INDEX. Kingston General Hospital May Introduction Page 2. Cardiac Conduction System Page 3. Introduction to Cardiac Monitoring Page 5

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2 Kingston General Hospital May 2008 INDEX Introduction Page 2 Cardiac Conduction System Page 3 Introduction to Cardiac Monitoring Page 5 Recording Electrical Events Page 9 Waves of the ECG Complex Page 10 Intervals and Segments Page 16 Rhythm Regularity Page 22 Measurement of Heart Rate Page 23 Systematic Analysis of Rhythm Strips Page 25 Describing Rhythms Page 26 Normal Sinus Rhythm Page 27 Arrhythmias- Patient Assessment Page 28 Arrhythmias originating in the sinus node Page 29 Junctional Rhythms Page 33 Ventricular Rhythms Page 37 Atrial Arrhythmias Page 42 Atrio-ventricular blocks Page 45 Practice Strip Answers Page 52 References Page 56

3 INTRODUCTION The electrocardiogram (ECG or EKG) is a recording of the electrical activity of the heart. The heart has it s own electrical or conduction system. Normally the electrical signals are initiated and travel through the heart s conduction system in a specific order. This is accomplished by a process known as depolarization. The pathway receiving the electrical stimulus is negatively charged (polarized). It must be made positive so that the impulse can be conducted. This process is called depolarization. These cells later recharge or repolarize in preparation for receiving the next electrical impulse. As depolarization and repolarization occur, certain electrical signals are seen on the ECG. This learning guide will help you identify those signals on the ECG. The patient will be hooked up to an ECG monitor that is at the bedside (hardwire), or a battery operated system (telemetry). Telemetry(softwire) is a portable box that is worn by the patient, and the rhythm is displayed centrally at the nursing desk.

4 The heart has both electrical and mechanical properties. The electrical event occurs first followed by the mechanical event. Normal electrical conduction: the cardiac impulse begins in the sinoatrial (SA) node and travels to the right and left atria the atria depolarize and generate the p wave on the electrocardiogram the conduction then travels to the atrioventricular (AV) node where the conduction speed is reduced conduction then speeds up and travels down the Bundles of His, and the right and left bundle branches to the Purkinje fibers the Purkinje fibers distribute the impulse rapidly and uniformly and ultimately depolarize the ventricular myocardium- this generates the QRS wave on the electrocardiogram Mechanical Events: after the P wave is generated the atria contract. This contraction contributes 20% of the blood flow to the ventricle. This is called atrial kick after the QRS wave is generated the ventricles contract the reduction in depolarization speed at the AV node allows time after the atrial mechanical contraction for the ventricles to fill before they contract.

5 CARDIAC CONDUCTION SYSTEM Escape rhythms Automatic Cardiac Tissues There are different conduction tissues in the heart that can act as pacemakers and initiate the electrical sequence. These are: SA node, atrial tissues, AV node, and the ventricles. These tissues each have their own intrinsic or pre-set rate. Normally the SA node initiates the electrical sequence because it has the highest intrinsic rate. If the SA node cannot sustain this rate for some reason, the pacemaker with the next highest rate would then take over as the pacemaker of the heart. This is called an escape rhythm and is the heart s emergency pacing system. It is very uncommon to see an atrial escape rhythm, even though they are the next pacemaker in line. The AV node (junction) is the pacemaker that most often escapes when the SA node fails.

6 INTRODUCTION TO CARDIAC MONITORING The ECG monitor: The patient must be attached to a heart monitor in order to see the electrical signals from the heart. This is done by applying electrodes (sticky sensors) to the patient s skin. Wires attached to a cable are snapped on to the electrodes. The cable is attached to the monitor. A signal will now appear on the monitor. Monitoring Guidelines: 1) Electrodes: prepare skin- shave if required, cleanse with alcohol and abrade skin with backing on electrode electrodes will dry out over time: change if monitor signal is poor or patient is complaining of itchiness underneath electrode use new unopened package of electrodes each time 2) Documentation: 6 second monitor strips are placed on the chart on each shift and when arrhythmias are detected evaluation of the rhythm strip by the nurse is documented with the strip *pt s name and CR number on strip *do not tape over important information- it will fade and disappear over time

