Yellow Belt Flashcards
Measurements
*Think of Height as Voltage in mV
*Think of Width as Time in Seconds.
Small Box: 1mm x 1mm
Width: 1mm = 0.04 seconds
Height: 1mm = 0.1 mV
Large Box: 5mm x 5mm (5x5 small boxes)
Width: 5mm = 0.20 seconds (because 0.04 x 5 = 0.20 seconds)
Height: 5mm = 0.5mV
Y-axis measures mV (millivolts - amplitude or voltage)
10mm = 1mV (2 large boxes)
X-axis measures time (seconds)
25mm/s = 1 second (or 5 large boxes)
5mm = 1 large box = 1/5th of a second, or 0.2s
1mm = 1 small box = 1/5th of a Large box = 0.04s
Measurements begin at the isoelectric line.
Can take a piece of paper and mark beginning and end, then move paper to the start of boxes and add…
P Wave
- Normal is <0.12 Seconds (3 small boxes)
- If the atria are enlarged, especially the left, then depolarization takes a little longer and p-wave duration is longer. If the right atrium is enlarged, duration is still normal.
P mitrale is the double positive inflection if the left atrium is enlarged. An “M” like P-wave shape. *One arch is from the right atria, the other arch from the left.
PR Interval
prolonged = 1st degree AV block
shortened = LGL or WPW
- Normal is 0.12 - 0.2 seconds (3 - 5 small boxes)
- Represents AV conduction time
Lown-Ganong-Levine Syndrome (LGL Syndrome): normal QRS immediately follows shortened PR interval
WPW: delta wave follows P wave
QRS Complex
- Normal is < or = 0.1 sec (2.5 small boxes)
- Normal is < or = 0.1 sec (2.5 small boxes)
- Prolonged duration = Complete Bundle Branch Block.
Left BBB: M form over left ventricle (leads V4-V6). V1 and V6 reverse mirror each other, even with the T waves.
Right BBB: M form over the right ventricle. V6 typically shows a sagging or U shaped T wave. V1 and V6 reverse mirror each other, even with the T waves
Incomplete BBB: When QRS duration is in between 0.1 - 0.12 seconds. May be caused by dilation of the ventricles, which is known as volume overload.
Precordial Leads Placement
- V1 - fourth intercostal space, just right of the sternum.
- V2 - mirrors V1, just left of sternum.
- V3 - *split the difference between v2 - v4
- V4 - fifth intercostal space, midclavicular line.
- V5 - *split the difference between v4-v6
- V6 - perpendicular to midaxillary line, does not follow fifth intercostal space.
- V7 - post axillary line, horizontal to v6
- V8 - scapulary line
Progression of R wave and S wave
R wave: v1 → v6 = smallest to largest R-Wave, increasing.
S wave: opposite, V1 → v6 = largest to smallest S-Wave, decreasing
Rotation of the lateral line (along septum from apex to base)
Clockwise, counterclockwise
- Regular predicted - R/S ratio same at v4
- Counterclockwise Rotation - R/S ratio is the same around v1 or v2. The heart rotated around the lateral line in a counterclockwise way. The septum is along the v2 lead instead.
- Clockwise Rotation - R/S ratio is the same around v5 or v6. The heart rotated the septum clockwise towards the v5 or v6 lead.
- Do not assess rotation in the following situations: Bundle Branch Block, Q-Wave infarction, WPW Syndrome
Normal ECG
- T-wave is usually positive in precordial leads except in v1.
- P-wave is usually positive except for v1, where it is biphasic.
- V2 has a bigger S-wave than v1. S-wave becomes smaller v2 - v6
- Can have a small Q-wave in v6, v5, and sometimes v4. Usually not in v3-v1.
Ventricular Hypertrophy
Left Ventricular Hypertrophy (shown in photo on front of card)
Precordial leads…
S+R Wave Height:
- S(V1 or V2) + R(V5 or V6) is >3.5mV, then met this criteria
*If V4, V5, or V6 is > 2.5mV by itself, then met this criteria
Right Ventricular Hypertrophy (shown in photo here)
1. R (V1) > or equal to 0.5mV
2. R/S (V1) > or equal to 1. (If R is taller than S)
3. S(V5) > or equal to 0.5mV
Bilateral Ventricular Hypertrophy if criteria for both LVH and RVH met!
ST Depression
ST Shape
- Descending (as in A above)
- Sagging or U shape (as in B above)
- Horizontal (as in C above)
- Ascending (as in D above)
(see notes for specifics for 1-8)
*Note that the ST Segment is between the end of the S wave and the beginning of the T wave.
2 Principles:
1. ST Segment is at the level of the isoelectric line. The line is found after the T wave and before the next P wave when the heart has a moment before depolarization.
ST Depression = if ST segment is lower than isoelectric line
- >0.5mv for V2/V3.
- >1mv for all other leads
2. Except for V1, T wave is normally positive
T wave negativity or T wave inversion = when T wave is negative
T wave Negativity
Asymmetric negativity = hypertrophy (can be for left or right ventricle)
Symmetric negativity = ischemia
*T wave negativity can change between asymmetrical and symmetrical.
*Can also have positive/negative T waves, or negative/positive T waves. Where the T wave flips. Common sign of coronary heart disease.
ECG inflections
Areas of the Heart
Need to know when looking at which part of the heart the MI is in, based on which lead.
