Experience and Implantation Techniques with a New Single-Pass Lead VDD Pacing System

Thirty-six patients were implanted with a single-lead atrial-synchronous ventricular pacing (VDD) system at our center in the first and second phases of a clinical trial between October 1987 and December 1989. The clinical system comprised a pulse generator in conjunction with a pacing lead incorporating two diagonal atrial bipolar (DAB) electrodes designed to lie in the mid-to upper-right atrium and a distal tip electrode for ventricular pacing and sensing. Twenty five of the patients had complete heart block, ten had second-degree block, and one had AV nodal block. A modified Bruce protocol limiting treadmill speed to 1.7 miles per hour was used to establish sinus node competency as evidenced by sustained sinus rate increase in a more-or-less linear fashion. The mean acute P wave amplitude measured at implant was 1.66 mV +/- 1.04 SD; the mean P wave amplitude (minimum and maximum, both sitting and supine) for all patients at all follow-up (N = 420) was 1.54 mV +/- 0.9 SD. The follow-up interval for all patients ranged from a minimum of 13 days and a maximum of 762 days, with a mean of 261 +/- 206 days as of December 1, 1989. Four dislodgments of the ventricular electrode occurred with the more pliable of two passive fixation mechanisms used on the lead; atrial sensing remained intact at all times with both fixation systems. Changes in atrial sensing threshold were quite frequent during the early follow-up visits due to electrode movement in the right atrium; however, adequate ventricular tracking of the atrial rate was achieved in all cases once the threshold values were established initially, even though several patients required atrial sensing of 0.2 mV at some of the follow-up visits. Two patients presented with pacemaker-mediated tachycardia associated with retrograde conduction, which was resolved with reprogramming; they are presently maintaining atrial synchrony in the VDD mode. Successful single-lead VDD pacing with consistent P wave sensing has been achieved with this atrial rate responsive system.     

Effect of Equilibration Zones on Stability, Uniformity, and Homogeneity Profiles of Vapors and Aerosols in the ADG Nose-Only Inhalation Exposure System

Effect of Equilibration Zones on Stability, Uniformity, andHomogeneity Profiles of Vapors and Aerosols in the ADG Nose-OnlyInhalation Exposure System. GREEN, J. D., HELKE, W. F., SCOTT,J. B., YAU, E. T., TRAINA, V. M., AND DIENER, R. M. (1984).Fundam. Appl. Toxicoi. 4, 768–777. A commercially available,inexpensive, nose-only exposure chamber was modified to includeremovable equilibration zones, and the effect of these zoneson chamber performance was determined. Since limited performancedata were available concerning this unit, a more extensive characterizationwas performed. EPA limit concentrations (5 mg/liter) of toluenevapor or corn oil aerosol, and relatively low concentrationsof uranine aerosol (50 pg/liter) were produced by standard techniques.The presence or absence of equilibration zones did not affectthe stability or uniformity of toluene vapor atmospheres, withthe coefficient of variation (CV) not exceeding 3.33% in allexperiments. In contrast, the presence of two equilibrationzones was found to progressively enhance the uniformity of theinhalable test aerosols in the animal exposure zone (CV 3.16%).Matrix sampling revealed that in both uranine and corn oil experiments,the center matrix point concentration was consistently lowerthan samples taken in the actual animal breathing zone. Equilibrationzones markedly reduced the difference between breathing zoneand center point concentrations. These performance data indicatedthat the modified ADG nose-only exposure system performed exceptionallywell with the materials that were studied. Results were comparableto those describing whole-body chamber performance. The readyavailability of this inexpensive prototype lends itself to standardizationof techniques between laboratories     

THE EFFECTS OF COCAINE AND LIGNOCAINE ON THE RAT RIGHT VENTRICLE IN VITRO

• 1 The effects of cocaine and lignocaine on the contractile responses to field stimulation and to exogenously applied agents, in the absence of other stimuli, have been investigated in the rat right ventricle using methods we have recently described (Doggrell & Vincent, 1981a). In addition the effects of ³H accumulation from (?)-[³H]-noradrenaline and on the spontaneous and field stimulation-induced overflow of ³H, following preloading of the tissue with (?)-[³H]-noradrenaline, are reported.
• 2 Cocaine, but not lignocaine, inhibited the accumulation of ³H from (?)-[³H]-noradrenaline. The spontaneous overflow of ³H, following preloading of the tissue with (?)-[³H]-noradrenaline was not altered by cocaine, 10μ, or lignocaine, 100μM. 10μM Lignocaine had no effect on the overflow of ³H evoked by field stimulation at 5Hz. Lignocaine, 100μM, increased and cocaine, 1 and 10μM, reduced the decline in evoked release of ³H. This effect of lignocaine probably represents a decrease in nerve excitability and that of cocaine inhibition of neuronal uptake of noradrenaline.
• 3 Cocaine, μM, reduced the rate of beat response to tyramine, 1μM, alone, probably by inhibiting the neuronal uptake process.
• 4 Cocaine, 1 and 10μM, had no effect on the contractile responses to field stimulation (at 2 and/or 5Hz). The rate of beat to (?)-noradrenaline or (?)-isoprenaline, 1μM, alone was decreased by cocaine, 10μM. Lignocaine, 10μM, reduced the force of contractions to field stimulation at 5 Hz and the responses to (?)-noradrenaline or (?)-isoprenaline alone. It is suggested that the inhibitory effects of cocaine and lignocaine on responses to (?)-isoprenaline in the rat right ventricle are due to a decreased postjunctional membrane excitability. The inability of 10μM cocaine to potentiate contractile responses to endogenous or exogenous (?)-noradrenaline as a consequence of the inhibition of neuronal uptake is also probably due in part to decreased post-junctional excitability of the right ventricle.

