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EKG

Kevin's EKG Interpretation Lecture (SIUE Nurse Anesthesia)

QuestionAnswer
Name the six limb leads. I, II, II, aVF, aVL, aVR
Name the six precordial leads v1 – v6
Name the 3 pathways that carry impulses from the SA node to the AV node. Anterior Intranodal Pathway Middle Intranodal Pathway Posterior Intranodal Pathway
Does the Bachmann bundle carry impulses from the SA node to the AV node? No. Bachmann's bundle carries impulses from the SA node to the left atrium so that rt and lt atria contract at the same time.
Which ion is responsible for slowing of conduction in the AV node? Ca2+
Why is it important for the conduction to be slowed in the AV node? So that the atria have time to contract and squeeze all of their contents into the ventricles.
What is another name for the AV bundle? Bundle of His
Are AV node and AV bundle synonymous? No
Where is the SA node located? upper-posterior wall of RA
Which wave on the EKG is produced by the SA node? P wave
True/False. Contraction of the atria produces the P wave on an EKG. False. It is depolarization of the SA node.
How do the AV valves contribute to the electrical activity of the heart? They insulate the AV node so that the impulse can only travel down the AV node to the septal wall.
In which direction does the depolarization of the septum occur? Left to right
Which BB produces terminal filaments in the septum? LBB
What structures make up the ventricular conduction system? Purkinje fibers
How do Purkinje fibers conduct impulses so fast? Fast-moving sodium ions
True/False. Impulse from the AV node creates the QRS complex on the EKG. False. The contraction of the ventricles creates the QRS complex.
Blockage of the anterior or posterior fascicle of the LBB is called what? hemiblock
What is the term for the SA node preventing the lower structures of the pacemaker system from firing? Overdrive suppression
SA Node 60-100 BPM
Atrial Cells 55-60 BPM
AV Node 40-60 BPM
His Bundle 40-45 BPM
Bundle Branches 40-45 BPM
Purkinje Fibers 35-40 BPM
Ventricular Cells 30-35 BPM
What does the PR interval represent? Represents the time between the beginning of atrial contraction and the beginning of ventricular contraction
Does the atrial contraction last longer than the p wave? Yes
What does the P wave represent? atrial depolarization and contraction
What does the QRS complex represent? ventricular depolarization and contraction
Where does the ventricular contraction start on the QRS complex? beginning of the Q wave
Where does the ventricular contraction end on the QRS complex? end of the T wave
What does the ST segment represent? represents plateau phase of ventricular repolarization
What does the T wave represent? rapid phase of ventricular repolarization
How does repolarization of ventricular myocytes occur? Potassium ions leaving myocytes
When does repolarization of ventricular myocytes occur? immediately after S wave to end of T wave
What does the QT interval represent? ventricular contraction (depolarization and repolarization)
What is the QT interval a good indicator of? repolarization
What is a good indication of a normal QT interval besides the QTc? If it is less than half the R to R interval
What do the y and x axis of a small square on EKG represent? y axis = .1 mV x axis = .04 sec
What do the y and x axis on a large square on EKG represent? y axis = .5 mV x axis = .2 sec
On an EKG if an impulse is traveling toward a positive electrode, what direction will the deflection be? positive
On an EKG if an impulse is traveling away from a positive electrode, what direction will the deflection be? negative
Name the bipolar leads. I, II, III
Name the unipolar leads. aVR, aVL, aVF, v1-v6
What direction are leads I, II, III? lead I = +0 degrees lead II = +60 degrees lead III = +120 degrees
Where do all of the bipolar lead cross? AV node
For augmented leads, which leads serve as the negative lead (common ground)? The other two leads.
