CARDIAC DISEASECLINICAL BIOCHEMISTRY

Learning Objectives

• Explain the etiology of Myocardial infarction (MI).

• List out the symptoms of MI.• Elaborate the tests to investigate the disease.

Myocardial Infarction

• Heart attack= MI= death of heart muscle from the sudden blockage of a coronary artery by blood clot

• Blockage; injury; chest pain & pressure; muscle death; scar tissue.

Etiology

• Atherosclerosis with occlusive or partially occlusive thrombus formation

Symptoms of MI

1)Chest painSqueezing, aching, burning or sharp painMore than 30 min: infarctionAssociated with nausea, vomiting, dyspnea,

fatigue or palpitationsAtypical chest pain common in diabetes and

elderly patients

2)Shortness of breathAnginal equivalent or symptom of heart

failureDue to elevated end-diastolic pressure; lead

to elevated pulmonary pressure

3)Atypical presentationsCommon and lead to misdiagnosesAbdominal discomfort or jaw pain may

presentElderly patient may present with altered

mental statusWomen present more common atypical

symptoms

Physical Examination of MI

• Low grade fever• Hypo or hypertension• 4th heart sound (S4) may be heard• Dyskinetic cardiac bulge• Systolic murmur can be heard• Cool, clammy skin and diaphoresis• Signs of CHF

Risk Factors

1)Non modifiable risk factorsFamily history of premature coronary heart

disease

2) Modifiable risk factors Smoking Diabetes mellitus Hypertension Dyslipidemia Obesity Sedentary life Psychosocial stress Poor oral hygiene

3) Non atherosclerotic causes Vasculitis Coronary emboli Congenital coronary anomalies Coronary trauma Coronary spasm Drugs Factors that increase O2 requirement & decrease O2 delivery

Lab Investigation

• Cardiac enzymes• Troponin levels• Myoglobin levels• Lipid profile• ECG

Cardiac Enzymes

• Creatine kinase: 3 isoenzymes• CK-MB: mainly in heart• Serial measurement of CK-MB for diagnosis MI• CK-MB: increase within 3-12 hours of onset, peak values

within 24 hours, return baseline after 48-72 hours• High sensitivity & specificity (but not as high as Trop T)

Troponin

• Greater sensitivity & specificity• Role in diagnostic and prognostic• Positive troponin levels virtually diagnostic of

MI• Trop T: increase within 3-12 hours from onset,

peak at 24-48 hours, return baseline over 5-14 days

Myoglobin

• Urine myoglobin: rise within 1-4 hours from onset

• High sensitive but not specific• Useful in early detection of MI in the ED

Treatment of MI

• Restoration balance between oxygen supply and demand

• Pain relief• Prevent and treat complications

QUESTIONS :

• Discuss in a group;(1) Information about Myocardial infarction.

Discussion must include the etiology, symptoms, physical examination and risk factor.(2) Elaborate the tests to investigate the disease.