7 INTRODUCTION TO CARDIAC MONITORING The electrodes detect the heart s electrical activity. There may be 3 or 5 electrodes attached to your patient. Placement of electrodes: RA-right arm-below right clavicle white LA-below left clavicle black 3 lead 5 lead LL-left leg-left lower rib cage or abdomen red RL-right lower rib cage or abdomen green C- 5 th ICS anterior axillary line brown 3 lead system: RA LA and LL electrodes these electrodes form a triangle around the heart you can choose to monitor leads I, II, or III with a 3 lead system-these are called limb leads 5 lead system: RA LA LL RL C electrodes the C electrode can be positioned in any one of 6 designated positions on the left anterior chest- these are called the V1-V6 positions and are called chest leads the RL electrode is a ground electrode and is not used as a recording electrode with a 5 lead system you can choose to monitor leads I,II,III,aVR,, avl, avf, V1-V6

8 INTRODUCTION TO CARDIAC MONITORING The electrical activity is picked up between 2 electrodes. A different pair is used to record each lead. One electrode is considered negative and one positive. It is the positive one that is recording the electrical activity. Lead 1- uses the RA (neg) and LA (positive) for electrical recording Lead 2 -uses the RA(neg) and LL(positive) for recording Lead 3-uses the LA(now neg) and LL (positive) for recording These limb leads record the electrical conduction of the heart from three different viewpoints. They are called bipolar leads because they use a pair of electrodes to record the activity Remember it is the positive electrode that records the heart s electrical activitythink of the positive electrode like a camera, watching the electrical activity of the heart. The electrical activity of the heart remains the same but each lead views this activity from a different angle.

9 INTRODUCTION TO CARDIAC MONITORING Recording the electrical waves: an upward deflection will be recorded on the monitoring paper if the conduction goes towards the positive electrode a downward deflection will be recorded on the monitoring paper if the conduction goes away from the positive electrode Lead 2- the positive electrode is the LL which is positioned just below the heart normal conduction in the heart is down and to the left, therefore Lead 2 will pick up the conduction (or depolarization) coming towards it -the waves will be recorded as upright on the monitoring paper Lead 2 is the limb lead usually used in monitoring

10 RECORDING ELECTRICAL EVENTS 1 mm.04 sec The recording paper is graph paper which records at a specific speed. The horizontal lines measure the amplitude of events in millimeters or millivolts One horizontal line measures 1 mm The vertical lines measure the duration in seconds of any events. Between 2 vertical lines the measure is.04 of a second. This is called a small box. You ll notice that every 5th vertical line is bolded. This is called a large box and measures.04x5=.20 of a second. The next section discusses what events will be seen on the recording paper.

11 WAVES OF THE ECG COMPLEX The P wave represents the depolarization of the atria. Atrial depolarization begins in the SA node and spreads through both atria. The p wave is small, rounded and usually upright. Atrial repolarization is usually not seen on the ECG because it is hidden in the subsequent QRS waveform and is of low voltage. WAVES OF THE ECG COMPLEX

12 The largest wave in the ECG is the QRS complex. The electrical impulses spreading through the ventricles produce the QRS complex. Therefore the QRS represents ventricular depolarization. Normal QRS duration (interventricular conduction time )is seconds Abnormal QRS duration is >.12 seconds. Indicates that conduction has been delayed in the ventricles Q wave the first downward wave of the QRS complex precedes the R wave often absent on the ECG R wave the first upward wave of the QRS complex an upward wave is always called an R wave a second upward wave is called an R prime ( R ) S wave the downward wave following the R wave An upward wave is always called an R wave The downward wave before the R is called the Q wave The downward wave after the R wave is called the S wave Ventricular contraction following the QRS creates the pulse.

13 WAVES OF THE ECG COMPLEX

14 2 small squares=.08 seconds NORMAL A B A 2 small squares=.08 seconds NORMAL B 3 ½ small squares=.14 seconds WIDE

15 WAVES OF THE ECG COMPLEX Even though we call this complex the QRS complex, not all QRS complexes have all three components. The examples above illustrate different QRS complexes and the names of all the components.

16 WAVES OF THE ECG COMPLEX The T wave represents ventricular repolarization or recovery. The T wave follows the QRS and is smooth and rounded. It is usually upright. Inverted T waves: If a T wave is upside down (inverted) this is usually an abnormal finding. It can indicate myocardial ischemia. Notched or pointed T waves: Heavily notched or sharply pointed T waves in adults may indicate MI or pericarditis. Tall T waves: Tall T waves suggest an MI or hyperkalemia If any of the above are new findings on the monitor a 12 lead ECG should be done

17 PRACTICE YOUR Ps and Qs! QRS QRS QRS QRS T T T T P P P P P QRS QRS QRS QRS QRS QRS T T T T T T P P P P P P

18 INTERVALS AND SEGMENTS This is the segment between the P wave and the QRS. This represents the time interval between when the atria depolarize and when the ventricles depolarize. The electrical impulse is spreading to the AV node, Bundle of His and Purkinje fibers. This is considered a baseline from which we measure changes in the ST segment.

