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12 Lead ECG
Terms in this set (113)
What is the criteria for a Wandering Atrial Pacemaker/Multifocal Atrial Tachycardia?
At least 3 different P-wave morphologies
If you see ??? in the presence of a prolonged QTc, prepare for imminent cardiac arrest.
If you see T-wave alternans in the presence of a ???, prepare for imminent cardiac arrest.
T-wave alternates does not involve?
The p-wave or QRS complex.
What is one of the strongest predictors of imminent malignant ventricular dysrhythmias and sudden cardiac arrest?
T-wave alternans: beat-to-beat variation in the size of shape of the T-wave.
A Right Bundle Branch Block should never have?
ST-segment elevation - anywhere.
ST-segment depression is normal in V1 and V2 ± V3.
What is the blood supply for the SA node?
1. Most common is RCA
2. Second most common is LCD
3. Least common is both the RCA and LCA
What electrical pathway transmits impulses through the inter-atrial septum?
What electrical pathway transmits imputes from the AV node and gives rise to the right and left bundle branches?
Bundle of His - it is the only route of communication between the atria and the ventricles.
Where does the left bundle branch end?
At the beginning of the left anterior and left posterior fascicles.
What are the key characteristics of Premature Atrial Contraction?
Different PR interval
What is a compensatory pause?
In sync with beat preceding premature complex
What is a non-compensatory pause?
Out of sync with preceding beat
What is the criteria for P-Mitrale?
1. Notched P-wave
2. > 0.12 seconds
3. Notch > 0.04 seconds
What is the significance of P-Mitrale?
Severe Left Atrial Enlargement = Mitral Stenosis/Regurg.
*Prolong conduction thru large LA
What is the criteria for P-Pulmonale?
Peaked T-wave; > 2.5 mm high (limb leads)
What is the significance of P-Pulmonale?
Severe Right atrial enlargement
What is the diagnosis if the first half of a biphasic p-wave is taller in V1 than in V6?
Right Atrial Enlargement
Second half of biphasic p-wave; width of one small box =
Causes of RAE =
Pulmonic Valve Dz
Asymmetrical T-waves more common in =
Sequence of ventricular depolarization =
Septum (Front and Right)
Main Ventricle (Down and Back)
Ventricular Base (Up and Back)
Flat ST segments + Symmetrical T-waves =
Checklist for R:S >/= 1 in V1/V2 =
Posterior Wall MI (Horizontal STD and upright TW)
*Could be old posterior wall MI if no ST changes
RBBB (rSR' pattern)
WPW (Delta wave)
RVH (Dx of exclusion)
QS wave in V1 =
QS wave in V2, especially V3 =
Past or present anteroseptal MI
Significant Q-wave + Symmetrical T-wave =
No positive components of QRS =
Transition Zone =
Precordial; QRS complex is isoelectric
Normal transition zone =
V3 or V4
Additional evidence of RVH =
Osborne wave =
The colder the patient, the larger the Osborn wave.
Associated with bradycardia, A-Fib, QRS widening, prolonged QTc
Osborne wave; differential diagnosis =
Sepsis (cold shock)
Osborne waves; do not require =
Catecholamines do not work at body temps below =
32C / 89.6F
Picture the hex axial system =
Lead I is isoelectric to =
Lead II is isoelectric to =
Lead III is isoelectric to =
How many isoelectric complexes in the limb leads =
Should only be one.
(Should also be the smallest QRS voltage)
Normal axis =
-30 - 90 degrees
Which limb lead has smallest QRS voltage =
QR' or qR' in V1 =
Anteroseptal MI with RBBB
Q wave takes place of the R wave; the next positive wave is technically the R'
Most common ST depression with RBBB =
Right precordial (V1-V3)
Can you diagnose LVH with RBBB?
*You can't diagnose LVH with LBBB
Can you diagnose RVH with RBBB?
Difficult, if not impossible
Can you diagnose LVH with LBBB?
An "S-wave" must go below the =
Baseline, in order to meet the definition of an S-wave
Where can you fined positive, notched QRS complexes in LBBB?
Usually V5 and V6
QRS complexes _________ or more could represent a ventricular focus acting as the pacemaker.
In LBBB, QRS and ST/T waves should be?
Discordant = normal
Criteria for diagnosing LBBB =
1. QRS >/= 0.12 seconds
2. Broad, monomorphic R-wave in I and V6 (no Q-waves, may be notched as RR' [no S-wave below baseline])
3. Broad, monomorphic S-wave in V1 (may have small r-wave)
Lead I and V6 should be =
LVH should not be wider than =
0.12 seconds (3 small boxes)
QT prolongation commonly occurs in =
BBB, especially LBBB.
Not clinically significant.
Left Anterior Hemiblock criteria =
2. Negative in II
3. More proof: small r in II, III, aVF
Patient has bifascicular block and an MI =
Get ready for a 3rd degree HB
What is a bifascicular block?
