A method and medical device for delivering an atrial pacing pulse to an atrial chamber to generate an evoked atrial depolarization, delivering a stimulation pulse to an atrioventricular node during a stimulation window to increase a PR interval of the heart, the stimulation window having a start time corresponding to the delivered atrial pacing pulse so that the stimulation pulse is delivered during a refractory period corresponding to the evoked atrial depolarization, and delivering a ventricular pacing pulse to a first ventricular chamber during the increased PR interval to cause a contraction of the first ventricular chamber to occur prior to a contraction of a second ventricular chamber to increase dyssynchrony between the contraction of the first ventricular chamber and the contraction of the second ventricular chamber.
