ECG Lead System
Method for ECG Strip reading
1. Atrial and Ventricular Rhythm 2. Atrial and Ventricular rates 3. P-Waves 4. Intervals 5. QRS Complexes 6. ST Segment 7. T-Wave
Where should you put electrodes ?
1. Close to bone 2. Over soft tissue
Other Factors that affect QT interval
1. Ischemia 2. Hypothermia 3. Bradycardia 4. Neurological Imbalance 5. Electrolyte imbalances 6. Recent CVA
Antibiotics
1. Macrolides 2. Erthromycin and Biaxin 3. Fluoroquinolones
Where should you NOT put electrodes
1. Thick muscles 2. Skin Folds 3. Bony prominence's they can cause ECG artifacts that take away from the reading
Antidepressants
1. Tricyclics 2. Haldol 3. HIV protease inhibitors
Identify the three (3) statements that correlate with cardiac cells. A. The heart has pacer cells and myocardial cells. B. Myocardial cells generate and conduct electrical impulses. C. Myocardial cells receive the impulse and do the work. D. Pacer cells are part of the electrical conduction system.
ACD
When the parasympathetic nerve fibers are stimulated, what is released?
Acetylcholine
Six-Second Rule
All Rhythm Types -6 second strip -Total number of R (ventricular) wave or P waves (atrial rate) - x by 10 to find BPM
P-Wave
Atrial Depolarization in response to SA node triggering Atria are stimulated and contract, they push blood through tricuspid and mitral valve into the relaxed ventricles height: 2-3mm duration: 0.06-0.12 seconds
The ECG stylus produces an isoelectric line in response to what?
Balanced electrical force field
ST Segment
Beginning of ventricle repolarization, should be flat Total ventricular activity: complete time for ventricles to depolarize and repolarize duration is most critical: 0.36 to 0.44 seconds (half the distance between R-waves) duration varies with: HR, age, sex male: .39-.41 female: .36-.44
Knoched R Wave
Bundle branch block
Why is the QRS larger than the P wave?
C. Ventricular depolarization involves greater muscle mass than atrial depolarization.
What electrolyte is important in cardiac muscle contraction?
Calcium is much needed for muscle contraction
What if P-waves are absent?
Can indicate that the rhythm was generated somewhere beside the sinus node. Maybe the AV junction
Along with Lead II, lead III is most helpful in monitoring changes in what part of the heart?
Changes associated with inferior wall myocardial infarction
What allows the cardiac cells to transmit an electrical impulse?
Conductivity
PR Interval
Delay of AV node to allow filling of ventricle Atrial-ventricular conduction time. Path of electrical impulse through the AV node, bundle of HIS, right and left bundle branches, to the purkinje fibers PRI is measured from begnning of P wave to start of QRS Duration:0.12-.20 seconds
What does the P wave represent?
Depolarization of both right and left atria
QRS
Depolarization of ventricles, triggers , main pumping contractions represents ventricular depolarization, when ventricles contract, forcing blood out into the arteries Q- depolarization of interventricular septum R and S = depolarization of left and right ventricles duration: 0.04-0.10 seconds
ST segment
Early repolarization of right and left ventricles QRS and ST meet is j point should be flat at isoelectric line: Myocardial injury like acute ischemia
The ECG produces an upright pattern on the paper in response to what?
Electricity flowing from the heart towards a positive electrode
T or F? The QRS is smaller than the P wave.
F
What are ECG artifacts?
False cardiac waveforms
Shorter QT interval
Fast heart rate (heart doesnt have enough time to regroup)
Sequential Method
For regular rhythms only -Select P and R Waves that fall on dark line on ECG Strip -Mark next 6 consecutive dark lines with 300, 150, 100, 75, 60, 50 -If R and P Wave fall on line 100 then HR is 100 BPM
ECG Strips
Has a grid formed by vertical and horizontal lines -Vertical Lines: Waves Amp/Voltage, can be +/- -Horizontal Lines: time, 25mm/second every box = 0.04 seconds 5x5 = 1 square 1 second of time = 5 squares
Myocardial Infraction (MI)
Heart Attack -Have abnormal rhythms. -Death of cardiac muscle due to ischemia
When the sympathetic nerve fibers are stimulated, what is elevated?
