Low catecholamines? do docs ever check for this in extremely fatigued patients with bradycardia?

Not usually: The usual causes of fatigue and bradycardia checked for include underactive thyroid and primary cardiac conditions causing slow heart rates such as extreme sinus bradycardia, various degrees of heart block, medication side effects or toxicity,elevated potassium levels. Catecholamines are usually checked in cases of hypertension or tachycardia.