Acute Coronary Syndrome (ACS)
Universal definition of myocardial infarction
The term ‘myocardial infarction’ should be used when there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischaemia, in which case any one of the following meets the diagnosis for MI:
Detection of rise and/or fall of cardiac biomarkers (preferably troponin), with at least one value above the 99thpercentile of the upper reference limit, together with at least one of the following:
Symptoms of ischaemia
ECG changes indicative of new ischaemia (new ST-Tchanges or new left bundle branch block)
Development of pathological Q waves
Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
Sudden unexpected cardiac death, involving cardiac arrest, often with symptoms suggestive of myocardialischaemia,and accompanied by presumably new ST elevation or new left bundle branch block, and/or evidence of fresh thrombus by coronary angiography and/or at autopsy, but death occurring before blood samples could be obtained or before the appearance of cardiac biomarkers in the blood
Pathological findings of an acute MI
Pathogenesis of ACS
ACS may present as a new phenomenon or against a background of chronic stable angina.
The culprit lesion is usually a complex ulcerated or fissured atheromatous plaque with adherent platelet rich thrombus and local coronary artery spasm.
This is a dynamic process whereby the degree of obstruction may either increase leading to MI or regress spontaneously due to platelet disaggregation and endogenous fibrinolysis.
Clinical features of acute coronary syndrome
Prolonged cardiac pain: chest,throat,arms,epigastrium or back
• Anxiety and fear of impending death
• Nausea and vomiting
Signs of sympathetic activation: pallor, sweating, tachycardia
• Signs of vagal activation: vomiting, bradycardia
• Signs of impaired myocardial function
Hypotension, oliguria, cold peripheries
Narrow pulse pressure
Third heart sound
Quiet first heart sound
Diffuse apical impulse
• Signs of tissue damage: fever
• Signs of complications: e.g. mitral regurgitation, pericarditis
Timely intervention is vital
Sudden death from VF or asystole may occur immediately and often within first hour.
If patient survives this most critical phase then liabilities to dangerous arrhythmias remains, but diminishes as each hour goes by.
It is vital that the patient knows not to delay calling for help if symptoms occur.
Early intervention can save life,myocardium.
Differential diagnosis of chest pain
Myocardial ischaemia (angina)
Mitral valve prolapse
DD chest pain
Connective tissue disorders (rare)
Intercostal muscle injury
Epidemic myalgia(Bornholm disease)
Prolapsed intervertebral disc
Thoracic outlet syndrome
Diagnostic workup of ACS
Serial measurements of CKMB and trop T and trop I
Other blood tests
Management of acute MI
Urgent admission to CCU
Medical treatment aspirin,clopidogrel,anticoagulation and angina therapy.
Management of pain and vomiting
Cardiac monitoring and management of arrythmias
PCI or CABG
Oral antiplatelet agents in acute coronary syndromes
Aspirin alone (75–325 mg/day) reduces the risk of death, MI and stroke in acute coronary syndromes . The addition of clopidogrel (75 mg daily) to aspirin causes a further modest reduction in these events.
Anti coagulation in acute coronary syndromes
Aspirin plus low molecular weight heparin is more effective than aspirin alone in reducing the combined endpoint of death,MI, refractory angina and urgent need for revascularisation. In comparison to low molecular weight heparin, the pentasaccharide,fondaparinux (2.5 mg s.c.), is associated with lower bleeding rates and better overall survival.
Relative contraindications to thrombolytic
therapy: potential candidates for primary angioplasty
Active internal bleeding
Previous subarachnoid or intracerebral haemorrhage
Recent surgery (within 1 mth)
Recent trauma (including traumatic resuscitation)
High probability of active peptic ulcer
Complications of MI
Post infarction angina
Acute circulatory failure and cardiogenic shock
Rupture of papillary muscles,interventricular septum or ventricle.