[Long-term survival of patients with severe aortic stenosis undergoing transcatheter aortic valve implantation]

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is an effective and safe option for low, medium and high-risk patients with severe aortic stenosis (SAS).

AIM

To analyze the clinical results and long-term survival of TAVI in our center.

MATERIAL AND METHODS

Prospective analysis of 53 patients aged 73 ± 10 years with a Society of Thoracic Surgeons (STS) score of 7.3 ± 3.9%.

RESULTS

In 96% a transfemoral access was used and, in most patients, ProGlides™ as vascular closure device was used. General anesthesia and conscious sedation were used in 79 and 21% of cases, respectively. Fifty-three valves were implanted, 42 self-expandable (SEV) and 11 balloon-expandable (Edwards Sapiens). The implant was successful in 49 patients (92,4%). The transaortic gradient after TAVI was almost zero mmHg in all patients and one had a severe aortic regurgitation. Permanent pacemakers were needed in 17% of patients. Two patients had a pericardial effusion, and one had a major vascular complication. No strokes were recorded, and 30-day mortality was 3.7%. At long-term follow up (23.4 ± 21.6 months) the global survival was 85% and the rate of cardiovascular mortality was 5.9%.

CONCLUSIONS

In this series of intermediate to high-risk patients, TAVI was associated with an excellent early and long-term survival.

Bridge therapy in hepatocellular carcinoma before liver transplantation: the experience of two Chilean centers

BACKGROUND

Orthotopic liver transplantation (OLT) is currently an established therapy for small, early-stage hepatocellular carcinoma (HCC) within the Milan criteria. Long waiting times due to the shortage of donor organs can result in tumor progression and drop-out from OLT candidacy. Therefore a wide variety of procedures are necessary before OLT. The aim of this retrospective study was to review our experience in relation to bridge therapy prior to OLT for HCC.

METHODS

This was a retrospective database review of all of the patient who underwent transplantation in our institutions between January 1993 and June 2009. We analyzed patients with a diagnosis of HCC in the explant.

RESULTS

Among 29 patients, including 12 who were diagnosed by the explant and 17 prior to transplantation, 88% underwent bridge therapy during a mean waiting time to OLT of 12 months. Among the 23 procedures, namely 1.5 procedures per patient, included most frequently chemoembolization (48%), alcohol ablation (30%), radiofrequency ablation (13%), and surgery (9%). Thirty-three percent of the explants contained lesions within the Milan criteria. In our series the 5-year survival rate for patients transplanted for HCC was 86%; in the bridge therapy group, it was 73%.

CONCLUSIONS

The incidence of patients who underwent bridge therapy (52%) was similar to other reported experiences, but the fulfillment of Milan criteria in the explants was lower. Among the bridge therapy group, the survival was slightly lower, probably because this group displayed more advanced disease.

Rapid steroid taper and neoral monotherapy in liver transplantation in Chile: a step in the right direction?

Diabetes, hypercholesterolemia, hypertension, obesity, osteopenia, and increased risk of viral recurrence are among the complications associated with posttransplant steroid use. Steroid withdrawal or rapid taper has been reported to be safe. The aim of this study was to compare the rejection incidence and severity among patients treated with two different steroid taper strategies.

METHODS

This retrospective study included all the adult liver transplant recipients since the program's inception from 1993 to January 2002. The minimum follow-up was 1 year. Exclusions included patients receiving an immunosupressive regimen other than mycophenolate mofetil, steroids, and Neoral, or suffering an autoimmune etiology, or displaying patient or graft survival less than 1 year. The incidence and severity of rejection episodes were compared between the two groups of steroid taper protocols: group A received methylprednisolone (1 g) intraoperatively with a slow taper to 10 mg prednisone per day at 1 year. Group B received methylprednisolone (2 g) intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Rejection diagnosis was made on histological bases.

RESULTS

One-month and 1-year rejection rates were 47% and 53%, respectively, among the rapid taper group with Neoral monotherapy, which was similar to 60% and 64%, respectively, in the slow taper group. Rejection severity was also comparable between the two groups.

CONCLUSIONS

Patients treated with a rapid steroid taper protocol followed by Neoral monotherapy or a slow taper protocol showed similar acute rejection incidences and severities. Their survival rates were also comparable. Further study is necessary to evaluate the impact of rapid steroid taper to prevent the complications of steroid use.

