ECG 1: Overview

Question 1

routine speed of ECG machine

Answer 1

25 mm/sec

Question 2

segment vs interval

Answer 2

an interval contains a wave
e.g.,PR interval contains P wave
whereas a segment does not
e.g., ST segment, TP segment

It’s the TP segment that actually determines isoelectric line in ECG.

Question 3

remark on R wave and S wave across V1-V6

Answer 3

R wave should progress in amplitude across V1-V6 due to more left ventricular forces while the S wve becomes less deep.

Question 4

QT interval is best determined where?

Answer 4

best determined in the lead with the longest QT interval (usually V2 or V3)
and without a U wave

Question 5

normal duration of QTc

Answer 5

Male: 390-450 msec
Female: 390-460 msec

Question 6

Formula for QTc

Answer 6

Bazett’s formula:
QTc = QTa / sqrt of R-R interval

ex:
= 0.32 secs / sqrt of 0.48 secs
=0.32 / 0.69
=0.46 secs

Question 7

Used as reference point for ST elevation

Answer 7

J point

Question 8

Normal PR interval

Answer 8

120-200 ms (3-5 small boxes)

Question 9

Shortened PR suggests

Answer 9

WPW pattern
1. short PR interval (<120 ms)
2. wide QRS comples (>120 ms)
3. a slurred onset of the QRS, termed a delta wave

Question 10

normal QRS interval

Answer 10

≤120 ms