This document discusses various cardiac rhythms including bradyarrhythmias and tachyarrhythmias. It describes sinus bradycardia and sick sinus syndrome as common causes of bradyarrhythmias. Various degrees of atrioventricular block are also discussed. For tachyarrhythmias, it distinguishes supraventricular rhythms originating above the ventricles from ventricular rhythms. Common supraventricular rhythms include atrial flutter and atrial fibrillation. Treatment options depend on whether rhythms cause symptoms and include medications, pacing devices, or catheter ablation.

1. Rhythms of the HeartRhythms of the Heart

2. RatesRates
 BradyarrhythmiasBradyarrhythmias
 Sinus BradycardiaSinus Bradycardia
 Sick Sinus SyndromeSick Sinus Syndrome
 AV Nodal BlockadeAV Nodal Blockade
 First DegreeFirst Degree
 Second DegreeSecond Degree
 Mobitz IMobitz I
 Mobitz IIMobitz II
 Third DegreeThird Degree
 Complete Heart BlockComplete Heart Block

3. RatesRates
 TachyarrhythmiasTachyarrhythmias
 SupraventricularSupraventricular
 Originate from foci above or within the atrioventricularOriginate from foci above or within the atrioventricular
nodenode
 Main players in outpatient settingMain players in outpatient setting
 All the favoritesAll the favorites
 AV nodal reentrant tachycardia (SVT)AV nodal reentrant tachycardia (SVT)
 Atrial flutterAtrial flutter
 Atrial fibrillationAtrial fibrillation

4. LocationLocation
 Supraventricular ArrhythmiasSupraventricular Arrhythmias
 Originate from foci above or within the atrioventricularOriginate from foci above or within the atrioventricular
nodenode
 Ventricular ArrhythmiasVentricular Arrhythmias
 Non-sustained ventricular tachycardiaNon-sustained ventricular tachycardia
 Sustained ventricular tachycardiaSustained ventricular tachycardia
 StableStable
 Know the neighborhoodKnow the neighborhood
 Do no harmDo no harm
 UnstableUnstable
 Ventricular fibrillationVentricular fibrillation

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6. BradyarrhythmiasBradyarrhythmias
 Sinus BradycardiaSinus Bradycardia
 Sinus rhythm with a resting heart rate of 60Sinus rhythm with a resting heart rate of 60
beats/minute or lessbeats/minute or less
 Few patients actually become symptomatic untilFew patients actually become symptomatic until
their heart rate drops to less than 50 beats/minutetheir heart rate drops to less than 50 beats/minute
 Pathophysiology of sinus bradycardia is dependentPathophysiology of sinus bradycardia is dependent
upon the underlying causeupon the underlying cause
 Commonly, sinus bradycardia is an incidentalCommonly, sinus bradycardia is an incidental
finding in otherwise healthy individuals,finding in otherwise healthy individuals,
particularly in young adults or sleeping patientsparticularly in young adults or sleeping patients

7. BradyarrhythmiasBradyarrhythmias
 Sinus BradycardiaSinus Bradycardia
 Other causes of sinus bradycardia are related toOther causes of sinus bradycardia are related to
increased vagal tone.increased vagal tone.
 Physiologic causes of increased vagal tone include thePhysiologic causes of increased vagal tone include the
bradycardia seen in athletes.bradycardia seen in athletes.
 Pathologic causes include, but are not limited to,Pathologic causes include, but are not limited to,
inferior wall myocardial infarction, toxic orinferior wall myocardial infarction, toxic or
environmental exposure, electrolyte disorders, infection,environmental exposure, electrolyte disorders, infection,
sleep apnea, drug effects, hypoglycemia,sleep apnea, drug effects, hypoglycemia,
hypothyroidism, and increased intracranial pressure.hypothyroidism, and increased intracranial pressure.

