Biomedical subjects
J May
Publications and source records attributed to J May.
[Leishmaniasis. Basic principles, clinical aspects, diagnosis and therapy].
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Devices for aortic aneurysm repair.
Although the technical success and short-term efficacy of endovascular grafts have now been demonstrated, the long-term durability of grafts used in the aorta remains to be proven. No long-term data are yet available regarding device durability or patient outcome beyond the initial few years. Recent evidence shows that the ability of endovascular grafts to cause shrinkage and regression of aortic aneurysms may have a paradoxic effect of distorting the endograft itself, thus causing geometric changes within the supporting metallic framework and, ultimately, device failure (Fig. 9). Thus, the desired positive effect of the device may, ironically, lead to its eventual failure.
Successful completion of endoluminal repair of an abdominal aortic aneurysm after intraoperative iatrogenic rupture of the aneurysm.
PURPOSE: A method of achieving successful completion of endoluminal repair of an abdominal aortic aneurysm (AAA) in the presence of intraoperative iatrogenic rupture of the aneurysm is reported. METHODS: An 83-year-old woman with an AAA that was 7 cm in diameter was treated electively by means of endoluminal repair with a Vanguard bifurcated prosthesis (Boston Scientific, Natick, Mass). No difficulty was experienced with the introduction of the delivery catheter, despite extreme angulation in the aneurysm. An acute episode of hypotension prompted an aortogram to be performed. Extravasation of contrast outside the aneurysm sac was demonstrated. The balloon on the delivery catheter was immediately advanced to the suprarenal aorta and inflated. Hypotension was reversed, and hemodynamic stability was restored, thus enabling deployment of the prosthesis to proceed and the repair to be completed by means of the endoluminal method. RESULTS: The patient's blood pressure remained stable after deflation of the balloon, allowing a postprocedure aortogram to be performed. Exclusion of the aneurysm sac was demonstrated. Exclusion of the aneurysm sac from the circulation and a large retroperitoneal hematoma were confirmed by means of a postoperative contrast computed tomography scan. Convalescence was complicated by acute renal failure, pneumonia, and prolonged ileus. The patient remained well and active at the follow-up examination 6 months after operation. CONCLUSION: Iatrogenic perforation of an AAA during endoluminal repair may be treated by endovascular means and does not necessarily require conversion to open repair, although this may be the safest option.
Adverse events after endoluminal repair of abdominal aortic aneurysms: a comparison during two successive periods of time.
PURPOSE: The aim of this study was to document the incidence rate of adverse events after endoluminal repair of abdominal aortic aneurysms (AAAs) during two successive periods of time. METHODS: One hundred ninety patients (175 men, 15 women; mean age, 72 years) underwent endoluminal repair of AAAs in a 5(1/2)-year period. Adverse events were documented prospectively for all the patients throughout this interval. An adverse event was defined as any of the following events: a death within 30 days, a conversion to open repair, the need for further intervention (either open or endovascular), the need for hemodialysis, a failure to cure the AAA, and wound complications. The patients were divided into two groups those who underwent operation in the initial 3-year period (group I; n = 75) and those who underwent operation in the subsequent 2(1/2)-year period (group II; n = 115). The results were analyzed for total adverse events for both periods of time and for difference in incidence rates within categories of adverse events between the two groups. RESULTS: Eight patients (4.2%) died in the perioperative period. The endoluminal repair failed in 17 patients (8.9%), which necessitated a primary conversion to open repair at the original operation. In 88 patients, 110 adverse events occurred. There was no significant difference in the incidence rates of adverse events in patients in group I (37/75) and group II (51/115). Apart from primary conversion (P =.007), there was no significant difference in the incidence rates of adverse events between group I and group II within the following categories: perioperative (within 30 days) deaths, primary conversion, secondary conversion, supplementary endoluminal repair, intervention for lower limb ischemia, hemodialysis necessitated, failure to cure the AAA as a result of persistent endoleak, and wound complications. CONCLUSION: Despite improvements in technology and increasing experience, adverse events continue to occur in a relatively high proportion of patients (45%) who undergo endoluminal repair of AAA. Reporting the incidence rates of adverse events provides a more accurate picture of the morbidity rates of the endoluminal method rather than simply listing the procedures as successes or failures. The similarity in the incidence rates of adverse events in patients in group I and group II suggests that there are inherent risks in the endoluminal method rather than iatrogenic complications that occur during the learning curve with a new technique.
