I. Sinus rhythms and arrhythmias
A. Records the impulse originating from the sinus node and follows the path to the atria, AV junction, and through the bundle of His, to the bundle branches and on to the Purkinje fibers
B. Sinus node is the main pacemaker
C. Sinus rhythms include
1. Normal sinus rhythm
2. Sinus tachycardia
3. Sinus bradycardia
4. Sinus arrhythmia
5. Sinus arrest
6. Sinus exit block
II. Normal sinus rhythm
A. Is the standard against which all other rhythms are compared
B. Criteria:
1. Rhythm: regular
2. Heart rate: 60 - 100
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Sinus Rhythm
C. Clinical Presentation – no problems typically associated with rhythm
D. Treatment – no treatment generally associated with this rhythm
III. Sinus Tachycardia
A. Characterized by heart rate greater than 100
B. Causes: fever, any type of hypovolemia such as dehydration or blood loss
C. Criteria:
1. Rhythm: regular
2. Heart rate: 100 - 150
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Sinus Tachycardia
D. Clinical Presentation – dependent on the rate and patient tolerance of the rate
E. Treatment – directed at the underlying cause
IV. Sinus Bradycardia
A. Characterized by heart rate less than 60
B. Criteria:
1. Rhythm: regular
2. Heart rate: 40 -60
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Sinus Bradycardia
C. Clinical Presentation – dependent on the rate and patient tolerance of the rate
D. Treatment
1. Treated only if accompanied by symptoms of hypoperfusion, such as dizziness, chest pain, changes in LOC
2. Medical treatment may include atropine or pacemaker
V. Sinus Arrhythmia
A. Characterized by slightly irregular rhythm
B. Cause:
1. Usually caused by respiratory cycle
2. Inspiration causes slight increase in rate and exhalation causes a slight decrease in rate due to vagal tone during the different phases of respiration
3. Seen most often in children and young adults
C. Criteria:
1. Rhythm: irregular
2. Heart rate: normal, 60 - 100 or slow, 40 - 60
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Sinus Arrhythmia
D. Clinical Presentation – no problems associated with rhythm
E. Treatment – no treatment needed
VI. Sinus Arrest
A. Characterized by an irregular pause in the regular rhythm
B. Cause:
1. Failure of the SA node to discharge an impulse
2. Upsets the timing of the sinus node discharge, and the underlying rhythm will not resume on time following the pause
C. Criteria:
1. Rhythm: irregular – the underlying rhythm does not resume on time following the pause
2. Heart rate: can be normal, 60 - 100 or slow, 40 - 60
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Underlying rhythm with Sinus Arrest
D. Clinical Presentation
1. If pauses are short, there may be no symptoms
2. If pauses are long or frequent, patient may not tolerate and have symptoms of hypotension, dizziness, syncope
E. Treatment – Treated only if accompanied by symptoms of hypoperfusion, treat as symptomatic bradycardia
VII. Sinus Exit Block
A. Characterized by a regular pause in a regular rhythm
B. Cause:
1. An electrical impulse is generated by the SA node, but is blocked as it exits the sinus node
2. Because the regularity of the sinus node discharge is not interrupted (just blocked), the underlying rhythm will resume on time following the pause
3. The length of the pause will be a multiple of the underlying R-R interval
C. Criteria:
1. Rhythm: irregular – the underlying rhythm resumes on time following the pause, with the length of the pause being a multiple of the underlying R-R interval
2. Heart rate: can be normal, 60 - 100 or slow, 40 - 60
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, all have same size, shape and deflection
5. PR interval: 0.12 - 0.20
6. Interpretation: Underlying rhythm with Sinus Exit Block
D. Clinical Presentation
1. If pauses are short, there may be no symptoms
2. If pauses are long or frequent, patient may not tolerate and have symptoms of hypotension, dizziness, syncope
E. Treatment – Treated only if accompanied by symptoms of hypoperfusion, treat as symptomatic bradycardia
VIII. Atrial rhythms
A. Result from ectopic stimuli– that is, they arise from outside the SA node in either the left atrium or right atrium
B. P waves will have different configuration that sinus P waves
C. These rhythms, especially if very rapid, can affect ventricular filling time and diminish the strength of atrial kick that normally provides 30% of cardiac output
