ECG Extra

Question 1

What is an ECG?

Answer 1

• Provides a record of the net cardiac electrical activity measured between two points on the body surface as it changes with time during the cardiac cycle
• Records the net voltage difference between two points on the body surface, which is the product of the summation of many weak AP’s in the individual cells of the heart

Question 2

ECG is the primary clinical tool for:

Answer 2

• Detection and diagnosis of cardiac arrhythmias and myocardial injury
• Detects disturbances in heart rate, rhythm, and/or wave-front propagation

Question 3

What interval corresponds with Ventricular Filling?

Answer 3

P-Q interval

Question 4

What interval corresponds with Ventricular Systole?

Answer 4

Q-T

Question 5

What interval corresponds with isovolumetric relaxation in early ventricular diastole until atrial contraction? AKA Quiescent phase

Answer 5

T wave to beginning of the next P wave

Question 6

What is Automaticity? And which Specialized cell has the fastest rate?

Answer 6

-It is the property of the specialized cells to spontaneously fire Action Potentials

• SA node has the fastest rate and is therefore the dominant pacemaker.
• Other specialized cells are latent pacemakers

Question 7

What is the Absolute Refractory period

Answer 7

• The Time during which the working myocardial cells cannot be stimulated to fire another action potential through most of the action potential
• This precludes summated or tetanic contractions from occurring

Question 8

What is the relative refractory period?

Answer 8

-Time where myocardial cell can fire an action potential, but it requires a greater than normal stimulation

Question 9

What key ions go in during Phase 0 of a Specialized/pacemaker cell Action potential?

Answer 9

Ca2+

Question 10

What key ions exit during Phase 3 of specialized/pacemaker cell Action potential?

Answer 10

K+

Question 11

What ions are going in during Phase 4 of specialized/pacemaker cell action potential?

Answer 11

Na+ and Ca2+

Question 12

The strength of a cardiac muscle contraction is directly proportional to what?

Answer 12

Intracellular Ca2+ concentration

Question 13

What is a Lead?

Answer 13

The electrical potential difference between two electrodes.

Question 14

What ECG wave intervals are normally isoelectric?

Answer 14

• PR

- ST

Question 15

Ventricles contract during which ECG interval?

Answer 15

ST segment

Question 16

True or False: The AV node is the ONLY electrical link between the atria and the ventricles.

Answer 16

True

Question 17

What are 6 indications of a Normal Sinus ECG?

Answer 17

1. Frequency of QRS complexes is approximately 1 per second

2. Shape of the QRS complex is normal (R upright) in Lead II with a duration of