Search PubMed⌕ Search

Biomedical subjects

D M Shah

Publications and source records attributed to D M Shah.

At least 73 records · Page 4Linked to original sources
PubMed1996

Parameters associated with adverse perinatal outcome in hypertensive pregnancies.

BACKGROUND: Hypertensive disorders are a major contributor to perinatal morbidity and mortality. As all hypertensive pregnancies do not have a bad outcome, we sought to identify clinical and laboratory parameters associated with adverse perinatal outcome in hypertensive pregnancies. METHODS: We analyzed the clinical course of 271 hypertensive patients delivered at a tertiary center. Adverse perinatal outcome included: (1) perinatal death; and (2) perinatal morbidity due to hypertension-related prematurity and uteroplacental vasculopathy. In our analysis, we sought to compare good and adverse perinatal outcome groups of hypertensive pregnancies. Two sample t-tests were used for continuous variables and chi 2-tests were performed for categoric variables. Blood pressures (BP) were analyzed by multivariate analysis for four time periods (P, I through IV) defined by gestational age in weeks: I, 10-19; II, 20-24; III, 25-29; and IV, 30-36. RESULTS: There were 96 cases of adverse perinatal outcome due to hypertension (mortality, n = 6; morbidity, n = 90) in this series. Two clinical factors had a significant association with adverse perinatal outcome: (1) the need for prenatal treatment with antihypertensives (P < 0.0001); and (2) early onset of hypertension during the pregnancy (P < 0.008). The adverse outcome group had higher systolic (S) BP as early as 10-19 weeks (P < 0.01). This group had higher systolic and diastolic (D) BP as early as 20-24 weeks' gestation (P < 0.004-0.0001). Serum uric acid of > or = 6 mg/dl had a relative risk of 4.2 for adverse perinatal outcome (95% CI, 2.0-8.9; P < 0.0001). CONCLUSIONS: Our study suggests that the increased severity and longer duration of hypertension may be the primary pathophysiologic mediator of adverse perinatal effects in these pregnancies. Elevated serum uric acid may be a clinically useful predictor of perinatal mortality and, more importantly, of perinatal morbidity in hypertensive pregnancies.

Adult↗
PubMed1995

The osmotic response of the isolated, unfixed mouse tectorial membrane to isosmotic solutions: effect of Na+, K+, and Ca2+ concentration.

Changes in the size, shape, and structure of the isolated tectorial membrane (TM) of the mouse were measured in response to isosmotic changes in the ionic composition of the bathing solution. Substitution of artificial perilymph (AP) for artificial endolymph (AE) caused a small (approximately 1%) shrinkage of the TM's thickness. This substitution alters not only the predominate cation (from K+ to Na+) but also the Ca2+ concentration (from 20 mumol/l to 2 mmol/l). When the predominate cation was changed from K+ to Na+, while holding Ca2+ concentration constant, results depended on Ca2+ concentration: there was a small (approximately 1%) swelling for 20 mumol/l Ca2+, larger (approximately 14%) swelling for lower (< 7 mumol/l) concentrations of Ca2+, and little response for 2 mmol/l Ca2+ or for solutions containing the Ca2+ chelator EGTA. Addition of Ca2+ while holding the predominate cation constant caused shrinkage of the TM; both removal of Ca2+ and addition of the Ca2+ chelator EGTA caused swelling. Swelling responses were largely reversible if the magnitude of the swelling was small. Responses greater than a few percent were only partially reversible and caused long-lasting changes. Changes in ionic composition of the bath affected not only the thickness of the TM but also its other dimensions. Solution changes that increase TM thickness tend to cause radial shearing motions of the surfaces of the TM, which are accompanied by small decreases in width. Little change in length was observed. Although the responses were non-isotropic, increases in thickness were highly correlated with increases in volume. Swelling of the TM was also accompanied by a reduction in prominence of its radially oriented fibrillar structure. These results for the isolated TM of the mouse are qualitatively similar to those obtained previously for the isolated chick TM (Freeman et al., 1994) but different from those obtained for the in vitro mouse TM (Kronester-Frei, 1979a).

Acoustic Stimulation↗
PubMed1995

Does concomitant aortic bypass and renal artery revascularization using the retroperitoneal approach increase perioperative risk?