D. Atrial rhythms include
1. Wandering atrial pacemaker
2. Premature atrial contractions
3. Nonconducted premature atrial contractions
4. Atrial tachycardia
5. Paroxysmal atrial tachycardia
6. Supraventricular tachycardia
7. Atrial flutter
8. Atrial fibrillation
IX. Wandering Atrial Pacemaker
A. The pacemaker shifts from the SA node to ectopic atrial sites
B. Characterized by varying size, shape and direction of the P waves
C. Cause:
1. May be normal in very young, very old, or athletes
2. Mostly from an inhibitory vagal response
3. May be associated with Digitalis administration
D. Criteria:
1. Rhythm: usually irregular, but may be regular
2. Rate: usually 60 - 100, but may be slower
3. QRS: less than 0.10
4. P wave: only one precedes each QRS, but vary is size, shape, and deflection
5. PR interval: varies from 0.12 - 0.20
6. Interpretation: Wandering Atrial Pacemaker
E. Clinical Presentation – not usually significant
F. Treatment – Treated only if accompanied by symptoms of hypoperfusion, treat as symptomatic bradycardia
X. Premature Atrial Contraction
A. The impulse is from the atria, outside the SA node
B. Characterized by beats occurring earlier than the next expected beat in the underlying rhythm
C. Causes:
1. Alcohol, cigarettes, caffeine, anxiety, fever, fatigue
2. Also associated with coronary or valvular heart disease, respiratory failure, hypoxia, electrolyte imbalance, Digoxin toxicity, catecholamine release during pain or anxiety
3. When associated with heart disease, may lead to atrial fibrillation or atrial flutter
D. Criteria:
1. Rhythm: underlying rhythm regular, irregular with PAC
2. Heart rate: that of underlying rhythm
3. QRS: less than 0.10
4. P wave: abnormal in size, shape, deflection, or may be hidden in the preceding T wave distorting the T wave contour
5. PR interval: normal but may be shortened
6. Interpretation: Underlying rhythm with Premature Atrial Contraction
E. Clinical presentation – dependent on underlying cause
F. Treatment
1. No treatment if asymptomatic
2. Treatment is directed toward the underlying cause
3. Cause may be unrecognized
XI. Nonconducted PAC
A. Occurs when an ectopic atrial focus occurs so early that the AV node is refractory and the impulse cannot be conducted to the ventricles
B. Occurs earlier than expected in relation to the underlying rhythm
C. Characterized by an ectopic P wave, but not accompanied by a QRS, but rather a pause
D. Easy to confuse with as Sinus Arrest or Sinus Exit Block – examine T waves to differentiate the rhythms
E. Criteria:
1. Rhythm: underlying rhythm regular, irregular with nonconducted PAC
2. Heart rate: that of underlying rhythm
3. QRS: absent
4. P wave: abnormal in size, shape, deflection, or may be hidden in the preceding T wave distorting the T wave contour
5. PR interval: absent
6. Interpretation: Underlying rhythm with Nonconducted PAC
XII. Atrial Tachycardia
A. Occurs from an ectopic atrial pacemaker or rapid reentry in the atria and AV node
B. Results in decreased cardiac output due to loss of atrial kick and shortened diastole
C. Characterized by a rapid heart rate with P waves difficult to distinguish
D. Causes
1. Digoxin toxicity, most common cause
2. Also, Rheumatic heart disease, hyperthyroidism, Cor pulmonale
E. Criteria:
1. Rhythm: usually regular
2. Heart rate: 150 - 250
3. QRS: usually normal, less than 0.10
4. P wave: may not always be discernible due to fast rate, frequently obscured in the preceding T wave
5. PR interval: not measurable
6. Interpretation: Atrial Tachycardia
F. Clinical presentation
1. Depends on toleration of the rhythm
2. May have sign and symptoms of decreased cardiac output, such as hypotension, blurred vision, etc
G. Treatment
1. Vagal maneuvers – Valsalva, carotid massage
2. Adenosine to chemically cardiovert
3. Cardioversion
4. Also, Cardizem, Verapamil, Digoxin, Rapid atrial pacing –Caution, Cardioversion + Digoxin + Ca channel blocker can cause sustained systole
XIII. Paroxysmal Atrial Tachycardia
A. Characterized by an abrupt start and end of Atrial tachycardia
B. Is often initiated by a PAC
C. 3 or more consecutive PACs are considered to be atrial tachycardia
D. Criteria:
1. Rhythm: usually regular
2. Heart rate: 150 - 250
3. QRS: usually normal, less than 0.10
4. P wave: may not always be discernible due to fast rate, frequently obscured in the preceding T wave
5. PR interval: not measurable
