![QRS COMPLEX
QRS in limb leads
Initial negative deflection Q wave
First positive deflection R wave
First negative wave after positive wave S wave
Second upright wave following S wave R’[R prime]](https://image.slidesharecdn.com/basicppt-131030093057-phpapp01/85/Introduction-to-ECG-29-320.jpg)
Introduction to ECG
- 1. What is an ECG? An electrocardiogram (ECG or EKG) is a graphic recording of electric potentials generated by the heart that reaches the body surface. Since body fluids are good conductors, electrical activity of heart can be recorded extracellularly . The record of these potential fluctuation during the cardiac cycle is the electrocardiogram.
- 2. In heart electrical activity is shown by pacemaker cells Conducting cells cardiac muscle ECG recorded denotes electricular activity of cardiac muscle ECG is recorded by instrument known as electrocardiograph Continuos ECG recording in ambulatory patient is by Holter monitor
- 3. Useful in diagnosis of… Cardiac Arrhythmias Myocardial ischemia and infarction Pericarditis Chamber hypertrophy Electrolyte disturbances Drug effects and toxicity
- 4. HISTORY Augustus D Waller recorded first human ECG But he thought his work has little clinical application
- 5. 1906 - using the string electrometer EKG, William Einthoven diagnoses some heart problems 1924- the noble prize for physiology or medicine is given to William Einthoven for his work on EKG 1938 -AHA and Cardiac society of great Britain defined the position of chest lead 1942- Goldberger increased Wilson’s Unipolar lead voltage by 50% and made Augmented leads
- 6. IMPULSE CONDUCTION IN HEART Sinoatrial node AV node Bundle of His Bundle Branches Purkinje fibers
- 7. ECG BASICS The output of ECG is a graph with time represented on x axis and voltage represented on y axis ECG graphs: 1 mm squares 5 mm squares Paper Speed: 25 mm/sec standard Voltage Calibration: 10 mm/mV standard
- 8. ECG PAPER DIMENSIONS X-Axis represents time - Scale X-Axis – 1 mm = 0.04 sec Y-Axis represents voltage - Scale Y-Axis – 1 mm = 0.1 Mv Each small square is 0.04 sec (1 mm in size) One big square on X-Axis = 0.2 sec (big box) Two big squares on Y-Axis = 1 milli volt (mV) Each big square on the ECG represents 5 small squares = 0.04 x 5 = 0.2 seconds 5 such big squares = 0.2 x 5 = 1sec = 25 mm One second is 25 mm or 5 big squares One minute is 5 x 60 = 300 big squares = 1500 small square
- 9. ECG Leads Potentials generated by the cardiac electrical field and modified by transmission factors are sensed by electrodes placed on the torso that are configured to form various types of leads. Electrodes are metal devices applied to chest wall that sense electrical activity of heart Electrodes are connected to form leads Leads could be bipolar or unipolar Bipolar leads-The electrocardiographic leads are bipolar leads that record the potential difference between two electrodes.one electrode is positive the other is negative and potential difference between them is measured. Unipolar leads- Multiple electrodes are electrically connected together to represent the negative member of the bipolar pair. This electrode network or compound electrode is referred to as a reference electrode. The lead then records the potential difference between a single electrode serving as the positive input, the exploring electrode, and the potential in the reference electrode.
- 10. BASIC OF VECTORS When a depolarization wavefront moves toward a +ve electrode, it creates a +ve deflection on the ECG in the corresponding lead. When a depolarization wavefront moves away from a +ve electrode, it creates a - ve deflection on the ECG in the corresponding lead. When a depolarization wavefront moves perpendicular to a +ve electrode, it creates anequiphasic (or isoelectric) complex on the ECG. It will be positive as the depolarization wavefront (or mean electrical vector) approaches (A), and then become negative as it passes by (B).
