Clinical Electrophysiology IV Flashcards Preview

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Flashcards in Clinical Electrophysiology IV Deck (25):
1

Evaulation of Cardiac Arrhythmias

  • Symptoms due to an abnormal rhythm
  • Goal of arrhythmia evaluations

  • Symptoms due to an abnormal rhythm
    • Palpitations: unusual awareness of the heart beta
    • Tachycardia: rapid heart beat
    • Syncope: loss of consciousness
    • Presyncope: dizziness, lightheadedness
    • Chest pain
  • Goal of arrhythmia evaluations
    • Correlate symptoms w/ rhythm abnormality

2

12 Lead ECG

  • General
  • Assessment
  • Pros
  • Cons

  • General
    • Noninvasive tool
    • First step
  • Assessment
    • Heart rate
    • Conduction disease or abnormalities like WPW syndrome
    • Evidence of a prior MI
    • Evidence of various atrial or ventricular arrhythmias
  • Pros
    • Painless
    • Widely available
    • Inexpensive
  • Cons
    • Limited to a single 10 second recording of heart rhythm

3

Ambulatory or Holter Monitoring

  • General
  • Assessment
  • Pros
  • Cons

  • General
    • Noninvasive tool
    • Records heart rhythms for 24 hours
  • Assessment
    • Frequency of ectopic beats
    • Average heart rate
    • Episodies of tachycardia & bradycardia
  • Pros
    • Can see if the rhythm distrubances or symptoms occur at least once during the 24-hour period
  • Cons
    • Possible to miss an arrhythmic episode if an event doesn't occur during the 24-hour period
    • may fail to correlate symptoms w/ an abnormal rhythm

4

Patient Activated Event ("Loop," "King of Hearts") Recorders

  • General
  • Pros
  • Cons

  • General
    • Noninvasive tool
    • Patients activate the recorder when they feel symptoms
    • Rhythm recorded on the device is transmitted via telephone to the central station for interpretation
  • Pros
    • Assesses symptoms that occur less than daily buare are likely to occur ina reasonable period of time
  • Cons
    • Patients may not be able to activate the recorder at the time of the symptoms due to physical frailty or syncope

5

Implantable Loop Recorder

  • Noninvasive tool
  • Automatically records when it senses pauses, slow or fast HRs, or when the patient notices symptoms

6

Cardionet

  • General
  • Pros

  • General
    • Noninvasive tool
    • External loop recorder
    • Wearable monitor w/ a base unit that continuously transmits the rhythm to  a central monitoring center for interprtetation & monitoring
  • Pros
    • Good for patients that may not have time to activate a monitor prior to syncope or who don't "feel" the arrhythmia (ex. atrial fibrillation)

7

Signal Average ECG (SAECG)

  • General
  • Assessment
  • Cons

  • General
    • Noninvasive tool
    • Based on the assumption that areas of arrythmogenic ventricular muscle exhibit slow conduction that will be manifested as small potentials near the end of the QRS complex
    • Late potentials aren't seen on the avg ECG b/c of filtering that limits noise
    • If hundreds of QRS complexes are averaged, the "random noise" is cancelled out & these "late potentials" can be seen
  • Assessment
    • Assesses patient's risk of sudden cardiac death
    • Predicts future mortality after a MI
    • Not correlated w/ a symptom
  • Cons
    • Specificity is decreased if a patient has a baseline conduction abnormality (ex. BBB) or the noise level of the SAECG > 0.5

8

Heart Rate Variability (HRV)

  • General
  • Methods
  • Assessment
  • Pros

  • General
    • Noninvasive tool
    • Looks at cyclic changes in HR by analyzing the time b/n consecutive heart beats
  • Methods
    • Standard statistical methods
      • Time domain analysis
    • Transformation into the frequency domain
      • Uses the Fast Fourier Transform
      • Frequency domain analysis
  • Assessment
    • Arrhythmic risk
    • Decreases in parasympathetic (primarily vagal) activity are associated w/ increased mortality in post-MI patients
  • Pros
    • Decreased HR variability better predicts arrhythmic events than the SAECG, stress test, or EF measurements

9

T Wave Alternans

  • General
  • Assessment

  • General
    • Noninvasive tool
    • Look sfor microvolt changes in the size of the t wave
    • Alternating patterns of big & small amplitude t waves correlate w/ an increased risk for ventricular arrhythmias
  • Assessment
    • Patients who aren't at risk for cardiac arrhythmias

