Arrythmias Flashcards
Normal Electrical Conduction Pathway
SA Node –> AV Node–> Bundle of His –> Bundle Branches –> Purkinje fibers
Bpm for:
- SA Node
- AV Node
- His/ Purkinje fibers
- SA Node: 60-100 bpm
- AV Node: ~40-50 bpm
- His/ Purkinje fibers: <40 bpm
What method is used to assess heart’s electrical activity?
Electrocardiogram (ECG)
Electrocardiogram waves:
- Name of Waves?
- What does each wave represent?
- P-wave: atrial depolarization
- QRS Complex: ventricular depolarization
- T-wave: ventricular repolarization
- PR Segment: impulse conduction pause in the AV node
- QT interval: time from ventricular depolarization to repolarization (important for drug dosing!)
- Isoelectric point: No deflection from electrical activity (baseline)
Which ECG wave is most important for drug monitoring?
QT interval: time from ventricular depolarization to repolarization
Ventricular Cardiac Action Potential:
-Phases
-Electrolyte movement at each phase
~Sorry I can’t put in pictures friends, I’m pooro pooro~
Phase 4: Spontaneous pacemaker current- Gradual spontaneous conduction, mainly sodium ions
Phase 0: Rapid depolarization- Rapid inward sodium channel → rapid ventricular depolarization
Phase 1: Rapid repolarization- Outward K, Cl, transient outward current
Phase 2: Plateau phase- Inward sodium and calcium, outward potassium ions (balanced)
Phase 3: Rapid repolarization - Outward potassium → ventricular repolarization
Abnormal impulse formation vs Abnormal impulse conduction
Abnormal impulse formation
– SA or AV node is not working
– Impulse formation is coming from somewhere else = ectopic beat
Abnormal impulse conduction
– Blockade somewhere in the conduction system
– Reentry loop
Arrhythmias occur due to?
Scarring or fibrotic tissue (Caused by):
• Ischemic heart disease
• Cardiomyopathy
• Fibrotic diseases
Changes to the cardiac action potential:
• Electrolyte abnormalities
• Drugs
Other: • Genetic diseases
Types of Tachyarrhythmias (HR>100)
- Sinus Tachycardia
- Atrial Fibrillation
- Atrial flutter
- AV Node Reentrant Tachycardia
- AV Reentrant Tachycardia
- Ventricular Tachycardia
- Ventricular Fibrillation
Types of bradycardias (HR < 60bpm)
- Sinus Bradycardia
- First degree heart block
- Second degree heart block
- Third degree heart block
Sinus tachycardia:
a. Bpm
b. Causes
a. Bpm: > 100 bpm
b. Causes: increased firing of the SA node
• Non-pathologic: common during exercise or excitement
• Pathologic: – Often compensating for decreased stroke volume or blood pressure
– Due to autonomic disturbances
– If pathologic often leads to other tachycardic arrhythmias
Atrial Flutter
- Bpm
- ECG pattern
- Patho
BPM:
Atria =300 bpm
Ventricles: Any factor of 300 depending on the AV node (1:2 A flutter = 150 bpm, 1:3 A flutter = 100 bpm, 1:4 A flutter = 75 bpm)
ECG pattern: Sawtooth/ flutter waves
Patho:
Due to a predictable and rhythmic reentry loop in the R atrium
-Cavotricuspid isthmus: tissue in the lower R
atria between the inferior vena cava and the tricuspid valve that can conduct
-If this isthmus gets stimulated, it can recreate a reentry loop within the right atria
Notes: Very similar to Afib, often patients switch back and forth between Afib and atrial flutter
– Many of the same complications and symptoms as atrial fibrillation
AV NODE REENTRANT TACHYCARDIA (AVNRT)
-Patho
Reentry loop in the AV node due to an
ectopic atrial beat
- Normally, there is only one entry path into the AV node.
- In AVNRT, the patient has two entry paths – one slow (quickly repolarizing) and one fast (slowly repolarizing) entrance!
• Clinical manifestations: similar to other
tachycardias
ATRIAL VENTRICULAR REENTRANT TACHYCARDIA (AVRT)
-Patho
Reentry loop between the atria and ventricles
• Pathogenesis: reentry + ectopy in a heart with
an accessory pathway between the atria and ventricles
• Clinical manifestations: similar to other
tachycardias
VENTRICULAR TACHYCARDIA (VT)
- What is it
- Non sustained vs sustained VT
- Causes
- Clinical Manifestations
• Series of 3 or more premature ventricular beats
– Non-sustained VT: < 30 seconds, terminates spontaneously
– Sustained VT: > 30 seconds
Sustained VT may degenerate into ventricular fibrillation which can lead to sudden cardiac death!!
