MANAGEMENT OF MYOCARDIAL INFARCTIONSAMEEH SAIFUDHEEN
INTRODUCTION• Rapid development of myocardial necrosis due to acritical imbalance between O2 supply & myocardialdemand.• Also known as “Heart attack”.• The most important form of IHD.• One of the major cause of mortality around theworld.
CAUSES• The primary cause for MI is CORONARY ARTERYOCCLUSION.• Factors responsible are:– Coronary atherosclerosis– Vasospasm• Platelet aggregation• Cocaine abuse.– Emboli• AF• Lt. sided mural thrombus• Vegetations of inf. endocarditis
– Ischemia without detectable CA & thrombosis• Vasculitis of intramural vessels• Sickle cell disease• Amyloidosis• Vascular dissection• Low systemic BP(shock)
CLINICAL FEATURESClinical symptoms:– May or may not present with angina pectoris.– Dyspnoea• due to pulmonary congestion caused by impairedcontractility .– Diaphoresis(profuse sweating).– Rapid, weak pulse.– Anxiety.
Marker Abnormal activitydetectable(hr)Peak value ofabnormality(hr)Duration ofabnormality(days)CK-MB 3-8 10-24 2-3LD 8-12 72-144 8-14AST 6-12 24-48 4-6MYOGLOBIN 1-3 6-9 1TROPONIN ITROPONIN T3-83-824-4872-1003-55-10CARDIAC MARKERS & TIME COURSE AFTER ONSET OFMI
WHO DIAGNOSIS OF MIRequires atleast 2 of the following criteriae:– Prolonged ischemic-type chest discomfort.– Serial ECG changes.– Elevation of cardiac markers in serum.
TREATMENTInitial treatment:1.Morphine(2.5-5.0 mg i.v) - For sudden relief of pain& anxiety.2.Aspirin(162-325 mg orally) - For prevention ofthrombus extension, embolism, venous thrombosis.3.O2 inhalation & assisted respiration, if needed.4.I.V fluids - Maintain blood volume & perfusion.
Subsequent Management:– Treatment of complications:•Arrhythmias•Pump failure•Thromboembolism•Acidosis – NaHCO3 i.v infusion– Secondary prevention of further consequences& future MI.
Prevention & Treatment of Arrhythmia1. β-blocker– Prophylactic i.v infusion• Inj. Atenolol(50 mg)– oral administration for few days• Tab. Atenolol(50 mg)– Reduce incidence of arrhythmia & mortalityNote: β-blockers used early in evolving MI can reduce the infarctsize & subsequent complications.
2. Other Antiarrhythmics– Lidocaine, Procainamide for tachyarrhythmiaNote: Bradycardia & Heart block may be managed withAtropine or electrical pacing.
Pump Failure– The objective is to C.O and/or filling pressure withoutunduly increasing cardiac work or reducing B.P.– The drugs include:• Furosemide: Reduce preload & pulm. edema.• Vasodilators:–GTN, Sod. Nitroprusside– Reduce venous return, cardiac 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 1hour.– Subsequent infarcts• Recombinant tissue plasminogen activator(Alteplase).• Regimen for coronary thrombolysis is 15 mg i.vfollowed by 0.75 mg/kg over 30 min. & 0.5mg/kg overfollowing hour.
Long term TreatmentThe objectives include:• Prevention of remodeling & subsequent CHF.– ACE inhibitors / ARBs are of proven efficacy & affordlong term survival benefit.• Prevention of future attacks.– Platelet inhibitors:– Aspirin or Clopidogrel given on long term basis areroutinely prescribed.
– β 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.