Welch Allyn Means ECG Physicians Manual for CP Series Electrocardiographs - User Manual - Manual (Page 23)

MEANS Physicians Manual
Welch Allyn
23
High-lateral infarction
An abnormal Q wave in both leads I and aVL is necessary to diagnose high-lateral infarction.
In this situation the Q wave in I is by nature shallower and shorter than that in aVL. Therefore
the threshold to qualify as an infarct Q is lower in I than in aVL.
A minimum amplitude condition has been built in for the R wave in lead I to prevent the
diagnosis of a high-lateral infarction in pulmonary disease, where a very low R voltage in I
may occur.
Skip tests
if:
Q amplitude in I

70 µV
or Q amplitude in aVL

100 µV
or R amplitude in I < 100 µV
Say:
“high-lateral infarct”
if: Q duration  40 ms in I and aVL
or 35

Q duration in I < 40 ms
and Q duration in aVL

Q duration in I
and Q/R ratio

1/3 in I
or QRS axis  70 
Say:
“probable high-lateral infarct”
if: 35

Q duration < 40 ms and 1/4

Q/R ratio < 1/3 in I
and Q duration in aVL

Q duration in I
or 25

Q duration in I < 35 ms
and Q duration in aVL

Q duration in I
and Q/R ratio  1/3 in I
or QRS axis

70

or Q duration

20 ms and R amplitude

100 µV in I
and Q duration

50 ms and R amplitude

300 µV in aVL
Say:
“possible high-lateral infarct”
if: 25

Q duration < 35 ms and 1/4

Q/R ratio < 1/3 in I
and Q duration in aVL  Q duration in I
or Q duration

20 ms and R amplitude

100 µV in I
and 40

Q duration < 50 ms and R amplitude

300 µV in aVL