6. Interpretation: Paroxysmal Atrial Tachycardia
XIV. Supraventricular Tachycardia
A. Characterized by narrow complex tachycardia with P waves hidden in the previous T wave, it is not possible to tell where the rhythm originates
B. Is a general term that refers to the origin as being above the ventricles
C. Includes rapid response atrial flutter, atrial tachycardia, junctional tachycardia
D. Criteria:
1. Rhythm: regular
2. Heart rate: >150 beats/min
3. QRS: normal, less than 0.10
4. P wave: difficult or unable to visualize
5. PR interval: not measurable
6. Interpretation: Supraventricular Tachycardia
XV. Atrial Flutter
A. Occurs when an ectopic pacemaker site in the atria discharges impulses at a very rapid rate
B. The atrial muscles respond to the rapid stimulation producing wave deflections called flutter waves
C. Characterized by flutter waves
D. Cause:
1. Mitral valve disease, hyperthyroidism, pericardial disease, MI, COPD
2. Rarely seen in healthy people, usually have some underlying heart disease
E. Criteria:
1. Rhythm: atrial– regular, ventricular– regular if conduction is regular
2. Heart rate: atrial– 250 - 400, ventricular– varies depending on conduction but will be less than atrial rate
3. QRS: less than 0.10
4. P waves: sawtooth looking, more P waves than QRS
5. PR interval: not measurable
6. Interpretation: Atrial Flutter
F. Clinical presentation: if not tolerated, may have decreased cardiac output, hypotension, blurred vision, symptoms depend on ventricular response
G. Treatment: if associated with rapid ventricular response needs immediate attention. Treatment of choice is synchronized cardioversion, also may give Digoxin, Quinidine, Corvert
XVI. Atrial Fibrillation
A. Multiple ectopic pacemakers in the atria discharge at a very rapid rate
B. The impulses are so rapid it causes the atria to quiver instead of contracting regularly
C. If left untreated may cause thrombus formation due to blood pooling in the atria from inadequate contractions
D. Characterized by irregular rhythm, absence of P waves, and presence of fibrillation waves
E. Cause:
1. Valvular heart disease, hyperthyroidism, infection, CAD, MI, hypoxia, pericarditis, Aminophylline, Digoxin
2. Commonly associated with CHF
F. Criteria:
1. Rhythm: atrial and ventricular irregular
2. Heart rate: atrial– 350 - 600 (400 average), ventricular– 160 - 180 or depending on conduction
3. QRS: less than 0.10
4. P waves: absent, irregular fibrillation waves seen instead
5. PR interval: not measurable
6. Interpretation: Atrial Fibrillation
a) If ventricular rate is >100, called uncontrolled A-fib
b) If ventricular rate is < 100, called controlled A-fib
G. Clinical presentation: if not tolerated will show signs of decreased cardiac output
H. Treatment:
1. Try to keep ventricular rate under 100
2. Drugs: Cardizem, Verapamil, Digoxin, Corvert, Quinidine, Pronestyl, beta blockers
3. Chemical or electrical cardioversion
a) Electrical cardioversion most successful if used within the 1st 3 days
b) If unsure how long patient has had the rhythm, check for thrombus formation before cardioversion, because conversion to NSR may dislodge clots if not anticoagulated
c) Patient is at risk for CVA while in A-fib due to release of micro-emboli
XVII. Junctional rhythms
A. Originate from the area around the AV node
B. If the SA node fails to function, the AV junction contains specialized pacemaker cells and can serve as a secondary pacemaker site
C. The inherent firing rate of the junctional pacemaker cells is 40 - 60 beats per minute
D. Enhance automaticity may accelerate the rate beyond the inherent firing rate
XVIII. AV junction as a pacemaker
A. The electrical impulse leaves the AV junction and can be conducted
1. Retrograde – backward to depolarize the atria
2. Forward – to depolarize the ventricles
B. Location of the P wave relative to the QRS depends on the speed of conduction
1. P wave in front of the QRS – if the electrical impulse from the junction depolarizes the atria first, then the ventricles
a) May produce negative P waves before the QRS
b) PR interval will be short (0.10 seconds or less)
c) Ventricles will depolarize normally, resulting in a narrow QRS
2. P wave after the QRS – if the electrical impulse from the junction depolarizes the ventricles first, then the atria
3. P wave hidden in the QRS – if the electrical impulse from the junction depolarizes both the atria and the ventricles simultaneously
