Class I
(1) In patients with ischemic heart disease, EP study is indicated when initial evaluation suggests an arrhythmic cause of syncope unless there is already an established indication for ICD.

Class IIa
(1) In patients with BBB, EP study should be considered when non-invasive tests have failed to make the diagnosis.

Class IIb
(1) In patients with syncope preceded by sudden and brief palpitations, EP Study may be performed when other non-invasive tests have failed to make the diagnosis.

(2) In patients with Brugada syndrome, ARVC, and hypertrophic cardiomyopathy, an EP Study may be performed in select cases.

(3) In patients with high-risk occupations, in whom every effort to exclude a cardiovascular cause of syncope is warranted, an EP Study may be performed in selected cases.

Class III
(1) EP Study is not recommended in patients with normal ECG, no heart disease, and no palpitations.

Class I
(1) EP Study is diagnostic and no additional tests are required, in the following cases:
(a) Sinus Bradycardia and prolonged CSNRT (>525 msec)
(b) BBB and either a baseline HV of > 100 msec, or second or third degree His-Purkinje block is demonstrated during incremental atrial pacing, or with pharmacologic challenge.
(c) Induction of sustained monomorphic VT in patients with previous myocardial infarction.
(d) Induction of rapid SVT which reproduces hypotensive or spontaneous symptoms.

Class IIa
(1) An HV interval between 70-100 msec should be considered diagnostic.

European Heart Journal (2009) 30, 2631-2671.