Emergency Medicine: AMI

Acute ST Segment Elevation MI

Problem Based Approach

A 65 year old farmer is brought to the local emergency department with his wife by the local police. Apparently he developed a “twinge of chest pain” while shoveling grain 3 hours ago. He insisted on staying at home until “he collapsed on the floor”. Even then, he wanted to stay home and rest, but his wife insisted on calling 119. The call was answered by police department, and a police officer rushed him and his wife to ER at the hospital. At his admission, he states that the pain is “almost gone”-“what a fuss about nothing.” On a history, he tells the ER physician that he smokes two packs of cigarettes daily, that he drinks a goodly amount of beer and that he had been told that his serum cholesterol level is good; the doctor even told him that his was one of the best values he had ever seen for a man his size and age.  On further questioning, he admits to a dull, aching, viselike pain around his chest radiating to the left shoulder. He also discloses that when the pain was at it worse, he experienced nausea and vomiting, must be due to something he ate last night. His wife adds that she has never seen him in so much pain, but he is a “stubborn old goat”

He still insists that it is just a little stomach trouble, but on physical examination he is sweating and diaphoretic. He also vomited twice since coming to ER. His blood pressure is 165/102 mm Hg, and his pulse is 120 irregular. His abdomen is obese. There is no neurological deficit. On Chest examination, bilateral air entry is good and there is no added sound. First and second Heart sound is audible in all auscultatory area and there is no murmur.

Approach

1/ First, ascertain that the patient’s airway is patent (Talk to patient, vomit or any blockage) and administer 100% oxygen.

2/Do an ECG: 

12 lead ECG  

•       The 12-Lead ECG sees the heart from 12 different views.

•     helps you see what is happening in different portions of the heart.

Leads placement

The limb augmented leads “see” electrical activity moving inferiorly (II, III and aVF), to the left (I, aVL) and to the right (aVR).

Precordial leads “see” electrical activity in the  posterior to anterior direction.

Now, using these 3 diagrams let’s figure where to look for a lateral wall and inferior wall MI.

Putting all together: what is it?

Look at again:

Look at some posibilities: 
This patient most likely has suffered an anterolateral wall MI. The history suggest that he is at high risk for infarct and ECG finding confirm the diagnosis.
 An acute inferior wall MI would have ST segment elevation and possible Q wave in the inferior leads. Acute Pericarditis would have ST segment elevation in all leads. Musculoskeletal chest wall pain does not produce the abnormalities in the ECG that are seen in this patient.

Think of thrombolytic therapy:

Thrombolytic therapy should be administered only when the following criteria are met
1/Typical Chest pain suggestive of an Myocardial Infarction
2/ ECG confirming  MI
3/The Absence of other disease that would explain the symptom
Now Look At the Contraindication of thrombolysis:
1/Active internal bleeding
2/Suspected Aortic Dissection
3/Rescent Head Trauma or known intracranial neoplasm
4/Haemorrhaegic Retinopathy
5/Trauma or surgery within the past 2 weeks
6/History of recent(6 months or less) stroke
7/Prolonged or traumatic Cardiorespiratory Resuscitation

How much time you have?:

Greatest Benifit would be acheived if administered thrombolytic therapy within 1-3 hours, but upto 12 hours,10 % mortality benefit can be acheived.

Please note there is no benefit documented for thrombolytic therapy in Non Q wave infarcts, nor for patient with histroy of having Coronary Artery Bypass Graft. 

ADMINISTER FIBRINOLYTIC AGENTS SUCH AS STREPTOKINASE OR ALTEPLASE (t-PA):
Recommended dose:
   1) Streptokinase in AMI : 1.5 million U over 30-60 minutes
   2)Altepase in AMI: 15 mg IV bolus, then o.75 mg/ kg over 30 minutes   (maximum  50 mg), and then o.5 mg/kg for a 60 minute period (maximum 35 mg).


Role of Concomitant Heparin use :

1. In initial treatment of AMI, use of heparin for early and effective anticoaglation  maitains t-PA-induced coronary artery patency more effectively than ASPIRIN alone; high patency result upto 95% were noted in some subgroup analysis.
2. Two most important indications for concomitent use of HEPARIN
           i) acute anterior wall MI
           ii) echocardiographic evidence of left ventricular thrombi
3. It is better to avoid use heparin with streptokinase (except aforesaid indication).
4. Use either low molecular-weight heparin or unfractionated heparin.

ASpirin as ADJUNCTIVE agent:

ISIS-II study showed that ASA reduced mortality by 25%. However,when ASA was added to streptokinase,the effect was synergistic,and mortality from MI was reduced by 42%.

Other modalities of treatment:
Primary Angioplasty with stenting,with addition of glycoprotein IIb/IIIa inhibitor abciximab.

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