A New Temporary Occlusion and Aspiration System for Prevention of Distal Embolization During Percutaneous Transluminal Renal Angioplasty

Cholesterol embolization has been described as a severe complication of percutaneous transluminal renal angioplasty (PTRA) and may lead to renal insufficiency with the need of transient or permanent hemodialysis. We describe a case of successful angioplasty of a renal artery in-stent restenosis utilizing a new temporary balloon occlusion and aspiration system for prevention of distal embolization. Histological examination of blood retrieved from the distally occluded vessel showed lipid-rich macrophages (foam cells) and an amorphic lipoid substance as markers of atherosclerotic plaque debris. Further studies are necessary to evaluate the clinical relevance of atheromatous microembolization and its renal function and clinical course following angioplasty.     

Importance of an Individually Programmed Atrioventricular Delay at Rest and on Work Capacity in Patients with Dual Chamber Pacemakers

Despite higher costs, expenditure, and the necessity of repeatedly reprogramming of dual chamber pacemakers, they are increasingly implanted to achieve an optimal work capacity. The influence of an individually programmed atrioventricular (AV) delay hetween 100–250 msec on physical work capacity in 12 patients (68 ± 16 years) with dual chamher pacemakers implanted for high degree AV block was studied. During radionuclide ventriculography at rest the "optimal AV delay" with the maximal achieved left ventricular ejection fraction and the "most unfavorable AV delay" with the least achieved ejection fraction were determined. The ejection fraction at rest with the "optimal AV delay" was 5t ±14% and with the "most unfavorable AV delay" 45 ± 15% (P < 0.001). In random order each patient was assigned to either AV delay and a spiroergometry was performed to determine maximum oxygen uptake (max VO₂). which correlates best with work capacity, at a respiratory quotient of 1.1. The results show neither a difference in maximum oxygen uptake (1,262 ± 446 mUmin with the optimal AV delay, 1,248 ± 400 mL/min with the most unfavorable AV delay, respectively) nor in heart rate, blood pressure, exercise duration, maximal workload, and minute ventilation. Thus, an individually programmed AV delay affects left ventricular ejection fraction at rest. In contrast, an individually programmed A V delay has no influence on physical work capacity in patients with a dual chamber pacemaker.     

Cryoballoon Pulmonary Vein Isolation with Real-Time Recordings from the Pulmonary Veins

Introduction: Cryoballoon (CB) ablation represents a novel technology for pulmonary vein isolation (PVI). We investigated feasibility and safety of CB-PVI, utilizing a novel spiral catheter (SC), thereby obtaining real-time PV potential registration.
Methods: Following double transseptal puncture, a Lasso catheter (Biosense Webster, Diamond Bar, CA, USA) and the 28 mm CB were positioned within the left atrium. A novel SC (Promap, ProRhythm Inc., Ronkonkoma, NY, USA) was inserted through the lumen of the CB allowing PV signal registration during treatment. Time to PV conduction block was analyzed. If no stable balloon position was obtained, the SC was exchanged for a regular guide wire and PV conduction was assessed after treatment by Lasso catheter.
Results: In 18 patients, 39 of 72 PVs (54%) were successfully isolated using the SC. The remaining 33 PVs were isolated switching to the regular guide wire. Time to PV conduction block was significantly shorter in PVs in which sustained PVI was achieved as compared to PVs in which PV conduction recovered within 30 minutes (33 ± 21 seconds vs 99 ± 65 seconds). In 40 PVs, time to PV conduction block was not obtained because of: (1) PVI not being achieved during initial treatment; (2) a distal position of the SC; or (3) isolation with regular guide wire. No procedural complications occurred.
Conclusion: Visualization of real-time PV conduction during CB PVI is safe, feasible, and allows accurate timing of PVI onset in a subset of PVs. Time to PV conduction block predicts sustained PVI. However, mechanical properties of the SC need to be improved to further simplify CB PVI.     

