Intro to ECG Part 3

Question 1

The junction between the __ and the___t is called the J point:

Answer 1

The junction between the QRS complex and the ST segment is called the J point:

Question 2

J point?

Answer 2

This image shows J point elevation in lead III:

Question 3

J point?

Answer 3

This image shows J point depression in lead V3:

Question 4

J point?

Answer 4

After determining if the J point is elevated or depressed, analyze the shape of the J point. Here is an example of J point notching indicated by the blue arrow in lead II: AKA J WAVES

Question 6

note

Analyze the J point for:

absolute position: it can be elevated or depressed

shape: it can be notched or slurred

Make sure that when you analyze an ECG, you pay close attention to the J point. It is a very small region on the ECG, but it plays an important role in helping you diagnose different causes of ST segment elevation. This is important because one cause of ST segment elevation is myocardial infarction, but myocardial infarction is not the only cause of ST segment elevation.

Question 7

The J point can be thought of as the start of the ST segment. The ST segment should be evaluated after the J point is evaluated. Features that are important to analyze in the ST segment include:

Answer 7

absolute position: elevation vs. depression

slope: upsloping vs. downsloping vs. none

shape: flat vs. concave vs. convex

Question 8

discuss absolute position and slope of the ST segment

Answer 8

This ECG has an upsloping ST segment and ST elevation The blue dotted line is the zero degrees baseline. The red dotted line is parallel with the ST segment and is angled/sloped upwards:

Question 9

discuss the absolute position and slope of the St segment

Answer 9

example of ST depression with no sloping:

Question 10

analyze the shape of the ST segment

Answer 10

This ECG shows a diffuse J point with ST segment elevation that is concave upward:

Question 11

analyze the shape of the ST segment

Answer 11

The ST segment can also be concave down which can occur with ST depression.

Question 12

analyze the shape of the ST segment

Answer 12

The opposite of concave up is convex up.

Question 13

The T wave should be analyzed after the ST segment. The T wave should be analyzed for:

Answer 13

orientation: upgoing, downgoing (inverted) or biphasic

concordance with QRS

morphology (size and shape)

Question 14

Answer 14

This is a biphasic T wave. It has 2 “phases”: this one has an initial downgoing deflection followed by an upgoing deflection.

Question 15

cahracterize T wave

Answer 15

Here is another example of a biphasic T wave where the inverted portion is larger than the upright portion:

Question 16

two causes of biphasic T waves

Answer 16

Biphasic waves are not normal. Biphasic T waves can be “up then down”, or “down, then up”.

There are 2 causes of biphasic T waves:

• Ischemia
• Hypokalemia

Question 17

Inverted T waves are not normal. An exception to this rule is lead __

Answer 17

Inverted T waves are not normal. An exception to this rule is lead aVR

Question 18

characterize T wave

Answer 18

inverted T wave

Question 19

is this T wave discordant or concordant

Answer 19

discordant

Question 20

is this T wave discordant or concordant

Answer 20

Concordant: both QRS and T wave are downgoing (this is common in aVR for normal ECG’s):

Question 21

These peaked T waves in leads V3-5 are suggestive of __-___ ischemia:

Answer 21

These peaked T waves in leads V3-5 are suggestive of antero-lateral ischemia:

Question 22

A T wave height is often correlated with the height of the QRS: a bigger QRS = a bigger T wave. T waves are __ in males and get __ with age.

Answer 22

A T wave height is often correlated with the height of the QRS: a bigger QRS = a bigger T wave. T waves are bigger in males and get smaller with age.

Question 23

tall (peaked) T waves are seen in leads III and aVF, suggestive of ___ ischemia.

Answer 23

tall (peaked) T waves are seen in leads III and aVF, suggestive of inferior ischemia.

Question 24

NOTE:

Flattened T waves are a non-specific finding, but may be caused by ischaemia or an electrolyte abnormality such as hypokalaemia. Flattened T waves due to ischemia are usually in a localized region of the ECG, while electrolyte abormalities cause T wave flattening in most or all leads.

Here is an example of flat T waves in V1 (blue arrows) and simultaneous ST depression in V4 and V5 from ischemia (red arrows):

Question 25

Note:

The ECG undergoes 4 stages of evolution with pericarditis.

Stage 1 is the classic “acute pericarditis” description:

ST segment elevation in virtually all ECG leads

ST elevation typically is curved upward (concave or scooped up)

T waves concordant (same direction as) with ST segment elevation

PR segment depression

aVR shows the opposite: ST segment depression, and PR interval elevation

(advanced detail) the ratio of J point elevation to T wave amplitude is > 25% in V5,6

Stage 2 (usually days after onset)

ST segment return to normal

T waves can become flattened or inverted

Stage 3 (2-3 weeks after onset)

T waves are inverted

Stage 4 (weeks to months)

ECG returns to original state

some T wave changes could be permanent (if scar on pericardium develops)

Question 26

What is this indication of?

Answer 26

PERICARDITIS:

Abnormalities of atrial repolarization result in changes to the PR segment; the PR segment becomes depressed (below baseline) with pericarditis. This is called PR segment depression. It is usually downsloping. It occurs about 60% of the time in acute pericarditis.

Question 27

what is this an indication of?

Answer 27

PERICARDITIS
This travelling current causes J point elevation and ST segment elevation. The ST segment elevation it usually not flat: it is curved upward, also called concave upward.

Here we see ST segment elevation in V4 and the ST segment is curved upwards, nearly matching the shape of the blue circle. The blue dotted line indicates the isoelectric baseline.

Question 28

which lead doesn’t show the PR inteval elevation which is upsloping and ST segment depression typically seen in pericarditis

Answer 28

the AvR lead

Question 29

ECG Diagnostic criteria of myocardial ischemia

Answer 29

J point depression

ST segment depression

Inverted T waves

Biphasic T waves (might also be due to hypokalemia)

the findings above occur in 2 anatomically contiguous leads (2 leads from the same area of the heart)

Question 30

___ is a condition of oxygen deprivation that does not result in cell death. ___ is a condition of oxygen deprivation that does result in cell death.

Answer 30

Ischemia is a condition of oxygen deprivation that does not result in cell death. Infarction is a condition of oxygen deprivation that does result in cell death.

Question 31

ECG diagnostic criteria of myocardial infarction:

Question 32

ST segment elevation:
This is a finding that is present is pericarditis, early repolarization, LBBB, and LVH with repolarization changes– not just an MI.

Therefore, the simple present of ST segment elevation is non-specific and the details of the ST segment elevation become useful.

ST segment elevation with infarction will usually contain the following characteristics:

Answer 32

present in 2 or more anatomicaly contiguous leads

often is flat and upsloping (as opposed to curved or concave upward), but can be upsloping or

will be associated with reciprocal ST depression in the “opposite” leads

greater elevation of the ST segment (higher = higher probabilty of infarction). This finding was found to be statistically significant.2

Question 33

Answer 33

Here is an example of ST elevation in leads II, III, and aVF and reciprocal ST depression in leads I, aVL

probably an inferior lead STEMI

Why is this important? Infarction from one occluded vessel would produce a “regional” event within the heart. A process such as early repolarization, pericarditis, LBBB, or LVH would not a localized or regional process. Therefore, reciprocal changes do not exist for these diagnoses and therefore, when reciprocal changes are present, they are strongly suggestive of myocardial infarction, as opposed to a different diagnosis.

Question 35

compare the peaked T waves for infarction ve kyperkalemia

Answer 35

• *Infarction peaked T waves:** broad based and asymmetric
• *Hyperkalemia peaked T waves:** narrow based and symmetric