19 INTERVALS AND SEGMENTS The PR interval is measured from the beginning of the P to the beginning of the QRS. If there is no Q wave then it is measured from the beginning of the P wave to the beginning of the R wave. It represents atrial and atrioventricular conduction time. This includes atrial depolarization, the normal conduction delay in the AV node, and the passage of the electrical impulse through the bundle of His and the bundle branches. If conduction is occurring normally then this will take between 0.12 and.20 of a second or 3 to 5 small boxes Short P-R interval: AV conduction time is shortened: could be due to: initial impulse in the junction (AVnode) or another (faster)conduction pathway betweeen atria and ventricles Long P-R interval: AV conduction time is longer than normal: could be due to: a conduction delay in the AV junction a conduction delay through the atria

20 INTERVALS AND SEGMENTS The ST segment is the segment after the QRS and before the T wave. This segment represents ventricular repolarization. Normal ST segment: horizontal and flat level with the PR segment or baseline J point: the junction between the ST segment and the QRS is called the J point If the ST segment is more than 1 mm (1 small square) above the baseline it is considered elevated If the ST segment is more than 1 mm below the baseline for.08 seconds (2 small squares) after the J point, it is considered depressed

21 ST depression: The ST segment falls below the baseline for.08sec (2 small squares) past the J point indicates myocardial ischemia ST elevation: The ST segment is above the baseline acute ST elevation indicates myocardial injury prolonged ST elevation may indicate something other than myocardial injury: pericarditis, ventricular aneurysm or cardiac contusion If any of the above are new findings on the monitor a 12 lead ECG should be done

22 Intervals and Segments The QT interval is measured from the beginning of the QRS until the end of the T wave. The QT interval represents ventricular depolarization and repolarization. Normal QT interval: usually between 0.36 and 0.44 second varies greatly according to age, gender,heart rate, and whether the patient is asleep should be less than 1/2 the distance between two consecutive R waves (R-R interval) when the rhythm is regular Prolonged QT interval: Repolarization means that the muscle cell resets itself so it can depolarize again. Measured on an ECG, the time between the Q wave and the T wave is prolonged in this condition. This leads to a longer vulnerable period. If the next QRS begins before the end of repolarization, an arrhythmia or irregular heart beat could occur, such as ventricular fibrillation, or Torsades de Pointes which could be fatal. This condition is diagnosed on a 12 lead ECG. A 12 lead ECG should be done if the QT appears prolonged Cause:congenital, medications (Amiodarone, Haldol, Procainamide,Sotalol, some antibiotics ), hypokalemia and hypomagnesemia, intracranial or subarachnoid hemorrhage Intervals and Segments

23 PR ST QT J point PR=.16 sec NORMAL ST-depressed 1mm for.08 sec past the J point-abnormal QT- less than ½ the R-R NORMAL PR=.32 sec PROLONGED ST- slightly depressed, but not 1mm- baseline-normal QT- less than ½ the R-R NORMAL PR ST QT PR=.20 seconds NORMAL ST- baseline-normal QT- more than ½ the R-R PROLONGED PR ST QT

24 RHYTHM REGULARITY Rhythm Regularity: Refers to the regularity of the QRS complexes Measure the distance between the QRS complexes-this is referred to as the R-R interval There are three ways to describe regularity: Regular rhythms R-R intervals are all the same or vary slightly. In regular rhythms the QRSs usually look alike Regular but interrupted Most of the R-R intervals are constant Interrupted by premature beats or a pause Irregular R-R intervals vary Not due to premature beats or pauses, but because the actual rhythm is irregular

25 MEASUREMENT OF HEART RATE 6 seconds 3 seconds SECOND METHOD To determine HR: There are small line markers on the top of the graph paper These occur every 3 seconds Count # of QRS complexes in a 6 second strip. Multiply by 10. Above example: QRS s in 6 seconds = 6 6 X 10 = 60 beats/min

26 MEASUREMENT OF HEART RATE How to calculate the heart rate on ECG paper big box BIG BOX METHOD Alternate method to determine HR (for regular rhythms only) There are 300 big boxes in one minute If there was one big box between each QRS the HR would be 300 / minute If there were 2 big boxes between each QRS the HR would be 300/2= 150/min Try to find a QRS on a bolded line Count the number of big boxes to the next QRS Divide into 300