What direction are leads aVF, aVR, aVL? lead aVF = +90 degrees lead aVR = -150 degrees lead aVL = -30 degrees
What is the range for normal axis? +90 degrees to -30 degrees
What is the range for left axis deviation? -30 degrees to 180 degrees
What is the range for right axis deviation? +90 degrees to 180 degrees
For the chest leads, what serves as the positive leads and what serves as the negative leads? chest leads serve as positive leads heart serves as theoretical negative lead
What part of the hear do leads v1 and v2 look at? right ventricle
What part of the hear do leads v3 and v4 look at? septum
What part of the hear do leads v5 and v6 look at? left ventricle
What is the landmark for v2? 4th intercostal space, just lateral to sternum
What is the landmark for v4? 5th intercostal space, mid-clavicular line
What is the landmark for v6? directly lateral to v4 at mid-axillary line
What direction is the defection for v1 and v6? v1 = negative v6 = positive
What plane do the precordial leads measure? horizontal
What plane do the limb leads measure? frontal
List the 5 steps to EKG interpretation. 1) RATE 2) Rhythm 3) Axis 4) Hypertrophy 5) Infarction
How do you check rhythm? Identify the basic rhythm, then scan tracing for prematurity, pauses, irregularity, and abnormal waves
Steps for checking rhythm. Check for: Regularity Check for: P before each QRS Check for: QRS after each P (2 or 3° AV block) Check: PR intervals (for AV Blocks)(<0.2) Check: QRS interval (for Bundle Branch Block)(>0.12)
Name 4 basic types of arrhythmias. Irregular rhythms Escape Premature beats Tachy-arrhythmias
Name 4 types of irregular rhythms. Sinus Arrhythmia Wandering Pacemaker Multifocal Atrial Tachycardia Atrial Fibrillation
What is an escape rhythm? Escape Rhythm – an automaticity focus escapes overdrive suppression to pace at its inherent rate: 1) Atrial Escape Rhythm 2) Junctional Escape Rhythm 3) Ventricular Escape Rhythm
What is a premature beat? an irritable focus spontaneously fires a single stimulus 1) Premature Atrial Beat 2) Premature Junctional Beat 3) Premature Ventricular Contraction (PVC)
Name 4 basic types of blocks. Sinus Block AV Block Bundle Branch Block Hemiblock
What is a BBB and how is it identified on EKG? With BBB, one ventricle depolarizes slightly later than the other Will have 2 QRS complexes superimposed on each other. overall QRS will be wider & will have two peaks
What are 3 characteristics of a BBB? 1) Widened QRS (Greater than 3 small squares or 0.12 sec) 2) Look for two R-waves (R and R’) 3) Look for wide S
How do you tell a RBBB from a LBBB? If there is a R,R’ in V1/V2 there is probably a RBBB If there is a R,R’ in V5/V6 there is probably a LBBB RBBB will have a slurred S wave in v5 & v6 LBBB will have a deep, wide rS pattern in in v1 & v2 LBBB no petite Q wave in lat. leads.
Can the mean axis be determines in a BBB? No.
Can ventricular hypertrophy be determined accurately in the presence of a BBB? No.
How is an anterior hemlock identified on EKG? Axis shifts leftward > L.A.D. Look for Q1S3 normal or slightly widened QRS
How is a posterior hemlock identified on EKG? Axis shifts rightward > R.A.D. Look for S1Q3 normal or slightly widened QRS
What causes a hemiblock? Commonly due to loss of blood supply to the anterior or posterior division of the left bundle branch.
What causes an anterior hemiblock? Often associated with anterior infarction Results from occlusion of supply through branches of LAD
What causes a posterior hemiblock? Rare d/t collateral circulation Results from occlusion of supply through branches of RCA LCA LAD
Name the two bifasicular blocks. RBBB + Anterior Hemiblock RBBB + Posterior Hemiblock
Is an anterior and posterior hemiblock a bifasicular block? No. Just a LBBB.
What is a LBBB and a RBBB? complete AV block.
