A case of unidirectional exit block during pulmonary vein isolation

We present a case of unidirectional exit block from a pulmonary vein (PV) during a pulmonary vein isolation procedure. Following circumferential antral applications around the right PVs, PV pacing showed capture without exit. Meanwhile coronary sinus pacing showed continuous presence of delayed PV potentials. Our case is a rare example of unidirectional exit block since unidirectional block usually concerns entrance block.