ECG Leads

Which one of the following descriptions or statements about an electrocardio-

gram (ECG) is NOT correct?

• A. It is a record of the voltage changes (as measured at the body surface) due

  to the depolarisation of the muscle cells of the heart as it beats.

• B. The potentials measured by the ECG electrodes are combined in various

  ways to give 12 different ECGs.

• C. The ECG consists of the electrical events that follow the depolarisation of

  ventricles (PQR section), the depolarisation of atria (the S section) and the

  repolarisation of the ventricles (the T section).

• D. The value of the potential difference called “limb lead II” varies with time

  to produce the familiar ECG trace – a graph of voltage vs time.

Which of the following does limb lead II of a typical electrocardiogram

represent?

• A. A graph of the variation of voltage produced by the heart against time.

• B. The voltage at right arm (RA) plus the voltage at left leg (LL).

• C. The electrical events that precede the contraction of the ventricles.

• D. The projection of the electric dipole vector of the heart on the line from left

  arm (LA) to right arm (RA).

What view of the heart do leads V1 and V2 represent?

• A

  Septal

• B

  Lateral

• C

  Anterior

• D

  Inferior

What would it suggest if lead I became more positive than lead II and lead III ?

• A

  Left axis deviation

• B

  Right axis deviation

Which artery is most likely to be affected in the context of ST elevation being present in leads V3 and V4?

• A

  Left circumflex coronary artery

• B

  Left anterior descending coronary artery

• C

  Right coronary artery

• D

  All of the above

If ST-elevation was noted in leads II, III and aVF, what would it suggest?

• A

  A septal myocardial infarction

• B

  A posterior myocardial infarction

• C

  An anterior myocardial infarction

• D

  An inferior myocardial infarction

What is the duration of a normal PR-interval?

• A

  0.04 - 0.12 seconds (1-3 small squares)

• B

  0.08 - 0.12 seconds (2-3 small squares)

• C

  0.12 - 0.2 seconds (3-5 small squares)

• D

  0.04 - 0.08 seconds (1-2 small squares

What view of the heart do leads I, aVL, V5 and V6 represent?

• A

  Septal

• B

  Anterior

• C

  Lateral

• D

  Inferior

What view of the heart do leads II, III and aVF represent?

• A

  Septal

• B

  Inferior

• C

  Lateral

• D

  Anterior

What view of the heart do leads V3 and V4 represent?

• A

  Septal

• B

  Inferior

• C

  Lateral

• D

  Anterior