C. Rhythms from the AV junction
1. Premature junctional contraction
2. Junctional escape beats
3. Junctional rhythm
4. Accelerated junctional rhythm
5. Junctional tachycardia
XIX. Premature Junctional Contraction (PJC)
A. Is an early beat that originates in an ectopic pacemaker site in the AV junction
B. Characterized by narrow complex early beat with abnormal P wave
C. Criteria:
1. Rhythm: underlying rhythm is regular, irregular with extra beat
2. Rate: is that of the underlying rhythm
3. QRS: normal (<0.10 sec)
4. P wave: depends on speed of conduction
a) Negative P waves before the QRS
b) P wave after the QRS
c) P wave hidden in the QRS
5. PR interval: if present, short
6. Interpretation: Underlying rhythm with Premature Junctional Contraction
XX. Junctional Escape Beats
A. Occasionally an ectopic junctional beat will occur late instead of early
1. Are more likely to occur due to increased vagal effect on the SA node rather than to enhanced automaticity
2. Are common following a pause in the underlying rhythm
3. Morphologic characteristics are the same as the PJC
B. Characterized by narrow complex late beat with abnormal P wave
C. Criteria:
1. Rhythm: underlying rhythm is regular; irregular with escape beat
2. Rate: is that of the underlying rhythm
3. QRS: width is normal (<0.10 sec)
4. P wave: depends on speed of conduction
a) Negative P waves before the QRS
b) P wave after the QRS
c) P wave hidden in the QRS
5. PR interval: If present, short
6. Interpretation: Underlying rhythm with Junctional Escape
XXI. Junctional Rhythm
A. Characterized by narrow complexes and absent or abnormal P waves
B. Criteria:
1. Rhythm: regular
2. Rate: 40 - 60 beats per minute
3. QRS: width is normal (<0.10 sec)
4. P wave: depends on speed of conduction
a) Negative P waves before the QRS
b) P wave after the QRS
c) P wave hidden in the QRS
5. PR interval: if present, short
6. Interpretation: Junctional rhythm
XXII. Accelerated Junctional Rhythm
A. Characterized by greater than inherent rate, narrow complexes, and absent or abnormal P waves
B. Criteria:
1. Rhythm: regular
2. Rate: 60 - 100 beats per minute
3. QRS: width is normal (<0.10 sec)
4. P wave: depends on speed of conduction
a) Negative P waves before the QRS
b) P wave after the QRS
c) P wave hidden in the QRS
5. PR interval: if present, short
6. Interpretation: Accelerated Junctional Rhythm
XXIII. Junctional Tachycardia
A. Mechanism responsible could be increased automatcity of the junctional tissue, or conduction of the ectopic impulse though a reentry circuit
B. Characterized by rapid rate, narrow complexes, and absent or abnormal P waves
C. Criteria:
1. Rhythm: regular
2. Rate: >100 beats per minute
3. QRS: width is normal (<0.10 sec)
4. P wave: depends on speed of conduction
a) Negative P waves before the QRS
b) P wave after the QRS
c) P wave hidden in the QRS
5. PR interval: if present, short
6. Interpretation: Junctional Tachycardia
XXIV. Heart Blocks
A. Result from interruption in the conduction system of the atria and the ventricles
B. A block can be total or partial, or simply a delayed conduction
C. Blocks can occur at the AV node, the bundle of His, or at the bundle branches
D. Clinical presentation:
1. depends on how may impulses are completely blocked, and how slow the ventricular rate is
2. The symptomatic patient can present with decreased cardiac output, causing light-headedness, hypotension, and confusion
E. Heart block rhythms
1. First degree AV block
2. Second degree AV block, type I ( Mobitz I, Wenckebach)
3. Second degree AV block, type II (Mobitz II)
4. Third degree AV block (complete heart block)
5. AV dissociation
6. Bundle branch blocks
XXV. First Degree AV Block
A. Is simply a delay in conduction, may appear in a healthy person
B. Is the least severe of all blocks
C. Looks like NSR
D. Characterized by longer than normal PR interval
E. Criteria:
1. Rhythm: regular
2. Heart rate: normal, 60 - 100
3. QRS: normal, less than 0.10
4. P waves: normal configuration, one for every QRS
5. PR interval: > .20 seconds and is consistent with every beat
6. Interpretation: First Degree AV Block
F. Clinical presentation: usually asymptomatic
G. Treatment:
1. Monitor patient, watch for progression to a higher degree of block
2. Review use of Digoxin, calcium channel blockers, and beta blockers
XXVI. Second Degree AV Block, type I ( Mobitz I, Wenckebach)