27 SYSTEMATIC ANALYSIS OF RHYTHM STRIPS The key to identifying rhythms correctly is to systematically analyze the cardiac rhythm strip. 1. Determine the atrial and ventricular rate (HR) If these rates are different then you know to look more closely a the relationship between the p and the QRS 2. Measure R-R. a. Is the rhythm regular, regular but interrupted, or irregular? 3. P waves a. Are they present and do they all look the same? b. Is there a QRS after each one? 4. PR interval a. Normal is seconds (3-5 small boxes) b. Is each PR interval the same? 5. QRS duration a. Normal is <.12 seconds or 3 small boxes b. Are they all the same and point in the same direction? 6. Examine the ST segment a. Is it at baseline (even with the PR segment) b. Is there ST elevation or ST depression? 7. Examine the T waves a. Normal is upright and rounded b. Are they inverted or flattened 8. Measure the QT interval a. Normal is < ½ the R-R interval b. Is it changed from previously 9. Are there premature beats.

28 a. Is there a p in front of the QRS? b. Is the QRS normal or widened? 10. Analyze the rhythm. Rhythms are always described by the above format. The first part of the description tells us where the rhythm originates. The second part of the description tells us how fast the rhythm is. Examples: Sinus bradycardia: The rhythm originates in the sinus node and the rate is < 60 beats per minute Ventricular tachycardia: The rhythm originates in the ventricles and the rate is > 100 beats per minute

29 NORMAL SINUS RHYTHM Normal Sinus Rhythm Sinoatrial node Rhythm Regular Rate (per minute) P wave Upright PRI QRS Uniform The only rhythm that is considered normal is normal sinus rhythm. Mechanical events are optimal in normal sinus rhythm. An arrhythmia is any cardiac rhythm that is not normal sinus rhythm. Arrhythmias fall into the following categories: Arrhythmias originating in the sinus node Junctional rhythms Ventricular rhythms Atrial arrhythmias AV conduction disturbances

30 ARRYTHMIAS- PATIENT ASSESSMENT Arrhythmias can occur for a number of reasons. If the patient is symptomatic, then there must be immediate intervention Guide your nursing assessment with the following questions: 1. Is the patient oxygenating well? a. Check the O 2 saturation 2. Is there evidence of ischemia? b. Is the patient having chest pain? c. Check for high blood pressure. d. Assess for heart failure. 3. Are the electrolytes abnormal? a. Check the potassium, magnesium and calcium levels 4. What medications is the patient on? a. Check for medications that can cause bradycardia b. Check for medications that can cause prolonged QT intervals and may precipitate tachycardia

31 Arrhythmias Originating in the Sinus Node Sinus Tachycardia Sinus Bradycardia Sinus Arrhythmia Sinoatrial (SA) Block Sinus Arrest Sick Sinus Syndrome

32 Sinus Tachycardia Sinoatrial node Rhythm Rate P Wave PRI QRS (per minute) Regular Upright Uniform Causes Exercise, anxiety, fever, pain, hyperthyroidism, medications Nursing Implications Treat the cause

33 Sinus Bradycardia Sinoatrial node Rhythm Regular Rate (per minute) P Wave Upright Uniform PRI QRS Causes Sleep, athletic heart, increased vagal tone, beta-adrenergic blockade Nursing Implications Treat if there is hemodynamic compromise

34 Sinus Arrhythmia Sinoatrial node Rhythm Rate P Wave PR Interval QRS (per minute) Irregular Usually Upright Uniform irregular rhythm associated with respiratory cycles; HR á with inspiration & HR âwith expiration

35 Sinoatrial (SA) Block Rhythm Rate P Wave PRI QRS (per minute) Regular but interrupted Usually Upright, uniform but entire cycle missing <0.12 Causes Coronary artery disease, medications, carotid sinus sensitivity and increased vagal tone Nursing Implications Treat if the pauses are long and there is hemodynamic compromise

36 Sinus Arrest Escape rhythm Rhythm Rate P Wave PRI QRS (per minute) Regular but interrupted Any rate No sinus P s N/A <0.12 (junctional) >0.12 (ventricular) Causes Coronary artery disease, medications, carotid sinus sensitivity and increased vagal tone Nursing Implications Treat if the pauses are long and there is hemodynamic compromise