- 11. ECG Leads The standard ECG has 12 leads 3 Standard Limb Leads 3 Augmented Limb Leads 6 Precordial Leads The axis of a lead is the viewpoint from which it looks at the heart
- 12. Gold Berger :aV frontal leads Wilson & co-workwers :chest leads
- 13. Standard Limb Leads They are bipolar limb leads Records potential difference between two electrodes placed on different sides of heart LEAD 1 between RA LA LEAD II between RA LL LEAD III between LA LL
- 14. The electrical connections for these leads are such that the leads form a triangle, known as the Einthoven triangle. In it, the potential in lead II equals the sum of potentials sensed in leads I and III, as shown by this equation: I + III = II This relationship is known as Einthoven's law or Einthoven's equation
- 15. UNIPOLAR LIMB LEADS Measures absolute potential at the site The negative electrode is so constructed that it is considered to be at zero potential The negative, or reference, input is composed of a compound electrode known as the Wilson central terminal. This terminal is formed by combining the output of the left arm (LA), right arm (RA), and left leg (LL) electrodes through 5000-Ω resistances
- 16. Precordial Leads V1 Fourth ICS, right sternal border V2 Fourth ICS, left sternal border V3 Equidistant between V2 and V4 V4 Fifth ICS, left Mid clavicular Line V5 Fifth ICS Left anterior axillary line V6 Fifth ICS Left mid axillary line
- 17. Precordial leads
- 18. OTHER PRECORDIAL LEADS The right-sided precordial leads V3R to V6R are taken in mirror image positions on the right side of the chest V7 – Posterior axillary line V8 – Posterior scapular line V9 – Left border of spine
- 19. AUGEMENTED LIMB LEADS The three augmented limb leads are designated aVR, aVL, and aVF The reference potential for the augmented limb leads is formed by connecting the two limb electrodes that are not used as the exploring electrode This modified reference system was designed to produce a larger amplitude signal than if the full Wilson central terminal were used as the reference electrode. When the Wilson central terminal was used, the output was small, in part because the same electrode potential was included in both the exploring and the reference potential input. Eliminating this duplication results in a theoretical increase in amplitude of 50%.
- 20. EXPLORING ELECTRODE REFERENCE ELECTRODE aVR right arm left arm plus left leg aVL left arm right arm plus left leg aVF left foot right arm plus left arm
- 21. Lead aVR is oriented towards the heart cavity Lead aVL shows heart activity coming from the lateral wall of heart Lead aVF shows heart activity coming from inferior wall of the heart
- 23. CONTIGUOUS LEADS
- 24. WAVES AND MORPHOLOGY P WAVE REPRESENTS ATRIAL DEPOLARIZATION QRS COMPLEX REPRESENTS – VENTRICULAR DEPOLARIZATION ST-T-U COMPLEX REPRESENTS VENTRICULAR REPOLARIZATION
- 25. P wave Activation of atria <120 msec PR interval is from the beginning of P wave to the beginning of QRS – Normal up to 0.2 sec QRS comp. Activation of ventricles <110 msec ST segment – Normal Isoelectic (electric silence) T wave Ventricular repolarisation QT Interval – From the beginning of QRS to the end of T wave – Normal – 0.40 sec RR Interval – One Cardiac cycle 0.80 sec
- 26. P WAVE Represent atrial depolarization Mean p wave axis is +40 to +60 Always positive in lead I and II Always negative in lead aVR Biphasic in v1 Best seen in lead II Amplitude- 0.2 to 0.3 mv Duration-.06 sec to .12 sec
- 27. PR INTERVAL Measured from beginning of P wave to beginning of QRS Interval Represent conduction of impulse from atria to av node, bundle of his and right and left bundle branch Measured in the lead with the shortest PR interval Duration is 120-200 msec This delay allows time for atria to contract before ventricles start contracting
- 28. QRS COMPLEX Represents ventricular depolarization Ventricular excitation has two phases Interventricular septum depolarization from left to right Ventricular muscle depolarization from right to left because of muscle mass of left ventricle Depolarisation from endo to epicardium
- 29. QRS COMPLEX QRS in limb leads Initial negative deflection Q wave First positive deflection R wave First negative wave after positive wave S wave Second upright wave following S wave R’[R prime]
- 30. IV SEPTUM DEPOLARISATION First left part of septum is depolarized and then right part is depolarized So vector is directed towards right ,producing positive deflection in right oriented leads and negative deflection in left oriented leads
