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70 terms

EKG: Section C - 2

MI's; Hypertrophy; Intraventricular conduction delays and axis deviation
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Describe Myocardial Ischemia:
narrowing of coronary arteries reduces blood flow to myocardium; transient oxygen deficiency
what does the pt often feel with myocardial ischemia?
chest pain during exertion
What is most affected with myocardial ischemia?
left ventricle
What is the EKG criteria for Myocardial ischemia?
ST segment depression = or greater than 1mm at 0.08 sec; ST segment may be upsloping, downsloping or horizontal and T waves may be flattened or inverted
Describe what myocardial injury is:
stage beyond ischemia; transient, usually no permanent damage; vasoplastic angina(coronary artery spasm) can cause temporary ST segment elevation
What is a myocardial infarction also known as?
heart attack
2 types of myocardial infarction:
Transmural and Subendocardial MI
Transmural MI affects what?
all layers of the heart wall - endocardial, myocardial and epicardial layers of the heart wall
Subendocardial MI affects what?
only affects the endocardium of the heart
EKG changes due to MI include:
ischemia is normally displayed as ST Segment depression; old MIs show prominent Q waves that never resolve
When are serum enzymes secreted?
After an MI only when cardiac muscle tissue is damaged
Measuring serum enzymes is the primary diagnostic too for determining what?
the severity and age of infarction
What are the serum enzymes measured to determine MIs?
Creatine phosphokinase (CPK) -sometimes shortened to creatine kinase (CK); Glutamic Oxoloacetic transaminase (SGOT); Lactic dehydrogenase (LDH) and Troponin I
How long after MI does CPK elevate?
in first few hours
How long after MI does CPK peak?
in 24 hours
After MI how long does it take for CPK levels to return to normal?
3 -4 days
How long after MI does it take SGOT levels to elevate?
several hours after infarction
When does SGOT peak after MI?
in 1 1/2 to 3 days
When does SGOT levels return to normal after MI?
4 -5 days
How long after MI does it take LDH levels to elevate?
48 hours after infarction
When do LDH levels peak after MI?
4 to 7 days
How long does it take LDH levels to return back to normal?
2 weeks
When do Troponin I levels begin to rise?
4 -6 hours after injury
When do Troponin I levels peak?
12 - 16 hours
5 examples of the different causes of death resulting from complications of MI (sometimes years later)
Cardiac arrest; ventricular aneurysm rupture (necrotic muscle wall becomes thin and bulges outwardly until it cracks; CHF (impaired pumping action of the heart) and R-side HF due to L-Side HF which occurs more frequently
What is the Hallmark of Left sided heart failure?
Elevated pressure and congestion in systemic veins and capillaries
What is the Hallmarke of Right sides heart failure?
elevated pressure and congestion in the pulmonary veins and capillaries
What does left sided heart failure cause?
systemic edema (peripheral)
What does right sided heart failure cause?
pulmonary edema
What does CHF signify and what is it known as?
Signifies the terminal period of other diseases and is known as "end stage cardiac disease"
CHF may result in what?
an embolism (thrombus)
What is a thrombus?
an embolism which is blood clot that can occlude any vessel
CHF causes what?
total or near total, lack of perfusion to tissue
EKG criteria for Q waves for MI
may appear immediately or in several days; 1/3 height of R wave; 0.04 sec wide (if neither criteria is met, Q waves are not diagnostic)
EKG criteria for T waves for MI:
prolonged; increased in magnitude; upright; inverted
EKG criteria for ST segment for MI:
elevation in leads facing injured area; depression in leads opposite injured area; when elevation occurs damage is often progressive and severe
Initial EKG tests is DIAGNOSTIC of acute MI in what percent of patients?
60%
Initial EKG tests is INCONCLUSIVE of acute MI in what percent of patients?
25%
Initial EKG tests is INACCURATE of acute MI in what percent of patients?
