cardiac electrophysiology presentation part two

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Cardiac Electrophysiology Rhythm Interpretation: PART TWO Kathleen Brownrigg, BSc, RN, MSN Pediatric Nurse Educator May 2011

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Page 1: Cardiac electrophysiology  presentation part two

Cardiac ElectrophysiologyRhythm Interpretation: PART TWO

Kathleen Brownrigg, BSc, RN, MSNPediatric Nurse Educator

May 2011

Page 2: Cardiac electrophysiology  presentation part two

Sino-atrial Node Arrhythmias

• Arrhythmias that originate in the SA Node are the following

• Sinus bradycardia• Sinus tachycardia• Sinus arrhythmia• Sinus arrest

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Sinus BradycardiaCharacteristics:•Can be in normal health individuals, such as athletes•Can be found in people with heart disease, such as MI•HR < 60 bpm•Regular rhythm•PR intervals 0.12 – 0.20 sec and are constant•QRS < 0.12 sec•May be caused by: B-blockers, anesthesia, hypothermia

Treatment•If HR very low and S & S of low CO or HF•Meds: Atropine, Isuprel•Pacemaker (temporary, permanent)

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Sinus TachycardiaCharacteristics•Can be present in healthy individuals, for example with exercise, anxiety, fever, hyperthyroidism, pain and stress.•May be early sign of CHF.•HR between 100-160 bpm in adults, age dependent in pediatric patients.•PR intervals 0.12 – 0.20 sec and constant.•QRS < 0.12 sec•Regular rhythm

Treatment

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Sinus arrhythmiaCharacteristics•Variations in sinus rhythm.•Found in children and associated with respiration; HR speeds up with inspiration and slows with expiration.•Rate 60 – 100 bpm•PR interval 0.12 – 0.20 sec and constant•QRS < 0.12 sec

Treatment•Digoxin

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Sinus ArrestCharacteristics•Failure of SA node momentarily so that no impulse is initiated•May be related to vagal stimulation, carotid sinus massage, deep inspiration as in Valsalva’s maneuver.•No atrial activity since no stimulus for atria to contract.•May occur with large doses of Digoxin or Quinidine•Usually, person has no symptoms, BUT with decreased CO, fainting, dizziness or syncope may occur.

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Atrial Arrhytmias

• Atrial arrhythmias originate from the atria when an ectopic focus in the atria assumes reponsibility for pacing the heart, either by irritability or escape.

• Four types of atrial arrhythmias are:– Premature atrial contractions– Atrial tachycardia– Atrial flutter– Atrial fibrillation

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Premature Atrial ContractionCharacteristics•Single beats originating in the atria and coming early in the cardiac cycle.•Rhythm is irregular d/t ectopic beats (ectopic means originating outside the SA node).•P wave of PAC different from other P waves•PR Interval 0.12 – 0.20 sec; could also be > 0.20 sec.•QRS < 0.12 sec.•Person may complain of heart “skiping”beats.•Can be caused by digitalis intake, vagus nerve stimulation, heart disease (i.e., rheumatic heart carditis).

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Atrial Tachycardia (SVT)Characteristics•Occurs in healthy individuals.•In cardiac patients, may be precursor to more serious atrial arrhythmias.•Rapid, regular heartbeat, which begins suddenly, and was likely preceded by frequent PACs.•Can be short-runs or last for hours.•Can be due to the toxic effects of digitalization.•Can lead to CHF with prolonged periods.•Rhythm is regular•Rate 150 – 250 bpm•P waves different from sinus P waves•PR Interval 0.12 – 0.20 sec•QRS < 0.12 sec

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Atrial FlutterCharacteristics•Impulse from single or multiple ectopic foci in atria.•Occurs in presence of organic heart disease.•Many impulses fail to pass though AV node to the ventricles b/c of chaotic atrial activity.•Digoxin and Inderal usually effective in treating.•Some cases may beed cardioversion or atrial pacin•Rhythm can be regular or irregular.•Atrial rate is 250 – 350 bpm•P waves have saw-toothed appearance •Unable to determine PR Interval•QRS < 0.12 sec

