Biomedical subjects
Publications and source records attributed to R J Gibbons.
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The objective of this study was to assess the variability in myocardium at risk and relate this to coronary angiographic variables. One hundred ninety-seven patients with > or = 1-mm ST-segment elevation in 2 contiguous electrocardiographic leads, without prior myocardial infarction, were injected with technetium-99m sestamibi acutely before reperfusion therapy. The perfusion defect was quantified to determine myocardium at risk for infarction. Patients underwent coronary angiography to determine the infarct-related artery and to classify the occlusion as proximal or not proximal. Collateral and anterograde (Thrombolysis In Myocardial Infarction [TIMI] trial) flow were assessed in a subset of 83 patients with angiography before direct angioplasty. Myocardium at risk for infarction in the distribution of the left anterior descending coronary artery was significantly greater (p <0.0001) than that in the circumflex or right coronary artery. In the left anterior descending coronary artery distribution, myocardium at risk for infarction was significantly larger for proximal occlusions (p <0.0001). There was a trend toward greater myocardium at risk for infarction of proximal occlusions (p = 0.14) of the left circumflex but not for proximal occlusions in the right coronary artery distribution (p = 0.47). Multivariate analysis revealed that the infarct-related artery (p <0.0001), TIMI flow (p = 0.0002), and proximal location (p = 0.09) in the infarct-related artery were independent predictors of myocardium at risk for infarction. Thus, infarct-related artery, TIMI flow, and proximal location of occlusion in the infarct-related artery influence the myocardium at risk for infarction, which is highly variable for given location of occlusion.
The goal of this study was to compare measurements of left ventricular (LV) ejection fraction (EF) by first-pass radionuclide angiography ("first-pass angiography") using technetium-99m (Tc-99m) sestamibi with those by contrast-enhanced electron beam computed tomography ("electron beam tomography") as a reference technique in patients with an anterior wall acute myocardial infarction (AMI). Twenty-five patients with first Q-wave anterior wall AMI underwent paired electron beam tomographic and first-pass angiographic studies (mean, 1 day apart). Fourteen patients had 2 sets of measurements of the LVEF obtained by both methods (separated by at least 6 weeks), for a total of 39 paired measurements. LVEF by electron beam tomography was calculated from absolute systolic and diastolic LV chamber volumes. LV volumes by electron beam tomography were 199 +/- 51 ml at end-diastole and 111 +/- 42 ml at end-systole. Mean LVEF was 45 +/- 11% by first-pass tomography and 46 +/- 9% by electron beam tomography. The linear correlation coefficient between both methods was 0.82 (p <0.0001), with slope = 1.0, y-intercept = -1.1, and SEE = 6.1. The mean difference between the 2 methods was -0.7 +/- 6.0 EF units (p = 0.75). The correlation between the differences and means of both methods was 0.34 (p = 0.04), indicating a trend for first-pass angiography to overestimate LVEF in the higher range. LVEFs measured by first-pass angiography in patients with abnormal LV geometry and contraction patterns caused by anterior wall AMI agree well with those measured by electron beam tomography in the clinically relevant range.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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We have identified two females who are mosaic for an ATRX mutation. One case, in whom the mutation was undetectable in peripheral blood and buccal cells, has two affected sons and is therefore presumed to be a germline mosaic. In another case, the ATRX mutation is weakly detectable in the peripheral blood but only one of her three children who share the disease-associated haplotype carries the mutation and therefore it is concluded that she is a gonosomal mosaic. These cases provide the first molecular evidence for the occurrence of post-zygotic mutation in X-linked alpha thalassaemia mental retardation syndrome. The possibility of germline mosaicism must therefore be considered in the genetic counselling of ATR-X families.
Brachydactyly type B (BDB), an autosomal dominant disorder, is the most severe of the brachydactylies and is characterized by hypoplasia or absence of the terminal portions of the index to little fingers, usually with absence of the nails. The thumbs may be of normal length but are often flattened and occasionally are bifid. The feet are similarly but less severely affected. We have performed a genomewide linkage analysis of three families with BDB, two English and one Portugese. The two English families show linkage to the same region on chromosome 9 (combined multipoint maximum LOD score 8.69 with marker D9S257). The 16-cM disease interval is defined by recombinations with markers D9S1680 and D9S1786. These two families share an identical disease haplotype over 18 markers, inclusive of D9S278-D9S280. This provides strong evidence that the English families have the same ancestral mutation, which reduces the disease interval to <12.7 cM between markers D9S257 and D9S1851 in chromosome band 9q22. In the Portuguese family, we excluded linkage to this region, a result indicating that BDB is genetically heterogeneous. Reflecting this, there were atypical clinical features in this family, with shortening of the thumbs and absence or hypoplasia of the nails of the thumb and hallux. These results enable a refined classification of BDB and identify a novel locus for digit morphogenesis in 9q22.
