Cardiac ECG
 

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The arteries are the exclusive suppliers of arterial blood to the heart muscle, delivering about 250 mL per minute.  The coronary artery carries about 85% of the blood supply to the myocardium.  The right coronary artery accounts for the remaining 15%.  The coronary arteries originate just past the aortic valve.  The coronary arteries receive blood during the phase of left ventricle activity.  The coronary arteries run along the epicardium surface then divide into smaller vessels as they penetrate the myocardium and endocardium.  The left main coronary artery subdivides into the descending and arteries.  The descending supplies the anterior heart on the left side. The circumflex feeds the lateral and portion of the left side and part of the right ventricle.  The right coronary artery feeds the atrium, and right ventricle.  The coronary blood leaves the heart by being dumped into the right atrium via the coronary sinus.

The heart is a pump system.  Low pressure right side know as the loop and high pressure left side know as the loop.   The function as a "primer pump" to fill the ventricles to the fullest.  This is know as Dr. Frank Starling's.  Dr. Frank Starling's said the more you stretch the ventricles the more the .  This is why when we give a fluid bolus to a cardiac patient. We are not trying to "fill them up with fluid" but rather stretch the ventricles to increase .  Simply put the myocardial fibers contract more forcefully when stretched resulting in an increase in stroke volume which increases pre-load.

The heart at work is referred to as  phase and the heart at rest is the phase.  Blood moves from areas of high pressure to pressure. 

The heart has valves which prevent back flow.  The ones located between the atria and ventricles are termed valves.  The left atrioventricular valve is the also know as the mitral valve.  The right atrioventricular valve is the .  The valves leaving the ventricles are termed valves.  The one leaving the left ventricle is the valve and the right ventricle is the valve. 

is the amount of blood ejected from each ventricle during one contraction.  is the amount of blood returning to each ventricle.   is a result of peripheral vascular resistance which is the total resistance against which blood must be pumped.  A decrease in vascular resistance allows for stroke volume.  An increase in vascular resistance allows for a lower stroke volume.  is the amount of blood pumped by the ventricles per minute.  Cardiac output can be increased by increasing the heart rate and/or stroke volume. 

Nervous system control of the heart.  The parasympathetic and sympathetic autonomic nervous system is a major factor influencing the heart rate, conductivity, and contractibility.  The atria are well supplied with both sympathetic and parasympathetic nerve fibers but the ventricles are mainly supplied by the   nerves.  So lets say you have a complete heart block.  This is when the atrial and ventricle conduction is blocked.  If the heart rate is slow atropine is generally indicated to block the tone.  Since there is a heart block the atropine will primarily work on the atria but not the ventricles. This is why pacing is preferred for high degree heart blocks since pacing can directly control the ventricles.  The nerve stimulates the vegetative state.  Thoracic ganglia release which increase beta affects - chronotropic which is and inotropic which is contraction. 

Electrolytes play a major part of cardiac function; , , and .  Magnesium is a major intracellular cation which helps stabilize the cell membranes.. 

The two basic cells within the myocardium are and .  Electrical cells make up the system and conduct electrical impulses.  The mechanical cells are movement cells which move the heart and create a pulse or blood pressure.

The sodium - potassium pump is an example of active transport.  The state is when sodium is outside the cell and potassium is inside.  When action potential is established potassium moves outside the cell and fast sodium channels and slow calcium channels move into the cell resulting in  of the cell(s).  When the potassium reenters the cell this is called the state.  Once this cycle is complete we are back to the ready state.  This is why calcium channel blockers like verapamil and diltiazem help to control rate. 

Nerve and muscle cells in the heart have the ability of producing action potentials known as excitability.  If the action potential is high enough a current will be produced.

During the depolarization phase all cells go through an "all or none" principle.  The   refractory period is the period of time when the cell has not recharged enough to discharge again.  The   refractory period is when enough of the cells have recharged to reach potential action but not all cells. 

