Hasan Ali Al _farhan FACC,FICMS Cardiol,DIC. Al _Kindy College of medicine ,
Electrocardiogram ECGIntroduction
During depolarization & depolarization of the cardiac tissue ,there are changes in the electrical field around the heart. ECG is the recording of these changes . This recording is by surface leads (chest and limbs).Definitions
Automaticity : ability of self stimulation. Rhythmicity: forming impulses at regular intervals. Refractory period : time during which the cardiac tissue is refractory to be stimulated Conductivity All or none response. ContractilityConductive Tissue of the Heart
Sino atrial node SA node Intra atrial tracts Atrio-ventricular node AV node Atrio-ventricular junction Bundle of Hiss : Left Bundle branch LBB Anterior fascicle posterior fascicle Right Bundle Branch Purkinje fibersPace Maker
The tissue with higher rate of discharging impulses, usually the SA node(60-100/min) Other pacemakers : Atrial tissue 60-80/min. A-V junction 40-60/min. Purkinje system 20-40/min.The ECG paper
Thermal sensitive paper Measured tow elements : Time &Voltage Horizontal plane measure the time Vertical plane measure the voltage Basic element of the ECG paper is a small square 1mm = 0.04 sec. in the horizontal plane & 1 mm = 0.1 mvolt. In the vertical planeECG Recording
The electrical activity is recorded by Leads positioned at variable points over the body. These are 12 standard leads : Bipolar Limb leads : I(Rt arm-Lt arm) ,II(Rt arm-Lt leg),III (Lt arm-Lt leg) Unipolar Limb leads: aVR(Rt arm), aVL(Lt arm), aVF(Lt leg).
Unipolar Chest Leads
V1: 4th Rt intercostal space V2: 4th Lt intercostal space V3: between V2 & V4 V4: 5th intercostal space mid clavicular line. V5: 5th intercostal space anterior axillary line. V6: 5th intercostal space mid axillary lineImportant points in the ECG
Correct labeling of the ECG : name , age & exact timing. Correct connection . Correct Calibration :10 mm= 1 m volt. Correct speed (25 mm/sec.)Components of ECG
Base line or isoelectrical line. Wave : positive (upward), negative (downward). Segment :length between 2 waves, named by the wave before and after. Interval: length of wave or segment. Complex: group of waves in sequence , QRS complex.How to read the ECG
You showed have a system to read & report the followings: Name, Time & date, Calibration, Correct connection ,Rate, Rhythm, Axis. ECG waves , intervals, complex, segmentDefinitions
P wave = Atrial depolarization. PR interval = Time for the impulse to travel from SA node to Myocardium. QRS = ventricular depolarization ST segment = Isoelectrical period before re polorazation T wave = ventricular repolarizationCalibration
Normal Calibration : 1 mvol. = 10 mm vertical distance
Connection
Misplacement of placement results in abnormal ECG and misdiagnosisHeart Rate
In normal sinus rhythm , the Atrial rate =ventricular rate =Heart rate Exceptions : e.g In Atrial fibrillation & ventricular tachycardiaEach small squire 1 mm = 0.04 ms , ECG paper speed 25mm/sec, 25 x 60=1500 mm/min. Measure P – P interval --- 1500/ P-P = Atrial rate Measure R-R interval --- 1500/R-R = ventricular rate R R R R R
P
P
P
P
P-P =15 mm, R-R= 15 mm, HR 1500/15 = 100 beat/min.
Heart Rate
If we use the large squire :One large = 5 small sq. = 5 mm 5 x 60 = 300 Measure P-P interval – 300/P-P= HRMeasure R-R interval -300/R-R= HR RR
P
P
P-P = 3 large sq. , R-R = 3 large sq. – HR = 300/3 = 100 beat/min
Cardiac Rhythm
Is the rhythm regular or not ? The intervals between various points are equal.