37 Sick Sinus Syndrome A cluster of symptoms arising from a pathology in the sinus node. Results in dramatic changes in heart rate -bradycardia " tachycardia, interspersed with sinus arrests, pauses and blocks. Escape beats common after long sinus pauses. Rhythm Rate (per minute) P Wave PRI QRS Irregular Varies wildly Too fast too slow May or may not be present, shape varies If present, varies Varies See answers beginning on page 52 Causes Ischemic disease, medication, inflammatory disease, surgical injury, idiopathic Nursing Implications Treat underlying cause (digoxin, beta blockers), pacemaker

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39 Junctional Rhythms Junctional Rhythm Premature Junctional Contraction Accelerated Junctional Rhythm Junctional Tachycardia Junctional Escape Rhythm Junctional Rhythm AV node 2 nd 1 st Simultaneous Atrium depolarized 1 st, then ventricles. Upside down P wave BEFORE QRS Atria & ventricles depolarized simultaneously. NO visible P wave, obscured by QRS Ventricles depolarized 1 st, then atria. Upside down P wave AFTER QRS

40 Premature Junctional Contractions (PJC) Rhythm Rate (per minute) P Wave PRI QRS Regular but interrupted Occurs at any rate Inverted before or after QRS or not visible <0.12 if P precedes QRS <0.12 Causes MI, Digoxin toxicity, hypoxia, stimulants Nursing Implications Remove the cause eg. Digoxin toxicity Junctional Rhythm AV node Rhythm Regular Rate (per minute) P Wave If visible, inverted (before or after QRS) PRI If able to measure <0.12 Causes MI, Digoxin toxicity, Hypoxia, vagal stimulation Nursing Implications If symptomatic- atropine. Treat the cause eg. Digoxin toxicity QRS <0.12

41 Accelerated Junctional AV node Rhythm Regular Rate (per minute) P Wave If visible, inverted (before or after QRS) Causes MI, stimulant drugs, caffeine, dig toxicity Nursing Implications Remove the cause PRI If able to measure <0.12 QRS <0.12 Junctional Tachycardia Rhythm Rate (per minute) P Wave PRI QRS Regular >100 If visible, inverted (before or after QRS) If able to measure <0.12 Causes Digoxin toxicity, heart disease, stimulants Nursing Implications Identify and treat the cause eg. Digoxin toxicity <0.12

42 Junctional Escape Rhythm Rhythm Regular Irregular Rate (per minute) P Wave If present inverted before or after QRS PRI Causes MI, Digoxin toxicity Nursing Implications Identify and treat the cause eg. Digoxin toxicity <0.12 QRS <0.12

43 See answers beginning on page 52

44 Ventricular Arrhythmias Premature Ventricular Contraction (PVC) Accelerated (Idio)ventricular rhythm Ventricular Tachycardia Ventricular Fibrillation Ventricular Escape Rhythm Bundle Branch Blocks

45 Premature Ventricular Contraction Rhythm Rate (per minute) P Wave PRI QRS T wave Regular but interrupted by PVC s Occurs at any rate Not seen on PVC s N/A >0.12 In opposite direction of QRS Causes Heart disease, hypokalemia, hypoxia, hypomagnesemia, stimulants, caffeine, stress, anxiety,digoxin, significant anemia Nursing Implications Assess frequency of PVC s and potential cause(s).

46 Bigeminy Multifocal PVC s Accelerated Ventricular Rhythm Rhythm Rate (per minute) P Wave PR Interval QRS Usually regular Causes Usually not seen Common after MI, administration of fibrinolytics Nursing Implications Not measureable Usually well tolerated. This is the patient s escape rhythm, so antiarrhythmics are not used >0.12

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48 Ventricular Fibrillation (VF) Rhythm Rate (per minute) P Wave PR Interval QRS Not detectable Can t be counted None Causes Significant underlying cardiac disease, AMI, hypokalemia, hypoxia, hypomagnesemia, drugs Nursing Implications Code Blue- defibrillation Not detectable Not detectable

49 Ventricular Escape Rhythm Rhythm Rate P Wave PR Interval QRS (per minute) Usually regular Usually not seen Not measureable >0.12 Causes Massive MI, hypoxia Nursing Implications Usually pulseless- CODE BLUE, CPR

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52 Atrial Arrhythmias Premature Atrial Contractions (PAC) Atrial Tachycardia Atrial Flutter Atrial Fibrillation Premature Atrial Contractions Rhythm Interrupted by PAC Rate (per minute) Varies P Wave P of PAC different from underlying rhythm P s PRI Differs from underlying rhythm Causes Electrolyte imbalance, stress, hypoxia, digoxin toxicity Nursing Implications Check electrolytes, O 2 saturation. Remove the cause. QRS <0.12

