EKG Interpretation Unrein Lecture Flashcards
•What is a P wave?
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•How can you tell that a P wave is from the sinus node?
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•How can you tell that conduction was initiated in the AV node?
What if the P waves all have different morphology?
- Atrial depolarization
- Regularity and uniform morphology
- P wave may be absent, inverted or post QRS-t complex
- Origin is from different places - multi-atrial foci. (not from SA or AV nodes) “Wandering P wave”
What is going on if you have absent or upside down and irregular, what is this called?
How do you know if a P wave is too large?
What is the significance of large P waves?
- Escape rythym or Junctional beat - irregular beats
- Height < 2.5 mm is NL, Width < 0.12 sec is NL, often biphasic
- Atrial Hypertrophy - due to pulmonary HTN, (with right vent. hypertrophy)
What is the PR interval duration?
What is a clinically important aspect of the PR interval?
- Length - 0.2 seconds
- AV nodal delay - and ventricular filling
- What is the QRS?
- Must it always have a Q wave to be a QRS complex?
What is the significance of a Q wave?
- Why is the QRS much more narrow than the P wave?
- What is the meaning of a QRS complex wider than 0.12 seconds?
- Ventricular depolarzition
- No, not always
- 1rst negative deflection in QRS, represents a vector moving away from sensing lead
- Happens rapidly, due to high speed conduction of His - perkinje system
- His-perkinje system is delayed, disturbed or by-passed with consequently diminished CO
What is the ST segment?
What significance does deviation from the baseline of ST reveal?
- Time between depolarization and repolarization of the ventricles, to finish cardiac ejection
- Reveals ischemia or tissue death from infarction
- What is the T wave?
- What is its normal appearance?
- Ventricular repolarization
- long (duration), short (amplitude), positive arc
•What is the QT interval?
What is the significance of a prolonged QT interval?
- Time from the beginning of Ventricular depolarization to repolarization. (Important segment clinically)
- Ventricular ejection is extended, due to V-fib (long term), heart become irritable
- How do you determine heart rate from the EKG?
- What is a rapid heart rate – a slow heart rate?
- Two ways…
a. # of QRS per two tick periods - 6 second rule
b. Memorize block correlations: distance in boxes… 1 box - 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, 5 boxes - 60 - Tachycardia - excess of 100 bpm; Bradycardia -
•How would you describe what part of the heart is initiating the conduction cycle if it is not sinus or junctional node?
atrial or ventricular rhythm
How do you tell if a non sinus or junctional conduction cycle is initiated supraventricularly or ventricularly?
Width of the QRS complex. Narrow = supraventricular, wide = ventricular (bypassing the his-perkinje conduction system)
- Describe the difference between automaticity and pacemaker function?
- What is a re-entry mechanism? Can you think of an example?
What does this lead to?
- bundle pathway is either too long, or repolarization happens too soon, or bypass nl conductive pathways, depolarizing wave hits polarized tissue when it shouldn’t. Creates ecg with “nice little saw tooth guys”
- Atrial flutter
What is a PAC (premature atrial conduction also known as APC)?
What is a PVC
- Atria contract before stimulation from the SA node
- Spontaneous contraction of the ventricles before stimulation, due to an alternative focus outside the normal conduction pathway.
What is fibrillation?
•What is atrial fibrillation? What is happening pathophysiologically?
V fib?
- Non-functional, irregularly irregular rythym.
- Failure to move blood into ventricles
- failure to eject blood, leading to death
- What is axis?
- What is a normal axis?
Average vector of conduction in the coronal plane
-30 to +110 (easiest to start with 0-90)
- What is rotation?
- What is the significance of rotation?
- Orientation of vectors along a transverse plane - orientation of the heart electrically
- Allows for assessment of
