromboxane A2
(it also blocks COX in endothelial cells blocking production of anti-thrombotic prostaglandin I2 is inhibited - this is not useful)
What is thrombolysis?
A way of unblockign arteries by breaking down clots using thrombolytic drugs such as streptokinase
When should thrombolysis be administered?
- Chest pain is suggestive of acute MI (more than 20 minutes and less than 12 hours)
- ECG changes - acute ST elevation, new LBBB
- No contraindications
It is NOT administered if PCI will be available
What is the downside to thrombolysis?
It can lead to severe intracranial haemorrhage
What is primary angioplasty?
A procedure also termed percutaneous coronary intervention (PCI) or coronary angioplasty, which involves inserting a wire through the coronary artery and opening it up again by inserting a balloon
What type of pain relief is given for MI?
Analgesic - Diamorphine (IV)
What is the full list of treatment given to a patient with a STEMI?
- Analgesia - diamorphine (IV)
- Antiemetic - IV
- Aspirin - 300mg
- Clopidogrel - 300mg
- GTN - when BP >90mmHg
- Oxygen - if hypoxic
- Primary angioplasty (PCI)
- Thrombolysis - when angioplasty is not available within 90 minutes
Infarction of myocytes most likey causes which type of arrhythmia?
Ventricular fibrillation
What is the KILLIP classification?
A system used in individuals with acute MI taking into account examination and the development of heart failure in order to predict the risk of mortality
Describe stages 1 to 4 in the KILLIP classification
- I - No signs of heart failure
- II - Crepitation < 50% of lung fields
- III - Crepitations > 50% of lung fields
- IV - Cardiogenic shock
How may an NSTEMI be diagnosed?
- ECG may show ST ↓ + TWI
- Pain is present in normal areas - left/right arm, jaw, back and epiastrium
- Troponin/creatinine kinase levels in urine
Troponin is a proetin exclusive to which cells?
Cardiac cells
Why is troponin a good test and relevant to MI?
When mycotyes undergo necrosis after MI, troponin is released and can be present in the urine
What are the three types of troponin?
Troponin C - binds to calcium and is identicle in heart and muscle cells
Troponin I - in absence of calcium it binds to actin and inhibits actin-myosin ATPase induced contraction, it is specific to the heart
Troponin T - links troponin complex to tropomyosin faciliating contraction, it is also specific to the heart
Which two out of the three troponin types have a higher likelihood of pointing towards MI?
TnT and TnI - they are specific to the heart muscle
Troponin may be detected in the urine in which other conditions?
- PE
- Post arrhythmia
- Renal failure
- Hypertensive crisis
What is a class I MI?
Spontaneous MI related to ischaemia due to a primary coronary event such as plaque erosion and or rupture
What is a class 2 MI?
MI secondary to ischaemia due to imbalance of oxygen supply and demand from cornary spasm, embolism, anaemia, arrhythmias etc.
What is a class 3 MI?
Sudden unexpected cardiac death including cardiac arrest often with symptoms suggestive of ischaemia
With new ST segment elevation, new LBBB, or pathological or angiographic evidence of fresh coronary thrombus
What is a class 4a MI?
MI associated with PCI
What is a class 4B MI?
MI associated with documented in-stent thrombosis
What is a class 5 MI?
MI associated with coronary artery bypass graft surgery
Which drugs can act as ADP antagonists?
- Ticegralor
- Ticlopidine
- Clopidogrel
- Prasugrel
Which drugs can act as COX inhibitors?
Aspirin
Which drugs are phosphodiesterase inhibitors?
Dipyridamole
Whcih drugs are GP IIb/IIIa inhibitors?
- Tirofiban
- Eptifibatide
- Abciximab
(block platelet aggregation)
What may be used to identify stenosis?
Coronary angiography
Describe coronary revascularisation
A balloon catheter can stretch out a vessel and push down the plaque to keep the vessel open
or
An intracoronary stent can be administered via balloon to keep the vessel open
What is a transient ischaemic attack (TIA)?
This occurs due to an unstable plaque
The blockage will last only for a short time
Acute MI involves what extent of vessel occulusion?
Complete
What is ischaemic cardiomyopathy?
The negative effects of remodelling and scar tissue from a previous MI
Is angina a symptom?
No
It is a clinical diagnosis
Does pain from angina last a long time?
No, usually a short period
What type of pain is angina?
Visceral pain
Feels like squeezing, heaviness and is similar to a weight on the chest
Where does pain from angina often radiate?
- Arms
- Back
- Jaw
- Teeth
- Shoulder
How can anginal pain be brought on?
