Based upon the patient's history and demographics, the following laboratory studies should be considered:
Serum electrolytes including Ca, Mg
TFTs should be checked
Hypoglycemia should be excluded
Consider a toxicologic screen
Sinus bradycardia laboratory findings
Right bundle branch block laboratory findings
Premature atrial contraction laboratory findings
Junctional bradycardia laboratory findings
Ventricular tachycardia laboratory findings
Wide complex tachycardia laboratory findings
Bradycardia laboratory findings
Atrial flutter laboratory findings