Predictive models in cirrhosis: correlation with the final results and costs of liver transplantation in Chile

Medical scores for predicting survival are essential to stratify patients with end-stage liver disease (ESLD) for prioritization for liver transplantation (OLT). Recently the UNOS has adopted the Mayo Model for End-stage Liver Disease (MELD) score as the basis for liver allocation in the United States. We retrospectively evaluated and assessed the prognostic impact, the length of stay (LOS), and hospital charges for OLT using two severity scores (Child-Turcotte-Pugh [CTP] versus MELD) to stratify cirrhotic patients before OLT. Twenty-six consecutive adult cirrhotic patients (11 women, mean age 46 years) underwent LT between 2000 and 2002. The main causes for transplantation were alcohol and primary biliary cirrhosis. The mean CTP and MELD scores at the moment of listing for OLT were 8.9 and 16.3 points, respectively. The best discriminative values with prognostic impact in terms of outcome and costs of OLT were a Child Pugh score >/=11 points or a MELD score >/=20 points. Patients in these strata showed a significant increase in LOS in the hospital (from a mean of 12 to 22 days) and intensive care stay (from a mean of 4 to 14 days) post-OLT when compared with patients with a lower CTP or MELD score (P <.05). There was also a trend toward higher hospital charges (P =.06). Organ allocation by MELD score will probably adversely affect the LOS and hospital charges of patients being transplanted due to ESLD.

A decade of adult liver transplantation in a single center in Chile

INTRODUCTION

Since the early days, liver transplantation (OLT) has conquered several barriers worldwide to become a proven therapy. We assessed the evolution of our adult liver transplant program.

METHODS

We studied all adult patients who underwent OLT since the inception from November 1993 through May 2003. Donor data, recipient pretransplantation evaluation, surgical technique, results, and costs were examined over our evolution, stratifying 3 groups over time, based on the number of adult OLT per year.

RESULTS

Between November 1993 and May 2003, 70 OLT were performed in 64 patients older than 15 years of age. Preoperative Child score, preoperative creatinine level, donor and recipient age, and proportion of emergencies were similar in the 3 groups. Over time, the predominant surgical technique was the piggyback technique (97% of OLT) with a decrease in the use of bypass from 63% to 5% during the last time period. Over the 10 years of our program's existence, warm ischemia time has been reduced to less than 1 hour, whereas cold ischemia time has remained constant at around 5 hours. Biliary and vascular complications decreased over time to around 10%. The mean length of hospital stay (LOS) decreased to 12 days (excluding emergencies). Since inception, our 1-year patient survival rate average is 91%; however, in just the last 3 years of our program (2000 through 2003), the 1-year patient survival rate is 97%.

CONCLUSIONS

In summary, our surgical technique has evolved toward piggyback use without veno-venous bypass with a significant decrease in warm ischemia times. As expected, our results have improved over time and our LOS and costs have decreased. Finally, our current results are similar to the best ones reported in the medical literature today.

Transcystic cholangiogram access via rubber band with early withdrawal after liver transplantation: A safe technique

OBJECTIVE

Since different techniques have been described for cholangiogram access after liver transplantation, we compared two different methods for patients with duct-to-duct biliary anastomoses.

METHODS

Adult liver transplant patients from program inception in 1993 to May 2003 in whom a duct-to-duct biliary anastomosis with a T-tube choledochostomy were compared with those having a transcystic duct catheter using a rubber band. We excluded 10 patients in which a different technique was used or graft or patient survived less than 21 days. Group A (n = 28,) had a number 10 T-tube exteriorized through the recipient main bile duct; and group B (n = 33) a number 5 Bard ureteral stent tied to the cystic stump with reabsorbable suture and secured with a hemorrhoidal rubber ligature.

RESULTS

The biliary complication rate was lower among the transcystic catheter group (9.1%, 3/33) compared to the T-tube group (35.7%, 10/28). Postcatheter withdrawal peritonitis was present in two patients in the T-tube group, one of whom required emergency laparotomy. A satisfactory postoperative cholangiogram was obtained in both groups. The transcystic catheter was withdrawn on average at 29 days, compared to 136 days in the T-tube group.

CONCLUSIONS

Both techniques are equally effective in obtaining a satisfactory postoperative cholangiogram. However, the transcystic catheter technique allows a significantly earlier withdrawal with fewer complications compared to the T-tube technique.

