Atrial latency in a dual chambered pacing system causing inappropriate sequence of cardiac chamber activation.

A transvenous atrioventricular pacemaker was implanted in a patient in whom junctional bradycardia and recurrent ventricular tachycardia had occurred after coronary artery bypass surgery. The period between delivery of the atrial stimulus and resultant atrial excitation was prolonged by up to 0.22 seconds and exceeded the programmed delay between atrial and ventricular stimulation. Consequently, ventricular stimulation preceded atrial excitation. Cardiac failure resulted: it was resolved by reprogramming the pacemaker to the atrial inhibited mode.