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Tuesday, December 4, 2012

Myocardial infarction (MI)


The complete necrosis of the myocardium due to complete cessation (occlusion) of blood supply is called myocardial infarction.


·         Atherosclerotic plaque (unstable)
·         Embolic occlusion of coronaries
·         Severe and prolonged vasospasm
·         Drugs (Cocain and Amphetamine)

Clinical features:


Ø  Chest pain
o   Severe and prolonged means more than 30 min not relieved with nitrates
o   Left side of chest and then radiates to left arm to left arm or back or neck
Ø  Vomiting
Ø  Sweating
Ø  Symptoms of heart failure in case of massive MI
o   Dizziness
o   Drowsiness
o   Severe shortness of breath
o   Unconsciousness (in some cases)


§  Fist sign
§  Sweating/ diaphoresis
§  Vomiting
§  BP will be either increased or decreased
§  Pulse:
o   Tachycardia: Due to anxiety, low cardiac output or arrhythmias
o   Bradycardia: If there is inferior wall infarction
§  Chest (pericardium) examination:
Usually normal examination of the heart or having the following
o   Ventricular septal defect (VSD)
o   Pain systolic murmur (PSM)
o   A soft first heart sound
o   Fourth heart sound
o   Third heart sound reflects left ventricular dysfunction
§  Lungs:
Crepts at the bases of lungs

Investigation of MI:


Ø  ST segment elevation
Ø  May be tachycardia or bradycardia
o   V3-V4 show anterior wall MI due to LAD involvement
o   II, III, aVF show inferior wall MI due to RCA involvement
o   I, aVL show high lateral wall MI due to circumflex

Cardiac enzymes:

Troponin T and I are raised up to 2 weeks while CK-MB remains elevated up to 3 days. Creatine kinase (CK) has three isoenzymes.
§  CK-MB: present in heart
§  CK-MM: present in skeletal muscle
§  CK-BB: present in brain


ü  It asses the myocardial movements i.e. whether Hypokinetic or Akinetic (no movement)
ü  It also asses the valves, whole function of the heart and aorta.

Routine investigation:

·         CBC (Complete Blood Count)
·         RBS (Random Blood Sugar)
·         Urea, creatinine
·         Serum electrolytes (especially K)
·         Cardiac X-ray


All the patients with suspected myocardial infarction should be confined to strict bed rest and admitted in hospital preferably in CCU.


v  The aim of general treatment is to relieve the symptoms.
v  To relieve the pain, so strong analgesics especially opoid group (Morphine, codein) and anti-emetics (Gravinate) are used.
v  Complete bed rest for 24 hrs.
v  To treat other co-morbidities (diseases like HTN, DM)



Aspirin 300mg and clopidogril 300 mg are given as first (loading) dose then 75mg OD.


§  Streptokinase
§  If once it is used then the patient become allergic to it

Beta blockers:

Atenolol, Propranolol, Metaprolol (cardio selective)


Angised, isoket (nitroglycerine) should be given to relieve chest discomfort.

ACE inhibitors (Angiotensin Converting Enzymes):

They prevent or at least reduce the left ventricular dilatation and cardiac failure following myocardial infarction. These are Ramipril and Captopril (Tab. Capoten 25mg).


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