EKG - Ischemia

Question 1

Coronary Artery Disease

Answer 1

Coronary Artery Disease (CAD) is the
development of atherosclerotic plaques in
the walls of the coronary arteries.

Question 2

CAD leads to stenosis of these very
important arteries, which can result in
_____

Answer 2

decreased blood supply to the area of the
myocardium supplied by that artery.

Question 3

____ is the single largest killer of men and
women in the United States

Answer 3

Coronary artery atherosclerosis

Question 4

The normal ST segment should be in line with _____

Answer 4

the isoelectric line and is the
starting point of early ventricular repolarization.

Question 5

ST Segment Elevation

Answer 5

○ Defined as elevation of 1 mm (1 small
box) or more above the isoelectric line.
○ Elevation may suggest infarction,
pericarditis, hypothermia, etc

Question 6

ST Segment Depression

Answer 6

○ Defined as depression of 1 mm (1 small box) or more below the isoelectric line.
○ Depression may suggest reciprocal changes of infarction, acute ischemia, digoxin toxicity,
hypokalemia, etc

Question 7

If the T wave is inverted, this may suggest

Answer 7

■ Ischemia
■ Infarction
■ Drug effects

Question 8

A twelve-lead EKG recorded during an anginal, ischemic event may show

Answer 8

ST Segment Depression and/or T Wave Inversion.

Question 9

ST Depression has several different appearances

Answer 9

Question 10

Although the resting EKG may be normal, increased demands
of exercise may bring out evidence of ischemia and subclinical CAD with _____

Answer 10

Stress testing

Question 11

Infarction on EKG

Answer 11

Infarction occurs when ischemia becomes so significant that myocardial cell death starts to occur due to lack of oxygen and nutrients
● In most infarctions, the EKG will initially reveal the diagnosis
● Some of the characteristic EKG changes during infarction include T Wave
changes, ST Elevation, reciprocal ST changes, and pathologic Q Waves.

Question 12

Some of the characteristic EKG changes during infarction include

Answer 12

T Wave changes, ST Elevation, reciprocal ST changes, and pathologic Q Waves

Question 13

The Evolution of EKG Changes During an AMI:

Answer 13

A- Normal EKG prior to the onset of arterial
blockage.
B- Hyperacute T Waves can occur early
during the MI. If only T Wave inversion is
seen, this only indicates ischemia and is
not diagnostic of acute MI.
C- ST Segment Elevation develops. This
signifies myocardial injury
D- ST Elevation starts to decrease.
E- Q Waves are present, ST Segment has returned to
normal, and T Waves are inverted.
F- T Waves may return to normal over months-years.

Question 14

Normal vs Pathologic Q Waves:

Answer 14

○ Small Q Waves can be seen in the left lateral leads (I, AVL, V5, V6) and occasionally in the inferior leads (esp II and III) in perfectly normal hearts.
○ Pathologic Q Waves generally signify history of infarction and are wider/deeper.
■ Must be greater than 1 mm wide and at least ⅓ the height of the total QRS amplitude

Question 15

STEMI

Answer 15

○ Full-thickness, transmural infarction of the wall.
○ Causes ST elevation in the acute stages.
○ Most result in the development of pathologic Q Waves after (which is why they are also referred
to as Q Wave Infarctions).
○ Will cause elevation of Cardiac Enzymes

Question 16

Non-STEMI

Answer 16

○ Partial-thickness, subendocardial infarction.
○ Does not cause ST Segment elevation, but instead generally presents with persistent ST Depression and T Wave Inversion.
○ Most of the time, there is not enough injury to cause the development of
pathologic Q Waves (So also referred to as Non-Q Wave Infarctions).
○ More difficult to diagnose because not as apparent as ST elevations. Need to
rely more on H&P and Cardiac Enzymes

Question 17

In order to diagnose an MI, EKG changes of infarction must be seen in
____ or more anatomically contiguous leads

Answer 17

two

Question 18

Anatomically contiguous leads

Answer 18

■ Lateral: I, AVL, V5 and V6
■ Inferior: II, III, and AVF
■ Septal: V1 and V2
■ Anterior: V1, V2, V3, and V4
■ Posterior: V7, V8, and V9, or
reciprocal changes in V1-V3
■ Right Ventricle: V4R *

Question 19

If ST changes in just V1 and V2, it is MI of the ____

Answer 19

interventricular septum

Question 20

If the blockage is at the bifurcation of the Left Main, you may see changes
in ____ (anterolateral MI, which is a huge MI).

Answer 20

any of V1-V6

Question 21

Anterior MIs may also show ____ in the precordials

Answer 21

Poor R Wave Progression

Question 22

Limitations of the EKG in diagnosing an infarction

Answer 22

Any underlying cardiac condition that masks the possibility of ST segment changes or development of a pathologic Q Wave by distorting the ST segment and QRS complex will render EKG diagnosis of infarction pretty much impossible
■ Two such conditions exist: Wolff-Parkinson-White Syndrome and Left
Bundle Branch Block.

Question 23

T/F : In the presence of WPW or LBBB, the diagnosis of MI
cannot be reliably made by EKG

Answer 23

T