sinus rhthms

Question 1

normal sinus rhythm

Answer 1

rate: 60-100bpm
rhythm: regular regular
p wave: present
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)

*Normal P wave axis: P waves should be upright in leads I and II, inverted in aVR

Question 2

sinus arrhymia

Answer 2

rate: 60-100bpm
rhythm: varies with respiration
p wave: present
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)

Question 3

sinus bradycardia

Answer 3

rate: <60bpm
rhythm: regulary-regular
p wave: present
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)

**Note the prominent U waves in the precordial leads, a common finding in sinus bradycardia.

Question 4

Sinus tachycardia

Answer 4

rate: >100bpm
rhythm: regulary-regular
p wave: present
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)

**With very fast heart rates the P waves may be hidden in the preceding T wave, producing a ‘camel hump’ appearance.

Question 5

sinus arrest

Answer 5

rate: varies
rhythm: irregular
p wave: present except for pause
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)

Question 6

sinus block

Answer 6

rate: varies
rhythm: regulary-irregular
p wave: present except for “dropped beat”
P:QRS ratio: 1 to 1
PR interval- normal
qrs widtch: <120 ms (0.12 seC)