ECG
CBC
BMP
TSH
CXR
Troponin in patients with suspicion for underlying heart disease or failure
Consider extended electrolytes (Mg/Phos)
Consider toxicologic work-up if concern for intoxications
Thyroid exam
Careful cardiac exam for murmurs
Cardiac monitoring
Consider walk test if<unk>  primarily present with exertion
Palpitations
Arrhythmias:
Chest pain 
Narrow-complex tachycardias
Heart murmurs
Wide-complex tachycardias
Hypopyon
AV blocks