Hi,
Ventricular fibrillation is a condition where in the ventricles beat abnormally at a very higher rate causing loss of blood supply to the brain and leading to a collapse. Before getting collapsed you might experience chest pain, dizziness, rapid heart beat, nausea or shortness of breath about an hour before.
As, you have a history of congestive heart failure, which is one of the risk factors for developing ventricular fibrillation further evaluation by a cardiologist should be considered. A holter monitoring or continuous 24 hour cardiac rhythm monitoring is required for conclusion on the cause for this. Best.
I am not a doctor but If you just "felt" and are not recorded, I think can be anything.
I suggest you to go to cardiologist for a Holter test.
Jesus