HEAD-UP TILT TESTING PREDICTS SYNCOPE DURING VENTRICULAR-TACHYCARDIA IN IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR PATIENTS

Implantable cardioverter defibrillator (ICD) programming is usually ba sed on results of supine electrophysiological (EP) testing. However, E P testing does not provide any information about tolerance to ICD ther apy in the upright posture. We hypothesized that in addition to the ar rhythmia duration and ventricular tachycardia (VT) cycle length, cereb ral perfusion may play a role in determining tolerance to tiered (CD t herapy. Transcranial Doppler (TCD) and cerebral venous oxygen saturati on (rCVOS) are relatively new noninvasive techniques that may be used to assess dynamic changes in cerebral blood flow and metabolism during VT. Sixteen patients with pace-terminable VT and ICDs underwent supin e (S) and upright tilt (HUT) ICD testing in conjunction with TCD and r CVOS monitoring. ICDs were programmed to deliver antitachycardia pacin g, cardioversion, and defibrillation for VT, in the ascending order of aggressivity. Despite no significant differences in the induced VT cy cle length (320 +/- 100 msec, S, vs 330 +/- 90 msec, HUT) and VT durat ion (14.6 +/- 6.7 sec, S, vs 17 +/- 9.2 sec, HUT), cerebral perfusion was more significant impared during HUT (21 +/- 10 [S] vs 29 +/- 7% de crease from baseline [HUT], P < 0.001), and rCVOS decreased from basel ine (5 +/- 6 [S] vs 10 +/- 6 [HUT] %, P < 0.001). Five of 16 patients experienced syncope during HUT and none during supine testing. At I-ye ar follow-up five patients who experienced syncope during HUT experien ced at least one episode of syncope, whereas none not so identified di d We conclude that: (1) Supine ICD testing is insufficient to predict individual patient tolerance to ICD therapy; (2) HUT testing predicts tolerance to ICD therapy; and (3) noninvasive neuromonitoring techniqu es are useful for assessment of cerebral blood flow and metabolism dur ing ICD testing. (J Interven Cardiol 1998; 11:205-211).