Cardiovascular system / Electrocardiogram (ECG)

Question 1

What is the ECG/EKG?

Answer 1

Graphic recording/display of the biopotentials generated by the myocardium during the cardiac cycle.

Question 2

How is ECG a vector?

Answer 2

Has the components of magnitude and direction.

Question 3

What is the duration during a normal cardiac cycle?

Answer 3

The duration of ventricular systolic is substantially shorter than that of the ventricular diastole.

Question 4

Definition of waves:

Answer 4

• P wave: Atrial depolarization.
• QRS complex: Ventricular depolarization.
• T wave: Ventricular repolarization.
• U wave: Repolarization of papillary muscles, delayed repolarization of Purkinje fibers.

Question 5

What is PR interval?

Answer 5

Time starts at the beginning of
atrial depolarization to the start of ventricular depolarization.
- Time requires for the impulse, generated by the SA node (beginning of P wave), to initiate the depolarization of the ventricular septum

Question 6

What is the PR segment?

Answer 6

Time starts at the end of atrial
depolarization to the start of
ventricular depolarization.
- The length of this segment is
closely related to the time of
delay for the action potential
passing through the AV node.

Question 7

What is the QRS complex duration?

Answer 7

• Time indicates the duration of ventricular depolarization.
• Associated with the functional integrity of the ventricular conduction system (Bundle of His, bundle branches, Purkinje fibers) and contractile myocardium.

Question 8

What is the ST segment?

Answer 8

• Time between the end of
  ventricular depolarization
  and the beginning of
  ventricular repolarization.
• Also known as isoelectric line.
• For a normal heart, there should have no electrical activity for both the atria and ventricles within the duration of ST segment.

Question 9

What is the QT interval?

Answer 9

• Time starts at the beginning
  of ventricular depolarization
  to the end of ventricular
  repolarization.
• Can be used to roughly
  estimate the duration of
  ventricular action potentials.
• Also directly correlated with heart rate.

Question 10

During short PR interval:

Answer 10

One could consider the Wolff-Parkinson-White syndrome.

Question 11

During long PR interval:

Answer 11

One could consider heart block.

Question 12

What is the normal ECG values of PR interval?

Answer 12

Between 0.12 to 0.20 sec.

Question 13

What is the normal ECG values of QRS complex?

Answer 13

Less than 0.12 sec.

Question 14

For wide QRS:

Answer 14

One could consider bundle branch block, ventricular rhythm, and/or hyperkalemia (hi K+).

Question 15

For tall QRS:

Answer 15

One could consider ventricular hypertophy.

Question 16

What does increased levels of K+ cause?

Answer 16

Partial depolarization of the membrane potentials.

Question 17

How is QTc calculated?

Answer 17

by dividing the QT interval by the square root of the preceding R-R interval.
* QTc = QT / √(RR)

Question 18

What is the ST segment know as?

Answer 18

The isoelectric line.

Question 19

What does the deviation from this isoeletric line indicate?

Answer 19

Acute myocardial ischemia.
- Elevation: Epicardial ischemia
- Depression: endocardial ischemia.

Question 20

What is the T wave?

Answer 20

Usually in upright position.

Question 21

What could inverted T wave indicate?

Answer 21

Inverted T wave could
indicate myocardial
ischemia, intraventricular
conduction delay, or even
an anxiety attack.

Question 22

How many limb leads and chest leads does ECG contain?

Answer 22

• 6 limb leads (I, II, III, aVR,
  aVL, and aVF).
• 6 chest leads (V1-V6)

Question 23

What are leads I. II, &III known as?

Answer 23

Bipolar limb leads.

Question 24

What are leads aVR, aVL, aVF, and V1 to V6 known as?

Answer 24

Unipolar ECG.

Question 25

What are the bipolar limb leads?

Answer 25

Lead I:
→ -ve lead at right arm.
→ +ve lead at left arm.
Lead II:
→ -ve lead at right arm.
→ +ve lead at left leg.
Lead III:
→-ve lead at left arm
→ +ve lead at left leg