R
R
R
P
P
P
The ECG components P wave - represent atrial contraction or depolarization Duration = 3mm (3 small sq.) Height = 2.5 mm Usually the 1st +ve deflection except in lead aVR Usually rounded Notched P wave – LT atrial enlargement (lead II) Biphasic usually in lead V1 , pecked P wave RT atrial enlargement ( lead III) P
Notched
BiphasicRT Atrial Enlargement , pecked P wave in lead II ( P Pulmonale)
The PR intervalRepresents the time needed for the impulse to travel from The SA node –Atria– AV node (where there is usually delay)– Bundle of His – Rt & LT bundle branches– Perkinji fibers – ventricle.PR = 3 mm – 5 mm ( 0.12 -0.2 sec.) Measured from the begging of P to the beginning of R wave
PR interval
The QRS
Consists from many wave forms :Q wave = The 1st _ve deflection after the P wave.R wave is the 1st +ve deflection after the P wave.S wave is the 1st _ve deflection after the R wave QRS complex may consist of all 3 components or only 2 (RS ,QR)Some time one wave may have more than on deflections :R S R’Q
R
S
QRS voltage = variable according to age , sex ,body build .Low voltage ECG =if the sum R+S in lead I II III < 15 mm seen in advanced heart failure, obesity , emphysema, pericardia effusion.
High voltage ECG if R wave in I or aVL > 20 mm, S V1 + R V5 or V6 > 35 mm seen in left ventricular hypertrophy
Q wave 1st downward deflection after P wave
Normally can be seen in lead in aVR and small q wave in some other leadsNormal septal small Q wave of lead 1
Pathological Q wave , Deep > 25% of preceding R wave or wide > 0.04 sec.
The ST segment : Iso electrical period between ventricular depolarization and repolarization
ST deviation from base line is abnormal , either ST elevation in MI , pericarditis or ST depression seen in myocardial ischemia , electrolyte disturbances, Ventricular hypertrophy
ST DEP
ST ELEVThe T wave : ventricular repolarization
Usually Up in lead I,II, V3-V6 Usually down in aVR Usually variable in lead III, aVF, aVL,V1V2 Shape : usually rounded , pecked seen in MI Height 5 mm in limb leads , 10 mm in chest leads Tall T wave in MI ,CVA, HyperkalemiaThe QT interval
Measured from the begging of Q to the end of T wave ( Ventricular depolarization + iso electrical + ventricular repolarization) Normal = 0.32 msec.--- 0.46 msec. Prolonged in heart failure, hypocalemia, drugsQ
T
U Wave
*May be seen in normal ECG usually after the T wave especially in lead V3. *Same direction of T wave . *Become prominent in hypokalemia * Becomes opposite to T wave direction in Myocardial ischemiaCardiac Axis (QRS Axis)
It is the average direction of spread of ventricular depolarization. We have to chose 2 leads perpendicular on each other : Lead I X aVF Lead II X aVL Lead III X aVRLead I +ve Zero
Lead aVF + 90+ 180
- 90 -VE
aVL -30Lead II +60
Lead III + 120
aVR = 210
-VE
Lead I +ve Zero
aVF + 90-VE
-VE 90
I +ve
aVF + 90* * * * * *
******
+ 70
Lead I = +ve 9 mm, -ve 3 mm =+ve 6 mm put in on the +ve side of it Lead aVF = +ve 9mm put it on the +ve side of it and get the Axis
The normal Axis ( - 30 +110)
- 30+ 110
RT Axis Deviation > + 120
Lead IIIaVL -30
LT Axis Deviation > - 30
aVL - 30Ischemic Heart Disease
Angina pectoris : it is mainly clinical diagnosis. Only 50% of cases got ECG changes if it is taken during the attack of chest pain. It is mainly ST segment Depression except in PrinzMetal Angina where it is ST elevation.ST DEP
Myocardial InfarctionIndicate Myocardial necrosis and death Mainly of two types : 1.ST Elevation MI STEMI , full thickness MI , transmural MI, Q MI 2.Non ST Elevation MI , NSTEMI , Sub Endocrinal MI , Non Q MI
Pathological Q wave , Deep > 25% of preceding R wave or wide > 0.04 sec.
STEMI : stagesStage 1 : peaked T wave + ST segment Elevation, sub endocrinal injury , no cell death( 1st few hours) . Stage 2 : Loss of amplitude of R wave , still ST elevation , 1st day , injury extend to epicardium Stage 3 : T inversion ,beginning of Q wave , decrease of ST elevation, 2-3 day Stage 4 : Deep T wave inversion , Marked Q wave , ST my back to base line, > 3 day . Stage 5 :after several weeks : ST back normal,Q wave , T inversion less
Beginning of ST Elev.