10

Electrophysiology (EP) Study

  • General
  • Method
  • Programmed electrical stimulation
  • Specialized studies

  • General
    • Invasive tool
    • Gold standard for evaluating cardiac arrhythmias
  • Method
    • Insert catheters to record intracardiac signals from critical regions of the cardiac conducting system
    • Catheters are normally placed near the SA node, AV node, Bundle of His, & RV apex
  • Programmed electrical stimulation
    • Catethers introduce pacing sitmuli & record to study the conducting system or induce arrhythmias (typically those w/ a reentrant mechanism)
  • Specialized studies
    • Catheters are placed into hte LV, LA, or coronary sinus
    • Recordings of conduction times & location where conduction fails or is blocked allows assessment of SA & AV nodal function
    • Determiens the need for a permanent pacemaker

11

Computer Based Mapping Systems

  • Invasive tools
  • Introduce extra stimuli to reproduce reentrant arrhythmias
    • Ex. VT associated w/ CAD, many types of SVT
  • Map the location of the focus or circuit responsible for the abnormal rhythm
  • Use GPS-like technology to construct 3D images of cardiac activation
  • Speeds ablation
  • Makes it possible to perform new procedures

12

Vaugn-Williams Antiarrhythmic Drugs: Classification & Representative Drugs

  • Class I
    • IA
    • IB
    • IC
  • Class II
  • Class III
  • Class IV

  • Class I: sodium channel blockers
    • IA
      • Procainamide
      • Quinadine
      • DIsopyramide
    • IB
      • Lidocaine
      • Mexilitine
      • Tocainide
    • IC
      • Flecainide
      • Encainide
      • Propafenone
  • Class II: beta blockers
    • Propranolol
    • Atenolol
    • Metoprolol
    • Timolol
    • Naldolol
    • Esmolol
  • Class III: potassium channel blockers
    • Amiodarone
    • Bretylium
    • NAPA
    • Sotalol
    • Dofetilide
  • Class IV: calcium channel blockers
    • Verapamil
    • Diltiazem
    • Nifedipine

13

Vaugn-Williams Antiarrhythmic Drugs: Effects

  • Class I
    • IA
    • IB
    • IC
  • Class II
  • Class III
  • Class IV

  • Class I: sodium channel blockers
    • IA
      • Increase AP duration & Effective Refractory Period (ERP)
      • Increase QRS & QT duration
      • Decrease slope phase 0
    • IB
      • Neutral effect on ERP
      • Decrease AP & QT duration
      • Decrease slope phase 0
    • IC
      • Neutral effect on ERP & AP duration
      • Decrease slope phase 0 & 4
  • Class II: beta blockers
    • Increase AV nodal refractoriness
    • Decrease AV conduction
    • Decrease chronotropy
  • Class III: potassium channel blockers
    • Increase AP duration & ERP
    • Increase PR interval
    • Increase QRS duration
    • Increase QT duration
  • Class IV: calcium channel blockers
    • Increase ERP of AV node
    • Block slow Ca2+ current

14

Vaugn-Williams Antiarrhythmic Drugs: Side Effects

  • Class I
  • Class II
  • Class III
    • Amiodarone
    • Sotolol
    • Dofetilide
  • Class IV

  • Class I: sodium channel blockers
    • *GI distress
    • CNS symptoms
    • Allergic reactions
    • *Lupus
    • Thrombocytopenia
    • Pro-arrhythmia
    • *Syncope (Quinidine)
  • Class II: beta blockers
    • Hypotension
    • Bradycardia
    • Worsening CHF
    • Worsening asthma or COPD
  • Class III: potassium channel blockers
    • Amiodarone
      • *Pulmonary toxicity
      • Bradycardia
      • GI symptoms
      • *Thyroid & liver abnormalities (hypothyroidism)
    • Sotolol
      • Class II effects + pro-arrhythmia
      • Contraindicated in patients w/ renal dysfunction
    • Dofetilide
      • Torsade de pointes
      • Contraindicated in patients w/ renal dysfunction
  • Class IV: calcium channel blockers
    • Hypotension
      Bradycardia
    • Worsening AV block
    • Liver function abnormalities

15

Medical Therapy for Supraventricular Arrhythmias

  • Treatment for supraventricular arrhythmias
  • Treatment for supraventricular arrhythmias where the AV node is part of the arrhythmia circuit
  • Treatment not effective in atrial rhythm abnormalities

