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ECG Workshop Combo Ahmed Nahian, B.S., M-I ELECTROCARDIOGRAPHY WORKSHOP PART I Carmine D’Amico, D.O. Electrocardiography Overview Introduction Basic Principles Rate Axis Rhythm Intraventricular Conduction Defects Hypertrophy Ischemia, Infarction, and Pericarditis Putting It All...
ECG Workshop Combo Ahmed Nahian, B.S., M-I ELECTROCARDIOGRAPHY WORKSHOP PART I Carmine D’Amico, D.O. Electrocardiography Overview Introduction Basic Principles Rate Axis Rhythm Intraventricular Conduction Defects Hypertrophy Ischemia, Infarction, and Pericarditis Putting It All Together Electrocardiography Learning Objectives 1. Identify each of the deflections (waves) that may be seen on an EKG tracing. 2. Identify the PR interval, PR segment, QT interval, and ST segment on an EKG tracing. 3. Describe the physiological events that are responsible for the various waves, segments, and intervals that may be seen on an EKG tracing. 4. On a cellular level, explain the physiological cause for upward and downward deflections on an EKG tracing. Electrocardiography Learning Objectives (cont.) 5. Determine heart rate from rhythm strips and EKG’s. 6. Compare and contrast the bipolar limb leads from the augmented limb leads. 7. Contrast the limb leads from the precordial leads based on their anatomical plane of orientation (frontal versus horizontal). 8. Determine the mean QRS vector (axis) in the frontal plane. 9. Determine the mean QRS vector (axis) in the horizontal plane. Electrocardiography Recommended text Electrocardiography “Suggested” Reading EKG Workshop I Dubin, Chapters 1, 2, 4, & 7 EKG Workshop II Dubin, Chapter 5 EKG Workshop III Dubin, Chapters 6 & 8 EKG Workshop IV Dubin, Chapter 9 Electrocardiography Supplemental text Electrocardiography Supplemental text Electrocardiography Supplemental text Electrocardiography Background Developed by Dr.Willem Einthoven in 1901 Most frequently used cardiac diagnostic test Clinical utility attributable to: Widespread availability Ease of performance Relative cost permissiveness Lack of procedural risk or contraindications High yield of useful information about the function and structure of the heart Willem Einthoven 1860-1927 Nobel Prize winner, 1924 Electrocardiography Basic Principles Myocyte contraction depends upon myocyte depolarization Myocyte depolarization occurs as a wave which travels from one end of the myocyte to the other Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) A wave of depolarization traveling towards a positive EKG electrode causes a/an up deflection on the EKG tracing A wave of depolarization traveling away from a positive EKG electrode causes a/an down deflection on the EKG tracing Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) A wave of repolarization traveling towards a positive EKG electrode causes a/an down deflection on the EKG tracing A wave of repolarization traveling away from a positive EKG electrode causes a/an up deflection on the EKG tracing Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Nomenclature In electrocardiography, an interval includes at least one of the waves that it is named after, whereas a segment does not. In other words, a segment is simply a section of baseline which is between the waves that it is named after. Electrocardiography Basic Principles (cont.) Nomenclature (cont.) By convention, the following intervals are defined as: PR interval: distance (time) from beginning of P wave to beginning of QRS complex (includes P wave but not the QRS complex) time between depolarization QT interval: distance (time) from beginning of QRS complex to end of T wave (includes the QRS complex and the T wave ) ST interval: distance (time) from end of QRS complex to end of T wave (includes the T wave but not the QRS complex) Electrocardiography Basic Principles (cont.) Nomenclature (cont.) By convention, intervals and segments involving the QRS complex are named as follows*: PR (interval or segment)- even if there is a Q wave QT interval- even if there is no Q wave ST (interval or segment)- even if there is no S wave *There is no “rhyme or reason” for these idiosyncrasies! Electrocardiography Basic Principles (cont.) J point: The point where the QRS complex and the ST segment meet ST segment = plateau phase PR interval PR segment ST interval Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) More on left, so it is positive. Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Electrocardiography Basic Principles (cont.) Describe the physiological event that is responsible for the U wave on an EKG tracing. Fastest depolarizers are Purkinje; slowest repolarizer (what it is) Electrocardiography Rate On a standard EKG: The vertical axis* represents voltage. the tracing At standard calibration, 1 mm = 0.1 mV The horizontal axis* represents time. of of the tracing At standard paper speed (25 mm/sec.), 1 mm = 0.04 sec. = 40 msec. *Don’t confuse these axes with the electrical axes Electrocardiography Rate (cont.) Electrocardiography Rate (cont.) Since the horizontal distance between consecutive bold lines on an EKG represents 0.2 sec. (5 mm = 0.2 sec.), this same distance represents: 1/5 sec. 1/300 min. In other words, there are 5 “big blocks” per second, and 300 “big blocks” per minute. Electrocardiography Rate (cont.) Therefore, the heart rate (the number of beats per minute) equals 300 divided by the number of “big blocks” between consecutive beats on a standard EKG tracing.