A. Each successive impulse from the SA node is delayed slightly longer than the previous impulse until one impulse fails to be conducted through the ventricles
B. Is almost always temporary until underlying cause can be fixed
C. Characterized by irregular rhythm and progressively lengthening PR interval along with dropped complexes
D. Cause: MI usually inferior wall, Digoxin toxicity, acute myocarditis, calcium channel blockers, beta-blockers, and cardiac surgery
E. Criteria:
1. Rhythm: irregular (regularly irregular), P wave will be regular
2. Heart rate: usually normal, depends on the P to QRS ratio
3. QRS: normal, less than 0.10
4. P waves: normal configuration, more P waves than QRS complexes
5. PR interval: progressively longer until a P wave is not conducted and the QRS complex dropped, then the cycle repeats
6. Interpretation: Second Degree AV Block, type I ( Mobitz I, Wenckebach)
F. Clinical presentation:
1. Usually asymptomatic with good prognosis
2. May have signs of decreased cardiac output
G. Treatment:
1. None if asymptomatic
2. Atropine if slow ventricular rate
3. Possible temporary pacemaker until rhythm resolves
XXVII. Second Degree AV Block, type II (Mobitz II)
A. More serious because the block is in the lower conduction system
B. Ventricular rate tends to be slower and cardiac output diminished
C. Has the potential to deteriorate rapidly to Third Degree AV block or ventricular standstill with little or no warning
D. Conduction ratio can be regular or can vary causing 2:1, 3:1, 4:1, etc. blocks
E. Characterized by a variation in the P to QRS ratio
F. Cause: Permanent: changes associated with aging, congenital abnormalities, MI usually anterioseptal, cardiomyopathy, cardiac surgery, and ablation
G. Criteria:
1. Rhythm: atria regular, ventricles regular unless the conduction rate varies
2. Heart rate: atrial rate usually 60 - 100, ventricular rate slower depending on the number of impulses conducted
3. QRS:
a) Normal, <0.10, if blocked at the bundle of His
b) Wide, > 0.10, if blocked at the bundle branches
4. P waves: normal contour, more P waves than QRSs
5. PR interval: may be normal or prolonged, but remains constant
6. Interpretation: Second Degree AV Block, type II (Mobitz II)
H. Clinical presentation:
1. Asymptomatic if only a few beats dropped
2. As the number of dropped beats increase, patient may experience palpitations, fatigue, dyspnea, chest pain, lightheadedness
I. Treatment:
1. Observation if asymptomatic
2. Isoproterenol (Isuprel) instead of Atropine because conduction problem is in the bundle of His and the purkinje system, therefore, drugs that work directly on the myocardium work better than those that increase atrial rate
3. Commonly requires placement of a pacemaker
XXVIII. Third Degree AV Block (Complete Heart Block)
A. The impulses from the atria are completely blocked at the AV node and cannot be conducted through the ventricles
B. The atria and ventricles beat independently of each other
C. The atria will be paced by the SA node, while the ventricles are paced by an escape pacemaker near the AV or in the ventricles
D. Characterized by lack of cooperation between the P waves and the QRS complexes
E. Causes: acute inferior or anterior MI, drug toxicity (Digoxin, beta-blockers, calcium channel blockers), excessive vagal tone, myocarditis, endocarditis, following cardiac surgery, congenital abnormality
F. Criteria:
1. Rhythm: Atrial– regular (P waves march out, but some may be hidden in T wave or QRS complexes), Ventricular– regular
2. Heart rate: Atrial– usually that of the sinus node, 60 - 100
a) Ventricle– 40 - 60 if paced by the AV junction
b) Ventricle– 20 - 40 if paced by the ventricles
3. QRS:
a) Normal if blocked at the AV node or bundle of His
b) Wide if blocked at the bundle branches
4. P waves: normal configuration, more P waves than QRSs
5. PR interval: varies greatly – no relationship between Ps and QRSs
6. Interpretation: Third Degree AV Block (Complete Heart Block)
G. Clinical presentation: most patients experience significant symptoms of decreased cardiac output, can be life threatening
H. Treatment: Atropine or Isoproterenol, temporary pacemaker until problem resolves or until permanent pacemaker can be placed
XXIX. Complete AV dissociation
A. Atria and ventricles beat independently of each other, each controlled by its own pacemaker
B. Characterized by atrial and ventricular rates about the same, with the ventricular rate slightly faster, but Ps and QRSs are independent