Intrinsic Causes • Structural disease – Ischemic heart disease – Cardiomyopathy – Surgical trauma
Extrinsic Causes • Electrolyte abnormalities – Hypokalemia – Hypomagnesemia • Medications – Antiarrhythmic medications
Clinical Manifestations • Patients can present with or without a pulse – With pulse patients may experience: o Palpitations o Dizziness, light-headedness o Hypotension, syncope
-Without a pulse bpm> with a pulse bpm
Ventricular Fibrillation
- What is it?
- Clinical Manifestation
- Disordered, rapid stimulation of the ventricles with no coordinated contractions
- Ventricular tachycardia degenerates into multiple smaller wavelets of reentry
– Clinical manifestation = NO CARDIAC OUTPUT → DEATH (Immediately life-threatening arrhythmia!!)
Sinus bradycardia
a. bpm
b. causes
c. clinical manifestations
a. Bpm: < 60 bpm
b. Due to: decreased firing of the SA node
- Non-pathologic: common during rest or sleep
- Pathologic:
Intrinsic Causes • Conduction disease :Decreased automaticity (aging) • Structural disease: – Ischemic heart disease – Cardiomyopathy – Surgical trauma
Extrinsic Causes
• Medications: Beta-blockers, calcium channel blockers
• Metabolic disease: Hypothyroidism
• Autonomic syndromes
• Electrolyte abnormalities: Hyper/hypokalemia, Hypermagnesemia
c. Clinical Manifestations: • Often asymptomatic • Fatigue, weakness • Dizziness, light-headedness, syncope • Exercise intolerance
Heart Block
- Degrees
- What does each degree represent?
- Causes
- Clinical Manifestation of each degree
Three degrees of Heart Block
(higher degree = more severe)
First-degree: conduction delay in the AV node
Second-degree: conduction delay in AV node or bundle of His
– Type 1: less severe
– Type II: more severe
Third-degree (“complete heart block”): complete dissociation between the atria and ventricles
Second-degree type II and third degree heart block
are medical emergencies and require immediate
intervention!!
-Causes: same as sinus bradycardia
Pathologic:
Intrinsic Causes
• Conduction disease :Decreased automaticity (aging)
• Structural disease:
– Ischemic heart disease
– Cardiomyopathy
– Surgical trauma
Extrinsic Causes
• Medications: Beta-blockers, calcium channel blockers
• Metabolic disease: Hypothyroidism
• Autonomic syndromes
• Electrolyte abnormalities: Hyper/hypokalemia, Hypermagnesemia
Clinical Manifestations:
1. First-degree: usually asymptomatic
2. Second-degree: usually symptomatic only at low heart rates
3. Third-degree (“complete heart block”):
– Fatigue, weakness
– Dizziness, light-headedness, syncope
– Exercise intolerance
Which arrhythmia is the most common?
Atrial Fibrilation
Atrial Fibrillation:
Types
Paroxysmal: Terminates within 7 days of onset
Persistent: Lasts > 7 days
Longstanding, persistent: Lasts > 12 months
Permanent: patient and clinician have decided that
there will be no more effort to restore
or maintain sinus rhythm
AFIB w/ rapid ventricular rate: Generally acute presentation – Higher HRs (more conduction through AV node) • Often needs immediate intervention – May lead to syncope
ATRIAL FIBRILLATION (AFIB): CLINICAL MANIFESTATIONS
Fatigue Palpitations Shortness of breath Hypotension Dizziness, light-headedness Syncope
Many patients are asymptomatic and may not know
they have Afib!
- Stroke or systemic embolism: 5-fold increase in risk
- Heart failure: 3-fold increase in risk
- Dementia: 2-fold increase in risk
- Hospitalization: 2-fold increase in risk
- Mortality: 2-fold increase in risk
Atrial Fibrillation:
- Electrical activity
- Patho
- BPM: Atria & Ventricles
Disorganized and irregular atrial electrical activity
– “Quivering”
– No distinguishable atrial depolarization/contraction (p-waves)
• Occurs when atrial tissue is modified due to abnormalities in structure or function
• Rate:
– Atrial: 600-800 bpm
– Ventricular: usually 100-180 bpm
Atrial Fibrillation:
- Patho
- Risk Factors
• Triggered by rapidly firing ectopic beats in the atria
– Most common: where pulmonary veins connect to the atria
• Ectopic beats can occur due to previously discussed etiologies of arrhythmias
• Risk factors: – Concomitant cardiac disease – Diabetes mellitus – Obesity – Obstructive sleep apnea – Hyperthyroidism – Smoking
