Tuesday, January 11, 2022

Primary Vs. Secondary Ventricular Fibrillation

 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.

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