Heart rate
What lead would be most helpful to assess bundle branch defects and confirm pacemaker wire placement?
Modified Chest Lead 1 (MCL1)
Inverted T-wave
Myocardial Ischemia
P-Wave disinformation
Notched, peaked or inverted: atrial enlargement associated with COPD, pulmonary emboli, valvular disease or CHF
The electrocardiogram (ECG) complex represents the electrical events occurring in _____.
One cardiac cycle
Doe the ECG machine monitor or control the hearts rhythm?
Only monitors
Cardiac cycle: ECG
P wave: atrial contraction QRS: ventricular contraction T: resting state
Sinus Rythum
P- atrial depolarization QRS-ventricular depolarization (.04-.10) PR Interval- atrial-ventricular conduction time (.12-.20 seconds) QT Interval- ventricular depolarization and repolarization ST Segment- isoeletric should be flat T-Wave- ventricular re-polarization
Which part of the waveform represents atrial depolarization?
P-wave
V1 shows
P-wave QRS complex ST segment
What interval measurement represents the complete refractory period?
PR Interval
Which part of the waveform represents atrioventricular conduction?
PR Interval
T or F? A waveform is movement away from the baseline in either positive or negative direction.
T
T or F? ECGs are used to monitor the effects of new medications.
T
T or F? The QRS complex in the modified chest lead 1 (MCL1) can be negative and still be normal.
T
T or F? To assure good contact, new electrode patches should be applied every 24 hours or whenever a patient bathes, or becomes clammy or sweaty.
T
T or F?The ECG monitor displays the conduction of the electrical impulses through the heart, NOT the actual contraction of the heart muscle.
T
In which part of the waveform does ventricular repolarization occur?
T wave
ECG Pattern
Upward Pattern: electricity flowing from the heart to the electrodes moving to the positive electrode Downward Pattern: electricity flowing from the heart to the electrodes moving away from the positive electrode
What affects preload?
Volume of blood in ventricles
12-Lead Testing System
Whole picture of heart 6 are chest 6 are limb
LL
aVF left leg: positive deflection positive deflection because the hearts electrical activity moves toward the lead
LA
aVL Left arm: positive deflection because the hearts electrical activity moves toward the lead
RA
aVR Right arm: negative deflection because the hearts electrical activity moves away from the lead
A Leads
aVR aVL aVF
How often should electrode location sites on inpatients be rotated? A. 2 hours B. 12 hours C. 24 hours D. 48 hours
every 24 hours
Lead 111
left arm (-) left leg (+) -also positive deflection -also detects changes associated with an inferior wall myocardial infraction
V4
placed at 5th intercostal space and midclavicular line
Leads
recordings of heart activity from several angles around the heart (like adjusting the view for your camera)
Lead 11
right arm (-) to below the last left palpable rib, below the midclavicular line(+) -primary lead -also positive deflection -current travels down and to the left following normal condition system of the heart -info about inferior portion of the heart -useful for detecting sinus node (SA) and atrial arrhythmias
Lead 1
right arm (-) to left arm (+) -positive deflection of ECG tracings -helpful in monitoring atrial rhythms and hemi blocks
Of the following locations, what is the best area to position electrodes?
soft tissue
T-wave
ventricular repolarization amplitude: 0.5mm leads 1,2,3
What interval represents total ventricular activity?
QT Interval
Which segment represents total ventricular activity?
QT Interval
QT correction formula
QTc= QT/ sqrt R-R
What is the first step in preparation of the patient for ECG monitoring?