While elective repair of abdominal aortic aneurysms and aortoiliac occlusive disease is associated with an acceptable (3%) mortality rate, combined aortic and renal revascularization has usually been reported to have a higher perioperative mortality. Over the past 5 years, 785 elective aortic procedures have been performed at the authors' medical center. During the same period, 77 renal artery reconstructions have been performed in 73 patients in conjunction with aortic procedures. All were done using the retroperitoneal approach to the aorta and renal arteries. Indication for concomitant renal artery revascularization included 79% (61 of 77 patients) for either significant stenosis or anatomic involvement, 18% for renovascular hypertension (14 of 73) and 3% (two of 73) for renal impairment. The demographics and risk factors were similar in both groups. Operative mortality rate was 2.9% (23 of 785) in the aortic group and 3% (two of 73) in the combined group. Complications in the combined group were one stroke (1.4%), one re-exploration for bleeding (1.4%), two pulmonary pneumonia (2.7%) and five patients had elevated serum creatinine (> 350 mumol/l) after operation. Of these patients two died, one had an occluded graft and two eventually improved. There was one early graft thrombosis and one late thrombosis. In the authors' experience, concomitant aortic bypass and renal artery revascularization can be performed with an acceptable mortality and morbidity using the retroperitoneal approach.

Adult↗
PubMed1995

Choice of peroneal or dorsalis pedis artery bypass for limb salvage.

BACKGROUND: Arterial bypasses performed for limb salvage have increasingly used peroneal and pedal arteries as outflow. However, few reports have been published that compare the patency of limb salvage of these alternative outflow tracts. In this report, we have examined our experience with peroneal and dorsalis pedis (DP) artery bypasses for limb salvage. METHODS AND MATERIALS: Of more than 3,000 infrainguinal reconstructions performed for limb salvage, 732 were completed to the peroneal artery. During the same period, 238 bypasses were performed to the DP artery. Patient demographics were similar in both groups. The in situ technique was used in 68% of the peroneal bypasses and in 66% of the DP bypasses, respectively. Translocated veins were used in 28% of bypasses, and spliced veins were used in 32%. RESULTS: Secondary patency rates for the DP bypass at 1 and 5 years were 89% and 67%, respectively, as compared with 89% and 78% for the peroneal artery bypass. Limb salvage rates for the DP bypass were 94% at 1 year and 86% at 5 years, as compared with 96% and 93% at 1 and 5 years, respectively, for the peroneal artery bypass. No statistical difference was found. Four (1.7%) hemodynamic failures occurred in the DP group and 10 (1.4%) in the peroneal group. Wound complications were seen in 9 (3%) patients in the DP group and in 11 (1.5%) in the peroneal group. CONCLUSION: This experience indicates that both peroneal and DP bypasses have acceptable patency and limb salvage rates. Selection of one of these two outflow tracts, where a choice exists, may depend on the conduit limitation and adjacent tissue infection; however, both outflow tracts are durable and hemodynamically effective for limb salvage.

Ankle↗
PubMed1995

Arterial reconstruction for limb salvage: is the terminal peroneal artery a disadvantaged outflow tract?

BACKGROUND: Arterial reconstructions performed for limb salvage have increasingly used distal perimalleolar and pedal arteries as outflow tracts. However, a paucity of reports comparing the patency and limb salvage rates of these outflow tracts has been published. In this report we examine our experience with distal peroneal artery reconstructions for limb salvage. METHODS: During the past 14 years 159 bypasses were performed to the distal peroneal artery (within 5 cm of the malleolus), 157 of which were performed by the medial approach and two by the lateral approach. RESULTS: Sixty-three percent of the patients were male, 65% were diabetics, and 43% were smokers; the average age was 72.6 years. Sixty-five percent of the bypasses were performed with the in situ technique. Thirty-one percent of the bypasses were performed with translocated or spliced vein technique, and seven (4%) were performed with prosthetic technique. Secondary patency rates for distal peroneal artery bypass grafts at 1 and 5 years were 86% and 75%. The limb salvage rate for distal peroneal artery bypasses was 87% at 5 years. Four hemodynamic failures occurred in this group. Wound complications requiring revision were seen in one patient with a distal peroneal bypass (0.6%). These results do not differ from our results with other perimalleolar vessels. CONCLUSIONS: Arterial reconstruction to the distal peroneal artery has acceptable patency and limb salvage rates. These bypasses are as effective and durable as other perimalleolar bypasses.

Adult↗
PubMed1995

Foot amputations.