* *This is only true for regular rhythms. Electrocardiography Rate (cont.) 1 interval 300/5 blocks = 60 Electrocardiography Rate (cont.) 300/5 blocks = 60 Electrocardiography Rate (cont.) For exceptionally slow heart rates or irregular rhythms, the 3 second interval marks may be used to determine heart rate. Simply count the number of cardiac cycles (R-to-R intervals) over 2 consecutive 3 second intervals, and then multiply this number by 10 in order to determine the heart rate in beats per minute. Electrocardiography Rate (cont.) Electrocardiography (Electrical) Axis The mean electrical axis can be determined in 2 separate planes for any of the waves on a standard 12-lead EKG: Frontal plane Horizontal plane Electrocardiography Axis (cont.) Standard 12-lead EKG 6 limb leads (I, II, III, aVR, aVL, aVF) Allow determination of axis in the frontal plane 6 precordial (chest) leads (V1 – V6) Allow determination of axis in the horizontal plane Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Chest Leads Lead Positive Electrode Position Heart Surface Viewed V1 Right side of sternum, fourth intercostal space Septum V2 Left side of sternum, fourth intercostal space Septum V3 Midway between V2 and V4 Anterior V4 Left midclavicular line, fifth intercostal space Anterior V5 Left anterior axillary line; same level as V4 Lateral V6 Left midaxillary line; same level as V4 Lateral Copyright © 2012 by Mosby, an imprint of Elsevier Inc. 48 Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) 6 limb leads 3 Bipolar limb leads Each has 1 positive and 1 negative electrode 3 Augmented unipolar limb leads Each has 1 positive electrode and 1 compound reference electrode Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Since the 3 limbs from which voltages are measured when recording a standard EKG are the right arm (RA), the left arm (LA), and the left leg (LL), there are only three possible combinations for bipolar limb leads… Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL Electrocardiography Axis (cont.) D’Amico’s rule of “L”’s For the bipolar limb leads: 1. The name of the lead equals the sum of the number of “L”’s in the abbreviations of the limbs composing that lead. 2. The positive electrode of each lead is located on the limb with the most “L”’s in its abbreviation. Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL lead I Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL lead I Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III Electrocardiography Axis (cont.) D’Amico’s rule of “L”’s For the bipolar limb leads: 1. The name of the lead equals the sum of the number of “L”’s in the abbreviations of the limbs composing that lead. 2. The positive electrode of each lead is located on the limb with the most “L”’s in its abbreviation. Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III LA(+) Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III LA(+) Electrocardiography Axis (cont.) RA – LA lead I LA(+) RA – LL lead II LL(+) LA – LL lead III Electrocardiography Axis (cont.) RA – LA lead I LA(+) RA – LL lead II LL(+) LA – LL lead III Electrocardiography Axis (cont.) RA – LA lead I LA(+) RA – LL lead II LL(+) LA – LL lead III LL(+) Electrocardiography Axis (cont.) RA – LA RA – LL LA – LL Electrocardiography Axis (cont.) RA – LA lead I RA – LL lead II LA – LL lead III Electrocardiography Axis (cont.) RA – LA lead I LA(+) RA – LL lead II LL(+) LA – LL lead III LL(+) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) 6 limb leads 3 Bipolar limb leads Each has 1 positive and 1 negative electrode 3 Augmented unipolar limb leads Each has 1 positive electrode and 1 compound reference electrode Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) 3 steps for determining the QRS axis in the frontal plane 1. Locate the most isoelectric lead. The lead in which the difference between the amount of QRS deflection above and below the isoelectric line is closest to zero 2. Locate the lead 90 degrees from the most isoelectric lead. 3. The QRS axis is along this lead (perpendicular to the isoelectric lead), in the direction corresponding to the polarity of the QRS complex in that lead. Electrocardiography Axis (cont.) What is the QRS axis in this “EKG”? Electrocardiography Axis (cont.) What is the QRS axis in the EKG below? Electrocardiography Axis (cont.) What is the QRS axis in the EKG below? Electrocardiography Axis (cont.) Although less accurate, the QRS axis (in the frontal plane) can be quickly localized to a quadrant by glancing at leads I and aVF. Lead I -90 _ + I If lead I is positive, the green zone reveals the area of electrical activity 0 aVF – aVF -90 If aVF is positive, the red zone reveals the area of electrical activity + I 0 aVF -90 I 0 aVF +90 If we superimpose these onto one another we find the axis to be between 0° & +90° Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) _ Lead I -90 + If lead I is positive then the blue zone is the area of electrical activity I 0 aVF +90 _ aVF -90 If aVF is negative, the green zone is the area of electrical activity + I 0 aVF +90 If we superimpose these onto one another we find the axis to be between 0° & –90° -90 I 0 aVF +90 Electrocardiography Axis (cont.) _ Lead I -90 + If lead I is negative the green zone encompasses the area of electrical activity I 180 0 aVF +90 _ aVF -90 If aVF is positive, the red zone reveals the area of electrical activity + I 180 aVF +90 0 -90 I 180 If we superimpose these onto one another, we find the axis to be between 90° & 180° aVF +90 0 Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) A shift in the electrical axis out of the normal range is referred to as: “Deviation” in the frontal plane Left Right Extreme right “Rotation” in the horizontal plane Leftward Rightward Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Note: You do NOT need to see an isoelectric lead (or even identify the most isoelectric lead) when