PubMed Health⌕ Search

Biomedical subjects

R Singh-Ranger

Publications and source records attributed to R Singh-Ranger.

9 recordsLinked to original sources
PubMed2000

For debate: concomitant critical coronary arterial disease and abdominal aortic aneurysm--timing of corrective procedures.

BACKGROUND: The high prevalence of coronary artery disease (CAD) in patients with abdominal aortic aneurysm (AAA) is responsible for most , 30-day mortality and morbidity in elective repair of AAA. The continuing debate regarding staged or combined surgery for AAA and CAD (coronary artery bypass grafting -CABG) in the small number of patients with critical degrees of both co-morbidities has not had a significant impact on the greater mortality and morbidity when the AAA repair is undertaken using the standard open operation. PATIENTS: We report four cases with these combined pathologies which we have managed over the last 30 months during which time we have developed techniques of endolumenal repair of AAA. CONCLUSIONS: Whilst it is not possible to make firm recommendations regarding management strategy owing mainly to a lack of large series reporting this unusual combination of co-morbidities, the options are debated on the basis of published anecdotal evidence as well as our own case reports. We suggest that if the AAA is non-tender and/or 5.5-8.0 cm, the staged approach is appropriate. If the AAA is tender and/or > 8.0 cm, a combined approach may be a better option in order to avoid the risk of AAA rupture during the interval between the operations. Endolumenal repair of AAA offers a further option for the staged and combined approach, and may be less invasive than the standard open surgery for AAA repair.

Aged↗
PubMed2000

A prospective study of changes in aneurysm and graft length after endovascular exclusion of AAA using balloon and self-expanding endograft systems.

PURPOSE: Longitudinal shrinkage of aneurysms post-endovascular repair, employing unvalidated measurement techniques has been held to account for endograft disruption. In this study we record changes in aneurysm length, diameter and volume using the gold standard of calibrated spiral CT angiography (SCTA). METHOD: From 179 patients with AAA scanned by SCTA, 68 were selected for endografting. Twenty-seven had PTFE home-made prostheses while 41 patients had Talent endografts. SCTA was performed on the fifth postoperative day and 6-monthly intervals thereafter. The distance between the lowest renal artery and the aortic bifurcation (VBL - vertical body length) and the luminal centre line length (LCL) were measured. Maximal sac diameters and volumes were recorded using 3DCT reconstruction. RESULTS: Significant increase was noted in VBL (3.2) mm for PTFE-treated patients accompanied by an increase in sac volume at day 5 (12.5 ml). No changes in LCL or maximal diameters were evident. At 1.5 years further lengthening of both VBL (6.4 mm) and LCL (9.3 mm) was unaccompanied by sac diameter/volume changes. Talent patients - no changes in VBL or LCL were evident. Volumes and maximal AP and transverse diameters showed marked shrinkage: AP -11. 2 mm; transverse -2.6 mm; volumes by -35.5 ml at 6 months. CONCLUSION: With PTFE increase in VBL but not graft length, without concurrent changes in maximal diameters at day 5, is commensurate with increase in sac volume; after 1.5 years graft lengthening overtakes aortic lengthening. In Talent patients VBL/graft length remained unchanged. There is no evidence for longitudinal aneurysmal contracture. Volumes and maximal diameters for the Talent endograft but not for PTFE show shrinkage.

Aged↗
PubMed2000

Differing morphological changes following endovascular AAA repair using balloon-expandable or self-expanding endografts.

PURPOSE: To determine whether changes in aneurysm morphology after endovascular abdominal aortic aneurysm (AAA) repair differ according to the type of endograft (self-expanding versus balloon-expandable). METHODS: Among 88 patients with AAA treated with either homemade polytetrafluoroethylene (PTFE) aortomonoiliac endografts or Talent stent-grafts, 30 patients (24 males; mean age 73 years, range 55-93) were selected for this study based on a >2-year follow-up and freedom from endoleak or conversion. Of these, 12 had PTFE endografts and 18 Talent devices. All patients had spiral computed tomographic angiography with 3-dimensional reconstruction at 5 days posttreatment and 6-month intervals thereafter. Neck dimensions (length and diameters at 3 levels) were measured, along with volumes and maximal diameters of the sac and lengths of the aneurysm and endograft. Intra- and interobserver errors were <5% for linear and volume measurements. RESULTS: Both groups had an initial 20-mL increase in median volume (p = 0.02) followed, only in Talent patients, by marked shrinkage at 6 months (-87.4 mL; p = 0.09). PTFE patients had no further changes in sac volume. Maximal sac diameters reflected volumes, but only after day 5. PTFE patients had an immediate increase (p = 0.03) in aneurysm neck diameters, which then remained stable. Talent patients had continuing increases in diameter to 6 months (p < 0.05), with no change thereafter. Length changes were not significant in either group. PTFE patients had an increase in median aneurysm length at day 5 (+3.2 mm, p = 0.04) and again at 1.5 years (+6.4 mm, p = 0.03). Endograft length slowly increased (+18.7 mm) over 1.5 years (p = 0.02). Talent patients had no length changes in the device or aneurysm. CONCLUSIONS: Aneurysm morphology appeared to alter according to the type of endograft deployed. With PTFE endografts, aneurysm volume does not change, whereas impressive sac shrinkage occurs in conjunction with the Talent system. Aneurysm/graft lengths increase with unsupported stent-grafts. Neck diameter increases immediately with balloon-expandable endografts and then remains constant. In the self-expanding models, neck diameter increases at 6 months but not thereafter.

