Inappropriate sinus tachycardia (IST) is a clinical syndrome defined by an increase in sinus rate out of pro- portion to physiologic needs. It is an under-appreciated etiology of persistent tachycardia often misdiagnosed as anxiety or atrial tachycardia. Prior reports of radiofrequency catheter ablation have demonstrated only moderate long- term success rates with risks of significant damage to the sinus node requiring treatment with a permanent pacemaker. Recent advances that allow real-time 3D mapping of atrial activation have allowed more precise localization of sinus pacemaker cells causing early activation possibly allowing for increased efficacy and safety profile for catheter ablation in the management of IST. We report a case of long-standing IST treated with sinus node modification utilizing St. Jude Medical’s EnSite non-contact mapping and Array catheter, allowing for ablation of three distinct sites of early atrial activation.

Case Description

   A 58-year-old female nurse presents with a greater than 40-year history of intermittent palpitations. Her heart rate (HR) would increase to 150-180 bpm, occasionally with presyncopal symptoms. The symptoms were often nocturnal or coincident with periods of emotional stress. Thyroid tests revealed no abnormalities. At age 20, she underwent an exercise tolerance test with a resting heart rate of 120 that increased to 187 with an upright p wave in the inferior leads throughout. Subsequently she underwent initial electrophysiology study at age 23 where only sinus tachycardia was reported. Trials of medical therapy, including treatment with escalating doses of beta blockers and calcium channel blockers, were ineffective. At the time of our initial evaluation, her atenolol dose had been increased to 300 mg daily with persistent breakthrough symptoms. Trial discontinuation of beta blocker therapy did not alter symptoms. In 2009, the patient underwent two EP studies with ablation of presumed ectopic atrial tachycardia located in the high right atrium with locations near the sinus node, producing improvement but not resolution of her symptoms. Physical exam at all visits was notable for intermittent tachycardia and hypertension. The remainder of her cardiovascular exam was unremarkable. Echocardiogram revealed preserved left ventricular function without evidence of underlying valvular disease. A Holter
monitor placed one month after her second ablation revealed sinus rhythm with average rate of 86 bpm (minimum 67 bpm, maximum 117 bpm) and frequent unifocal atrial ectopy. Her symptoms again worsened, prompting evaluation with repeat EPS, but this time utilizing the EnSite Array catheter (St. Jude Medical, St. Paul, MN).