Florida Heart CPR* s1

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Florida Heart CPR*

Telemetry

8 hours

Because of the length of this course it is recommended that the student print the course out. Then log back on to MEDCEU and take the accompanying test when finished studying the text.

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Have you ever had trouble identifying a rhythm or just wished you could recognize an EKG quickly and easily? After completing this course you will be able to rapidly identify most rhythms.

When we were initially trained in school to identify rhythms, we had to memorize what the rhythm
looked like to identify it. But the trick is to understand what is happening to the heart, more specifically theElectrophysiology of the heart. It is important to understand what's going on with the heart to interpret any rhythm. Understanding is the key to knowledge. Today we are going to learn how to understand and readEKG's. It's simple and easy. You just have to follow the 5 basic steps of rhythm recognition. If you apply these steps you will be able to identify most rhythmswith no tools or calipers, just your eyes and head.
The electrocardiogram (EKG) will be our main area of study today. We will coverseveral topics in this course including cardiac anatomy and physiology, electrodes, lead placement, measuring heart rates, and identifying EKG wave forms.

Note: Although we freely use the term EKG as an abbreviation for electrocardiogram, the abbreviation ECG is the proper term but is easily confused with electroencephalograph (EEC).

Anatomy and Physiology

Heart Chambers

The heart is a four chambered structure made up of two receiving chambers called atria
and two pumping chambers called ventricles. The right atrium receives oxygen poor
blood returning from the body through the superior and inferiorvena cava. The right
ventricle pushes the oxygen poor blood to the lungs through the pulmonary arteries.
The left atriumreceives oxygen rich blood returning from the lungs through pulmonary veins.
The left ventricle pushes the oxygen richblood out through the aorta, which directs the
blood to all parts of the body. The right and left atria are separated by the
interatrial septum while the right and left ventricles are separated by the interventricular septum.

Heart Valves

When blood flows through the heart it follows a unidirectional pattern. It first enters both atria
and then fills both ventriclesbefore leaving the heart. In order to prevent backflow
against this pattern there are four valves in the heart that serve this function.
Found between the atria and ventricles are two atrioventricular (A-V) valves
that prevent blood from reentering the atria. The valve that guards the right
atrium is called the tricuspid valve while the valve guarding the left atrium
is called the bicuspidor mitral valve.

The two remaining valves are called semilunar valves. The valve located where the
pulmonary trunk meets the right ventricleis called the pulmonary semilunar valve.
The valve found where the aorta and left ventricle meet is called the aortic semilunar
valve. Both semilunar valves prevent backflow of blood into the ventricles.

Heart Muscle (Myocardium)

The heart is a specialized structure, which is made of muscle that has unique characteristics.
The cell membranes of myocardial cells form very close connections to each other.
These connections are called intercalated disks and allow groups of muscle
cells to function as one. This unique contractile ability of myocardium is known
as a syncytium. The muscle cells that make upthe atria and ventricles act as two separate
syncytia, therefore contracting as two single units.

Cardiac muscle has the ability to adapt to the amount of blood being delivered to it. There is
a direct proportion betweenthe amount of blood returning to the heart and the force of
cardiac muscle contraction. The more blood returning through the veins, the stronger
the muscular contraction ejecting blood out of the heart into the arteries. This occurs
due to the heartmuscle responding to a stretch in the chamber walls as a result of an
increased amount of blood volume entering the heart.The ability of the heart to be able
to equalize the amount of blood entering and exiting it is called Frank-Starling’s law of the heart.

Compared to skeletal muscle, heart muscle cells have a longer rest or refractory period.
This allows the myocardium to relax aftereach contraction preventing a tetanic contraction
of the heart. It also gives the heart chambers time to fill with blood before the next
contraction.

Unlike skeletal muscle, which needs nerve innervation for stimulation, cardiac muscle
needs no outside stimulus.This is what is known as automaticity. Heart muscle also
possesses inherent rhythm, which means it will contract at a regular rate.