15%
What is necessary for accurate diagnosis?
successive tracings
A definitive diagnosis for determining an old infarction depends on what?
presence of Q waves; (abnormal Q waves may be absent in transmural MI and nearly half of Q waves in anterior and inferior leads are false positive)
To determine the location of an MI you have to have what?
Significant Q waves in at least 2 leads
Significant Q waves for Anterior Infarction would be in what leads?
(AWMI) VI - V4
Significant Q waves for Lateral Infarction would be in what leads?
(LWMI) I, AVL, V5 and V6
Significant Q waves for Inferior Infarction would be in what leads?
(IWMI) II, III, AVF
Criteria for Posterior Infarction:
(PWMI) tall R wave in V1 and V2; AVF at least 25% of amplitude of R wave; serum levels very critical to obtain ( esophageal leads make accurate)
To make an accurate diagnosis of hypertrophy what procedures comes first, second and third?
echocardiography, angiography and then EKG to determine hypertrophy
In hypertrophied areas what is the signifying markings on the EKG?
large voltages are recorded in the leads over hypertrophied areas
Criteria for LEFT ATRIAL HYPERTROPHY:
Lead VI- diaphasic Pwave with terminal portion bigger; Lead I - Pwave is greater than 2.5 mm in hieght
Criteria for RIGHT ATRIAL HYPERTROPHY:
Lead II, III, AVF - Pwave hight is 2.5mm or greater; Lead V1 - diaphasic P wave with initial portion bigger
Criteria for LEFT VENTRICULAR HYPERTROPHY:
AVL will measure greater than 11mm; R wave in V5 and the S wave in V1 will be greater than 35 mm; V5 or V6 is greater than 27 mm high; repolarization changes may show ST depression and asymmetrical T wave inversion
Criteria for RIGHT VENTRICULAR HYPERTROPHY:
V1 - R wave is taller than S wave; Inverted R wave progression; Repolarization changes with St depression and asymmetrical T wave inversion in VI and V2
What are Intraventricular Conduction Delays?
abnormal conduction of impulse in one or more of conduction pathways below the Bundle of His
Intraventricular conduction delays include what 4 arrythmias?
Right /Left Bundle Branch blocks; and Left Anterior/Posterior Fascicular Blocks
The impulse pathway of a RBBB:
normal impulse reaches RBBB and advances to LBB and depolarizes left ventricle; impulse then travels through the intraventricular septum and intiates right ventricular depolarization
EKG Criteria for RBBB:
QRS greater than 0.10 sec; QRS positive in V1; repolarization changes in V1 and V2 and QRS has a RSR wave appearance in V1 and V2
The impulse pathway of a LBBB:
Cardiac impulse travels to LBB, deflects to RBB and depolarizes through IV septum to depolarize LV
EKG criteria for LBBB:
QRS greater than 0.10sec; QRS negative in V1; repolarization changes in I, AVL, V5 and V6; QRS has an RR wave appearance in V5,V6
The impulse pathway of a Left Anterior Fascicular Block:
impulses reaches LBB, is delayed at anterior fascicle and travels down posterior fascicle; LV depolarized through connection of Purkinje Fibers
EKG Criteria for Left anterior Fascicular Block:
QRS axis -30 degrees or greater with small Q wave in lead I
The impulse pathway of a Left Posterior Fascicular Block:
impulse travels down anterior fascicle through connection of Purkinje fibers and depolarizes LB
EKG criteria for Left Posterior Fascicular Block:
QRS axis shifts right to +110 degrees or greater with small Q waves in lead III
For Quick Look Method for axis deviation what 2 leads do you use?
Lead I and AVF
Both Lead I and AVF positive =
Normal Axis Deviation
Lead I Negative and AVF Positive =
Right Axis Deviation
Leave I Positive and AVF Negative =
Left Axis Deviation
Both Lead I and AVF Negative =
Extreme Right Axis Deviation
If Lead II is positive it is:
truly normal
If Leave II is negative it is:
truly Left Axis
3 Causes of Axis Deviation:
Hypertrophy (towards the affected side); myocardial infarction (away from the affected side) and anatomical position of the heart