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Ischemic Heart Disease

Chapter 6, pg.131-156

The Objectives for this assignment are combined with the ones from Chapter 5 on Atherosclerosis. The two subjects go hand-in-hand, but I’ll try not to overlap with Ashley too much. Here are the objectives restricted to my section:

  • 1.

    Identify the major determinants of myocardial oxygen supply and demand; describe the rationale, pathophysiology and clinical utility of exercise stress testing

  • 2.

    Describe the epidemiological characteristics of ischemic heart disease

  • 3.

    Develop a rational plan for evaluation and management of a patient with chest pain

Intro and the basics:

  • Angina = condition where you have a mismatch between myocardial oxygen supply and demand.

  • The leading cause of angina is CORONARY ARTERY DISEASE

  • CAD = reduced myocardial oxygen supply due to atherosclerotic narrowing of the coronary vessels

  • Ischemic Heart Disease is the leading cause of death in the US

Objective # 1: The major determinants of myocardial oxygen supply and demand. Oxygen supply depends on

  • Oxygen carrying capacity of the blood

    • o

      This term remains constant in the absence of anemia or lung disease

  • Rate of coronary blood flow.

      • o

        This is the important one

      • o

        Recall that coronary artery flow (Q) is directly proportional to perfusion pressure (P) and inversely related to coronary vascular resistance (R)

      • o

        Q=P/R

      • o

        For the coronary arteries, most of the perfusion HAPPENS DURING DIASTOLE!!

      • o

        This is because during contraction of the myocardium during systole, the coronary vessels are mashed closed when the muscle contracts (and I think Dr. Faber said that the blood can’t enter the coronary vessels from the aorta when the velocity of systole is so great. Did I make that up?)

      • o

        So, blood enters the vessels during diastole when the myocardium is relaxed and the vessels aren’t compressed.

      • o

        We can approximate the perfusion pressure of the coronaries by measuring the aortic diastolic pressure

        • Things that change the aortic diastolic pressure will thus change the perfusion pressure of the coronaries

        • EX: hypertension, aortic regurg will decrease aortic diastolic press.

      • o

        The other key determinant in blood flow is coronary vascular resistance

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