ACS ECG Flashcards
What is the earliest electrocardiographic finding in STEMI?
The hyperacute T wave
A tall and peaked structure that can appear within minutes of the interruption of blood flow and initiation of acute infarction.
What is the structure of the hyperacute T wave in STEMI?
Broad-based and asymmetrical
The ST segment can be elevated at the junction between the QRS complex and ST segment.
What does the hyperacute T wave progress to in typical STEMI?
ST segment elevation
This progression occurs as the infarction advances.
Which conditions can also present with tall T waves besides acute ischemia?
- Hyperkalemia
- Benign early repolarization (BER)
- Left ventricular hypertrophy (LVH)
- Left bundle branch block (LBBB)
- Acute pericarditis
What are the morphologic variations of ST segment elevation in STEMI?
- Flat
- Convex
- Domed
- Tombstoned
- Horizontal or oblique
- Concave or scooped
How is ST segment elevation measured on an electrocardiogram?
In millimeters
One block on the electrocardiographic tracing is equivalent to 1 mm in height.
What is the usual baseline considered for measuring ST segment elevation?
The TP segment
Some advocate using the terminal point of the PR segment.
What is benign early repolarization (BER)?
A common finding in young males with ST segment elevation
It is usually 1 mm or more in men and 1 mm or less in women.
How can one differentiate normal ST segment elevation from pathologic ST segment elevation of STEMI?
ST segment elevation in STEMI is a dynamic phenomenon
ECGs recorded sequentially should show fluctuation in the degree of ST segment deviation.
What does ST segment depression generally represent in patients with chest pain?
Subendocardial ischemia
What is the typical contour of ischemic ST segment depression?
Horizontal or downsloping
An upsloping contour may be seen but is less frequently associated with ischemia.
Which clinical conditions can present with ST segment depression?
- Myocardial ischemia or infarction
- Repolarization abnormality of left ventricular hypertrophy
- Bundle branch block
- Ventricular paced rhythm (VPR)
- Digoxin effect
- Hyperkalemia
- Hypokalemia
- Pulmonary embolism (PE)
- Intracranial hemorrhage
- Myocarditis
- Rate-related ST segment depression
- Postcardioversion of tachydysrhythmias
- Pneumothorax
In what leads will ST segment depression appear during transmural posterior wall infarction?
Right to mid precordial leads
What type of myocardial infarction is associated with ST segment depression?
NSTEMI
ST segment depression can also precede ST segment elevation in STEMI
What does ST segment depression in leads V1 to V3 indicate in the context of posterior MI?
It reflects a mirror image of ST segment elevation from posterior MI
This occurs when there is ST segment depression in the right- to mid-precordial leads
What is the significance of reciprocal ST segment depression?
It indicates changes seen in leads opposite to ST segment elevation
For example, in posterior MI, depression in V1 to V3 reflects elevation in posterior leads V8 and V9
Which lead is best for identifying reciprocal ST segment depression in inferior MI?
Lead aVL
This lead is 150 degrees removed from lead III
In anterior STEMI, which inferior leads may show reciprocal ST segment depression?
II, III, or aVF
These leads can show reciprocal changes in the context of ST segment elevation
True or False: Reciprocal changes in STEMI increase the specificity and positive predictive value of the ECG.
True
They coincide with larger infarctions and increased risk of adverse cardiovascular events
What does T wave inversion typically suggest in the context of ACS?
Chronic ischemic change or ACS
T wave inversions are nonspecific but significant in the right clinical context
Which leads typically have upright T waves?
I, II, and V3 to V6
T waves are normally inverted in lead aVR
What characterizes the T wave inversions of ACS?
They are classically narrow and symmetrical
The preceding ST segment is typically isoelectric
What is Wellens syndrome characterized by?
Deep symmetrical T wave inversions (type I) or biphasic T wave changes (type II)
These changes are suggestive of myocardial ischemia
What additional electrocardiographic features are associated with Wellens syndrome?
Isoelectric or minimally elevated ST segments and lack of precordial Q waves
This can occur in both anginal and pain-free states
What happens to T waves in MI without culprit artery reperfusion?
T waves may invert as ST segments return to baseline
The inversion may not be particularly deep
What does pseudonormalization of the T wave indicate?
An apparently normal T wave replacing a previously inverted T wave during acute ischemia
This can be a sign of acute ischemia
What do pathologic Q waves represent?
Irreversible myocardial necrosis
They may develop within the first hour of infarction or at 8 to 12 hours
True or False: Q waves can persist after MI as markers of previous infarction.
True
They may also disappear over time, regardless of reperfusion status
