IHD Patho 2012_Student Version (2)

Myocardial ischemia inadequate supply of o 2 to meet

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Myocardial Ischemia • Inadequate supply of O 2 to meet myocardial O 2 demand (MVO 2 ) O O 2 demand in face of fixed supply causes ischemia demand in face of fixed supply causes ischemia PAIN! PAIN! If ischemia transient or quickly reversed Myocardium is salvageable and viable
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Myocardial Oxygen Demand Major determinants of MVO 2 Heart rate Myocardial contractility Intramyocardial wall tension Exercise Increases MVO 2
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Myocardial Oxygen Demand  Heart rate (chronotropy) Direct relationship Myocardial contractility (inotropy) Direct relationship
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Myocardial Oxygen Demand Intramyocardial wall tension Intraventricular pressure, left ventricular (LV) radius (direct relationship) BP or LV dilation wall tension MVO 2 Ventricular wall thickness (indirect relationship) LV hypertrophy wall tension MVO 2
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Myocardial Oxygen Supply Coronary blood flow Arteriolar resistance resistance coronary blood flow Coronary perfusion pressure perfusion pressure coronary blood flow
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Factors that Exacerbate  Myocardial Ischemia These factors are especially important in chronic stable angina – where pain is predictable and provoked by exercise or increased stress. There are medications that patients can take to balance myocardial supply and demand to help reduce the frequency of chest pain.
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Coronary Arteries Main coronary arteries Left main (LM) coronary artery Left anterior descending (LAD) artery Left circumflex (LCx) artery Right coronary artery (RCA)
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Coronary Arteries Photo adopted from: http://www.images.md.proxy1.lib.tju.edu:2048/users/image_show.asp
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Coronary Arteries Overall prognosis is largely dependent on the number of coronary vessels obstructed Greater number obstructed = worse outcomes Average 12-year survival Zero vessel disease = 88% One vessel disease = 74% Two vessel disease = 59% Three vessel disease = 40% Other factors that risk of death: Heart failure (low EF) Smoking Left main CAD Diabetes Prior MI Other factors that risk of death: Heart failure (low EF) Smoking Left main CAD Diabetes Prior MI
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Checkpoint Question A patient with chronic stable angina would be more likely to have a coronary artery plaque with the following properties: A. Thick fibrous cap, thick lipid core B. Thin fibrous cap, thin lipid core C. Thick fibrous cap, thin lipid core D. Thin fibrous cap, thick lipid core
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Nonmodifiable Risk Factors Age Men 45 yr Women 55 yr Family history of premature CAD Includes history of MI or sudden death Father or 1 st degree male relative < 55 yr Mother or 1 st degree female relative < 65 yr
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Modifiable Risk Factors Smoking risk of: MI Sudden cardiac death Cerebrovascular disease
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Myocardial Ischemia Inadequate supply of O 2 to meet...

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