In existing models of alluvial architecture it is typically assumed that mean avulsion frequency is independent of sedimentation rate. However, if avulsion is driven by superelevation of a river bed above its surrounding flood plain, one might expect avulsion rate to increase with sedimentation rate. We have carried out a series of experiments with laboratory-scale fluvial fans in which we measured the frequency of apical avulsions as a function of mean sedimentation rate on the fan. Avulsion frequency increased strongly with increasing sedimentation rate and then stabilized as mass flows began to influence deposition. In the regime of increasing avulsion frequency, the added volume of sediment needed to trigger an avulsion decreased with increasing sedimentation rate. Although our experimental results cannot simply be scaled up to natural rivers, they suggest the possibility of coupling between avulsion frequency and sedimentation rate that would be strong enough to change qualitatively the results of existing models of alluvial architecture. These models should be applied with caution until avulsion mechanics are better understood.

Background-Paroxysmal atrial fibrillation (PAF) can be eliminated with continuous circular lesions (CCLs) around the pulmonary veins (PVs), but it is unclear whether all PVs are completely isolated. Methods and Results-Forty-one patients with symptomatic PAF underwent 3D mapping, and all PV ostia were marked on the 3D map based on venography. Irrigated radiofrequency energy was applied at a distance from the PV ostia guided by 2 Lasso catheters placed within the ipsilateral superior and inferior PVs. The mean radiofrequency duration was 1550Ϯ511 seconds for left-sided PVs and 1512Ϯ506 seconds for right-sided PVs. After isolation, automatic activity was observed in the right-sided PVs in 87.8% and in the left-sided PVs in 80.5%. During the procedure, a spontaneous or induced PV tachycardia (PVT) with a cycle length of 189Ϯ29 ms was observed in 19 patients. During a mean follow-up of 6 months, atrial tachyarrhythmias recurred in 10 patients. Nine patients underwent a repeat procedure. Conduction gaps in the left CCL in 9 patients and in the right CCL in 2 patients were closed during the second procedure. A spontaneous PVT with a cycle length of 212Ϯ44 ms was demonstrated in 7 of 9 patients, even though no PVT had been observed in 6 of these 7 patients during the first procedure. No AF recurred in 39 patients after PV isolation during follow-up. Conclusions-Automatic activity and fast tachycardia within the PVs could reflect an arrhythmogenic substrate in patients with PAF, which could be eliminated by isolating all PVs with CCLs guided by 3D mapping and the double-Lasso technique in the majority of patients.

Background-Atrial tachyarrhythmias (ATa) can recur after continuous circular lesions (CCLs) around the ipsilateral pulmonary veins (PVs) in patients with atrial fibrillation (AF). This study characterizes the electrophysiological findings in patients with and without ATa after complete PV isolation. Methods and Results-Twenty-nine of 100 patients had recurrent ATa after complete PV isolation by use of CCLs during a mean follow-up of Ϸ8 months. A repeat procedure was performed in 26 patients with ATa and in 7 volunteers without ATa at 3 to 4 months after CCLs. No recovered PV conduction was demonstrated in the 7 volunteers, whereas recovered PV conduction was found in 21 patients with recurrent ATa (right-sided PVs in 9 patients and left-sided PVs in 16 patients). The interval from the onset of the P wave to the earliest PV spike was 157Ϯ66 ms in the right-sided PVs and 149Ϯ45 ms in the left-sided PVs. During the procedure, PV tachycardia activated the atrium and resulted in atrial tachycardia (AT) in 10 patients. All conduction gaps were successfully closed with segmental RF ablation. After PV isolation, macroreentrant AT was induced and ablated in 3 patients. In the 5 patients without PV conduction, focal AT in the left atrial roof in 2 patients and non-PV foci in the left atrium in 1 patient were successfully abolished; in the remaining 2 patients, no ablation was performed because of noninducible arrhythmias. During a mean follow-up of Ϸ6 months, 24 patients were free of ATa without antiarrhythmic drugs. Conclusions-In patients with recurrent ATa after CCLs, recovered PV conduction is a dominant finding in Ϸ80% of patients and can be successfully eliminated by segmental RF ablation. Also, mapping and ablation of non-PV arrhythmias can improve clinical success. (Circulation. 2005;111:127-135.)

