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Chapter 6. The Coronary Circulation

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Which intracoronary parameter has been shown to be the least influenced by hemodynamic changes?

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A. Coronary flow reserve (CFR)

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B. Fractional flow reserve (FFR)

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C. Instantaneous wave-free ratio (iFR)

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D. Resting distal coronary pressure/aortic pressure (Pd/Pa)

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The correct answer is B.

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Both animal and human studies have shown that FFR is the only parameter that is highly independent of hemodynamic variations such as heart rate, blood pressure, and contractility. The reason that FFR is fundamentally different than CFR, iFR, and resting Pd/Pa is that it is the only parameter that is not dependent on resting flow.

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In the normal heart at rest, an increase in coronary perfusion pressure of 20% will result in which of the following?

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A. An increase in myocardial blood flow by about 20%

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B. An increase in myocardial blood flow by about 40%

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C. A decrease in myocardial blood flow by about 20%

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D. No change in myocardial blood flow

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The correct answer is D.

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Coronary autoregulation keeps coronary flow constant despite changes in coronary perfusion pressure, between a mean aortic pressure of 50 and 130 mm Hg.

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In the normal heart during maximal hyperemia, an increase in coronary perfusion pressure of 20% will result in which of the following?

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A. An increase in myocardial blood flow by about 20%

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B. An increase in myocardial blood flow by about 40%

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C. A decrease in myocardial blood flow by about 20%

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D. No change in myocardial blood flow

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The correct answer is A.

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During maximal hyperemia (eg, induced by adenosine, severe ischemia, or a perfusion pressure out of the autoregulatory range), autoregulation is exhausted, and therefore, perfusion pressure is proportionally related to coronary flow.

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What is the accuracy of the coronary angiogram to predict whether a coronary stenosis is able to induce myocardial ischemia?

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A. 70%

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B. 80%

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C. 90%

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D. 95%

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The correct answer is A.

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