Ventricular Fibrillation (VF) is the most frequent cause of death in myocardial
infarction.
The primary Ventricular fibrillation is the VF that is occurring in less than
24 hours (before revascularization). This is accounting for 90% of all
pre-hospital deaths in STEMI. The primary VF also can be appeared as so-called
reperfusion arrhythmias after thrombolysis. Here the immediate defibrillation
is the only first-choice treatment, not anti-arrhythmic drugs.
The secondary Ventricular fibrillation is the VF that is
occurring in more than 24 hours (after revascularization which has a worse
prognosis). It is mainly due to two factors whether remained anatomical
arrhythmogenic substrate or as a result of heart failure. Here the first-choice
treatment is anti-arrhythmic therapy or ICD implantation as soon as possible
after 4 weeks, but, as a bridging therapy, the wearable defibrillator must be
undertaken.
If the VF occurs after PCI with stent implantation, acute
stent thrombosis must be considered which has a 50% mortality rate and in this
scenario, the patients need re- catheterization.
If the VF occurs after 48 hours and acute stent thrombosis is
ruled out in SCD- HeFT Study: not more effective than placebo and in NYHA class
III patients even increase the mortality. This trial showed a lack of survival
benefit for treatment with amiodarone vs. placebo in patients with LVEF ≤35%. Unlike
sodium channel blockers, however, amiodarone can be used without increasing
mortality in patients with HF.
Amiodarone has a broad spectrum of action that includes
blockade of depolarizing sodium currents and potassium channels that conduct
repolarizing currents; these actions may inhibit or terminate VAs by
influencing automaticity and re-entry.