- Exertion
- Stress
- Cold wind
- After meal
Which drug is commonly used to relieve anginal pain?
GTN spray
What is the differential diagnosis of chest pain?
- GI - acid reflux, peptic ulcer, oesophageal spasm, biliary colic
- MSK - Hurts during movement, lasts longer, nerve root pain
- Pericarditis - central and posture related
- Pleuritic pain - exacerbated by breathing, sharp
Is it true that morphine can relieve the pain from an MI?
Not always
The pain from an MI is very severe
What type of pain is felt with a PE in comparision to an MI?
Dull pain
How can angina be tested for?
Exercise testing - shows characteristic changes on ECG
Perfusion scanning - can identify areas of the heart with decreased blood flow
CT angiography - non invasive, but less precise than angiography when calcium is present
Angiography - a sheath is instered into the artery (radial/femoral), x-ray contrast is injectedto outline arteries. This test is the gold standard
How can the risk factors be reduced for angina?
- Drugs - aspirin, B blockers, statins, ACEI
- Lifestyle - smoking cessation and diet
- Revascularisation - CABG, PCI
Which two veins may be targeted for coronary revascularisation?
- The left internal thoracic artery
- A great saphenous vein
Describe how the left thoracic artery can be used in coronary artery bypass grafts
The left thoracic artery is diverted to the left anterior descending branch of the left coronary artery, bypassing the occulusion
Describe how a great saphenous vein is used for coronary revascularisation
The vein is removed from a leg
One end is attched to the aorta or one of the major branches
The other end is attched to the obstructed artery immediately after the occulsion
This will restore blood flow
What is cardioplegia?
The intentional cessation of cardiac activity
This is often done for surgical purposes
For a STEMI what is the gold standard treatment?
PCI
Where can Q waves be considered normal?
Q.M
They are normal in most leads. Should not be seen in leads V1-V3
What are the ECG changes associated with a posterior MI? Q.M
- ST elevation, Q waves in leads V7-V9
- Horizontal ST depression
- Tall, dominant R waves with R wave/S wave ratio >1 in lead V2
- Upright T wave
Inferior STEMI is seen in which ECG leads?- Q.M
- ST elevation in II, III, aVF
- Reciprocal ST depression in aVL
Which type of muscle(s) is Troponin found in?
Cardiac and skeletal muscle
Which heart failure medications have evidence to support a reduction in mortality rates? Q.M
Beta blockers, ACE inhibitors, Aldosterone antagonists, hydralazine/nitrates
What are the causes of Left axis deviation? Q.M
Normal variant. Inferior myocardial infarction. Hyperkalaemia. Congenital heart disease. LBBB. Left ventricular hypertrophy (rare cause)
Which lead on an ECG specifically looks at the right ventricle?
Q.M
V1 - as the most anterior of the chest leads
What percentage of patients develop post infarction pericarditis?
Q.M
5-10%
Which vessel is most likely to be occluded in an inferior STEMI? Q.M
RCA
Which scoring system can be used to estimate the probability of a patient having a PE?
Q.M
Wells score
What coronary territory is involved in an anterior MI? Q.M
Left anterior descending artery
What are some of the complications of anterior STEMI?
Ventricular arrhythmia
Recurrent ischaemia/infarction
Acute mitral regurgitation
Congestive heart failure
2nd, 3rd degree heart block
Cardiogenic shock
Cardiac tamponade
Ventricular septal defects
Left ventricular thrombus/aneurysm
What are some of the characteristic murmurs that may be heard in a patient with hypertrophic cardiomyopathy? Q.M
- Ejection systolic murmur, loudest between lower left sternal edge and apex, louder with exercise/standing, quieter when supine/squatting/valsalva.
- Pansystolic murmur - loudest at the apex and radiating to the axilla (mitral regurgitation) due to systolic anterior motion (SAM) of the mitral valve.
- Rarely, diastolic murmur from aortic regurgitation.
What coronary territory is involved in a lateral MI?
Q.M
Left circumflex
What are the causes of right axis deviation?
- Q.M
- Right ventricular hypertrophy
- Right bundle branch block
- Dextrocardia
- Ventricular ectopic rhythms
- Lateral wall infarction
- Right ventricular load
- WPW
Diagnostic features of different ACS subtypes
Diagnosis depends on a combination of clinical, ECG and biochemical findings which helps distinguish between the various types of ACS.
- Q.M
- Unstable angina - Cardiac chest pain + abnormal/normal ECG + normal troponin
- NSTEMI - Cardiac chest pain + abnormal/normal ECG (but not ST-elevation) + raised troponin
- STEMI - Cardiac chest pain + Persistent ST-elevation/new LBBB (note that there is no need for a troponin in this case)
What are the leads involved in an anterior MI?
