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Cardiovascular System ANALYSIS Dr.Mohammed Sharique Ahmed Quadri Asst. Professor Physiology Almaarefa College بسم الله الرحمن الرحيم 1

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The simple steps to analyze the ECG How to calculate the heart rate. How to analyze the rhythm. To calculate the QRS axis 2

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THE 12-LEADS The 12-leads include: –3 Limb leads (I, II, III) –3 Augmented leads (aVR, aVL, aVF) –6 Precordial leads (V 1 - V 6 ) 3

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VIEWS OF THE HEART Some leads get a good view of the: Anterior portion of the heart (V1,V2,- setum V3,V4-)- anterior Left Lateral portion of the heart ( I, Avl, v5,v6) Inferior portion of the heart II, III, aVF 4

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BASIC COMPONENTS 5

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THE “PQRST” P wave - Atrial depolarization T wave - Ventricular repolarization QRS - Ventricular depolarization 6

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THE PR INTERVAL Atrial depolarization + delay in AV junction (AV node/Bundle of His) (delay allows time for the atria to contract before the ventricles contract) 7

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SEGMENTS & INTERVALS PR interval: 0.12 – 0.20 sec QRS interval : 0.08 – 0.10sec QT interval : 0.40-0.43sec ST interval :0.32 - sec 8

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HOW TO READ THE ECG Rhythm analysis Analyzing individual wave & segments Determine the mean electrical axis 9

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RHYTHM ANALYSIS Step 1:Determine regularity. Step 2:Calculate rate. Step 3:Assess the P waves. Step 4:Determine PR interval. Step 5:Determine QRS duration. 10

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1-DETERMINE REGULARITY Look at the R-R distances (using a caliper or markings with a pen on paper). Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular? Interpretation? Regular RR 11

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12 Find the R wave that falls on, or nearly on, one of the heavy lines. Count the number of large square or small square until the next R wave Deter mine the heart rate by applying following formula

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2-CALCULATING HEART RATE H.R = 1500 NO OF SMALL SQURES BETWEEN R-R WAVES OR H.R = 300 NO OF BIG SQURES BETWEEN R-R WAVES 13

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That’s why I selected medical profession

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CALCULATE RATE Option 2 Find a R wave that lands on a bold line. Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. (cont) R wave 15

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3-ASSESS THE P WAVES Are there P waves? Do the P waves all look alike? Do the P waves occur at a regular rate? Is there one P wave before each QRS? Interpretation? Normal P waves with 1 P wave for every QRS 16

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4-DETERMINE PR INTERVAL Normal: 0.12 - 0.20 seconds. (3 - 5 boxes) Interpretation? 0.12 seconds 17

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5-QRS DURATION Normal: 0.04 - 0.12 seconds. (1 - 3 boxes) Interpretation? 0.08 seconds 18

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RHYTHM SUMMARY Regularityregular Rate90-95 bpm P wavesnormal PR interval0.12 s QRS duration0.08 s Interpretation? Normal Sinus Rhythm 19

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Calculate Heart Rate. 20 Normal ECG

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35 bpm Rate? Regularity? regular normal 0.10 s P waves? PR interval? 0.12 s QRS duration? Interpretation? Sinus Bradycardia VARIATIONS IN SINUS RHYTHM

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130 bpm Rate? Regularity? regular normal 0.08 s P waves? PR interval? 0.16 s QRS duration? Interpretation? Sinus Tachycardia VARIATIONS IN SINUS RHYTHM

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INTERPRETE THE ECG ? SINUS ARHYTHMIA Observe Variation in Heart Rate during Inspiration and Expiration. [Increased Heart Rate during Inspiration] 23

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Deviation from NSR No organized atrial depolarization, so no normal P waves (impulses are not originating from the sinus node). The atrial rate is usually above 350 beats per minute Atrial activity is chaotic (resulting in an irregularly irregular rate). Common, affects 2-4%, up to 5-10% if > 80 years old

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70 bpm Rate? Regularity? regular flutter waves 0.06 s P waves? PR interval? none QRS duration? Interpretation? Atrial Flutter

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1st Degree AV Block 2nd Degree AV Block, MobitzType I 2nd Degree AV Block,MobitzType II 3rd Degree AV Block

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60 bpm Rate? Regularity? regular normal 0.08 s P waves? PR interval? 0.36 s QRS duration? Interpretation? 1st Degree AV Block Take a look at this ECG. What do you notice PR Interval> 0.20 s Etiology: Prolonged conduction delay in the AV node or Bundle of His.