Pecked T waveST ELEV
Age of Myocardial Infarction
Acute : peaked T wave ,ST segment elevation. Recent : ST segment Elevation , T wave inversion. Old : If only Q wave .NSTEMI
No ST segment elevation ST segment depression , T wave inversion.NSTEMI
Localization of the Myocardial infarctionInferior surface
III aVF II
Lateral surface aVL I V5 V6
Anterior V1,V2,V3,V4
Localization of MI
Anterior V1V2V3V4 Inferior II III aVF Lateral aVL I V5, V6Chambers Enlargement :Atrial Enlargement
Left Atrial Enlargement P wave < 0.12 sec width , < 0.1 sec height
If the P wave > 0.12 sec( 3 mm) usually in any lead. Notched P wave usually in lead I ,aVl may be lead II Negative terminal portion of P wave in V1 , 1 mm depth and 3 mm width( most specific) Since Mitral valve stenosis is the most common cause of LA enlargement . It is called P MitraleNotched
BiphasicRT Atrial Enlargement
P wave > 0.12 sec , 2.5 mm (pecked) usually in Lead II III aVF and V1. It is called P pulmonale , because chronic pulmonary disease is frequently the cause.LT Ventricular Hypertrophy
Voltage criteria : R Lead 1 or aVL > 20 mm R V5 or V6 + S V1 > 35 mm In sever LVH There will be ST segment depression and T wave inversion in Lateral leads (I aVL,V5 V6)RT Ventricular Hypertrophy
Prominent R in V1 ( =or > S wave) . prominent S in V 6( = or > R wave ). Usually associated with RT axis deviation(>+110). In sever RVH ST depression & T wave inversion V1 may be V2 V3Heart Block
The impulse will be conducted from : SA node --- AV node ---- Bundle of His --- RT & LT bundle branches. Any interference with this path way leads to impulse delay or block Level of the block : SA block , AV block , Bundle branch block (BBB), Fascicular blockSA Block
Impulse in generated in the SA node but it couldn't propagated further( Exit block), there is no impulse and in ECG paper no recording . The gap recorded on ECG paper is multiplication RR interval The heart has to have other pace maker from lower sites.AV node Block
The most common site of block . Of three degrees : 1st Deg. : all impulses from SA node will reach the ventricle but with delay , normal P wave followed by normal QRS but the PR interval is > 0.2 sec (5mm)Second degree AV Block
Two types : Mobitz type 1 (wenchebach phenomena): Progressive PR segment prolongation till the beat will drop out , P wave which will not followed by QRS , the cycle will recurs again .Mobetiz type 2
P wave which is not followed by QRS with out preceding PR segment prolongation. We see P waves> than QRS complexes, if the P waves are double the no. of QRS , called 2:1 block , if every 3 Ps one QRS complexes , called 3:1 block and so on . The more the no of P for QRS the more sever the block.Third degree AV block Complete Heart Block
The impulse generated in the SA node will not pass at all to the ventricle , the lower pace maker in the Perkinje fibers will act to stimulate the ventricle . There are P waves not related to QRS complexes, PP interval regular and different from RR interval also regular at other rate (30-40 b/min)Bundle Brach Block
RT BBB : QRS > 0.12 , Broad S lead I and V6 rSR in V1 . T inversion in V1-V3rSR
LT Bundle Branch Block
QRS > 0.11 RSR in lead I aVL , V5 V6. ST segment depression , T wave inversion in the same leads. High voltage but LVH cannot be diagnosed.Fascicular Block
LT anterior hemi block : unexplained LT axis deviation. LT posterior hemi block : RT axis deviationDysrythmia
Look at the ECG , regular or irregular. If it is regular irregularity or irregular irregularity . Look for the P wave and its relation to QRS Look to the Shape of the P wave and QRS configuration.Sinus Bradycardia
There P wave for each QRS. PP or RR < 60 beat/mint . Frequently seen in Athletes , Hypothyroidism Hypothermia, Increased intracranial pressure, inferior MI.Sinus Tachycardia
Hear rate > 100 b/min. P wave for each QRS . Seen in fever , anxiety ,exercise, anemia , hyperthyrodsim.Sinus Arrhythmia
P wave for each QRS but the rate is irregular The longest RR interval > the shortest RR by 0.16 sec. (4 mm) , then sinus arrhythmia is diagnosed. Normal in infants and young children . Pathological in elderly .Atrial Premature Contraction (APC)
Basically the ECG is regular , some impulses are not , but there is P wave (which looks different from previous one) for each QRS (which is normal). The PR interval is changeable in these beats ( shorter or longer).
The second beat is sinus but comes at an earlier time
Multifocal Atrial Tachycardia (MAT)Different Shape P waves, different PR interval ,different PP and RR interval . Multiple area of origin of P wave . Usually seen in patient with advanced pulmonary disease.