Sinus Rhythm

Question 1

Criteria of normal SR.

Answer 1

60-100 bmp
Regular
QRS <120ms
P before QRS and QRS after P
Up in II and down in aVR

Question 2

Normal P wave

Answer 2

Size: P < 2,5mm high, < 120ms wide
– Lead II: shape consistent and round, small notch acceptable
– V1: biphasic, both portions equal in size and duration

Question 3

Normal SR segment

Answer 3

best seen in rhythm strip = PR segment on baseline

Question 4

Normal PR interval

Answer 4

PR interval 120-200ms duration
– constant/fixed from cycle to cycle

Question 5

Normal QRS Complex

Answer 5

Width <120ms
– Axis: 0º (<-30º) to 90º
– Morphology: small R in V1, Tall R in V6, no Qs in V1-V3
– Q waves < ¼ of R, < 40ms wide, not in [II + III + aVF]
– Size:
R in V6 < 25mm
S in V1 < 25mmm
[S in V1] + {R in V5/V6] < 35mm

Question 6

Normal Q wave

Answer 6

Q absent in V1-3, may be present in left-sided
leads: I, II, aVL and V5-6 (always <40ms and <1mm)

Question 7

Normal ST segment

Answer 7

ST segment on isoelectric line

Question 8

Normal QT interval

Answer 8

QT < ½ of R-R interval

Question 9

Normal T wave

Answer 9

– limb leads: follows polarity of QRS
– Chest leads: neg in V1/V2 but thereafter positive
– Tip: usually neg in aVR, III and V1