When presented with an ischemic limb with forefoot necrosis of varying amounts, the surgeon often categorizes the need for amputation into toe, ray, transmetatarsal, below-knee, and above-knee. Adherence to this type of algorithm ensures a primary above- or below-knee amputation rate of 10% to 20%. The utility of the more uncommon amputations advocated here is an increase of limbs deemed eligible for revascularization and limb salvage. Furthermore, delaying the amputations until the vascular supply is normalized maximizes tissue salvage and minimizes prolonged hospitalizations with multiple amputations performed as a prelude to major amputation. Although these amputations are often looked upon as an afterthought by many vascular surgeons, careful execution here is as important to effective limb salvage as any distal bypass procedure.

Amputation, Surgical↗
PubMed1995

The use of spliced vein bypasses for infrainguinal arterial reconstruction.

PURPOSE: The use of autogenous vein, whether in situ or excised, for arterial bypass procedures is well accepted. However, this usually requires the presence of a length of good-quality vein of adequate diameter. In patients lacking sufficient length of vein, two or more pieces of vein may be spliced together to complete the reconstruction. The effect of vein splicing on vein bypass patency is not well studied. METHODS: Over a 14-year period, 1956 lower extremity revascularizations were performed with a single autogenous vein, 1806 in situ and 150 excised veins. During the same time, 184 bypasses required splicing vein segments together, of which 111 were in situ bypass procedures, which required splicing of one or more pieces of excised vein to complete the reconstruction (partial in situ bypass). Seventy-three bypasses were completed with multiple pieces of spliced excised vein. The source for the excised, spliced vein segments was the distal ipsilateral greater saphenous vein (GSV) in 40%, accessory ipsilateral GSV in 8%, contralateral GSV in 13%, lesser saphenous vein in 28%, and arm vein in 11%. RESULTS: The 1- and 4-year primary patency rates for the entire spliced vein group were 72% and 45%, with secondary patency rates of 79% and 61%. The 1- and 4-year secondary patency rates of partial in situ bypasses were 80% and 70%, compared with 91% and 83% for in situ bypasses completed without a spliced segment (p < 0.0001). The 1- and 4-year secondary patency rates were 78% and 67% in the spliced excised vein group and 85% and 75% in the single excised vein group (p = not significant). The 4-year limb salvage rates were as follows: in situ (96%), partial in situ (85%), single excised vein (95%), and spliced excised vein (90%). CONCLUSIONS: We conclude that the use of excised vein segments to complete partial in situ bypasses may be associated with a decrement of bypass patency. Use of spliced excised vein segments of good quality for arterial bypass can produce acceptable patency rates. Such spliced autogenous conduits are clearly preferable to prosthetic bypasses for infrageniculate arterial reconstructions. Meticulous technique is a prerequisite for the successful performance of vein-to-vein anastomoses.

Arm↗
PubMed1995

Durability of short bypasses to infragenicular arteries.

OBJECTIVES: The purpose was to test the durability of the use of the unobstructed popliteal or tibial arteries as alternative inflow sources. MATERIALS: We examined 106 such bypasses performed during a 12 year period (1981-93). The indication for surgery was limb salvage in 99.1%. Seventy-five percent of the patients were male, 78% were diabetic and the average age was 59.6 years. The inflow source was the above-knee popliteal artery in 15 cases, the below-knee popliteal artery in 70 cases, the anterior tibial artery in 11 cases and the posterior tibial artery in 10 cases. Adequacy of inflow was determined by angiogram as well as intraoperative pressure measurement when indicated. Outflow was to a distal tibial or plantar arteries in 77.4% of the procedures. Forty-six bypasses were performed by an in situ technique. Excised vein was used as conduit in 60 patients (56.6%); greater saphenous vein (38), lesser saphenous vein (10), cephalic/basilic vein (4), and splice vein (8). RESULTS: Operative mortality was 2.8%. Five year cumulative primary patency was 75.4% with a secondary patency of 82.6%. Five year cumulative limb salvage was 93.5%. Patency rate was not significantly different for various inflows or outflows. Only four of the 106 bypasses ultimately required a reconstruction from the femoral level for proximal progression of disease. Bypasses performed using an in situ technique showed a significantly better 5 year cumulative secondary patency rate (96.3%) than those done with excised vein (70.5%), p < .05 CONCLUSION: Results of this study indicate that use of the popliteal or tibial arteries as an inflow source in the absence of significant proximal disease carries acceptable results, especially when using the vein in situ.

Adolescent↗
PubMed1995

Long-term results of in situ saphenous vein bypass. Analysis of 2058 cases.

