Clinical Electrophysiology III Flashcards Preview

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Flashcards in Clinical Electrophysiology III Deck (23):
1

Wide Complex Rhythm: 2 Causes

  • Ventricular tachycardia
    • With ominous implications
  • Supraventricular tachycardia
    • With aberrant conduction (functional bundle branch block)

2

Factors that Indicate Ventricular Tachycardia

  • Most specific findings
  • Less specific findings

  • 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

Forms of Ventricular Ectopic Beats

  • 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

Premature Ventricular Contractions (PVCs)

  • Normal heart
  • Abnormal heart
  • Treatment of ventricular ectopic beats (couplets) or alternating ventricular ectopic & normal beats (bigeminy)

  • 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
  • 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

Accelerated Idioventricular Rhythms

  • 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

Ventricular Tachycardia

  • Most common question
  • Surest way to determine if a rhythm is ventricular

  • 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
  • Surest way to determine if a rhythm is ventricular
    • AV dissociation

7

AV Dissociation

  • Ventricular tachycardia
  • EKG findings
    • Direct evidence
    • Indirect evidence

  • 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

Fusion Beats

  • General
  • EKG findings

  • 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

Cardiac Arrhythmia Suppression Trial (CAST)

  • CAST
  • Vaugn-Williams Class I antiarrhythmic drugs

  • 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

10

Sotalol

  • Sotalol
  • d,l-Sotalol
  • d-Sotalol
  • JULIAN trial
  • SWORD trial

  • 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

Amiodarone

  • Amiodarone
  • European Myocardial Infarction AMiodarone Trial (EMIAT)
  • Canadian Amiodarone Myocardial Infarction Arrhythmia Trial (CAMIAT)

  • 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

Dofetilide

  • 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

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

  • 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

Nonsustained Ventricular Arrhythmias

  • Multicenter Unsustained Tachycardia Trial (MUSTT)
  • Bottom line

  • 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

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

  • 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

16

Limitations of the ICD

  • ICDs can increase the quantity, but not the quality, of life
  • They represent a resource-intensive tehrapy that may not be appropriate in some circumstances
    • i.e. advanced age, multiple comorbid illnesses
  • Patients' values & outlook are an important part of the decision making process

17

Ventricular Arrhythmias Not Related to CAD

  • Non-ischemic, dilated cardiomyopathy
  • Long QT Syndromes
    • Acquired
      • Most common cause
      • Less common cause
    • Congenital
      • General
      • Genetic defects
      • Two forms
      • Treatment

  • Non-ischemic, dilated cardiomyopathy
    • Treated the same as patients w/ ischemic cardiomyopathy & similar EF
  • Long QT Syndromes
    • Acquired: most common type
      • Most common cause: QT prolonging drug
        • Ex. Dofetilide for atrial fibrillation
      • Less common cause: metabolic abnormality (hypokalemia, hypomagnesaemia)
    • Congenital
      • General
        • Exclude metabolic & toxic abnormalities
        • Seein in patients w/ syncope & w/ a FH of unexplained death in relatives under 30yo
      • Genetic defects
        • DNA coding voltage dependent potassium channels (LQT1, LQT2, LQT3)
        • DNA coding voltage dependent sodium channels (SCN5A)
      • Two forms
        • Romano-Ward: AD
        • Jervell-Lange-Nielsen: AR, associated w/ congenital deafness
      • Treatment (untreated --> mortality)
        • Stellate galnglia sympathectomy
        • Combined beta-blocker & pacer therapy
        • Implantable Cardioverter Defibrillator (ICD)

18

QT Interval Prolongation

  • Concern
  • Patient experiences...

  • Concern
    • If a QRS complex falls on the vulnerable period of the T wave --> polymorphic VT or ventricular fibrillation
    • Prolonged QT interval --> increased risk of this --> increased risk of arrhythmia
  • Patient experiences...
    • Slow HR & long QT interval --> "long-short" coupling interval --> arrhythmia
  • Effects of PVC on T wave
    • Fail to induce additional ectopy
    • Induce non-sustained VT
    • induce a sustained ventricular arrhythmia
  • Sustained ventricular arrhythmia
    • Torsade de pointes: cyclic pattern
    • Almost always fatal unless prompt defibrillation

19

Brugada Syndrome

  • Congenital long QT syndrome
  • Inherited ion channel abnormality
  • Abnormal ST segment in leads V1 & V2
  • Leads to increased risk of sudden death
  • Treatment: ICD

20

Mitral Valve Prolapse

  • General
  • Assessment
  • Treatment

  • General
    • Redundant leaflet of the mitral valve
      • aka floppy valve, Barlow's, or click-murmur syndrome
    • Low incidence of sudden cardiac death
  • Assessment
    • Asymptomatic: nothing
    • Palipitations, presyncope, or syncope: holter or event recorder monitoring
    • Significant ventricular arrhythmias: EP study
  • Treatment
    • First line: beta blockers

21

Hypertrophic Cardiomyopathy (HOCM)

  • General
  • Indications for increased risk for sudden cardiac death
  • Treatment

  • General
    • Abnormal thickening of the ventricular muscle w/ cellular disarray
  • Indications for increased risk for sudden cardiac death
    • History of ysnceope or presyncope
    • Nonsustained ventricular tachycardia
    • Palpitations
    • FH of sudden cardiac death
  • Treatment
    • EP study & guided therapy only if symptoms are present

22

Post Aortic Valve Replacement Surgery

  • General
  • Treatment

  • General
    • Increased ventricular ectopy --> sudden deaths
  • Treatment
    • EP study in patients w/ symptomatic palpitations or complex ventricular ectopy

23

Corrected Congenital Heart Disease

  • Surgical corrections to congenital heart disease
  • Tetralogy of Fallot

  • Surgical corrections to congenital heart disease
    • Extensive surgery of the ventricular muscle --> abnormal hemodynamics
    • Scar & chronic hemodynamic stress --> increased risk of ventricular arrhythmias
    • More extensive ventricular repairs (ex. single outlet ventricles) --> increase risk of ventricular arrhythmias
  • Tetralogy of Fallot
    • Most common corrected congenital heart disease
    • Surgical repair --> scar --> arrhythmias
      • Atrial scars --> atrial arrhythmias (esp atrial fibrillation)
      • Ventricular scars related to VSD repair & correction of pulmonary stenosis --> ventricular arrhythmias
    • Changes in surgical technique to minimize ventricular insults --> decrease ventricular arrhythmias