ECG PDF

# Electrocardiogram (ECG) ## Content - Definition - Significance of ECG - ECG waves - Waves and Intervals in ECG - Nomenclature of waves in QRS complex - ECG Leads and electrodes - Limb leads and electrode placement - Einthoven's Law - Augmented Unipolar Limb leads - Precordial leads / chest leads...

# Electrocardiogram (ECG) ## Content - Definition - Significance of ECG - ECG waves - Waves and Intervals in ECG - Nomenclature of waves in QRS complex - ECG Leads and electrodes - Limb leads and electrode placement - Einthoven's Law - Augmented Unipolar Limb leads - Precordial leads / chest leads and their placement - MCQS ## Contd. - Anotomical lead grouping - ECG Paper and its features - Normal ECG Parameters - Heart rate calculation - Determining QRS axis - Ten Rules of Normal ECG - Patient Preparation and basic steps of ECG - Artifacts and troubleshooting - ECG had system for continuous monitoring - MCQS ## Lecture Objective After attending this lecture students will: - Be able to define what is ECG. - Be able to understand significance of ECG. - Be able to understand ECG waves and its origin. - Be able to clarify laws and rules of leads formation. - Be able to apply different methods of leads placement. - Be able to distinguish qnatomical leads grouping. - Be able to find heart rate calculation and axis determination. - Be able to interpretate normal ECG. - Be able to conduct ECG test successfully. ## Definition - The electrocardiogram (ECG) is a graphic representation of the electrical events of heart during cardiac cycle. - Each electrical event has a distinctive waveform. - These events are detected and amplified thousand times by ECG machine. - It is painless and harmless investigation. - Electrocardiogram - report / print out from machine. - Electrocardiograph - the machine which does ECG. - Electrocardiography - procedure of obtaining ECG. ## Significance - To diagnose the presence of myocardial ischemia and infarction. - To diagnose cardiac rhythm disorders. - To diagnose the presence of cardiac chamber enlargements. - To detect the electrolyte abnormalities especially kt and cort. - To evalute the effect of treatment on the heart le.g. drugs, thrombolysis, coronary interventions etc. ## Waves in ECG - P - QRS - T - U ## Origin of ECG Waves - P Wave - Atrial depolarization. - Ta - Atrial repolarization (not visible - buried within QRS complex). - QRS Complex - Ventricular depolarization. - T Wave - Ventricular repolarization. ## Waves and Intervals in ECG - RR interval - PQ Segment - PR Interval - ST Segment - QRS Interval - ST Interval - QT Interval ## Nomenclature of Waves in QRS Complex 1. First negative wave is always "q" or "Q"Wave. 2. First Positive wave is always "r" or "R". 3. If there is a second positive deflection within the QRS complex it is called as R' (R prime) and if there is a second negative deflection after the 'R' it is called as 'S' (S prime). 4. Small deflections are designated by small letters "s", "q" and large deflections are represented by large letters "R" "S" "Q". ## ECG Leads - Leads measure the difference in elictrical potential between two points (electrodes). - Bipolar leads: - Two different points on the body. - Unipolar leads! - One point on the body and a virtual reference point with zero electrical potential, located in the centre of the heart. - The standard ECG has 12 leads : - 3 Standard (bipolar) Limb leads - I, II and III - 3 Augmented (Unipolar) Limb leads - QVR, AVL and aVF - 6 Precordial/chest Leads (Unipolar) - V1, V2, V3, 4, 5, 6 ## Electrodes - Electrodes detect the tiny electrical changes on the skin that arise from the heart muscles. - Jelly helps in good electrical contact between electrodes and skin. - For limb leads 4 electrodes are needed. - For chest leads 6 electrodes are needed. - It means total 10 electrodes are placed and there various combinations give 12 leads ECG. ## Limb leads and electrode placement | Lead | Placement | Color | | :---- |:----------------- |:--------------| | RA | Right Arm |Red | | LA | Left Arm |Yellow | | RL | Right Leg | Black | | LL | Left Leg | Green | ### Bipolar leads (Standard limb leads) | Lead | Negative Terminal | Positive Terminal | | :---- |:--------------------- |:-----------------------| | I | Right arm | Left arm | | II | Right arm | Left leg | | III | Left arm | Left leg | #### Standard Limb Leads - Lead I: Right arm to Left arm - Lead II: Right arm