17. Normal ECG

Question 1

x axis of ECG:

• 1 large box
• 1 small box

Answer 1

lg: 0.2 s
sm: 0.04s

Question 2

y axis of ECG:

• 1 large box
• 1 small box

Answer 2

lg: 0.5 mV
sm: 0.1 mV

Question 3

in what leads in the P wave upright?

inverted?

variable?

Answer 3

upright: 1, 2, V4-V6, AVF
inverted: AVR
variable: 3, AVL, chest leads

Question 4

what is the normal duration for PR interval

Answer 4

0.12 - 0.2 s (3-5 sm boxes)

Question 5

what is the normal duration of QRS complex

Answer 5

0.05 s - 0.10 s (1-2.5 sm boxes)

Question 6

what is the upper limit duration for a Q wave

Answer 6

0.03 s (less than 1 sm box)

should be narrow and small

Question 7

in what leads is ok normal for the Q wave to be 1-2 mm?

Answer 7

1, AVL, AVF, V5, V6

Question 8

what is a normal ST elevation?

what does an abnormal elevation indicate?

Answer 8

not more than 1 mm (1 sm box) in standard leads, 2 mm (2 sm boxes) in chest leads

subepicardial or transmural injury/ischemia

Question 9

what is a normal ST depression>?

what does an abnormal depression indicate?

Answer 9

1/2 mm (1/2 sm box)

subendocardial injury/ischemia

Question 10

in what leads in the T wave upright?

inverted?

variable?

Answer 10

upright: 1, 2, V3-V6
inverted: AVR
variable: 3, AVL, AVF, V1, V2

Question 11

what is the upper limit of height for T wave

Answer 11

standard: <5 mm (1 lg box)
chest: <10 mm (2 lg boxes)

Question 12

what do abnormal T waves indicate

Answer 12

• ischemic patterns (associated with inverted or tall upright T waves)
• hyperkalemia

Question 13

what do abnormal ST segments indicate

Answer 13

pattern of injury

Question 14

what do abnormal Q waves or QRS complexes indicate

Answer 14

pattern of necrosis or infarction

Question 15

what do broad notched p waves, taller in I than III, indicate

Answer 15

p- mitrale

left atrial enlargement; left atrium is dilated and potentially scarred, lending to the bifid nature of the P wave, and the characteristic “M” pattern

Question 16

what do flat P waves in I with tall, pointed P waves in II and III indicate

Answer 16

p- pulmonale

right atrial enlargement, p wave > 2.5 mm

Question 17

what do inverted P waves in II and III, with short PR interval indicate

Answer 17

AV junctional rhythm

Question 18

a prolonged PR interval indicates what pathology

Answer 18

• AV block d/t coronary or rheumatic disease

- hypterthyroidism

Question 19

a shortened PR interval indicates what pathology

Answer 19

• AV junctional or low atrial rhythms
• wolff parkinson white syndrome
• lown ganong levine syndrome

Question 20

what are the best leads for reading p-waves

Answer 20

II and V1

Question 21

how do you evaluate rhythm

Answer 21

• is the a P wave before every QRS and vice versa
• look at PR interval (prolonged –> AV block)
• look a QRS interval (prolonged –> BBB)

Question 22

in what diagnoses would you see a P wave following a QRS complex

Answer 22

• SVT

- junctional rhythm

Question 23

in what diagnoses would you not see P waves

Answer 23

• afib (350-500 bpm)
• atrial flutter
• junctional or ventricular escape rhythms
• junctional tachycardia
• VTACH