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Atrial FibrillationCharacteristics•Impulse originates in one or more irritable atrial ectopic areas.•Ventricular rhythm highly irregular.•Atrial rate constantly changing due to the fibrillation wave•Atrial rate > 350 bpm •P waves not distinguishable, therefore PR Interval unmeasurable.•QRS < 0.12 sec•May have unknown etiology•Can be treated with Digoxin, Quinidine, Inderal•Elective cardioversion or temparary pacemaker for low ventricular rates due to possible block.ar

Page 12: Cardiac electrophysiology  presentation part two

Junctional Arrhythmias

• Rhythms that originate from the AV node.• They replace the activity of the SA node when he latter

fails, therefore are the heart’s secondary pacemaker.• P waves may be inverted because the atria are

depolarized via retrograde conduction. P waves can be closer, lost in or follow the QRS complex, and the PR Intervals are < 0.12 sec in the P wave precedes the QRS complex.

• Junctional arrythmias can occur in cases of organic heart disease, atrial ischemia, myocardial infarction, or exessive digitalization.

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Junctional Escape Rhythm

Characteristics•Ventricular rate 40-60 bpm•QRS duration < 0.12 sec•May lead to heart failure and decreased cardiac output.

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Junctional TachycardiaCharacteristics•Rate 100 – 180 bpm•Occurs when the AV junction becomes irritable, speeds up and overrides higher pacemaker sites.•Rhythm is regular

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Premature Junctional ContractionCharacteristics•Can be caused by excess digitalization or Quinidine, or organic heart disease.•PR Interval < 0.12 sec•Also called premature nodal contraction.

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Ventricular Arrythmias

• Ventricular arrythmias are the most serious arrythmias because the heart is less effective than usual, and because the heart is functioning on its last level of backup support. Usually they occur suddenly and are often rapidly fatal despite vigorous treatment.

• Occasionally they can be benign. • Types of ventricular arrythmias are:

– Premature ventricular contractions (PVCs)– Ventricular tachycardia– Ventricular fibrillation– Idioventricular rhythm– Asystole/ventricular standstill

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Premature Ventricular ContractionUnifocal PVC

Unifocal PVC, Bigeminy

Multifocal PVCs

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Premature Ventricular ContractionsCharacteristics• Originate in an ectopic focus of the ventricular myocardium.• Have wide bizarre-shaped QRS complex with no preceding P wave, and T wave is in

opposite direction• QRS can be in opposite direction of person’s normal QRS complexes.• Can occur in healthy people but are more common when the heart is disease or injured.• Can arise from a single focus (unifocal) or several foci (multifocal) in the ventricles.• Can occur alone, in pairs (couplets), or in runs of three or more.• Multifocal PVCs are often signs of difitalis toxicity or severe myocardial diseases.

Treatment• Lidocaine to quiet an irritable myocardium• Procainamide and Quinidine can also be given• PVCs are often associated with poor cardiac output, therefore, temporary pacemakers

may be required with severe bradycardia.

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Premature Ventricular Contractions

Unifocal PVCs Multifocal PVCs

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Ventricular TachycardiaCharacteristics•Looks like an uninteruupted series of PVCs•Rhythm usually regular, but could be irregular•Rate 150 – 250 bpm•Often preceded by a PVC that occurs in the vulnerable period of he ventricular repolarization cycle.

Treatment•Must be initiated since person unable tolerate high ventricular rates for long (decreased cardiac output).•Lidocaine, procainamide or Quinidine for short runs of V tach.•Cardioversion needed for sustained runs of V tach.

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Ventricular FibrillationCharacteristics•Appears on monitored as an uncoordinated tracing with no discernible waves or complexes.•Indication of extreme myocardial irritability with many ventricular foci initiating impulses in a chaotic fashion.•Patient may appear dead, complete loss of sensorium and possible tremors and seizures.

Treatment•Defibrillation•If defibrillation not effective after a few shocks, START CPR!

