ECG questions and answers| (164 questions) Graded A

Normal ECG Conduction Correct Answer: Frontal and Horizontal Plane (image) Correct Answer: Frontal Plane Correct Answer: 6 limb leads: look at the heart @ a different 30 degree interval the limb leads: BIPOLAR I II III Unipolar limb leads aVRaVLaVF -reference point is in the centre of the Δ Horizontal Plane Correct Answer: CHEST Leads V1-V6 unipolar leads looking into the heart What does an ECG mean? -cellular level Correct Answer: -sum of all the electrical activity of all the cardiomyocytes What does the ECG mean? -myocardial level Correct Answer: P wave Correct Answer: atrial depolarization -Abnormal axis indicates ectopic atrial pacemaker - Abnormal morphology or duration indicate RA or LA pathology PR interval Correct Answer: The PR interval represents the time from the start of atrial depolarization to the start of ventricular depolarization. It includes the delay in conduction that occurs at the AV node. The PR interval P.50 normally lasts from 0.12 to 0.2 seconds -Short PR interval indicates accessory AV pathway - Long pathway indicates conducting tissue disease (AV node/His) FLAT LINE: but really its not flat but because we cant reach the AV node with electrodes (small structure) Q wave Correct Answer: septal depolarization left-right direction -Pathological (large) q wave indicates myocardial damage - usually old infarct Septal Depolarisation Correct Answer: Usually from left side to right side that's why the Q wave is negative R wave Correct Answer: Ventricular Depolarization Too large, or wrong axis: may indicate hypertrophy. Too small: may indicate damage Big R wave as the impulse moves from the back to the front of the heart (towards electrodes) The amplitude of the QRS complex is much greater than that of the P wave because the ventricles, having so much more muscle mass than the atria, can generate a much greater electrical potential. S wave Correct Answer: remaining ventricular depolarization Prolongation of QRS complex indicates delay in conduction within ventricle, including bundle branch block ST segment Correct Answer: ventricular systole: usually horizontal or gently up-sloping in all leads. It represents the time from the end of ventricular depolarization to the start of ventricular repolarization ST elevation may indicate myocardial infarction or pericarditis. ST depression may indicate ischaemia. T wave Correct Answer: ventricular repolarisation: Unlike depolarization, which is largely passive, repolarization requires the expenditure of a great deal of cellular energy the membrane pump) Twave is highly susceptible to all kinds of influences, both cardiac and noncardiac (e.g., hormonal, neurologic), and is therefore variable in its appearance. The amplitude, or height, of a normal T wave is one third to two thirds that of the corresponding R wave. Inverted T wave seen in myocardial infarction and ischaemia. Prolonged T wave indicates delayed repolarization Local Electrograms VS Surface ECG Correct Answer: U wave Correct Answer: a wave on the cardiac cycle that indicates an immature cardiovascular system or an electrolyte imbalance little blip Interval Times Correct Answer: PR: from P to Q (some machines dont have a Q wave) Systematic Approach to Interpreting 12 Lead ECG Correct Answer: 1. Rate 2. QRS axis (I, aVF) 3. Rhythm: PR relationship 4. QRS width (BBB), voltage (LVH) 5. Ischaemia: Q, ST, TWI 6. QT interval 7. Previous ECG fro comparison ECG Graph paper Correct Answer: 1. Amplitude (1mV/cm) 2. Time 25mm/sec 3. Small boxes= 40msec X 0.1mV 4. Large box= 0.2sec x 0.5mV 1. RATE Correct Answer: HR= 300/(# of large boxes" 2. AXIS; frontal plane Correct Answer: 6 limb leads Correct Answer: The frontal plane is a coronal plane. The limb leads view electrical forces moving up and down and left and right on the frontal plane Angle of orientation Correct Answer: for each lead a line from -ve to +ve and the angle superimposing on the 360 circle of the frontal plane Lead I Correct Answer: is created by making the left arm positive and the right arm negative. Its angle of orientation is 0°. Lead II Correct Answer: is created by making the legs positive and the right arm negative. Its angle of orientation is 60°. Lead III Correct Answer: is created by making the legs positive and the left arm negative. Its angle of orientation is 120°. Augmented Leads Correct Answer: -A single lead is chosen to be positive, and all the others are made negative, with their average essentially serving as the negative electrode -called augmented because the EKG machinery must amplify the tracings to get an adequate recording In AUGMENTED one lead is compared with the mean of all the others Lead aVL Correct Answer: is created by making the left arm positive and the other limbs negative. Its angle of orientation is -30°. Lead aVR Correct Answer: is created by making the right arm positive and the other limbs negative. Its angle of orientation is -150°. Lead aVL Correct Answer: is created by making the legs positive and the other limbs negative. Its angle of orientation is +90° All the views from the 6 limb leads Correct Answer: Inferior Leads Correct Answer: Leads II, III, and AVF most effectively view the inferior surface of the heart. The inferior surface, or wall, of the heart is an anatomic term for the bottom of the heart, the portion that rests on the diaphragm. This is the region suppplied by the right coronary artery Left Lateral Leads Correct Answer: L