Clinical Electrophysiology III Flashcards
1
Q
Wide Complex Rhythm: 2 Causes
A
- Ventricular tachycardia
- With ominous implications
- Supraventricular tachycardia
- With aberrant conduction (functional bundle branch block)
2
Q
Factors that Indicate Ventricular Tachycardia
- Most specific findings
- Less specific findings
A
- Most specific findings
- History of coronary arteyr disease & decreased LV EF
- AV dissociation
- Ventricular activity (not atrial) drives propagation of depolarizations & ventricular rate
- Direct evidence
- Distinct P waves
- Indirect evidence
- Capture (fusion) beats
- QRS complex forms when a ventricular depolarization occurs at nearly the same time as a normal impulse
- QRS complex looks like a fused copmlex of the normal & ventricular QRS complex
- Less specific findings
- Left axis deviation during wide complex tachycardia
- QRS complex > 0.14 sec
- R to nadir of S interval > 60 ms in precordial leads of LBBB morphology wide complex rhythms
3
Q
Forms of Ventricular Ectopic Beats
A
- Single premature ventricular contraction (PVC)
- Couplets: 2 beats in a row
- Bigeminy or Trigeminy: every 2nd or 3rd beat is a ventricular ectopic beat
- Accelerated idioventricular rhythm: 3 or more beats in a row, rate < 120 bpm
- Ventricular tachycardia: 3 or more beats in a row, rate > 120 bpm
- Ventricular fibrillation: rapid, often chaotic ventricular rhythm
4
Q
Premature Ventricular Contractions (PVCs)
- Normal heart
- Abnormal heart
- Treatment of ventricular ectopic beats (couplets) or alternating ventricular ectopic & normal beats (bigeminy)
A
- Normal heart
- General
- PVC aren’t associated w/ any additional mortality & aren’t markers of other cardiac problems
- Therapy for asymptomatic patients
- No other conditions: no therapy required
- If potassium or magnesium levels are abnormal: oral replacement therapy
- Therapy for symptomatic patients
- No therapy required to alter survival
- If symptoms interfere w/ daily activities: potassium/magnesium supplements, reassurance of benign PVC
- If treatments insufficient: stepped approach
- Beta blockers: 1st line, effective, safe
- Antiarrhythmic drugs: only if beta blockers fail, side effects, risks
- General
- Abnormal heart
- Side effect of drug therapy: pro-arrhythmia (creating new or worsening current arrhythmias)
- Sodium or potassium channel abnormality (long QT syndromes): make drug therapy more dangerous, excluded as a cardiac abnormality
- Treatment of ventricular ectopic beats (couplets) or alternating ventricular ectopic & normal beats (bigeminy)
- Same prognosis & treatment as PVCs
5
Q
Accelerated Idioventricular Rhythms
A
- aka “slow V tach”
- Same mechanism as V tach, but slower rate & slightly different prognosis
- Seen in recovery phase of an acute MI
- Only treat underlying cause (ex. MI)
6
Q
Ventricular Tachycardia
- Most common question
- Surest way to determine if a rhythm is ventricular
A
- Most common question
- Whether wide QRS complex beats & rhythm are venticular or due to a bundle branch block (permanent or functional)
- Funcitonal BBB = aberrant conduction
- Whether wide QRS complex beats & rhythm are venticular or due to a bundle branch block (permanent or functional)
- Surest way to determine if a rhythm is ventricular
- AV dissociation
7
Q
AV Dissociation
- Ventricular tachycardia
- EKG findings
- Direct evidence
- Indirect evidence
A
- Ventricular tachycardia
- Wide complex tachycardia shows no relationship to the activity in the atrium
- Ventricular rate is faster than the atrial rate
- Rhythm must be originating int he ventricle
- EKG findings
- Direct evidence: P wave & QRS complexes move separately across the tracing
- Indirect evidence: fusion or capture beats
8
Q
Fusion Beats
- General
- EKG findings
A
- General
- Due to simultaneous activation of the ventricle by both the ectopic ventricular focus & the normal conducting system
- Combination fo the ventricular beat & native QRS
- EKG findings
- QRS morphology looks like a summation of the intrinsic & ventricular-origin QRS complexes
- Normal QRS: if timing of atrial & ventricular activity is exactly right, all the ventricle may be activated by teh normal conducting system
- Capture beat: occurs in the middle of the wide complex tachycardia run
- Sometimes, all you see is the fusion or capture beat
9
Q
Cardiac Arrhythmia Suppression Trial (CAST)
- CAST
- Vaugn-Williams Class I antiarrhythmic drugs
A
- CAST
