Intro to ECG Part 3 Flashcards
The junction between the __ and the___t is called the J point:
The junction between the QRS complex and the ST segment is called the J point:
J point?
This image shows J point elevation in lead III:
J point?
This image shows J point depression in lead V3:
J point?
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
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.
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:
absolute position: elevation vs. depression
slope: upsloping vs. downsloping vs. none
shape: flat vs. concave vs. convex
discuss absolute position and slope of the ST segment
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:
discuss the absolute position and slope of the St segment
example of ST depression with no sloping:
analyze the shape of the ST segment
This ECG shows a diffuse J point with ST segment elevation that is concave upward:
analyze the shape of the ST segment
The ST segment can also be concave down which can occur with ST depression.
analyze the shape of the ST segment
The opposite of concave up is convex up.
The T wave should be analyzed after the ST segment. The T wave should be analyzed for:
orientation: upgoing, downgoing (inverted) or biphasic
concordance with QRS
morphology (size and shape)
This is a biphasic T wave. It has 2 “phases”: this one has an initial downgoing deflection followed by an upgoing deflection.
cahracterize T wave
Here is another example of a biphasic T wave where the inverted portion is larger than the upright portion:
two causes of biphasic T waves
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
Inverted T waves are not normal. An exception to this rule is lead __
Inverted T waves are not normal. An exception to this rule is lead aVR
characterize T wave
inverted T wave
is this T wave discordant or concordant
discordant
is this T wave discordant or concordant
Concordant: both QRS and T wave are downgoing (this is common in aVR for normal ECG’s):
These peaked T waves in leads V3-5 are suggestive of __-___ ischemia:
These peaked T waves in leads V3-5 are suggestive of antero-lateral ischemia:
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.
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.
tall (peaked) T waves are seen in leads III and aVF, suggestive of ___ ischemia.
tall (peaked) T waves are seen in leads III and aVF, suggestive of inferior ischemia.
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):
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)
What is this indication of?
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.
what is this an indication of?
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.
which lead doesn’t show the PR inteval elevation which is upsloping and ST segment depression typically seen in pericarditis
the AvR lead
ECG Diagnostic criteria of myocardial ischemia
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)
___ 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.
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.
ECG diagnostic criteria of myocardial infarction:
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:
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
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.
compare the peaked T waves for infarction ve kyperkalemia
- *Infarction peaked T waves:** broad based and asymmetric
- *Hyperkalemia peaked T waves:** narrow based and symmetric
