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Biomedical subjects

J F Walsh

Publications and source records attributed to J F Walsh.

At least 19 recordsLinked to original sources
PubMed1997

Dependency of contractile reserve on myocardial blood flow: implications for the assessment of myocardial viability with dobutamine stress echocardiography.

BACKGROUND: Contractile reserve, improvement in contractile function during inotropic stimulation, is a proposed marker of viable myocardium. This study was designed to address, in patients with left ventricular dysfunction due to chronic coronary artery disease, whether contractile reserve depends on myocardial blood flow. METHODS AND RESULTS: We studied 19 patients, at rest and during dobutamine, with 2D echocardiography for regional mechanical function and PET for regional myocardial blood flow ([(15)O]water) and oxygen consumption ([11C]acetate). Of 166 myocardial segments, 21 had normal systolic function, 56 were dysfunctional but contractile reserve-positive, and 89 were dysfunctional and contractile reserve-negative. Myocardial blood flow at rest was lower in contractile reserve-negative (0.41+/-0.18 mL x g(-1) x min(-1)) than in contractile reserve-positive (0.50+/-0.22 mL x g(-1) x min(-1)) and normal segments (0.55+/-0.20 mL x g(-1) x min(-1), P<.009). After dobutamine infusion, blood flow increased less in contractile reserve-negative (0.63+/-0.38 mL x g(-1) x min(-1)) than in contractile reserve-positive (1.28+/-0.65 mL x g(-1) x min(-1)) and normal segments (1.93+/-0.83 mL x g(-1) x min(-1), P<.0001). Likewise, myocardial oxygen consumption was lower at rest in contractile reserve-negative (clearance rate of [11C]acetate, 0.043+/-0.012 min(-1)) than in contractile reserve-positive (0.048+/-0.01 min(-1)) and normal segments (0.058+/-0.008 min(-1), P<.02). Myocardial oxygen consumption with dobutamine increased less in contractile reserve-negative (0.060+/-0.013 min(-1)) than in contractile reserve-positive (0.077+/-0.016 min(-1)) and normal segments (0.092+/-0.024 min(-1), P<.0001). Of segments defined as viable by PET, 54% were contractile reserve-negative and exhibited lower blood flow with dobutamine (0.72+/-0.36 mL x g(-1) x min(-1)) than with viable, contractile reserve-positive segments (1.29+/-0.70 mL x g(-1) x min(-1), P<.0001). CONCLUSIONS: Contractile reserve depends, in part, on the level of myocardial blood flow at rest and during inotropic stimulation.

Aged↗
PubMed1997

Blunt cardiac trauma: atrioventricular valve disruption and ventricular septal defect.

Nonpenetrating cardiac trauma resulting in cardiac chamber or valvar rupture is uncommon, requiring a high degree of suspicion for diagnosis. A case involving avulsion of the tricuspid and mitral papillary muscles with resultant interventricular septal rupture is reported. This case illustrates the importance of transesophageal echocardiography in the rapid diagnosis of blunt cardiac trauma. Surgical treatment of this condition is also discussed.

Accidents, Traffic↗
PubMed1996

Delineation of myocardial stunning and hibernation by positron emission tomography in advanced coronary artery disease.

With positron emission tomography, the resting flow abnormalities underlying reversible left ventricular dysfunction in 17 patients with chronic coronary artery disease were delineated. The level of flow in reversible dysfuncTional segments (i.e., those demonstrating improvement after revascularization) was markedly variable, ranging from 0.32 to 1.25 ml/gm/min. In 20 of these segments, flow was preserved, whereas in 12 segments, flow was reduced, when compared with that in, age-matched controls. Preservation of flow was associated with preservation of myocardial oxygen consumption and no alterations in myocardial substrate use. In contrast, a reduction in flow resulted in a decrease myocardial oxygen consumption and an increase in myocardial glucose use. Thus resting reversible left ventricular dysfunction in patients with chronic coronary artery disease can reflect a diversity of resting flow abnormalities. Moreover, myocardial perfusion at rest is frequently within normal limits, suggesting that the reversible mechanical dysfunction in these patients is attributable to intermittent myocardial stunning and not hibernation.