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54 Atrial Fibrillation Rhythm Rate P Wave PRI QRS (per minute) Irregular A: V: slow to rapid Fibrillatory (fine to coarse) N/A <0.12 Causes- Valvular HD,MI, thyrotoxicosis, lung disease Nursing Implications Assess BP as patient has lost atrial kick. Lack of co-ordinated contraction in the atria predisposes patients to embolic events- anticoagulation required Acute-cardiovert or control rate with beta blockers, calcium channel blockers >48 hours- anticoagulation required x 3 weeks prior to cardioversion

55 See answers beginning on page 52

56 Heart Blocks 1. What is heart block? Heart block is an arrhythmia usually caused by ischemia or an MI. It can also be caused by drugs such as beta blockers, calcium channel blockers, digoxin or any drug trying to slow down a fast rhythm and overshoots the mark! 2. What is being blocked in a heart block? The signal from the SA node is trying to get through to the AV node (creating a p wave) and then to the ventricle (creating a QRS). In heart block the signal from the SA node through the AV node is either slowed down (causing a longer P-R interval) or blocked altogether, so there is a p wave but no QRS.is triggered by the p wave. The key to heart blocks: The signal is getting through: 1 all of the time (but taking longer than normal-.20 sec) 2 some of the time 3 none of the time These are called first degree (#1), second degree (#2)and third degree (#3) heart blocks.

57 3. What are the three types or degree of heart block? Look at a normal sinus rhythm: PR interval You can see the p waves and you can see where the QRS begins- the measurement from the beginning of the P to the beginning of the QRS is the PR interval. A normal P- R interval should be no longer than.20 seconds or one big box on the EKG paper. The PR interval represents the electrical depolarization from the SA node through the atria and the AV node. If the PR interval is normal then the signal is taking the normal amount of time to travel this far. The signal should then travel to the ventricles to create a QRS. 3.1 First degree heart block: Measure the PR interval. You will notice that it is longer than.20 seconds or one big block. It is taking longer than normal time to get from the SA node through the AV node to the ventricles. It does get to the ventricles all the time. This is SR with a first degree heart block. 3.2 Second degree heart blocks: By definition a second degree heart block has signals getting through some of the time. So you will see p s with QRS s after them and you will see p s without QRS s after them.

58 The SA node will fire at a constant rate- some of the time the signal gets through the AV node to the ventricle and sometimes it doesn t.. There are 2 kinds of second degree heart block: The first kind can be called one of two names: Type 1 second degree or Wenckebach Second degree type 1-Wenckebach You can see the p waves without a QRS. The signal is getting through the AV node some of the time. Look at the PR intervals before the dropped beat- the PR starts out normal, then gets longer with the next beat, longer with the subsequent beat and then doesn t get through. So the PRs leading up to the dropped beat get longer and longer then drop. The heart rate in this patient is still 70 bpm, so the patient probably has a good blood pressure. Usually this rhythm is benign and is transient due to a MI. However it still bears watching Second degree type 2

59 degree type 1- PRs- longer,longer, longer and drop degree type 2-PRs- all the same and then drop a QRS without warning Predictable Unpredictable You can see the p s without the QRS. The other Ps are followed by a QRS and all the PRs are the same. The signal is getting through to the AV node some of the time. therefore it is a second degree heart block. The PRs of the other beats are all the same. This heart block is much more serious and can progress to third degree heart block (complete heart block). This patient requires a pacemaker. 3.3 Third degree heart block (complete) Third Degree Heart Block In third degree heart block the SA node is firing a signal at a regular rate. The top arrows show where the p s are. However the signal is not getting through the AV node to create a QRS. When this happens either the AV node or the ventricle will generate a rate by themselves. If the AV node generates it the QRS will be narrow. If the ventricle generates it the QRS will be wide. The QRS is marked by the arrows at the bottom. If you measure the PR intervals, none of them are the same. There are p s in the middle of QRS s. This tells you that there is no connection between the p and the QRS. The SA node and the ventricle are depolarizing independently of each other. None of the p waves are conducted through the AV node to the ventricle. This heart block is serious as the ventricular rate can go as low as 20 or stop altogether. This patient requires a pacemaker.

