Cardiac Physiology
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Questions and Answers

What percentage of the transthoracic diameter does the heart occupy in the frontal plane on a chest X-ray?

  • Less than 50% (correct)
  • Less than 30%
  • More than 50% (correct)
  • Less than 70%

    • Which of the following forms the cardiac silhouette on the left side?

  • Aortic arch, pulmonary trunk, right atrial appendage, and RV
  • Aortic arch, pulmonary trunk, left atrial appendage, and LV (correct)
  • Right ventricle, left ventricle, aortic arch, and pulmonary trunk
  • RA, RV, aortic arch, and pulmonary trunk

    • What is the percentage of right-dominant circulation?

  • 80% (correct)
  • 40%
  • 60%
  • 50%

    • Which artery supplies the sinoatrial (SA) node?

    <p>SA nodal artery</p> Signup and view all the answers

    What is the percentage of left-dominant circulation?

    <p>15%</p> Signup and view all the answers

    Which structure acts as a priming pump for the ventricles?

    <p>Atria</p> Signup and view all the answers

    What is the percentage of balanced circulation?

    <p>5%</p> Signup and view all the answers

    Which artery supplies the AV node?

    <p>AV nodal artery</p> Signup and view all the answers

    What is the normal range of stroke volume in an average person?

    <p>40-70 ml</p> Signup and view all the answers

    What is the term that refers to the measurement of how much blood is being pumped out of the left ventricle of the heart?

    <p>Left ventricular ejection fraction</p> Signup and view all the answers

    What is the normal range of left ventricular ejection fraction?

    <p>55-70%</p> Signup and view all the answers

    What does a LVEF of 65 mean?

    <p>65% of the total amount of blood in the left ventricle is pumped out with each heartbeat</p> Signup and view all the answers

    What is a possible diagnosis if the LVEF is less than 40%?

    <p>Heart failure</p> Signup and view all the answers

    What is the possible risk if the LVEF is less than 35%?

    <p>Life-threatening irregular heartbeats</p> Signup and view all the answers

    What may be recommended for patients with an LVEF of less than 35%?

    <p>Implantable cardioverter defibrillator (ICD)</p> Signup and view all the answers

    What is the factor that affects cardiac output?

    <p>All of the above</p> Signup and view all the answers

    What is the location of the SA node in the heart?

    <p>At the junction of the SVC and the roof of the RA</p> Signup and view all the answers

    What is the function of the AV node in the heart?

    <p>To conduct electrical impulses from atria to ventricles</p> Signup and view all the answers

    What is the effect of increased sympathetic nerve activity on the heart?

    <p>Increased heart rate and contractility</p> Signup and view all the answers

    What is the effect of parasympathetic nerve activity on the heart?

    <p>Decreased heart rate and contractility</p> Signup and view all the answers

    What is the equation for cardiac output?

    <p>CO = HR x SV</p> Signup and view all the answers

    What is the normal cardiac output in liters per minute?

    <p>5 liters per minute</p> Signup and view all the answers

    What is the bundle of His divided into?

    <p>Left bundle branch (LBB) and right bundle branch (RBB)</p> Signup and view all the answers

    Which of the following is NOT a location where parasympathetic nerves innervate?

    <p>Ventricular myocardium</p> Signup and view all the answers

    Study Notes

    Cardiac Physiology

    Heart Structure and Function

    • The heart acts as two serial pumps, sharing electrical and mechanical components.
    • The right heart circulates blood to the lungs for oxygenation, and the left heart circulates it to the rest of the body.
    • Atria are thin-walled structures acting as priming pumps for ventricles, which provide most of the energy to maintain circulation.
    • Ventricles are thick-walled structures adapted to circulating blood through large vascular beds under pressure.

    Radiological Features

    • The heart occupies less than 50% of the transthoracic diameter in the frontal plane on a chest X-ray.
    • The cardiac silhouette on the left is formed by the aortic arch, pulmonary trunk, left atrial appendage, and LV.
    • The cardiac silhouette on the right is formed by the RA, superior and inferior venae cavae, and the lower right border is formed by the RV.

    Coronary Circulation

    • The conventional arterial supply to the heart arises from the right and left coronary arteries, which originate from the root of the aorta.
    • The right coronary artery (RCA) gives off conus, acute marginal, AV nodal, and posterior descending arteries.
    • The left coronary artery (LCA) gives off LAD, septal, diagonal, LCx, and obtuse marginal branches.
    • Dominance of circulation is determined by whether the RCA or LCA supplies the posterior descending artery (PDA).
    • Right-dominant circulation: PDA and at least one posterolateral branch arise from RCA (80%).
    • Left-dominant circulation: PDA and at least one posterolateral branch arise from LCA (15%).
    • Balanced circulation: Dual supply of posteroinferior LV from RCA and LCA (5%).

    Conduction System

    • The sinoatrial (SA) node is located at the junction of SVC and roof of RA, governing pace-making.
    • The SA node is supplied by the SA nodal artery, which may arise from RCA (60%) or LCA (40%).
    • The AV node is located within the triangle of Koch and is supplied by the AV nodal artery, which may arise from RCA (90%) or LCA (10%).
    • The AV node connects to the bundle of His, which divides into LBB and RBB.
    • LBB further splits into anterior and posterior fascicles.
    • RBB and fascicles of LBB give off Purkinje fibers conducting impulses into ventricular myocardium.

    Cardiovascular Innervation

    • Sympathetic nerves innervate the SA node, AV node, ventricular myocardium, and vasculature, increasing heart rate and contractility.
    • Parasympathetic nerves innervate the SA node, AV node, and atrial myocardium, slowing heart rate and reducing AV conduction.

    Cardiac Output

    • Cardiac output (CO) is the volume of blood pumped by each ventricle in one minute, normally 5 L/min.
    • CO = HR x SV.
    • CO depends on heart rate, preload, afterload, and contractility.

    Stroke Volume and Ejection Fraction

    • Stroke volume (SV) is the volume of blood pumped by each ventricle in one beat, normally 70 mL.
    • Ejection fraction (EF) is the percentage of blood pumped out of the ventricle with each beat, normally 55-70%.
    • LVEF is the measurement of how much blood is being pumped out of the left ventricle.
    • RVEF is the measurement of how much blood is being pumped out of the right side of the heart to the lungs.
    • An EF of less than 40% may confirm a diagnosis of heart failure.

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    Related Documents

    Cardiac Physiology L1 PDF

    Description

    Understand the heart's function as two serial pumps, its electrical and mechanical components, and the role of atria and ventricles in maintaining circulation.

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