Clinical characterization and survival of adult patients awaiting liver transplantation in Chile

Liver transplantation has become widely used for patients with decompensated disease. Because of the shortage of donors, each year more patients die on the waiting list. Our aim was to characterize and evaluate the final outcomes of all listed candidates for liver transplantation during a 34-month period. We retrospectively evaluated all adults listed between January 2000 and November 2002. Sixty-three patients (37 women, mean age 45.8 years) were listed: 48 due to chronic liver disease and 15 for a highly urgent transplantation due to acute liver failure. The main etiology of chronic disease was alcoholic (22%) or primary biliary cirrhosis (17%). Of 52 chronic patients, 26 (50%) were transplanted with a mean waiting time of 168 days. Among the others, 8 died (15%) while awaiting transplantation, 3 (5%) were removed from the list, and 15 patients still await transplantation (28%). Among acute liver failure patients, the main etiologies were autoimmune (25%) and medication induced (25%). Of 15 acute patients, 6 (37.5%) have been transplanted at a mean waiting time of 6.8 days with 100% survival posttransplantation. In this cohort, 6 patients (37.5%) died while awaiting liver transplantation, and 4 (25%) survived with medical support. In conclusion, the severity of liver disease and death rate among our waiting list was similar to that observed in developed countries. It seems reasonable to review our current allocation system based on waiting time on the list. We will have to decide whether to transplant sicker patients or those with hepatocarcinoma (as in the United States recently with the MELD system), thereby possibly decreasing the mortality rate on the waiting list at the expense of higher costs and more difficult postoperative care or to just keep our current policy.

IL-2 receptor blockers in liver transplantation: initial experience with daclizumab in Chile

Monoclonal antibodies against the interleukin 2 receptor have been developed in an effort to decrease rejection rates and spare calcineurin inhibitors when renal dysfunction occurs after transplant. While success has been reported in kidney transplantation, its effectiveness in liver transplantation is less clear.

METHODS

This prospective nonrandomized study including adult patients was performed between October 2000 and April 2003. Two groups of immunosuppressive regimens were compared: group A received 2 g of methylprednisolone intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Cellcept was also given for 2 months in the absence or for up to 4 months in the presence of rejection. Group B received the same immunosuppressive regimen but, in addition, daclizumab 1 to 1.5 mg/kg on day 1 and day 5 posttransplant. Rejection diagnosis is made on histology basis. Protocol biopsies were performed in all the patients on day 7 and if indicated by biochemistry thereafter.

RESULTS

Both groups were similar in terms of preoperative CHILD score, serum creatinine, incidence of status I, donor and recipient age and ischemia times. The mean follow-up time was 20 months for Group B (n = 24) and 7 months for Group A (n = 10). The 1-month and 1-year rejection rates are 29.1% and 41% in Group A versus 20% and 30% in group B. Rejection severity was similar between both groups. One-year patient and graft survival rates were 96% and 92% in group A and 100% for both in Group B.

CONCLUSIONS

In this series, daclizumab induction therapy seems to display a trend toward a lower rejection rate without increasing infectious complications nor affecting graft survival rates.

Nitric oxide synthase activity in brain tissues from llama fetuses submitted to hypoxemia

The fetal llama (Lama glama; a species adapted to live in chronic hypoxia in the highlands of the Andes) did not increase cerebral blood flow and reduce the brain oxygen uptake during hypoxemia. Although nitric oxide (NO) is a normal mediator in the regulation of vascular tone and synaptic transmission, NO overproduction by hypoxemia could produce neuronal damage. We hypothesized that nitric oxide synthase (NOS) activity is either maintained or reduced in the central nervous system of the llama fetuses submitted to chronic hypoxemia. Approximately 85% of the Ca(2+)-dependent NOS activity was soluble, at least 12% was associated with the mitochondrial fraction, and less than 5% remains associated with microsomes. To understand the role of NO in chronic hypoxemia, we determined the effect of 24-h hypoxemia on NOS activity in the central nervous system. No changes in activity or the subcellular distribution of NOS activity in brain tissues after hypoxemia were found. We proposed that the lack of changes in NOS activity in the llama under hypoxemia could be a cytoprotective mechanism inherent to the llama, against possible toxic effects of NO.