Reassure patient and maintain privacy
Ectopic P waves may be upright or inverted and originate from somewhere other than the
SA Node
In which segment/interval does early repolarization of R/L ventricles occur?
ST Segment
R-R Interval
Same = Ventricular rhythm regular different = Ventricular rhythm irregular
P-P Interval
Same = atrial rhythm regular different = atrial rhythm irregular
Electrocardiogram (ECG)
Since you can't see the heart beating we use a ECG to provide a picture that replicates the actual cardiac issue.
Longer QT interval
Slower heart rate (heart is working to hard
V1
-corresponds to modified chest lead (MCL1) placed Right side of sternum, 4th intrcostal space -Distinguishes between right and left ventricular topic beats
What is the normal measurement for the QRS complex?
0.04 to 0.10 seconds
A PRI is considered short if it is less than ___ second and long if it is more than ___ second
0.12, 0.20
Atrial/Ventricular Rate 1500 Rule
-2 consecutive rates for P (atrial) rate -2 consecutive rates for R (Vent) rate -Count # of small boxes between them -Divide 1500 by total # of boxes
Atrial/Ventricular Rate 300 Rule
-2 consecutive rates for P (atrial) rate -2 consecutive rates for R (Vent) rate -Count # of sqaures between them -Divide 300 by this #
Caliper Measure for Atrial
-Lay strip flat on desk -Position Left caliper leg on 1st P wave and Right on second peak (P-P Interval) -turn caliper to next P wave, and continue down to make sure P-P wave line up
Caliper Measure for Atrial
-Lay strip flat on desk -Position Left caliper leg on 1st R wave and Right on second R peak (R-R Interval) -turn caliper to next R wave, and continue down to make sure R-R wave line up
V1 monitors:
-Ventricular arrhythmia -ST segment changes -Bundle branch blocks
antiarrhythmics
1. Amiodarone 2. Tikosyn 3. Pronestyl 4. Quinidine 5. Sotalol
Lead I is helpful for monitoring?
Hemi blocks
QRS > 0.10 seconds means
Intraventricular conduction delay
Straight line when machine is turned on but not connected to the patient
Isoelectric = no current It is straight because there is a balanced electrical force field. This Isoelectric line acts as a starting point for the patterns to be displayed
What do you look at for Inferior MI?
Lead 11
Which lead is helpful in monitoring atrial rhythms and hemiblocks?
Lead I
Which of the following leads would you use to monitor atrial rhythms and hemi blocks?
Lead I
Which lead is the most useful for routine monitoring and monitoring the sinus node?
Lead II
Which of the following leads would be helpful for detecting sinus node and atrial arrhythmias?
Lead II
Biphasic
Lead V1-3 with both positive and negative deflections
Modified Chest Lead (MCL1)
Left upper chest (-) to Right Side of the sternum @ 4th inter coastal space (+) and Ground on the right upper chest -Looks at the anterior wall of the heart -can be uses to access QRS complex arrhythmia -premature ventricular and supra ventricular beats -ventricular tachy -bundle branch defects -P-wave changes -Confirm pacemaker wire placement
What is the most common reason for the alarm to sound during an ECG procedure?
Loosening of a leadwire
What do you look at for Anterior MI?
MCL1 test lead
Deep, wide Q wave
MI
Which of the following cells are responsible for spontaneous generation and conduction of electrical impulses?
Pacer Cells
V5
Place at 5th intercostal space and anterior axillaryline positive deflection of ECG
V3
Placed between 2 and 4
V2
Placed left of sternum, 4th intercostal rib space
V6
Placed level with v4 and midaxillary line positive deflection
Tall P-Wave
Potassium abnormality
What is an important electrolyte that affects cardiac function?
Potassium and Calcium
What factors impact afterload? (select all that apply) A. Arterial contractility B. Pressure C. Resistance D. Volume
Pressure Resistance
Which part of the waveform represents ventricular depolarization?
QRS Complex
