992-113 The Role of Tilt Table Testing and Neuromonitoring for Optimal Defibrillator Programming

Abstract

Programming of third generation implantable cardioverter defibrillators (ICDs) is usually based on electrophysiologic (EP) testing in the supine position. However, efficacy and tolerance to tiered therapy for ventricular tachycardia (VT) may not be equivalent in the erect position. To test this hypothesis we studied 9 patients ages 36–72 years with implanted ICDs in the supine and erect position on a tilt table. ICDs were programmed to deliver ATP, cardioversion and defibrillation in the ascending order of agressivity for hemodynamically stable VTs. Perfusion was assessed by continuous intraarterial pressure and neuromonitoring techniques capable of assessing beat to beat cerebral perfusion (transcranial Doppler (TCD)), oxygen utilization (near infrared spectroscopy (NIRS)) and neuronal function (quantitative encephalography (QEEG)). 52 episodes of tachyarrhythmias were induced, 30 in the supine and 22 in the erect position. The duration of VT was 12 ± 5 secs in the supine and 17 ± 11 secs in the erect position (p = NS). Adequate perfusion was seen with programmed therapy in all patients in the supine but only in 5/9 patients in the erect position. Abnormal response in 4 patients was characterized by subnormal post-hypotensive hyperemic response < 40% increase in the blood flow velocity post-VT), delta wave slowing on the QEEG, and > 20% increase in NIRS post-hypotensive episode typical of cerebral ischemia. Of these 4 patients, syncope (2) and seizures (2) were experienced in the erect, but not in the supine position during testing. 1) Supine testing may not predict optimal ICD therapy. 2) Neuromonitoring techniques are useful to assess cerebral perfusion during ICD testing. 3) Upright tilt should be considered forroutine ICD testing to optimize programming.