ECG BASICS By Dr Bashir Ahmed DarChinkipora Sopore KashmirAssociate Professor MedicineEmail firstname.lastname@example.org
From Right to Left • Dr.Smitha associate prof gynae • Dr Bashir associate professor Medicine • Dr Udaman neurologist • Dr Patnaik HOD ortho • Dr Tin swe aye paeds
From RT to Lt • Professor Dr Datuk rajagopal N • Dr Bashir associate professor medicine • Dr Urala HOD gynae • Dr Nagi reddy tamma HOD-opthomology • Dr Setharamarao Prof ortho
ELECTROGRAPHY MADE EASY • ULTIMATE AIM TO HELP PATIENTS
Limb and chest leads • When an ECG is taken we put 4 limb leads or electrodes with different colour codes on upper and lower limbs one each at wrists and ankles by applying some jelly for close contact. • We also put six chest leads at specific areas over the chest • So in reality we see only 10 chest leads.
Position of limb and chest leads Four limb leads Six chest leads V1- 4th intercostal space to the right of sternum V2- 4th intercostal space to the left of sternum V3- halfway between V2 and V4 V4- 5th intercostal space in the left mid-clavicular line V5- 5th intercostal space in the left anterior axillary line V6- 5th intercostal space in the left mid axillary line
LA LV RA RV V4 V1 V2 V2 V3 V3 V5 V5 V6 V6 V1 V4 Horizontal plane - the six chest leads 6.5
ECG Paper: Dimensions 5 mm 1 mm Voltage ~Mass 0.1 mV 0.04 sec 0.2 sec Speed = rate
ECG paper and timing • ECG paper speed = 25mm/sec • Voltage calibration 1 mV = 1cm • ECG paper - standard calibrations • each small square = 1mm • each large square = 5mm • Timings • 1 small square = 0.04sec • 1 large square = 0.2sec • 25 small squares = 1sec • 5 large squares = 1sec
After applying these leads on different positions then these leads are connected to a connector and then to ECG machine. • The speed of machine kept usually 25mm/second.calibration or standardization done while machine is switched on.
ECG paper 1 Small square = 0.04 second 1 Large square = 0.2 second 5 Large squares = 1 second Time 2 Large squares = 1 cm 6.1
The first step while reading ECG is to look for standardization is properly done. • Look for this mark and see that this mark exactly covers two big squares on graph.
STANDARDISATION ECG amplitude scale Normal amplitude 10 mm/mV Half amplitude 5 mm/mV Double amplitude 20 mm/mV
ECG WAVES • You will see then base line or isoelectric line that is in line with P-Q interval and beginning of S-T segment. • From this line first positive deflection will arise as P wave then other waves as shown in next slide. • Small negative deflections Q wave and S wave also arise from this line.
The Normal ECG Normal Intervals: PR 0.12-0.20s QRS duration <0.12s QTc 0.33-0.43s
Simplified normal Position of leads on ECG graph • Lead 1# upward PQRS • Lead 2# upward PQRS • Lead 3# upward PQRS • Lead AVR#downward or negative PQRS • Lead AVL# upward PQRS • Lead AVF# upwards PQRS
Simplified normal Position of leads on ECG graph • Chest lead V1# negative or downward PQRS • Chest leads V2-V3-V4-V5-V6 all are upright from base line .The R wave slowly increasing in height from V1 to V6. • So in normal ECG you see only AVR and V1 as negative or downward defelections as shown in next slide.
Normal ECG Slide 13
P-wave • Normal P wave length from beginning of P wave to end of P wave is 2 and a half small square. • Height of P wave from base line or isoelectric line is also 2 and a half small square.
Normal values up in all leads except AVR. Duration. < 2.5 mm. Amplitude. < 2.5 mm. Abnormalities 1. Inverted P-wave Junctional rhythm. 2.Wide P-wave(P- mitrale) LAE 3.Peaked P-wave (P-pulmonale) RAE 4. Saw-tooth appearance Atrial flutter 5. Absent normal P wave Atrial fibrillation P-wave
P wave height 2 and half small squares ,width also 2 and half small square
Shape of P wave • The upward limb and downward limbs of P wave are equal. • Summit or apex of P wave is slightly rounded.
P pulmonale & P mitrale • P pulmonale-Summit or apex of P wave becomes arrow like pointed or pyramid shape,the height also becomes more than two small squares from base line. • P waves best seen in lead 2 and V1.
P pulmonale & P mitrale • P mitrale- the apex or summit of p wave may become notched .the notch should be at least more than one small square. • Duration of P becomes more than two and a half small squares.
Left Atrial Enlargement Criteria P wave duration in II >than 2 and half small squares with notched p wave or Negative component of biphasic P wave in V1≥ 1 “small box” in area
Right Atrial Enlargement Criteria P wave height in II >2 and half small squares and are also tall and peaked. or Positive component of biphasic P wave in V1 > 1 “small box” in area
Atrial fibrillation • P waves thrown into number of small abnormal P waves before each QRS complex • The duration of R-R interval varies • The amplitude of R-R varies • Abnormal P waves don’t resemble one another.
Atrial flutter • The P waves thrown into number of abnormal P waves before each QRS complex. • But these abnormal P waves almost resemble one another and are more prominent like saw tooth appearance.
Junctional rhythm • In Junctional rhythm the P waves may be absent or inverted.in next slide u can see these inverted P waves.
Paroxysmal atrial tachycardia • The P and T waves you cant make out separately • The P and T waves are merged in one • The R-R intervals do not vary but remain constant and same. • The heart rate being very high around 150 and higher.
NORMAL P-R INTERVAL • PR interval time 0.12 seconds to 0.2 seconds. • That is three small squares to five small squares.
Definition: the time interval between beginning of P-wave to beginning of QRS complex. Normal PR interval 3-5mm or 3-5 small squares on ECG graph (0.12-0.2 sec) Abnormalities 1. Short PR interval WPW syndrome 2. Long PR interval First degree heart block PR interval
Short P-R interval • Short P-R interval seen in WPW syndrome or pre- excitation syndrome or LG syndrome • P-R interval is less than three small squares. • The beginning of R wave slopes gradually up and is slightly widened called Delta wave. • There may be S-T changes also like ST depression and T wave inversion.
Lengthening of P-R interval • Occurs in first degree heart block. • The P-R interval is more than 5 small squares or > than 0.2 seconds. • This you will see in all leads and is same fixed lengthening .
Q WAVES • Q waves <0.04 second. • That’s is less than one small square duration. • Height <25% or < 1/4 of R wave height.