Endovascular treatment of abdominal aortic aneurysms.
OBJECTIVE: The purpose of this paper is to briefly review the historical aspects and outcome of endoluminal abdominal aortic aneurysm (AAA) repair and summarise two studies presented at the 1997 and 1998 meetings of the Society for Vascular Surgery. PATIENTS: Between May 1992 and September 1998 the endoluminal method was used to repair arterial aneurysms in 304 patients at the Royal Prince Alfred Hospital, Sydney, a tertiary referral teaching hospital. The study focuses on 243 patients with true AAA who underwent primary repair. There were 17 females and 226 males with a mean age of 72 years. Co-morbidities leading to rejection for conventional open repair were present in 83 patients. The criteria for inclusion included a segment of thrombus-free aorta between the lowermost renal artery and the commencement of the aneurysm of 1.5 cm or greater and iliac arteries that allowed access to the aorta from the groin. The technique involved the delivery of an endograft into the abdominal aorta by means of a sheath inserted through the femoral or iliac artery. Laparotomy associated with conventional open repair was avoided. Outcome measures included clinical examination and contrast-enhanced computed tomography (CT) within 10 days, at 6, 12, 18 months after operation and then annually thereafter. RESULTS: Endografts were successfully deployed in 226 patients. In the remaining 17 patients endoluminal repair was converted to open repair. There were 8 deaths within 30 days of operation giving a perioperative mortality rate of 3.3%. The two studies presented to the Society for Vascular Surgery concern: (i) a concurrent comparison of the endoluminal versus open methods of treating AAA; and (ii) a comparison of adverse events following endoluminal repair of AAA during two consecutive periods of time.
The occurrence of ochratoxin A in dust collected from a problem household.
Accumulated dust samples were collected from the heating ducts in a household where signs resembling ochratoxin poisoning in animals occurred. Several Penicillium spp. and Aspergillus ochraceous had been identified previously from air samples taken from this house. A composite sample from six collected samples was examined by HPLC, and it was determined that 58 ppb of ochratoxin A was present in this sample. A second set of six samples was collected and determinations were made by HPLC of the ochratoxin content in each sample. All samples, including one sample of dirt from a crawl space, yielded at least a trace of ochratoxin A; however, one sample of dust collected from the heating ducts yielded over 1500 ppb of ochratoxin A, and another sample of dust from a different heating duct yielded 306 ppb of ochratoxin A. Ochratoxin A was confirmed in all samples by LC-MS, and ochratoxin was evident in the samples by TLC analysis. This is believed to be the first report of finding ochratoxin in house dust.
The contribution of alpha+-thalassaemia to anaemia in a Nigerian population exposed to intense malaria transmission.
The proportion to which alpha-thalassaemia contributes to anaemia in Africa is not well recognized. In an area of intense malaria transmission in South-West Nigeria, haematological parameters of alpha-thalassaemia were examined in 494 children and 119 adults. The -alpha3.7 type of alpha+-thalassaemia was observed at a gene frequency of 0.27. Nine and 36.5% of individuals were homozygous and heterozygous, respectively. P.falciparum-infection was present in 78% of children and in 39% of adults. The alpha-globin genotypes did not correlate with the prevalence of P. falciparum-infection. alpha+-thalassaemic individuals had significantly lower mean values of haemoglobin, mean corpuscular volume, and mean corpuscular haemoglobin than non-thalassaemic subjects. Anaemia was seen in 54. 7% of children with a normal alpha-globin genotype, in 69.9% of heterozygous (odds ratio: 1.99, 95% confidence interval: 1.32-3.00, P = 0.001), and in 88.4% of homozygous alpha+-thalassaemic children (odds ratio: 7.72, 95% confidence interval: 2.85-20.90, P = 0.0001). The findings show that alpha+-thalassaemia contributes essentially to mild anaemia, microcytosis, and hypochromia in Nigeria.
Techniques for surgical conversion of aortic endoprosthesis.
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Rupture of abdominal aortic aneurysms: A concurrent comparison of outcome of those occurring after endoluminal repair versus those occurring de novo.
