Clinical Electrophysiology IV Flashcards
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
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

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

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
Implantable Loop Recorder
- Noninvasive tool
- Automatically records when it senses pauses, slow or fast HRs, or when the patient notices symptoms
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)

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

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
- Standard statistical methods
- 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
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
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

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

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
- IA
- 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
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
- IA
- 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
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
- Amiodarone
- Class IV: calcium channel blockers
- Hypotension
Bradycardia - Worsening AV block
- Liver function abnormalities
- Hypotension
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
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
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
- Assigns points for each risk factor
- 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)
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
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
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
- Advantages
- Beta & calcium channel blockers
- Advantages
- Controls rate well during activity
- Relatively inexpensive
- Widely available
- Disadvantages
- Effective rate controlling doses can have intolerable side effects
- Advantages
- Amiodarone
- Advantages
- May help restore sinus rhythm
- Widely available
- Disadvantages
- Pulmonary & thyroid side effects
- Interactions w/ other drugs (warfarin)
- Bradycardia & long half-life
- Advantages
- AV node ablation
- Advantages
- Complete control of ventricular rate
- Disadvantages
- Requries life long permanent pacemaker
- Advantages
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
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

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
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

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
