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H A McAllister

Publications and source records attributed to H A McAllister.

At least 19 recordsLinked to original sources
PubMed2001

One-at-a-time versus grouped presentation of mug book pictures: some surprising results.

Eyewitnesses to a simulated crime attempted to identify the perpetrator from a computerized mug book. The 208 mug book pictures were presented either 1 mug shot per page or in groups of 12 mug shots per page. Half of the mug books were arranged by similarity to the perpetrator as determined by a facial recognition algorithm, and half were randomly arranged. In contrast to past findings with photospreads, false-positive identifications were significantly higher using the one-at-a-time procedure than the grouped procedure. Results suggest that the best practice for mug books may be the use of groups of pictures per page rather than the one-at-a-time procedure long advocated by experts for use in lineups and photospreads.

Adult↗
PubMed2000

Evidence of Trypanosoma cruzi infection (Chagas' disease) among patients undergoing cardiac surgery.

BACKGROUND: Trypanosoma cruzi, the agent of Chagas' heart disease, is transmitted by triatomine insects and by blood transfusion. The emigration of several million people from T cruzi-endemic countries to the United States has raised concerns regarding a possible increase in cases of Chagas' heart disease here, as well as an increased risk of transfusion-transmitted T cruzi. To investigate these 2 possible outcomes, we tested a repository of blood specimens from multiply transfused cardiac surgery patients for antibodies to T cruzi. METHODS AND RESULTS: Postoperative blood specimens from 11 430 cardiac surgery patients were tested by enzyme immunoassay, and if repeat-reactive, were confirmed by radioimmunoprecipitation. Six postoperative specimens (0.05%) were confirmed positive. Corresponding preoperative specimens, available for 4 of these patients, were also positive. The other 2 patients had undergone heart transplantations. Tissue samples from their excised hearts were tested for T cruzi by polymerase chain reaction and were positive. Despite the fact that several of these 6 patients had histories and clinical findings suggestive of Chagas' disease, none of them were diagnosed with or tested for it. Patient demographics showed that 5 of 6 positive patients were Hispanic, and overall, 2. 7% of Hispanic patients in the repository were positive. CONCLUSIONS: No evidence for transfusion-transmitted T cruzi was found. All 6 seropositive patients apparently were infected with T cruzi before surgery; however, a diagnosis of Chagas' disease was not known or even considered in any of these patients. Indeed, Chagas' disease may be an underdiagnosed cause of cardiac disease in the United States, particularly among patients born in countries in which T cruzi is endemic.

Animals↗
PubMed2000

Partial left ventriculectomy: which patients can be expected to benefit?

BACKGROUND: Although some patients with end-stage heart disease will benefit from a partial left ventriculectomy, no criteria have been found for identifying this group preoperatively. Our experience with partial left ventriculectomy at two institutions-the Texas Heart Institute in Houston, TX, USA, and Dedinje Cardiovascular Institute in Belgrade, Yugoslavia-showed a higher survival rate and better postoperative myocardial function in the Yugoslavian patients. METHODS: We reviewed data from 42 patients (21 at each center) who had idiopathic cardiomyopathy, a left ventricular end-diastolic dimension of more than 70 mm, wall thickness of 1 cm or greater, and New York Heart Association class III or IV symptoms. The only significant difference in preoperative status between the two groups was duration of symptoms. Histologic specimens, blinded as to origin, were graded with regard to myocyte hypertrophy, cytoplasmic vacuolation, and fibrosis. Computer-assisted myocyte and nuclear morphometry was also performed. RESULTS: Immediately postoperatively, there were no significant intergroup differences in the reduction in cardiac dimension or in corrections of mitral regurgitation. During 6-month follow-up, however, the Texas Heart Institute patients had a lower cardiac index (1.8 versus 3.0 L x min(-1) x m(-2); p = 0.001) and left ventricular ejection fraction (24% versus 34%; p = 0.006) than the Dedinje Cardiovascular Institute patients. The Texas Heart Institute patients differed from the Dedinje Cardiovascular Institute patients in the degree of severe or moderate changes in myocyte hypertrophy (90% versus 29%; p = 0.0003) and fibrosis (71% versus 29%; p = 0.006), as well as in the measurements of median myocyte diameter (35 +/- 7 microm versus 27 +/- 4 microm; p = 0.0002) and median nuclear size (15 +/- 4 microm versus 12 +/- 2 microm; p = 0.0029). CONCLUSIONS: In the Texas Heart Institute patients, the significant intergroup difference in clinical outcome may have been related to increased myocyte hypertrophy and fibrosis. Further studies should be performed to determine the usefulness of these criteria in selecting patients for partial left ventriculectomy.