     

THE INTRAVENTRICULAR RESERVOIR IN THE TREATMENT OF NEUROLOGICAL DISEASE SECONDARY TO HEMATOLOGICAL MALIGNANCY: AN EIGHT YEAR EXPERIENCE

Abstract Between 1974 and 1982, 17 patients with central nervous system disease secondary to hematological malignancy had an intraventricular reservoir inserted to monitor their disease and to instil cytotoxic chemotherapy. Two other patients with acute lympho-blastic leukemia and difficult access to the cerebrospinal fluid had a reservoir inserted to facilitate intrathecal chemotherapy. All 17 patients with established disease showed clinical improvement. Thirteen patients had complete elimination of malignant cells from the cerebrospinal fluid with cytotoxic chemotherapy, and the other four had a reduction in the concentration of malignant cells. Infection and neurotoxicity were found in a significant number of cases. and therefore the good clinical resDonse associated with th; procedure must be weighed carefully against the associated toxicity.     

Feasibility of Electroporation for the Creation of Pulmonary Vein Ostial Lesions

Feasibility of Electroporation . Introduction: There is an obvious need for a better energy source for pulmonary vein (PV) antrum isolation. Objective: We investigated the feasibility and safety of electroporation for the creation of PV ostial lesions. Methods: After transseptal puncture, a custom 7F decapolar 20 mm circular ablation catheter was placed in the PV ostia of 10 pigs. Ablation was performed with a nonarcing, 200 J application delivered between the catheter and an indifferent patch electrode on the lower back. A single pulse was applied for each catheter position, with a maximum of 4 per ostium. Local PV electrogram amplitude and stimulation threshold were measured at multiple locations in both ostia before and directly after ablation, and after 3 weeks survival, using a regular 4 mm mapping catheter. All PV ostia were sectioned, stained, and histologically investigated. Results: The 3‐week survival period was uneventful. PV ostial electrogram amplitude decreased and stimulation threshold increased significantly in most ostia. PV angiograms did not show any stenosis during this short follow‐up. Histologically, up to 3.5‐mm‐deep lesions were found. Conclusion: Data suggest that electroporation can safely be used to create lesions in a sensitive environment like PV ostia. (J Cardiovasc Electrophysiol, Vol. 22, pp. 302‐309, March 2011)     

Transvenous Intramyocardial Cellular Delivery Increases Retention in Comparison to Intracoronary Delivery in a Porcine Model of Acute Myocardial Infarction

Background: Clinical trials using intracoronary (IC) delivery of cells have addressed efficacy but the optimal delivery technique is unknown. Our study aimed to determine whether transvenous intramyocardial (TVIM) approach was advantageous for cellular retention in AMI. Methods: Domestic pigs (n = 4) underwent catheterization with coronary angiography and ventriculography prior to infarction and pre‐ and post‐cells. Pigs underwent 90‐minute balloon occlusion of the left anterior descending artery (LAD). After one week they were prepared for IC (n = 2) or TVIM (n = 2) delivery of bone marrow mononuclear cells (MNC) labeled with GFP. IC infusion used an over‐the‐wire catheter to engage the LAD and balloon inflation to prevent retrograde flow. Venography via the coronary sinus was used for TVIM delivery. The anterior interventricular vein was engaged with a guidewire allowing use of the TransAccess? catheter that is outfitted with an ultrasound tip for visualization. Animals were sacrificed one hour after delivery and tissue was analyzed. Results: Procedures were performed without complication and monitoring was uneventful. 1 × 10⁸ MNC were isolated from each bone marrow (BM) preparation and 1 × 10⁷ MNC delivered. Ventriculography at one week revealed wall motion abnormalities consistent with an anterior AMI. TVIM and IC delivery revealed mean 452 cells per section and 235 cells per section on average, respectively, in the infarct zone (P = 0.01). Conclusion: We have demonstrated that TVIM approach for cell delivery is feasible and safe. Moreover, this approach may provide an advantage over IC infusion in retention of the cellular product; however, larger studies will be necessary.