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Idioventricular Rhythm

Characteristics•HR 20 – 40 bpm and usually regular•Because rate so slow, cardiac output very low.•As with other ventricular arrhythmias, QRS complex wide and bizarre

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Torsade de PointesCharceteristics:• Type of ventricular tachycardia• Characterized by a gradual twisting of the direction of the QRS complexes around

the isoelectric line.• Associated with R on T phenomenon and a unique mechanism of initiation with a

long-short cycle length.• D Precipitating factors:

– Class I antiarrythmic agents – Electrolyte imbalances– Altered ventricular refractoriness related to prolonged QT intervals, brady-arrythmias or

ischemia.• Treatment

– Correct underlying abnormality or stop Class I antiarrythmics

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AsystoleCharacteristics•Signifies ventricular standstill, meaning there is no electrical conduction throughout the heart. Therefore, no contraction occurs.•Can be caused by various problems, cardiac and non-cardiac, i.e., impaired respiratory function, drug overdose, hemorrhage, anaphalactic reactions, …

Treatment•EMERGENCY•Initiate CPR

Page 25: Cardiac electrophysiology  presentation part two

Atrio-ventricular Blocks

• AV blocks are conduction delays or blocks through the AV node.

• Three categories:1. First Degree AV Blocks2. Second Degree AV Blocks

Mobitz Type I (Wenckebach)Mobitz Type II (Classical)

3. Third Degree AV Block- Complete heart block

Page 26: Cardiac electrophysiology  presentation part two

First Degree AV BlockCharacteristics•Most common conduction disturbance•Can appear in healthy individuals and those with diseasaed hearts.•In many elderly patients, chronic degeneration of the conduction system causes this arrythmia.•Can be caused by Quinidine and Procainamide.•Impulse carried normally from SA node through atria but are delayed when reach AV node.•PR Interval > 0.20 sec and usually constant across the strip.

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Second Degree AV Block: Mobitz Type I (Wenckebach)

Characteristics•Characterized by occasional dropped ventricular beats, meaning the impulse conducted through the atria, but was blocked at the AV node.•Irregular rhythm; R-R interval gets progressively shorter as PR interval gets longer unitl one P wave is not conducted.•Occurs with digitalis toxicity or with inferior wall MI•Can be caused by acute rheumatic fever, electrolyte imbalance, vagal stimulation, Quinidine or Procainamide therapy.•Generally, does not affect CO since V rate remains almost normal

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Second Degree AV Blocks: Mobitz Type II (Classical 2:1 AV Block)

Characetristics•There are 2, 3, or 4 P waves for every QRS complex because AV node blocks out many of the impulses.•Rhythm can be regular or irregular.•Rate is usually bradycardic.•PR Interval is regular and ALWAYS constant.

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Third Degree AV BlockCharacteristics•Total block at the AV node, resulting in AV dissociation, meaning that the atria and ventricles are totally dissociated from each other.•Venricles can be controlled by either junctional or ventricular escape rhythm.•Atrial rate faster than ventricle.•Can be due to digitalis toxicity; acute rheumatic fever, acute MI or diffuse fibrosis throughout the conduction system. Can be congenital also.•May also occur after open-heart surgery, especially in patients with septal defects.•With slow ventricular rates may cause low CO.•Rhythm is regular•No relationship between P waves and QRS complexes.

Page 30: Cardiac electrophysiology  presentation part two

Bundle Branch BlocksCharacterstics•Caused by a block of depolarization in the right or left Bundle Branch.•A block to either of the bundle branches creates a delay of the electrical impulse to that side, so that the ventricles are not deolarized at the same time,•Individual depolarization of both ventricles are still of normal duration, but because both ventricles do not fire simultaneously, a widened QRS is seen on the ECG since the two are out of sync.

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Bundle Branch BlockCharacteristics•QRSs are superimposed on each other; as seen in diagram •Occasionally, occur in healthy individuals, but more commonly in people with coronary artery disease or hypertension.

Treatment•Usually directed toward the associated heart disease rather than the block.