60 AV Blocks 1 p for every QRS Constant Prolonged P-R Interval 1 0 AV block NO Regular R-R? More p s than QRS P-R constant? YES 2 0 type 2 AV block Includes 2:1 AV conduction YES NO Diagram: AV blocks 3 0 AV block (complete) 2 on 0 AV the block right type 1 side (Wenckebach) of the diagram are the most serious and equire a permanent pacemaker. AV blocks on the left side are less serious, QRS normal width? ransient, or the causes can be reversed. NO YES Ventricular escape Junctional escape Atrioventricular (AV) Conduction Disturbances First Degree AV Block Second Degree AV Block Type I (Wenckebach) Type II Third Degree (Complete) AV Block

61 First Degree AV Block Rhythm Rate P Wave PR Interval QRS (per minute) Depends on underlying rhythm Can occur at any rate upright Uniform Precede QRS Prolonged > 0.20 < 0.12 Causes AV node ischemia,dig toxicity,drugs (beta blockers, calcium channel blockers), ablation Nursing Implications Remove the cause. Treat the cause 2 nd Degree Heart Block Type I - Wenckebach Rhythm Rate P Wave PRI QRS (per minute) Usually irregular Atrial usually Ventricular < atrial Sinus P s Gradually # s until QRS dropped <0.12 if block at AV >0.12 if block at bundle branches Causes- Drugs, MI, chronic degenerative conduction disease. Nursing Implications Usually due to MI, is transient and only requires observation If symptomatic- atropine, pacemaker

62 2 nd Degree Heart Block Type II Rhythm Regular Or Irregular Rate (per minute) Atrial usually Ventricular < atrial P Wave Sinus P s 2 or > before each QRS PRI Constant for conducted beats QRS <0.12 if block at AV >0.12 if block at bundle branches Causes- Drugs, MI, chronic degenerative conduction disease, hypoxia Nursing Implications Definitive treatment is a pacemaker as this can progress to complete AV block or asystole.. Atropine can be tried for symptoms, but may paradoxically slow the heart rate. Third Degree AV Block Rhythm Rate (per minute) P Wave PRI QRS Regular Atrial Ventricular Block at AV Block at bundle branches Sinus P s with no relation to QRS varies Block at AV <0.12 Block at bundle branches >0.12 Causes- Drugs, MI, chronic degenerative conduction disease, hypoxia Nursing Implications Definitive treatment is a pacemaker. Atropine can be tried for symptoms, but may paradoxically slow the heart rate.

63 See answers beginning on page 52

64 Rate: Atrial 40 Ventricular 40 Regular? Yes P waves _Yes-all the same Followed by QRS? Yes PRI 0.16 QRS 0.08 ST segment baseline T wave upright QT Interval less than ½ the R-R interval PRACTICE STRIP ANSWERS Interpretation sinus bradycardia Practice Strips page 32 Rate: Atrial 70 Ventricular 70 Regular? No- slows down and speeds up P waves Yes-all the same Followed by QRS? Yes PRI 0.14 QRS_0.08 ST segment depressed T wave upright QT Interval 1/2 the R-R interval Interpretation Sinus arrhythmia

65 Rate: Rate: Atrial Atrial none none Ventricular Ventricular Regular? yes Regular? yes P waves P waves none Followed no Followed by QRS?_no by QRS? no_ PRI PRI _none none QRS 0.06 QRS 0.20_(wide)_ ST segment ST segment lightly can t depressed measure T wave upright T wave can see QT Interval QT Interval less can t than ½ measure the R-R interval Practice Strips Page 36 Iterpretation junctional Interpretation ventricular rhythm tachycardia Practice Strips page 41

66 Rate: Atrial 300 Ventricular 80 Regular? No P waves f waves Followed by QRS? sometimes PRI _not measured QRS 0.10 ST segment hard to tell T wave can t see Practice Strips page 44 QT Interval can t measure Interpretation atrial flutter with variable conduction from A to V 3 second arrows show f waves hidden in the QRS

67 Rate: Atrial no p Ventricular 90 Regular? irregular P waves _no Followed by QRS?_no PRI none QRS 0.08 ST segment hard to tell- could be depressed T wave _upright QT Interval 0.28 normal Interpretation atrial fibrillation with controlled ventricular response (less than 100/ minute) QT interval

