LEARNING OBJECTIVES
CARDIAC FUNCTION
4
Understanding the concepts presented in this chapter will enable the student to:
1.
Describe the basic anatomy of the heart, including the names of vessels enter-
ing and leaving the heart, cardiac chambers, and heart valves; trace the flow of
blood through the heart.
2.
Describe the changes in cardiac pressures and volumes, and associated electri-
cal events and heart sounds, that occur during one cardiac cycle.
3.
Draw and label ventricular pressure-volume loops derived from ventricular
pressure and volume changes during the cardiac cycle.
4.
Calculate stroke volume, cardiac output, and ejection fraction from ventricular
end-diastolic and end-systolic volumes and heart rate.
5.
Describe the factors that determine or modify ventricular preload, afterload,
and inotropy.
6.
Show how changes in preload, afterload, and inotropy affect ventricular end-
diastolic volume, end-systolic volume, and stroke volume by using Frank-
Starling curves and ventricular pressure-volume loops.
7.
Describe how changes in preload, afterload, and inotropy alter the length-
tension and force-velocity relationships for cardiac muscle.
8.
Calculate myocardial oxygen consumption given coronary blood flow, and corO'
nary arterial and venous oxygen contents.
9.
Explain how changes in stroke volume, stroke work, afterload, heart rate, and
inotropy affect myocardial oxygen consumption.
INTRODUCTION
The heart is a specialized muscular organ
that rhythmically contracts and pumps blood
from the low-pressure venous side to the high-
pressure arterial side of the circulation. Efficient
pumping occurs because of the orderly contrac-
tion sequence of the different heart chambers
and the presence of valves within the heart that
ensure a unidirectional flow of blood. This chap-
ter describes the basic anatomy of the heart—its
chambers, valves, and vessels entering and leav-
ing the heart—and the sequence of electrical
and mechanical events that occur during a cycle
of contraction and relaxation. It then describes
the mechanisms that regulate cardiac output,
particularly those mechanisms that influence
the amount of blood ejected into the aorta with
each contraction of the left ventricle. The last
section of this chapter discusses the relationship
between myocardial oxygen consumption and
the mechanical activity of the heart.
CARDIAC ANATOMY
Functional Anatomy of the Heart
The heart consists of four chambers: right
atrium, right ventricle, left atrium, and left ven-
tricle (Fig. 4.1). The right atrium receives blood
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CHAPTER
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