Ventricular fibrillation is the most dreaded cardiac arrhythmia during STEMI .If it occurs outside the hospital , it is usually a farewell arrhythmia to most patients . If it occurs within CCU , it is a well tackled arrhythmia and has little impact on long term mortality.
When it occurs in early hours of STEMI it is referred to as primary VF.
Even though it is a killer arrhythmia , primary VF is often an one time re- perfusion arrhythmia. There is no entity called recurrent primary VF .
If recurrent VF occurs some other mechanism is to be suspected (Drug, hypoxia, scar, ion channel defect etc)
Primary VF is ischemia triggered and secondary VF is infarct area triggered .Hypoxia , LVF or old scars also could contribute .
How to terminate primary VF ?
Immediate defibrillation is the only option.
After a successful reversion of VF should we follow it up with anti arrhythmic drugs routinely ?
No . It is not routine.(This is what we are debating today !)
What if , multiple VPDs and non sustained VT continue to occur in the ensuing hours after an episode of primary VF ?
It is indeed appropriate , to use an infusion of Amiodarone or lignocaine in such situation . Following it with oral Amiodarone is generally not required if the LV function is well-preserved.
Advantage and disadvantages of Amiodarone
- Pro arrhythmia – A undermined issue.
- Myocardial depressive action of Amiodarone is a deterrent for its routine use.
- Amiodarone induced bradycardia (If it is not a AV block ) may be an advantage as MVO2 may be reduced.
By the way , Lignocaine how does it fare vis-a-vis Amiodarone ?
It is equally a good drug with less side effects .But the ALIVE study delivered a death knock for this wonder drug. Many (At-least me !) would still believe the unpopularity of Lignocaine among the current generation cardiologists is not due to academic reasons .
So what is the final message ?
- Even though popular opinion and ( even some guidelines ) suggest it may not be necessary to give anti arrhythmic drugs after successful reversion of primary VF . It is prudent to weigh the risks. We can’t use it as a routine .
- Still , it is always wiser to prevent further episodes of VF (Rare though ) .
- If you have a well performing CCU , routine post shock Amiodarone is not advised .
- If you do not trust your CCU staff one may have to rely on these drugs.
- Patients with complicated MI , high risk VPDs ( Akin to after shocks after an earth quake ! ) especially in large anterior MIs should receive intensive anti-arrhythmic therapy (IV followed by oral )
**Never plan for an ICD in patient’s with primary VF it is an absolute contraindication.
***Recurrent VT/VF in the setting of STEMI is often termed as electrical storm .It is a rare event which will require immediate CABG/PCI with VT ablation. Again ICDs are contraindicated here as the battery depletion will be fast .Further ICDs it does not cure the VT rather it allows it to emerge from within and then try to tackle it, while RF ablation eliminates VT focus and prevents it,s origin and provide a potential cure. But , remember only 20% of VT are amenable for RF ablation , while ICD counters all VTs wherever it originates . So there is a role for combination of ablation and then putting an ICD .