Cardiorespiratory responses to acute hypoxemia in the chronically catheterized fetal llama at 0.7-0.9 of gestation

The adult llama (Lama glama) has several compensatory mechanisms that allow it to successfully survive at high altitude. Llama fetuses at 0.6-0.7 of gestation, and near-term llama fetuses studied close to surgery, did not increase cerebral blood flow and decreased cerebral oxygen delivery during acute hypoxemia. It is not known whether these responses were the result of immaturity or surgical stress. The aim of this study was to determine whether the lack of increase in cerebral blood flow and the decrease in cerebral oxygen delivery during hypoxemia in the fetal llama is characteristic of this high-altitude species near term, and under nonstressed conditions. We chronically catheterized 7 llamas and their fetuses near to term, at 0.7-0.9 of gestation. Fetal cardiac output, cerebral and regional blood flows, systemic blood pressure, heart rate, pH, and blood gases, organ vascular resistances and organ oxygen deliveries were determined at least 4 days after surgery, both during the basal state and after 1 hr of acute fetal hypoxemia. During hypoxemia the llama fetus did not increase cerebral blood flow and markedly decreased its cerebral oxygen delivery. There was also a marked decrease in kidney blood flow and oxygen delivery. These results indicate that, in contrast to fetuses of lowland species, the fetal llama does not increase the cerebral blood flow during hypoxemia, suggesting specific cellular mechanisms to preserve brain integrity during oxygen limitation.

Renal function in the chronically cannulated fetal llama: comparison with studies in the ovine fetus

Samples of maternal and fetal plasma, fetal urine, and amniotic fluid were collected from 8 chronically cannulated pregnant llamas, in the last third of gestation. The samples were obtained for up to 18 days post-surgery. Osmolality, sodium (Na), potassium (K), chloride (Cl), and urea were measured on 40 samples collected on days 1, 2, 3, 4-5, 6-7, 8-9, and 10-19. The osmolalities of maternal and fetal plasma, fetal urine and amniotic fluid, averaged over these 7 time periods, were, respectively, 312 +/- 2, 311 +/- 1, 484 +/- 14, and 317 +/- 1 mosmol kg-1. Values are given as mean +/- s.e. The major differences from fetal fluid values in the ovine fetus (from previously published values) were the higher osmolality and urea concentration of llama fetal urine. Urine flow rate measured in 6 fetuses, 4.5-6.5 kg body weight, was 5.8 +/- 0.4 mliter h-1; urea clearance rate was 55.5 +/- 11.8 mliter h-1. Glomerular filtration rate (GFR), measured with 51Cr-EDTA in 5 fetuses on 1-4 occasions, was 111.4 +/- 23.3 mliter h-1. Fractional reabsorptions (FR) of Na, K and Cl were 97.9 +/- 1, 75.9 +/- 13.5 and 97.7 +/- 0.4% respectively. The GFR (25 mliter kg-1 h-1) and urine flow rate (1 mL kg-1 h-1) were less than half and about one-tenth the respective values in ovine fetuses. As Na reabsorption is the major oxygen-consuming activity of the kidney, the llama fetal kidney requires only half the oxygen needed by the ovine fetal kidney to reabsorb the filtered sodium load. The reason for the formation of hypertonic, rather than hypotonic, urine in the fetal llama may be due to both greater morphological maturity of the kidney and the excretion of as yet unidentified osmotically active organic substances.

Air pollution in tropical areas

Air pollution problems in three different tropical areas are presented. The levels of various atmospheric contaminants (i.e. SO4) indicate that the operation of a large petroleum refinery affects a substantial portion of the island of Curacao. A significant fraction of the suspended particles in Curacao are due to non-traditional open source emissions aided by the predominantly high wind speeds. Particulate missions from the industrial complex in Guayana, Venezuela, noticeably affect the surrounding savannah. The constant direction of the Trade Winds is an important factor in the high long-term average particulate levels down-wind of the complex. A serious atmospheric contamination problem (i.e. TSP) exists in The Valley of Caracas. The high emission, principally due to the circulation of vehicles, exceed the average dispersion capacity of the atmosphere.

