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EKG
Kevin's EKG Interpretation Lecture (SIUE Nurse Anesthesia)
| Question | Answer |
|---|---|
| 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 |
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