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Le# Posterior Hemiblock
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Ischemic Heart Disease
� Is most commonly due to atherosclerosis in coronary arteries
� Ischemia occurs when blood supply to tissue is deficient � Causes increased lactic acid from anaerobic metabolism
� Often accompanied by angina pectoris (chest pain)
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CHEST PAIN
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259
ST Segment
• Normal ST Segment is flat (isoelectric) – Same level with subsequent PR segment
• Elevation or depression of ST segment by 1 mm or more, measured at J point IS ABNORMAL
• “J” (Junction) point is the point between QRS and ST segment
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What’s a J point and where is it? • J point – point to
mark end of QRS and beginning of ST segment – Evaluate ST elevation
0.04 seconds after J point
– Based on relationship to the baseline
– Used in assessing ST elevation
Ischemic Heart Disease
� Detectable by changes in S-T segment of ECG
� Myocardial infarction (MI) is a heart attack � Diagnosed by high levels of creatine phosphate (CPK) &
lactate dehydrogenase (LDH)
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Measuring for ST Elevation • Find the J point • Is the ST segment
>1mm above the isoelectric line in 2 or more contiguous leads?
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EARLY REPOLARIZATION
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Characteristic changes in AMI
� ST segment elevation over area of damage
� ST depression in leads opposite infarction
� Pathological Q waves
� Reduced R waves
� Inverted T waves
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Myocardial Insult • Ischemia
– lack of oxygenation – ST depression or T wave inversion – permanent damage avoidable
• Injury – prolonged ischemia – ST elevation – permanent damage avoidable
• Infarct – death of myocardial tissue; damage
permanent; may have Q wave 4/18/12 badri@gmc 266
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ST elevation
R
P
Q
ST
• Occurs in the early stages
• Occurs in the leads facing the infarction
• Slight ST elevation may be normal in V1 or V2
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Variable Shapes Of ST Segment Elevations in AMI
Goldberger AL. Goldberger: Clinical Electrocardiography: A Simplified Approach. 7th ed: Mosby Elsevier; 2006. 4/18/12 badri@gmc 268
269
Deep Q wave
R
P
Q
T
ST
• Only diagnostic change of myocardial infarction
• At least 0.04 seconds in duration
• Depth of more than 25% of ensuing R wave
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T wave changes
R
P
Q
T
ST
• Late change
• Occurs as ST elevation is returning to normal
• Apparent in many leads
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Bundle branch block
I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6
Anterior wall MI Left bundle branch block
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Sequence of changes in evolving AMI
1 minute after onset 1 hour or so after onset A few hours after onset
A day or so after onset Later changes A few months after AMI
Q!
R!
P!
Q!T!
ST R!
P!
Q!
ST
P!
Q!T!
ST
R!
P!
S
T
P!
Q!T!
ST
R!
P!
Q!
T!
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Evolution of AMI A - pre-infarct (normal) B - Tall T wave (first few
minutes of infarct) C - Tall T wave and ST
elevation (injury) D - Elevated ST (injury),
inverted T wave (ischemia), Q wave (tissue death)
E - Inverted T wave (ischemia), Q wave (tissue death)
F - Q wave (permanent marking) 4/18/12 badri@gmc 274
EVOLUTION OF MI
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Diagnostic criteria for AMI
• Q wave duration of more than 0.04 seconds
• Q wave depth of more than 25% of ensuing r wave
• ST elevation in leads facing infarct (or depression in opposite leads)
• Deep T wave inversion overlying and adjacent to infarct
• Cardiac arrhythmias
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ACUTE INFARCTION
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Location of infarct combinations
aVR V1 V4 I
II
III
LATERAL
INFERIOR
ANT POST ANT
SEPTAL
ANT
LAT
aVL
aVF
V2
V3
V5
V6
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Lateral View – I, aVL, V5, V6
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Lateral infarction Lateral infarction
I II III aVR aVL aVF V1 V2 V3 V4 V5 V6
Left circumflex coronary artery 4/18/12 badri@gmc 280
Complications of Lateral Wall MI I, aVL, V5, V6
• Monitor for lethal heart blocks
– Second degree type II – classical – Third degree heart block – complete
• Treat with TCP – Consider sedation for patient comfort – Monitor for capture – Monitor for improvement by measuring level
of consciousness and blood pressure 4/18/12 badri@gmc 281
Inferior View – II, III, aVF
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Inferior infarction Inferior infarction
I II III aVR aVL aVF V1 V2 V3 V4 V5 V6
Right coronary artery 4/18/12 badri@gmc 283
Complications of Inferior Wall MI II, III, aVF
• May see Mobitz type I – Wenckebach – Due to parasympathetic stimulation & not injury to conduction
system
• Hypotension – Right ventricle may lose some pumping ability
• Venous return exceeds output, blood accumulates in right ventricle
– Less blood being pumped to lungs to left ventricle and out to body
– Develop hypotension, JVD, with clear lung sounds • Treated with additional fluid administered cautiously • Ems to contact Medical Control prior to NTG administration
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Septal View – V1 & V2
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Complications of Septal Wall MI V1 & V2
• Monitor for lethal heart blocks – Second degree type II – classical – Third degree heart block – complete
• Treat with TCP
• Rare to have a septal wall MI alone – Often associated with anterior and/or lateral
wall involvement
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Anterior View – V3 & V4
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Anterior infarction Anterior infarction
I II III aVR aVL aVF V1 V2 V3 V4 V5 V6
Left coronary artery
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Complications of Anterior Wall MI V3 & V4
• Occlusion of left main coronary artery – the “widow maker” – Cardiogenic shock and death without prompt reperfusion
• Second degree AV block type II – Often symptomatic – Often progress to 3rd degree heart block – Prepare to initiate TCP
• Third degree heart block – complete – Rhythm usually unstable – Rate usually less than 40 beats per minute – Prepare to initiate TCP
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ST T changes- MI anteroseptal/// axis???
