ACS - STEMI

Question 1

What is STEMI

Answer 1

-new and persistent ST segment elevation in at least 2 contiguous leads of >1mm in all leads other than v2-v3:
>2.5 mm in men <40
>2mm in men > 40
>1.5mm in women

Question 2

Case histories of STEMI

Answer 2

1) A 54-year-old man with a medical history of hypertension, diabetes, dyslipidaemia, smoking, and family history of premature coronary artery disease presents with retrosternal crushing chest pain (10/10 in intensity), radiating down the left arm and left side of the neck. He feels nauseated and light-headed and is short of breath. Examination reveals hypotension, diaphoresis, and considerable discomfort with diffuse bilateral crackles on chest auscultation. ECG reveals convex ST-segment elevation in leads V1 to V6
2) A 70-year-old woman is 2 days post-operative for knee replacement surgery. Her past medical history includes type 2 diabetes and a 40 pack-year history of smoking. She reports feeling suddenly unwell with dizziness, nausea, and vomiting. She denies any chest pain. On examination she is hypotensive and diaphoretic. ECG shows convex ST-segment elevation in leads II, III, and aVF with reciprocal ST segment depression and T-wave inversion in leads I and aVL.

Question 3

Diagnosis of STEMI

Answer 3

• time critical
• immediate ECG 10mins
• single loading dose of aspirin 300mg
• coronary reperfusion therapy
• primary PCI

-consider right ventricular involvement where there is a triad of hypotension, elevated JVP, clear lung fields.

• posterior STEMI = ST-segment depression in v1-v3
• complete left main coronary artery obstruction if: ST depression >1mm in >6 leads OR ST elevation in aVR or v1

Question 4

Emerging tests

Answer 4

Cardiac myosin-binding protein C (cMyC)

• released more rapidly than troponin after acute MI
• CMyC is more abundant than troponins
• may become gold standard test for early diagnosis of acute MI

Question 5

Treatment of STEMI

Answer 5

-Suspected or clinical diagnosis of STEMI (symptoms of myocardial ischaemia + ST elevation on ECG):

-aspirin 300mg
-assess eligibility for coronary reperfusion therapy
-analgesia- morphine sulfate 2.5 to 10mg intravenously OR diamorphine
-antiemetic- ondansetron 4-8mg IV OR metoclopramide 500micrograms/kg/day or 10mg IV if >60kg OR cyclizine 50mg IV
Consider:
-oxgen- if <90%
-intravenous nitrate if persistent chest pain despite glyceryl trinitrate, sustained hypertension, CHF : glyceryl trinitrate 15-20micrograms/min OR isosorbide dinitrate 2-10mg/hr

<12 hrs since symptoms onset: primary PCI available within 120minutes

• aspirin
• assess eligibility for coronary reperfusion therapy
• analgesia
• anti-emetic
• oxygen
• IV nitrate
• primary PCI, else emergency CABG
• P2Y12 inhibitor- prasugrel with aspirin if not taking anticoagulant 60mg loading dose then 5mg; OR clopidogrel 300-600mg LD then 75mg if taking anticoagulant; OR ticagrelor 180mg LD then 90mg
• parenteral anticoagulation: heparin 70-100 units/kg OR enoxaparin 0.5mg/kg OR bivalirudin 0.75mg/kg
• glycoprotein IIb/IIIa inhibitor- eptifibatide, tirofiban

<12 hrs since symptoms onset: primary PCI unavailable within 120minutes & patient eligible for fibrinolysis

• Fibrinolysis - tenecteplase 30mg if <60kg or 35mg or 40mg OR alteplase 15mg IV, streptokinase 1.5 million units IV over 30-60mins
• parenteral anticoagulation: enoxaparin 60units/kg OR heparin 60 units/kg OR fondaparinux 2.5mg IV OD
• angiography with or without PCI

POST-STEMI

• continue dual antiplatelet therapy: aspirin 75-100mg AND prasugrel 5-10mg OR ticagrelor 90mg T2 OR clopidogrel 75mg OD
• BB or non-dihydropyridine Ca-channel blocker- bisoprolol 1.25mg OR carvedilol 3.125mg T2 or verapamil 240mg T3
• ACEi or angiotensin-II receptor antagonist: enalapril 2.5mg OR ramipril 2.5mg OR lisinopril 2.5-5mg OR valsartan 20mg OR iosartan 12.5 mg OR candesartan 4mg
• statin- atorvastatin 40-80mg OR rosuvastatin 20-40mg
• aldosterone antagonist- eplerenone 25mg OR spironolactone 25mg
• cardiac rehab

Emerging
-factor Xa inhibitors