Chapter 3 Flashcards
Is this EKG normal?
A typical rhythm strip. It can be as short or as long as you need to decipher the rhythm. This particular strip represents a continuous recording of lead II in a patient with normal sinus rhythm, the normal rhythm of the heart.
When would you see EKG like this?
A surgically implanted event monitor recording in a patient with syncope. The small vertical dashes mark off intervals of 1 second. The 3-second pause near the bottom of the strip activates the monitor, which then stores the EKG tracing from several minutes before to several minutes after the activation point. The stored recording is then downloaded and printed at a later time. In this patient, the long pause was associated with a near-syncopal episode.
What’s the rate of the following EKG?
Every QRS complex is separated by five large squares (1 second). A rhythm occurring once every second occurs 60 times every minute.
What’s the rate for this one?
The R waves are slightly more than four squares apart—let’s say four and one-quarter. The rate must therefore be between 60 and 75 beats per minute. If you guess 70, you’ll be close. Alternatively, divide 300 by four and one-quarter and get 70.6 beats per minute.
Is this NSR? If not, what is it?
No. It’s ST
Is this NSR? If not, what is it?
No. It’s SB
What does this picture illustrate?
Sinus arrhythmia. The heart rate accelerates with inspiration and slows with expiration.
Is this NSR? If not, what is it?
A beautiful example of sinus arrhythmia. You may have also noticed the prolonged separation of each P wave from its ensuing QRS complex (i.e., a prolonged PR interval). This represents a conduction delay called first-degree atrioventricular (AV) block; it is discussed in Chapter 4.
Is this NSR? If not, what is it?
Sinus arrest occurs after the third beat. The fourth beat, restoring electrical activity to the heart, is a junctional escape beat. Note the absence of a P wave before this last beat.
Is this NSR? If not, what is it?
Junctional escape. The first two beats are normal sinus beats with a normal P wave preceding each QRS complex. There is then a long pause followed by a series of three junctional escape beats occurring at a rate of 40 to 45 beats per minute. Retrograde P waves can be seen buried in the early portion of the T waves. Retrograde P waves can occur before, after, or during the QRS complex, depending on the relative timing of atrial and ventricular depolarization. If atrial and ventricular depolarization occur simultaneously, the much larger QRS complexes will mask the retrograde P waves.
Know the rate range for each ectopic signal region
What’s the difference between B and C?
(B) Sinus arrest. The sinus node falls silent. No current is generated, and the EKG shows no electrical activity. (C) Sinus exit block. The sinus node continues to fire, but the wave of depolarization fails to exit the sinus node into the atrial myocardium. Again, the EKG shows no electrical activity; there is not sufficient voltage to generate a detectable P wave.
What does this illustrate?
(A) Normally, the sinus node drives the heart. (B) If another potential pacemaker (e.g., the AV junction) is accelerated, it can take over the heart and overdrive the sinus node.
What does this illustrate?
A model showing how a reentrant circuit becomes established. (1) Normally, pathways A and B (any two adjacent regions of cardiac function) conduct current equally well. (2) Here, however, conduction through pathway B is temporarily slowed. Current passing down A can then turn back and conduct in a retrograde fashion through B. (3) The reentry loop is established.
What’s the “Four Questions”?
- Are normal P waves present?
- Are the QRS complexes narrow or wide?
- Is there a QRS complex following every P wave?
- Is the rhythm regular?
Is this NSR? If not, what is it?
The third beat is an atrial premature beat. Note how the P wave contour of the premature beat differs from that of the normal sinus beat.
Is this NSR? If not, what is it?
The third beat is a junctional premature beat. There is no P wave preceding the premature QRS complex.
Is this NSR? If not, what is it?
The third beat is an atrial premature beat. The P wave is shaped differently from the other, somewhat unusual-looking P waves, and the beat is clearly premature.
Is this NSR? If not, what is it?
A junctional premature beat. The third beat is obviously premature, and there is no P wave preceding the QRS complex
Is this NSR? If not, what is it?
The third beat is a junctional escape beat, establishing a sustained junctional rhythm. It looks just like a junctional premature beat, but it occurs late, following a prolonged pause, rather than prematurely.
Is this NSR? If not, what is it?
The fourth P wave(the 3rd T wave is really small, then the more prominant little wave right after 3rd T is the 4th P) is a blocked PAC. Sometimes a PAC may occur sufficiently early that the AV node will not have repolarized from previous beat and will therefore be unable to conduct the atrial beat into the ventricles. The EKG may then show only a P wave w/o an ensuing QRS.
Is this NSR? If not, what is it?
PSVT, simultaneous activation of the atria and ventricles; therefore, the retrograde P waves are lost in the QRS complexes
Is this NSR? If not, what is it?
PSVT; this one shows a supraventricular tachycardia mimicking a more serious rhythm called ventricular tachycardia (VT)
Is this NSR? If not, what is it?
PSVT; retrograde P waves can be seen
Is this NSR? If not, what is it?
PSVT; A good example of the pseudo-R’ configuration in lead V1 representing the retrograde P waves (arrows) of PSVT
What’s the most common cause of PSVT?