C. Is never the primary problem, results from an underlying disturbance
D. Criteria:
1. Rhythm: Atrial and Ventricular rates nearly equal, regular
2. Heart rate: at least 60 - 100, atria and ventricles are within 10 beats of each other
3. QRS: Normal or Wide depending on where the escape pacemaker is
4. P wave: are always present, but may move in and out of the QRS, are not related to the QRS complexes
5. PR interval: changes as the rhythm dissociates
6. Interpretation: Complete AV dissociation
E. Clinical presentation: usually present signs of decreased cardiac output
F. Treatment:
1. Aimed at treating the underlying problem
2. May need antiarrhythmics, pacemaker, review for cardiac drug toxicity
XXX. Bundle Branch Block
A. An obstruction in the transmission of impulses through one of the branches, either the left or the right, of the bundle of His
B. The block causes the ventricle on that side to be depolarized later than the ventricle on the intact side
C. Characterized by an abnormal QRS complex, wide (0.12 or greater) and bizarre looking
D. The presence of a bundle branch block can be recognized by a single lead monitoring system, but differentiating between left and right bundle branch blocks requires a 12 lead ECG
E. Causes: acute MI, many types of heart diseases
F. Criteria:
1. Rhythm: is that of the underlying rhythm
2. Heart rate: is that of the underlying rhythm
3. QRS: wide, greater than 0.12 seconds
4. P waves: usually normal depending on underlying rhythm
5. PR interval: normal depending on underlying rhythm
6. Interpretation: underlying rhythm with accompanying bundle branch block
G. Treatment:
1. A bundle branch block itself is not significant, and requires no treatment
2. However, a temporary transvenous pacemaker is indicated under the following conditions
a) A new right or left bundle branch block develops as a result of acute MI
b) A bundle branch block complicated by a 1st, 2nd , or 3rd degree AV block or by a fascicular block, especially when associated with an acute MI ( a fascicle is a bundle of Purkinje fibers – any main division of the ventricular conduction system is a fascicle. There are three fascicles in the ventricular conduction system, the Right Bundle Branch, the Anterior Division of the Left Bundle Branch, and the Posterior Division of the Left Bundle Branch.)
XXXI. Ventricular rhythms
A. Originate in the ventricles, below the bundle of His
B. Most are associated with a wide QRS complex
C. Ventricular arrhythmias include:
1. Premature ventricular contraction (PVC)
2. Ventricular escape beats
3. Fusion beats
4. Ventricular tachycardia
5. Torsade de pointes
6. Ventricular fibrillation
7. Idioventricular rhythm (Ventricular escape rhythm)
8. Accelerated idioventricular rhythm
9. Ventricular standstill (Ventricular asystole)
XXXII. Premature Ventricular Contraction
A. A premature ectopic impulse originating in the ventricles
B. Usually caused by increased automaticity and electrical irritability in the ventricular conduction system or muscle tissue
C. Are significant for two reasons:
1. Can lead to more serious arrhythmias
2. Decrease cardiac output
D. Characterized by an early, abnormal QRS complex
E. Often followed by a compensatory pause (the measurement between the R wave preceding the PVC to the R wave following the PVC is equal to 2 R-R intervals of the underlying rhythm)
F. The underlying rhythm resumes on time following the PVC because the SA node is not depolarized by the ectopic beat
G. PVCs occur in addition to the underlying rhythm, and appear in various combinations
1. Single beat
2. Every other beat – bigeminal pattern
3. Every third beat – trigeminal pattern
4. Every fourth beat – quadrigeminal pattern
5. In pairs – couplets
6. In runs – three or more beats together is also termed ventricular tachycardia
7. Uniform – unifocal, PVCs that are identical in size, shape and direction due to the fact that they arise from the same focus
8. Multiform – multifocal, PVCs that differ in shape, size, and direction due to differing focus sites
9. ``R on T" phenomenon – when a PVC has occurred during the vulnerable period of ventricular repolarization (on or near the peak of the T wave) Stimulation of the ventricle at this time may precipitate repetitive ventricular contractions, resulting in V-tach or V-fib
H. Occur in healthy hearts as well as those with heart disease
I. Cause:
1. Anxiety, excessive caffeine or alcohol
