VentricularVentricular RhythmsRhythms

Electrical impulses that originate from the ventricular conduction

system.

Ventricular RhythmsVentricular Rhythms

Bundle Branch Blocks (BBB) & Hemiblocks

Premature Ventricular Contractions (PVC)

Ventricular Escape Beat

Idioventricular Rhythm & AIVR

Ventricular Tachycardia

Ventricular Fibrillation

Ventricular Standstill

Asystole

Wide, Bizarre QRS’sSequential Depolarization

The electrical impulse originates from an ectopic site within one of the ventricles stimulating that side first, then depolarizes the other ventricle

Conduction time is slower than normal causing a wide, bizarre QRS complex

(> 0.12 sec)

Bundle Branch Block (BBB)Bundle Branch Block (BBB)

A bundle branch block refers to an obstruction in the transmission of the electrical impulse through

one branch (either right or left) of the bundle of His.

HemiblocksHemiblocks

A bundle branch block that occurs farther down the left bundle branch is called a hemiblock

Left Posterior Fascicular Block Left Anterior Fascicular Block

Bundle Branch Block (BBB)Bundle Branch Block (BBB)

In a bundle branch block, the impulse travels down the

unaffected bundle branch and then from one myocardial cell to the next to depolarize the

ventricle

Because this cell-to-cell conduction progresses much

more slowly than the conduction along the

specialized cells of the conduction system, ventricular

polarization is prolonged

Bundle Branch Block (BBB)Bundle Branch Block (BBB)

BBB: Analyzing a StripBBB: Analyzing a Strip

Rhythm: Regular

Rate: 60 – 100 bpm

P waves: Upright & uniform.

PRI: 0.12 – 0.20 sec

QRS: > 0.12 sec; notched or “bunny ears”.

***Interpretation: NSR w/ BBB & ST-segment depression

Premature Ventricular Premature Ventricular Contraction (PVC)Contraction (PVC)

A PVC is a premature, ectopic impulse that originates in either the right or left ventricle.

Electrical impulse originating from ventricle depolarizes only one ventricle at a time (resulting in sequential

depolarization).

This results in a wide, bizarre-looking QRS complex.

May be unifocal or multifocal.

PVC’sThe ST segment and T

wave slope in the opposite direction from

the main deflection of the QRS complex

If depolarization is abnormal, then

repolarization will be abnormal

Compensatory Pause

Occurs because the SA node isn’t depolarized by the ectopic ventricular beat, the discharge timing of the sinus

node remains unchanged and the underlying rhythm will resume on time

after the PVC

Unifocal PVC’s

Multifocal PVC’sMultifocal PVC’s

Patterned PVC’sBigeminy, Trigeminy, Quadrigeminy

Premature Ventricular Premature Ventricular Contraction (PVC)Contraction (PVC)

Causes:

Electrolyte ImbalancesHypokalemia, Hyperkalemia, Hypomagnesemia, Hypocalcemia

Metabolic Acidosis

Hypoxia

Myocardial Ischemia

Drug IntoxicationsCocaine, amphetamines, TCA’s

LV Enlargement

Increased Sympathetic Stimulation

Myocarditis

Premature Ventricular Premature Ventricular Contraction (PVC)Contraction (PVC)

Treatment:

If asymptomatic, no treatment may be required

Antiarrhythmics such as amiodarone (Cordarone), lidocaine, or procainamide

(Pronestyl), propafenone (Rythmol)

PVCs: Analyzing a Strip PVCs: Analyzing a Strip

Rhythm: Premature ectopic beat causes slight irregularity

Rate: Overall HR depends on rate of underlying rhythm

P waves: Ectopic beat is not preceded by a P wave.

PRI: None; impulse originates from a lower focus

QRS: Wide and bizarre; different from underlying QRS complexes. T wave is frequently in the opposite direction from

the QRS complex.

Run of PVC’sRun of PVC’s

3 or more consecutive PVC’s

Occurs within an underlying rhythm

Spontaneously resumes back to underlying

Symptomatic or Asymptomatic

Result of R-on-T Phenomenon

Amiodarone (Cordarone), lidocaine, or procainamide (Pronestyl)

Run of PVCs: Analyzing a Strip

Atrial Fibrillation (controlled) with a 5-beat run of PVCs (run of V-Tach or burst of PVCs) & ST-segment depression

Ventricular Escape BeatA ventricular beat that occurs as a result of a

pause in an underlying rhythm

Likely occur due to increased vagal effect on the SA node rather than because of

enhanced automaticity

A protective mechanism – preventing slow heart rates

Ventricular Escape Beat

How does this beat differ from a junctional escape beat???

Interpretation: NSR w/ ventricular escape beat following a pause converting back to NSR

Idioventricular (Escape) RhythmIdioventricular (Escape) Rhythm

Idioventricular (Escape) RhythmIdioventricular (Escape) Rhythm

Idioventricular rhythms occur when all pacemakers fail to function or when SV

impulses can’t reach the ventricles because of a block in the conduction

system

Idioventricular (Escape) RhythmIdioventricular (Escape) Rhythm

Causes:

Accompanied by Complete Heart Block

Myocardial Ischemia

MI

Digoxin Toxicity

Pacemaker Failure

Metabolic Imbalances

Idioventricular (Escape) RhythmIdioventricular (Escape) Rhythm

Treatment:

Pacemaker(Temporary – Permanent)

Treat Underlying Cause

IVR: Analyzing a StripIVR: Analyzing a Strip

Rhythm: Regular; can slow down as heart dies.