The AV node is usually the site of the reentrant circuit that causes the arrhythmia (hence it’s often referred to as AV nodal reentrant tachycardia). Atrial depolarization therefore occurs in reverse, and if P waves can be seen, their axis will be shifted nearly 180° from normal (retrograde P waves).
How does carotid massage work?
The carotid sinus contains baroreceptors that influence vagal input to the heart, primarily affecting the sinus node and AV node. Stimulation of the right carotid baroreceptors primarily stimulates sinus node vagal input, whereas stimulation of the left carotid baroreceptors is more likely to affect the vagal input to the AV node.
What does this illustrate?
An episode of PSVT is broken almost at once by carotid massage. The new rhythm is a sinus bradycardia with a rate of 50 beats per minute.
What does this illustrate?
Atrial flutter. Carotid massage increases the block from 3:1 to 5:1.
Is this NSR? If not, what is it?
Atrial flutter. Lead II shows classic negative deflections.
Is this NSR? If not, what is it?
Atrial fibrillation with a slow, irregular ventricular rate
Is this NSR? If not, what is it?
atrial fibrillation. In the absence of a clearly fibrillating baseline, the only clue that this rhythm is atrial fibrillation is the irregularly irregular appearance of the QRS complexes.
What’s this one?
Multifocal atrial tachycardia. Note that (1) the P waves vary dramatically in shape; (2) the PR intervals vary; and (3) the ventricular rate is irregular.
Is this NSR? If not, what is it?
PAT. P waves are not always visible, but here they can be seen fairly easily. You may also notice the varying distance between the P waves and the ensuing QRS complexes; this reflects a varying conduction delay between the atria and ventricles that often accompanies PAT
What’s this?
A PVC. Note the compensatory pause before the next beat.
What’s this called?
Bigeminy. PVCs and sinus beats alternate in a 1:1 fashion.
What’s going on here?
Beats 1 and 4 are sinus in origin. The other three beats are PVCs. The PVCs differ from each other in shape (multiform), and two occur in a row.
What happened here?
A PVC falls on the T wave of the second sinus beat, initiating a run of VT.
What’s this called? what’s its rate?
Ventricular tachycardia. The rate is about 200 beats per minute.
What’s going on here?
Ventricular tachycardia degenerates into ventricular fibrillation.
Is this NSR? If not, what is it?
Accelerated idioventricular rhythm. There are no P waves, the QRS complexes are wide, and the rate is about 75 beats per minute.
What’s this one called?
Torsade de pointes. The QRS complexes seem to spin around the baseline, changing their axis and amplitude.
What does this illustrate?
The one circumstance that a supraventricular beat produces wide QRS complexes.
(A) A premature atrial impulse catches the right bundle branch unprepared. Conduction down the right bundle is blocked but proceeds smoothly down the left bundle. (B) Right ventricular depolarization occurs only when the electrical forces can make their way over from the left ventricle—a slow, tedious process. This mode of transmission is very inefficient and results in a wide, bizarre QRS complex. (C) The third P wave is a premature atrial contraction. It is conducted aberrantly through the ventricles, generating a wide, bizarre QRS complex.
It looks like a PVC, but the 3rd beat has P wave
How can you tell if the following is VT or PSVT?
- If you know anything about the Pt; VT is usually seen in diseased hearts, and PSVT is usually in normal hearts.
- Carotid massage can terminate PSVT, yet no effect on VT.
- If you have a central line in. 75% of VT is accompanied by AV dissociation, where the atria and ventricles beat independently (you may see that on EKG P wave to QRS complex ratio is not 1:1). So every so often the atria will contract against closed mitral and tricuspid valves. This results in cannon A waves. But you won’t see that in PSVT.
- You may see fusion beats in VT only. Example below, The second beat is a fusion beat, a composite of an atrial (sinus) beat (beats 1 and 4) and a PVC beat (beat 3).
- PSVT has retrograde P waves, with a positive peak in lead aVR and a negative peak in lead II
What’s going on here?
The Ashman phenomenon. The fourth beat looks like a PVC, but it could also be an aberrantly conducted supraventricular beat. Note the underlying atrial fibrillation, the short interval before the second beat, and the long interval before the third beat—all in all, a perfect substrate for the Ashman phenomenon.
What happened here?
The heart rate of a 72-year-old woman is rescued from VT by a shock delivered by an implantable cardioverter–defibrillator.
What’s going on here?
Sick sinus syndrome (SSS), aka the bradytachycardia.
This EKG starts with AFib, a long pause later it turns into ventricular escape beats (the QRS are wide and bizarre, no P waves, and the rate is about 33bpm), finally the SA node ticks in at a slow rate of 50bpm.
The SSS is typified by alternating episodes of a supraventricular arrhythmia, such as AFib, and bradycardia. Often, when the supraventricular arrhythmia terminates, there’s a long pause before the SA node fires again (hence the sick sinus)
Identify the following EKG
Bigeminy. Junctional beats (w/ narrow QRS and no P wave) occuring in a 1:1 ratio with PVCs
Identify the following EKG
PVC landed on the previous T wave and triggered a run of VT
Ifentify the following EKG
PVC landed on the previous T wave and triggered persistant VT which turned into Torsade de Pointes