determining the axis in the horizontal plane! Electrocardiography Axis (cont.) Simply stated, in determining the mean QRS axis in the horizontal plane: If the R to S ratio changes from <1 to >1: After V4 (i.e. V5, V6, or never), then this is referred to as “leftward axis rotation” At or before V2 (i.e. V1, or V2), then this is referred to as “rightward axis rotation” After V2 and at or before V4, then the axis in the horizontal plane is referred to as “normal” Electrocardiography Axis (cont.) Additional rules for determining the mean QRS axis in the horizontal plane: If the R to S ratio: Starts < 1 and stays < 1, then this is referred to as “leftward axis rotation” Starts >1 and stays > 1, then this is referred to as “rightward axis rotation” Starts > 1 and becomes < 1 by V6, then this is referred to as “leftward axis rotation” Electrocardiography Axis (cont.) Describe the QRS axis in the horizontal plane in the EKG below. Electrocardiography Axis (cont.) Describe the QRS axis in the horizontal plane in the EKG below. Electrocardiography Axis (cont.) Note: Beware of “lead change lines” when interpreting 12-lead EKG’s! Electrocardiography Axis (cont.) Describe the QRS axis in the horizontal plane in the EKG below. Electrocardiography Axis (cont.) Fascicular block (hemiblock) Electrocardiography Axis (cont.) Fascicular block (hemiblock) (cont.) Left anterior (LAFB or LAHB) QRS axis between –45 and –90 degrees rS patterns in II, III, and aVF (near) normal QRS duration (unless RBBB coexists) Small Q waves in I and aVL Electrocardiography Axis (cont.) Fascicular block (hemiblock) (cont.) Left posterior (LPFB or LPHB) QRS axis +90 to 180 degrees (near) normal QRS duration (unless RBBB coexists) Small Q waves in III (and sometimes II &/or aVF) rS pattern in I (and often aVL) Exclusion of other causes of RAD Lateral wall MI RVH Emphysema/vertical heart ELECTROCARDIOGRAPHY WORKSHOP PART II Carmine D’Amico, D.O. Electrocardiography Overview Introduction Basic Principles Rate Axis Rhythm Intraventricular Conduction Defects Hypertrophy Ischemia, Infarction, and Pericarditis Putting It All Together Electrocardiography Learning Objectives 1. Define automaticity focus, and list the inherent rate range for each automaticity focus at each “level” of the heart. 2. Define overdrive suppression. 3. Discuss the concept of “escape” as a protective mechanism. 4. Differentiate normal sinus rhythm from sinus bradycardia and sinus tachycardia on EKG tracings. 5. Recognize sinus arrhythmia on EKG tracings. Electrocardiography Learning Objectives (cont.) 6. Differentiate sinus rhythm from atrial and junctional rhythms on EKG tracings. 7. Differentiate between sinus beats, atrial beats, junctional beats, and ventricular beats on EKG tracings. 8. Differentiate unifocal ventricular beats from multifocal ventricular beats on EKG tracings. 9. Differentiate escape beats from premature beats on EKG tracings. Electrocardiography Learning Objectives (cont.) 10. Recognize non-conducted premature atrial beats on EKG tracings. 11. Define and recognize the common premature beat patterns (bigeminy, trigeminy, and quadrigeminy) on EKG tracings. 12. In terms of heart rate (for adults), define bradycardia, normal, tachycardia, flutter, and fibrillation. 13. Recognize QT interval prolongation on EKG tracings and discuss its clinical relevance. Electrocardiography Learning Objectives 14. Recognize/ differentiate between the following rhythms (on EKG tracings): wandering atrial pacemaker multifocal atrial tachycardia atrial fibrillation atrial flutter ventricular tachycardia ventricular fibrillation ventricular flutter 15. Recognize ventricular pre-excitation (WolffParkinson-White syndrome) on a 12-lead EKG. Electrocardiography “Suggested” Reading EKG Workshop I Dubin, Chapters 1, 2, 4, & 7 EKG Workshop II Dubin, Chapter 5 EKG Workshop III Dubin, Chapters 6 & 8 EKG Workshop IV Dubin, Chapter 9 Electrocardiography Rhythm (and Conduction) Cardiac Conduction System: Electrocardiography Rhythm (cont.) Cardiac Conduction System (cont.): Electrocardiography Rhythm (cont.) Cardiac Conduction System (cont.): Electrocardiography Rhythm (cont.) Concepts and terminology Automaticity Ability of specialized cells to spontaneously generate electrical impulses which may then spread throughout surrounding tissue. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Automaticity foci Potential pacemakers within the heart The inherent rates for automaticity foci vary depending upon their location: Atrial foci 60-80 per min Junctional (AV nodal) foci 40-60 per min Ventricular foci 20-40 per min Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Overdrive suppression The pacemaker with the fastest rate is the dominant pacemaker. Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Escape A protective mechanism whereby an automaticity focus with the next highest inherent rate begins pacing (escapes overdrive suppression) in the event of a pause or cessation of pacing activity of the previously dominant pacemaker. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Escape beat Transient escape of an automaticity focus (from overdrive suppression) to generate one beat. This occurs when there is a pause in pacing activity in the previously dominant pacemaker. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Escape rhythm Escape of an automaticity focus (from overdrive suppression) with subsequent pacing by that automaticity focus, at its inherent rate. This occurs when there is a cessation (or arrest) of pacing activity in the previously dominant pacemaker. Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Sinus Rhythm EKG Criteria: Each QRS complex is preceded by a P wave. The P waves must be positive in lead II, and negative in lead aVR. Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) + Electrocardiography Rhythm (cont.) P wave axis with sinus rhythm: Electrocardiography Rhythm (cont.) P wave axis with sinus rhythm: Electrocardiography Axis (cont.) Electrocardiography Axis (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) + Electrocardiography Rhythm (cont.) P wave axis with sinus rhythm: Electrocardiography Rhythm (cont.) P wave axis with sinus rhythm: Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) P wave axis with AV junctional rhythm: Electrocardiography Rhythm (cont.) P wave axis with AV junctional rhythm: Electrocardiography Rhythm (cont.) P wave axis with AV junctional rhythm: Electrocardiography Rhythm (cont.) Normal Sinus Rhythm EKG Criteria: Sinus rhythm with a heart rate between 60 and 100 beats per minute Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Sinus Bradycardia EKG Criteria: Sinus rhythm with a heart rate less than 60 beats per minute Electrocardiography Rhythm (cont.) Sinus Tachycardia EKG Criteria: Sinus rhythm with a heart rate greater than 100 beats per minute Electrocardiography Rhythm (cont.) Sinus Arrhythmia EKG Criteria: Same criteria as sinus rhythm and there is greater than 0.16 sec. difference between the shortest and the longest PP intervals within the same EKG tracing Most common cause is respiration Heart rate increases with inspiration and decreases with expiration (due to changes in vagal tone during Electrocardiography Rhythm (cont.) Sinus Arrhythmia: Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) The key to determining the origin of a completely inverted P wave in lead II is the length of the PR interval.* *Provided that there is no AV nodal dysfunction Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Junctional beats In summary: Depending on the specific location of the automaticity focus within the AV node, as well as individual conduction variability, AV junctional beats may be recognized on the EKG by one of three possible patterns: Electrocardiography Rhythm (cont.) Junctional beats (cont.) Retrograde P wave (positive in lead aVR and negative in lead II) immediately preceding (PR interval <120 msec) the QRS complex: Electrocardiography Rhythm (cont.) Junctional beats (cont.) Retrograde P wave (positive in lead aVR and negative in lead II) immediately following the QRS complex: aVR II Electrocardiography Rhythm (cont.) Junctional beats (cont.) Absent P wave (buried in the QRS complex or absent due to lack of retrograde AV conduction): aVR II Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Determining a beat’s origin The width (duration) of the QRS complex may provide a clue to that beat’s origin. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Determining a beat’s origin (cont.) If the QRS complex is not prolonged (not >120 msec.), ventricular depolarization must have occurred via the His-Purkinje system (i.e. that beat must have originated above the ventricles). The opposite of this is not true All wide QRS complexes are not necessarily ventricular in origin. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Irritability An increase in the tendency for automaticity foci to spontaneously generate electrical impulses Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Irritability (cont.) Automaticity foci may become irritable for multiple reasons, including: Hypoxia Electrolyte disturbances Mechanical stretch Sympathetic (B1) stimulation Other cardiac stimulants Infection Hyperthyroidism Toxins Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Premature beat Occurs when an irritable automaticity focus spontaneously generates a single electrical impulse prior to the next expected beat from the dominant pacemaker Also known as an “extrasystole” Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Synonymous terms: Premature atrial contraction (PAC) Premature atrial beat (PAB) Atrial premature contraction (APC) Atrial premature beat (APB) Similar terminology is used for junctional and ventricular premature beats. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Escape beats and premature beats differ by: Timing of occurrence (relative to the preceding beat) Mechanism: escape of an automaticity focus (from overdrive suppression) due to failure of the previously dominant pacemaker, versus irritability of an automaticity focus Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Unifocal PVC’s: Electrocardiography Rhythm (cont.) Multiform (multifocal) PVC’s: Electrocardiography Rhythm (cont.) Concepts and terminology Premature beat patterns Bigeminy – every other beat is premature Trigeminy – every third beat is premature Quadrigeminy – every fourth beat is premature Electrocardiography Rhythm (cont.) Atrial Bigeminy: Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Paroxysmal Sudden Sustained (arrhythmia) Greater than 30 seconds in duration Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Bradycardia Tachycardia Heart rate > 100 bpm Flutter Heart rate < 60 beats per minute (bpm) Rate between 250 and 350 bpm Fibrillation Rate between 350 and 450 bpm Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Supraventricular tachycardia (SVT) A “generic” term for any tachycardia originating above the ventricles However, in clinical practice, sinus tachycardia is not usually treated like other SVT’s (since it is usually a physiologic response to other things) Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Arrhythmogenesis Production of arrhythmias Electrocardiography Rhythm (cont.) Mechanisms of arrhythmogenesis Disorders of impulse formation Disorders of impulse