EKG Interpretation

Question 1

How do you interpret the rate of an EKG (assuming a standard paper speed of 25 mm/sec)?

Answer 1

• 300, 150, 100, 75, 60, 50, 43, 37, 33
• 300, 250, 214, 188, 167, 150 (tachycardias)
• 6 second method

Question 2

What is the criteria for left atrial enlargement?

Answer 2

P wave in lead II longer in duration that 2.5 boxes AND negative part of P wave in V1 greater than 1 box deep or wide

Question 3

What is the criteria for right atrial enlargement?

Answer 3

P wave in lead II is higher in amplitude than 2.5 boxes AND positive part of P wave in lead V1 greater than one box wide or high

Question 4

What is a normal PR interval?

Answer 4

O.12-.20 seconds (approximately 3-5 boxes)

Question 5

What is a normal QRS duration?

Answer 5

<0.10 seconds (3 boxes)

Question 6

What is the formula for the corrected QT interval?

Answer 6

• QT / square root of the preceding RR interval
• Use 0.40 seconds as the normal QT for a HR of 70 BPM…for every 10 above or below 70, subtract or add 0.02 seconds (Example: HR 100 BPM: 0.40-(3 x 0.02) = 0.34
• Normal QT should be less than 50% of the RR interval for heart rates 60-100 BPM in narrow QRS complex rhythms

Question 7

How do you determine QRS axis?

Answer 7

NORMAL = I and avF + or I and II +
LEFT AXIS = I + with avF and II -
RIGHT AXIS = avF + with I -
RIGHT SUPERIOR = I and aVF -

Question 8

What is the criteria for low voltage on EKG?

Answer 8

QRS less than 5mm in the limb leads and less than 10mm in the chest leads

Question 9

What is the criteria for RVH on EKG?

Answer 9

R wave > S wave in V1

RV1 + SV5 > 10.5

Question 10

What is the criteria for LVH on EKG?

Answer 10

R wave > 15mm in any limb lead 
R wave > 11mm in avL
R wave > 25mm in V4, V5, V6
S wave > 25mm in V1, V2, V3
SV1 + RV5 or V6 > 35mm

Question 11

What is the criteria for abnormal Q waves?

Answer 11

• Q wave > 0.02 seconds in leads V2-V3

- Q wave > 0.03 seconds in II, II, aVL, aVF, V4, V5, V6

Question 12

What is the normal T wave morphology?

Answer 12

• Upright in I, II, V3-V6
• Inverted in aVR, V1
• Upright, flat, or biphasic in III, aVL, aVF, V1, V2

Question 13

What are ST-T changes that are suggesting myocardial ischemia?

Answer 13

Horizontal or downsloping ST segments
Biphasic T waves
Abnormally tall, symmetrical, inverted T waves
Associated EKG findings…prolonged QT, prominent U waves, reciprocal T wave changes (“upside down” ST elevation opposite the site of infarction)

Question 14

Multifocal Atrial Tachycardia

Answer 14

• Atrial rate > 100 BPM
• P waves with > 3 different morphologies
• PR, RR, and RP intervals vary

Question 15

Hypokalemia is suggested by what on EKG?

Answer 15

• Prominent U waves
• ST segment depression and flattened T waves
• Increased amplitude and duration of the P wave
• Prolonged QT
• Paroxysmal atrial tachycardia with block, Wenkebach (2 degree AV block), AV dissociation, PVCs, ventricular tachycardia, and ventricular fibrillation