In the BEAUTIFUL (Morbidity-Mortality Evaluation of the If Inhibitor Ivabradine in Patients With Coronary Disease and Left-Ventricular Dysfunction) study,166 with coronary disease and a left ventricular ejection frac- tion <40% were randomized to ivabradine or placebo. In the SHIFT (Systolic Heart Failure Treatment With the If Inhibitor Ivabradine) trial,167 6558 patients with a left ventricular ejection fraction 35% were randomized to ivabradine or placebo. In both of these trials, therapy with ivabradine resulted in additional heart rate reductions of 6 to 8 bpm and proved to be generally safe. The drug has no other hemodynamic effects aside from lowering the heart rate. As such, it has been investigated for use to reduce the sinus rate and improve symptoms related to IST.168 176 Radiofrequency ablation to modify the sinus node can reduce the sinus rate, with acute procedural success rates reported in the range of 76% to 100% in nonrandomized Ablation is typically performed with 3-dimen- sional electroanatomic or noncontact mapping techniques targeting sites of early activation with isoproterenol infusion, with or without use of intracardiac ultrasound guided map- ping to image the crista terminalis. Nonetheless, symptoms commonly recur after several months, with IST recurrence in up to 27% and overall symptomatic recurrence (IST or non- IST AT) in 45% of patients.177,179,180,182 Complications can be significant and may include symptomatic sinus or junctional bradycardia necessitating pacemaker placement, phrenic nerve injury with paralysis of the right hemidiaphragm, and significant facial and upper-extremity swelling caused by narrowing of the superior vena cava/RA junction, which may rarely result in superior vena cava syndrome. 