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50 bpm Rate? Regularity? regularly irregular normal, but 4th no QRS 0.08 s P waves? PR interval? lengthens QRS duration? Interpretation? 2nd Degree AV Block, Type I Take a look at this ECG. What do you notice –PR interval progressively lengthens, then the impulse is completely blocked (P wave not followed by QRS). Etiology: Each successive atrial impulse encounters a longer and longer delay in the AV node until one impulse (usually the 3rd or 4th) fails to make it through the AV node.

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40 bpm Rate? Regularity? regular normal, 2 & 3 no QRS 0.08 s P waves? PR interval? 0.14 s QRS duration? Interpretation? 2nd Degree AV Block, Type II Take a look at this ECG. What do you notice Occasional P waves are completely blocked (P wave not followed by QRS). Etiology: Conduction is all or nothing (no prolongation of PR interval); typically block occurs in the Bundle of His.

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40 bpm Rate? Regularity? regular no relation to QRS wide (> 0.12 s) P waves? PR interval? none QRS duration? Interpretation? 3rd Degree AV Block Take a look at this ECG. What do you notice Etiology: There is complete block of conduction in the AV junction, so the atria and ventricles form impulses independently of each other. Without impulses from the atria, the ventricles own intrinsic pacemaker kicks in at around 30 - 45 beats/minute.

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When an impulse originates in a ventricle, conduction through the ventricles will be inefficient and the QRS will be wide and bizarre.

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Determination of Mean Electrical Axis Axis refers to the mean QRS axis (or vector) during ventricular depolarization. As you recall when the ventricles depolarize (in a normal heart) the direction of current flows leftward and downward because most of the ventricular mass is in the left ventricle. We like to know the QRS axis because an abnormal axis can suggest disease such as pulmonary hypertension from a pulmonary embolism. 32

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When a vector is exactly horizontal and directed toward the person’s left side,the vector is said to extend in the direction of 0 degrees From this zero reference point, the scale of vectors rotates clockwise: 33

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I III II 34 I II III

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aVR aVL aVF 35

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-90 -120 -60 aVR aVL -150 -30 180 0 I +150 +30 III+120 +60 II +90 aVF FORMATION OF HEXAAXIAL SYSTEM 36

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Determination of Mean Electrical Axis The QRS axis is determined by overlying a circle, in the frontal plane. By convention, the degrees of the circle are as shown. The normal QRS axis lies between -30 o and +110 o. 0o0o 30 o -30 o 60 o -60 o -90 o -120 o 90 o 120 o 150 o 180 o -150 o A QRS axis that falls between -30 o and -90 o is abnormal and called left axis deviation. A QRS axis that falls between +110 o and +180 o is abnormal and called right axis deviation. A QRS axis that falls between +180 o and -90 o is abnormal and called Indeterminant (extende rt axis ). 37

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HOW TO CALCULATE THE QRS AXIS Leads & there isoelectric partners 38

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Indeterminant /extended RAD LAD RAD NORMAL AXIS

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… if the QRS is negative in lead I and negative in lead II what is the QRS axis? (normal, left, right or right superior axis deviation) QRS Complexes Axis I aVF + + + - - + - - normal left axis deviation right axis deviation right superior axis deviation/ indeterminant How to calculate the QRS axis 42

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What is Axis ? 43 Normal ECG

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References The ECG made Easy by John R.Hampton 7th edition The only EKG book you will ever need,Malcolm.S.Thaler, seventh edition Introduction to ECG interpretation BY Frank G. Yanowitz

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