ECG readings

Question 1

What is 3rd degree AV block?

Answer 1

No association between the atrium and the ventricle. This shows up on an ECG as P waves that have no pattern of associate with QRS waves.

Question 2

What is 1st degree AV block?

Answer 2

A delay between the SA and AV nodes. This shows on the ECG as a widened PR interval. A normal interval is .12 - .2 seconds, or 3 small boxes on the readout at 25mm/sec write speed.

Question 3

What is a normal P wave showing?

Answer 3

The current that causes Atrial contraction

Question 4

What is a normal Q wave showing?

Answer 4

Current movement through the AtrioVentricular node and begining to stimulate the ventricals

Question 5

What is a normal R wave showing?

Answer 5

Current movement across the ventricles

Question 6

What is a normal S wave showing?

Answer 6

Final stimulation of the ventricles

Question 7

What is a normal T wave showing?

Answer 7

Repolarization moving back across the heart tissue. Remember that the ECG shows the absolute difference between the leads.

Question 8

What leads go with which angle?

Answer 8

For RLF, the letter corresponds with the patients body. Right, Left and Feet.

Recall that a postive QRS for a lead means that the impulse is traveling in that direction. Negative is traveling away, and no impules is perpendicular in either direction, or simply non existant.

Question 9

Identify phases 0-4 for each

Answer 9

Note that the nodal phases are similar but lack stage 1 and 2

Question 10

Describe the phases (0-4) of a ventricular action potential based on ion movement

Answer 10

0 - Fast sodium channels open allowing for rapid influx and depolarization spike.

1. The Fast Na+ channels close, Voltage gated K+ channels begin to open to reset the potential, stopping the upward movement, and beginning rapid decent.
2. The initial K+ gate (I_k1) Shuts, slowing repolarization. Slow Na and Ca channels open allowing influx causing the plateu
3. K+ channels remain open as evertyhing else closes, allowing repolarization.
4. Resting phase. (in nodal cells this phase is “leaky” which is the cause of self-excitation

Question 11

What are these?

Answer 11

Bule is the Absolute refractory period. No additional stimulous can trigger action.

Green is the relative refractory period, where a strong stimulation can counter the repolarization action and trigger a new action potential.

Red is the supranormal period where the overall ion balance and gate configuration will allow a smaller than normal stimulous to trigger action.

Question 13

What is an ECG lead axis?

Answer 13

Lead axis is defined as the direction from the negative electrode to the positive electorde.

Question 14

Define and describe Einthoven’s triangle

Answer 14

Question 15

How is cardiac depolarization resolved onto a lead axis?

Answer 15

The amount of a depolarization vevtor that is parallel to the lead is registered.

Question 16

What is a mean cardiac vector?

Answer 16

The vector sum of all cardiac depolarizations occuring at the time of measurement.

Question 17

What currents underlie the plateau phase of the ventricular action potential? How are increases or decreases in these currents manifest on the ecg?

Answer 17

The plateau phase has minor Na+ influx, Ca++ influx and K+ efflux.

If the Efflux current is expidited, or the influx currents reduced, the QRS portion of the ECG should be shortened.

If the influx is extended, or the efflux reduced, than the QRS should be lengthened.

Question 18

What is RRAIM?

Answer 18

Rate

Rythem

Axis

Interval

Morphology

The systematic approach to analysing ECG

Question 19

What is the rapid way to calculate heart rate?

Answer 19

Find the first QRS peak, and start counting large boxes to the next peak.

1= 300 bpm

2 = 150 bpm

3 = 100

4 = 75

5 = 60

6 = 50

10 = Lance Armstrong

Question 20

What is the Rapid Axis assessment

Answer 20

Assess the I and II leads for QRS

if: I is (+) and II is (+), then: Normal

if I is (+) and II is (-), then : Left deviation

if I is (-) and II is (+) then: Right deviations

Question 21

Define normal sinus Rhythm

Answer 21

Normal is defined as sequential P-QRS-T waves,** P-positive in II, III and avF,** with normal PR interval at a rate of

60-100 bpm

HR<60 = Bradycardia

HR> 100 = Tachycardia

In actuallity HR’s under 60 are pretty normal in young, fit individuals.

Question 22

What are normal PR, QRS and QT intervals?

Answer 22

PR - (not PQ because Q is often hard to see) is .12-.2 seconds, or 3 small boxes. this can be longer in healthy young people.

QRS - usually .06-.1 seconds, less than 3 boxes.

Q-T intervals are 0.35 seconds, or almost 2 big boxes.