8. BradyarrhythmiasBradyarrhythmias
 Physical:Physical:
 Cardiac auscultation and palpation of peripheral pulsesCardiac auscultation and palpation of peripheral pulses
reveal a slow, regular heart rate.reveal a slow, regular heart rate.
 The physical examination is generally nonspecific,The physical examination is generally nonspecific,
although it may reveal the following signs:although it may reveal the following signs:
 Decreased level of consciousnessDecreased level of consciousness
 CyanosisCyanosis
 Peripheral edemaPeripheral edema
 Pulmonary vascular congestionPulmonary vascular congestion
 DyspneaDyspnea
 Poor perfusionPoor perfusion
 SyncopeSyncope

9. BradyarrhythmiasBradyarrhythmias
 Causes:Causes:
 One of the most common pathologic causes ofOne of the most common pathologic causes of
symptomatic sinus bradycardia is thesymptomatic sinus bradycardia is the sick sinussick sinus
syndromesyndrome..
 The most common medications responsible includeThe most common medications responsible include
therapeutic and supratherapeutic doses of digitalistherapeutic and supratherapeutic doses of digitalis
glycosides, beta-blockers, and calcium channel-glycosides, beta-blockers, and calcium channel-
blocking agents.blocking agents.
 Other cardiac drugs less commonly implicatedOther cardiac drugs less commonly implicated
include class I antiarrhythmic agents andinclude class I antiarrhythmic agents and
amiodarone.amiodarone.

10. BradyarrhythmiasBradyarrhythmias
 Causes:Causes:
 One of the most common pathologic causes ofOne of the most common pathologic causes of
symptomatic sinus bradycardia is thesymptomatic sinus bradycardia is the sick sinussick sinus
syndromesyndrome..
 The most common medications responsible includeThe most common medications responsible include
therapeutic and supratherapeutic doses of digitalistherapeutic and supratherapeutic doses of digitalis
glycosides, beta-blockers, and calcium channel-glycosides, beta-blockers, and calcium channel-
blocking agents.blocking agents.
 Other cardiac drugs less commonly implicatedOther cardiac drugs less commonly implicated
include class I antiarrhythmic agents andinclude class I antiarrhythmic agents and
amiodarone.amiodarone.

11. BradyarrhythmiasBradyarrhythmias
 TreatmentTreatment
 AsymptomaticAsymptomatic
 No treatment requiredNo treatment required
 SymptomaticSymptomatic
 Treatment aimed at restoring normal sinus rateTreatment aimed at restoring normal sinus rate
 Specific to etiology of bradycardiaSpecific to etiology of bradycardia
 If patient is on rate controlling medications-stop them.If patient is on rate controlling medications-stop them.
 If patient is hypokalemic-replace it.If patient is hypokalemic-replace it.
 If the patient is hypothyroid-replace it (you get the idea)If the patient is hypothyroid-replace it (you get the idea)
 Permanent pacemaker if the patient has continuedPermanent pacemaker if the patient has continued
symptoms with no improvement from intervention orsymptoms with no improvement from intervention or
with no identifiable cause.with no identifiable cause.

12. BradyarrhythmiasBradyarrhythmias
 Sick Sinus SyndromeSick Sinus Syndrome
 Sinus bradycardia may also be caused by the sickSinus bradycardia may also be caused by the sick
sinus syndrome.sinus syndrome.
 Involves a dysfunction in the ability of the sinusInvolves a dysfunction in the ability of the sinus
node to generate or transmit an action potential to thenode to generate or transmit an action potential to the
atria.atria.
 Includes a variety of disorders and pathologicIncludes a variety of disorders and pathologic
processes that are grouped within one looselyprocesses that are grouped within one loosely
defined clinical syndrome.defined clinical syndrome.
 includes signs and symptoms related to cerebralincludes signs and symptoms related to cerebral
hypoperfusion, in association with sinus bradycardia,hypoperfusion, in association with sinus bradycardia,
sinus arrest, sinoatrial (SA) block, carotidsinus arrest, sinoatrial (SA) block, carotid
hypersensitivity, or alternating episodes of bradycardiahypersensitivity, or alternating episodes of bradycardia
and tachycardia.and tachycardia.

