ECG and Arrhythmias Dec, 1 st 2014 Doctor Mohammad Jarrah References: - Lecture and Slides - ECG Made Easy - Davidson Principles of Medicine - First Aid Cases for the USMLE Step 1 - Mini-OSCE Archive ECG stands for electrocardiogram; it s a record of the heart s electrical activity. it s a very important tool that can provide evidences to support a specific diagnosis. Remember that most abnormalities in the ECG are amenable to reason. The Basics: The quality of an ECG is determined by the presence of PATIENT S NAME, DATE/TIME, the 12 LEADS and a RYTHEM STRIP at the bottom. The paper moves in a speed of 25mm/s (horizontal).?if faster (50mm/s) it ll give a false impression of slow HR And a caliberation of 1cm or 10mm/mV (vertical).?if >1mm/mv gives a false impression of Left Ventriuclar Hypertrophy 1 small square (Ssq) = 1 mm, 1 large square (Lsq) = 5 Ssq = 5 mm. P: Atria Depolarization (<2.5 mm vertical) QRS: Ventricular Depolarization T: Ventricular Repolarization U: Repolarization of the papillary muscles follows the T wave. (Normal or Abnormal) PR interval: 120-220 ms (3-5 small squares) >220: Block, <120: accessory pathway QRS complex: 120 ms (3 small squares) 1 min = 60 sec = 60* (5 large squares) = 300 large square Heart Rate= 300 (Lsq)/ R-R interval = 1500 (Ssq)/ R-R interval = # of R per 15 (Lsq) * 20 = (60-100 bpm) normally. Rhythm: - Sinus rhythm if each QRS is preceded by P - Regular rhythm if the distance between the R is constant. 1
Normal ECG Positive deflection: If a wave of depolarization passing through the heart is moving toward a surface electrode Negative deflection: If a wave of depolarization passing through the heart is moving away from the electrode. Biphasic wave: If a wave of depolarization passing through the heart is moving perpendicularly to the electrode. The 12-Lead ECG 6 limb leads: I between right arm and left arm. II between right arm and left leg. III between left arm and left leg. avr: right arm, avl: left arm, avf: left leg I, II, avl: Left lateral surface. III, avf: Inferior surface. avr: Right surface. In a normal cardiac axis (about 60 degrees): Lead II and avf have the highest positive deflection. I and II are normally both positively deflected. Lead II is usually the long rhythm strip, with the most obvious P wave. 2
6 chest leads: V1 and V2: Parasternal at 4 th intercostals space. V3 is in between V2 and V4. V4, V5 and V6 at the 5 th intercostal space: V4: Midclavicular line V5: Anterior axillary line V6: Middle axillary line. V1, V2, V3, V4: Anteriospetal surface. V5,V6: Lateral surface In a normal cardiac axis (about 60 degrees): - V1: Small R, Deep S - V2: R increases, S decreases - V3/V4: R=S - V5/V6: Large R, S disappears in normal people If the R is poorly enlarging (poor progression R wave sign of ischemia) The Cardiac Axis: Normally, between -30 and +90 Right Axis Deviation/RAD (>+90): Right ventricular hypertrophy Left Axis Deviation/LAD (<-30): Left ventricular hypertrophy, LBBB. Indeterminate Axis (No Man s Land): extreme LAD or extreme RAD, Dextrocardia. -ve Lead I +ve Lead II +ve Lead I -ve Lead II -ve Lead I, II & III 3
Normal ECG Record: 12 leads with a rhythm strip (II) Good Voltage (2 Lsq or 1cm vertical) HR = 300/5 = 60 bpm Regular Sinus Rhythm: P wave precedes each QRS with good relation between them PR interval is between 3-5 Ssq, P voltage is less than 2.5 Ssq QRS complex is less than 3 Ssq QT isn t prolonged (<450 ms) Normal axis (+ve lead I,II and III) Negative T wave in V1 is normal V1 V6: R increases and S decreases (disappears in V6) 4