Adult↗
PubMed1999

Lowering the hemoglobin threshold for transfusion in coronary artery bypass procedures: effect on patient outcome.

BACKGROUND: There is controversy regarding the application of transfusion triggers in cardiac surgery. The goal of this study was to determine if lowering the hemoglobin threshold for red cell (RBC) transfusion to 8 g per dL after coronary artery bypass graft surgery would reduce blood use without adversely affecting patient outcome. STUDY DESIGN AND METHODS: Consecutive patients (n = 428) undergoing elective primary coronary artery bypass graft surgery were randomly assigned to two groups: study patients (n = 212) received RBC transfusions in the postoperative period if the Hb level was < 8 g per dL or if predetermined clinical conditions required RBC support, and control patients (n = 216) were treated according to individual physician's orders (hemoglobin levels < 9 g/dL as the institutional guideline). Multiple demographic, procedure-related, transfusion, laboratory, and outcome data were analyzed. Questionnaires were administered for patient self-assessment of fatigue and anemia. RESULTS: Preoperative and operative clinical characteristics, as well as the intraoperative transfusion rate, were similar for both groups. There was a significant difference between the postoperative RBC transfusion rates in study (0.9 +/- 1.5 RBC units) and control (1.4 +/- 1.8 RBC units) groups (p = 0.005). There was no difference in clinical outcome, including morbidity and mortality rates, in the two groups; group scores for self-assessment of fatigue and anemia were also similar. CONCLUSIONS: A lower Hb threshold of 8 g per dL does not adversely affect patient outcome. Moreover, RBC resources can be saved without increased risk to the patient.

Aged↗
PubMed1998

Immunohistochemistry of matrix metalloproteinases and their inhibitors in thoracic aortic aneurysms and aortic valves of patients with Marfan's syndrome.

BACKGROUND: Thoracic aortic aneurysms (TAAs) and valvular insufficiency, the main cardiovascular lesions in Marfan's syndrome, are associated with destruction of connective tissue; however, their pathogenesis remains unclear. METHODS AND RESULTS: To test the hypothesis that changes in the activity of the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are responsible for the damage to connective tissue in these lesions, histochemical studies of the immunoreactivity (IR) for MMPs and their tissue TIMPs (MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2) were made in TAAs (n = 7) and aortic valves (n = 5) from 7 patients with Marfan's syndrome. All TAAs showed cystic medial necrosis (CMN), with loss of elastic fibers and smooth muscle cells. Extensive areas of myxoid change were found in all aortic valves. Areas of CMN showed no IR for any MMPs or TIMPs. The IR of smooth muscle cells at the borders of areas of CMN was stronger for all MMPs, especially MMP-2 and MMP-9, than in other regions. The surfaces of disrupted elastic fibers showed IR for MMP-2 and MMP-9. Areas of myxoid change showed similar but less pronounced alterations. CONCLUSIONS: We hypothesize that the defect in fibrillin-1 in Marfan's syndrome leads to (1) formation of elastin that is abnormally aggregated and more easily degraded by MMPs than is normal elastin, (2) upregulation of the synthesis of MMPs, (3) progressive destruction of connective tissue by these enzymes, and (4) development of TAAs and valvular lesions.

Adolescent↗
PubMed1996

Sudden cardiac death in cardiac transplant recipients.

BACKGROUND: Sudden cardiac death (SCD) remains a significant cause of mortality in the general population. Its role in cardiac transplant patients-including its incidence, mechanism, potential risk factors, or influence on survival in this patient population-has not been well described. METHODS AND RESULTS: We undertook a retrospective analysis of the clinical and autopsy records of 257 patient deaths. SCD was analyzed in relation to severity and frequency of rejection episodes, clinical history of arrhythmias, coronary artery disease (CAD), hypertension, diabetes, left ventricular dysfunction, and clinical history of premorbid symptoms. A total of 25 patients were identified as having died of SCD, an incidence of 9.7%: 20% died < or = 12 months after transplantation, 80% died after > 12 months, and 20% died after > or = 60 months. Patient survival ranged from 2.5 to 138 months (mean, 45.7 months). The mean number of rejection episodes per patient was 2.6, most occurring within 12 months after transplantation. Echocardiography or multigated acquisition scan revealed an ejection fraction (EF) > or = 50% in 68% of patients; however, the presence of arrhythmias, primarily atrial, was evident in 68% of patients and was equally distributed between patients with EFs > or = 50% and EFs < 50%. CAD was present in 53% of patients (10 of 19) whose angiograms were available, and the appearance of CAD after transplantation was between 29 and 85 months (mean, 51.4 months). Of the 9 patients with normal cardiac catheterization studies, 6 with available autopsy reports had documented CAD. Autopsy data in 13 of 25 patients revealed CAD in 92% and rejection in 15% (International Society for Heart and Lung Transplantation grade > 3A). Of the deaths, 64% occurred within 3 months of the last endomyocardial biopsy, 96% had normal biopsies, and the only rejection was without hemodynamic compromise. CONCLUSIONS: SCD occurs relatively frequently in the cardiac transplant population, and CAD is present in most of the patients. Because the frequency of arrhythmias is relatively high in this group, more aggressive antiarrhythmic therapy may be beneficial for patients with allograft CAD in the prevention of SCD.