OBJECTIVE: The authors evaluated the long-term patency and outcome of patients undergoing infrainguinal reconstruction using the in situ saphenous vein. SUMMARY BACKGROUND DATA: The in situ saphenous vein bypass has demonstrated excellent patency and limb salvage rates in numerous studies. The authors previously reported their early results with these bypass procedures, and this article represents their long-term experience with 2058 in situ saphenous vein bypasses during a 20-year period. This comprises the largest series with long-term follow-up of in situ saphenous vein bypasses in the literature. METHODS: From 1975 to 1995, 3148 autogenous vein bypasses were performed at the authors' institution, of which 2058 used the saphenous vein in situ. The indication for operation was limb-threatening ischemia in 1875 of 2058 patients (91%). In 88% of patients with an intact ipsilateral saphenous vein, an in situ bypass was completed successfully. One thousand twenty-three bypasses (69%) were terminated at the infrapopliteal level. Of these bypasses, 1562 of 2058 (76%) were completed using the closed in situ technique. RESULTS: The 30-day patency rate was 96%, and the cumulative secondary patency was 91%, 81%, and 70% at 1, 5, and 10 years, respectively. Limb salvage rates using the in situ bypass were 97%, 95%, and 90% at 1, 5, and 10 years, respectively. CONCLUSION: The infrainguinal inflow source, length of bypass, specific outflow vessel, or vein diameter did not have a significant effect on immediate or long-term bypass performance. These data suggest that the in situ saphenous vein is an excellent conduit for femoropopliteal and femoral to infrageniculate bypasses for limb salvage.

Adolescent↗
PubMed1995

Advanced triploid pregnancy and preeclampsia.

Triploidy, though unusual in advanced gestations, may be associated with preeclampsia. The increase in paternal genetic material associated with the triploid diandric placenta may support the role of immunologic factors in the development of preeclampsia.

Adolescent↗
PubMed1995

Disease resistance conferred by expression of a gene encoding H2O2-generating glucose oxidase in transgenic potato plants.

Plant defense responses to pathogen infection involve the production of active oxygen species, including hydrogen peroxide (H2O2). We obtained transgenic potato plants expressing a fungal gene encoding glucose oxidase, which generates H2O2 when glucose is oxidized. H2O2 levels were elevated in both leaf and tuber tissues of these plants. Transgenic potato tubers exhibited strong resistance to a bacterial soft rot disease caused by Erwinia carotovora subsp carotovora, and disease resistance was sustained under both aerobic and anaerobic conditions of bacterial infection. This resistance to soft rot was apparently mediated by elevated levels of H2O2, because the resistance could be counteracted by exogenously added H2O2-degrading catalase. The transgenic plants with increased levels of H2O2 also exhibited enhanced resistance to potato late blight caused by Phytophthora infestans. The development of lesions resulting from infection by P. infestans was significantly delayed in leaves of these plants. Thus, the expression of an active oxygen species-generating enzyme in transgenic plants represents a novel approach for engineering broad-spectrum disease resistance in plants.

Base Sequence↗
PubMed1994

Effect of chitinase antisense RNA expression on disease susceptibility of Arabidopsis plants.

Chitinases accumulate in higher plants upon pathogen attack are capable of hydrolyzing chitin-containing fungal cell walls and are thus implicated as part of the plant defense response to fungal pathogens. To evaluate the relative role of the predominate chitinase (class I, basic enzyme) of Arabidopsis thaliana in disease resistance, transgenic Arabidopsis plants were generated that expressed antisense RNA to the class I chitinase. Young plants or young leaves of some plants expressing antisense RNA had < 10% of the chitinase levels of control plants. In the oldest leaves of these antisense plants, chitinase levels rose to 37-90% of the chitinase levels relative to vector control plants, most likely because of accumulation and storage of the enzyme in vacuoles. The rate of infection by the fungal pathogen Botrytis cinerea was measured in detached leaves containing 7-15% of the chitinase levels of control plants prior to inoculation. Antisense RNA was not effective in suppressing induced chitinase expression upon infection as chitinase levels increased in antisense leaves to 47% of levels in control leaves within 24 hours after inoculation. Leaves from antisense plants became diseased at a slightly faster rate than leaves from control plants, but differences were not significant due to high variability. Although the tendency to increased susceptibility in antisense plants suggests that chitinases may slow the growth of invading fungal pathogens, the overall contribution of chitinase to the inducible defense responses in Arabidopsis remains unclear.

Arabidopsis↗
PubMed1994

Pelvic ischemia following aortoiliac reconstruction.

