Download Twelve-lead

TWELVE-LEAD
INTERPRETATION
By
Leslie Hernandez, BS, NREMT-P, LP
THE HEART
• One heart
• Two sides/Two
arteries
• Three layers
• Four
chambers/valves
BLOOD FLOW THROUGH
THE HEART
– Blood Flow
• From the Body
– Right Atrium
• To the Lungs
– Right Ventricle
• From the Lungs
– Left Atrium
• To the Body
– Left Ventricle
THE ELECTRICAL
CONDUCTION SYSTEM
•
•
•
•
•
•
•
•
SA Node
Intranodal Pathways
AV Junction
AV Fibers
Bundle of His
Septum
Bundle Branches
Purkinje System
The Electrical Conduction
System
THE ECG LEADS
• ECG Leads
– Bipolar
• Leads I, II, and II
– Unipolar
• Leads aVR, aVL, and aVF
– Precordial
• V1, V2, V3, V4, V5, V6
LEAD PLACEMENT
THE ELECTROCARDIOGRAM
WAVES, INTERVAL,
SEGMENTS AND
COMPLEXES
INTERVALS AND SEGMENTS
– Time Intervals
• P–R Interval (PRI)
or P–Q Interval
(PQI)
120–200 ms
• QRS Interval
80–100 ms
• S–T Segment
isoelectric
• Q–T Interval
360–440 ms
P WAVE
P-Waves and Atrial Enlargement
THE PR INTERVAL
120-200 ms
THE QRS COMPLEX
THE T WAVE
How to Measure
ST-Segment Deviation
THE THREE I’S OF THE ACS
• S–T Segment Changes
– Associated with Myocardial Infarctions
• Ischemia
• Injury
• Infarct
Two Rules to Follow
Changes >1 mm (0.1 mV) are significant
If
They occur in two or more contiguous
leads
Patterns and Localization
• Inferior – II, III, and aVF
• Septal – V1 and V2
• Anterior – V3 and V4
• Lateral – I, aVL, V5, and V6
12-Lead ECG Variations
in AMI and Angina
Baseline
Ischemia—tall or inverted T wave (infarct),
ST segment may be depressed (angina)
Injury—elevated ST segment, T wave
may invert
Infarction (Acute)—abnormal Q wave,
ST segment may be elevated and T wave
may be inverted
Infarction (Age Unknown)—abnormal Q wave,
ST segment and T wave returned to normal
Conditions that Mimic Injury
• Pericarditis
– Diffuse or “global” ST-segment changes
• Left bundle branch blocks
– If possibly new, must treat as MI
• Left ventricular hypertrophy
– Causes ST-segment elevation
• Early repolarization
– Causes ST-segment elevation
• Ventricular paced rhythms
– Causes ST-segment elevation
THE NORMAL
TWELVE-LEAD
ANTERIOR MI
ANTEROLATERAL MI
Inf. Wall Inj. Or Infarct with
RCA
II, III, aVF, and V4R:
• Hypotension
• Supranodal and AV nodal blocks
• Atrial fibrillation / flutter
• PAC’s
• Significant NTG and MS hemodynamic
hypersensitivity
INFERIOR MI
HEXAXIAL SYSTEM
NORMAL AND ABNORMAL AXES
-90o
Indeterminate
Axis
Abnormal Left
Axis (Pathologic)
-30o
180o
0
Right Axis
Normal Left
Axis
(Physiologic)
o
Normal QRS Axis
+90o
Axis Deviation
Axis
Normal
Left
EXTREME
RIGHT
Lead I QRS Positive Positive Negative
Lead aVF
QRS
Positive Negative Negative
Right
Negative
Positive
AXIS DEVIATION
• Left Axis Deviation
– Abnormal finding.
– Often associated
with hypertension,
valvular heart
disease, and other
disease processes.
Left Axis Deviation - Causes
• Left ventricular enlargement
– Hypertension
– Aortic stenosis
– Ischemic heart disease
• Left bundle branch block and left anterior
fascicular block
RIGHT AXIS DEVIATION
• Right Axis
Deviation
– Abnormal finding.
– Often associated
with COPD and
pulmonary
hypertension.
Right Axis Deviation - Causes
• Right ventricular enlargement
–
–
–
–
COPD
Pulmonary embolism
Congenital heart diseases
Other diseases causing pulmonary hypertension
and cor pulmonale
• Right bundle branch block and left posterior
fascicular block
BUNDLE BRANCH BLOCKS
• Conduction
Abnormalities
– Bundle Branch Blocks
• Right Bundle
Branch Block
BUNDLE BRANCH BLOCKS
• Conduction Abnormalities
– The Turn-Signal Rule
• QRS > 120 ms
throughout the ECG.
• Look at the QRS
in V1.
• Identify the J point.
• Draw a horizontal
line.
• Triangle pointing up
indicates RBBB.
• Triangle pointing
down indicates LBBB.
LEFT BUNDLE BRANCH
BLOCK
RIGHT BUNDLE BRANCH
BLOCK
CONDUCTION
ABNORMALITIES
• Conduction
Abnormalities
– Hemiblocks
• Left Anterior
Hemiblock
CONDUCTION
ABNORMALITIES
• Conduction
Abnormalities
– Hemiblocks
• Left Posterior
Hemiblock
CHAMBER ENLARGEMENT
Chamber Enlargement
Atrial Enlargement
Ventricular Hypertrophy
Causes
Right-sided enlargement and hypertrophy, usually
secondary to long-term pulmonary disease.
Left-sided enlargement and hypertrophy, usually
secondary to long-term hypertension.
RIGHT ATRIAL
ENLARGMENT
LEFT ATRIAL
ENLARGEMENT
RIGHT VENTRICULAR
ENLARGEMENT
LEFT VENTRICULAR
ENLARGEMENT
Time to Practice . . . .