Question 1) Letter A in the diagram indicates:
Question 2) Letter B in the diagram indicates:
Question 3) If a stimulus to contract is delivered during letter B phase will cells be stimulated?
Question 4) If a stimulus to contract is delivered during letter A phase will cells be stimulated?

Electrical Conduction System of the Heart.  The SA and AV nodes are located in the   atrium.  The Bundle of His is the potion of the AV node which descends to the ventricles and branches into the left and right branches.  Smaller branches of the bundles are Purkinje fibers which contact the myocardial fibers through which electrical impulses spread from cell to cell resulting in contraction. 

A pacemaker node or cell(s) reaction to hormonal changes or stimulus which are the SA and AV nodes.  When an electrical impulse spontaneously occurs this is know as .  The intrinsic rate is a back up system of the heart.  The SA node fires to 100 times a minute.  When the SA node escapes the AV node takes over at to 60 beats per minute.  If the AV node fails the Purkinje fibers fire at to 40 beats a minute. 

Ectopic beats are ones that do not originate from within the node.  If a stimulus to beat occurs that interrupts the normal SA node rate it is termed a premature beat.  If the premature beat becomes the pacemaker it is the ectopic focus. Reentry is reactivation of myocardial tissue from the same impulse numerous times as seen in V-tach, SVT, a-fib, a-flutter.

Electrocardiogram (ECG) is a graphic representation of the heart's electrical activity.  ECG leads are

bulletBipolar leads have one positive and the other - examples are leads I, II, III or limb leads. 
  1. Lead one is from left to right arm.  Left arm is positive.
  2. Lead two is from right to left leg.  Left leg is positive.
  3. Lead three is from left to left arm.  Left leg is positive.
bulletUnipolar leads make up augmented limb leads - aVr, aVl, aVf. 
  1. Reference point from the center of the heart.
  2. Helpful in determining axis.
bulletPrecordial leads are V1 through V6. 
  1. Specific areas of the heart.
  2. V1, V2 are septal
  3. V2, V3, V4 are anterior
  4. V5, V6 anterior
  5. V4 left ventricle

12 lead placement

bulletV1, V2 at   intercostal
bulletV4 5th intercostal
bulletV3 between V2 and V4
bulletV6 level with V4 or V5.
bulletV5 between V4 and V6
bulletIf using alligator clips place electrode facing down.
bulletIf doing a 12 lead keep electrodes on so hospital staff has a reference point.
bulletRemember that a 12 lead only uses electrodes.

Application of electrodes.  Use alcohol prep to remove dirt and oil.  Use location without large muscles, lots of hair, and bone.  Use conduction gel.

ECG graph paper.

bullet lines measure time in seconds.
bullet lines measure voltage/amplitude.
bullet1 small box is sec (at standard recording speed of 25mm per second.)
bullet5 small boxes is seconds. 
bullet5 big boxes is second.
bullet1 little box in height is 1 mm.

Standard waves in one cardiac complex.

bullet"P" represents the atria
bullet"QRS" represents the depolarizing. Measure less than 0.12 sec.
bullet"T" represents the of ventricles.
bullet"PR Interval" is the amount of time from start of atrial depolarization "P"  to start of ventricle depolarization "QRS".  Should measure 0.12 to sec.
bullet"ST" segment is from the end of the "QRS" to the start of the "T" wave.
bullet"QT" segment from start of "QRS" until end of "T" wave. 
bulletSegments are two waves.
bulletInterval is from the of one wave to the start of another.
bulletIsoelectric line is a period of electrical activity.
bulletUp slope of "T" is termed refractory period
bulletDown slope of "T" is termed refractory period or R on T phenomenon

Artifact

bulletImproper grounding of machine.
bulletPatient
bulletLoss of electrode contact
bulletShivering or
bulletCPR
bullet cycle interference from motors.
bulletBiotelemetry like low batteries on holster monitor.