OBJECTIVE: To determine whether adenosine could be safely administered to patients with chronic obstructive pulmonary disease (COPD) for coronary vasodilatation during perfusion scintigraphy without causing bronchospasm. MATERIAL AND METHODS: The study was divided into two phases. In the monitoring phase, patients with COPD were pretreated with an inhaled bronchodilator (albuterol) and had pulmonary function monitored during the infusion of a graduated dose of adenosine. Eligibility for entry into this phase of the study was determined on the basis of results of pulmonary function testing (PFT) during resting. Once we had shown that adenosine could be safely administered to patients with COPD, an implementation phase was begun. Entry did not require resting PFT, and patients were administered adenosine without monitoring of pulmonary function. Differences between patients with normal pulmonary function or mild COPD and those with more severe COPD were analyzed statistically. RESULTS: Of 94 patients entered into the monitoring phase, none had obvious bronchospasm. The dosage of adenosine was reduced in four patients because of a decrease in forced expiratory volume in 1 second (FEV1) of 20% in comparison with baseline (FEV1 before administration of albuterol). The mean FEV1 decreased slightly from 1.83 L after administration of albuterol to 1.78 L during the maximal adenosine dose. Patients with a remote history of asthma, positive result of a methacholine challenge test, or mild COPD (FEV1 60 to 80% of the maximal predicted value for age) did not differ significantly in their response to infusion of adenosine from those with moderate or severe COPD (FEV1 30 to 59% of the maximum predicted for age). Of 117 patients in the implementation phase, 2 had bronchospasm during infusion of adenosine that was quickly terminated by stopping the administration in one patient and reducing the dose of adenosine in the other. CONCLUSION: This study shows that adenosine can be safely administered intravenously to selected patients with known or suspected COPD to produce coronary vasodilatation for myocardial perfusion imaging. Patients who are within the guidelines established for this study should be considered for adenosine coronary vasodilatation with use of bronchodilator pretreatment, a graduated dose of adenosine, and regular chest auscultation during the infusion.
OBJECTIVE: The purpose of this study was to determine the extent and cause of radioactive contamination in our nuclear cardiology laboratory, and to develop possible solutions to minimize future occurrence. METHODS: We conducted a retrospective review to determine the underlying causes of the 15 minor radioactive contamination events that have occurred in the exercise areas of our laboratory since 1986. Of the 15 documented events, 8 were caused by failure of intravenous apparatus and 7 were due to syringe mishandling. Based on a staff questionnaire, we determined the most prevalent causes of radioactive contamination. Other than problems associated with intravenous setup, the causes were lack of experience by the individual performing the injection, followed closely by radioactive syringe disposal problems, injection technique, and unclear designation of duties during the exercise procedure. RESULTS: Based on these findings, we formulated a 4-part plan: a training program; a closely inspected intravenous apparatus; a mobile radioactive waste container; and a clear designation of duties for personnel to be included in the exercise procedure protocol. CONCLUSION: We have implemented a sensible and practical plan for reducing radioactive contamination, which is currently being evaluated.
BACKGROUND: Nearly half of patients hospitalized with unstable angina eventually receive a non-cardiac-related diagnosis, yet 5 percent of patients with myocardial infarction are inappropriately discharged from the emergency department. We evaluated the safety, efficacy, and cost of admission to a chest-pain observation unit (CPU) located in the emergency department for such patients. METHODS: We performed a community-based, prospective, randomized trial of the safety, efficacy, and cost of admission to a CPU as compared with those of regular hospital admission for patients with unstable angina who were considered to be at intermediate risk for cardiovascular events in the short term. A total of 424 eligible patients were randomly assigned to routine hospital admission (a monitored bed under the care of the cardiology service) or admission to the CPU (where patients were cared for according to a strict protocol including aspirin, heparin, continuous ST-segment monitoring, determination of creatine kinase isoenzyme levels, six hours of observation, and a study of cardiac function). The CPU was managed by the emergency department staff. Patients whose test results were negative were discharged, and the others were hospitalized. Primary outcomes (nonfatal myocardial infarction, death, acute congestive heart failure, stroke, or out-of-hospital cardiac arrest) and use of resources were compared between the two groups. RESULTS: The 212 patients in the hospital-admission group had 15 primary events (13 myocardial infarctions and 2 cases of congestive heart failure), and the 212 patients in the CPU group had 7 events (5 myocardial infarctions, 1 death from cardiovascular causes, and 1 case of congestive heart failure). There was no significant difference in the rate of cardiac events between the two groups (odds ratio for the CPU group as compared with the hospital-admission group, 0.50; 95 percent confidence interval, 0.20 to 1.24). No primary events occurred among the 97 patients who were assigned to the CPU and discharged. Resource use during the first six months was greater among patients assigned to hospital admission than among those assigned to the CPU (P<0.01 by the rank-sum test). CONCLUSIONS: A CPU located in the emergency department can be a safe, effective, and cost-saving means of ensuring that patients with unstable angina who are considered to be at intermediate risk of cardiovascular events receive appropriate care.
