Disappearance of orthostatic hypotension after pacemaker implantation in a patient with a long PR interval.

Orthostatic hypotension is the fall in blood pressure when upright and has a high prevalence in elderly population. Diagnostic and therapeutic work-up can be long and difficult. We describe the case of an 81-year-old male patient with long PR interval and episodes of 2:1 atrioventricular block, in whom the implantation of a dual chamber pacemaker led to the disappearance of orthostatic hypotension. The most likely mechanism was an impaired cardiac filling with a short diastolic time due to a very prolonged PR interval, a somewhat "pseudo-pacemaker syndrome". The correction of the first degree AV block with the implantation of the pacemaker and the optimization of the AV delay allowed us to correct the diastolic impairment and to resume a normal response to orthostatism. This case underlies the complex and multifactorial nature of orthostatic hypotension and the importance of a correct diagnosis of correctable causes to treat a very disabling condition.

Externalized conductors and insulation failure in Biotronik defibrillator leads: History repeating or a false alarm?

Conductor externalization and insulation failure are frequent complications with the recalled St. Jude Medical Riata implantable cardioverter-defibrillator (ICD) leads. Conductor externalization is a "unique" failure mechanism: Cables externalize through the insulation ("inside-out" abrasion) and appear outside the lead body. Recently, single reports described a similar failure also for Biotronik leads. Moreover, some studies reported a high rate of electrical dysfunction (not only insulation failure) with Biotronik Linox leads and a reduced survival rate in comparison with the competitors. In this paper we describe the case of a patient with a Biotronik Kentrox ICD lead presenting with signs of insulation failure and conductor externalization at fluoroscopy. Due to the high risk of extraction we decided to implant a new lead, abandoning the damaged one; lead reimplant was uneventful. Subsequently, we review currently available literature about Biotronik Kentrox and Linox ICD lead failure and in particular externalized conductors. Some single-center studies and a non-prospective registry reported a survival rate between 88% and 91% at 5 years for Linox leads, significantly worse than that of other manufacturers. However, the preliminary results of two ongoing multicenter, prospective registries (GALAXY and CELESTIAL) showed 96% survival rate at 5 years after implant, well within industry standards. Ongoing data collection is needed to confirm longer-term performance of this family of ICD leads.

Riata silicone defibrillation lead with normal electrical measures at routine ambulatory check: The role of high-voltage shock testing.

AIM: To describe our experience with shock testing for the evaluation of patients with Riata™ leads. METHODS: Among 51 patients with normal baseline electrical parameters, 20 died during follow-up. Of the remaining 31 patients, 15 underwent the test: In 10 cases a defibrillation testing with ventricular fibrillation (VF) induction and in 5 cases a R-wave-synchronized shock (> 20 J, without inducing VF). The test was performed under sedation with Midazolam. RESULTS: Twelve patients (80%) had a normal behavior during shock testing: In 8 cases induced VF was correctly detected and treated; in 4 cases of R-wave-synchronized shock electrical parameters remained stable and normal. Three patients (20%) failed the test. One patient with externalized conductors showed a sudden drop of high-voltage impedance (< 10 Ohm) after a 25 J R-wave-synchronized shock. Two other patients with externalized conductors, undergoing defibrillation testing, showed a short-circuit during shock delivery and the implantable cardioverter defibrillator was unable to interrupt VF. CONCLUSION: In Riata™ leads the delivery of a low current during routine measurement of high-voltage impedance may not reveal a small short circuit, that can only be evident by attempting to deliver a true shock, either for spontaneous arrhythmias or in the context of a shock testing.