Heart Rate Calculator Rule

bulletSix Second Method
  1. Used on irregular and regular rhythms
  2. Ventricular rate - take the number or QRS complexes in a six second ECG strip and multiply by 10.
  3. Atria rate - take the number of P waves in a six second strip and multiply by 10.
  4. This method is an approximation.
bulletTriplicate Method
  1. A must for medics to memorize.
  2. Take the number of large boxes between two consecutive R to R waves or P to P waves.  Divide the number of large boxes into 300.
  3. This method is only recommended for regular rhythms.
  4. 300, , 100, , 60,

bulletMost accurate method
  1. For regular rhythms
  2. Take the number of small boxes between two consecutive R to R waves or P to P waves and divide  into 1500.

5 step analysis

bulletStep one REGULARITY
  1. Is the rhythm regular, irregular or irregularly irregular.
bulletStep two RATE
  1. Establish the underlying rate.
  2. Get both the atria and ventricular rates.
  3. Six second method, triplicate method or most accurate method.
bulletStep three P WAVE
  1. Is the P upright/
  2. Are all the P waves uniform.
  3. Is there one P for every QRS complex?
bulletStep four PR Interval
  1. Is the PR Interval constant or changes?
  2. Is the PR Interval measurement at 0.12 and no longer than sec.
bulletStep five QRS COMPLEX
  1. Does the QRS complex change?
  2. Is there one QRS for every P wave?
  3. Is the QRS measurement less than sec for adults and 0.08 for pediatrics?

Classification of ECG Rhythms

bulletSinus (originates from the node)
  1. Normal Sinus Rhythm
  2. Sinus Bradycardia
  3. Sinus Tachycardia
  4. Sinus Arrhythmia
bulletAtrial Rhythms (originate from the atria but outside the node)
  1. Wandering Pace Maker
  2. Atrial Flutter
  3. Atrial Fibrillation
  4. Atrial Tachycardia
  5. SVT
  6. "Stepchild" is a PAC
bulletJunctional Rhythms (originate in the node)
  1. Escaped Junctional Rhythm
  2. Accelerated Junctional
  3. Junctional Tachycardia
  4. "Stepchild" is a PJC
bulletVentricular (Wide QRS - originates in the ventricles)
  1. Idioventricular
  2. V-Tach (monomorphic and polymorphic)
  3. V-Fib
  4. Asystole
  5. "Stepchild" is a PVC
bulletHeart Blocks
  1. 1 degree heart block
  2. 2nd degree type 1
  3. 2nd degree type 2
  4. 3rd degree

_____________________________________________________

Label the heart:
A green) B green) A black) B black)
C) D)   E) F) 1)
2) 3) 4) 5) 6)

________________________________________________________

The letter A represents how much time in seconds?
The letter B represents how much time in seconds?
For the following colors calculate the time in seconds?
The Brown line in seconds?    
The Blue line in seconds?       
The Green line in seconds?    
The Red line in seconds?       
The Pink line in seconds?      
Using the triplicate method of calculating rate (large boxes into 300) what is the rate for:
The Brown line?    
The Blue line?       
The Green line?    
The Red line?       
The Pink line?      
Using the most accurate method to calculate rate (divide small boxes into 1500) what is the rate for:
The Brown line?   
The Blue line?       
The Green line?   
The Red line?       
The Pink line?    

________________________________________________________

Using box 1: Black square numbered 1 is the?
Using box 1: Blue square numbered 2 is the?
Using box 1: Yellow square numbered 3 is the?
Using box 1: The green gap numbered 4 is the?
Using box 1: The red gap numbered 5 is the?
Using box 1: The white box numbered 6 is termed the?
Using box 2: The red rectangle represents the?
Using box 2: The blue rectangle represents the?
Using box 3: What is missing in the Black Circles?
Using box 3: Is the rhythm regular or irregular? 