Conduction System

The conduction system of the heart explains how heart muscle has automaticity
and is able to contract without the help ofoutside nervous or hormonal innervation.
It is made up of specialized cardiac cells that initiate and guide myocardial
contraction. The conduction system consists of the sinoatrial node (S-A node),
atrioventricular node (A-V node),atrioventricular bundle (A-V bundle or A-V bundle of His),
Purkinje fibers and bundle branches.

The S-A node is located in the posterior wall of the right atrium. It sets off impulses
that trigger atrial contraction. It discharges impulses quicker than any other part of
the heart and establishes the rate and rhythm for the entire
heart. Because of this it is more commonly known as the pacemaker.
Note: A node is the same thing as a pacer or pacemaker.

The contracted atrial cells then send the impulse to the A-V node, which is located in the
atrial wall near the interatrialseptum. Once the A-V node picks up the signal, the speed
of impulse transmission is slowed down to allow the atria
time to complete contraction before ventricular contraction occurs.

From the A-V node the impulse then travels to the A-V bundle (bundle of His)
which is made up of special fibers calledPurkinje fibers. The A-V bundle begins
at the right side of the interatrial septum and runs down to the beginning of the
interventricular septum. It then branches into right and left bundle branches
that run down the length of the interventricularseptum. The bundle branches further
divide into Purkinje fibers that cover the inner surface of the ventricles. The impulses
relayed from the Purkinje fibers initiates ventricular contraction.

The Electrocardiogram

The EKG is a recording of the electrical impulses produced by the heart.
The body acts as a giantconductor of electrical currents. Any two points on the body may be
connected by electrical leads (electrodes) to register an EKGor to monitor the rhythm of the heart.
The tracing recorded from the electrical activity of the heart forms a series of waves and
complexes that have been arbitrarily labeled (in alphabetical order) the P, Q, R, S, T waves,
and sometimes the U wave.The waves or deflections are separated in most patients by regularly occurring intervals.

Depolarization (electrical firing) of the atria produces the P wave. Depolarization of the ventricles produces the QRS complex .
Repolarization (electrical recharging) of the ventricles causes the T wave. The significance of the U wave is uncertain, but it may be
due to repolarization of the Purkinje system.

The key to rhythm interpretation is the analysis of the form and interrelations of the P wave, the PR interval,
and the QRS complex. The EKG should be analyzed with respect to its rate, its rhythm, the site of the
dominant pacemaker, and the configuration of the P and QRS waves.

P Wave:.
The P wave is generated by the Sinoatrial(SA) Node or sinus node. Once the SA node fires the electricity goes though both atria and a P wave is then
present on the monitor. That's why we call it a sinus rhythm. OK let me put it like this; if the rhythm has one P wave for every QRS complex
and is under 150 BPM, then we call it a sinus rhythm because it is generated by the Sinus node (SA node).
If the rhythm has more than one P wave for each QRS we call it an Atrial rhythm.If for some reason the sinus (SA) node fails to act as the normal cardiac pacemaker, other atrial foci may take over,and the P wave may have a different configuration. Alternatively, a secondary pacemaker (eg, the AV junction)
may provide an "escape rhythm."

Top of Form

Bottom of Form

PR Interval: When conduction through the atria, the AV node, or bundle of His is slowed, the PR interval
becomes longer. Changes in conduction through the AV node are the most common cause of changes in the PR interval.
The P to R interval is important in identification of heart blocks. We'll cover some of that later on.
The PR interval extends from the beginning of the P wave (the beginning of atrial depolarization) to the onset of the
QRS complex (the beginning of ventricular depolarization). It should not exceed 0.20 seconds as measured on
EKG graph paper, where each small square represents 0.04 seconds.