Clinically evident compromise of parietal or visceral pelvic function secondary to interruption of pelvic blood flow occurs infrequently after aortoiliac reconstruction. Certain patterns of aortoiliac or occlusive aneurysmal disease or graft infection may require exclusion of the hypogastric or profunda femoral arteries. In these situations collateral blood flow or retrograde iliac flow may be insufficient to perfuse the pelvis and may cause ischemia. We present three cases of postoperative pelvic ischemia and describe our efforts to restore pelvic perfusion.

Aged↗
PubMed1994

Clostridial aortic graft infection.

Aortic graft infection represents one of the most formidable challenges encountered by the vascular surgeon. Current principles of treatment are based on experience primarily derived from infection with Staphylococcus and enteric bacteria. Anaerobic prosthetic infection is a case event. Infection with Clostridium has heretofore been reported only twice. An additional case of clostridial infection of an aortic prosthesis is presented with review of the literature. Its clinical significance and management are discussed.

Aged↗
PubMed1994

Can the deep femoral artery be used reliably as an inflow source for infrainguinal reconstruction? Long-term results in 563 procedures.

PURPOSE: Historically, most infrainguinal bypasses originated from the common femoral artery. In spite of sporadic reports of the use of the deep femoral artery as an inflow source, its durability has not been critically reviewed. METHODS: From 1977 to 1994, 2829 infrainguinal reconstructions have been performed. Of these, 563 (20%) procedures have been performed with the deep femoral artery used as the inflow source. The indication for operation was limb salvage in 91.5% of cases. Four hundred eleven procedures were performed with use of the saphenous vein in situ, 48 were performed with partial in situ vein, and 75 were performed with excised (translocated) vein (29 other). When the deep femoral artery was relatively disease free, it was accessed through a lateral or standard inguinal approach. Reasons given for the use of the deep femoral artery were inadequate vein length, concomitant inflow procedures, prior groin dissections, and occluded superficial femoral artery. RESULTS: The 1- and 5-year secondary patency rates for all bypasses with the deep femoral artery were 90.4% and 76.9%, respectively, as compared with 88% and 73.3% for common femoral artery-based bypasses. Sixty-five patients (11.5%) had concomitant inflow procedures. All patients were monitored with serial noninvasive examinations, and data were collected from the vascular registry. Only eight patients (1.6%) required further inflow reconstructions for salvage of bypasses. CONCLUSIONS: The hemodynamically unobstructed deep femoral artery is a reliable and durable inflow source for patients requiring infrainguinal bypasses. Its patency rates are comparable to those of the common femoral artery-based reconstructions in our experience.

Femoral Artery↗
PubMed1994

Carotid endarterectomy can be safely performed with acceptable mortality and morbidity in patients requiring coronary artery bypass grafts.

BACKGROUND: Patients undergoing the placement of coronary artery bypass grafts (CABG) with hemodynamically significant carotid artery lesions pose a difficult problem for both cardiac and vascular surgeons. Despite numerous studies, there has been no consensus of opinion as to the proper management of these patients. In numerous series, the combined mortality and perioperative stroke rates in concomitant carotid endarterectomy and CABG procedures have ranged from 8% to 40%. This has made many surgeons consider staging these procedures. METHODS: Retrospective analysis of patients undergoing combined carotid endarterectomies and CABG from 1980 to 1993 were reviewed. Two hundred six procedures were performed in 189 patients. Seventeen patients had bilateral carotid endarterectomy performed with CABG. The average age of our patient population was 66 years, with 123 being male and 66 being female. Seventy-five percent of the patients were asymptomatic with the remainder having transient ischemic attacks, amaurosis fugax, or prior stroke. RESULTS: Operative mortality was 2%, with three of four patients dying of cardiac failure and one of a stroke. A temporary neurologic deficit was seen in 2% of patients, and a permanent neurologic deficit was seen in 2 of 206, or 1%. Thirty shunts were used in this series, mostly in patients with contralateral carotid occlusion. All procedures were performed under general anesthesia with full invasive monitoring. One patient was re-explored for bleeding, and one patient had a temporary hypoglossal palsy. A total of 203 cases had the arteriotomies closed primarily, and 3 required patches. CONCLUSION: In our experience, simultaneous carotid endarterectomy and CABG can be performed with an acceptable mortality and morbidity and does not appear to put the patient at an increased risk. Staging of these procedures may not be necessary in most cases.

Aged↗