� ST T in V1-V5/ aVL
� Axis
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291 4/18/12 badri@gmc 292
ST DEPRESSION
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� ST in V1-V4
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ISCHEMIC T WAVES LAHB RBBB
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INFEROLATERAL ISCHEMIA
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Hypertrophy Strain Pattern vs. ACS
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DIGOXIN EFFECT
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PERICARDITIS
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Patient Presenting with Coronary Chest Pain – AMI Until Proven Otherwise
• Oxygen – May limit ischemic injury – New trends/guidelines coming out in 2011 SOP’s
• Aspirin - 324 mg chewed (PO) – Blocks platelet aggregation (clumping) to keep
clot from getting bigger – Chewing breaks medication down faster & allows
for quicker absorption – Hold if patient allergic
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• Nitroglycerin - 0.4 mg SL every 5 minutes – Dilates coronary vessels to relieve vasospams – Increases collateral blood flow – Dilates veins to reduce preload to reduce
workload of heart • Watch for hypotension • If inferior wall MI (II, III, aVF), contact Medical
Control prior to administration – If pain persists, move to Morphine – Check for recent male enhancement drug use
(ie: viagra, cialis, levitra) • Side effect could be lethal hypotension
Acute Coronary Syndrome Medications cont.
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Acute Coronary Syndrome Region X EMS Medications cont.
• Morphine - 2 mg slow IVP – Decreases pain & apprehension – Mild venodilator & arterial dilator
• Reduces preload and afterload – Given if pain level not changed after
nitroglycerin – Give 2mg slow IVP repeated every 2 minutes
as needed – Max total dose 10 mg
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T wave • The normal T wave is asymmetrical, the
first half having a more gradual slope than the second half
• The T wave should generally be at least 1/8 but less than 2/3 of the amplitude of the corresponding R wave
• T wave amplitude rarely exceeds 10 mm • Abnormal T waves are symmetrical, tall,
peaked, biphasic or inverted.
T wave
• As a rule, the T wave follows the direction of the main QRS deflection. Thus when the main QRS deflection is positive (upright), the T wave is normally positive.
• Other rules – The normal T wave is always negative in lead
aVR but positive in lead II. – Left-sided chest leads such as V4 to V6
normally always show a positive T wave. 306
HYPERKALEMIA: PEAKED T WAVES
See a normal EKG…
HYPOKALEMIA: PROMINENT U WAVES
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QT interval • QT interval decreases when heart rate increases • A general guide to the upper limit of QT interval.
For HR = 70 bpm, QT<0.40 sec. – For every 10 bpm increase above 70 subtract 0.02
sec. – For every 10 bpm decrease below 70 add 0.02 sec
• As a general guide the QT interval should be 0.35- 0.45 s, and should not be more than half of the interval between adjacent R waves (R-R interval).
QT Interval
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Long QT Syndrome
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Prolonged QTc
• During sleep • Hypocalcemia • Ac myocarditis • AMI • Drugs like
quinidine,procainamide,tricyclic antidepressants
• Hypothermia • HOCM
• Advanced AV block or high degree AV block
• Jervell-Lange –Neilson syndrome • Romano-ward syndrome
Shortened QT
• Digitalis effect • Hypercalcemia • Hyperthermia • Vagal stimulation
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QT Interval
• The QT interval increases slightly with age and tends to be longer in women than in men.
• Bazett's correction is used to calculate the QT interval corrected for heart rate (QTc): QTc = QT/ Sq root [R-R in seconds]
U wave • Normal U waves are small, round, symmetrical
and positive in lead II, with amplitude < 2 mm (amplitude is usually < 1/3 T wave amplitude in same lead)
• U wave direction is the same as T wave direction in that lead
• More prominent at slow heart rates and usually best seen in the right precordial leads.
• Origin of the U wave is thought to be related to afterdepolarizations which interrupt or follow repolarization
Final Impression “ Does the ECG correlate with the clinical scenario ?”
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