Name 4 reasons for axis deviation. 1) Change of the position of the heart in the chest 2) Hypertrophy of one ventricle 3) Myocardial infarction 4) Bundle branch block
1) Change of the position of the heart in the chest Obesity results in increased intrabdominal pressure which places a horizontal displacement on the heart A tall slender pt may have a more vertical displacement
2) Hypertrophy of one ventricle Axis deviates towards the hypertrophied muscle
3) Myocardial infarction Axis deviated away from the damaged muscle
4) Bundle branch block Axis unreliable
Which two leads are used to determine axis? Leads I and aVF
What are the 3 steps to determine axis? Locate the mean QRS vector in an axis quadrant (as previously discussed) Find the isoelectric lead Equal magnitudes of upward/downward deflection Move 90° away from the isoelectric lead into the predetermined quadrant (step 1)
lead I positive and lead aVF negative is? LAD
lead I negative and lead aVF negative is? EAD
lead I negative and lead aVF positive is? RAD
lead I positive and lead aVF positive is? normal axis
Which chest lead is best for determining an anterior or posterior infarction? v2
Which chest leads are usually isoelectric? v3 & v4
What are the 3 steps for assessing hypertrophy on EKG? Examine p-wave for Atrial Hypertrophy Examine R-wave for Right Ventricular Hypertrophy Examine S-wave depth in V1 and R-wave height in V5 for Left Ventricular Hypertrophy
What are the characteristics of RAH? Large, diphasic (both positive and negative) p-wave with tall initial component Seen in lead V1 Suspect if p-wave >2.5mm in any lead
What are the characteristics of LAH? Large humped p-wave in I, II, III; p > 0.12 w/ 0.04 between humps. or diphasic (positive and negative) in lead V1 with terminal portion > than initial portion. Seen with mitral valve stenosis and systemic htn
What are the characteristics of RVH? S wave persists in V5-V6 RAD with slightly widened QRS R wave gets progressively smaller from V1-V6 R > S wave in V1
What are the characteristics of LVH? Very deep S-wave in V1 & v2 Large R in V5 & v6 LAD or mm of S wave in v1 + mm of R wave in v5 = 35 mm or more
Why do arrhythmias occur with infarction? Ventricular foci in the hypoxic area around the infarct become very irritable
What type of MI occurs with occlusion of the left anterior descending artery? anterior infarction
What type of MI occurs with occlusion of the circumflex artery? lateral infarction
What type of MI occurs with occlusion of the right coronary artery? posterior. also supplies the SA, AV nodes and Bundle of His. (associated with serious arrhythmias.
What are the characteristics of ischemia? Characterized by transient inverted t-waves 1) Usually symmetrically inverted 2) Inverted t-waves are most pronounced in the chest leads 3) Inverted t-waves in V2-V6 always pathological 4) Inverted t-waves in V2-V3 alert us to stenosis of LAD
What are the characteristics of acute infarct? ST segment elevation Elevation of > 1mm above the baseline
What must be done for ST elevation without Q waves? Rule out infarction
What does ST depression represent? subendocardial infarction angina digitalis
What does a large Q wave mean? necrosis
What are the characteristics of a significant Q wave? One mm wide (0.04 sec in duration/one small box) or 1/3 the amplitude (or more) of the QRS *Omit lead AVR when looking for significant Q’s
What are the steps for assessing for infarction on EKG? Q waves Inverted T waves ST segment elevation or depression Find the location of the pathology and then identify the occluded coronary artery
Left anterior descending artery V1, V2, V3, V4
What leads show infarction of Left circumflex artery? I, aVL, V5, V6
What leads show infarction of Right or left coronary artery? II, III, aVF
What leads show infarction of Right coronary artery? V1, V2
Where does the base of the LV receive its blood supply from? The base of the LV receives its blood supply from branches of the dominant coronary artery Right coronary artery most common Left coronary artery less common
When is the EKG diagnosis of an infarction not valid? in presence of LBBB.
What are the characteristics of COPD on EKG? Often produces low voltage amplitude in all leads Usually RAD Multifocal Atrial Tachycardia is also seen with COPD RV hypertrophy
What are the characteristics of PE on EKG? Acute transient Right Bundle Branch Block R.A.D. and clockwise rotation Inverted t-waves in V1 – V4 ST depression in Lead II S1Q3T3
What are the characteristics of hyperkalemia on EKG? P-wave flattens down QRS complex widens T-wave becomes peaked
What are the characteristics of hypokalemia on EKG? Flattened or inverted t-waves Appearance of a u-wave Low serum potassium can initiate Torsades de Pointes and V-tach
What are the characteristics of Hypocalcemia on EKG? QT interval is prolonged
What are the characteristics of Hypercalcemia on EKG? QT interval shortens
What are the exclusionary criteria for RVH? RBBB Post-wall MI young children *if present, then can not diagnose RVH.
RV strain pattern signs? ST frowning (concave) in v1 or v2
LV strain pattern signs? ST smiling (convex) in v1 or v2
What is the difference between strain pattern and ischemic pattern? strain = non-symmetric T wave and curving ST segment ischemic = symmetric T wave and non-curving ST segment
Created by: toppu2020