propagation Combination of both Some arrhythmias can be started by one mechanism and perpetuated by another. Electrocardiography Rhythm (cont.) Tachyarrhythmias Disorders of impulse formation Enhanced automaticity Due to irritability Triggered activity Pacemaker activity which is dependent upon a preceding impulse or series of impulses (initiated by afterdepolarizations) Electrocardiography Rhythm (cont.) “R on T” Phenomenon: Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) Torsades de pointes Polymorphic ventricular tachycardia (VT) which is preceded by marked prolongation of the QT interval Due to triggered activity (from early afterdepolarizations) related to “R on T” phenomenon, facilitated by marked QT prolongation Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) Torsades de pointes (cont.) Polymorphic QRS complexes change in amplitude and cycle length, giving the appearance of oscillations twisting around the baseline (“twisting of the points”). QT prolongation may be congenital or acquired. Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) QT interval must be corrected for heart rate Estimation: The QT interval should be less than half of the R-to-R interval which contains that QT interval. Bazett formula (1920!): QT = C Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) Disorders of impulse propagation Reentry Most common mechanism of tachyarrhythmias “Short circuit” of normal conduction system Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) Disorders of impulse propagation Reentry (cont.) Examples: Atrial fibrillation Atrial flutter AV nodal reentry tachycardia (AVNRT) Wolff-Parkinson-White (WPW) syndrome Lown-Ganong-Levine (LGL) syndrome Ventricular tachycardia (some) Ventricular fibrillation Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Tachyarrhythmias (cont.) Ventricular tachycardia Monomorphic: QRS complexes all look alike Polymorphic: QRS complexes vary in size and shape Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) ELECTROCARDIOGRAPHY WORKSHOP PART III Carmine D’Amico, D.O. Electrocardiography Overview Introduction Basic Principles Rate Axis Rhythm Intraventricular Conduction Defects Hypertrophy Ischemia, Infarction, and Pericarditis Putting It All Together Electrocardiography Learning Objectives 1. Differentiate the various degrees of AV block on EKG tracings. 2. On EKG tracings, differentiate junctional from ventricular escape rhythms that may occur in association with high-grade AV block. 3. Identify bundle branch blocks (right and left) on a 12- lead EKG. 4. Identify ventricular hypertrophy (right and left) on a 12-lead EKG. 5. Identify atrial abnormality (right and left) on a 12-lead EKG. Electrocardiography “Suggested” Reading EKG Workshop I Dubin, Chapters 1, 2, 4, & 7 EKG Workshop II Dubin, Chapter 5 EKG Workshop III Dubin, Chapters 6 & 8 EKG Workshop IV Dubin, Chapter 9 Electrocardiography Rhythm (cont.) Bradyarrhythmias Disorders of impulse formation Sinus node dysfunction (with or without subsequent escape rhythms) Disorders of impulse propagation Conduction disturbances (“block”) may occur at any level of the conduction system. SA block AV block Bundle branch block Fascicular block Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Disorders of impulse formation Sick-sinus syndrome Encompasses several SA nodal abnormalities: Chronotropic incompetence Sinus pause, arrest or exit block Bradycardia-tachycardia syndrome: Paroxysms of atrial tachyarrhythmias alternating with slow atrial and ventricular rates Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Disorders of impulse propagation AV block First degree Second degree Type I (Wenckebach) Type II Third degree (complete) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) First degree AV block 1-to-1 ratio of P waves to QRS complexes PR interval is fixed (consistent) PR interval exceeds 200 msec Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Second degree AV block Type I (Wenckebach) Type II BEWARE of confusing terminology Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Second degree AV block (cont.) Other names for the 2 types of second degree AV block: Type I: Mobitz type I Wenckebach Type II: Mobitz type II Mobitz (Dr. Dubin) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Type I second degree AV block may present in one of two ways: Grouped beats Groups or clusters of QRS complexes separated by “missed” single beats Two P waves for every QRS complex, without groups or clusters of beats All PR intervals will be the same (fixed/consistent) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Type I second degree AV block (cont.): Grouped beats (cont.) Within each group or cluster (of QRS complexes): There is always one (and only one) more P wave than there are QRS complexes. Close inspection reveals progressive lengthening of the PR interval until one of the P waves is not followed by a QRS complex, and then the pattern repeats. Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) In Type II second degree AV block: There are more P waves than QRS complexes All P waves that immediately precede QRS complexes have equal PR intervals At times, there may be a fixed ratio of P waves to QRS complexes (e.g. 2-to-1*, 3-to-1, or 4-to-1, etc.) *Remember: 2-to-1 second degree AV block may be either Type I or Type II Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Third degree (complete) AV block Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) For further clarification: First degree AV block: Second degree AV block (both types): All of the supraventricular impulses are conducted to the ventricles. Some, but not all, of the supraventricular impulses are conducted to the ventricles. Third degree (complete) AV block: None of the supraventricular impulses are conducted to the ventricles. Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) For further clarification (cont.): Whenever the ratio of P waves to QRS complexes is “2:1” If the PR intervals are all the same, then we refer to it as “ 2-to-1 second degree AV block”, without specifying Type I or Type II. If the PR intervals are variable, then the block is probably third degree (complete) AV block! Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Determining an escape rhythm’s origin Ventricular rate is not as reliable as QRS width in determining an escape rhythm’s origin If the QRS complexes during the escape rhythm are narrow (< 120 msec.), then the escape rhythm cannot be ventricular in origin. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Determining a beat’s origin If the QRS complex is not prolonged (not >120 msec.), ventricular depolarization must have occurred via the His-Purkinje system (i.e. that beat must have originated above the ventricles). The opposite of this is not true All wide QRS complexes are not necessarily ventricular in origin. Electrocardiography Rhythm (cont.) Concepts and terminology (cont.) Determining an escape rhythm’s origin (cont.) If the QRS complexes during the escape rhythm are wide (> 120 msec.), then the escape rhythm may be ventricular in origin. Ventricular origin is more likely if the QRS complexes were narrow prior to the escape rhythm (but are now wide). Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Third degree AV block is only one of the potential causes of AV dissociation. Other causes of AV dissociation: Default Slowing of the previously dominant pacemaker, with subsequent junctional or ventricular escape rhythm Usurpation Acceleration of a latent pacemaker which usurps control of the ventricles Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) When AV dissociation exists: The relationship between the atrial and ventricular rates allows differentiation of third degree (complete) AV block from the other potential causes of AV dissociation. Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) Relationship between atrial and ventricular rates in AV dissociation: Third degree AV block Default Atrial rate exceeds ventricular rate Ventricular rate exceeds atrial rate Usurpation Ventricular rate exceeds atrial rate Electrocardiography Rhythm (cont.) Bradyarrhythmias (cont.) In other words: When AV dissociation exists and the atrial rate is faster than the ventricular rate, then the AV dissociation is due to third degree (complete) AV block. When AV dissociation exists and the atrial rate is slower than the ventricular rate, then the AV dissociation cannot be attributed to AV block. Electrocardiography Intraventricular Conduction Defects Bundle branch blocks Right Left Complete (QRS duration > or = to 0.12 sec.) Incomplete (QRS duration between 0.10 and 0.12 sec.) Characteristic QRS pattern in leads V1, I, (+/- V6) Complete Incomplete Characteristic QRS pattern in leads V1, I, (+/- V6) Nonspecific intraventricular conduction defect Prolonged QRS, but not RBBB or LBBB pattern Electrocardiography IVCD’s (cont.) Right bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Right bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Right bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Right bundle branch block (RBBB) (cont.) rSR’ pattern in lead V1 Wide S wave in lead I (+/- V6) Complete: QRS duration > or = to 0.12 sec. Incomplete: QRS duration between 0.10 and 0.12 sec. Electrocardiography IVCD’s (cont.) Left bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Left bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Left bundle branch block: I +/- Electrocardiography IVCD’s (cont.) Left bundle branch block (LBBB) (cont.) Broad, sometimes notched R wave in leads I (+/- V6) Absent q waves in leads I, aVL, (+/- V6) Wide and deep S waves in lead V1 Complete: QRS duration > or = to 0.12 sec. Incomplete: QRS duration between 0.10 and 0.12 sec. Electrocardiography IVCD’s (cont.) I +/- Recognizing Bundle Branch Block Criteria for bundle branch block recognition QRS duration of >0.12 sec (if a complete BBB) QRS complexes produced by supraventricular activity (i.e., the QRS complex is not a paced beat nor did it originate in the ventricles) Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 277 Recognizing Bundle Branch Block Look at lead V1 or MCL1 Move from J-point back into QRS complex Determine if terminal portion (last 0.04 sec) of QRS complex is positive or negative Positive = right BBB Negative = left BBB Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 278 Turn Signal Theory Right is up Left is down Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 279 Electrocardiography IVCD’s (cont.) Nonspecific Intraventricular Conduction Defect (Nonspecific IVCD) QRS duration > 120 msec. Criteria for RBBB are not met Criteria for LBBB are not met Electrocardiography Hypertrophy Ventricular Left Ventricular Hypertrophy (LVH) Right Ventricular Hypertrophy (RVH) Biventricular Hypertrophy Atrial (abnormality) Left Atrial Abnormality Right Atrial Abnormality Biatrial Abnormality Electrocardiography Hypertrophy Ventricular Many criteria by many authors Voltage criteria ST segment and T wave changes Limb leads Precordial leads Provide supportive evidence of ventricular hypertrophy Increase the specificity of voltage criteria in diagnosing ventricular hypertrophy QRS axis deviation Electrocardiography Hypertrophy Electrocardiography Hypertrophy Deeper of V1 or V2 or V2 or V6 or V6 TALLER (positive) Taller of V5 40 + Electrocardiography Hypertrophy Electrocardiography