Myocardial Infarction

Question 1

Definition of ACS - acute coronary syndrome

Answer 1

Includes three conditions with a common pathology

• unstable angina
• STEMI
• NSTEMI

Question 2

What is the common pathology in ACS?

Answer 2

Rupture of the fibrous cap of a coronary artery, atherosclerotic plaque. This causes a thrombus, followed by inflammation.
Rarely can also be caused by emboli, coronary artery spasm or vasculitis

Question 3

What is a myocardial infarction?

Answer 3

Myocardial ischaemia and death, releasing troponin into the blood
Ischaemia is a lack of blood supply to an area +/- cell death

Question 4

What is the difference between a myocardial infarction and unstable angina?

Answer 4

MIs have troponin rises, unstable angina does not

Question 5

What is the difference between a STEMI and an NSTEMI?

Answer 5

STEMI
- ACS with ST elevation rise or a new onset LBBB

NSTEMI

• ACS with positive troponin and no ST elevation
• may show ST depression, T-wave inversion, non-specific changes or a normal ECG

Question 6

Risk factors for ACS

Answer 6

Non-modifiable 
- age
- gender
- family history of IHD before the age of 55
Modifiable 
- smoking 
- hypertension 
- hyperlipidaemia 
- obesity 
- diabetes mellitus 
- sedentary lifestyle
- cocaine use

Question 7

What are the and symptoms of ACS

Answer 7

Acute central chest pain
- lasts more than 20 mins 
- associated with nausea, sweating, dyspnoea and palpitations 
Sense of impending doom
Syncope 
Tachycardia 
Vomiting and sinus bradycardia 
- due to excessive vagal stimulation

Question 8

What are the signs of ACS

Answer 8

Pallor
Sweating 
Increased pulse
Decreased BP
4th heart sound added 
Signs of heart failure 
- increased JVP
- 3rd heart sound 
- basal crepitations 
- pansystolic murmur 
- pericardial friction rub

Question 9

What are the signs and symptoms of a silent MI

Answer 9

No chest pain
Syncope
Pulmonary oedema
Epigastric pain
Vomiting 
Post-op drop in blood pressure or oliguria 
Acute confusional state 
Stroke 
Diabetic hypoglycaemic states

Question 10

How is an ACS diagnosed

Answer 10

2 out of 3

• suggestive history (s/s and risk factors)
• ECG changes (new ischaemia, q waves)
• troponin rise

Question 11

ACS differentials

Answer 11

Cardiac
- stable angina
- pericarditis 
- myocarditis 
- aortic dissection 
- takotsubo cardiomyopathy
Pulmonary
- PE
- pneumothorax 
- pleuritc chest pain
Oesphageal 
- reflux/spasm 
- tumour

Question 12

Investigations for ?ACS

Answer 12

ECG
CXR - may show cardiomeagly or widened mediastinum
Bloods
- FBS, U&Es, glucose, lipids, troponins and CK/LDH
Echo
- may show regional wall abnormalities

Question 13

What troponin changes could indicate ACS?

Answer 13

Greater than x2 normal for diagnosis
Peak elevation is 12-24 hours after event
Differentiates angina and MI

Question 14

What ECG changes could you expect in an MI?

Answer 14

STEMI
- peaked T-waves
- raised ST or new LBBB
- after a few hours/days T-wave inversion and pathological q waves may develop 
NSTEMI (/unstable angina)
- ST depression 
- T-wave inversion
- non-specific changes 
- normal

Question 15

Briefly describe the management of an STEMI

Answer 15

Oxygen
Aspirin 300mg and ticagrelor 180mg
Morphine 5-10mg IV (and anti-emetic)
PPCI (if available within 120 mins)
Fibrinolysis (PCI not available within 120 mins)
- later requires angiography or rescue PCI (if fibrinolysis unsuccessful)
Secondary management

Question 16

When is a primary PCI indicated in MI?

Answer 16

Indicated in patients within 12 hours of symptom onset and within 120 minutes of first medical intervention
If not possible, the patient needs fibrinolysis followed by rescue PCI or angiogram

Question 17

When is fibrinolysis/thrombolysis given in MI?

Answer 17

If the patient doesn’t meet the criteria for a PPCI, but is still within 12 hours of initial symptom
Given within 30 mins of admission
- alteplase (tPA)
DO NOT thrombolyse on ST depression alone, T-wave inversion alone or a normal ECG

Question 18

What are the contraindications for thromboylsis?

Answer 18

Haemorrhage 
Ischaemic stroke 
AVM
Cerebral malignancy
Recent trauma/surgery 
GI bleeding 
Known bleeding disorder 
Aortic disorders

Question 19

How are patients who present >12 hours after first symptoms managed in STEMI?

Answer 19

Patients who don’t get reperfusion therapy are given fondaparinux (LMWH) or unfractioned heparin

Question 20

Breifly describe the acute management for an NSTEMI.

Answer 20

Oxygen 
Morphine 
Nitrates - GTN or tablets to dilate coronary artery 
Oral anti-platelets - aspirin 300mg
Fondaparinux 25mg
Second anti-platelet e.g. ticagrelor 180mg or clopidogrel 300mg 
IV nitrate (if pain continues) 
Oral beta-blocker e.g. bisoprolol 
Refer for angiography

Question 21

Indications for angiography post-NSTEMI

Answer 21

Urgently (<120 mins after presentation)
- ongoing angina and evolving ST changes 
- signs of cardiogenic shock
- life-threatening arrythmias
Early (<24h)
- GRACE score >140 and a high risk patient 
Routine (within 72h)
- lower-risk patient

Question 22

What makes a patient high risk in ACS?

Answer 22

Over the age of 60y
Previous stroke, TIA, MI or CABG
Known coronary artery stenosis (greater than 50% in 2 or more vessels)
Diabetes
Peripheral artery disease
Chronic kidney disease

Question 23

What is the secondary prevention required post-MI?

Answer 23

Modify risk factors 
COBRA
- Clopidogrel (at least 12 months)
- Omega 3 (diet supplementation) 
- Bisoprolol (peripheral vasodilation reduces cardiac output)
- Rampiril (reduces BP and risk of CKD)
- Aspirin (at least 12 months)
- Atorvastatin (regardless of cholesterol level)

Question 24

What are the complications after/during an MI?

Answer 24

Cardiac arrest
Cardiogenic shock
Left ventricular failure 
Bradyarrhyhtmia  
Tachyarrhythmia 
Right ventricular failure
Pericarditis 
Systemic embolism 
Cardiac tamponade 
Mitral regurgitation 
Ventricular septal defect 
Late malignant ventricular arrhythmia
Dressler's syndrome 
Left ventricular aneurysm