Adult↗
PubMed1995

Heterogeneity of myocardial perfusion provides the physiological basis of perfusable tissue index.

UNLABELLED: Assessment of viable from nonviable myocardium is critical for the care of patients being considered for revascularization procedures. Recently, the perfusable tissue index (PTI) has been proposed as an index of myocardial viability. METHODS: Computer simulations were performed for homogeneously and heterogeneously perfused tissue over a wide range of flows (0.04-6.4 ml/g/min) using both bolus and infusion inputs. RESULTS: PTI estimated from simulated homogeneously perfused tissue did reflect the amount of tissue being perfused independent of absolute level of flow, type of input or model configuration, whereas PTI obtained from simulated heterogeneously perfused tissue was consistently lower than the simulated "true" PTI and varied with flow, type of input function and model configuration. Flow estimated with 15O-water was not significantly different from that measured with radio labeled microspheres. CONCLUSION: Oxygen-15-water can diffuse into both acutely and chronically ischemic myocardium irrespective of its functional status. The results suggest that PTI is most likely an index of the heterogeneity of myocardial flow rather than an index of the amount of tissue being perfused. Its utility for delineating myocardial viability is thus related to the amount of tissue perfused that has low absolute levels of perfusion or high degrees of flow heterogeneity.

Analysis of Variance↗
PubMed1994

A rapid mapping technique for the prevalence and distribution of onchocerciasis: a Cameroon case study.

A rapid and cheap method for mapping the endemicity levels of onchocerciasis in both forest and savanna areas, where the vectors are members of the Simulium damnosum complex, is described. The selection of the study communities is based on a general understanding of the vectors' ecology and biassed towards those at highest risk of onchocerciasis, although there must be adequate geographical coverage. In a case study in Cameroon, prevalences were determined, using the non-invasive nodule palpation technique, in samples, each of 30-50 adult males, from 49 villages in six study areas in Cameroon. The method proved effective in the rapid mapping of onchocerciasis distribution in all areas studied, in which the distribution patterns varied from the classical linear to diffuse, and in one area with an anomalous distribution. The method should prove of value in the design of national onchocerciasis control programmes.

Adult↗
PubMed1994

Aggregated oviposition in the Simulium damnosum complex is mediated by eggs in a laboratory bioassay.

The phenomenon of aggregated oviposition in blackflies (Diptera: Simuliidae) was investigated under controlled laboratory conditions, using wild-caught females of the Simulium damnosum complex in Sierra Leone. A method was developed for inducing Simulium females to lay eggs, and used as a bioassay to measure the responses of gravid S. damnosum s.l. to freshly laid eggs of the same species complex. In a series of two-choice tests, significantly more ovipositing flies chose substrates already containing eggs over control substrates (P = 0.004). The time from introduction of flies into the oviposition system to the onset of egg-laying was significantly less when eggs were already present (P = 0.049). Flies responded more quickly when more eggs were present and the relationship between egg-batch number and the time of this response was curvilinear (P = 0.012). Ecological advantages and disadvantages of such aggregation behaviour and the possible role of semiochemicals in its mediation are discussed.

Animals↗
PubMed1993

Deforestation: effects on vector-borne disease.