The Chlorine Atom Sensitized Oxidation and the Ozonolysis of C2Cl4

The chlorine atom initiated oxidation of C2Cl4 was studied both in the absence and presence of O3 at 24 and 32 °C. In the absence of O3, the products are CCl3CCl(O) and CCl2O, and they are produced in a long-chain process in a ratio of 2.5 at 24 °C and 3.0 at 32 °C. The product producing step involves the decay of C2Cl5O radicals[Formula: see text]The ratio k6a/k6b is 5.0 at 24 °C and 6.0 at 32 °C since CCl3 reacts with O2 to produce another CCl2O molecule. In the presence of O3 the ratio Φ{CCl3CCl(O)}/Φ{CCl2O} drops, [Formula: see text] is produced, and the chain length is reduced. The change in Φ{CCl3CCl(O)}/Φ{CCl2O} is a function of [O3]/[O2] and is attributed to the additional reactions[Formula: see text]The epoxide yield is a function of [C2Cl4]/[O3] and is attributed to the reaction of ClO with C2Cl4. The ClO is produced by the reaction of Cl• with O3[Formula: see text]which competes with[Formula: see text]The ratio k2/kl0 = 6.7. The reduction in yield as O3 is added results from the terminating reaction[Formula: see text]The ClO2 reacts further with O3 to produce Cl2O7.The reaction of O3 with C2Cl4 at 24 °C also produces mainly CCl3CCl(O) and CCl2O with [Formula: see text] as a minor product. Other minor products detected after extended conversions included Cl2, CO, and CO2. However c-C3Cl6 was not found. The ratio [CCl3CCl(O)]/[CCl2O] is < 1. Moreover, the addition of O2 retarded the reaction, indicating a long chain mechanism in which both free radicals (species with an odd number of electrons) and CCl2 were absent. A diradical chain mechanism is presented which explains the main features. The chain step is the addition of CCl2O2 to C2Cl4[Formula: see text]The adduct then reacts with O3 in a chain regenerating step or with O2 in a chain terminating step.

The Hg 6(3P)-Photosensitized Oxidation of C2Cl4

The Hg 6(3P) sensitized photolysis of C2Cl4 was studied at 25 °C both in the absence and presence of N2O and O2. For C2Cl4 alone, the only products are polymer and Hg2Cl2. The quantum yield of C2Cl4 disappearance, −Φ{C2Cl4} ∼ 1. Thus, the photolysis produces C2Cl3 radicals and Hg2Cl2, the C2Cl3 radicals dimerize, and the resultant 1,3-C4Cl6 polymerizes. The relative quenching of Hg 6(6P) by C2Cl4 compared to N2O is 3.0.In the presence of O2 the products are CCl3CCl(O) and CCl2O which are formed in a radical chain process in a ratio of 2.6 independent of reaction conditions. CO is also produced with a quantum yield of unity. The quantum yields of the chlorine-containing products are independent of the O2 pressure and the absorbed intensity, but are proportional to the C2Cl4 pressure, the proportionality constants being 1.4 and 3.7 Torr−1, respectively, for CCl2O and CCl3CCl(O). A detailed mechanism, based on the chlorine atom chain oxidation, is presented, and appropriate rate constant ratios are evaluated.

The Reaction of O(3P) with C2Cl4

The reaction of O(3P), prepared from Hg photosensitization of N2O with C2Cl4 was studied at 25 °C. The exclusive products of the reaction in the absence of O2 were CCl2O and polymer (as well as N2 from the N2O). The quantum yield of CCl2O production, Φ{CCl2O}, was 0.19 independent of the C2Cl4 pressure or the absorbed intensity, Ia. There was no evidence for CO, Cl2, c-C3Cl6, CCl3CCl(O), or [Formula: see text] production. The reaction mechanism is[Formula: see text]with k12a/k12 = 0.19. The CCl2 radical dimerizes and the energetic C2Cl4O* intermediate polymerizes. By competitive kinetics, the ratio k12/k13 was found to be 0.10, where k12 ≡ k12a + k12b and k13 is the rate coefficient of the O(3P) + C2F4 reaction.In the presence of O2, a chain process is involved in which CCl3CCl(O) and CCl2O are the major products. They are formed in a ratio of 2.0 independent of reaction conditions, but the chain length is proportional to [C2Cl4]/Ia1/2. Also produced is CO with a quantum yield of ∼0.18. The ratio Φ{CCl3CCl(O)}/Φ{CCl2O} = 2.0 is similar to that of 2.5 found in the Cl atom initiated oxidation. This result is interpreted to mean that chlorine atoms are involved in the chain. The reaction which initiates monoradicals in the system is[Formula: see text]