No, not always.
There are three mechanisms.
1) Ventricular fibrillation (as you've mentioned)
2) Asystole ("flatline")
3) Electromechanical dissociation or "pulseless electrical activity" - where electrical activity (like sinus rhythm) is present but the heart isn't beating.
Asystole can be a result of VF or extreme bradycardia/complete heart block, where pulseless electrical activity could be caused by massive MI's or something obstructing the heart from beating (like liters of fluids in the pericardium)
hello and thank you for your reply, it's interesting to know that. To be honest, I thought that almost every case of death was preceded by VF, but I was wrong.
I know a case of a person who was alive and doing well, and in the "next second" was dead, literally. The autopsy revealed that it was caused by a piece of plaque. So, it was probably the 3rd scenario, correct?
Heart attacks can cause SCD through all three mechanisms. Ventricular fibrillation is more common in the setting of tachyarrhythmias (VT), bradycardia or asystole may happen if the conduction system is blocked by the heart attack, and EMD/PEA may be the result if the heart suffers severe damage.
CAD is the major cause of SCD. The conditions we tend to fear, like LQT, IVF, ARVC, Brugada, CPVT, etc, are extremely rare. CAD kills one of three of us, I think.