Amiodarone in Ischemic VT : Doesn’t work always,.. IRA patency could be the missing link.
Curiously, the management of VT is simple if the patient is unstable. Just, we need to shock. Cardiologists are troubled only with a hemodynamically stable patient with VT. Some of us still think Amiodarone is a universal antidote for any VT. Though It is effective in both ischemic and non -Ischemic VT, the success rate is not uniform.
The mechanism of action of the Initial IV bolus is not a class 3 K + blocking action, instead, it is thought to be its beta-blocking action. If amiodarone fails, we may try Lignocaine, magnesium, Flecainide. .Many times it is the cumulative dose of amiodarone that reverts the VT. In some patients, it may reduce the ventricular rate instead of reverting to sinus rhythm. This is due to the prolongation of re-entrant circuit time. The question of amiodarone worsening polymorphic VT with a deleterious effect on the QT interval is still not clear yet.
Why Amiodarone fails to revert VT in some ?(Up to 40 % ?)
One of the factors we looked at some 15 years back was the relationship between IRA patency and amiodarone efficacy. Presented in CSI meet 2004.
It was a simple conclusion. For Amiodarone to be effective IRA must be at least partially patent to enable the drug to reach the target tissue. I am not aware of any study on this issue. Request anyone to expand this study and publish it as a full paper. (Royalty-free research topic!) Please acknowledge the concept if you think it’s original.