Exam II Flashcards
Rate of Atrial foci
60-80/min
Rate of Junctional (AV) Foci
40-60/min
Rate of Ventricular Foci
20-40/min
What has to occur for a beat to be considered an escape beat?
Must be preceded by a pause. This is due to a pause in the previously dominant pacemaker
What has to occur in an escape rhythm?
Cessation of the previously dominant pacemaker
What does a retrograde P wave look like (what leads)? What type of beat is this?
P wave that is positive in the aVR lead and negative in Lead II (normal P wave is exactly the opposite.) This is a type of junctional beat
What is the length of a PR interval that follows a junctional beat.
Wide, greater than 120 ms
Where can a retrograde P wave be seen relative to the QRS complex?
Can occur before or after the complex, or can be buried in it.
What does it mean if a QRS complex is NOT prolonged (i.e. less than 120 ms)?
Ventricular depolarization MUST have occurred above the ventricles (i.e. the normal Purkinje-His system)
What is the difference between a premature beat and an escape beat?
They differ by timing of occurrence: An escape beat occurs after a pause due to the SA node (and/or atrial foci) failing to fire (escape from overdrive suppression), whereas a premature beat is due to an irritable automaticity focus that fires spontaneously (extrasystole)
Define Bigeminy (Trigeminy, Quadrigeminy).
Every other (every third, every fourth) beat is pre-mature
What is a Non-conducted pre-mature atrial beat? What does the QRS complex look like?
What happens after it?
Pre-mature atrial beat occurs when an irritable atrial focus fires early during the ventricular refractory period.
QRS complex: NONE!
After pre-mature atrial beat, the SA node resets and continues as normal.
What is the difference between complete and incomplete compensatory pause?
Complete: The beat after the aberrant beat occurs where it normally would. SA node does not “reset” in time with aberrant beat
Incomplete: The premature firing of a beat causes the beat after it to be out of sync with the normal rhythm. The SA node with reset “in step” with the premature atrial beat.
Which type of beat is usually followed by a compensatory pause?
PVCs
What is the difference between unifocal and multiform PVCs on an EKG?
Unifocal: Come from one place and all look the same
Multiform: Each irritable focus produces its own unique PVC, which makes the EKG look like a mess.
How long is a “sustained” arrhythmia?
Greater than 30 s
Rate of bradycardia?
< 60 bpm
Rate of tachycardia?
> 100 bpm
Rate of flutter?
250-350 bpm
Rate of fibrillation?
350-450 bpm
Define Supraventricular Tachycardia.
General term for tachy that originates above the ventricles.
Is tachycardia a disorder of impulse propagation or formation?
Formation.
What causes tachyarrhythmias?
Enhanced automaticity (irritability) and triggered activity.
Define triggered activity.
Pacemaker activity which is dependent upon a preceding impulse or series of impulses (initiated by afterdepolarizations)
What is torsade de pointe?
What causes it?
“Twisting of the points:” Polymorphic ventricular tachycardia (VT) which is preceded by marked prolongation of the QT interval. Seen as oscillations twisting around the baseline.
Due to triggered activity (from early afterdepolarizations) related to “R on T” phenomenon, facilitated by marked QT prolongation
What phenomenon precedes torsade de pointe?
Prolonged QT interval
What is the normal estimation for QT interval?
The QT interval should be less than half of the R-to-R interval which contains that QT interval.
Bazett formula…
QTC = measured QT x (R-to-R int. (sec.))-1/2
What are the 3 things that distinguish a wandering pacemaker on EKG?
How does this differ from multifocal atrial tacchycardia?
- Highly variable P waves
- Atrial rate less than 100
- Irregular ventricular rhythm
In MAT, Atrial rate is greater than 100
What occurs in Wolff-Parkerson-White Syndrome?
Initial ventricular depolarization from the bundle of Kent produces a delta wave on EKG.
What is the ratio of P waves to QRS complexes in First Degree AV Block?
1:1
What does the PR interval look like for First Degree AV Block?
PR Interval is FIXED
“A PR Interval of more than _________ seconds indicates First Degree AV Block.”
.2 Seconds (i.e. Greater than 5 blocks)
Where does Type I Second degree AV Block occur? How about Type II?
Type I occurs IN the AV Node and Type II are farther down from the AV Node
What are the two ways Type I SECOND DEGREE AV Block can present?
- Cluster of beats separated by “missed” beats
2. 2 P waves for every 1 QRS complex (no clusters), with regular PR intervals
What is characteristic of Second Degree AV block Type II ?
- There are more P waves then QRS complexes
- All P waves that immediately precede QRS complexes have equal PR intervals
- At times, there may be a fixed ratio of P waves to QRS complexes (e.g. 2-to-1*, 3-to-1, or 4-to-1, etc.)
What degree is complete AV Block?
Third Degree
What occurs with complete AV Block?
When the conduction of the supraventricular depolarizations is completely blocked, an automaticity focus escapes to pace at its inherent rate.
What do you have if the P waves to QRS ratio is 2:1 and PR intervals are all the same?
It’s Second Degree AV Block. Could be Type I or type II.
What do you have if the P waves to QRS ratio is 2:1 and PR intervals are variable?
Complete AV Block
What lead do you use to assess RBBB and what do you see?
Lead I and you see the “Slurred S Wave”
What is another less effective lead for seeing RBBB and what do you see?
V1 and you “Bunny Ears” or R-S-R’ complex
How do you differentiate between complete and incomplete RBBB?
Complete: QRS complex is greater than or equal to .12 sec
Incomplete: QRS is between .1-.12 sec
What characteristic feature do you see in V1 or V2 in LBBB?
Notching of the “S wave”
What are 3 things you see in LBBB?
- Broad, sometimes notched R wave in leads I (and V6)
- Absent q waves in leads I, aVL, and V6
- Wide and deep S waves in lead V1
Criteria the same as RBBB for complete and incomplete.
Which to leads are you assessing for Left Ventricular Hypertrophy? If they are more than ___ mm, it’s considered LHV.
Depth of V1 and height of V5
If together they are greater than 35 mm, it’s considered LVH
To what age does the hypertrophy criteria apply?
Pts over the age of 40.
What do the Left Chest Leads show in LVH?
ST segment depression and inverted T wave
If the inverted T wave is symmetrical, what does this indicate?
Ischemia
What are the 3 criteria that suggest RVH?
- Right axis deviation (> 110°)
- R/S > 1 in lead V1
- Deep S wave in lead V6
What waves in what leads to you inspect for an atrial abnormality?
Look at the P waves of Lead II and V1 for amplitude, duration, and morphology
What does a normal P wave look like in the V1 lead?
- Biphasic
- First half of P wave is less than 1.5 mm high
- Second half of P wave is less than 1 mm deep
What does a normal P wave look like in Lead II?
- P wave is upright
- less than 2.5 mm high
- No more than 120 ms in duration (3 blocks)
What do the P waves look like in a RIGHT atrial abnormality? (V1 and Lead II)
V1: Over 1.5 mm high (initial portion)
Lead II: Over 2.5 mm high
(If peaked = p pulmonale)
What do the P waves look like in a LEFT atrial abnormality? (V1 and Lead II)
V1:
> 1.0 mm deep and > 1.0 mm wide (terminal negative (LA) portion)
OR
Lead II:
> 120 msec in duration (> 3 mm wide)
If notched, referred to as “p mitrale”
What do the P waves look like in a BIATRIAL abnormality? (V1 and Lead II)
In sinus rhythm, the P waves:
Meet the criteria for right atrial abnormality in lead V1 and/or lead II
AND
Meet the criteria for left atrial abnormality in lead V1 and/or lead II