13. BradyarrhythmiasBradyarrhythmias
 Sick sinus syndromeSick sinus syndrome
 Most commonly occurs in elderly patients withMost commonly occurs in elderly patients with
concomitant cardiovascular disease and follows anconcomitant cardiovascular disease and follows an
unpredictable course.unpredictable course.
 The majority of cases remain idiopathic.The majority of cases remain idiopathic.

14. BradyarrhythmiasBradyarrhythmias
 Sick Sinus SyndromeSick Sinus Syndrome
 Clinical presentationClinical presentation
 Same as symptomatic bradycardiaSame as symptomatic bradycardia
 TreatmentTreatment
 Same as symptomatic sinus bradycardiaSame as symptomatic sinus bradycardia
 Usually requires permanent pacemakerUsually requires permanent pacemaker

15. AV BlockAV Block
 What are the rhythms?What are the rhythms?

16. AV BlockAV Block
 What is the rhythm?What is the rhythm?

17. AV BlockAV Block
 What is the rhythm?What is the rhythm?

18. AV BlockAV Block
 Atrioventricular BlockAtrioventricular Block
 Not truly part of the bradyarrhythmias, but usuallyNot truly part of the bradyarrhythmias, but usually
slow.slow.
 Varying degreesVarying degrees
 Think of them as burns…the higher the degree, theThink of them as burns…the higher the degree, the
worse they are.worse they are.

19. AV BlockAV Block
 First-degree heart block, or first-degreeFirst-degree heart block, or first-degree
atrioventricular (AV) blockatrioventricular (AV) block
 Definition:Definition:
 Prolongation of the PR interval on the ECG to more than 200Prolongation of the PR interval on the ECG to more than 200
msec.msec.
 TreatmentTreatment
 If underlying condition suspected (drug overdose, acute MI,If underlying condition suspected (drug overdose, acute MI,
myocarditis, etc) treat that condition.myocarditis, etc) treat that condition.
 No treatment indicated if asymptomatic.No treatment indicated if asymptomatic.

20. AV BlockAV Block
 Second-degree heart block, or second-degreeSecond-degree heart block, or second-degree
atrioventricular (AV) blockatrioventricular (AV) block
 Refers to a disorder of the cardiac conduction system in whichRefers to a disorder of the cardiac conduction system in which
some atrial impulses are not conducted to the ventricles.some atrial impulses are not conducted to the ventricles.
 Electrocardiographically, some P waves are not followed by aElectrocardiographically, some P waves are not followed by a
QRS complexQRS complex
 composed of 2 types: Mobitz I or Wenckebach block, and Mobitz II.composed of 2 types: Mobitz I or Wenckebach block, and Mobitz II.
 Mobitz I second-degree AV blockMobitz I second-degree AV block
 Characterized by a progressive prolongation of the PR interval,Characterized by a progressive prolongation of the PR interval,
which results in a progressive shortening of the R-R interval.which results in a progressive shortening of the R-R interval.
Ultimately, the atrial impulse fails to conduct, a QRS complex isUltimately, the atrial impulse fails to conduct, a QRS complex is
not generated, and there is no ventricular contraction.not generated, and there is no ventricular contraction.
 Mobitz II second-degree AV blockMobitz II second-degree AV block
 Characterized by an unexpected nonconducted atrial impulse.Characterized by an unexpected nonconducted atrial impulse.
Thus, the PR and R-R intervals between conducted beats areThus, the PR and R-R intervals between conducted beats are
constant.constant.

