6: Rhythm Identification Flashcards
What distinguishes sinus node reentry from sinus tachycardia?
It is only the abrupt onset and offset that distinguishes sinus node reentry from sinus tachycardia.
What is the difference between Mobitz 1 and 2?
In both there are dropped QRS Complexes, but only in Mobitz 1 is there a lengthening of the PR Interval.
Looking at different leads helps make the diagnosis. Delayed and abnormal activation of the left ventricular myocardium and a diffuse slowing of conduction throughout the left ventricle lead to the following changes on the ECG: there is a tall monophasic and broadened R wave in leads I, aVL, and V6 instead of a septal Q wave; there is a QS complex which is abnormal and widened in V1, instead of a small initial R wave, due to septal activation; the QRS interval is prolonged >0.12 seconds; myocardial repolarization changes, including T-wave inversion and ST segment depression, are evident.
Complete LBBB
Every other beat is a PVC in a regular pattern.
Ventricular Bigeminy
Sinus rhythm with a rate between 60 and 100.
Normal Sinus Rhythm
Looking at different leads helps make the diagnosis. The initial myocardial activation is normal; thus, there is
a normal septal q wave in leads I and V6, followed by a
tall R wave. Similarly, there is a normal initial septal R
wave followed by a deep S wave in leads aVR and V1.
However, the subsequent abnormal right ventricular
activation occurs from left to right and goes through the ventricular myocardium instead of the His-Purkinje
system; thus, there will be a tall and broad secondary R
wave (R’) in leads aVR and V1 (a RSR’ complex), and
a deep and broad S wave in leads I and V6. The width
of the QRS complex is >0.12 seconds.
Complete RBBB
Impulses discharged in the SA node are either not conducted to the atria or are done so with a delay.
Sinoatrial Exit Block
Every 3rd beat is a PVC in a regular pattern.
Ventricular Trigeminy
What do you look for on an EKG in atrial flutter?
Flutter waves, which have a predictable, sawtooth appearance.
What causes PACs?
Different states of excitability promote occurrence.
Delay of conduction through the left bundle leads to slight prolongation of the QRS Complex (0.10-0.12 seconds). Initial septal activation is normal and the QRS Complexes resemble those associated with normal conduction.
Incomplete LBBB
What causes a sinus pause?
Intermittent failure of the sinus node impulse generation.
Complete loss of P Wave functioning. Narrow QRS. Slower rhythm.
Junctional Dysrhythmias
AV node gets excited and causes HR >100.
Junctional Tachycardia
Progressive lengthening of the PR Interval followed by a dropped QRS Complex.
Second-Degree Block 1 (Mobitz 1, Wenckebach)
Can occur when the backup pacemaker fails and now using the backup backup. Ventricles fire at a regular rate. QRS Complexes are wide and no P Waves.
Accelerated Idioventricular Rhythm
P Wave fires prematurely. A very early one can block the QRS Complex or cause it to be aberrantly conducted.
Atrial Premature Complexes (APCs or PACs)
Is second-degree Mobitz 1 or 2 more alarming?
Mobitz 2, b/c it often needs a pacemaker if the rhythm can’t be reversed.
A negative QRS complex in lead I and positive QRS complex in aVF is characteristic. The QRS duration is normal.
Left Posterior Hemiblock
Manifests as a long RR cycle length, which is longer than the RR interval of the underlying sinus rhythm.
Sinus Pause
Short PR Interval (<0.12 seconds) which represents a fusion beat. Delta Wave. Broad QRS Complex.
Wolff-Parkinson-White Syndrome
The AV junctional rate speeds up to 61-99 and takes over the pacemaking function.
Accelerated Junctional Rhythm
PR Interval is prolonged (>0.20). Delay in conduction.
First-Degree AV Heart Block
P Waves and QRS Complexes dissociated. Both march along at their own rhythm. Usually requires pacemaker.
Third-Degree (Complete) Heart Block