GLIAL CELL INTERACTIONS WITH TENASCIN-C: ADHESION AND REPULSION TO DIFFERENT TENASCIN-C DOMAINS IS CELL TYPE RELATED

The multimodular glycoprotein tenascin-C is transiently expressed, predominantly by glial cells, during the development of the central and peripheral nervous systems. This extracellular matrix glycoprotein is involved in the control of cell adhesion, neuron migration and neurite outgrowth. Distinct functional properties for neuronal cell types have been attributed to separate tenascin-C domains using antibody perturbation studies and in vitro experiments on tenascin-C fragments. In order to study potential roles of tenascin-C for glial cell biology, a library of recombinant tenascin-C domains was used in a bioassay in vitro. Embryonic day 14 astrocytes, various astroglial-derived cell lines (C6, A7 and Neu7) and oligodendroglial-derived cell types (Oli-neu and G26-20) were examined in an adhesion assay and compared to the neuroblastoma cell line N2A. A binding site for most cell types, except for A7 and N2A, could be assigned to the first three fibronectin type III domains. Repulsive properties could be mapped to three different sites, the epidermal growth factor-like repeats, fibronectin type III repeats 4 and 5 and to the alternatively spliced region of the molecule. The responses to these repulsive sites varied according to the cell type. These data are consistent with the interpretation that different cell types express distinct sets of tenascin-C receptors which might regulate cellular responses via distinct second messenger pathways. Copyright © 1996 ISDN. Published by Elsevier Science Ltd.     

Is Atrial Sensing of Ventricular Far-Field Signals Important in Single-Lead VDD Pacing?

In single-lead VDD pacing the atrial sensitivity frequently is programmed to sensitive values. Atrial sensing of ventricular far-field signals should be reduced by differential atrial sensing. The aim of the study was to evaluate the effectiveness of this approach. Methods: The study included 10 patients with a single-lead VDD pacemaker (Thera 8948, Lead 5032). The atrial sensitivity was set to its most sensitive value of 0.18 mV and the telemetered intraatrial EGM was continuously recorded. After atrial tracked ventricular pacing, VVI pacing was performed with pacing rates from 100 to 160 beats/min in steps of 10 beats/min and up to 165 beats/min. The peak-to-peak amplitudes of P waves (P) and ventricular far-field signals (VFFS) were measured from the recordings. The ratio P/VFFS that defines the atrial signal-to-noise ratio was calculated, and the time from stimulus to maximum of the far-field signals amplitude (Tmax) was measured. Results: P measured 0.98 ± 0.76 mV. A VFFS was visible in the atrial channel in all patients with an amplitude of 0.45 ± 0.25 mV (range 0.01–1.0 mV), independent of the pacing rate. The ratio P/VFFS was 3.9 ± 4.2 (range 0.9–21.0). Tmax measured 99.4 ± 15.2 ms during sinus rhythm. A rate dependent shortening of Tmax to 92.7 ± 11.2 ms at 140 beats/min was observed (P = 0.001). At rates above 140 beats/min no further shortening occurred. Conclusion: Ventricular far-field signals are measurable in the atrial channel of VDD systems and may reach considerable amplitudes, which are not rate dependent. Although differential sensing provides favorable P waves to ventricular far-field signal ratios, refractory periods are needed to avoid far-field sensing. The rate dependent shortening of the ventricular signal can be detected in the atrial channel in VDD pacing.     

Carcinoma of the Breast and Pacemaker Generators

A 90-yearold woman developed intraductol adenocarcinoma (TNM classification pT2, G2) of the left breast 18 years after initial pacemaker implantation deep to the left breast. There was no evidence of local or distant metastasis and she was treated with local excision and tamoxifen.     

Assessing Acute Ventricular Volume Changes by Intracardiac Impedance in a Chronic Heart Failure Animal Model

Background: Implantable device diagnostics may play an essential role in simplifying the care of heart failure patients by providing fundamental insights into their complex clinical patterns. Early recognition of heart failure progression by a continuous hemodynamic monitoring would allow for timely therapeutic interventions to prevent decompensation and hospitalization. In this study, the feasibility of assessing ventricular volume changes by implant-based measurements of intracardiac impedance was tested in a heart failure animal model.
Methods: Heart failure was induced in five minipigs by high-rate pacing over 3 weeks. During a final open-chest examination a graded dobutamine stress test was performed. Stroke volume (SV) was measured by an ultrasonic flow probe at the ascending aorta. End diastolic pressure (EDP) and maximum pressure slope (dP/dt_max) were calculated from a left ventricular microtip catheter signal. Impedance was measured by an implanted pacemaker between biventricular leads. Stroke impedance (SZ) was calculated as the difference between end-systolic and end-diastolic impedance (EDZ).
Results: Administration of dobutamine led to an increase in SV (55 ± 16%), dP/dt_max (107 ± 89%), and SZ (56 ± 30%). EDP changed by 37 ± 21% whereas EDZ changed by 7.4 ± 4%. Significant correlations were found between SZ and SV (r = 0.88), and between EDZ and EDP (r =−0.82).
Conclusion: The strong correlation with SV allows the application of intracardiac impedance measurements for an implant-based continuous monitoring of cardiac function. Impedance may also be used for hemodynamic optimization of cardiac resynchronization therapy.