Rate: No atrial rate; ventricular rate 20 – 40 bpm

P waves: None; impulse originates from a lower focus

PRI: None; impulse originates from a lower focus

QRS: Wide and bizarre; equal to or > 0.12 sec. T wave not visible

Interpretation: Idioventricular Rhythm (IVR)

Accelerated Idioventricular Rhythm

Rate: 41 - 100

Wide, bizarre QRS complexes

No P waves

Accelerated Idioventricular Rhythm

How is AIVR distinguished from accelerated junctional rhythm???

Ventricular TachycardiasVentricular Tachycardias

Monomorphic, Polymorphic, Torsades de Pointes

Ventricular TachycardiaVentricular Tachycardia

Ventricular tachycardia usually results from increased myocardial irritability, which may be triggered

by enhanced automaticity or reentry within the Perkinje system or by

PVC’s initiating the R-on-T phenomenon

Ventricular TachycardiaVentricular TachycardiaCauses:

Myocardial ischemia

MI

CAD

Valvular heart disease

Heart failure

Cardiomyopathy

Electrolyte imbalances

Drug intoxication – digoxin, procainamide, quinidine, or cocaine

Ventricular Tachycardia

Non-sustained:

Paroxysmal bursts lasting less than 30 seconds

Sustained:

Stable, Unstable, or Pulseless

Ventricular TachycardiaVentricular Tachycardia

Three Types of ACLS Algorithms for V-Tach:

Stable Ventricular Tachycardia

Unstable Ventricular Tachycardia

Pulseless Ventricular Tachycardia

Monomorphic VT: Monomorphic VT: Analyzing a StripAnalyzing a Strip

Rhythm: Regular; sometimes slightly irregular

Rate: no atrial rate; ventricular rate 150 – 250 bpm

P waves: No P waves present

PRI: None

QRS: Wide and bizarre; Uniform; 0.12 sec.

T wave opposite direction of QRS

***Interpretation: Ventricular Tachycardia (VT)

Ventricular TachycardiaVentricular Tachycardia

A.K.A. – Monomorphic V-Tach

Polymorphic VT: Polymorphic VT: Analyzing a StripAnalyzing a Strip

Rhythm: Regular; sometimes slightly irregular

Rate: no atrial rate; ventricular rate 150 – 250 bpm

P waves: No P waves present

PRI: None

QRS: Wide and bizarre; Varied morphology; > 0.12 sec.

T wave opposite direction of QRS

***Interpretation: Polymorphic VT

Torsades de PointesTorsades de Pointes

Causes:

• Usually reversible

• Drugs that lengthen QT interval (amiodarone, ibultilide, erhythromycin, haloperidol, sotalol, levafloxicin)

• Myocardial ischemia

• Hypokalemia, hypomagnesemia, hypocalcemia

Torsades de PointesTorsades de Pointes

Treated by correcting the underlying cause:

Mechanical overdrive pacing

Magnesium sulfate

Electrical cardioversion

Torsades de Pointes: Torsades de Pointes: Analyzing a StripAnalyzing a Strip

Rhythm: Irregular; sometimes slightly irregular

Rate: no atrial rate; ventricular rate 150 – 250 bpm

P waves: No P waves present

PRI: None

QRS: Wide and bizarre; Varied morphology; > 0.12 sec.

T wave opposite direction of QRS

***Interpretation: Torsades de pointes

Ventricular Fibrillation (VF)Ventricular Fibrillation (VF)

A chaotic pattern of electrical activity in the ventricles in which electrical impulses arise from many different foci.

No effective myocardial contraction = No CO

Untreated V-fib causes most cases of sudden cardiac death in people outside of the hospital

Ventricular FibrillationVentricular FibrillationCauses:

Myocardial ischemia

MI

Untreated Ventricular Tachycardia

Underlying HD

Acid-Base Imbalance

Electric Shock

Severe Hypothermia

Electrolyte imbalancesHypokalemia, hyperkalemia, hypercalcemia

Ventricular Fibrillation

Fine or Coarse

VF: TreatmentVF: Treatment

Defibrillatory Shocks

CPR

Vasopressors

Antidysrhythmics

Determine Underlying Cause

DefibrillationDefibrillation

What Does Defibrillation Do?

The electrical current causes the myocardium to depolarize, which, in turn, encourages the SA node to resume normal control of the heart’s

electrical activity

RESETS THE ELECTRICAL CONDUCTION!

VF: Analyzing a StripVF: Analyzing a Strip

Rhythm: Chaotic

Rate: Cannot be determined; no discernible waves

P waves: No P waves

PRI: None

QRS: No discernible QRS complexes

***Interpretation: Ventricular Fibrillation (VF)

Ventricular Standstill SA node intact, so P waves are present

No ventricular conduction due to a preceding advanced AV block

AsystoleAsystole

NO ELECTRICAL ACTIVITY

NO MECHANICAL ACTIVITY

AsystoleAsystole

Treatment:

CPR

Epinephrine

Atropine

TIME TO WORKOUT!!!TIME TO WORKOUT!!!

ReferencesReferencesBeverage, D. Haworth, K., Labus, D. Mayer, B. H., & Munson, C.

(2005). ECG interpretation made incredibly easy, (3rd ed.). Ambler, PA: Lippincott, Williams, & Wilkins.

Chernecky, C., et al. (2002). Real world nursing survival guide: ECG’s & the heart. United States of America: W. B. Saunders Company.

Huff, J. (2006). ECG workout: Exercises in arrhythmia interpretation (5th ed.). United States of America: Lippincott, Williams & Wilkins.

Walraven, G. (1999). Basic arrhythmias (5th ed.). United States of America: Prentice-Hall, Inc.

www.madsci.com/manu/ekg_rhy.htm