21. AV BlockAV Block
 Because an acute myocardial infarction is one causeBecause an acute myocardial infarction is one cause
of complete heart block, patients who concurrentlyof complete heart block, patients who concurrently
experience an MI can have associated symptomsexperience an MI can have associated symptoms
from the MI, including chest pain, dyspnea, nauseafrom the MI, including chest pain, dyspnea, nausea
or vomiting, and diaphoresis.or vomiting, and diaphoresis.
 Patients who have a history of cardiac disease mayPatients who have a history of cardiac disease may
be on medications that affect the conduction systembe on medications that affect the conduction system
through the AV node, including the following:through the AV node, including the following:
 Beta-blockersBeta-blockers
 Calcium channel blockersCalcium channel blockers
 Digitalis cardioglycosidesDigitalis cardioglycosides

22. AV BlockAV Block
 TreatmentTreatment
 For all symptomatic high degree heart blockFor all symptomatic high degree heart block
 Identification of etiology based on clinical presentationIdentification of etiology based on clinical presentation
 Transcutaneous pacing for unstable patientsTranscutaneous pacing for unstable patients
 Permanent pacemaker when indicatedPermanent pacemaker when indicated

23. TachyarrhythmiasTachyarrhythmias
Ectopic rate nomenclature:
[150-250] Paroxysmal tachycardia
[250-350] Flutter
[350+] Fibrillation

24. TachyarrhythmiasTachyarrhythmias
 ECG or ambulatory monitoringECG or ambulatory monitoring
 Evaluation usually reveals a supraventricular origin of QRS complexes atEvaluation usually reveals a supraventricular origin of QRS complexes at
rates of 150-250 bpm and a regular rhythm.rates of 150-250 bpm and a regular rhythm.
 The QRS complex usually narrows unless a conduction abnormality isThe QRS complex usually narrows unless a conduction abnormality is
present or is functionally induced from the rapid heart rate.present or is functionally induced from the rapid heart rate.
 P waves are not usually seen because they are buried within the QRSP waves are not usually seen because they are buried within the QRS
complex. A pseudo R prime may be seen in V1, or pseudo S waves may becomplex. A pseudo R prime may be seen in V1, or pseudo S waves may be
seen in leads II, III, or aVF. The onset is abrupt with an atrial prematureseen in leads II, III, or aVF. The onset is abrupt with an atrial premature
complex, which conducts with a prolonged PR interval.complex, which conducts with a prolonged PR interval.
 The PR interval may shorten over the first few beats at onset, or it mayThe PR interval may shorten over the first few beats at onset, or it may
lengthen during last few beats preceding termination of the tachycardia.lengthen during last few beats preceding termination of the tachycardia.
 Abrupt termination occurs with a retrograde P wave, sometimes followedAbrupt termination occurs with a retrograde P wave, sometimes followed
by a brief period of asystole or bradycardia.by a brief period of asystole or bradycardia.

25. TachyarrhythmiasTachyarrhythmias
 Preventive therapyPreventive therapy
 Needed for frequent, prolonged, or highly symptomaticNeeded for frequent, prolonged, or highly symptomatic
episodes that do not terminate spontaneously or those thatepisodes that do not terminate spontaneously or those that
cannot be easily terminated by the patient.cannot be easily terminated by the patient.
 DrugsDrugs
 Include long-acting beta-blockers, calcium channel blockers, andInclude long-acting beta-blockers, calcium channel blockers, and
digitalis.digitalis.
 Radiofrequency catheter ablationRadiofrequency catheter ablation
 Should be considered in patients with frequent symptomaticShould be considered in patients with frequent symptomatic
episodes who do not want drug therapy, who cannot tolerate theepisodes who do not want drug therapy, who cannot tolerate the
drugs, or in whom drug therapy fails.drugs, or in whom drug therapy fails.

26. TachyarrhythmiasTachyarrhythmias
 Treatment:Treatment:
 Hemodynamically StableHemodynamically Stable
 Slowing the ventricular response with verapamil orSlowing the ventricular response with verapamil or
diltiazem may be the appropriate initial treatment.diltiazem may be the appropriate initial treatment.
 Adenosine produces transient AV block and can be usedAdenosine produces transient AV block and can be used
to reveal flutter waves.to reveal flutter waves.
 These drugs generally do not convert atrial flutter toThese drugs generally do not convert atrial flutter to
NSR(normal sinus rhythm).NSR(normal sinus rhythm).

