Monophasic action potential duration alternans after abrupt shortening of the cardiac cycle in humans

BackgroundAction potential alternans may be important in causing ventricular arrhythmias.Methods and resultsWe recorded monophasic action potentials from the right ventricular endocardium in patients with persistent atrial fibrillation who underwent internal atrial defibrillation during rapid ventricular pacing. In 3 of 45 patients, monophasic action potential duration alternans was observed at a pacing cycle length ≤350 ms.ConclusionAction potential alternans is not a rare phenomenon (6.6%) in humans.