Table 5: Investigation of Inappropriate Sinus Tachycardia Syndrome according to the Heart Rhythm Society.

Recommendation	CoR	LoE
A complete history and physical exam and 12-lead ECG are recommended.	I	E
It might be useful to obtain complete blood count and thyroid function studies.	IIa	E
A 24-hour Holter monitoring might be performed.	IIb	E
It might be useful to obtain urine/serum drug screen.	IIb	E
It might be useful to consider autonomic testing.	IIb	E
It might be useful to consider treadmill exercise testing.	IIb	E

CoR = class of recommendation; LoE = level of evidence.[1]