L15 and L16 ECG I and II PDF

ECG I & II Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae COLLEGE OF MEDICINE List the limb and chest leads Describe normal ECG waves and intervals. Explain how to determine heart rate from an ECG tracing. List the clinical significance of ECG Develop a systematic appro...

ECG I & II Dr. Ghada Elgarawany Assistant professor of Medical Physiology www.gmu.ac.ae COLLEGE OF MEDICINE List the limb and chest leads Describe normal ECG waves and intervals. Explain how to determine heart rate from an ECG tracing. List the clinical significance of ECG Develop a systematic approach to ECG interpretation. Electrocardiogram Electrocardiogram (ECG) Definition: recording of potential changes that are generated by heart during cardiac cycle and transmitted to the surface of the body Electrocardiograph Apparatus ECG recording ECG leads Chest leads Limb leads Bipolar limb lead I, II& III Unipolar limb lead aVR, aVL & aVF Unipolar chest lead V1 to V6 ECG Leads 12 leads used in the recording of ECG Limb leads: Bipolar limb leads: Lead I, Lead II, Lead III Unipolar augmented limb leads : aVR, aVL, aVF Precordial or Chest Leads V1, V2, V3, V4, V5, V6 1. Bipolar recording: Using two active electrodes 2. Unipolar recording: Using one electrode Bipolar Limb leads Lead I: Record potential difference between Right arm (Negative) and Left arm (Positive) (L-R) Lead II: Record potential difference between Right arm (negative) Left leg “foot” (positive) (F-R) Lead III: Record potential difference between Left arm (Negative) and Left leg “foot” (positive) (F-L) Einthoven's triangle & Law This triangle illustrates that the two arms and left leg form apices of a triangle surrounding the heart Einthoven's Law: Voltage in lead II= Voltage in lead I + Voltage in lead III Unipolar augmented Limb leads aVR lead: when it record the electric changes from the right arm. aVL lead: when it record the electric changes from the left arm. aVF lead: when it record the electric changes from the left leg “foot” ECG recorded from Limb leads Chest leads ECG recorded from Chest leads Unipolar (limb or Chest)Leads aVL aVR V1 Left 4th intercostal space border of the sternum V2 th intercostal space mid V3 Between V2Left and5V4 th V6 Right 4 intercostal space border axillary line V4 V5 of the sternum Left 5th intercostal space anterior axillary line Left 5th intercostal space midclavicular line aVF 15 ECG Waves Use Lead II for comment on ECG P wave ✓It is positive wave. ✓It is due to Atrial Depolarization and occurs just prior to atrial contraction. ✓Duration: is 0.12 sec ✓Voltage: 0.1 and 0.3 millivolts ✓Atrial Repolarization is not recorded as it is masked by QRS complex +ve 0 -ve ECG Waves QRS Complex: ✓R is positive and Q & S are negative waves. ✓QRS is due to Ventricular Depolarization ✓Q wave is due to depolarization of interventricular septum. ✓R wave is due to depolarization of The apex and ventricular wall. ✓S wave is due to depolarization of posteriobasal part of the left ventricle and the pulmonary conus. ✓Its duration is 0.08 – 0.1 sec. ✓Voltage: 1.0 to 1.5 mv (Lead II) ECG Waves T wave ✓It is a positive wave. It is caused by Ventricular Repolarization ✓Its duration is 0.12 – 0.16 sec ✓Voltage: 0.2 and 0.3 mv. U wave ✓ Small +ve wave. ✓ It may be due to repolarization of the papillary muscles. U ECG Intervals and segments P-R interval : ✓beginning of P wave and beginning of QRS complex ✓It is around 0.16 Sec (100 Sinus Bradycardia 1500/27= 55 HR: < 60 Rhythm Regular: if R-R interval has equal distance along ECG Irregular: if R-R interval has Not equal distance along ECG Axis of the heart The cardiac axis refers to the general direction in which the heart depolarizes Normal Axis from -30˚ to +90 ˚ +ve +ve -ve -ve +ve +ve Normal Axis Right Axis Deviation Left Axis Deviation Causes of Abnormal Axis Right Axis Deviation Left Axis Deviation Right Ventricular hypertrophy Left Ventricular hypertrophy Right Bundle Branch Block Left Bundle Branch Block Infant and Thin people Obese Right Ventricular load ( Pulmonary Embolism and COPD) Mechanical Shift (Ascites, Pregnancy, and abdominal tumors) Clinical significance of ECG To detect 1. Heart rate & rhythm 2. Axis of the heart 3. Size of the heart 4. Abnormal rhythm and conduction 5. Ischemic damage of the heart Review Questions Comment on following ECG: Rate Rhythm Axis Waves (duration and voltage), segments and intervals Summary List the limb and chest leads Describe normal ECG waves and intervals. Explain how to determine heart rate from an ECG tracing. List the clinical significance of ECG Develop a systematic approach to ECG interpretation. Learning Resources John E. Hall PhD and Michael E. Hall MD, MS )2021): Guyton and Hall Textbook of Medical Physiology ,14th edition, Chapter, 13 ,168-157 https://www-clinicalkey-com.gmulibrary.com/#!/content/book/3-s2.0B9780323597128000138?scrollTo=%23top https://exchange.scholarrx.com/brick/normal-ecg Power-point presentation in the Moodle. www.gmu.ac.ae COLLEGE OF MEDICINE