- 31. VENTRICULAR DEPOLARISATION Ventricular depolarization dominated by left ventricle QRS in chest leads V1 & V6 - V1 rS complex V6 qR complex Intermediate leads will show relative increase in R wave amplitude and decrease in S amplitude Where R and S wave are equal are called transition zone
- 32. NORMAL R WAVE PROGRESSION AND TRANSITON
- 33. QRS COMPLEX Normal axis from -30 to +100 Duration of QRS < 110 msec Negative in aVR and v1 to v3 Left axis deviation- -30 to -90 Right axis deviation from 100 to 180 Extreme axis deviation from -90 to 180
- 34. Rotation of the heart Around AP axis;here the axis runs through the IVS from the ant to post surface of the heart Horizontal position;main body of the LV is oriented upwards and to the left:towards leads I and avL(left axis) Vertical position;main body of the LV is oriented to leads II and avF(right and inferior)
- 36. ROTATION OF THE HEART Around oblique axis;the axis runs through the IVS from apex to base Anatomical rotation clock-wise and counter clock wise rotation Counter clock-wise more anterior position of LV Results in transition zone shifting to patient right leads
- 37. Clock wise rotation;here th RV assumes a more anterior position so that the IVS lay parallel to the chest wall There is a shift of the transition zone to the left of patient
- 38. ST SEGMENT Represent end of ventricular depolarization and beginning of ventricular repolarization The point that marks the end of the QRS complex and the beginning of the ST segment is known as the J point Typical duration of ST segment is 0.08seconds
- 39. T WAVE The T wave represents the repolarization (or recovery) of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred to as the relative refractory period . It tends to have a blunt apex with assymetrical limbs Always neg in lead aVR + in lead I, II, aVL , aVF Variable in lead III ,V1-V3 In V1,V2 T wave may be normally negative Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted. T wave follows the direction of the QRS deflection
- 40. U WAVE U wave related to afterdepolarizations which follow repolarization U waves are small, round, symmetrical and positive in lead II, with amplitude < 1 mm U wave direction is the same as T wave More prominent at slow heart rates Increased amplitude- drugs, hypokalemia Decreased amplitude- sign of angina Prominent U waves- torsades de pointes
- 41. QT INTERVAL Begins at beginning of QRS complex and ends at end of T wave. Includes total dur.of ventricular activation and recovery. Duration of QT interval decreases as heart rate increases. Normal QT interval </= 440msec. It should be measured in the lead that shows longest intervels
- 42. The most commonly used method for correcting the QT interval for rate is Bazett's formula = QTc is the QT interval corrected for rate, and RR is the interval from the onset of one QRS complex to the onset of the next QRS complex, measured in seconds QTc upper normal limits as 0.43 s in men and 0.45 s in women
- 43. DETERMINIG ECG RHYTHM P-P Interval helps in determining atrial rhythm R-R intereval helps in determining ventricular rhythm By two methods Paper and pencil method Caliper method
- 44. Determining the Heart Rate 10 times method 300 method 1500 method
- 45. 10 times method Obtain a 6 second strip of ecg Count the number of P waves and multiply by 10 to get atrial rate Count the number of R waves and multiply by 10 to get ventricular rate Especially useful if the rhythm is irregular
- 46. 300 Method Take the number of “big boxes” between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate Although fast, this method only works for regular rhythms.
- 47. THE RULE OF 300 No of big boxes Rate 1 300 2 150 3 100 4 75 5 60 6 50
- 48. 1500 method Used when heart rate is regular 1500 square represent one minute Count the number of small square between two R waves Divide 1500 by that number
- 49. HIS BUNDLE ELECTROGRAM In patient with heart block, the electrical events in AV node, bundle of His and Purkinje system are recorded by a catheter placed near tricuspid valve This record of electrical activity is called is calledHBE A- av node activation, H- HIS bundle activated,V- ventricular depolarization Three intervals obtained PA interval-conduction time from SA node to AV node AH interval- represents AV node conduction time HV interval-conduction in bundle of his and bundle branch
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