ECG Record with some abnormalities: 12 leads with a rhythm strip (II) Good Voltage (2 Lsq or 1cm vertical) HR > 60 bpm Regular Sinus Rhythm: P wave precedes each QRS with good relation between them PR interval is between 3-5 Ssq, P voltage is less than 2.5 Ssq QRS complex is slightly widened is some leads Left axis deviation (+ve Lead I and ve Lead II) Poor progression R wave Ischemia S wave in V6? Abnormality The abnormally looking complex in avf is just an artefact (not significant) Abnormalities due to machine or human error: Paper speed 12.5 mm/s false rapid heart rate Patient is shivering Remember: ECG must be individualized: Male vs Female, Old vs Young, Chest Pain vs Normal 5
The Abnormalities of the waves, complexes and intervals: Absence P Pulmonale: Pointy; >2.5 Ssq vertical in Lead II P wave abnormalities Not Sinus Right Atrial dilatation/hypertrophy due to cor pulmonale/copd/... P Mitral: Bifid in Lead II Left Atrial dilatation/hypertrophy due to Mitral stenosis (MS) or sometimes MR Too short (<3 Ssq) Too long (>1Lsq) PR Interval Abnormalities - Wolf Parkinson White syndrome (WPW): accessory pathway associated with Delta wave. - Could be normal in rapid heart rate. Heart block/av block (1 st, 2 nd and 3 rd degrees) Spot on Arrhythmias: Preexcitation syndromes (WPW Syndrome): Preexcitation is a condition characterized by an accessory pathway of conduction, which allows the heart to depolarize in an atypical sequence. In Wolfe-Parkinson-White (WPW) syndrome, there s a direct atrioventricular connection allows the ventricles to begin depolarization while the standard action potential is still traveling through the AV node. ECG Characteristics of WPW: 1. Short PR interval 2. QRS prolongation 3. Delta Wave 4. Followed by tachycardia 6
In fact, the PR interval isn t shortened, but it looks so due to the emergence of the delta wave. Heart Block (AV block): 1 st degree Heart block: - Prolongation of the PR interval, which is constant - All P waves are conducted 2 nd degree Heart block (Mobitz 1)/Wenckebach: - Progressive prolongation of the PR interval until a P wave is not conducted. - As the PR interval prolongs, the RR interval actually shortens 2 nd degree Heart block (Mobitz 2): Constant PR interval with intermittent failure to conduct Third degree Heart block (Complete): No relationship between P waves and QRS complexes, Relatively constant PP intervals and RR intervals and Greater number of P waves than QRS complexes 7
QRS complex Abnormalities Generally, if QRS > 0.12 ms Bundle Branch Block (Rt vs Lt) Accepted Q waves: V1, avr and III Pathological Q waves: >25% of subsequent complex and unusual location on leads previous infarction. Sum of the S wave (-ve deflection) in V1 and the biggest R wave in V5 or V6 >35mm (> 5Lsq) Left Ventricular Hypertrophy (LVH) If LVH is presented with ST depression and T inversion on the left leads indicates LVH induced infarction (blood supply isn t enough for the hypertrophied muscle tissue (LVH with Strain) LVH with Strain, Normal sinus rhythm 8
Spot on LBBB and RBBB: Common causes ECG changes Appearance RBBB - Normal variant - Right ventricular hypertrophy or strain - ASD QRS > 3 Ssq RSR (M shaped QRS complex) in V1, V2 and deep S in V6. - May present with RAD (usually) or LAD (Atrial septal defect, severe conducting problem) LBBB - CAD - HTN - Aortic valve disease - Cardiomyopathy QRS > 3 Ssq RSR (M shaped QRS complex) in V5, V6, I and deep S in V1 - Usually associated with LAD Mnemonic MaRRoW: M first letter = M in V1 WiLLiaM: M last letter = M in V6 RBBB with LAD: Bifascicular rhythm s 9
ST segment Abnormalities These are usually in territories eg. anterior/lateral/inferior etc. and will be present in contiguous leads (III,aVF or I,aVL,V5,V6...) ST depression: - Downsloping or horizontal = abnormal - Ischaemia (coronary stenosis): Chest pain association - If lateral (V4-V6), consider LVH with strain or digoxin toxicity ST elevation - Infarction (coronary occlusion) - Pericarditis (widespread) - Prinzmetal spasm - Post ventricular aneurysm - Early embolization Normal rhythm (P wave in II) and axis, ST elevation is V2-V6, and minimally in avl, Q wave also present: Acute MI in the proximal Left Anterior Descending Artery. 10
