PR Interval (lec 7)

Question 1

PR Interval reflects?

Answer 1

depol of heart from SA node thru atria, AV node, His-Purkinje (initiation of QRS)

Question 2

PRI begins?

ends?

Answer 2

start of P Wave

start of Q Wave

Question 3

PRI duration?

Answer 3

0.12 - 0.20 sec

Question 4

PRI abnormal if?

Answer 4

shorter
longer
absent
variable

Question 5

Short PRI occurs when impulse originates where? (3)

Answer 5

1) impulse originates in atria close to AV jxn
2) originates in AV jxn
3) originates in supravent site, travels thru abnormal accessory pathway to vents (preexcitation)

Question 6

Long PRI occurs from?

(U) caused by?

Answer 6

delay in impulse thru AV node

1stº AV block

Question 7

Variable PRI occurs from? (2)

Answer 7

1) wandering atrial pacemaker (U) w/i normal range)

2) 2nd degree AV block (PR intervals get progressively longer until QRS is dropped, cycle repeats)

Question 8

Absent PRI from atrial flutter looks like?

Answer 8

sawtooth

Question 9

Absent PRI from 3rd degree AV heart block appears as?

Answer 9

(U) wide QRS
artia and vents beat independent of ea other,
(U) are regular in relation to themselves (march out)