- Determined if suppression of ventricular ectopic beats would decrease mortality
- Copmared 3 drugs in patients w/ previous MIs
- Drugs: glecainide, encainide, & moricizine
- Each drug decreased ventricular ectopy but increased mortality
- Vaugn-Williams Class I antiarrhythmic drugs (esp class IC): poor choice in patients w/ coronary artery disease (CAD) & w/ decreased EF
- Increase mortality in post-MI patients
- Flecainide, encainide, & moricizine
- Neutral effect on mortality in post-MI patients (& maybe non-ischemic cardiomyopathy patients)
- Amiodarone, sotalol, & dofetilide
- Increase mortality in post-MI patients
10
Q
Sotalol
- Sotalol
- d,l-Sotalol
- d-Sotalol
- JULIAN trial
- SWORD trial
A
- Sotalol
- Class III Vaugn-Williams antiarrhythmic drug
- Effective against ventricular arrhythmias
- Primary antiarrhythmic drug for patients w/ a prior MI & depressed EF
- Ikr channel blocking agent
- d,l-Sotalol
- Racemic mixture
- Also has beta blocker properties
- d-Sotalol
- Pure isomer
- Lacks beta blocker properties of d,l-Sotalol
- JULIAN trial
- Long-term effects of d,l-Sotalol: neutral effect on mortality
- SWORD trial
- d-Sotalol: increased mortality (no longer used)
11
Q
Amiodarone
- Amiodarone
- European Myocardial Infarction AMiodarone Trial (EMIAT)
- Canadian Amiodarone Myocardial Infarction Arrhythmia Trial (CAMIAT)
A
- Amiodarone
- Class III antiarrhythmic drug
- Treats ventricualr & supraventricular arrhythmias
- Primary antiarrhythmic drug for patients w/ a prior MI & depressed EF
- European Myocardial Infarction AMiodarone Trial (EMIAT)
- Decreased mortality in post-MI patients
- Neutral effects on mortality in non-post-MI patients
- Canadian Amiodarone Myocardial Infarction Arrhythmia Trial (CAMIAT)
- Decreased risk of arrhythmic death
- Not significant beneficial effect on all-cause mortality
12
Q
Dofetilide
A
- Dofetilide
- Class III antiarrhythmic drug
- Only FDA approved to treat atrial fibrillation & flutter
- Similar to amiodarone
- Danish Investigations of Arrythmia & Mortality on Dofetilide Study (DIAMOND-MI)
- Neutral effect on mortality
13
Q
Device Therapy of Ventricular Arrhythmias
- Cardiac Arrest Study in Seattle (CASCADE)
- Antiarrhythmics versus Implantable Defibrillators (AVID)
- Cardiac Arrest Study Hamburg (CASH)
- Canadian Implantable Defibrillator Study (CIDS)
- Bottom line
A
- Cardiac Arrest Study in Seattle (CASCADE)
- Patients: post-cardiac arrest, not MI
- Amiodarone had better cardiac survival but more pulmonary toxicity
- Antiarrhythmics versus Implantable Defibrillators (AVID)
- Patients: post-SCD or post-sustained VT
- Implantable Cardioverter Defibrillator (ICD): reduced mortality in patients w/ decreased EFs
- Amiodarone & ICD equally effect in reducing mortality in non-ischemic cardiomyopathy patients
- Cardiac Arrest Study Hamburg (CASH)
- Patients: post-sudden cardiac death (SCD), not MI
- Propafenone (IC drug): increased mortality
- ICD: reduced mortality & SCD than amiodarone & metoprolol
- Canadian Implantable Defibrillator Study (CIDS)
- Patients: post-SCD or post-sustaiend VT
- ICD: reduced mortality than amiodarone (not statistically significant)
- Bottom line
- ICD: increased survival in ischemic population (sudden cardiac death or sustained ventricular tachycardia)
- ICD & amiodarone: equally effective in increasing survival in non-ischemic population
- Class IC antiarrhythmic drugs: increase mortality
14
Q
Nonsustained Ventricular Arrhythmias
- Multicenter Unsustained Tachycardia Trial (MUSTT)
- Bottom line
A
- Multicenter Unsustained Tachycardia Trial (MUSTT)
- Patients: post-MI, decreased EF, nonsustained VT
- EP: reduced arrhythmic death & cardiac arrest
- ICD: survival benefit
- Bottom line
- Patients: post-MI, decreased EF, nonsustained VT
- ICD: reduces mortality the best
15
Q
LV Dysfunction
- Multicenter Automatic Defibrillator Implantation Trial (MADIT I)
- Multicenter Automatic Defibrillator Implantation Trial (MADIT II)
- Sudden Cardiac Death Heart Failure Trial (SCD-HeFT)
- Bottom line
A
- Multicenter Automatic Defibrillator Implantation Trial (MADIT I)
- Patients: post-MI, decreased LV EF, nonsustained VT
- ICD: reduced mortality
- Multicenter Automatic Defibrillator Implantation Trial (MADIT II)
- Patients: post-MI, decreased EF
- ICD: reduced mortality
- Sudden Cardiac Death Heart Failure Trial (SCD-HeFT)
- Patients: decreased EF
- ICD: reduced mortality
- Bottom line
- Patients w/ significant LV dysfunction have best survival w/ ICD