Myocardial Infarction Flashcards
What is a myocardial infarction?
Rapid development of myocardial necrosis due to a critical imbalance between oxygen supply & myocardial demand.
• Also known as a Heart attack.
• The most important form of IHD (ischemic heart disease)
• One of the major cause of mortality around the world.
Clinical symptoms of MI
- May or may not present with angina pectoris.
- Dyspnoea: due to pulmonary congestion caused by impaired contractility
- Diaphoresis (profuse sweating).
- Rapid, weak pulse.
- Anxiety.
Causes of MI and factors responsible
The primary cause for Ml is CORONARY ARTERY OCCLUSION.
Factors responsible are:
1. Coronary atherosclerosis
- Vasospasm:
• Platelet aggregation
• Cocaine abuse - Emboli
• AF (in atrial fibrillation the atria do not contract effectively causing blood stasis which increases the risk of thrombus formation)
• Left sided mural thrombus (a mural thrombus is a clot that forms along the wall of a heart chamber or blood vessel)
• Vegetations of infective endocarditis (Vegetations are clumps of platelets, fibrin, microorganisms, and inflammatory cells that form on heart valves or endocardial surfaces in infective endocarditis)
Ischemia without detectable CA & thrombosis
• Vasculitis of intramural vessels
• Sickle cell disease
• Amyloidosis
• Vascular dissection
• Low systemic BP(shock)
Cardiac markers for MI (enzyme and non-enzyme)
• Enzymes
- Creatine kinase (MB fraction)
- Aspartate transaminase (AST)
- Lactate dehydrogenase
• Non-enzyme proteins
- Troponin T & I
- Myoglobin
WHO DIAGNOSIS OF MI
Requires atleast 2 of the following criteriae:
- Prolonged ischemic-type chest discomfort.
- Serial ECG changes.
- Elevation of cardiac markers in serum.
TREATMENT: Initial treatment
1.Morphine (2.5-5.0 mg i.v) - For sudden relief of pain & anxiety.
- Aspirin (162-325 mg orally) - For prevention of thrombus extension, embolism, venous thrombosis.
- O2 inhalation & assisted respiration, if needed.
4.I.V fluids - Maintain blood volume & perfusion.
Treatment: Subsequent Management
- Treatment of complications:
•Arrhythmias
•Pump failure
•Thromboembolism
•Acidosis - NaHCO, i.v infusion - Secondary prevention of further consequences
& future MI.
Prevention & Treatment of Arrhythmia
- B-blocker
- Prophylactic i.v infusion
• Inj. Atenolol(50 mg)
- oral administration for few days
• Tab. Atenolol(50 mg)
- Reduce incidence of arrhythmia & mortality
Note: ß-blockers used early in evolving Mi can reduce the infarct
size & subsequent complications - Other Antiarrhythmics
- Lidocaine, Procainamide for tachyarrhythmia
Note: Bradycardia & Heart block may be managed with
Atropine or electrical pacing.
Pump Failure
- The objective is to G.O and/or filling pressure without
unduly increasing cardiac work or reducing B.P. - The drugs include:
• Furosemide: Reduce preload & pulm. edema.
• Vasodilators:
-GTN (glyceryl trinitrate), Sodium Nitroprusside - Reduce venous return.
dardiac work load.
• Inotropic agents:
-Dopamine, Dobutamine
-Augment the pumping action of heart.
Thrombolysis & Reperfusion
- First infarct patient • Inj. Streptokinase - 15,00,000 units i.v infusion over 1
hour. - Subsequent infarcts
• Recombinant tissue plasminogen activator(Alteplase). • Regimen for coronary thrombolysis is 15 mg i.v followed by 0.75 mg/kg over 30 min, & 0.5mg/kg over
following hour:
Fibrinolytics
Urokinase
Streptokinase
Alteplase
Adverse reactions to fibrinolytics
• Bleeding
• Nausea, vomiting
• Multiple micro emboli • Allergic reactions - Streptokinase is
antigenic - cause anaphylaxis
Thrombolysis & Reperfusion
- First infarct patient
• Inj. Streptokinase - 15,00,000 units i.v infusion over 1 hour. - Subsequent infarcts
• Recombinant tissue plasminogen activator(Alteplase).
• Regimen for coronary thrombolysis is 15 mg i.v followed by 0.75 mg/kg over 30 min. & 0.5mg/kg over following hour.
Contraindications to fibrinolytics
:
• Haemorrhagic diathesis
• Pregnancy
• Recent symptoms of peptic ulcer / GI
bleeding
• Recent stroke (Previous 3 mths)
• Recent surgery (Previous 10-14 days)
• Proliferative Diabetic retinopathy
• Severe uncontrolled hypertension
• Aortic dissection
• Acute pancreatitis
Long term Treatment
The objectives include:
• Prevention of remodeling & subsequent CHF. - ACE inhibitors / ARBs are of proven efficacy & afford
long term survival benefit.
• Prevention of future attacks.
- Platelet inhibitors: - Aspirin or Clopidogrel given on long term basis are
routinely prescribed.
- B blockers:
- Reduces risk of reinfarction, CHF & mortality
- Given for at least 2 years unless contraindicated
- Control of hyperlipidemia
- Hypolipidemic drugs, especially statins.
- Dietary substitution with unsaturated fats.