27. TachyarrhythmiasTachyarrhythmias
 TreatmentTreatment
 If the flutter cannot be cardioverted, terminated byIf the flutter cannot be cardioverted, terminated by
pacing, or slowed by the drugs mentioned above,pacing, or slowed by the drugs mentioned above,
digoxin can be administered alone or with either adigoxin can be administered alone or with either a
calcium antagonist or beta-blocker.calcium antagonist or beta-blocker.

28. TachyarrhythmiasTachyarrhythmias
 TreatmentTreatment
 Rate control is the goal of medication in atrial flutter or AF.Rate control is the goal of medication in atrial flutter or AF.
 Beta-adrenergic blockers are especially effective in the presence ofBeta-adrenergic blockers are especially effective in the presence of
thyrotoxicosis and increased sympathetic tone.thyrotoxicosis and increased sympathetic tone.
 Antiarrhythmic drugs alone control atrial flutter in only 50-60% ofAntiarrhythmic drugs alone control atrial flutter in only 50-60% of
patients.patients.
 Radiofrequency catheter ablation has been used to interrupt the re-Radiofrequency catheter ablation has been used to interrupt the re-
entrant circuit in the right atrium and prevent recurrences of atrialentrant circuit in the right atrium and prevent recurrences of atrial
flutter.flutter.
 Radiofrequency ablation is immediately successful in more than 90% ofRadiofrequency ablation is immediately successful in more than 90% of
cases and avoids the long-term toxicity observed with antiarrhythmic drugs.cases and avoids the long-term toxicity observed with antiarrhythmic drugs.
 When considering drug therapy for atrial flutter/fibrillation,When considering drug therapy for atrial flutter/fibrillation,
remember the treatment caveat "electrical cardioversion is theremember the treatment caveat "electrical cardioversion is the
preferred modality in the patient whose condition is unstable."preferred modality in the patient whose condition is unstable."

29. TachyarrhythmiasTachyarrhythmias
 What is the rhythm?What is the rhythm?

30. Atrial FibrillationAtrial Fibrillation
 Most commonly encountered arrhythmia inMost commonly encountered arrhythmia in
clinical practice.clinical practice.
 Defined by the absence of coordinated atrialDefined by the absence of coordinated atrial
systole.systole.
 Results from multiple reResults from multiple re--entrant electricalentrant electrical
wavelets that move randomly around the atria.wavelets that move randomly around the atria.
 P waves are replaced by irregular, chaoticP waves are replaced by irregular, chaotic
fibrillatory waves, often with a concomitantfibrillatory waves, often with a concomitant
irregular ventricular response.irregular ventricular response.

31. Atrial FibrillationAtrial Fibrillation

32. Atrial FibrillationAtrial Fibrillation
 When ventricular rate increases to tachycardicWhen ventricular rate increases to tachycardic
levels, a situation of atrial fibrillation withlevels, a situation of atrial fibrillation with
rapid ventricular response (AF with RVR)rapid ventricular response (AF with RVR)
ensues.ensues.
 The incidence of atrial fibrillation increasesThe incidence of atrial fibrillation increases
significantly with advancing age.significantly with advancing age.
 AF may increase mortality up to 2-fold,AF may increase mortality up to 2-fold,
primarily due to embolic stroke.primarily due to embolic stroke.

