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  • • Normal coronary blood flow: 1 mL per gram of myocardium per minute

    • Oxygen extraction from coronary bed: 75% at rest, 100% during stress

    • Coronary flow primarily during diastole

    • Mean coronary resistance is 3-6 times the totally vasodilated value, implying extreme vasodilator reserve

    Atherosclerosis progression: Intimal incorporation of lipids → expanding plaque with fibrosis and calcification → finally rupture of plaque causing thrombosis → acute infarction

    • Subtotal occlusions important in pathogenesis of unstable angina

    Usual pattern

    • -Short, proximal stenoses of left coronary artery

      -In right coronary artery, disease more diffuse, involving proximal and middle portions of artery

      -Patients with type 1 diabetes mellitus have diffuse disease

    • Blood flow may be adequate at rest; exercise and stress may produce ischemia

    Acute coronary insufficiency (angina pectoris): Immediate decrease in myocardial work

    • After only 15 minutes of reversible ischemia, may take 24-48 hrs for complete recovery

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Epidemiology

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  • • Coronary artery disease responsible for 20% of all deaths

    • Cardiovascular disease accounts for > 40% of all deaths

    • Atherosclerosis identified in up to 50% of autopsies of patients in second decade of life

    Risk factors

    • -Smoking (secondhand increases death rate from coronary disease by 30%; smoking cessation decreases coronary risk by 50% after 1 year of abstinence)

      -Hypercholesterolemia

      -Male

      -Diabetes mellitus

      -Hypertension

      -Family history

      -Obesity

      -Inactivity

    • Coronary mortality rate directly proportional to number of vessels affected and LV function

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Symptoms and Signs

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  • • Retrosternal chest pain

    • -Pressure

      -Choking

      -Tightness

      -Frequently radiates down left arm, left neck, occasionally right arm, mandible, ear

    • Exercise, cold exposure, eating can precipitate symptoms

    • Stable, progressive, or unstable angina

    • Pulmonary edema from ischemia (poor prognosis)

    • Some have no symptoms (silent myocardial ischemia)

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Laboratory Findings

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  • ECG

    • -Normal in 50% of patients

      -May have inverted T waves, ST segment abnormalities, or Q waves at rest

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Imaging Findings

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  • Coronary angiography: Highest sensitivity and specificity of any test available (10% of patients underestimated)

    Screening

    • -Stress ECG

      -Stress echocardiography

      -Dobutamine echocardiography

      -Stress thallium may identify viability

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  • • Consider other causes of chest pain, including gastroesophageal reflux disease, aneurysms, aortic dissection

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  • • Screening test

    • If high suspicion, proceed to angiography

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  • Risk reduction: Smoking cessation, hypertension control, lipid reduction

    • Percutaneous transluminal coronary angioplasty (> 90% successful but repeat interventions common)

    Operative therapy: Complete revascularization associated with improved outcome

    • Evaluate carotid bruits, renal function, respiratory status, coagulation studies

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Conventional Coronary Artery Bypass Grafting (CABG)

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  • • Internal mammary (preferred), saphenous vein, or radial artery used to bypass on average 3-4 coronary vessels

    • Graft patency affected by smoking, low-density lipoprotein

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Minimally Invasive

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  • • Off-pump coronary artery bypass (OPCAB)

    • -Performed without cardiopulmonary bypass

      -Best for left anterior descending, diagonal, proximal right coronary arteries

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