Cardiology

  • Electrocardiograms

    (ECGs)

  • Which location on the chest wall is lead V1 connected?

  • 4th intercostal space right sternal edge

  • Which location on the chest wall is lead V2 connected?

  • 4th intercostal space left sternal edge

  • Which location on the chest wall is lead V3 connected?

  • Midway between V2 and V4

  • Which location on the chest wall is lead V4 connected?

  • 5th intercostal space left mid-clavicular line

  • Which location on the chest wall is lead V5 connected?

  • Level of the 5th intercostal space left anterior axillary line

  • Which location on the chest wall is lead V6 connected?

  • Level of the 5th intercostal space left mid-axillary line

  • What is the standard speed of ECG paper?

  • 25 mm per second

  • What is the standard ECG calibration?

  • 1 mV is equal to 10 mm i.e., 10 small squares

  • What duration of time is displayed on a standard ECG?

  • 10 seconds

  • In a regular rhythm division of 300 by the number of large squares between two consecutive R waves allows what calculation?

  • Heart rate

  • In an irregular rhythm heart rate can be calculated by multiplying the number of complexes counted on ECG by which number?

  • 6

  • What is the range for a normal electrical axis in the frontal plane?

  • -30 degrees to 90 degrees

  • If the QRS is positive (upright) in both leads I and II, what is the electrical axis?

  • Normal

  • What time interval corresponds to 1 large square (5 small squares)?

  • 0.2 second

  • What time interval corresponds to 1 small square?

  • 0.04 second

  • How many large squares represent 1 second?

  • 5 large squares

  • How is the PR interval measured?

  • From the start of the P wave to the start of the QRS complex – whether this begins with a Q wave or an R wave

  • What does the PR interval represent?

  • The interval between atrial depolarisation and ventricular depolarisation

  • What is the duration of a normal PR interval?

  • 3-5 small squares i.e., 0.12 – 0.2 second

  • What does the P wave represent?

  • Atrial depolarisation

  • What is the normal duration of the P wave?

  • Less than 3 small squares i.e., less than 0.12 second

  • What is the normal amplitude of the P wave?

  • Less than 2.5 small squares i.e., less than 0.25 mV

  • The P wave may be biphasic in which lead?

  • Lead V1 – initial positive deflection representing right atrial depolarisation and the second negative deflection representing left atrial depolarisation

  • What does the QRS interval represent?

  • Ventricular depolarisation

  • What is the upper limit of normal for the duration of the QRS complex?

  • 0.12 second i.e., 3 small squares

  • What is the first positive deflection of the QRS complex?

  • R wave

  • What does the R wave represent?

  • Depolarisation of the left ventricular myocardium

  • What is the R’?

  • Second positive deflection in the QRS complex (first being the R wave)

  • What is R wave progression?

  • Increase in R wave amplitude (height) on progression across leads V1 to V6 i.e. across the precordium

  • Is the QRS complex duration affected by heart rate?

  • No

  • How is the QT interval measured?

  • From the start of the QRS complex to the end of the T wave

  • What does ‘corrected QT interval’ refer to?

  • QT interval corrected for heart rate

  • What is the upper limit of normal for the corrected QT interval (QTc) in men?

  • ≤ 440 milliseconds

  • What is the upper limit of normal for the corrected QT interval (QTc) in women?

  • ≤ 450 to 460 milliseconds

  • What does the ST segment represent?

  • The interval between the ventricular depolarisation and ventricular repolarisation

  • What does the T wave represent?

  • Ventricular repolarisation

  • What is the J point?

  • The junction between the end of the QRS complex and the start of the ST segment

  • Which section of the ECG waveform is considered a time of electrocardiographic silence?

  • ST segment, occurring after ventricular depolarisation has ended and before ventricular repolarisation has started

  • What term indicates zero potential?

  • Isoelectric

  • What effect does increased heart rate have on the PR interval?

  • Shortened – due to sympathetically mediated enhanced atrioventricular nodal conduction

  • What effect does slower heart rate have on the PR interval?

  • Increased – slower AV nodal conduction due to reduced sympathetic tone or increased vagal input

  • What effect can hyperkalaemia have on the QRS complex duration?

  • Prolonged i.e., broad QRS

  • What effect can hypomagnesaemia have on the QRS complex duration?

  • Prolonged i.e., broad

  • How does a faster heart rate affect the QT interval?

  • QTc interval is shortened

  • How does a slower heart rate affect the QT interval?

  • QTc interval is increased

  • How is the QT interval affected by bundle branch block?

  • Increased

  • What effect can hypocalcaemia have on the QT interval?

  • Prolonged

  • What effect can hypercalcaemia have on the QT interval?

  • Shortened

  • What effect can hypermagnesaemia have on the T wave?

  • Tall and tented

  • Which important arrhythmia can torsade de pointes predispose to?

  • Ventricular fibrillation

  • What effect can sleep have on heart rate?

  • Physiological bradycardia

  • What effect can hypothermia have on heart rate?

  • Bradycardia

  • What electrolyte abnormality may cause U waves?

  • Hypokalaemia

  • What change in heart rate may cause U waves?

  • Bradycardia

  • In which leads can a U wave typically be seen?

  • V2 to V4

  • In a paced rhythm where in relation to the pacing ‘spike’ should the QRS complex be seen?

  • Immediately after the pacing ‘spike’

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