to Left Leg - Lead III: Left arm to Left leg ### Einthoven's Law and Triangle - Einthoven's law; Vector sum of lead I and II is equal to lead III - J + Ⅲ = II. ### Augmented Unipolar limb leads - Measures the electrical activity from one limb at a time. - Also called unipolar leads. - avR - aVL - aVF ## Precordial leads / Chest leads V1 - Fourth intercostal space on the right side of sternum V2 - Fourth intercostal space at the left side of sternum V3 - Midway between placement of V2 and V4 V4 - Fifth intercostal space at the midclavicular line. Vs. Anterior axillary line on the same horizontal level as V4. V6 - Mid - axillary line on the same horizontal level as V4 and V5. ### Right Sided Chest leads - RV3 - Same as V3 on right side. - RV4 - Same as V4, but on right side (Right 5 intercostal space in midclavicular line. - RV5 - Anterior axillary line on right side, same horizontal level as RV4. ### Left Posterior leads - - V7 - left Posterior line, same horizontal level as V4-V6. - Vg - Midscapular line (tipos left scapular), same horizontal level as V4-V6 - Ng - Left parasternal line, same horizontal level as V4-V6 ## Arrangement of Leads on the ECG | Lead | Augmented leads | Precordial leads | | :---- |:------------------ |:------------------| | I | avR | V1 | | II | aVL | V2 | | III | aVF | V3 | | | | V4 | | | | V5 | | | | V6 | - Rhythm strip (Lead II, V₁) ## Anatomic groups (Septal leads) | Lead | Augmented Leads | Precordial leads | Placement | | :---- |:--------------------- |:------------------ |:--------------| | I | AVR | V1 | Septal | | | None | V4 | Anterior | | II | aVL | V2 | Septal | | | Inferior | V5 | Lateral | | III | avf | V3 | Septal | | | Inferior | V6 | Lateral | ## Anatomic groups (Anterior leads) | Lead | Augmented Leads | Precordial leads | Placement | | :---- |:--------------------- |:------------------ |:--------------| | I | AVR | V1 | Septal | | | None | V4 | Anterior | | II | aVL | V2 | Septal | | | Inferior | V5 | Lateral | | III | avf | V3 | Septal | | | Inferior | V6 | Lateral | ## Anatomic groups (Lateral leads) | Lead | Augmented Leads | Precordial leads | Placement | | :---- |:--------------------- |:------------------ |:--------------| | I | AVR | V1 | Septal | | | None | V4 | Anterior | | II | aVL | V2 | Septal | | | Inferior | V5 | Lateral | | III | avf | V3 | Septal | | | Inferior | V6 | Lateral | ## Anatomic groups (Interior leads) | Lead | Augmented Leads | Precordial leads | Placement | | :---- |:--------------------- |:------------------ |:--------------| | I | AVR | V1 | Septal | | | None | V4 | Anterior | | II | aVL | V2 | Septal | | | Inferior | V5 | Lateral | | III | avf | V3 | Septal | | | Inferior | V6 | Lateral | ## Type of Electrocardiograph machine ### ECG Machine - Single channel - Multichannel ## The ECG Paper - Graph Paper - Sensitized paper (thermal paper) - Horizontal axis shows time (determined by Paper speed) - Normal Paper speed 25 mm / sec - One small box - 0.04 sec (40msec) - One large box - 0.20 Sec (200 msec) - Vertical axis shows amplitude (determined by gain) - Measured in millivolts - One large box - 0.5 mv ## ECG Calibration - Calibration is detemination of height (Voltage) and Paper speed of ECG Machine. - Voltage of ECG Machine is = 10 mm. - Speed of paper = 25 mm / sec. - 1 mile volt = QRS complex voltage. - At the beginning of the each ECG recording, the electrocardiograph automatically Performs a calibration for o'zsec, recording a srectangu shape with I mv height and 5 mm width on the graph Paper (see image on the right). - Horizontal calibration (5mm) - Vertical (10 mm) ## Normal ECG ## Normal ECG Parameters - Rate = 60 to 100 (beats per minute) - Rhythm = Regular - QRS Axis = -30 degrees to +110 degrees - Pwave = duration less than 120m sec (3 Small squares) - PR interval = 120-200 msec C 3-5 small squaris) - QRS duration = 120 m sec ( 3 small squares) - QT interval = 400msec. ## Heart rate calculation ### Rule of 300 - Rate is calculated by 300 divided by number of large squarus between two consecutive R waves. - Useful in regular heart rate. - Rule of 300: 300 / No. of Large boxes b/w two R wave ### Rule of 1500 - 1500 divided by number of small squarus between two consecutive R waves. - Useful in regular heart rate. - Rule of 1500: 1500 / No. of small boxe b/w two R wave ### 10 Second rule - Number of QRS complex in 10 seconds (50 large squares) multiplied by 6 - 10 Second rule: No. of