Download Cardiac System

Cardiovascular System
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Objectives:
1. Review the pathophysiology of the cardiac system.
2. Discuss common diagnostic tests of the cardiac system.
3. Evaluate risk factors for coronary heart disease.
4. Discuss peripheral vascular disease and treatment options.
5. Discuss the psychological needs of the “cardiac patient” and desired life style
changes.
6. Discuss dysrhythmias, heart failure, myocardial infarction, and hypertension;
manifestations of disease and treatment.
7. 7. Discuss anticoagulant therapy: drugs, purpose, monitoring, patient
education.
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Readings:
1. Lewis, Medical-Surgical Nursing: 7th edition, chapters 32-38; 6th edition,
chapters 31-37.
2. Flattery, Maureen et al, “COX-2 Inhibitors and Cardiovascular Risk,”
http://toxicology.usu.edu/endnote/Cox-2-inhibitors-cardiovascular-2005.pdf
3. Browse the American Heart Association web site:
http://www.americanheart.org/presenter.jhtml?identifier=1200000
4. Go to http://www.youtube.com/ . In the search box, enter “heart sounds.”
Explore various heart sounds on the videos available.
Please use the following outline, along with the readings, to fulfill the objectives of the
course.
Heart
A. The heart is a four-chambered muscular organ appproximately the size of
your fist.
1. Heart wall has 3 layers
a. endocardium - thin inner lining
b. myocardium - middle muscular layer
c. epicardium - outer serous layer
2. Pericardial sac surrounds the heart
a. visceral layer (inner)
b. parietal layer (outer)
c. normally, a small amount of fluid is in the sac and allows the layers to
slide over each other while the heart beats
3. 4 Chambers of the heart
a. atria - thinner than ventricles
b. ventricles - more muscular
4. Blood supply to the myocardium
a. coronary circulation
-Right coronary artery (RCA) and branches supply the right atrium, right
ventricle, and a portion of the posterior wall of the left ventricle
-Left coronary artery and its branches supply the left atrium and walls of
the left ventricle
-in 90% of individuals, the artioventicular node (AV node - part of the
conduction system of the heart, lies between the atria and ventricles) receives
blood from the RCA
-if the blood flow through any part of the coronary arterial system is
interrupted, some of the myocardium will lose the ability to function
(Myocardial Infarction)
-if the blood flow is reduced slowly. alternate routes may develop in time
to nourish the endangered myocardium (collateral circulation)
5. Myocardial Cells exhibit
a. automaticity - the ability to initiate or propagate an action potential
(change in intracellular charge)
b. excitability - the ability to respond to an electrical impulse
c. conductivity - the ability to shorten (contract) when stimulated
d. although all myocardial cells share the same characteristics, certain
specialized cells generate electrical impulses
-sinoatrial node (SA node) - the "pacemaker" of the heart
-intranodal pathways
-artrioventricular node (AV node)
-bundle of His
-Right and left bundle branches
-Purkinje fibers
e. Myocardial contraction occurs when myocardial cells depolarize - the
myocardial intracellular charge changes when the NA+ and Ca+ ions flow into
the cell and the K+ ions flow out - this change is called the action potential
f. Repolarization occurs when the K+ flows out of the cell and the cell
returns to the resting state; this requires energy for the ion-transport system
called the Na+/K+ pump
Depolarization causes myocardial cells to contract.
Repolarization causes myocardial cells to relax.
g. Innervation
-Sympathetic stimulation enhances
-excitability
-pacemaker firing rate
-conduction speed
-contractility
-Parasympathetic stimulation depresses these effects
6. Conduction System
a. starts at the SA node (normally 60-80 beats/ minute in an adult), travels
down the intranodal pathways to the AV node (can generate 40-60 beats a
minute if the SA node is unable), where it pauses briefly to allow contraction and
emptying of the atria into the ventricles before contraction of the ventricles begin.
It then travels down a thick bundle of conducting nerve fibers, called the bundle
of HIS (which is capable of initiating 20-40 beats/min if the SA node and the AV
node are unable. The bundle divides into right and left branches and ends in the
Purkinje fibers which are embedded in the myocardial tissue and this is where
the impulses are transfered to the myocardial muscle cells
7. Cardiac output (CO) = the amount of blood pumped by each ventricle in
one minute
a. Stroke volume (SV) = the amount of blod ejected from one ventricle with
1 heartbeat
b. SV X HR = CO
c. normal adult at rest CO = 5liter/minute
d. Factors affecting cardiac output:
-preload
-contractility
-afterload
Please refer to the readings for discussions of:
1.
2.
3.
4.
5.
Coronary Artery Disease and Acute Coronary Syndrome
Heart Failure
Hypertension
Vascular disorders
Dysrhythmias