Adult↗
PubMed1996

Thermal detection of cellular infiltrates in living atherosclerotic plaques: possible implications for plaque rupture and thrombosis.

BACKGROUND: Atherosclerotic lesions are heterogeneous and prognosis cannot easily be predicted, even with intracoronary ultrasound and angioscopy. Serial angiographic and necropsy studies suggest that the risk of plaque rupture correlates only weakly with the degree of stenosis. Most ruptured plaques are characterised by a large pool of cholesterol or necrotic debris and a thin fibrous cap with a dense infiltration of macrophages. The release of matrix-digesting enzymes by these cells is thought to contribute to plaque rupture. Other thromboses are found on non-ruptured but inflamed plaque surfaces. We postulated that both types of thrombotic events may be predicted by heat released by activated macrophages either on the plaque surface or under a thin cap. METHODS: To test the hypothesis, we measured the intimal surface temperatures at 20 sites in each of 50 samples of carotid artery taken at endarterectomy from 48 patients. The living samples were probed with a thermistor (24-gauge needle-tip; accuracy 0.1 degree C; time contrast 0.15 s). The tissues were then fixed and stained. FINDINGS: Plaques showed several regions in which the surface temperatures varied reproducibly by 0.2-0.3 degrees C, but 37% of plaques had substantially warmer regions (0.4-2.2 degrees C). Points with substantially different temperatures could not be distinguished from one another by the naked eye; such points could also be very close to one another (< 1 mm apart). Temperature correlated positively with cell density (r = 0.68, p = 0.0001) and inversely with the distance of the cell clusters from the luminal surface (r = -0.38, p = 0.0006). Most cells were macrophages. Infrared thermographic images also revealed heterogeneity in temperature among the plaques. INTERPRETATION: Living atherosclerotic plaques show thermal heterogeneity, which raises the possibility that an infrared catheter or other techniques that can localise heat or metabolic activity might be able to identify plaques at high risk of rupture or thrombosis.

Carotid Arteries↗
PubMed1995

Blood use in patients undergoing repeat coronary artery bypass graft procedures: multivariate analysis.

BACKGROUND: The prevailing clinical opinion is that patients undergoing repeat coronary artery bypass graft (CABG) operation require more blood transfusions than do patients undergoing primary CABG operation. To determine the extent of this increased demand and the variables responsible for it, the cases of 196 patients who had undergone primary procedures and 65 patients who had had repeat procedures at the same institution were reviewed. STUDY DESIGN AND METHODS: To analyze the differences in transfusion requirements for these two groups, the following data were obtained: number of transfusions given between the time of surgery and the time of hospital discharge; preoperative hemoglobin (Hb), hematocrit (Hct), prothrombin time, and platelet count; Hb and Hct at hospital discharge; time the patient was on cardiopulmonary bypass; number and type of grafts; estimates of intraoperative blood loss; and chest-tube blood shed during the first 48 hours after surgery. RESULTS: The groups were comparable with respect to age, body weight, preoperative Hb and Hct, number of grafts, and aspirin exposure. Patients in the repeat group had 35-percent greater blood loss and required 75-percent more blood components than did the patients undergoing primary procedures. The mean number of blood components transfused per patient was as follows: red cells, 3.8 +/- 0.5 units in repeat patients and 2.2 +/- 0.2 units in primary patients (p = 0.002); platelets, 2.9 +/- 0.9 vs. 1.1 +/- 0.2 (p = 0.043); fresh-frozen plasma, 1.6 +/- 0.4 vs. 0.8 +/- 0.1 (p = 0.044). Analysis of variables by regression method for repeat patients showed a predictive effect of blood loss (p < 0.0001), prolonged time on cardiopulmonary bypass (p < 0.0001), preoperative Hb (p = 0.0003), and aspirin exposure (p = 0.0094) on red cell transfusion rate in repeat patients (R-square = 0.7778, Prob > f = 0.0001). CONCLUSION: Repeat CABG patients have higher transfusion rates. These findings may be attributed to the increased microvascular bleeding, prolonged time on cardiopulmonary bypass, lower preoperative Hb, and the use of preoperative antiplatelet medications.

