Arrhythmia and Heart Block Rhythms Flashcards

Flashcards about Arrhythmia and Heart Block Rhythms

Heart Block Rhythms

Occur when electrical activity has difficulty traveling along normal conduction pathway; ventricular depolarization is absent or delayed.

First Degree AV Block: Characteristics

Delay in electrical conduction from SA node to AV node, causing a longer than normal PR interval.

First Degree AV Block: Criteria

P-P and R-R intervals are regular, rate is 60 to 100 bpm, consistent P wave morphology, PR interval greater than 0.20 second, and normal QRS duration.

True or False: A first degree atrioventricular block prevents impulses generated in the SA node from reaching the ventricles.

A first degree AV block causes a delay in electrical conduction, but the impulse is not completely blocked from reaching the ventricles.

What are the distinguishing characteristics of first degree AV block?

The PR interval is constant and measures greater than 0.20 second.

Second Degree AV Block, Type I

Some electrical impulses are blocked at AV junction region.

Second Degree AV Block, Type I: Characteristics

Impulses are conducted with increasing difficulty; PR interval increases until a QRS complex is blocked, then resets in a regular pattern.

What are the distinguishing characteristics of second degree AV block, type I?

It has a cyclical prolonging PR interval until the QRS is blocked; then the cycle resets and begins again.

Second Degree Atrioventricular (AV) Block, Type II (Mobitz II)

AV node selects electrical impulses to block; pattern may or may not exist; frequently progresses to third degree AV block.

What is the mnemonic to help you remember how to distinguish between second degree AV block, types I and II?

“Lengthen, lengthen, drop equals Wenckebach”

Third Degree AV Block (Complete)

All electrical impulses originating above the ventricles are blocked; no correlation between atrial and ventricular depolarization; P-P and R-R intervals are dissociative.

What are the distinguishing characteristics of third degree heart block?

The P-P and R-R intervals are regular but firing at different rates.

Key features of Rhythms Originating from the Ventricles

Wide (> 0.12 seconds in duration) and bizarre QRS complexes, T waves in the opposite direction of the R wave, and absence of P waves.

Premature Ventricular Complexes (PVCs)

Ectopic impulse that occurs early in the cycle and originates from the ventricles.

Unifocal PVCS

PVCs have similar shape (only one irritable focus present)

Multifocal PVCS

PVCs have different shapes.

Occasional PVC

Less than 6 PVCs per minute

Frequent PVCS

6 or more PVCs per minute

Bigeminy

Every other beat is a PVC.

Trigeminy

Every third beat is a PVC.

Quadgeminy

Every fourth beat is a PVC.

R-on-T PVC

PVCs begin on downslope of T wave.

Coupling/Couplet

Back-to-back PVCs.

Run of Ventricular Tachycardia

3 or more PVCs in a row.

What is a premature ventricular complex?

A premature ventricular complex is an early QRS complex that occurs without a P wave and has a wide and bizarre appearance.

Agonal Rhythm

Occurs when all of the pacemakers in the heart have failed; the heart is dying; ventricular rate is less than 20 beats per minute.

What is the ventricular rate in a patient who has an agonal rhythm?

Less than 20 beats per minute

Idioventricular Rhythm

Impulse created by the ventricular pacemaker; presents with the classic wide QRS complex, slow ventricular rate, and absence of P waves.

What are the differentiating characteristics of idioventricular rhythms?

Idioventricular rhythms have a slow ventricular rate of 20 to 40 bpm, with wide and bizarre QRS complexes and an absence of P waves.

Accelerated Idioventricular Rhythm

Impulse created by the ventricular pacemaker; the heart rate is faster than an idioventricular rhythm; QRS complex is wide and bizarre and P waves are absent.

How is an accelerated idioventricular rhythm different from an idioventricular rhythm?

Accelerated idioventricular rhythm occurs at a rate of 40 to100 bpm, and idioventricular rhythm occurs at a rate of 20 to 40 bpm.

Ventricular Tachycardia

Three or more PVCs occur in a row; ventricles are in continuous state of contraction-relaxation.

Torsades de Pointes

Depolarization impulses move to different locations in one ventricle, then the other; occurs due to electrolyte deficiencies.

Identify this rhythm.

Torsades de Pointes, a type of ventricular tachycardia in which the impulse origination points move around from ventricle to ventricle

Ventricular Fibrillation

Chaotic, asynchronous electrical activity within ventricular tissue; ventricle walls quiver, preventing ejection of blood; no cardiac output.

What is ventricular fibrillation?

The absence of organized electrical activity in the ventricles, resulting in a disorganized or chaotic tracing.

Asystole

Absence of ventricular activity and depolarization; no electrical activity is present in the myocardium. Always confirm asystole in at least two different leads to rule out “fine” ventricular fibrillation.

Why is asystole confirmed in at least two different leads?

To rule out “fine” ventricular fibrillation

Electronic Pacemakers

Also known as artificial pacemakers; deliver electrical impulse to myocardium, causing cells to depolarize; mimic normal pacemaker of the heart.

Pacing Spike

Thin spike on ECG tracing indicating electrical current from pacemaker; evidence of depolarization should appear after the spike, depending on type of pacing.