Ajmaline Challenge To Unmask Infrahisian Disease In Patients With Recurrent And Unexplained Syncope, Preserved Ejection Fraction, With Or Without Conduction Abnormalities On Surface ECG.

: Background: Pharmacological challenge with class I antiarrhythmic drug is a recommended diagnostic test in patients with unexplained syncope only in the presence of bundle branch block, when non-invasive tests have failed to make the diagnosis. Its role in patients with minor or no conduction disturbances on 12-leads ECG has not been evaluated yet. It is also not clear which are the values of His-Ventricular interval to be considered diagnostic. We sought to evaluate the role of ajmaline challenge in unmasking the presence of an infrahisian disease in patients with recurrent and unexplained syncope, regardless of the existence of conduction disturbances on surface ECG. Materials And Methods: Patients with history of recurrent syncope, preserved EF and a negative first level workup were enrolled. Conduction disturbances on ECG were not considered as an exclusion criteria. During EPS, basal HV conduction was determined. In the presence of a HV >70 msec the study was interrupted and the patient was implanted with a pacemaker. If the HV was ≤ 70 msec, ajmaline was infused and HV was reassessed. The maximum value of HV was considered. A prolongation ≥ 100 msec was considered as diagnostic and indicative of conduction disease, and the patient underwent pacemaker implantation. Patients with an HV 70 msec in basal conditions and ≥ 100 msec after ajmaline administration seem appropriate to unmask infrahisian disease. Larger population is required to validate this hypothesis.