Aged↗
PubMed1992

The declining risk of post-transfusion hepatitis C virus infection.

BACKGROUND: The most common serious complication of blood transfusion is post-transfusion hepatitis from the hepatitis C virus (HCV). Blood banks now screen blood donors for surrogate markers of non-A, non-B hepatitis and antibodies to HCV, but the current risk of post-transfusion hepatitis C is unknown. METHODS: From 1985 through 1991, blood samples and medical information were obtained prospectively from patients before and at least six months after cardiac surgery. The stored serum samples were tested for antibodies to HCV by enzyme immunoassay, and by recombinant immunoblotting if positive. RESULTS: Of the 912 patients who received transfusions before donors were screened for surrogate markers, 35 seroconverted to HCV, for a risk of 3.84 percent per patient (0.45 percent per unit transfused). For the 976 patients who received transfusions after October 1986 with blood screened for surrogate markers, the risk of seroconversion was 1.54 percent per patient (0.19 percent per unit). For the 522 patients receiving transfusions since the addition in May 1990 of screening for antibodies to HCV, the risk was 0.57 percent per patient (0.03 percent per unit). The trend toward decreasing risk with increasingly stringent screening of donors was statistically significant (P less than 0.001). After we controlled for the method of donor screening, the risk of seroconversion was strongly associated (P less than 0.001) with the volume of blood transfused, but not with the use of particular blood components. CONCLUSIONS: The incidence of post-transfusion hepatitis C has decreased markedly since the implementation of donor screening for surrogate markers and antibodies to HCV. The current risk of post-transfusion hepatitis is about 3 per 10,000 units transfused.

Alanine Transaminase↗
PubMed1992

Ionescu-Shiley bovine pericardial bioprostheses. Histologic and ultrastructural studies.

Studies were done on the structural changes that develop in Ionescu-Shiley valves that are used as replacement heart valves for 4 to 8 years. These changes were compared with those found in similarly used porcine aortic valve (PAV) bioprostheses. A variety of morphologic differences were observed between bovine pericardial valve (BPV) and PAV bioprostheses after orthotopic implantation including: primary tissue failure associated with the use of an alignment suture, thickening of valve leaflet, leaflet tissue delamination, leaflet calcification, and dystrophic alterations of collagen. These findings indicate that valve design criteria directly influence the durability of pericardial valves. However, other factors unique to pericardial tissue also affect the durability and performance of BPVs. These factors include the inability of pericardial tissue to accommodate dynamic stresses; the extensive insudation of plasma proteins and lipids; and the inability to reduce leaflet calcification using agents that effectively mitigate calcification in PAV bioprostheses.

Adult↗
PubMed1990

Risk factors for development of accelerated coronary artery disease in cardiac transplant recipients.

Allograft coronary artery disease (CAD) is the major determinant of long-term survival following heart transplantation (HTx). In a group of 210 heart transplant recipients, we diagnosed CAD in 54 (27.1%) by coronary angiography, postmortem examination or examination of the transplanted heart at the time of retransplantation. Retrospective analysis of potential risk factors for the development of CAD was performed for both immunological (rejection pattern, immunosuppressive therapy, cytomegalovirus [CMV] infection), and nonimmunological (hyperlipidemia, smoking, hypertension, diabetes mellitus, obesity) risk factors. The total number of rejection episodes correlated significantly with the occurrence of CAD (P less than 0.05), showing that patients who experienced two or more rejection episodes had an incidence of CAD of 40%, as opposed to a 23% incidence in patients who experienced no rejection. A composite rejection score derived from multivariate regression analysis of the severity, frequency, and timing of acute cardiac rejection episodes was found to correlate with the development of CAD (P less than 0.05). Postoperative arterial hypertension also correlated significantly with the onset of CAD (P less than 0.01), with a 92.6% incidence of hypertension in the group with CAD versus 76.3% in the group without CAD. Smoking after transplantation correlated significantly with the occurrence of CAD (P less than 0.05). There was no significant correlation with other analyzed factors in this group of patients. In this review, the development of CAD after heart transplantation correlated with treated allograft rejection. Aggressive treatment of hypertension and cessation of smoking may contribute to alleviation of this serious complication.

Coronary Disease↗