Sinus rhythm ST depression Lead I, avl, ST elevation V5, V6 Lateral MI (acute over chronic) ST elevation in III and avf Inferior MI reciprocal ST depression in V1, V2 Posterior MI InferioPosterioLateral MI Super-dominant Right coronary artery, proximal occlusion. ask for Right ventricular leads Right Ventricular Infarction Cardiogenic Shock Hypotension IV fluids Pericarditis: Sinus tachycardia with Diffuse ST elevation in all leads except: V1: Normal or depression, avr: ST depression 11
T wave Abnormalities Peaked hyperkalaemia or normal young man Inverted/biphasic ischaemia, previous infarct Small hypokalaemia What is the rate, rhythm and axis for these patients, and is there any other abnormalities? Not sinus (ectopic) and irregular rhythm, rate = 120, right axis deviation?, LVH due to deep S and huge R, T inversion can be seen laterally. LVH Right atrial abnormality and fibrillation P wave present, Sinus tachycardia and LVH (what s the rate?) 12
P wave present, Sinus bradychardia (what s the rate?) Recall that the NORMAL SINUS RHYTHM shows Regular narrow-complex rhythm Rate 60-100 bpm, Each QRS complex is proceeded by a P wave P wave is upright in lead II & downgoing in lead avr Bradycardia, and obvious delta wave in V1 WPW Syndrome ST elevation in inferior leads and No relation between P and QRS complete Heart Block 13
QT interval must be corrected because it s affected by the HR: QT interval Abnormalities Long QT (>450ms) can be genetic (long QT syndrome) or secondary due to drugs (amiodarone, sotalol) Associated with risk of sudden death due to Torsades de Pointes (check page 16) Atrial and Ventricular Arrythmias? Supraventricular means SA, AV or Atrial origin. Most Important Arrythmias to be familiar with: SVT (Supraventricular Tachycardia): Narrow QRS, Rate >150, regular RR complexes, P wave may be superimposed on T wave or hidden inside the QRS complex: Atrial Flutter: Biphasic sawtooth flutter waves at a rate of >250/min Flutter waves have constant amplitude, duration, and morphology through the cardiac cycle. There is usually either a 2:1 or 4:1 block at the AV node, resulting in ventricular rates of either 150 or 75 bpm Adenosine is used to unmask an unclear record (SVT or Flutter?) by showing the saw-tooth appearance. 14
Atrial Fibrillation Atrial fibrillation is caused by numerous wavelets of depolarization spreading throughout the atria simultaneously, leading to an absence of coordinated atrial contraction. AF is important because it can lead to: Hemodynamic compromise, Systemic embolization and other Symptoms On ECG: Absent P waves, Presence of fine fibrillatory waves which vary in amplitude and morphology, Irregularly irregular ventricular response. Ventricular Tachychardia: (usually follows MI) - Broad bizzare QRS complex - Regular RR waves - Rate >120 (less than the SVT) - P waves are present, fused with T or on top of ascending QRS complexes - Treat with lignocaine or DC shock. Some times a normal QRS is present within the tachycardia: Capture beat. 15
Torsade de Pointe: usually with prolonged QT interval The QRS complexes spin around the baseline, changing their axis and amplitude Ectopic Beats Abnormal early beat whether atrial or ventricular within a normal ECG In ventricular extrasystole/ectopic beat : QRS would look broad and bizarre, not preceeded by P and followed by opposing ST-T changes and by a compnesatory pause. In Atrial extrasystole/ectopic beat: QRS would look normal, abnormally looking P wave and with a compnesatory pause. Unknown Arrhythmia (not discussed)? 1. Is the rate slow (<60 bpm) or fast (>100 bpm)? Slow Suggests sinus bradycardia, sinus arrest, or conduction block Fast Suggets increased/abnormal automaticity or reentry 16