68 Rate: Atrial 80 Ventricular 60 Regular? No P waves _yes-all the same Followed by QRS?_not all PRI _ prolonging QRS 0.06 ST segment baseline T wave upright Practice Strips page 51 QT Interval 0.36 normal Interpretation second degree type 1 AV block (Wenckeback) Arrows indicate p waves hidden in the complex REFERENCES Rate: Atrial 80 Ventricular 30 Regular? yes P waves upright Followed by QRS?_no PRI all different QRS 0.16_(wide) ST segment depressed T wave inverted QT Interval 0.28 normal Interpretation 3 rd degree AV block

69 References 1. Daly, S., Weinstein E., Ambrose, M., Charnow, J., (eds) et al. (1993) Deciphering Difficult ECG s. Pennsylvania: Springhouse Corporation. 2. Dubin, D. (2000) Rapid Interpretation of EKG s. 6th edition. Florida: COVER Publishing Company. 3. Ellis, Karen (2002) EKG Plain and Simple. New Jersey: Prentice Hall. 4. Hudak, C., Gallo B., Gonce Morton, P.,(1998) Critical Care Nursing: A Holistic Approach. 7th edition. New York: Lippincott. 4. Stein, E. (1997) Clinical Electrocardiography: A Self Study Course. Philadelphia: Lea & Febiger. 5. Vinsant, M., Spence, M. (1989) Commonsense Approach to Coronary Care: A Program: 5th edition. Toronto: The C.V Mosby Company. 6. Woods, S., Sivarajan Froeclicher,E., Underhill Motzer, S. (2000) Cardiac Nursing. 4th edition. New York: Lippincott.

70 TEST Please check with your CE to see which test is appropriate for you to complete Please evaluate the following strips in a systematic way. Describe the dysrhythmia by the predominant underlying rhythm and then any other rhythm or extra beats that are on the strip. e.g.- SR with PVC s or SR with first degree HB Filling out the test completely should lead you to an accurate interpretation Thank you

71 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

72 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself -Are the premature QRSs wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2

73 Mark /10 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Marks Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

74 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Marks Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

75 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

76 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

77 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

78 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

79 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

80 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

81 Marks 1. What is the ventricular rate? Is it regular? Are there any premature QRS s? Ask yourself- Are the premature QRS s wide or narrow? 2. P waves What is the rate? Are the each followed by a QRS? 3. What is the P-R interval? Is it constant? If not constant what is happening to the P-R? 4. What is the QRS duration? Is this a normal QRS duration? Ask yourself: Could there be a hidden p wave in the ST segment or T wave? Identify the conduction pathway for this rhythm on the following diagram 1 6. State the rhythm diagnosis 2 Mark /10

82 Test # 2 Please check with your CE to see which test is appropriate for you Please evaluate the following strips in a systematic way. Describe the dysrhythmia by the predominant underlying rhythm and then any other rhythm or extra beats that are on the strip. e.g.- Normal Sinus rhythm with Premature Ventricular Contractions (NSR with PVCs) or Normal Sinus Rhythm (NSR) with first degree Heart Block (HB) For test purposes each rhythm strip will be assumed to be a 6 second strip. as Identify the normal PR interval as and abnormal as > 0.20 in the learning guide Identify the normal QRS interval as and abnormal as > 0.10 as in the learning guide Filling out the test completely should lead you to an accurate interpretation. Each test strip will be marked out of 5 for a total score out of 25. Thank you

83 Strip #1 2. a) What is the ventricular rate? a) Is it regular? 2. P waves a) What is the rate? b) Is each P wave followed by a QRS? 3. a) What is the P-R interval? b) Is it constant? 7. a) What is the QRS duration? b) Is this a normal QRS duration? 8. State the rhythm diagnosis.

84 Strip #2 1. a) What is the ventricular rate? b) Is it regular? 3. P waves a) What is the rate? 3. a) What is the P-R interval? 7. a) What is the QRS duration? 8. State the rhythm diagnosis.

85 Strip #3 1. a) What is the ventricular rate? b) Is it regular? 2. P waves a) What is the rate? 3. a) What is the P-R interval? 7. a) What is the QRS duration? b) Is this a normal QRS duration? 8. State the rhythm diagnosis.

86 Strip #4 1. a) What is the ventricular rate? b) Is it regular? 2. P waves a) What is the rate? b) Are they each followed by a QRS? 3. a) What is the P-R interval? 7. a) What is the QRS duration? b) Is this a normal QRS duration? 8. State the rhythm diagnosis.

87 Strip #5 1. a) What is the ventricular rate? b) Is it regular? c) Are there any premature QRS s? P waves a) What is the rate? 3. a) What is the P-R interval? b) Is it constant? 7. a) What is the QRS duration? 8. State the rhythm diagnosis.