QRS complex in 10 second (50 large syr) x 6 ### 6 Second rule - Number of QRS complexes in 6 seconds (30 large squares) multiplied by 10. - Useful for erregular ratt - 6 Second rule: No.of QRS complexes in 6 seconds (30 large boxes) x 10 ## Determining QRS axis - Normal QRS axis is from -30° to +110° - Left axis deviation (LAD) = When QRS axis is - 30° to-90° - Right axis deviation (RAD) = When QRS axis is + 110° to +180° - Extreme Right axis deviation (North-west axis) = when QRS axis is + 180° to +270° or - 90° ### Determining QRS axis |Lead I | Lead II | Lead III | Interpretation | |---|---|---|---| | Positive | Positive | Positive | Normal axis | | Negative | Positive | Positive | Right axis deviation | | Positive | Negative | Negative | Left axis deviation | | Negative | Negative | Negative | North West axis | ## Ten Rules of Normal ECG 1. PR interval should be 120 to 200 milliseconds or 3 to 5 small squares. 2. The width of the QRS complex should not exceed 110 ms, less than 3 small squares. 3. The QRS complex should be dominantly upright in leads I and II 4. QRS and T waves tend to have the same general directic in the limb leads 5. All waves are Negative in lead aVR 6. The R wave must grow from V1 to at least V4. The S wave must grow from V5 to at least V3 and disappear in V6 (Normal R wave progression). 7. The ST segment should start isoelectric except in V1 and V2 where it may be elevated. 8. The P wave should be upright in I, II and V2 to V6. 9. No pathologic Q wave in I, II, and V2 to V6. 10. T wave must be upright in I, II and V2 to V6. ## Chamberline's 10 Rules 1. PR interval should be 0.12 - 0.2 Sec (3-5 small sq.) 2. With of QRS should not exceed 0.11 sec (3 small sq.) 3. QRS Should be dominantly upwards in lead I and II 4. QRS and T waves have same diruction in limb leads 5. All waves are negative in lead aVR 6. R wave must grow from V1 to V4 while S wave must grow from V5 to at least V3 and disappear in V6 7. ST segment should start iso - electric except in V4 and V2 where it may be elevated. 8. P wave should be upright in I, II and V2 to V6. 9. No pathologic Q wave in I, II, and V2 to V6. 10. T wave must be upright in I, II and V2 to V6. ## Equipment Needed - Twelve-Leads ECG machine with charged bottery, cables and leads. - Graph paper. - Disposable electrodes (12) - Electrode paste or gel - Alcohol wipes - Pillows - Sheet or drape - Towel and washcloth - Disposable razor ## Patient Preparation - clean hands - Supine position - must be able to lie down comfortably - Explain -Procedwu, duration, Purpose - Privacy - curtains, closedoors, - Female nurse or attendant if patient is female - Expose - chest and limbs. - Remove oil, moisture, excess hair, scrub skin - Apply electrodes, ECG gel | Jelly it needed - Attach Lead wises to electrodes ## Basic setup of Machine - - Switch on. - Connect to Power supply, should have enough battery. - Enter patient data I'details. - Calibration - Paper speed gain. - Accurate ECG bracing on display. - For single channel, at least 2.5 second or 3 QRS complexes per lead. - 12 lead, plus 10 second rhythm strip. - If satisfied, print. - If accurate Print, remove electrodes, wires. - Wipe the jelly off the skin. - Hand over ECG to physician. - Wash hands. - Return machine, replace supplies. ## Limitation of ECG - The ECG reveals the heart rate and rhythm only during the time that the ECG is taken. - If intermittent cardiac rhythm abnormalities are present, the ECG is likely to miss them. - Ambulatory monitoring is needed to record transient arrhythmias, undiagnosed coronary artery disease or other forms of heart disease (False negative results) - Many "abnormalities" that appear on the ECG turn out to have no medical significance after a thorough evaluation is done (false positive risults). ## ECG had system for continuous monitoring - 3 electrode system - 5 electrode system - Mason-liker modification - EAST system. ### 3 Electrode system - White / Red - Black/Yellow - Red/green ### 5 electrode system - White/Red - Black/Yellow - Red/green ### Mason-Liker modification - TMT - Treade-mille stress test ## ECG lead system for continuous monitoring - 3 electrode system - 5 electrode system - Mason-Liker modification - EAST system. ### 3 Electrode system - - White / Red - Black/Yellow - Red/green ### 5 electrode system - - White/Red - Black/Yellow - Red/green ### Mason-Liker modification - TMT - Treade-mille stress test