Download Lecture 19 EKG – Electrocardiogram

Lecture 19
The Electrocardiogram
EKG/ECG
Holdorf PhD, MPA, RDMS, RVT
Normal complex
• P wave-atrial systole
• QRS complex – ventricular systole (depolarization)
• T wave – Ventricular diastole (repolarization)
Hint:
• 1 small box = 0.04 seconds
• 1 big box = 0.2 seconds
• 5 big boxes = 1 second
• Normal values:
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R-R interval: between 3 to 5 big boxes (60-100 beats/minute
QRS complex: less than 3 little boxes (less than .12 seconds
PR interval: Less than 1 big box (less than 0.2 seconds)
The ECG has which of the following rhythms?
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Normal sinus rhythm (via the SA node)
Method of analysis
Find the P waves (they’re the big ones)
Assess at the QRS duration (< little boxes)
Assess at R-R interval: between 3 and 5 big boxes
Look for P preceding each R wave
Check the PR interval (less than I big box)
ECG: Common abnormalities
• Normal sinus rhythm (R-R interval between 3 and 5 big boxes
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60-100 BPM
P-wave preceding each QRS
PR interval and QRS complex within normal limits
SINUS BRADYCARDIA (more than 5 big boxes
Heart rate less than 60 BPM
Otherwise all other findings of normal sinus rhythm
SINUS TACHYCARDIA
Less than 3 big boxes
Heart rate greater than 100 BPM
Otherwise all other findings of normal sinus rhythm
If the cardiac electrical impulse is in the bundle
branches, where are you on the ECG tracing?
The Purkinje fibers
The bundle of His?
• Answer for all
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PR interval
ARRHYTHMIAS OVERVIEW
• P waves
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Present or absent
Relationship to QRS
• PR Interval
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Normal < 0.20 sec.
• QRS Duration
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Normal <0.12 sec.
Sinus arrhythmia
Irregular rhythm related to respiration (increase rate
with inspiration; decrease rate with expiration
In sinus arrhythmia, the heart rate varies with the phase of respiration. The
heart rate typically increases during inspiration and decreases during
expiration. Therefore, as observed, the R-R interval is longer during
expiration. These changes are mediated through vagal reflexes. Sinus
arrhythmia is more common in young healthy athletes.
Atrial fibrillation
• Rapid discharge of multiple foci in the atria, no discrete P waves, irregularly
irregular rhythm.
Atrial flutter
Rapid discharge of an ectopic focus for atrial
depolarization. Only occasional stimulus will
penetrate AV node. Saw-tooth pattern.
Ventricular Fibrillation
Chaotic rhythm in which there are multiple areas exhibiting varying degrees of
depolarization and repolarization. Absence of R-waves
Premature Beats
Atrial (PAC)
Electrical impulse originating in the atria outside of the SA node.
Produces an abnormal P wave earlier than expected.
Ventricular
(PVC-premature ventricular contractions)
Ectopic ventricular focus (anatomic source) produces an abnormal ventricular
complex (usually larger and wider than normal complex).
A PVC occurring every other beast is called bigeminy
A PVC occurring every 3rd beat is trigeminy
Ventricular tachycardia
Three or more beast of ventricular origin (PVC) occurring in
succession.
Bundle Branch Block
Right BBB= delay in depolarization of the right
ventricle: QRS > 0.12 sec.
Left BBB
Delay in depolarization of the left ventricle
V5 or V6 QRS > 0.12 sec.
Heart Block
1st degree AV Block
PR interval >0.20 sec. (more than I big box) and of the same duration in every cycle. R-R
interval is normal.
2nd degree AV Block
PR interval >0.20 sec. and gets progressively longer until a QRS is dropped.
In other words, the P moves further away from the QRS.
3rd degree AV block
• Complete absence of conduction between the atria and ventricles (also
known as complete heart block (CHB).
• P-R interval gets progressively shorter.
• In other words, the P marches straight into the QRS complex.
Pacemakers
A high voltage, short duration pacing spike seen
before each ventricular conduction pattern.
Exercise Stress Testing
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Indications
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To aid in the diagnosis of chest pain
To determine the severity and prognosis of CAD
To guide post MI rehab
To evaluate cardiac arrhythmias
To screen high risk professionals or asymptomatic patients
Interpretation
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Morphology, degree and duration of ST-Segment depression (Mechanical / pressure)
ST = segment elevation
Duration of exercise
Exercise-induced hypotension or arrhythmias