  • Treatment for supraventricular arrhythmias
    • Class IA, IC, & III antiarrhythmic drugs
  • Treatment for supraventricular arrhythmias where the AV node is part of the arrhythmia circuit
    • Class IA, IC, & III antiarrhythmic drugs
    • Class II & IV antiarrhythmic drugs for their AV nodal blocking properties
  • Treatment not effective in atrial rhythm abnormalities
    • Class IB antiarrhythmic drugs

16

Clinical Risk Factors for Stroke

  • High risk
  • Moderate risk
  • Low risk ("lone atrial fibrillation")

  • High risk
    • Rheumatic valvular disease
  • Moderate risk
    • CHF within last 3 months
    • History of HTN
    • History of arterial thromboemboli
    • Global LV dysfunction
    • LA size > 4.7 cm
    • Left sided valvular abnormalities
  • Low risk ("lone atrial fibrillation")
    • Absnece of all other risk factors
    • Under 60yo

17

Atrial Fibrillation & Flutter

  • Atrial fibrillation
  • Anti-thrombotic therapy
  • CHADS2 Score
  • Warfarin vs. aspirin

  • Atrial fibrillation
    • Most common abnormal rhythm found in adults
    • Treatment: treat abnormal rhythm + prevent embolic complications
  • Anti-thrombotic therapy
    • Essential for treating both atrial fibrillation & flutter
    • Afib patients: at high risk for strokes if not receiving anticoagulation
  • CHADS2 Score
    • Assigns points for each risk factor
      • 2 points: prior stroke or TIA
      • 1 point: >75yo, HTN, diabetes, heart failure
    • Guideline recommendations
      • 0 points: no therapy
      • 1 point: aspirin or warfarin
      • >2: warfarin
  • Warfarin vs. aspirin
    • Warfarin: higher stroke risk reduction, higher risk of bleeding
    • Aspirin: lower stroke risk reduction, lower risk of bleeding
    • Except for patients w/ lone atrial fibrillation, anticoagulation w/ warfarin should be used unless the patient is contraindicated (ex. elderly w/ increased risk of bleeding)

18

Atrial Fibrillation & Flutter: Timing & Duration of Anticoagulation

  • AFib < 48 hours
  • AFib > 48 hours or unknown
  • AFib > 48 hours or unknown but can't wait 3 weeks
  • All cases

  • AFib < 48 hours
    • Low stroke risk, so attempt to restore sinus rhythm
  • AFib > 48 hours or unknown
    • Anticoagulate for 3 weeks before attempting to restore sinus rhythm
  • AFib > 48 hours or unknown but can't wait 3 weeks
    • Initiate anticoagulation
    • Inspect the LA for thrombus by transesophageal echo
    • If LA is thrombus-free, risk of thromboemboli from cardioversion is ~= to the risk of thromboemboli following 3 weeks of anticoagulation, so attempt to restore sinus rhythm
  • All cases
    • Maintain an INR for >3 weeks after sinus rhythm is restored, even w/ a negative transesophageal echo

19

Atrial Fibrillation & Flutter: Timing & Duration of Anticoagulation

  • AFFIRM trial
  • Current conditions for which anticoagulation & rate control are needed
  • Treatment for patient w/ disabling symptoms
  • Treatment for permanent AFib
  • Treatment for a patient w/ appropriate antithrombotic therapy that needs to restore sinus rhythm
  • Treatment of AFib in patients w/ WPW syndrome

  • AFFIRM trial
    • When managing AFib, a rhythm control strategy (restoring sinus rhythm) has no survival advantage over a rate control strategy (keeping the ventricular rate from beating too fast)
  • Current conditions for which anticoagulation & rate control are needed
    • Recurrent paroxysmal AFib
    • Recurrent persistent AFib
  • Treatment for patient w/ disabling symptoms
    • Consider antiarrhythmic drugs (rhythm control) & potential electrical cardioversion
  • Treatment for permanent AFib
    • Anticoagulation & rate control as needed
    • Ventricular rate control w/ concomitant antithrombotic therapy increases block in the AV node so the resulting ventricular rate/response is slowed
  • Treatment for a patient w/ appropriate antithrombotic therapy that needs to restore sinus rhythm
    • Cardioversion: electrical, synchronized transthoracic direct current counter-shock that terminates activity in the chaotic atrial foci to allow SA activity to emerge
    • Antiarrhythmic drugs: used for chemical cardioversion
      • Not as effective, but may be useful in patients when anesthesia (needed for electrical cardioversion) may pose additional risks
    • Risk fo periconversion stroke is the same for electrical & chemical cardioversion
  • Treatment of AFib in patients w/ WPW syndrome
    • AV nodal blocking agent (ex. digoxin) --> allows atrial conduction through the accessory pathway --> doesn't slow conduction --> sudden cardiac death --> don't use these
    • Procainamide / amiodarone --> slow both AV nodal & accessory pathway conduction --> avoid rapid ventricular response --> use these

