Alternating right bundle branch block or intermittent preexcitation?

Ángel Cueva-Parra, Electrophysiology Department, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
Michael Soto-Gamarra, Department of Cardiology, Hospital Regional Docente de Cajamarca, Cajamarca, Peru
Pedro Iturralde-Torres, Electrophysiology Department, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico
Santiago Nava, Electrophysiology Department, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico

Right bundle branch block (RBBB) is a very common electrocardiographic feature in patients with Ebstein anomaly (EA) and it is present in more than 94% of these patients¹.