Ischemia Electrocardiography Hypertrophy RVH (cont.) Presence of all 3 criteria strongly suggests RVH: Right axis deviation (> 110°) R/S > 1 in lead V1 Deep S waves in lead V5 or V6 Electrocardiography “Hypertrophy” (cont.) Atrial (abnormality) Inspect P waves in leads V1 and II for: Amplitude Duration Morphology Electrocardiography “Hypertrophy” (cont.) Normals: In sinus rhythm, without right or left atrial abnormality, the P waves: In lead V1 are: Sometimes biphasic < 1.5 mm high (initial upright (RA) portion) < 1.0 mm deep (terminal negative (LA) portion) In lead II are: Upright < 2.5 mm high < 120 msec in duration (< 3 mm wide) Electrocardiography “Hypertrophy” (cont.) Right atrial abnormality: In sinus rhythm, the P waves: In lead V1 are: > 1.5 mm high (initial upright (RA) portion) ……………………… or ………………………… In lead II are: > 2.5 mm high If peaked, referred to as “p pulmonale” Electrocardiography “Hypertrophy” (cont.) Left atrial abnormality: In sinus rhythm, the P waves: In lead V1 are: > 1.0 mm deep and > 1.0 mm wide (terminal negative (LA) portion) …………………….. or ……………………………… In lead II are: > 120 msec in duration (> 3 mm wide) If notched, referred to as “p mitrale” McDonald’s = p mitrale Electrocardiography “Hypertrophy” (cont.) Biatrial abnormality: In sinus rhythm, the P waves: Meet the criteria for right atrial abnormality in lead V1 and/or lead II …………………. and ………………………. Meet the criteria for left atrial abnormality in lead V1 and/or lead II Electrocardiography “Hypertrophy” (cont.) Atrial abnormality (cont.) Electrocardiography “Hypertrophy” (cont.) ELECTROCARDIOGRAPHY WORKSHOP PART IV Carmine D’Amico, D.O. Electrocardiography Overview Introduction Basic Principles Rate Axis Rhythm Intraventricular Conduction Defects Hypertrophy Ischemia, Infarction, and Pericarditis Putting It All Together Electrocardiography Learning Objectives 1. Identify and localize acute myocardial infarction on a 12-lead EKG. 2. Differentiate acute myocardial infarction from acute pericarditis from early repolarization on a 12-lead EKG. 3. List the criteria for “significant” Q waves. 4. Differentiate “age-indeterminate” (i.e. old, or previous) myocardial infarction from acute myocardial infarction on a 12-lead EKG. 5. Identify and localize age-indeterminate myocardial infarction on a 12-lead EKG. Electrocardiography Learning Objectives (cont.) 6. Interpret a 12-lead EKG using a systematic approach. This interpretation should include: a. b. c. d. e. f. g. h. i. Rate Rhythm Intervals QRS axis Conduction Atrial abnormality Ventricular hypertrophy Extra or abnormal waves ST segment and T wave changes Electrocardiography “Suggested” Reading EKG Workshop I Dubin, Chapters 1, 2, 4, & 7 EKG Workshop II Dubin, Chapter 5 EKG Workshop III Dubin, Chapters 6 & 8 EKG Workshop IV Dubin, Chapter 9 Electrocardiography ST Segment Elevation ST segment elevation has many potential causes: Acute myocardial infarction Acute myocarditis Acute pericarditis Myocardial contusion Coronary artery spasm Left ventricular aneurysm Early repolarization LVH LBBB Hyperkalemia Hypothermia Scorpion sting Electrocardiography ST Segment Elevation (cont.) Interpreting ST elevation: Distribution Reciprocal ST depression Not as reliable PR depression: Present or absent? ST segment shape: Regional (vascular) or diffuse? Present or absent Clinical presentation Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury Myocardial involvement Anterior Anteroseptal Anterolateral Extensive Anterior Lateral High lateral Inferior Inferolateral Posterior Inferoposterolateral Right Ventricular EKG leads V2, V3, V4 (at least 2) V1, V2, V3 (+V4) V4, V5, V6 (+V3, +V2) V1 through V6 (all) V5, V6 (+I, +aVL) I, aVL II, III, aVF (at least 2) as above, +V6 (+V5) V1, V2 (*recip. changes) Combine above 3 items V4R, +V3R and/or V5R Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury (cont.) Another way to think about it*… *Shared with me by a LECOM MS2 student in September 2022 Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury (cont.) EKG leads in the horizontal plane detect infarction in the anterior, posterior, and lateral* myocardium • • • • • • • Anterior Anteroseptal Anterolateral Extensive Anterior Posterior Right Ventricular Lateral* V2, V3, V4 (at least 2) V1, V2, V3 (+V4) V4, V5, V6 (+V3, +V2) V1 through V6 (all) V1, V2 (recip. changes) V4R, +V3R and/or V5R V5, V6 (+I, +aVL) *Since the horizontal and frontal planes intersect laterally, lateral infarction has overlap with both precordial and limb leads. Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury (cont.) EKG leads in the frontal plane detect infarction in the high lateral and inferior myocardium • • • High lateral Inferior Inferolateral* • Inferoposterolateral* I, aVL II, III, aVF (at least 2) as above, +V6 (+V5) Inferolateral + posterior *Since the horizontal and frontal planes intersect laterally, lateral infarction has overlap with both precordial and limb leads. Electrocardiography ST Segment Elevation (cont.) Reciprocal ST depression: Electrocardiography ST Segment Elevation (cont.) ST elevation shapes: Electrocardiography ST Segment Elevation (cont.) Early repolarization ST elevation: Distribution: Diffuse (usually) Reciprocal ST depression: Absent ST segment shape: Concave upwards PR depression: Absent Clinical: Asymptomatic; usually an incidental finding on a routine EKG; often present in young males Electrocardiography ST Segment Elevation (cont.) Early Repolarization: Electrocardiography ST Segment Elevation (cont.) Early Repolarization (another example): Electrocardiography ST Segment Elevation (cont.) Acute pericarditis ST elevation: Distribution: Diffuse (usually) Reciprocal ST