- Base (Posterior)- Mostly left atrium, also right atrium and some of great veins
- Diaphragmatic Surface (Inferior) - Mostly left and right ventricles
- Sternocostal (Anterior)- Mostly Right ventricle, some of left ventricle and right atrium
- Left Pulmonary Surface (Lateral?) - Only by left ventricle
- Right Pulmonary Surface (Lateral?)- Only by right atrium
Leads for areas of the heart
bleh
V1, V2, V3 - right ventricle
V2, V3 - basal septum (the part of the interventricular septum closest to the base. Different from the atrial septum though.)
V2, V3, V4 - anterior wall of left ventricle
V5, V6 - lateral wall of left ventricle
V7, V8 - posterior wall of left ventricle
- Anterolateral = Changes that are seen in the anterior wall + lateral wall (blue + green in above photo)
- Posterolateral = changes that are seen in the lateral wall + posterior wall (green + orange above)
Normal ECG strip (for Myocardial Infarction comparison)
Normal -
- Notice that the Q waves increase in size from V4 → V6 (if a Q wave is present in V4)
- Notice that V1, V2, and V3 usually start with a small initial R wave. Sometimes V1 doesn’t have an initial R wave, but it should be there from V2 onward.
- Notice that the R wave size increases from V4 → V6.
There should not be any Q waves in leads with deep S waves!!!
Beware of when V1, V2, V3 have a small initial Q wave.
(Q waves are considered to be abnormal if they…)
A. are longer than 0.04 seconds, or 1 small box.
B. > or equal to ¼ of the R wave
Myocardial Infarction
Overall, the whole QRS is drowning in negativity. Like the whole QRS complex is pulled downward.
Rule #1 - existing R-waves get smaller
Rule #2 - Q waves develop or get deeper
Abnormal in V4, V5, V6 (front photo)
- Notice how the Q wave size is uneven across V4, V5, and V6. This signals an infarction in the septal or lateral regions.
If the lateral region of the V6 also affected, then the Q wave of V6 would also be abnormal in size.
Abnormal in V1, V2, V3
- Small initial Q wave!
Examples (photo on this side)
A. abnormal Q waves in V4, V5, V6, & R waves decrease from V3 → V4. = MI of anterolateral region.
B. R wave lost in V1 & V2, Q wave in V3 & V4 = anterior wall MI
C. R wave decreases V1 → V2, normal again in V4. = basal septum MI
Acute Coronary Syndromes
When blood supply to areas of the heart is suddenly reduced or blocked. Reduced blood supply is termed ischemia. A prolonged ischemia can lead to tissue death, or infarction (aka heart attack)
- Unstable Angina
- STEMI
- Non-STEMI, or NSTEMI
(each have their own flashcard)
Unstable Angina
Unstable Angina: ischemia without infarction
- No necrosis
- ECG normal or ST depression. Maybe T wave inversion (?)
- No enzyme markers are elevated
NSTEMI, or Non-STEMI
Partial necrosis, only inner layer of ventricular wall
- ST Depression, T wave inversion, or both
STEMI
ST Elevation Myocardial Infarction:
Necrosis extends through thickness of myocardium
- ST Elevation
- >1mm in two contiguous limb leads.
- >2mm in two contiguous precordial leads.
*Concave curve is less indicative of myocardial ischemia. Convex curve is indicative of infarction, “tombstone” effect. - Posterior STEMI may show reciprocal changes in anteroseptal leads. V7, V8, and V9 would show ST elevation
*Pathological Q waves may also develop in large infarctions
*hyperacute, or large T waves, can precede ST elevation and change into the “tombstone” shape.
ST Segment Resolution (from elevation back to baseline)
Pathways I and II (It can have a Q wave or not.)
1A = a few hours
1B = ST segment begins to lower
1C = ST segment back to isoelectric line and T wave is negative, may be forever this way for some
1D = chronic phase. The T wave becomes positive again. No residual sign of infarction in ST segment, myocardial scar is only visible as a Q wave
**ST resolution can take hours or days. If longer than days or weeks, consider the possibility of a myocardial aneurysm.
Pathway III
In NSTEMI and unstable angina, symptoms are associated with ST depression or T wave inversion. To tell them apart, you have to look at enzymes. Troponin elevation in NSTEMI, not in angina.
Variant angina, (or Prinzmetal angina, or vasospastic angina):
(Special Case of ST elevation)
a form of myocardial ischemia that is commonly associated with ST elevation.
- Chest pain is typically a short time (15 - 20 min) and appears at rest or even sleep.
- ST elevation returns to baseline immediately after symptoms disappear.
- Coronary occlusion may be caused by a coronary spasm.
Perimyocarditis (top)
- ST segment is usually also elevated like previous examples
- Diffuse disease (unlike infarction) = not limited to one spot or one coronary artery.
- Can be seen in most limb leads and many precordial leads.
- ST elevation comes from the Ascending part of the QRS complex, as opposed to the Descending part such as in a STEMI
Vagotonia (an increase in vagal tone)
- Elevation up to .2 mV in amplitude
- J point is elevated
- Usually accompanied by a tall and peaked T wave
- Low heart rate of <60 bpm
- No typical chest pain
Coronary Arteries
Right Coronary Artery (RCA)
- SA nodal artery
- R. marginal artery
- Posterior descending artery (PDA) (bottom of image)
Left Coronary Artery (LCA)
- Left anterior descending artery (LAD)
- Left Circumflex artery (LCX)
- L. marginal artery
Cardiac Veins
Coronary Sinus
- Great cardiac vein
- Middle cardiac vein
- Small cardiac vein
