Basics of EKG part II Flashcards
What is the normal duration and amplitude of a P wave
- duration: 0.06-0.10 sec
- amplitude: 0.5 - 2.5 mm
If amplitude of P wave is > 2.5 mm it suggests
- right atrial enlargement: called “P pulmonale”
If width of P wave is > 0.10 sec, it suggests
- Left atrial enlargement
- called “P mitrale”
impulses arising from the atria but not the SA node, will produce what
- different looking P waves
In rapid rates, the P wave is likely buried where
- in the T wave of the preceeding beat
- when this occurs, T waves are often peaked, notched, or larger than normal
What type of P waveform is produced when the atria fires rapidly from one site at a rate of 250-350 bpm
- “F” waves or flutter waves
- often described as a saw tooth pattern
- with atrial flutter, an ectopic site in the atria fires at rate 250-350 bpm
What happens to P waves when atria fire rapidly from many sites at a rate > 350 bpm
- “fibrillatory” waves (not getting coordinated contraction)
How are inverted P waves produced
- when a P wave arises from the lower right atrium near the AV node, the left atrium, of the AV junction
- results in retrograde depolarization of the atria
inverted P waves can have what relationship to QRS complex
- immediately preceed, occur during, or follow the QRS complex
more P waves than QRS complexes indicates what
- the impulse was initiated in the SA node or atria but was blocked and did not reach the ventricles
While there is only one Q wave, there can be more than one R and S wave. What are the second R or S wave called? What if they are small?
- R’ or S’: (R prime or S prime)
- use lower case: “r” or “s”
- small: less than 1 big box
how do you measure QRS complexes
- starting point is where first wave of complex starts to move away from baseline
- ending point is where last wave of complex begins to level out at, above, or below baseline
tall QRS complexes are usually caused by what heart condition
- hypertrophy of one or both ventricles
low voltage QRS complexes are seen in what patient conditions
- obese patients
- hypothyroid patients
- pericardial effusion
wide QRS complexes are often a result of
intraventricular conduction defect
What is an aberrant conduction
- occurs when electrical impulses reach the bundle branch while it is still refractory after conducting a previous electrical impulse
- results in impulse traveling down the unaffected bundle first, followed by stimulation of the other bundle branch
- causes QRS complex to appear wider than normal
List the five step process of ECG analysis
- rate
- regularity
- P waves
- QRS complexes
- PR intervals
What does the PR interval denote
- depolarization of the heart from the SA node through the atria, AV node and His-purkinje system
how is PR interval measured
- distance from beginning of P wave to the beginning of the Q wave
what causes short PR intervals
- impulse originates in the atria close to the AV junction or in the AV junction
- impulse arises from a supraventricular site but travels through abnormal accessory pathways to the ventricles
- leads to premature ventricular depolarization -> preexcitation
what conditions cause longer PR intervals
- there is a delay in impulse conduction through the AV node
What can cause varying PR intervals
-
wandering atrial pacemaker
- pacemaker site moves from beat to beat causing the P waves to appear different and the PR intervals to vary
what condition is characterized by PR intervals that are progressively longer until a QRS complex is dropped and then the cycle repeats
2nd degree AV heart block, type I