20

Treatment Comparisons for HR Control in Atrial Fibrillation

  • Digoxin
    • Advantages
    • Disadvantages
  • Beta & calcium channel blockers
    • Advantages
    • Disadvantages
  • Amiodarone
    • Advantages
    • Disadvantages
  • AV node ablation
    • Advantages
    • Disadvantages

  • Digoxin
    • Advantages
      • Inexpensive
      • Widely available
    • Disadvantages
      • Poorly controls rate during activity
      • Digitalis toxicity
  • Beta & calcium channel blockers
    • Advantages
      • Controls rate well during activity
      • Relatively inexpensive
      • Widely available
    • Disadvantages
      • Effective rate controlling doses can have intolerable side effects
  • Amiodarone
    • Advantages
      • May help restore sinus rhythm
      • Widely available
    • Disadvantages
      • Pulmonary & thyroid side effects
      • Interactions w/ other drugs (warfarin)
      • Bradycardia & long half-life
  • AV node ablation
    • Advantages
      • Complete control of ventricular rate
    • Disadvantages
      • Requries life long permanent pacemaker

21

ICD vs. Drug Therapy for Ventricular Arrhythmias

  • Implantable cardioverter defibrillator (ICD) has largely eliminated drug therapy
    • Esp in patients w/ a prior MI & depresed EF
  • Sometimes, drugs are used in conjunction w/ ICD therapy to suppress ventriculra ectopy & reduce shocks from the defibrillator

22

Catheter Ablation Therapy for Arrhythmias

  • Procedure
  • Treats...

  • Procedure
    • Apply radiofrequency energy to a critical protion of the tachycardia circuit that was identified during an EP study
    • Safe, low morbidity, no mortality, & >95% cure rate
  • Treats...
    • Supraventricular tachycardias
    • AV node reentry tachycardia
    • SVT associated w/ WPW syndrome
    • AFib
    • Ventricular tachycardia

23

Device Related Therapy

  • General
  • Categories

  • General
    • Implanted devices that help maintain the appropriate heart rate by pacing the heart (pacemaker) or terminating abnormally fast heart rhythms (defibrillators)
  • Categories
    • Chamber paced
    • Chamber sensed
    • Response to sensing
    • Programmability, rate modulation
    • Anti-tachycardia functions

24

Pacemaker vs. Defibrilaltor (ICD) Therapy

  • Pacemaker
  • Class I indications for pacemaker implantation
  • Class I indications for defibrillator (ICD) therapy

  • Pacemaker
    • Pulse generator + lead wire that conducts energy from the pacemaker to the appropriate place in the heart
  • Class I indications for pacemaker implantation
    • Symptomatic bradycardia
    • Asystole > 3 seconds
    • Asymptomatic complete or high grade AV block w/ an escape rate < 40 bpm
  • Class I indications for defibrillator (ICD) therapy
    • Sudden cardiac deat not due to a transient or reversible cause
    • Sustained, spontaneous VT
    • Severe LV dysfunction that persists despite appropriate therapy

25

Biventricular Pacing / Cardiac Resynchronization Therapy

  • Requirements for patients to receive this therapy
  • Theory behind therapy

  • Requirements for patients to receive this therapy
    • History of Class III or IV CHF despite optimal medical therapy
    • History of LBBB
    • EF < 36%
    • QRS > 120ms
  • Theory behind therapy
    • LBBB --> delayed conduction to the LV --> RV & LV beat dyssynchronously
    • Regular RV pacing doesn't hepl b/c the impulse still takes a long time to travel to the LV
    • Need to pace both the RV & LV
    • Since placing a pacing lead in the LV causes a risk of embolic stroke, the left sided lead is placed in the coronary sinus to pace the LV free wall