- Clinically significant AV conduction disturbances and/or arrhythmias (e.g. second- or third-degree AV block; sick-sinus syndrome or clinically significant bradycardia- resting heart rate < 45 beats/minute), tachyarrhythmias; clinically significant arrhythmias, presence of accessory bypass tract (e.g. Wolff-Parkinson-White syndrome)