Aged↗
PubMed2000

The abdominal aortic aneurysm sac after endoluminal exclusion: a medium-term morphologic follow-up based on volumetric technology.

PURPOSE: The purpose of this study was to evaluate the role of three-dimensional spiral computed tomographic angiography (SCTA) for the assessment of the feasibility and results of endoluminal repair of infrarenal abdominal aortic aneurysm. METHODS: Laboratory studies: Phantom glass aneurysms, filled with contrast, underwent SCTA. The correlation between SCTA and laboratory measurements of linear dimensions and volumes was highly accurate (r(2) = 1.0). CLINICAL STUDIES: From the first 7 patients that were suitable for endoluminal repair, the correlation between SCTA and angiocatheter measurements was 0.85 to 0.99 (P <.04), but there was poor agreement between individual values. As determined from the measurements by 2 experienced investigators, intraobserver and interobserver errors for volume calculation in 12 randomly chosen scans from a total of 120 scans were 5.7 and 4.4 mL, respectively (range of volumes, 100-403 mL). The conditions of 53 patients were judged suitable for endoluminal repair of which 30 patients reached 1 year or more follow-up. The median aneurysm neck length and diameter were 24.5 mm (range, 11.5-60.8 mm) and 23.4 mm (18.3-31.5 mm), respectively. The fate of the sac after endografting by two techniques (pre-expanded polytetrafluoroethylene [PTFE] fixed with Palmaz stents and endografts) was defined with three-dimensional SCTA. RESULTS: The sac volume after endografting by pre-expanded PTFE (n = 12 patients) showed a significant median increase (P =.02) from 129 mL before surgery to 141 mL at 5 days after the operation with no change at 6 (139 mL), 12 (137 mL), and 18 (159 mL) months later. With the endografts (n = 18), there was an initial increase in median volume at 5 days (179-194 mL; P =.02) and then a significant shrinkage at 6 (148 mL; P =.012) and 12 (94.9 mL; P =.02) months. CONCLUSION: Three-dimensional SCTA has been validated and is both precise and reliable. Interobserver and intraobserver errors are within acceptable ranges. Angiocatheter measurements are less accurate and may give misleading information when used for patient selection and endograft construction. The sac volume increased after endografting and later shrank in patients who were treated with endografts, but not in those patients treated with pre-expanded PTFE. We propose that three-dimensional SCTA should be regarded as the gold standard for linear and volumetric measurement for infrarenal abdominal aortic aneurysm.

Aortic Aneurysm, Abdominal↗
PubMed1998

Endovascular repair for abdominal aortic aneurysms.

Endovascular exclusion could allow safe and successful treatment of abdominal aortic aneurysms. It may also be possible to use this technique in patients classed as high risk for conventional open repair. However, it is a new technique which has not been validated in a proper clinical trial. This review aims to outline current thinking in this field and the basis of the procedure.

Angioplasty, Balloon↗
PubMed1992

The comparative role of 1,25-dihydroxycholecalciferol and phorbol esters in the differentiation of the U937 cell line.

The active metabolite of cholecalciferol, 1,25-dihydroxycholecalciferol (1,25-DHCC), is a mononuclear phagocyte product with immunoregulatory properties which can influence not only surrounding T cells but also other mononuclear phagocytes; and which acts in an autocrine fashion. In this study we have used the U937 cell line as a starting point model to investigate further the comparative role of 1,25-DHCC and phorbol myristate acetate (PMA) upon growth, differentiation and phenotype in the mononuclear phagocyte system, and have correlated our findings with changes in 1,25-DHCC metabolism and receptor expression. Both 1,25-DHCC and PMA inhibit growth and differentiate U937 cells in a dose-dependent fashion. When used together, however, at low doses of PMA, 1,25-DHCC protects against the PMA-induced growth inhibition. At high concentrations of both compounds there is a decrease (1,25-DHCC) or an increase (PMA) in 1,25-DHCC receptor expression, with either 24-OHase (1,25-DHCC) or 1-OHase (PMA) synthesis. If the compounds are used in combination the receptor levels are equivalent to controls, and both enzymes are produced. The phenotype of the 1,25-DHCC-induced cells shows light adherence, class I+, increase in CD4 and CD14 and decrease in CD71. The PMA-induced cell is tightly adherent, class I+, and strongly positive for CD13 with a concomitant decrease in both CD4 and CD71. These findings suggest another role for 1,25-DHCC in the mononuclear phagocyte system, as a potential mitogenic agent. They also suggest that 1,25-DHCC may act at both membrane and nuclear levels within this model of the mononuclear phagocyte pathway and demonstrate one possible way in which physiological peripheral macrophage heterogeneity might be induced, i.e. due to the nature of the signals which are implicated during differentiation. The presence of increased CD4 and decreased CD13 on the surface of 1,25-DHCC-differentiated cells, and vice versa on PMA-differentiated cells, illustrates how this may then be reflected in functional mononuclear phagocyte heterogeneity, which may in turn be reflected in differential peripheral function.

Antigens, Surface↗