VENTRICULAR ARRHYTHMIAS


 Amiodarone is often used in the management of sustained ventricular arrhythmias both in the presence and absnce of hemodynamic instability

Frequent PCVs (> 30/h) can be a sign of CAD

Ventricular fibrillation: Treated with CPT, electrical defibrillation, epinephrine, and vasopressin; if not responsive, amiodarone is sometimes used and as an alternative, lidocaine.

Causes of ventricular irritability

  1. Hypoxia
  2. Hypokalemia
  3. Certain medications
  4. Ischemia
  5. Etc.

Torsades des pointes

Features:

  1. Preceded by long QT interval
  2. Polymorphic VT
  3. Tachycardia initiated with a late coupled PVC

Causes:

  1. Drugs (see also NEJM 350:1013, 2004)
    1. Antiarrhythmics: IA (quinidine, procainamide, disopyramide), IC (encainide, flecainide), III (amiodarone, sotalol)
    2. Tricyclics
    3. Certain antipsychotics (chlorpromazine, haloperidol, mesoridazine, thioridazine, pimozide)
    4. Certain antibiotics (clarithromycin, erythromycin, pentamidine, sparfloxacin)
    5. Certain antiemetics (domperidone, droperidol)
    6. Cisapride
    7. Methadone
  2. Hypokalemia
  3. Hypocalcemia
  4. Hypomagnesemia
  5. Myocardial ischemia
  6. Congenital long-QT syndromes (e.g. Romano-Ward)

Treatment:

  1. IV magnesium is a common emergency treatment
  2. Treat underlying cause, if possible
  3. Pacing to avoid sinus pauses, which will prime the ventricle for torsades des pointes
  4. Automated Implantable Cardiac Defibrillators (AICDs)
    1. In a study of 1,000 pts who had been resuscitated from VFib or pulseless VT and were randomized to either an AICD vs. anti-arrhythmic pharmacotherapy (us. amiodarone) and f/u'd for 18mos, sig. lower death rate in the AICD group (16% vs. 24%), which persisted after adjustment for various confounders (NEJM 337:1576, 1997--JW)
  5. Fish Oil supplements
    1. In a study in 200 pts with AICDs for ventricular arrhythmias randomized to fish oil 1.8g/d vs. placebo, over median 24mo f/u, there was no sig. diff. in incidence of AICD discharge.  Among pts with prior VT, the fish oil group had sig. greater incidence of AICD firing during the study period (JAMA 293:2884, 2005--JW)
    2. In a study of 546 pts with ICDs and f/u VFib or VTach randomized to fish oil 2g/d vs. placebo, over median 1y f/u, incidence of (ICD discharge for spontaneous VFib or VTach, or death) was not sig. diff. between the groups; no subgroups identified with a sig. diff (JAMA 295:2613, 2006--JW)