This review addresses changes in the ecology of vectors and epidemiology of vector-borne diseases which result from deforestation. Selected examples are considered from viral and parasitic infections (arboviruses, malaria, the leishmaniases, filariases, Chagas Disease and schistosomiasis) where disease patterns have been directly or indirectly influenced by loss of natural tropical forests. A wide range of activities have resulted in deforestation. These include colonisation and settlement, transmigrant programmes, logging, agricultural activities to provide for cash crops, mining, hydropower development and fuelwood collection. Each activity influences the prevalence, incidence and distribution of vector-borne disease. Three main regions are considered--South America, West & Central Africa and South-East Asia. In each, documented changes in vector ecology and behaviour and disease pattern have occurred. Such changes result from human activity at the forest interface and within the forest. They include both deforestation and reafforestation programmes. Deforestation, or activities associated with it, have produced new habitats for Anopheles darlingi mosquitoes and have caused malaria epidemics in South America. The different species complexes in South-East Asia (A. dirus, A. minimus, A. balabacensis) have been affected in different ways by forest clearance with different impacts on malaria incidence. The ability of zoophilic vectors to adapt to human blood as an alternative source of food and to become associated with human dwellings (peridomestic behaviour) have influenced the distribution of the leishmaniases in South America. Certain species of sandflies (Lutzomyia intermedia, Lu. longipalpis, Lu. whitmani), which were originally zoophilic and sylvatic, have adapted to feeding on humans in peridomestic and even periurban situations. The changes in behaviour of reservoir hosts and the ability of pathogens to adapt to new reservoir hosts in the newly-created habitats also influence the patterns of disease. In anthroponotic infections, such as Plasmodium, Onchocerca and Wuchereria, changes in disease patterns and vector ecology may be more difficult to detect. Detailed knowledge of vector species and species complexes is needed in relation to changing climate associated with deforestation. The distributions of the Anopheles gambiae and Simulium damnosum species complexes in West Africa are examples. There have been detailed longitudinal studies of Anopheles gambiae populations in different ecological zones of West Africa. Studies on Simulium damnosum cytoforms (using chromosome identification methods) in the Onchocerciasis Control Programme were necessary to detect changes in distribution of species in relation to changed habitats. These examples underline the need for studies on the taxonomy of medically-important insects in parallel with long-term observations on changing habitats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

The vectorial efficiency of Simulium yahense populations in south-eastern Ghana.

Adult female Simulium yahense were identified amongst catches of S. damnosum s. 1. caught at Tsatsadu Falls and Wegbe in south-eastern Ghana. Dissections of stained flies to assess the species' role as a vector of onchocerciasis in the region revealed as many as 357 L3 per 1000 biting flies in a sample from Wegbe. When the data from the two sites were combined 154 L3 per 1000 biting flies and 315 L3 per 1000 parous flies were recorded. The values for wet season samples were about 12% higher than those for the dry season. The results are discussed in relation to other studies of S. yahense populations and regarding the species' recent spread in Ghana and Togo.

Animals↗
PubMed1990

The WHO Onchocerciasis Control Programme: retrospect and prospects.

The history of onchocerciasis control in Africa and the genesis of the WHO Onchocerciasis Control Programme in West Africa (OCP) are briefly reviewed. The importance of experience gained in anti-locust campaigns in helping to plan the OCP is stressed. Members of the Simulium damnosum species complex are the vectors of onchocerciasis, which OCP is controlling with insecticide treatments on the stretches of rivers where the Simulium breed. Migrations of flies have been responsible for reinfestations of controlled areas and the spread of insecticide resistance. The management of these problems and related research are described, but it is emphasized that despite setbacks OCP is achieving its aims. A strategy for the future is outlined: vector control supplemented by chemotherapy is expected to continue until the year 2004.

Africa, Western↗
PubMed1990

Bootstrapping: a tool for clinical research.

The use of the bootstrap sampling technique is applied to the type of data found in clinical research. Confidence intervals are computed for simulated values by use of SAS. By applying this approach, clinical researchers are free to explore topics that do not meet the requirements of traditional statistical analytic methods.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Gastric surgery for morbid obesity. The Adelaide Study.

The efficacy of three gastric restriction operations were compared in a prospective randomized study of 310 morbidly obese subjects. The median patient age was 34 years (range, 18 to 62 years). They were predominantly female (13:1) and had a median pre-operative weight that was 198% of their ideal weight (range, 160% to 318%). There was an equitable dispersion of perceived risk factors between the groups under study and there were no deaths during the perioperative period. Compliance with follow-up at 3 years was 91%. When success was defined as a loss of more than 50% of excess weight or a current pregnancy, the success rates at 3 years were 17% for gastrogastrostomy, 48% for vertical gastroplasty, and 67% for Roux-en-Y gastric bypass (p less than 0.001). Although the gastric bypass operation took longer to perform, there were similar outcome patterns for the three groups during the postoperative period. We conclude that the Roux-en-Y gastric bypass is the preferred procedure for the surgical treatment of morbid obesity.