depression: Absent ST segment shape: Concave upwards PR depression: Present (in leads that have ST elevation) Clinical: (usually) gradual onset of sharp, pleuritic chest discomfort, which is often relieved or improved by sitting up; sometimes preceded or accompanied by fever or other flu-like symptoms Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute Pericarditis: Electrocardiography ST Segment Elevation (cont.) Acute MI ST elevation: Distribution: Regional (vascular) Reciprocal ST depression: Present (if MI involves inferior or high lateral wall) ST segment shape: Not as reliable Concave down (if “textbook” case) PR depression: Absent Clinical: (usually) Sudden onset of nonsharp, non-pleuritic chest discomfort or dyspnea; sometimes accompanied by nausea, vomiting, and/or diaphoresis Electrocardiography ST Segment Elevation (cont.) Acute Myocardial Infarction (AMI): Electrocardiography ST Segment Elevation (cont.) Localization of Myocardial Injury Myocardial involvement Anterior Anteroseptal Anterolateral Extensive Anterior Lateral High lateral Inferior Inferolateral Posterior Inferoposterolateral Right Ventricular EKG leads V2, V3, V4 (at least 2) V1, V2, V3 (+V4) V4, V5, V6 (+V3, +V2) V1 through V6 (all) V5, V6 (+I, +aVL) I, aVL II, III, aVF (at least 2) as above, +V6 (+V5) V1, V2 (*recip. changes) Combine above 3 items V4R, +V3R and/or V5R ACUTE CORONARY SYNDROME No ST Elevation ST Elevation NSTEMI Unstable Angina NQMI QwMI Electrocardiography Infarction (cont.) Myocardial infarction may be diagnosed on an EKG as: ST segment elevation Deep, symmetrically inverted T waves Acute ST elevation MI Non-ST elevation MI (acute or recent) Other causes: myocardial ischemia, ICH “Significant” Q waves “Age-indeterminate” (i.e. old, or previous) MI Electrocardiography Infarction (cont.) “Hyperacute” T waves: Electrocardiography Infarction (cont.) NSTEMI vs. STEMI: Electrocardiography Infarction (cont.) Since NSTEMI and myocardial ischemia may both cause very similar EKG changes (ST depression and/or T wave inversion), the diagnosis of NSTEMI can only be confirmed by: Serum cardiac marker elevation Gross examination of myocardium Intraoperative examination Postmortem examination Electrocardiography Q waves Q waves have many potential causes: Normal variant (V1, V2, III, aVF, lateral leads) Myocardial infarction (age-indeterminate) Left bundle branch block Ventricular pre-excitation (e.g. WPW syndrome) Hypertrophic cardiomyopathy Myocarditis (acute or chronic) Cardiomyopathies (infiltrative, idiopathic, etc.) Ventricular hypertrophy (LVH, RVH) Myocardial tumor Left pneumothorax Chronic obstructive lung disease Hyperkalemia, phos. tox., protracted hypoglycemia Electrocardiography Q waves (cont.) Pseudoinfarction pattern, LBBB: Electrocardiography Q waves (cont.) Pseudoinfarction pattern, WPW: Electrocardiography Infarction (cont.) Electrocardiography Infarction (cont.) Electrocardiography Infarction (cont.) Electrocardiography Infarction (cont.) Electrocardiography Infarction (cont.) Electrocardiography Infarction (cont.) Always order right-sided chest leads when there is evidence of an acute inferior wall MI on the standard 12-lead EKG! Electrocardiography Infarction (cont.) Right ventricular infarction is diagnosed by right-sided chest leads: Electrocardiography Putting It All Together When faced with the task of interpreting a 12-lead EKG or a rhythm strip, the best way avoid missing an important finding is to use the same systematic approach every time! Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Basic information Identification Calibration Paper speed, amplitude Technician’s comments Name, age, gender, date “Right-sided chest leads” “Arm leads transposed” “During chest pain” Interpretation Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Basic information Interpretation Rate Rhythm Intervals QRS axis Conduction Atrial abnormality Ventricular hypertrophy Extra or abnormal waves ST segment and T wave changes Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Important: Always compare the EKG that you’re interpreting to that patient’s previous EKGs when possible (especially the most recent previous EKG). Caution: Not all 12-lead EKGs are formatted the same. Don’t confuse “lead change lines” with QRS Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Rate Ventricular Atrial Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Rhythm Regularity QRS complex width P wave polarity in leads II and aVR Explain missing or extra beats Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Intervals PR (normal: 120 – 200 msec) QT (corrected for rate) (normal: 360 - 460 msec) QRS duration (normal: <120 msec) Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) QRS axis Frontal plane Horizontal plane Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Conduction AV Ratio of P waves to QRS complexes PR interval Intraventricular QRS duration QRS pattern Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Atrial abnormality P wave size and shape in leads II and V1 (rhythm must be sinus to use these criteria) Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Ventricular hypertrophy QRS amplitude (if patient’s age > 40 years) QRS axis (for RVH) ST and T changes (ventric. strain pattern) Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) Extra or abnormal waves Delta waves Flutter waves Significant Q waves Prominent or inverted U waves Electrocardiography Putting It All Together (cont.) Systematic approach (cont.) Interpretation (cont.) ST segment and T wave changes ST elevation ST depression ST segment shape T wave inversion T wave shape (including symmetry) T wave size Compare to previous EKGs if available
