3.2.1. ECG a clinical approach

Question 1

How do you measure heart rate on an ECG?

Answer 1

One QRS ventricular depolarization per large box is 300 bpm (or 1 beat/.2sec * 60 sec/min = 300 bpm), per two boxes is 150 bpm (1 beat/.4 sec * 60 sec/min = 150 bpm and so on…), per three boxes is 100 bpm, four boxes = 75 bpm, 5 boxes = 60 bpm, 6 boxes = 50 bpm. Also, you can take the number of beats on the sheet and multiply by 6 for average heart rate.

Question 2

What is tachycardia?

Answer 2

HR > 100 bpm

Question 3

What is bradycardia?

Answer 3

HR < 60 bpm

Question 4

What’s the rapid approach for evaluating the depolarization axis?

Answer 4

Done normally by looking at QRS with lead I and II if (+) in I and II, then axis is normal if (+) is I and (-) in II, then left axis deviation. if (-) in I, (+) in II, then right axis deviation. Indicates right ventricle abnormally enlarged. Think congenital heart problems to make right ventricle enlarged.

Question 5

How do you know whether the sinus rhythm is normal on an ECG?

Answer 5

1. rate is 60-100 bpm 2. one P wave per QRS 3. PR interval is normal and upright in leads II, III, and aVf

Question 6

What are arrhythmias?

Answer 6

abnormalities of electrical rhythm that result from alterations of impulse conduction, impulse formation, or both

Question 7

What is atrial fibrillation?

Answer 7

When atria beat faster than 300 bpm. no P waves exist. Sinus node is not functioning correctly

Question 8

What is the PR interval?

Answer 8

Corresponds to the time it takes the electrical impulse to travel from the SA node, through the AV node, to the start of ventricular depolarization. Depends on both conduction velocity through the AV node and HR.

Question 9

What are causes of an abnormal QRS interval?

Answer 9

Bundle branch blocks, abnormal depolarization, and myocardial disease.

Question 10

What will give a wide QRS and a negative V1 lead pulse?

Answer 10

Left bundle branch block.

Question 11

What is Wolff Parkinson-White (WPW) syndrome?

Answer 11

If an accessory pathway from the atrium to the ventricle is present (bundle of Kent), electrical impulses bypass the AV node, allowing the ventricle to partially depolarize earlier. This condition has a characteristic delta wave on ECG and may result in a reentry current, leading to supraventricular tachycardia.

Question 12

What are the ECG characteristics of Wolff Parkinson-White (WPW) syndrome?

Answer 12

1. short PR interval ( 100 ms

Question 13

In the x axis of an ECG, how is time measured?

Answer 13

x axis: time is measured 40 msec/small box and 200 msec/large box

Question 14

What is the chart speed during an ECG?

Answer 14

chart speed is 25 mm/ sec or 5 large boxes per sec

Question 15

What does each y axis block on an ECG mean?

Answer 15

y axis: depolarization vector voltage is measured 0.1 mV as one small box

Question 16

To summarize, ECG is recorded on _____ mm graph paper at a speed of _____mm of recording paper per _____. Each _____ (small box) corresponds _____ seconds and 5-mm grid lines indicate _____ seconds.

Answer 16

To summarize, ECG is recorded on 1-mm graph paper at a speed of 25 mm of recording paper per second Each millimeter (small box) corresponds 0.04 seconds and 5-mm grid lines indicate 0.2 second

Question 17

What happens to the blood during atrial fibrillation?

Answer 17

Ultimately, clots develop because of lack of blood movement in atria

Question 18

Describe the length of time of the p wave and what is happening at this time

Answer 18

P wave: .06 - .10 sec Atrial depolarization

Question 19

Describe what causes QT interval?

Answer 19

Prolonged indicates a drug problem or congenital abnormality with cardiac repolarization.

Question 20

Longer PR interval indicates what abnormality in the heart?

Answer 20

Longer than this tells you there is a problem of conduction through the atria. Shorter than this indicates a short from the SA node to the ventricle

Question 21

What does a Sinus Tachycardia EKG look like?

Question 22

What does an atrial fibrillation EKG look like?

Question 23

Normal QRS implies functioning whats?

Answer 23

Right and Left Bundle Branches

Question 24

What does a right bundle branch block look like on an EKG?