RBBB with either LAFB or LPFB
MC is RBBB and LAFB
RBBB and LAFB are considered =
Stable; don't usually turn into a 3rd degree HB
What will RBBB with LPFB look like =
RBBB with small q wave in lead III; RAD
May not be able to see s-wave in lead I
Criteria for LPFB =
1. RAD (90 to 180)
2. s-wave in I
3. q-wave in III
4. Not RVH, RAH, or lateral wall mi
Right Axis Deviation; degrees =
90 - 180
Asymmetrical T-wave =
Very broad T-waves can be found in =
CNS events; especially intracranial hemorrhage
Can be positive or negative broad T-waves
T-waves should not more taller than =
6mm in limb leads; 12 mm in precordials
> 2/3 height of R-wave
T-waves should be upright in =
I, II, and V3-V6
Tall, symmetric T-waves; especially mid-precordial =
Think = hyperkalemia
R-wave progression in anterior wall MI =
The only disease process that can cause AMI of both right and left coronary arteries simultaneously =
Bipolar Leads =
I, II, and III
Unipolar Leads =
aVR, avL, avF, and V1 - V6
Hyperacute T-waves =
T-wave inversion =
Which will dominate the ECG if both are present; hyperacute T-waves or inverted T-waves?
Inverted T-waves; represent subepicardial ischemia, which is anatomically closer to to electrodes.
Supepicardium also has more mass.
"Current of Injury"; theory =
-Damaged myocardial cells leak K+, cells become more negative
-Changes the ECG baseline
-Subendocardial: Damage close to + electrode, baseline lowers (ST segment stays the same, appears elevated)
-Subendocardial: baseline raises; ST stays same; appears depressed
Most sensitive lead for detection inferior wall MI =
Inferior wall MI will have STE in II and ST depression in AVL; unless =
There is simultaneous lateral wall MI
Most sensitive lead for detection of high lateral wall MI =
Posterior wall MI will have ST elevation in V1-V3; unless =
There is an RVI causing simultaneous ST elevation in V1, which will cancel out ST segment changes.
Septal MI or RV infarction may have ST depression in =
V5 - V6
ST elevation; II, III, aVF, and V1:
Anatomic Location =
Culprit Vessel =
Anatomic Location = Inferior and RV AMI
Culprit = RCA proximal to RCA marginal branch
ST elevation; II, III, aVF, and ST depression in V1-V4
Anatomic Location =
Culprit Vessel =
Anatomic Location = Inferior Posterior AMI
Culprit Vessel = Dominant RCA - 70%; Dominant Circ 30%
ST elevation; V2-V4
Anatomic Location =
Culprit Vessel =
Anatomic Location = Anterior AMI
Culprit Vessel = Mid-LAD
ST segment elevation measurement is relative to =
The greater the depth of the ST depression =
The more likely it is to be ischemia and/or infarction.
ST depression could represent these 3 things =
1. Posterior wall MI
2. Reciprocal changes
3. Subendocardial ischemia
Posterior wall MI mimics =
RV MI usually occurs in the presence of =
Inferior wall MI; either acute or old
In the setting of acute cardiac ischemia, ST elevation in aVR is suggestive of =
Left Main Coronary Artery Occlusion
Two conditions that increase the specificity for Left Main Coronary Occlussion when ST elevation in aVR is present?
1. STE in avR > STE in V1
2. Simultaneous STE in aVR and aVL
1/3 of inferior MIs will extend to =
Another 1/3 of inferior MIs will extend to =
The AV node is always supplied by the =
The left anterior fascicle enervates =
Anterior and superior aspect of the Left Ventricle
The left posterior fascicle is difficult to block; why =
Has wide distribution
Positive electrical impulse moves away from a positive electrode =
(Positive wave moving away from positive lead)
Evaluate P-waves; leads =
II, III, and aVT
PR intervals; junctional rhythm =
< 0.11 seconds
If 0.12 - 0.20 seconds, it's a low atrial ectopic pacemaker
(AoI P. 91)
Biphasic P-wave in V1; automatically -
Intra-Atrial conduction delay
*Not enough enlargement to cause P-Pulmonale or P-Mitrale
Symmetrical T-waves; commonly found =
(AoI P. 109)
PR depression; abnormal criteria =
> 0.8 mm below baseline (Almost 1 small box)
Normal PR depression; due to =
(AoI P. 127)
Pericarditis; presents with 1 or more of the following =
-Diffuse ST elevation (concave upward/scooped out)
-Terminal QRS notching
Short PR interval; criteria =
≤ 0.11 seconds
*Retrograde junctional P-wave
Bundle of Kent bypasses =
The AV node
What is difficult, if not impossible, to diagnose in WPW?
Abnormal depolarization causes abnormal depolarization that allows for ST and T wave abnormalities.
WPW can be mistaken for infarcts when =
The delta waves are negative - it will resemble a Q-wave.
Antidromic WPW =
Conduction travels through the Bundle of Kent and back up the AV node to the atria.
Orthodromic WPW =
Conduction travels down the AV node and returns to the atria via the Bundle of Kent.
Most dangerous form of WPW; orthodromic or antidromic =
-AV node is bypassed so no physiologic block
-Very fast WCT
-AFib/Flutter with 1:1
WPW; small delta wave =
Most conduction was through the AV node
Heart Rates > 250 usually associated with =
If > 300, must be associated with bypass tract.
What does the normal QRS look like in V1 and V2?
The limb leads are =
The augmented leads are =
The limb leads are = bipolar
The augmented leads are = unipolar
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