Ed's EKG Lecture / Final Prep

Question 1

Systematic approach to EKG interpretation.

5

Answer 1

1. ) Analyze the rate
2. ) Analyze the rhythm
3. ) Analyze the P waves
4. ) Analyze the P-R interval
5. ) Analyze the QRS complex

Question 2

The ECG is recorded at a speed of ?

Answer 2

25 mm/sec,

Question 3

voltages are calibrated so that 1 mV =

Answer 3

10 mm in the vertical direction.

Question 4

each small 1-mm square =

Answer 4

0.04 sec and 0.1 mV

Question 5

The P wave represents the wave of depolarization that spreads from the ?

Answer 5

SA node throughout the atria, and is usually 0.08 to 0.1 seconds (80-100 ms) in duration.

Question 6

The brief isoelectric (zero voltage) period after the P wave represents what ?

Answer 6

• the time in which the impulse is traveling within the AV node (where the conduction velocity is greatly retarded)

Question 7

Atrial rate can be calculated by what ?

Answer 7

-determining the time interval between P waves.

Question 8

The period of time from the onset of the P wave to the beginning of the QRS complex is termed the P-R interval, which normally ranges from 0.12 to 0.20 seconds in duration. This interval represents what?

Answer 8

-the time between the onset of atrial depolarization and the onset of ventricular depolarization.

Question 9

If the P-R interval is >0.2 sec, there is an ?

Answer 9

-AV conduction block, which is also termed a first-degree heart block if the impulse is still able to be conducted into the ventricles.

Question 10

The QRS complex represents what?

Answer 10

-ventricular depolarization.

Question 11

Ventricular rate can be calculated by determining

Answer 11

-the time interval between QRS complexes, which is done by looking at the R-R intervals.

Question 12

The duration of the QRS complex is normally ?

Answer 12

0.06 to 0.1 seconds.

Question 13

If the QRS complex is prolonged (> 0.1 sec), conduction is impaired within the ventricles. This can occur with?

Answer 13

bundle branch blocks or whenever a ventricular foci (abnormal pacemaker site) becomes the pacemaker driving the ventricle.

Question 14

ectopic foci nearly always results in ?

Answer 14

impulses being conducted over slower pathways within the heart, thereby increasing the time for depolarization and the duration of the QRS complex.

Question 15

The isoelectric period (ST segment) following the QRS is the time at which ?

Answer 15

-the entire ventricle is depolarized and roughly corresponds to the plateau phase of the ventricular action potential.

Question 16

The ST segment is important in the diagnosis of ?

Answer 16

-ventricular ischemia or hypoxia because under those conditions, the ST segment can become either depressed or elevated.

Question 17

The T wave represents ?

Answer 17

-ventricular repolarization and is longer in duration than depolarization (i.e., conduction of the repolarization wave is slower than the wave of depolarization).

Question 18

U wave may be seen following the T wave This wave represents what?

Answer 18

-the last remnants of ventricular repolarization.

Question 19

Inverted or prominent U waves indicates an underlying pathology or conditions affecting what?

Answer 19

-repolarization.

Question 20

The Q-T interval represents what?

Answer 20

• the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential.

Question 21

QT interval can range from ?

Answer 21

0.2 to 0.4 seconds depending upon heart rate.

Question 22

At high heart rates, ventricular action potentials shorten in duration, which

Answer 22

decreases the Q-T interval.

Question 23

prolonged Q-T intervals can be diagnostic for susceptibility to certain types of

Answer 23

-tachyarrhythmias

Question 24

it is important to determine if a given Q-T interval is excessively long. In practice, the Q-T interval is expressed as a “corrected Q-T (QTc)” by completing the following formula?

Answer 24

(Q-T interval)/(√R-R )

This allows an assessment of the Q-T interval that is independent of heart rate.

Question 25

R-R interval =

Answer 25

(interval between ventricular depolarizations

Question 26

Normal corrected Q-Tc intervals are less than?

Answer 26

0.44 seconds.