AIM: to compare the outcome of patients whose abdominal aortic aneurysm (AAA) ruptured following endoluminal repair with those whose AAA ruptured prior to treatment. PATIENTS: over a 4-year period 434 patients underwent treatment for AAA with conventional open (n=253) and endoluminal repair (n=181). Of those having open repair, 216 patients had elective operations while 41 had operations for ruptured AAA. Four patients with ruptured AAA had undergone endoluminal repair previously (Group I) while the remaining 37 patients ruptured de novo (Group II). The patients in both groups were similar in age and sex but differed clinically. All four patients in Group I had major medical co-morbidities versus 56% in Group II (p<0.05). All patients in group I had a known endoleak following endoluminal repair. All patients underwent open repair. RESULTS: the proportion of patients presenting with hypotension in Group I (1/4) was significantly less than in Group II (30/37). The difference in 30-day mortality for Group I (0%) compared with that for Group II (43%) was significant. The four patients in Group I remain alive and well at follow-up 22 months after operation. The outcome for Group I was better than Group II despite the higher incidence of medical co-morbidities. CONCLUSION: endoluminal AAA repair complicated by a persistent endoleak does not protect from rupture, which may not be accompanied by such major haemodynamic changes and high mortality as rupture de novo. Further long-term results in more patients are required to confirm this intermediate level of protection.
HLA class II factors associated with Plasmodium falciparum merozoite surface antigen allele families.
In Plasmodium falciparum malaria, certain human leukocyte antigens (HLA) and the parasite's merozoite surface antigens 1 and 2 (MSA-1, MSA-2) have been shown to influence the course of the infection. This report is on associations of distinct HLA factors with the occurrence of particular MSA families in a group of patients with either severe or mild P. falciparum malaria in Gabon. Different distributions of HLA-DPB1 alleles were found in the 2 groups. DR *04 alleles were observed more frequently among patients with severe malaria. Several alleles of different loci were associated with distinct MSA allele families. In addition, carriers of the amino acid methionine at position 11 of the DPA1 allele were more often infected by MSA-1 K1 parasites and less frequently by MSA-1 RO33 parasites. Furthermore, associations of HLA factors with polyclonal infections were found.
Plasmodium falciparum infection: influence on hemoglobin levels in alpha-thalassemia and microcytosis.
Plasmodium falciparum malaria, alpha-thalassemia, and anemia are frequent in African children. In 494 nonhospitalized Nigerian children, P. falciparum infection rates, alpha-globin genotypes, and hematologic parameters were determined. P. falciparum infection was observed in 78% of the children. The gene frequency of alpha-thalassemia was 0.28. Infection rates and parasitemia were similar for the 3 alpha-globin genotypes. In contrast to nonthalassemic and heterozygous persons, infection in children with homozygous alpha-thalassemia did not influence hemoglobin values. Because microcytosis and anemia are common features of alpha-thalassemia, their significance in P. falciparum infection was examined. Microcytosis was significantly associated with protection from hemoglobin decrease due to P. falciparum. Moreover, the rate of infection was lower in microcytic than in normocytic anemia.
The role of red blood cell polymorphisms in resistance and susceptibility to malaria.
In regions highly endemic for Plasmodium falciparum malaria, red cell polymorphisms that confer resistance to severe disease are widespread. Sickle cell trait, alpha-thalassemia, glucose-6-phosphate dehydrogenase deficiency, and blood groups were determined in 100 children from Gabon with severe malaria who were matched with 100 children with mild malaria and followed up for evaluation of reinfections. The sickle cell trait was significantly associated with mild malaria and blood group A with severe malaria. During follow-up, the original severe cases had significantly higher rates of reinfection than the original mild cases, with higher parasitemia and lower hematocrit values. Incidence rates did not differ in the context of erythrocyte polymorphisms, but patients with sickle cell trait presented with markedly lower levels of parasitemia than those without. Thus, the severity of malaria is partly determined by the presence of blood group A and the sickle cell trait. The different presentation of reinfections in severe versus mild cases probably reflects different susceptibility to malaria.
Symposium on distortion and structural deterioration of endovascular grafts used to repair abdominal aortic aneurysms. Introduction.
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Shortening of endografts during deployment in endovascular AAA repair.