2. Certain cardiac drugs
3. Hypoxia, acidosis, electrolyte imbalance
4. Congestive heart failure, MI, and other heart diseases
5. Reperfusion following thrombolytic therapy or angioplasty
6. Heart surgery or contact of endocardium with catheters
J. Criteria:
1. Rhythm: underlying rhythm usually regular, irregular with PVC
2. Heart rate: that of the underlying rhythm
3. QRS: wide and bizarre, greater than 0.12 seconds, and differ from the QRS complexes of the underlying rhythm
4. P wave: none with the PVC, P waves may be present in the underlying rhythm
5. PR interval: none to measure with the PVC
6. Interpretation: underlying rhythm with PVC
K. Clinical presentation: depends on the frequency of the beats
L. Treatment:
1. Could require no treatment
2. May be aimed at treating the underlying cause
3. If frequent or poorly tolerated, IV lidocaine or procainamide my be used
4. In nonacute setting, oral antiarrhythmics may be given
XXXIII. Ventricular Escape Beat
A. Characterized by ventricular beats that occur late instead of early in an underlying rhythm
B. More likely to be caused by increased vagal effect on the SA node, rather than increased automaticity
C. Commonly occur following a pause in the underlying rhythm
D. Criteria:
1. Rhythm: underlying rhythm usually regular, irregular with the escape beat
2. Heart rate: that of the underlying rhythm
3. QRS: wide and bizarre, greater than 0.12 seconds, and differ from the QRS complexes of the underlying rhythm
4. P wave: none with the escape beat, P waves may be present in the underlying rhythm
5. PR interval: none to measure with the escape beat
6. Interpretation: underlying rhythm with Ventricular Escape Beat
XXXIV. Fusion Beats
A. Occur when two opposing electrical currents meet and collide within the same chamber at the same time
B. A PVC occurs at about the same time that a regular beat occurs, depolarizing the ventricles simultaneously in two different directions
C. Characterized by complexes that have characteristics of both the PVC and the QRS complex of the underlying rhythm
D. The complex is usually narrower and of lesser amplitude than a PVC alone
E. The P to P, and R to R interval will remain constant
F. Cannot be recognized clinically, only electrically
G. There is no clinical significance to fusion beats alone, except to identify the presence of a ventricular focus
H. Criteria:
1. Rhythm: regular
2. Heart rate: that of the underlying rhythm
3. QRS: wide, usually greater than 0.12
4. P wave: will be the same as those of the underlying rhythm
5. PR interval: may be somewhat shorter than that of the underlying rhythm
6. Interpretation: underlying rhythm with Fusion beat
XXXV. Ventricular Tachycardia
A. Originates in an ectopic focus in the ventricles
B. Usually associated with increased automaticity or reentry
C. May develop without warning, but is often associate with frequent PVCs
D. Characterized by rapid heart rate made up of ventricular beats
E. May occur as a
1. Sustained rhythm– lasting longer than 30 seconds
2. Nonsustained rhythm– lasting less than 30 seconds
3. Burst of VT– a series of 3 or more consecutive PVCs
F. Cause:
1. Usually occurs with underlying heart disease
2. Commonly occurs with myocardial ischemia or infarction
3. Certain medications may prolong the QT interval predisposing the patient to ventricular tachycardia
4. Other causes include electrolyte imbalance and mechanical stimulation of the endocardium
G. Criteria:
1. Rhythm: usually regular, may be somewhat irregular
2. Heart rate: 150 - 250
3. QRS: wide and bizarre, greater than 0.12 seconds
4. P wave: none associated, the SA node does continue to fire independently, so P waves may be seen at random, but are usually hidden in the QRS complexes
5. PR interval: not measurable
6. Interpretation: Ventricular Tachycardia
H. Clinical presentation: depends on the duration and the patients ability to tolerate the rhythm
I. Treatment: Check the patient
1. If there is no pulse, begin CPR and other code measures
2. If there is a pulse and the patient is unstable - cardiovert and begin drug therapy
3. With chronic or recurrent VT
a) Give antiarrhythmics
b) Long term may need ICD placed
c) Ablation may be used for reentry
XXXVI. Torsade de Pointes
A. A unique variant form of ventricular tachycardia
B. Characterized by QRS complexes that seem to twist around the baseline, changing back and forth from negative to positive
