“…Beneath the cases of WPW pattern, alternans pre-excitation was rare, occurring in only four (2.2%) patients – half of them further developed AVRT-related symptoms. Although the intermittent loss of pre-excitation has historically been associated with low-risk AP, recent studies with both symptomatic and asymptomatic subjects demonstrated that over one-fifth of patients with intermittent WPW pattern presented AP ERP <250 ms. 15 Unfortunately, Lim et al could not provide information on risk stratification due to the small number of patients presenting alternans pre-excitation, the absence of invasive electrophysiologic information, and the limited follow-up period in their study. 15 More studies are needed to confirm the reported prevalence of alternans pre-excitation and evaluate its impact on patient prognosis.…”