MI/ Acute coronary syndrome

Question 1

What is acute coronary syndrome

Answer 1

• Includes unstable angina, evolving MI, STEMIs and NSTEMIs - (non)-ST-elevation MI

Question 2

How common is it

Answer 2

5 in 1000 for STEMI (0.5%)

Question 3

What causes ACS

Answer 3

• Always through plaque rupture –> thrombosis + inflammation
• NSTEMI/UA –> Plaque ruptures –> platelets bind –> >70% narrowing = chest pain, down stream ischaemia
• STEMI = 100% occlusion = Infarct
• Very rarely - emboli, coronary spasm, vasculitis

Question 4

Which part of the myocardium is affected first

Answer 4

Subendocardial tissue followed by subepicardial

Question 5

What are the symptoms of ACS

Answer 5

• Chest pain lasting >20 mins (oft unresponsive to GTN)
• Radiate –> neck + L arm
• Nausea, sweating, dyspnoea, palpitations
• ELDERLY/DIABETIC - present atypically

Question 6

What are the signs of ACS

Answer 6

• Distress, pallor, sweat
• Thread pulse increase
• Lower BP
• 4th heart sound

Question 7

What is the history, ECG and troponin levels in unstable angina

Answer 7

• increasing freq angina, unpredictable at rest, chest pain >20mins
• Normal ECG, ST depression or T wave changes
• Normal troponin

Question 8

What is the history, ECG and troponin levels for NSTEMIs

Answer 8

• Chest pain >20mins
• ST DEPRESSION or T wave INVERSION
• Increased troponin

Question 9

What is the history, ECG and troponin levels for STEMIs

Answer 9

• Chest pain >20mins
• ST elevation, new LBBB
• Increased troponin

Question 10

What are the differential diagnoses

Answer 10

-Angina, pericarditis, myocarditis, aortic dissection , PE, oesophageal reflux or spasm

Question 11

What investigations do you do

Answer 11

ECG

Biochemical markers - creatinine-kinase, troponin, myoglobin

Question 12

What do you look for in an ECG

Answer 12

• Classically tall T waves, ST elevation, new LBBB w/in HRS of ACS
• T wave inversion + development of pathological Q waves over next DAYS
• 20% normal
• Other ACS: ST depression + T wave inversion = highly suggestive

Question 13

What is the significance of biochemical markers

Answer 13

• Creatinine-kinase MB –> present in low levels in pt w. skeletal damage, prolonged exercise, hypothyroidism etc.
• Cardiac troponin –> mAb against troponin-T (peaks at 12-24hrs) and I
  • If troponin-T normal >6hrs after onset of pain + ECG normal = no MI
• Myoglobin –> useful for rapid diagnosis of ACS rel early in MI but not specific (also found in muscle)

Question 14

What treatment do you give to ACS (immediate action and monitoring)

Answer 14

• HIGH RISK = urgent coronary angiography
• LOW RISK = aspirin, clopidogrel, BB (atenolol) + nitrates

IMMEDIATE ACTION = ROMANCE

• Reassure
• Oxygen
• Morphine - vasodilatory, anti-emetic
• Aspirin
• Nitrates - GTN
• Clopidogrel
• Enoxaprin - LMWH
• ECG (STEMI = 1o PCI, NSTEM = elective PCI after 48hrs stabilisation w. ACEi, BB, statin, LMWH)

MONITORING

• Prophylaxis against VTE
• Starts B-Blockers (atenolol) to reduce pulse to <60 for yr
• Start Statin
• Consider clopidogrel 12 months if STEMI
• Continue ACEi
• Address modifiable factors

Question 15

What are the complications that can arise

Answer 15

• Cardiac arrest
• POST MI PERICARDITIS - DRESSLER’S SYNDROME - recurrent pericarditis
• HF (LVF)
• cardiogenic shock (inadequate organ perfusion)
• VSD
• Mitral regurg
• Cardiac arrhythmias
• Conductive disturbances