Transcript ECG Lecture Chapter 12 for 4/18 or 4/20 lecture

Chapter 12 – Miscellaneous
Conditions
Artifact
Digitalis Effect
Pericarditis
Early Repolarization
Low Voltage
Hypo- and Hypercalcemia
Hyperkalemia
Wolff-Parkinson-White
Pulseless Electrical Activity
Artifact
• Causes and Cures
• Inspect multiple leads
• Figure 12.1, page 135
Digitalis Effect
•
•
•
•
Often used to treat CHF
U shape depression of the ST segment.
Does not indicate toxicity
Problem: Difficult in determining if ST changes are caused by
ischemia or Digitalis.
• Toxicity problems include seizures, anorexia nervosa, nausea,
tremors, etc.
• Figure 12.2, page 136
Early Repolarization
• > 1mm ST segment elevation in a normal
person (ST ELEVATION = Infarct)
• Normal variant caused by unusually fast
repolarization of the ventricles.
• Brief upward deflection in one or more leads
at the J point (where the QRS complex ends
and ST segment begins).
• Does not occur in multiple leads or change
over time.
• Figure 12.4, Page 138
Low Voltage
• Criteria: Total QRS < 5 mm voltage in each limb
lead and < 15mm voltage in each precordial lead.
• Surface current recorded by electrodes is below
normal.
• May be normal or due:
– to subcutaneous fat
– Increased intrathoracic air volume (emphysema)
– Infarction (death of myocardial cells)
Possible Low Voltage
Normal ECG
Hypo- and Hypercalcemia
• Hypocalcemia prolongs the QT interval. No specific
guidelines.
• Hypercalcemia shortens the QT interval (beginning of
the T wave comes right after the QRS.
• QT INTERVAL: Beginning of QRS complex to the end of
the T wave
• Figure 12.4, Page 138
Hyperkalemia
• Elevated plasma potassium.
• Tall Peaked waves initially (T waves should only
be 1/3 the height of the QRS).
• With continued rise in potassium T waves remain
tall and peaked and what appears to be an
idioventricular rhythm appears.
• Figure 12.7, page 140. A: Early, B: Progressing
Progressing Hyperkalemia., Figure 12.7, Page 140.
Ideoventricular rhythm: Wide QRS, impulse is transmitted through the ventricles.
Wolff Parkinson-White Syndrome
• Some patients have an accessory or additional pathway
to the AV Node from the SA Node.
• May be present all the time or intermittent.
• Depolarization from Atria to Ventricles travels two
paths – Bundle of His and now Kent Bundle (this
pathway is more RAPID). No Delay.
• They then join together at the beginning of Ventricular
depolarization.
Wolff-Parkinson-White
• Figure 12.10, Page 143
• Three characteristics:
– A: Short PR interval
– B: Wide QRS complex
– C: Delta Wave
• These characteristics are not
present in all leads.
Not in book
WPW
• Can cause a rapid heart rate (tachycardia).
• Can be congenital but occurs mostly in adults age 3040.
• Therapy can include the valsalva manuever,
medications, cardioversion, ablation or surgery.
Many people with this syndrome who have symptoms or episodes of tachycardia (rapid
heart rhythm) may have dizziness, chest palpitations, fainting or, rarely, cardiac arrest.
Other people with WPW never have tachycardia or other symptoms.
Figure 12.11, page 144
Figure 5.4 Clinical Exercise Physiology Textbook
Wolff Parkinson-White Syndrome
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What is this rhythm?
Pulseless Electrical Activity - EMD
• Normal or somewhat normal ECG but mechanical
functioning is severely impaired. Can be any
rhythm.
• The ECG and contractile activity are closely coupled
but are not synonymous.
• Perfusable rhythm but no pulse or measureable
blood pressure.
• Must correlate with clinical activity.
WPW
• If there's an extra conduction pathway, the electrical signal may
arrive at the ventricles too soon. This condition is called WolffParkinson-White syndrome (WPW). It's in a category of electrical
abnormalities called "pre-excitation syndromes."
• It's recognized by certain changes on the electrocardiogram, which
is a graphical record of the heart's electrical activity. The ECG
will show that an extra pathway or shortcut exists from the atria to
the ventricles.
• Many people with this syndrome who have symptoms or episodes
of tachycardia (rapid heart rhythm) may have dizziness, chest
palpitations, fainting or, rarely, cardiac arrest. Other people with
WPW never have tachycardia or other symptoms. About 80 percent
of people with symptoms first have them between the ages of 11
and 50.