PURPOSE: To evaluate the incidence and extent of length changes during implantation of endovascular grafts in a prospective study of patients undergoing endovascular abdominal aortic aneurysm (AAA) repair. METHODS: Data regarding the occurrence of intraoperative technical difficulties and device complications were recorded prospectively for the Vanguard or AneuRx self-expanding, bifurcated endovascular grafts in 64 patients (56 males; mean age 75 years). Graft length was measured in the sheath system before deployment and again immediately after deployment by fluoroscopic comparison to a graduated marking catheter. RESULTS: Graft shortening > or = 15 mm was documented in 22 (56%) of 39 Vanguard cases and 11 (44%) of 25 AneuRx endografts. Additional extension grafts were required to correct endoleak caused by inadequate graft length in 9 (14%) patients, but no conversion to open repair was necessary. CONCLUSIONS: There appears to be a high incidence of intraprocedural graft shortening with 2 current designs of self-expanding endoluminal grafts.
Endotension: an explanation for continued AAA growth after successful endoluminal repair.
PURPOSE: To present and analyze several cases that illustrate persistent sac pressurization following endovascular abdominal aortic aneurysm (AAA) repair. METHODS AND RESULTS: Four patients with successful endovascular AAA exclusion presented in follow-up with an expanding aneurysm. Two had initial sac diameter decrease, but by 18 and 24 months, respectively, the AAA had enlarged and become pulsatile. There was no endoleak evident, but the proximal attachment stents had mig rated distally in both cases. One patient developed endoleak with aneurysm expansion at 6 months; contained rupture occurred at 12 months. The last case had slowly evolving aneurysm expansion over 36 months but no endoleak. All endografts were removed and successfully replaced with conventional grafts. Intrasac thrombus was implicated as the means of pressure transmission that precipitated AAA expansion in these cases. CONCLUSIONS: Excluded AAAs can increase in size owing to persistent or recurrent pressurization (endotension) of the sac even when there is no evidence of endoleak. One proposed mechanism is pressure transmission via thrombus that lines the attachment site. Endotension may also represent an indiscernible, very low flow endoleak that allows blood to clot at the source of leakage.
High rate of mixed and subpatent malarial infections in southwest Nigeria.
The rate of malarial parasitemia in children and adults was assessed by microscopy and the polymerase chain reaction in a holoendemic area in Nigeria. A high rate of subpatent Plasmodium falciparum parasitemia (19.6%) was found. Plasmodium malariae and P. ovale infections were common in a rural area (26.1% and 14.8%) but were observed sporadically in individuals from an urban area. Simultaneous infections with P. falciparum, P. malariae, and P. ovale were frequent in the rural area (11.7% triple infections). The rate of triple infections was higher than expected from the prevalences of each species (P < 0.00001). Spleen enlargement was associated with mixed infections of P. falciparum and P. malariae (odds ratio [OR] = 5.9, 95% confidence interval [CI] 3.0-11.7) and less frequently observed in individuals without detectable parasitemia (OR = 0.06, 95% CI = 0.01-0.3). Spleen enlargement and titers of antibodies to schizonts were positively correlated with parasite densities. The results also suggest that in some individuals a long-lasting subpatent parasitemia might occur.
Short report: high prevalence and imbalanced age distribution of the Plasmodium falciparum dihydrofolate reductase gene Asn108 mutation in an area of low pyrimethamine usage in Nigeria.
Resistance of Plasmodium falciparum to pyrimethamine is associated with a non-silent point mutation of the parasite dihydrofolate reductase (DHFR) gene (Ser108 --> Asn108). Wide-scale use of antimalarials is thought to contribute to the emergence of drug resistance. In 131 P. falciparum-infected children in rural Nigeria, the frequency of the resistant Asn108 genotype was assessed by enzymatic restriction digestion of polymerase chain reaction-amplified DHFR sequences and compared with residual pyrimethamine blood levels. The prevalence of the Asn108 variant was 41.2%. In 18.3% of the isolates, both the Asn108 and the wild-type alleles were present. In contrast to the high prevalence of resistant genotypes, residual pyrimethamine blood levels were detected in only 4%. Furthermore, age was found to be a determinant of the parasite genotype since the proportion of Asn108 variants decreased with age (P < 0.05). These findings indicate that additional, unidentified factors, rather than selection by residual drug levels alone, might be responsible for the emergence of pyrimethamine-resistant parasite genotypes.