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.