5 - EKG (Kim)

Question 1

Where is the current generated in cardiac excitation that is read by EKG?

Answer 1

Extracellular fluit

Question 2

What type of value is the quantity that the EKG measures?

What is the average of all these values?

Answer 2

Vector

Has direction and magnitude

Mean Electrical Vector

Like dropping a pebble in a pond, and measuring the sum of all vectors for an average (depends on the electrode)

Question 3

What “node” serves as an electrical ground in the EKG system?

Answer 3

Right-Leg

Question 4

Positions of the Chest Electrodes V1 - V6

Answer 4

V1 - 4th ICS, 2 cm to Right of Sternum

V2 - 4th ICS, 2 cm to Left of Sternum

V3 - Midway b/t V2 and V4

V4 - 5th ICS, Left Midclavicular Line

V5 - 5th ICS, Left Anterior Axillary Line

V6 - 5th ICS, Midaxillary Line

Question 5

Bipolar Limb Leads Polaries (I - III)

Answer 5

I : R Arm (-) L Arm (+)

II : R Arm (-) L Leg (+)

III : L Arm (-) L Leg (+)

Question 6

P Wave

QRS Complex

T Wave

Answer 6

P Wave - Atria Depolarization

QRS - Ventricle Depolarization (Q initial down, R initial up, S second down, or following R)

T Wave - Ventricle Repolarization

Question 7

Label the QRS Complexes

Answer 7

A - QRS

B - RS

C - R

D - QS

E - RSR’

Question 8

Clinical: What may a large Q wave indicate?

Answer 8

Myocardial Infarction

Question 9

From V1 -> V6 what happens to the R Wave?

Answer 9

Becomes progressively taller

Question 10

Clinical: What is the normal mean electrical axis range?

Answer 10

-30 to +90

Question 11

Clinical: Left Axis Deviation of Normal Mean QRS

Clinical: Right Axis Deviation of Normal Mean QRS

Answer 11

Left Axis Deviation:

Inferior Wall MI

Left Anterior Fascicular Block

Left Ventricular Hypertrophy (LVH)

Right Axis Deviation:

Right Ventricular Hypertrophy (RVH)

Acute Heart Strain (massive pulmonary embolism)

Left Posterior Fascicular Block

Question 12

Clinical: What EKG feature may be 1st sign of Ischemia or drug interactions?

Answer 12

T Wave

Very sensitive, reflects electrolyte changes, ischemia, or drugs

Question 13

What wave represents Atrial Repolarization?

Answer 13

Atrial T Wave

Usually obscured by QRS complex, not normally seen

Question 14

Clinical: What is a clinical representation of AV Conduction?

Answer 14

P-R Interval

Question 15

Clinical: What is a clinical representation of Ventricular Conduction?

Answer 15

QRS Complex

Question 16

Clinical: Horizontal ST Segment following QRS Complex?

Answer 16

Atria - Returned to resting potential

Ventricle - Plateau phase of their action potentials (Phase 2)

Question 17

What interval represents Ventricular Depolarization and Repolarization?

Answer 17

QT Interval

Question 18

Summary of EKG Waves, Intervals, and Segments

P Wave

QRS Complex

T Wave

PR Interval

ST Segment

QT Interval*

Answer 18

P Wave - Atrial Depolarization

QRS Complex - Ventricular Depolarization

T Wave - Ventricular Repolarization

PR Interval - Atrial Depolarization + AV Nodal Delay

ST Segment - Isoelectric period of depolarized ventricles

QT Interval - Length of depolarization + repolarization, normalized to 60 bpm–depends on HR

Question 19

Clinical: What is normal for aVR that is unique?

Answer 19

All forces are negative

(+) electrode placed on right arm; electrical conduction traveling away

Question 20

Clinical: What is the normal expectation for all readings in Lead II?

Answer 20

P-QRS-T will all be positive