Adult↗
PubMed1990

Psychosocial and physical activity changes after gastric restrictive procedures for morbid obesity.

Gastric restrictive procedures for morbid obesity are frequently performed to reduce problems arising from the physical limitations and social isolation of massive obesity. Numerous reports have described changes in weight after gastric restrictive operations, yet few studies have documented changes in the secondary effects of obesity. This report deals with changes in psychosocial status and physical activity occurring in 240 patients who remained in the study 3 years after surgery. These patients were members of a group of 310 patients who were entered into a prospective randomized trial to assess the relative benefits of three forms of gastric restrictive procedure. Prior to operation, and at yearly intervals after operation, the physical activities and psychosocial status of each patient was assessed by a standardized semi-structured interview. At the time of the three-year interview the median weight loss for these patients was 29.5 kg which represents 53% of excess weight lost. This weight loss was associated with a marked reduction in the amount of food eaten. There was a significant increase in the number of patients smoking more than 20 cigarettes a day and a mild increase in alcohol intake. There were significant improvements in the level of self-image and state of happiness. The social lives and sex lives of the majority of patients were improved and a significantly greater number of patients reported being in a stable emotional relationship at 3 years after operation than did so pre-operatively. There was a marked increase in the number of patients in full-time or part-time employment from 38% prior to surgery to 60% at 3 years after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Review of vector control prior to the OCP.

It is a little over 60 years since Blacklock, in an elegant study, demonstrated that in Sierra Leone human onchocerciasis was transmitted by a Simulium fly. Amazingly within 6 years of Blacklock's discovery an attempt was made, mainly using environmental management, to control Simulium in the Chiapas focus of Mexico, though this was not successful. Later Buckley was successful in eradicating Simulium neavei from the small Riana focus in Kenya by clearing riverine forest. However, it was not until DDT became widely available that Simulium control entered its heroic phase with campaigns in Kenya, Uganda and Zaire, some of which were highly successful. This led to an interest in controlling the vector in West Africa. The very different pattern of disease with very large foci virtually contiguous across tens of thousands of square kilometers suggested a difficult proposition and early attempts were not very successful. There is much of interest in the East and Central African schemes and in the West African forerunners of the OCP. In this talk an attempt will be made to capture something of the flavour of these pioneering efforts, to give credit to the men involved, and to highlight the successes against both the S. neavei and S. damnosum complex, and the advances which contributed to the successful planning of the OCP.

Africa↗
PubMed1989

A community trial of ivermectin in the onchocerciasis focus of Asubende, Ghana. I. Effect on the microfilarial reservoir and the transmission of Onchocerca volvulus.

A community trial of the microfilaricide ivermectin was undertaken in an isolated focus of hyperendemic savanna onchocerciasis in Ghana. One of the objectives was to determine the effect of mass treatment on the microfilarial reservoir and on the transmission of Onchocerciasis volvulus. Since 1978 the focus has been under entomological surveillance. This was intensified from 1 September 1987 till 11 February 1988 with daily vector collection and dissection of over 30,000 flies. A total of 14,991 people were treated with ivermectin on 7-10 October 1987. Skin snip surveys were done pre-treatment, and at two and four months after treatment. The mean skin microfilarial load in treated persons had fallen by more than 96% two months after treatment. During the next two months there was an increase in microfilaria loads which appeared to be faster than reported in the clinical trials. The total reservoir of skin microfilariae available for transmission had been reduced by an estimated 68%-78% two months after treatment. This was consistent with the entomological results which indicated a reduction in transmission of 65%-85% during the first three post-treatment months. The present study has shown for the first time that mass chemotherapy can significantly reduce onchocerciasis transmission. However, the remaining level of transmission was still unacceptably high and further studies are required to predict the long term impact of repeated mass treatment.

Animals↗