Impact of Dual Chamber Pacing on the Incidence of Atrial and Ventricular Tachyarrhythmias in Recipients of Implantable Cardioverter Defibrillators

Recent observations suggest that frequent dual-chamber pacing in recipients of implantable cardioverter defibrillators (ICD) may adversely influence clinical outcomes. This prospective, multicenter study examined the relationship between the frequency of atrial (%AP) and ventricular pacing (%VP) and the incidence of atrial (AT) and/or ventricular tachyarrhythmias (VT) in a standard ICD population. A total of 141 consecutive patients with primary and secondary ICD indications were studied. Continuous arrhythmia detection with a dual-chamber ICD revealed paroxysmal AT in 60 (43%) and VT in 72 (51%) patients within 6 months of device implantation. Far-field oversensing of ventricular signals occurred in 13% of all "atrial tachy response" mode switches. Without adjustment for covariates, a higher %AP was associated with an increased incidence of AT (P < 0.05). However, this association remained only weakly significant after adjustment for covariates using a multivariate model. High New York heart failure functional classes correlated significantly with AT (P = 0.02) and VT (P = 0.007). Rate-modulated pacing, programmed in 1/3 of patients, correlated with occurrence of AT (P = 0.006), but not with occurrence of VT. With respect to dual-chamber pacing, a %AP ≥ 48% combined with a %VP > 40% was associated with an increased probability for VT. In conclusion, AT and VT occurred frequently within 6 months after dual-chamber ICD implantation. High rates of DDD/R stimulation were associated with a trend toward higher incidence of AT, VT, or both.     

Effects of Different Re-Wetting Techniques on Dentin Shear Bond Strengths

Purpose: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid‐etching. The purpose of this study was to compare the dentin shear bond strengths of two single‐bottle adhesives (one acetone‐based and one ethanol‐based) applied under different etched‐dentin conditions: dry, wet, or dry and re‐wetted with different solutions. Materials and Methods: Bovine incisors (N = 120) were mounted in acrylic, polished to 600‐grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot‐dried, air‐dried, or air‐dried and re‐wetted with different solutions (distilled water, Gluma Desensitizer, Aqua‐Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light‐cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. Results: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re‐wetted with Gluma Desensitizer, re‐wetted with Aqua‐Prep, or never dried. Differences between these surface conditions were not statistically significant for either material. CLINICAL SIGNIFICANCE Different dentin surface conditions and re‐wetting techniques affected bond strengths for adhesives studied. Aqua‐Prep and Gluma Desensitizer can be successfully used as re‐wetting agents. The use of a re‐wetting agent may be beneficial when dentin is dried after acid‐etching and rinsing.     

Randomized Comparison of Multipolar,Duty‐Cycled,Bipolar‐Unipolar Radiofrequency Versus Conventional Catheter Ablation for Treatment of Common Atrial Flutter

Comparison of Radiofrequency Versus Conventional Catheter Ablation. Introduction: Radiofrequency (RF) catheter ablation has been established as an effective and curative treatment for atrial flutter (AFL). Approved methods include a drag‐and‐drop method, as well as a point‐by‐point ablation technique. The aim of this study was to compare the acute efficacy and procedural efficiency of a multipolar linear ablation catheter with simultaneous energy delivery to multiple catheter electrodes against conventional RF for treatment of AFL. Methods: Patients presenting to our department with symptomatic, typical AFL were enrolled consecutively and randomized to conventional RF ablation with an 8‐mm tip catheter (ConvRF) or a duty‐cycled, bipolar‐unipolar RF generator delivering power to a hexapolar tip‐versatile ablation catheter (T‐VAC) group. For both groups, the procedural endpoint was bidirectional cavotricuspid isthmus block. Results: Sixty patients were enrolled, 30 patients each assigned to ConvRF and T‐VAC groups. Total procedure time (40.2 ± 15.8 min vs 60.5 ± 12.7 min), energy delivery time (8.5 ± 3.7 min vs 14.7 ± 5.2 min), radiation dose (14.5 ± 3.5 cGy/cm² vs 31.7 ± 12.1 cGy/cm²), and the minimum number of RF applications needed to achieve block (4.2 ± 2.4 vs 8.9 ± 7.2) were significantly lower in the T‐VAC group. In 7 patients treated with the T‐VAC catheter, bidirectional block was achieved with less than 3 RF applications, versus no patients with conventional RF energy delivery. Conclusion: The treatment of typical AFL using a hexapolar catheter with a multipolar, duty‐cycled, bipolar‐unipolar RF generator offers comparable effectiveness relative to conventional RF while providing improved procedural efficiency. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1109‐1113)     

Medical evacuations from the region of former Yugoslavia: The experience of 2 years

In September 1992, the International Organization for Migration(IOM), an intergovernmental humanitarian organization basedin Geneva, Switzerland, implemented the special medical programme(SMP) for the medical evacuation of war victims in former Yugoslavia.For inclusion into the SMP, patients must be victims of war,suffer from a serious medical condition with a favourable prognosis,not treatable locally, be stable enough to survive air traveland withstand delay between medical documentation and actualevacuation. As of August 1994,1,484 patients In need of secondarytreatment not locally available were evacuated to hospitalsin 31 countries. Most patients suffered from fractures, amputationsand nerve injuries. Seventy-two per cent originated from Bosnia-Herzegovina.This paper discusses various problems encountered, such as bureaucraticobstacles, ongoing armed conflict hampering humanitarian activities,lack of funding and the effects of the sustained media attention.     

Prenatal diagnosis of congenital mesoblastic nephroma associated with renal hypertension in a premature child

In the present article, we report, for the first time, a prenatal diagnosis of a congenital mesoblastic nephroma in combination with a post-partum hyperreninemia with hypertension. A newborn was delivered at 35 weeks gestation who had an intrauterine diagnosis of a renal mass as early as 32 weeks gestational age by ultrasound examination. Tumor nephrectomy was performed on day 11 after delivery when an increase in hypertension was observed in the newborn.     

Fundamental Considerations in Pacing of the Diaphragm for Chronic Ventilatory Insufficiency: A Multi-Center Study

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results fom the Center group yielded information on the early experience with diaphragm pacing important to its future application.     

Esophageal Acid Levels after Pulmonary Vein Isolation for Atrial Fibrillation

Background: Pulmonary vein antrum isolation (PVAI) is a potentially curative, nonpharmacologic treatment of atrial fibrillation (AF). Several procedural complications have been described, including esophageal wall lesions ranging from erythema and esophagitis, necrosis and ulcer, to atrio-esophageal fistula. We prospectively studied changes in esophageal acid levels before and after PVAI.
Methods: We performed 24-hour pH-metry before and 1.3 ± 1.6 days after PVAI, in 25 patients (mean age = 62 ± 12 years, 17 men) with symptomatic AF. A 2-mm transnasal probe was inserted into the inferior part of the esophagus and into the stomach to measure pH levels at fixed intervals. DeMeester scores, indicating acidic gastro-esophageal reflux, were calculated.
Results: The mean number of reflux episodes increased from 89 ± 80 before to 107 ± 94 after PVAI. The mean percentage of time with esophageal pH < 4 was shorter after (108 ± 193 minutes) than before PVAI (159 ± 245 minutes). The mean DeMeester score decreased from 49 ± 68 before to 31 ± 41 after PVAI (P < 0.05). We observed erythema or esophagitis in five patients, necrosis or ulcer in seven, and atrio-esophageal fistula in no patient.
Conclusions: Our hypothesis of increased acid levels caused by stimulation of the right vagal nerve during isolation of the right upper pulmonary vein was not verified.