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The P waves, which are circled RED, are they the same or different?
Is the rhythm regular or irregular? 
Using the QRS, which tip is circle in orange, what is the rate if it falls on the green line using the triplicate method?
Using the QRS, which tip is circle in orange, what is the rate if it falls on the red line using the triplicate method?
Using the QRS, which tip is circle in orange, what is the rate if it falls on the blue line using the triplicate method?
Using the QRS, which tip is circle in orange, what is the rate if it falls on the black line using the triplicate method?
Using the QRS, which tip is circle in orange, what is the rate if it falls on the pink line using the triplicate method?

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Premature beats are ectopic beats.  To be a premature beat it must come before the next expected normal beat.  In the square boxes are premature beats.  There are three premature beats which are PVC, PAC, PJC. The key difference is the origin of the beat. If there is an upright P wave it is a PAC.  If the P wave is absent or inverted and the QRS is narrow is it a PJC.  If the QRS is wide it is a PVC. The circle is the area to focus on to determine which  premature beat it is.

Is the premature beat a:
Is the rhythm regular or irregular?  (You do not count the premature beat complex)
What is the rate if it falls on the green line using the triplicate method?
What is the rate if it falls on the pink line using the triplicate method?
What is the rate if it falls on the blue line using the triplicate method?
What is the rate if it falls on the yellow line using the triplicate method?

________________________________________________________

Premature beats are ectopic beats.  To be a premature beat it must come before the next expected normal beat.  In the square boxes are premature beats.  There are three premature beats which are PVC, PAC, PJC. The key difference is the origin of the beat. If there is an upright P wave it is a PAC.  If the P wave is absent or inverted and the QRS is narrow is it a PJC.  If the QRS is wide it is a PVC. The circle is the area to focus on to determine which  premature beat it is.

Is the premature beat a:
Is the rhythm regular or irregular?  (You do not count the premature beat complex)
What is the rate if it falls on the green line using the triplicate method?
What is the rate if it falls on the red line using the triplicate method?
What is the rate if it falls on the blue line using the triplicate method?
What is the rate if it falls on the pink line using the triplicate method?

________________________________________________________

Premature beats are ectopic beats.  To be a premature beat it must come before the next expected normal beat.  In the square boxes are premature beats.  There are three premature beats which are PVC, PAC, PJC. The key difference is the origin of the beat. If there is an upright P wave it is a PAC.  If the P wave is absent or inverted and the QRS is narrow is it a PJC.  If the QRS is wide it is a PVC. The circle is the area to focus on to determine which  premature beat it is.

Is the premature beat a:
Is the rhythm regular or irregular?  (You do not count the premature beat complex)
What is the rate if it falls on the black line using the triplicate method?
What is the rate if it falls on the red line using the triplicate method?
What is the rate if it falls on the blue line using the triplicate method?
What is the rate if it falls on the yellow line using the triplicate method?

________________________________________________________

Using the ECG strip labeled box 4 is considered trigeminy or bigeminy?
Using the ECG strip labeled box 5 is considered trigeminy or bigeminy?

The green circles are normal beat and the red squares are ectopic beats.

________________________________________________________

Is the QRS complete narrow or wide?
Is the rhythm regular or irregular?
What method must be used to calculate the rate?
Does every P wave have a QRS?
Does every QRS have a P wave?
Does the PR Interval stay the same measurement?

________________________________________________________

Using the ECG below answer the following questions:
Is the rhythm regular or irregular? 
Describe the P wave?
What is the PR Interval measurement?
What is the QRS measurement?
Is there one P wave for every QRS?
Is there one QRS for every P wave?
Is the T wave upright or inverted?
Using the 6 sec strip method to calculate rate what is the ventricular rate?
Using the most accurate way to calculate rate (little boxes divided into 1500) what is the atrial rate?
Using the most accurate way to calculate rate (little boxes divided into 1500) what is the ventricular rate?

 


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