depends on operator experience, arrhythmia target location, and patient preference. Published trials, including a meta- analysis comparing radiofrequency ablation with cryoabla- tion for treatment of AVNRT, have shown a higher rate of recurrence with cryoablation but lower risk of permanent AV The rate of AVNRT recurrence with cryo- ablation depends on the size of the ablation electrode and the endpoint used.156,159 Ultimately, the choice of technol- ogy should be made on the basis of an informed discussion between the operator and the patient. 3. Sinus Tachyarrhythmias In normal individuals, the sinus rate at rest is generally between 50 bpm and 90 bpm, reflecting vagal tone.160 163 Sinus tachycardia refers to the circumstance in which the sinus rate exceeds 100 bpm. Sinus tachycardia may be appropriate in response to physiological stimuli or other exogenous factors or may be inappropriate when the heart rate exceeds what would be expected for physical activity or other circumstances. On the ECG, the P wave is upright in leads I, II, and aVF and is biphasic in lead V1. As the sinus rate increases, activation arises from more superior aspects of the right atrium, resulting in a larger-amplitude P wave in the inferior leads. Table 5. 