Are thoughts of "doom" or foreboding symptomatic of chf, pph, and, or afib?

No: No, they're thoughts of anxiety which should be addressed directly. It is much more anxiety provoking to deal with the unknown - many fears are borne of uncertainty and none of us do well with uncertainty, so check with your doc and address your actual health issues (af, chf) and you'll discover they're all treatable and controllable.

Interesting question: If you have important levels of congestive heart failure, primary pulmonary hypertension, or if atrial fibrillation causes decreased cardiac output, you can have some level of activation of the sympathetic nervous system (the fight or flight system.) some people are very sensitive to this and seem to have symptoms like you describe. If the "heart failure" improves, these symptoms lessen.