2. Is the rhythm irregular? Irregular Suggests atrial fibrillation, 2 nd degree AV block, multifocal atrial tachycardia, or atrial flutter with variable AV block 3. Is the QRS complex narrow or wide? Narrow Rhythm must originate from the AV node or above Wide Rhythm may originate from anywhere 4. Are there P waves? Absent P waves Suggests atrial fibrillation, ventricular tachycardia, or rhythms originating from the AV node 5. What is the relationship between the P waves and QRS complexes? More P waves than QRS complexes Suggests 2 nd or 3 rd degree AV block More QRS complexes than P waves Suggests an accelerated junctional or ventricular rhythm 6. Is the onset/termination of the rhythm abrupt or gradual? Abrupt Suggests reentrant rhythm Gradual Suggests altered automaticity When the variations in PP interval occur in phase with respiration, this is considered to be a normal variant, called sinus arrhythmia: What is the Sick Sinus Syndrome (SSS)? Characterized by a collection of symptoms and ECG findings due to chronic dysfunction of the sinoatrial (SA) node: Chronic and severe sinus bradycardia 17
Sinus pauses Sinus arrhythmia Complete sinus arrest Progressive development of atrial arrhythmias (a-flutter, a-fib, atrial tachycardia) Patients are usually elderly and present with lightheadedness and/or syncope, but it can also manifest as angina, dyspnea, and palpitations. Tachycardia-Bradycharida Variant: (needs pacemaker and medication for the AV) Etiologies: Sinus node firbosis, Atherosclerosis of the SA artery, Congenital heart disease, Excessive vagal tone, Familial, Pericarditis, Hypothyrodism. Multifocal Atrial Tachycardia: Discrete P waves with at least 3 different morphologies. Atrial rate > 100 bpm. The PP, PR, and RR intervals all vary. It s very common with COPD and Lung fibrosis patients. 18
Abnormalities due to electrolyte disturbance: Hyperkalemia: (peaked T) Hypokalemia: (U wave) Hypercalcemia: (QT Shortening) Hypocalcemia: (QT Elongation) Interpret this ECG case, before checking its answer beneath it: RBBB 19
First Aid Cases? 20
Past-Years Mini-OSCE Question: A 68 year old male presents with hx of frequent palpitations. What is your diagnosis? Answer: AF Note: Arrythmias were discussed in 10 minutes out of 2 hours, this sheet provide the most important ones according to what the doctor came through and what Davidson emphasized on. Make an effort to differentiate Normal from Abnormal ECG, and diagnose MI, Angina, Bundle Branch Blocks, AV Blocks, Tachycardia, Bradycardia, Axis deviation, Atrial and Ventricular hypertrophy, and Abnormal/ectopic/SV rhythms in general. Good Luck. Melad 21
Reminders 8 REMINDERS WHAT TO LOOK FOR 1. The rhythm and conduction: sinus rhythm or some early arrhythmias evidence of first, second or third degeree block evidence of bundle branch block. 2. P wave abnormalities: peaked, tall right atrial hypertrophy notched, broad left atrial hypertrophy. 3. The cardiac axis: right axis deviation QRS complex predominantly downward in lead I left axis deviation QRS complex predominantly downward in leads II and III. 4. The QRS complex: width: if wide, ventricular origin, bundle branch block or the WPW syndrome height: tall R waves in lead V 1 in right ventricular hypertrophy tall R waves in lead V 6 in left ventricular hypertrophy transition point: R and S waves are equal in the chest leads over the interventricular septum (normally lead V 3 or V 4 ) clockwise rotation (persistent S wave in lead V 6 ) indicates chronic lung disease. Q waves:? septal? infarction. 5. The ST segment: raised in acute myocardial infarction and in pericarditis depressed in ischaemia and with digoxin. 6. T waves: peaked in hyperkalaemia flat, prolonged, in hypokalaemia inverted: normal in some leads ischaemia infarction left or right ventricular hypertrophy pulmonary embolism bundle branch block. 7. U waves: can be normal hypokalaemia. 175
