A Novel Method for Sinus Node Modification and Phrenic Nerve Protection in Resistant Cases

JASON C. RUBENSTEIN, MICHAEL H. KIM, JASON T. JACOBSON
2009 Cardiovascular Electrophysiology  
Endocardial Catheter for IST Ablation. This is a case report of inappropriate sinus tachycardia in a patient who had a previous unsuccessful endocardial ablation, which had been limited due to concerns of phrenic nerve injury. The patient required a repeat ablation that utilized a novel combined epicardial and endocardial approach for sinus node modification and simultaneous protection of the phrenic nerve via an epicardial balloon. (J Cardiovasc Electrophysiol, Vol. 20, pp. 689-691, June 2009)
more » ... inappropriate sinus tachycardia, epicardial, ablation, phrenic nerve Case Report A 33-year-old female presented with previous diagnosis of noncompaction of the left ventricle, who had a dual chamber implantable cardioverter-defibrillator (ICD) placed many years ago for primary prevention of sudden cardiac death. Since that time, she has been repeatedly symptomatic of tachycardia. Initially, she had typical right atrial flutter diagnosed and had a successful cavotricuspid isthmus ablation. Recurrent symptomatic tachycardia, and occasional syncope, led to an empiric slow pathway modification due to the presence of dual pathways and typical atrioventricular (AV) nodal echoes, but she had no inducible supraventricular tachycardia. During this study, a heart rate increase of 25 beats per minute (bpm) was seen after a 1 μg i.v. bolus dose of isoproterenol, which was suggestive but not diagnostic of the diagnosis of inappropriate sinus tachycardia (IST). 1 All other potential causes of sinus tachycardia were excluded, and the clinical scenario was felt to be most consistent with IST. The patient also has a long history of multiple syncopal events and a tilt-table test consistent with vasovagal syncope. Recurrent syncope after ICD implantation occurred without any arrhythmic events except sinus tachycardia. The treatment for her IST was limited by baseline hypotension made worse by beta-blockers. The addition of low-dose calcium channel blockers was not tolerated. Because of the history of cardiomyopathy, fludrocortisone and midodrine were not prescribed. An attempt at endocardial sinus node modification was made using a noncontact array (NavX Array; St. Jude Medical, St. Paul, MN, USA). Escalating the doses of isoproterenol increased the sinus rate but did not change the site of earliest activation by more than a few millimeters. Lesions were delivered using an internally irrigated RF ablation catheter (Chilli; Boston Scientific, Natick, MA, USA), but it was limited by phrenic nerve capture at optimal ablation sites. Several of these sites had to be ablated with a 6-mm cryotherapy catheter (CryoCath, Montreal, Quebec) during phrenic nerve pacing from a quadripolar catheter in the superior vena cava. There was only a modest effect on the P-wave amplitude and resting sinus rate. Within a few weeks, she had recurrent severe symptoms and extreme hypotension, limiting medical therapies. Examination of her ICD
doi:10.1111/j.1540-8167.2008.01383.x pmid:19207755 fatcat:mtz64wfkizcdzd36tkgmqg475i