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BACKGROUND: Exercise stress testing in patients with abdominal aortic aneurysms may cause enlargement or rupture of aneurysms. OBJECTIVE: To evaluate the safety of treadmill exercise stress testing in patients with abdominal aortic aneurysms. DESIGN: Retrospective descriptive study. SETTING: Tertiary care center. PATIENTS: 262 patients who had abdominal aortic aneurysms more than 4 cm in diameter and underwent treadmill exercise stress testing. MEASUREMENTS: Pain after stress testing, rupture of the aneurysm or death, aneurysm size, and exercise stress test results. RESULTS: The average aneurysm diameter was 5.5 +/- 1.1 cm. One patient with a 6.1-cm aneurysm was found to have a contained rupture 12 hours after stress testing. The event rate for aneurysm rupture was 0.4% (95% CI, 0.0% to 2.1%). No deaths or other negative outcomes were documented. CONCLUSION: Despite theoretical concerns, exercise stress testing of patients with abdominal aortic aneurysms seems to be safe and is associated with a low incidence of acute adverse events.
Strategies to noninvasively evaluate patients after coronary stenting have not been evaluated. To determine the accuracy of single-photon emission computed tomography (SPECT) myocardial perfusion imaging in patients after coronary stenting, 209 patients who had undergone stenting followed by late stress SPECT myocardial perfusion imaging were evaluated. Quantitative coronary angiography was performed in 33 patients following SPECT imaging. SPECT restenosis was defined as a reversible or fixed defect within the stented vascular territory. Angiographic restenosis was examined using 2 definitions: total area narrowing > or =50% or > or =70% of the stent site or stented artery. The SPECT and angiographic findings were concordant in 22 of 33 stented vascular territories using the 50% definition of restenosis and in 29 of 33 stented territories using the 70% definition. Use of the 70% definition of restenosis resulted in improved accuracy of SPECT to detect a significant stenosis in the stented artery. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SPECT were 95%, 73%, 88%, 89%, and 88% respectively. In patients with positive SPECT scans, the most significant stenosis in the stented artery was outside the stent site in 50% of cases. SPECT imaging appears to be accurate to predict significant stenosis in the stented artery, although the most severe stenosis is frequently distant from the stent site.
This study examines the long-term prognosis of patients with an abnormal exercise radionuclide angiogram in the absence of significant angiographic coronary artery disease (CAD). In general, patients without significant CAD have an excellent prognosis, but the long-term outcome for the subset of patients with an "ischemic" exercise test is not known. In this study, 161 patients with normal coronary arteries or insignificant CAD (< 50% left main and < 70% left anterior descending, left circumflex, or right), resting left ventricular (LV) ejection fraction > or = 0.50, and an abnormal exercise radionuclide angiogram (LV ejection fraction that decreased with exercise or peak exercise LV ejection fraction < 0.60) were followed for a median duration of 11.3 years. The mean delta LV ejection fraction was -0.07, 98 patients (61%) had a decrease in LV ejection fraction of > or = 5 units, and 40 patients (25%) had peak exercise LV ejection fraction < 0.50. During follow-up there were 19 deaths (only 1 of which was cardiac), 7 nonfatal myocardial infarctions, and 9 revascularization procedures. At 12 years, overall survival was 88%, better than the expected survival for the age- and sex-matched general population. Survival free of cardiac death or myocardial infarction was 94% and survival free of any cardiac event including revascularization was 88%. Thus, patients with an abnormal exercise radionuclide angiogram but without significant CAD have an excellent long-term prognosis.