Infarction Flashcards by Brooke Davies

Most common area that suffers from MI

Left Ventricle

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EKG can be used to… (diagnostic implications)

Diagnose occlusion
Can tell which coronary artery is occluded
Reveals any blocks in ventricular conduction caused by infarction
Can help determine if coronary vessel is narrowed
…thus providing lifesaving information

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Left Ventricle

Commonly the area that suffers from MI
Uses greatest blood supply (actually using the O2 and nutrients that the blood transports)
Reference for describing infarct location

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Necrotic

Lack of blood supply reduces the tissue to functionally dead
Does not depolarize
No contraction
HYPOXIC VENTRICULAR FOCI NEARBY ARE OFTEN THE SOURCE OF SERIOUS VENTRICULAR ARRHYTHMIAS

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Ventricular arrhythmias caused by

hypoxic ventricular foci
Think of this as a last cry for help
Foci depolarize as they are “dying” causing ventricular arrhythmia

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The widow Maker aka

Left Anterior Descending coronary artery

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Primary Coronary Vessels of the Heart

Left Coronary Artery "Left Main Artery"
Circumflex Artery
Left Anterior Descending Artery
Posterior Descending Artery
Right Coronary Artery

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Myocardial Infarction Triad

Ischemia —> Injury —> Necrosis

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Ischemia

Means reduced blood supply
can cause chest pain (angina)
significant EKG: T wave inversion (inverted and symmetrical)
Do not exercise this person! can cause MI!!

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Ischemia on EKG

T Wave inversion at rest (inverted and symmetrical)
T wave inversion in V1-V6 is considered pathological
Do not exercise this person

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T wave inversion

In adults flat or minimal T wave inversion IN LIMB LEADS may be normal
T wave inversion in V1-V6 is PATHOLOGICAL
Ischemia

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Injury

Part of Infarction Triad
Means acute or recent
can be transient
EKG: ST elevation

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Myocardial Injury EKG

ST elevation

>1mm is out of normal range

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ST elevation

normal limit for ST segment is 1mm is pathological

Myocardial injury

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Injury (past injury)

can be subendocardial infarction
indicates compromised coronary blood flow
EKG: ST depression

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subendocardial infarction

below the surface/deep in the myocardium

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ST Depression

Normal limit for ST segment is 1mm depression is pathological
past myocardial injury/subendocardial infarction

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Necrosis

can be subendocardial infarction
indicates compromised coronary blood flow
EKG: significant Q wave
necrotic areas cannot depolarize and so cannot contract
can lead to an enlarged heart (not necessarily thickened muscle, but stretched)

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Insignificant Q wave

normal limit is less than .04 seconds (1 little box)

Significant Q wave

At least 0.04 sec in duration (> 1 little box)
and/or
1/3 of the entire QRS amplitude 
Check all leads except AVR
Indicative of necrosis

Leads to check for significant Q wave

All leads except AVR
Limb Leads I, II, III
Limb Leads AVL, AVF
V1-V6

Anterior Infarction

The positive (chest) electrode records only initial "away" vectors from the opposite side, so a significant Q records on the EKG
Remember: Negative inflection due to vectors moving AWAY from positive electrode

Lateral Infarct

The positive LEFT ARM electrode records only initial “away” vectors from the opposite side, so a sig. Q records on the EKG
Remember: Negative inflection due to vectors moving AWAY from positive electrode

Inferior Infarct

The positive LEFT FOOT electrode records only initial “away” vectors from the opposite side, so a sig. Q records on EKG
Remember: Negative inflection due to vectors moving AWAY from positive electrode

Understanding ventricular depolarization

Left ventricular depolarization moves in opposite directions (simultaneously) in opposing walls of ventricles Positive electrode sees through the electrical void of an infarct (void due to necrosis inability to depolariz) Electrode records "away" vectors, and thus sig. Q wave

Anterior Infarct Q

Q in V1, V2, V3, or V4 (CHEST LEADS) | think about placement of these electrodes, very close to the front of the heart

Lateral Infarct Q

Q in Lead I and AVL Think of location of leads: lateral necrosis would be in between Lead 1 and AVL because each has a positive electrode positioned lateral on the left arm (I at 0deg and AVL at -30deg)

Inferior Infarct Q

Q in II, III and AVF Think of location of leads: necrosis would be between III, AVF, and II because each has a positive electrode positioned inferior on the left foot (III at 120deg, AVF at 90deg, and II at 60deg)

Posterior infarct

Large R wave (the opposite of Q wave) in V1 and V2

Acute posterior infarction

Large R wave and ST depression in V1 and V2 | Using "Reversed Trans-illumination or the Mirror Test", looks like significant Q wave and ST elevation

Reversed Trans-illumination and Mirror Test

Used for Acute posterior infarction positive tests will look like ST elevation Reversed Trans-illumination: turn paper backwards and hold up to light Mirror Test: Hold EKG strip up to a mirror

Large R waves

found in V1 and V2 | indicative of posterior infarct

Difference between Anterior and Posterior infarct

ALWAYS CHECK V1 AND V2 FOR ST CHANGES Anterior: ST ELEVATION and Q WAVES in V1 and V2 Posterior: ST DEPRESSION and LARGE R WAVES in V1 and V2

Branches of Left coronary artery

L cricumflex | L anterior descending

Circumflex Artery supplies...

supplies lateral side of heart

LAD supplies...

supplies anterior heart, including major portions of the L ventricle aka "the widow maker"

Right Coronary artery supplies...

supplies R portion of heart and posterior heart | also thought to supply tissue around the SA node

Indication of location of occlusion (higher vs lower in an artery)?

The higher or closer to the trunk of an artery the occlusion is located, the worse off the individual is

Circumflex Branch of L Coronary Artery responsible for

Lateral infarction because it supplies the lateral portion of the heart (Q in AVL and I)

Anterior Descending branch of L Coronary Artery responsible for

Anterior infarct (Q in V1, V2, V3, V4) because it supplies the anterior portion of the heart, especially important is the Left ventricle

Coronary Artery responsible for Inferior Infarction

R Coronary Artery or L Coronary Artery depends on individual anatomy (Q in Lead II, AVF, III)

Right Coronary Artery responsible for....

Posterior infarction (Large R waves and ST depression in V1, V2, maybe Q in V6) because it supplies tissue to right side and posterior of heart (including tissue around SA node) may also be responsible for inferior infarct

What do you do when there is a BBB?

BBB = bundle branch block | STOP THE GXT IMMEDIATELY

Q Waves and Left Bundle Branch Block

Shown by R,R' in V6 You cannot tell if Q wave is significant with a BBB Stop the GXT

One occlusion is indicative of...

occlusions and narrowings in other areas