The treatment of HIV-associated lymphoma has changed since the widespread use of highly active antiretroviral therapy. HIV-infected individuals can tolerate more intensive chemotherapy, as they have better hematologic reserves and fewer infections. This has led to higher response rates in patients with HIV-associated Hodgkin disease (HD) or non-Hodgkin lymphoma (NHL) treated with chemotherapy in conjunction with antiretroviral therapy. However, for patients with refractory or relapsed disease, salvage chemotherapy still offers little chance of long-term survival. In the non-HIV setting, patients with relapsed Hodgkin disease (HD) or non-Hodgkin lymphoma (NHL) have a better chance of long-term remission with high-dose chemotherapy with autologous stem cell rescue (ASCT) compared with conventional salvage chemotherapy. IntroductionThe incidence of Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) in HIV-infected individuals is much greater than in the HIV-negative population. 1,2 In earlier decades the treatment of lymphoma in the setting of immune deficiency was far less successful than in the HIV-negative patient. 3 This was in part due to the poor hematologic reserves of HIV-infected patients but was also due to higher rates of infection and higher rates of relapse of the lymphoma. The advent of highly active antiretroviral therapy (HAART) altered the natural history of HIV infection by reducing the incidence of opportunistic infections and improving the underlying immune deficiency. 4 In addition, combining HAART with chemotherapy or consolidating chemotherapy with HAART has increased remission rates in both HIV-associated Hodgkin and non-Hodgkin lymphoma. 5,6 Recent studies also have confirmed that the International Prognostic Index (IPI) is applicable to patients treated with HAART and chemotherapy. 7 For HIV-infected lymphoma patients with high-risk features as defined by the IPI, relapse rates are still high after conventional chemotherapy. Furthermore, for HIV-infected patients with either relapsed HD or NHL the current salvage chemotherapy regimens offer little chance of long-term survival.In the HIV-negative setting, studies have shown that high-dose therapy with autologous stem cell transplant (ASCT) is the optimal therapy for relapsed HD and NHL. [8][9][10] As the procedure-related mortality of ASCT has decreased, ongoing studies are exploring its use in high-risk first remission patients. 10 Now that HIV-infected individuals have markedly improved immune and hematologic function, the use of both solid organ and ASCT is being explored in patients with underlying immunodeficiency and concomitant malignancy or organ dysfunction. 11-15 Herein we report the City of Hope Comprehensive Cancer Center experience on the largest single institution series of patients with HIV-associated lymphomas undergoing ASCT. Our initial experience demonstrated the feasibility of this approach in terms of stem cell mobilization, engraftment, and low regimen-related toxicity. 16 Now with long-term follow-up in a larger ser...

Long-term survival and improved neuropsychological function have occurred in selected children with Hurler syndrome (MPS I H) after successful engraftment with genotypically matched sibling bons marrow transplantation (BMT). However, because few children have HLA-identical siblings, the feasibility of unrelated donor (URD) BMT as a vehicle for adoptive enzyme therapy was evaluated in this retrospective study. Forty consecutive children (median, 1.7 years; range, 0.9 to 3.2 years) with MPS I H received high-dose chemotherapy with or without radiation followed by BMT between January 27, 1989 and May 13, 1994. Twenty-five of the 40 patients initially engrafted. An estimated 49% of patients are alive at 2 years, 63% alloengrafted and 37% autoengrafted. The probability of grade II to IV acute graft-versus-host disease (GVHD) was 30%, and the probability of extensive chronic GVHD was 18%. Eleven patients received a second URD BMT because of graft rejection or failure. Of the 20 survivors, 13 children have complete donor engraftment, two children have mixed chimeric grafts, and five children have autologous marrow recovery. The BM cell dose was correlated with both donor engraftment and survival. Thirteen of 27 evaluable patients were engrafted at 1 year following URD BMT. Neither T-lymphocyte depletion (TLD) of the bone marrow nor irradiation appeared to influence the likelihood of engraftment. Ten of 16 patients alive at 1 year who received a BM cell dose greater than or equal to 3.5 x 10(8) cells/kg engrafted, and 62% are estimated to be alive at 3 years. In contrast, only 3 of 11 patients receiving less than 3.5 x 10(8) cells/kg engrafted, and 24% are estimated to be alive at 3 years (P = .05). The mental developmental index (MDI) was assessed before BMT. Both baseline and post-BMT neuropsychological data were available for 11 engrafted survivors. Eight children with a baseline MDI greater than 70 have undergone URD BMT (median age, 1.5 years; range, 1.0 to 2.4 years). Of these, two children have had BMT too recently for developmental follow-up. Of the remaining six, none has shown any decline in age equivalent scores. Four children are acquiring skills at a pace equal to or slightly below their same age peers; two children have shown a plateau in learning or extreme slowing in their learning process. For children with a baseline MDI less than 70 (median age, 2.5 years; range, 0.9 to 2.9 years), post-BMT follow-up indicated that two children have shown deterioration in their developmental skills. The remaining three children are maintaining their skills and are adding to them at a highly variable rate. We conclude that MPS I H patients with a baseline MDI greater than 70 who are engrafted survivors following URD BMT can achieve a favorable long-term outcome and improved cognitive function. Future protocols must address the high risk of graft rejection or failure and the impact of GVHD in this patient population.

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Adding 90Y ibritumomab tiuxetan to high-dose BEAM with autologous stem-cell transplantation is feasible and has a toxicity and tolerability profile similar to that observed with BEAM alone. Rates of progression-free survival seen in these patients are promising and warrant additional study.

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