Ventricular Fibrillation is not a heart attack (heart attack is already an imprecise lay term) but I don't think encouraging it's use for anything other than acute myocardial ischemia is a good idea. In that sense, lidocaine doesn't stop a heart attack.
A heart attack may lead to arrhythmias like VF. But VF is not a heart attack.
Lidocaine is a sodium channel blocker, it controls arrhythmias by blocking or diminishing the disorganized electrical activity going on in heart while hopefully not squelching whatever remaining dominant organized pacemaker activity there is.
It is not the only antiarrhythmic though and relatively not a common one even for VF, it is not generally first line in its class. It's role in life support is a complicated subject but it is an optional drug for use in in-hospital CPR (ACLS) for VT/VF. High quality CPR and defibrillation are far more important though.
Lidocaine is a sodium channel blocker, it controls arrhythmias by blocking or diminishing the disorganized electrical activity going on in heart while hopefully not squelching whatever remaining dominant organized pacemaker activity there is. It is not the only antiarrhythmic though and relatively not a common one even for VF, it is not generally first line in its class. It's role in life support is a complicated subject but it is an optional drug for use in in-hospital CPR (ACLS) for VT/VF. High quality CPR and defibrillation are far more important though.