Infarction Flashcards
Most common area that suffers from MI
Left Ventricle
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
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
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
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
The widow Maker aka
Left Anterior Descending coronary artery
Primary Coronary Vessels of the Heart
Left Coronary Artery "Left Main Artery" Circumflex Artery Left Anterior Descending Artery Posterior Descending Artery Right Coronary Artery
Myocardial Infarction Triad
Ischemia —> Injury —> Necrosis
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!!
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
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
Injury
Part of Infarction Triad
Means acute or recent
can be transient
EKG: ST elevation
Myocardial Injury EKG
ST elevation
>1mm is out of normal range
ST elevation
normal limit for ST segment is 1mm is pathological
Myocardial injury
Injury (past injury)
can be subendocardial infarction
indicates compromised coronary blood flow
EKG: ST depression
subendocardial infarction
below the surface/deep in the myocardium
ST Depression
Normal limit for ST segment is 1mm depression is pathological
past myocardial injury/subendocardial infarction
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)
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