QRS Complex. The QRS complex represents the electrical
depolarization of the ventricles. The upper limit of normal duration of the QRS complex is less than 0.12 seconds. A QRS
complex duration of less than 0.12 seconds means that the impulse was initiated from the AV node or above (supraventricular).
A wide QRS complex (more than 0.12 seconds) may signify conduction that either arises from the ventricle or comes from
supraventricular tissue. Prolonged conduction through the ventricles produces a widened QRS complex.
If there is a delay or interruption in conduction in either bundle branch, the QRS will widen in a
manner typical for either right or left bundle branch block. An ectopic focus that initiates an impulse from the
ventricle also can alter the shape of the QRS. When an ectopic beat arises above the bundle branches, the
ventricles are activated in a normal fashion and the QRS complex will remain the same, assuming that there is no
conduction delay in either bundle branch. If the depolarization occurs below the bundle branches, the QRS complex
will be widened and notched or slurred because a different sequence of conduction will ensue.
A wide QRS complex with no P waves is usually a ventricular rhythm.
Lead Placement

There are many types of cardiac monitoring systems, but they generally consist of a monitor screen
(cathode ray oscilloscope) on which the EKG is displayed and a write-out system that directly transcribesthe rhythm strip onto paper. The write-out may be automatic or controlled by a switch, and a ratemeter may be set to write out a rhythm strip if the rate goes below a preset figure (eg, 50 beats per minute) or above a certain rate (eg, 120 beats per minute) for at least 6 seconds, and sometimes for as long as 30 seconds.

A ratemeter triggered by the QRS complex of the EKG is usually part of the system. Lights and beepers may provide visual and audible signals of the heart rate.
Monitor leads or electrodes may be attached to the patient's chest or extremities. The chest leads must be placed toshow clearly the waves and complexes of the EKG strip.
Conventional locations for the chest electrodes are illustrated below. The arrow indicates the direction of polarity from negative to positive. In lead I the positive electrode is below the left clavicle and the negative below the right.
Lead I

In lead II the positive
electrode is below the left pectoral muscle and the negative below the right clavicle .
Lead II

Lead III is displayed by attaching the positive electrode beneath
the left pectoral muscle and the negative below the left clavicle. Although these simulate or approximate the I, II, and III leads
of the standard EKG, they are not identical.
Lead III
Another popular monitoring lead is the MCL1 lead. To connect this lead, the negative electrode is placed near the left shoulder,
usually under the outer third of the left clavicle, and the positive is placed to the right of the sternum in the fourth intercostal space.
Lead MCL1

The ground electrode in all four leads can usually be placed almost anywhere but is commonly located below the rightpectoral muscle or under the left clavicle. The electrodes are often color-coded for ease of application, lessening confusion in location.

The negative lead is usually white, the positive lead is red, and the ground lead is black, green, or brown. The popular phrase "white-to-right, red-to-ribs, and black left over" helps to recall where the leads for lead II should be placed.
Remember the following points when monitoring patients:
1. A prominent P wave should be displayed if organized atrial activity is present. Leads that show the P wave clearly should be chosen.
2. The QRS amplitude should be sufficient to properly trigger the ratemeter.
3. The patient's pericardium must be kept exposed so that defibrillation paddles can be readily used if necessary.
4. Monitoring is for rhythm interpretation only. One should not try to read ST abnormalities or attempt more elaborate EKG interpretation.
5. Artifacts should be noted: a straight line will show if the electrode is loose, or a bizarre, wavy baseline resembling ventricular fibrillation (VF) may appear if an electrode is loose or the patient moves. Sixty-cycle interference also may be present.

Always remember that any EKG findings should be correlated with clinical observations of the patient.
Different electrode placements may be used for telemetry or other special purposes. The positive electrode should be to the left or below the negative electrode. Otherwise the deflections will all be reversed and the rhythm strips can be confusing.

How To Identify an EKG

Alright, lets get down to it. In order to identify rhythms, we need to follow the 5 basic steps
of rhythm recognition.
1. Rate (Calculate the heart rate)
2. Rhythm (Measure the regularity or rhythm of the R waves)
3. P-wave (Examine the P-wave)
4. P to R interval ( Measure the P to R interval)
5. QRS (Measure the duration of the QRS complex)