Q.M
V1-V4
When is septal rupture post-MI more likely to happen? Q.M
Without reperfusion, septal rupture typically occurs within the first week after the infarction.
What are the leads involved in an anterolateral MI?
Q.M
I, aVL, V1-V6
Myocardial infarction and Acute Coronary Syndrome (ACS) Question: Management of STEMI
- Q.M
- Targeted oxygen therapy (aiming for sats >90%)
- Loading dose of PO aspirin 300mg
- Note that some hospital protocols will also call for a loading dose of a second anti-platelet agent such as clopidogrel (300mg) or ticagrelor (180mg)
- For those going on to have PCI, NICE guidance suggests adding Prasugrel (if not on anti-coagulation) or clopidogrel (if on anti-coagulation)
- Sublingual GTN spray - for symptom relief
- IV morphine/diamorphine - in addition this causes vasodilation reducing preload on the heart
- Primary percutaneous coronary intervention (PPCI) for those who:
- Present within 12 hours of onset of pain AND
- Are <2 hours since first medical contact
Remember that (particularly in STEMI) time is heart therefore urgent treatment, escalation and delivery of PPCI is critical to good outcomes.
Classification of MI
Q.M
MI is generally categorised into two types:
- ST-elevation MI (STEMI) - Caused by complete occlusion of a coronary artery
- Non-ST-elevation MI (NSTEMI) - Caused by severe but incomplete stenosis/occlusion of a coronary artery
It is important to remember that some patients can have NSTEMIs due to lack of cardiac oxygenation for other reasons (e.g. severe sepsis, hypotension, hypovolaemia, coronary artery spasm). These cases might not respond to (or need) conventional treatment.
: Post-MI management
*
- ALL patients post-MI patients should be started on the following 5 drugs:
- Aspirin 75mg OM + second anti-platelet (clopidogrel 75mg OD or ticagrelor 90mg OD)
- Beta blocker (normally bisoprolol)
- ACE-inhibitor (normally ramipril)
- High dose statin (e.g. Atorvastatin 80mg ON)
- All patients should have an ECHO performed to assess systolic function and any evidence of heart failure should be treated.
- All patients should be referred to cardiac rehabilitation.
- Patients who have been treated without angiography should be considered for ischaemia testing to assess for inducible ischaemia.
ECG features of acute pericarditis?
- Q.M
- Widespread concave ST elevation
- PR depression
- ST depression and PR elevation in aVR +/- V1
https://www.youtube.com/watch?v=zC3kGghQFLA
Which leads are involved in an inferior infarct?
II, III and AVF
Management of NSTEMI
1.
- Targeted oxygen therapy (aiming for sats >90%)
- Loading dose of PO aspirin 300mg and fondaparinux
- Patients should have their 6 month mortality score (often the GRACE score) calculated as early as possible - all those who are anything other than lowest risk should also be given prasugrel or ticagrelor unless they have a high risk of bleeding where PO clopidogrel 300mg is more appropriate.
- Sublingual GTN spray - for symptom relief
- IV morphine/diamorphine - in addition this causes vasodilation reducing preload on the heart
- Start antithrombin therapy such as treatment dose low molecular weight heparin or fondaparinux if they are for an immediate angiogram
- Patients with high 6 month risk of mortality should be offered an angiogram within 96 hours of symptom onset.
Note that management of unstable angina is similar to that of NSTEMI with aspirin for all patients and fondaparinux and early angiography for those at high risk.
What ECG changes point towards Right ventricular infarction?
- Q.M
- ST elevation in lead V1 and V1>V2
- ST depression in V2
- ST elevation lead III>II
What are the complications associated with inferior myocardial infarction? Q.M
Papillary muscle rupture, bradycardia and AV block. Concurrent right ventricular infarction
What are the examination findings in patients with ventricular septal defect post-MI? Q.M
On examination patients will have a harsh, loud pansystolic murmur along the left sternal border.
Patients also often have a palpable parasternal thrill.
There may be features associated with low output cardiac failure.
Which is the best way to visualise a posterior MI on an ECG Q.M
By using a 15-lead ECG
What is the coronary territory affected in posterior MI?
posterior coronary circulation becomes disrupted. PAD
What is the appearance of the ECG leads in Left axis deviation?
Q.M
Positive in lead I and negative in lead II and III
What ECG features are associated with third-degree heart block? Q.M
Bradycardia, no association between P waves and QRS complexes
Which arteries supply the lateral wall of the left ventricle?
Q.M
Branches of the LAD and left circumflex arteries