C. Is commonly an immediate forerunner to ventricular fibrillation
D. Cause:
1. Is associated with prolonged QT interval
2. Is often caused by drugs conventionally recommended in treating VT
3. Phenothiazine or tricyclic antidepressant overdose
4. Electrolyte disturbances, especially hypokalemia and hypomagnesemia
E. Criteria:
1. Rhythm: somewhat irregular
2. Heart rate: 150 - 250
3. QRS: wide and bizarre, greater than 0.12 seconds, polarity changes from positive to negative around the isoelectric line
4. P wave: none associated
5. PR interval: not measurable
6. Interpretation: Torsade de Pointe
F. Treatment protocol includes:
1. Begin CPR and other code measures
2. Eliminate predisposing factors - rhythm has tendency to recur unless precipitating factors are eliminated
3. Administrate magnesium sulfate bolus
4. Overdrive pace, especially if precipitated by bradycardia
5. Defibrillation
XXXVII. Ventricular Fibrillation
A. A disorganized, chaotic electrical focus in the ventricles which takes control of the heart
B. The ventricles do not beat in any coordinated fashion, instead quiver asynchronously and ineffectively
C. Characterized by an erratic series of waves
D. Is the most common cause of sudden cardiac death
E. May occur spontaneously, but is most often preceded by VT or dangerous forms of PVCs (pairs, runs, multifocal, or R-on-T type)
F. There is no cardiac output, peripheral pulses, or blood pressure and the patient become unconscious immediately
G. Death is imminent
H. Two types of V-fib
1. Coarse - waves are large, usually indicates a more recent onset and is more likely to be reversed by defibrillation
2. Fine - waves are small, must be differentiated from asystole
I. Criteria:
1. Rhythm: chaotic
2. Heart rate: none
3. QRS: no complexes are present
4. P waves: none
5. PR interval: none
6. Interpretation: Ventricular Fibrillation
J. Treatment: Begin CPR and other code measures
XXXVIII. Idioventricular Rhythm
A. An arrhythmia originating in a escape pacemaker site in the ventricles
B. Occurs:
1. When the rate of impulse formation from the higher pacemakers becomes less than the escape pacemaker in the ventricles
2. When the impulses from the higher pacemakers are blocked and cannot reach the ventricles
C. Characterized by a slow ventricular rhythm
D. May be transient (as with vagal effect) or continuous (as seen with advanced heart disease)
E. Is usually a terminal event occurring just before ventricular standstill
F. Criteria:
1. Rhythm: usually regular
2. Heart rate: 20 - 40 beats per minute, sometimes slower
3. QRS: wide, greater than 0.12 seconds
4. P wave: none
5. PR interval: none
6. Interpretation: Idioventricular Rhythm
G. Clinical presentation - is generally symptomatic, with hypotension and decreased cardiac output
H. Treatment
1. Atropine
2. Pacing
3. Dopamine when hypotensive
XXXIX. Accelerated Idioventricular Rhythm
A. Accelerated denotes a rhythm that exceeds the inherent ventricular escape rate of 20 - 40 , but not fast enough to be ventricular tachycardia
B. An arrhythmia originating in a escape pacemaker site in the ventricles
C. Usually a transient arrhythmia that is well tolerated and produces no hemodynamic effects
D. Brief episodes of AIVR may alternate with periods of normal sinus rhythm
E. Characterized by a ventricular rhythm greater than the inherent ventricular rate, but less than 150
F. Cause:
1. Is common following acute MI, and is frequently a reperfusion rhythm
2. Is also seen with cardiomyopathy
G. Criteria:
1. Rhythm: usually regular
2. Heart rate: 50 - 100
3. QRS: wide, greater than 0.12 seconds
4. P wave: none
5. PR interval: none
6. Interpretation: Accelerated Idioventricular Rhythm
H. Treatment: not usually required
XL. Ventricular Standstill (Ventricular Asystole)
A. Is the absence of all electrical activity in the ventricles
B. Characterized by ECG tracings that show
1. P waves with no QRS complexes – is usually preceded by some type of advanced AV block
2. Straight line – is usually the terminal rhythm following VT, V-fib, or idioventricular rhythm
C. Prognosis is usually extremely poor despite resuscitative efforts
D. Criteria:
1. Rhythm: none
2. Heart rate: none
3. QRS: none
4. P wave: may be present or have none
5. PR interval: none
6. Interpretation: Ventricular Standstill (Ventricular Asystole)
E. Treatment: Begin CPR and other code measures
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