EKG

Question 1

Differentiate the heart’s response to pressure vs. volume

Answer 1

• Pressure (such as increased afterload from systemic HTN) causes hypertrophy
• Volume overload such as seen in LV dysfunction or shunt causes dilation

Question 2

Describe how hypertrophy changes EKG reads

Answer 2

Hypertrophy = increased muscle mass => increased in signal b/c more channels means more current

Question 3

Answer 3

Saw tooth pattern of atrial flutter

Question 4

Determining rhythm from EKG

(a) Source
(b) Regularity

Answer 4

Rhythm

(a) Source- SA nodal or ectopic? Look if there is a P wave before and in the same direction as each QRS- associated w/ sinus rhythm
(b) Regularity: 1:1 ratio of P-wave to QRS complexes

Question 5

What is an isoelectric lead?

Answer 5

Wave that is travelling at a 90 degree angle to a particular lead won’t create a defleciton => lead is isoelectric to the wave of energy

Question 6

Describe what the letters on an EKG represent

Answer 6

P = atrial depolarization

QRS complex = ventricular depolarization

T-wave = ventricular repolarization

Question 7

EKG findings of acute pericarditis

Answer 7

• concave up ST segment elevation
• PR segment depression
• is not confined to a vascular territory (differentiating factor from STEMI)

Question 8

Differentiate the cause of a positive vs. negative deflection on EKG

Answer 8

A wave traveling towards the (+) lead causes an upwards deflection on EKG

Wave traveling away from the (+) lead causes downward deflection

Question 9

What do EKG leads measure?

Answer 9

EKG waveform is a measurement of the surface voltage btwn 2 leads

Question 10

Describe technique for eyeballing HR on EKG

ex: Give the rate

Answer 10

Each dark vertical line count: 300 –> 150 –> 100 –> 75 –> 60 –> 50

ex: Rate around 90-95 (under 100 b/c just under 3 large boxes separate QRS complexes)

Question 11

PVC on EKG

Answer 11

See a wide bizarre QRS followed by a compensatory pause (and next P-wave is buried w/in the widened QRS)

Question 12

Locate the 6 precordial leads

Answer 12

V1 right of sternum at 4th intercostal space

V2 left of sternum at 4th intercostal space

V3 btwn sternum and midclavicular on left

V4 right below nipple line on left

V5 btwn midclavicular and axillary

V6 6th intercostal space axillary space

Question 13

RVH on EKG

Answer 13

Large R-wave in V1 (and less so in V2 and V3)

Question 14

What does the PR interval represent?

Answer 14

PR interval = delay of the signal thru the AV node

-makes sense b/c the P-wave is the SA node causing atrial contraction then the QRS is when the signal has gotten the AV node and the ventricles contract

Question 15

Locate the 6 basic EKG leads

Answer 15

Basic leads: I, II, III

Augmented leads: AVR, AVL, AVF (on right ankle)

Question 16

Rule of thumb for normal axis

Answer 16

Up in 1, Up in AVF

-b/c axis should be pointing down and left (1+ is to the pt left, AVF + is pointing down)

Question 17

When are V7 and V8 added?

Answer 17

V7 and V8 can be added posterior to cover left circ territory

Question 18

How does atrial hypertrophy appear on EKG

(a) Best seen in which lead
(b) RA vs. LA hypertrophy

Answer 18

Atrial hypertrophy => biphasic P-wave, best seen in V1

(a) V1 b/c is mostly right over the RA and is highest placed lead in the chest
(b) RA is closer to V1 => see RAH as large initial spike and see LA hypertrophy as second increased spike

Question 19

What is a PVC?

Answer 19

Premature ventricular complex = early beat from a focus in the ventricle fires on its own then spreads

Question 20

Which leads represent the territory of

(a) RCA
(b) LAD
(c) LCX

Answer 20

(a) RCA territory represented by II, III, aVF (inferior leads)
(b) LAD represented by V2,3,4 (anterior leads)
(c) Left circ represented by I, aVL, V5, V6 (lateral leads)

Question 21

LVH on EKG

Answer 21

LVH criteria : heigh of S in V1 + height of R in V5 > 35 mm

-large S-wave in V1, large R-wave in V5

Question 22

Precise measurements of time on EKG

(a) large box
(b) Small box

Answer 22

On EKG

(a) Large box = 200 msec = .2 sec
(b) Small box = 40 msec = .04 sec
- 5 small boxes to a large box

Question 23

Describe what territory of the heart the precordial leads cover

Answer 23

V1-V2 are over the RV

V4,5,6 are over the LV primarily

V3 = transition lead approximately over the intraventricular septum

Then add V7 and V8 to cover mor eof the LV since most of the LV lies posteriorly

Question 24

Which are the

(a) Lateral
(b) Inferior
(c) Anterior

leads

Answer 24

(a) Lateral leads = I, aVL, V5, V6
- Left circ distribution
(b) Inferior leads = II, III, aVF
- RCA distribution
(c) Anterior leads = V3,V4
- LAD distribution

Question 25

What is the axis on EKG? What is it’s significance?

Answer 25

Axis = sum of the vectors produced by all the EKG leads

-basically see if the summative vector is pointing down and left (aka from the SA node to the Purkinje fibers)