33. Atrial FibrillationAtrial Fibrillation
 Causes of atrial fibrillation can be divided intoCauses of atrial fibrillation can be divided into
cardiovascular versus noncardiovascular causes.cardiovascular versus noncardiovascular causes.
 Important cardiovascular causes include the following:Important cardiovascular causes include the following:
 Long-standing hypertensionLong-standing hypertension
 Ischemic heart diseaseIschemic heart disease
 CHFCHF
 Any form of carditisAny form of carditis
 CardiomyopathyCardiomyopathy
 Infiltrative heart disease of any typeInfiltrative heart disease of any type
 Sick sinus syndromeSick sinus syndrome

34. Atrial FibrillationAtrial Fibrillation
 Causes of atrial fibrillation can be divided intoCauses of atrial fibrillation can be divided into
cardiovascular versus noncardiovascular causes.cardiovascular versus noncardiovascular causes.
 Noncardiovascular causes of atrial fibrillation include theNoncardiovascular causes of atrial fibrillation include the
following:following:
 HyperthyroidismHyperthyroidism
 Low levels of potassium, magnesium, or calciumLow levels of potassium, magnesium, or calcium
 PheochromocytomaPheochromocytoma
 Sympathomimetic drugs, alcohol, electrocutionSympathomimetic drugs, alcohol, electrocution
 Noncardiovascular respiratory causes include the following:Noncardiovascular respiratory causes include the following:
 Pulmonary embolismPulmonary embolism
 PneumoniaPneumonia
 Lung cancerLung cancer
 HypothermiaHypothermia

35. Atrial FibrillationAtrial Fibrillation
 ECG:ECG:
 Absent P waves, replaced by irregular, chaotic fibrillatory FAbsent P waves, replaced by irregular, chaotic fibrillatory F
waves, in the setting of irregular QRS complexes .waves, in the setting of irregular QRS complexes .

36. Atrial FibrillationAtrial Fibrillation
 2010 ACC/AHA/ACP recommendations:2010 ACC/AHA/ACP recommendations:
 Recommendation 1: Rate control with chronicRecommendation 1: Rate control with chronic
anticoagulation is the recommended strategy for the majorityanticoagulation is the recommended strategy for the majority
of patients with atrial fibrillation.of patients with atrial fibrillation.
 Recommendation 2: Patients with atrial fibrillation shouldRecommendation 2: Patients with atrial fibrillation should
receive chronic anticoagulation with adjusted-dose warfarin,receive chronic anticoagulation with adjusted-dose warfarin,
unless they are at low risk of stroke or have a specificunless they are at low risk of stroke or have a specific
contraindication (eg, thrombocytopenia, recent trauma orcontraindication (eg, thrombocytopenia, recent trauma or
surgery, alcoholism)surgery, alcoholism)
 Recommendation 3: the following drugs are recommendedRecommendation 3: the following drugs are recommended
for their demonstrated efficacy in rate control during exercisefor their demonstrated efficacy in rate control during exercise
and while at rest: atenolol, metoprolol, diltiazem, andand while at rest: atenolol, metoprolol, diltiazem, and
verapamilverapamil..
 Digoxin is only effective for rate control at rest and therefore shouldDigoxin is only effective for rate control at rest and therefore should
only be used as a second-line agent for rate control in atrialonly be used as a second-line agent for rate control in atrial
fibrillation.fibrillation.

37. Atrial FibrillationAtrial Fibrillation
 2010 ACC/AHA/ACP recommendations:2010 ACC/AHA/ACP recommendations:
 Recommendation 4: For patients who elect to undergo acuteRecommendation 4: For patients who elect to undergo acute
cardioversion to achieve sinus rhythm in atrial fibrillation.cardioversion to achieve sinus rhythm in atrial fibrillation.
 Recommendation 5: Both transesophageal echocardiographyRecommendation 5: Both transesophageal echocardiography
with short-term prior anticoagulation followed by early acutewith short-term prior anticoagulation followed by early acute
cardioversion.cardioversion.
 Recommendation 6: Most patients converted to sinus rhythmRecommendation 6: Most patients converted to sinus rhythm
from atrial fibrillation should not be placed on rhythmfrom atrial fibrillation should not be placed on rhythm
maintenance therapy since the risks outweigh the benefits.maintenance therapy since the risks outweigh the benefits.