Now test yourself REMINDERS CONDUCTION PROBLEMS First degree block One P wave per QRS complex. PR interval greater than 200 ms. Second degree block Wenckebach (Mobitz type 1): progressive PR lengthening then a nonconducted P wave, and then repetition of the cycle. Mobitz type 2: occasional nonconducted beats. 2:1 (or 3:1) block: two (or three) P waves per QRS complex, with a normal P wave rate. Third degree (complete) block No relationship between P waves and QRS complexes. Usually, wide QRS complexes. Usual QRS complex rate less than 50/min. Sometimes, narrow QRS complexes, rate 50 60/min. Right bundle branch block QRS complex duration greater than 120 ms. RSR 1 pattern. Usually, dominant R 1 wave in lead V 1. Inverted T waves in lead V 1, and sometimes in leads V 2 V 3. Deep and wide S waves in lead V 6. Left anterior hemiblock Marked left axis deviation deep S waves in leads II and III, usually with a slightly wide QRS complex. Left bundle branch block QRS complex duration greater than 120 ms. M pattern in lead V 6, and sometimes in leads V 4 V 5. No septal Q waves. Inverted T waves in leads I, VL, V 5 V 6 and, sometimes, V 4. Bifascicular block Left anterior hemiblock and right bundle branch block (see above). 176
Reminders 8 REMINDERS CAUSES OF AXIS DEVIATION Right axis deviation Normal variant tall thin people. Right ventricular hypertrophy. Lateral myocardial infarction (peri-infarction block). Dextrocardia or right/left arm lead switch. The Wolff Parkinson White (WPW) syndrome. Left posterior fascicular block. Left axis deviation Left anterior hemiblock. The WPW syndrome. Inferior myocardial infarction (peri-infarction block). Ventricular tachycardia. REMINDERS POSSIBLE IMPLICATIONS OF ECG PATTERNS P:QRS apparently not 1:1 If you cannot see one P wave per QRS complex, consider the following: If the P wave is actually present but not easily visible, look particularly at leads II and V 1. If the QRS complexes are irregular, the rhythm is probably atrial fibrillation, and what seem to be P waves actually are not. If the QRS complex rate is rapid and there are no P waves, a wide QRS complex indicates ventricular tachycardia, and a narrow QRS complex indicates atrioventricular nodal (junctional or AV nodal) re-entry tachycardia. If the QRS complex rate is low, it is probably an escape rhythm. P:QRS more than 1:1 If you can see more P waves than QRS complexes, consider the following: If the P wave rate is 300/min, the rhythm is atrial flutter. If the P wave rate is 150 200/min and there are two P waves per QRS complex, the rhythm is atrial tachycardia with block. If the P wave rate is normal (i.e. 60 100/min) and there is 2:1 conduction, the rhythm is sinus with second degree block. If the PR interval appears to be different with each beat, complete (third degree) heart block is probably present. continued 177
Now test yourself REMINDERS POSSIBLE IMPLICATIONS OF ECG PATTERNS continued Wide QRS complexes (greater than 120 ms) Wide QRS complexes are characteristic of: Sinus rhythm with bundle branch block Sinus rhythm with the WPW syndrome Ventricular extrasystoles Ventricular tachycardia Complete heart block. Q waves Small (septal) Q waves are normal in leads I, VL and V 6. A Q wave in lead III but not in VF is a normal variant. Q waves probably indicate infarction if present in more than one lead, are longer than 40 ms in duration and are deeper than 2 mm. Q waves in lead III but not in VF, plus right axis deviation, may indicate pulmonary embolism. The leads showing Q waves indicate the site of an infarction. ST segment depression Digoxin: ST segment slopes downwards. Ischaemia: flat ST segment depression. T wave inversion Normal in leads III, VR and V 1 ; and in V 2 V 3 in black people. Ventricular rhythms. Bundle branch block. Myocardial infarction. Right or left ventricular hypertrophy. The WPW syndrome. 178