Can nitrogen-13 ammonia kinetic modeling define myocardial viability independent of fluorine-18 fluorodeoxyglucose?

OBJECTIVES: The hypothesis of this study was that evaluation of myocardial flow and metabolism using nitrogen-13 (N-13) ammonia kinetic modeling with dynamic positron emission tomographic (PET) imaging could identify regions of myocardial scar and viable myocardium as defined by fluorine-18 fluorodeoxyglucose (F-18 FDG) PET. BACKGROUND: Uptake of most perfusion tracers depends on both perfusion and metabolic retention in tissue. This characteristic has limited their ability to differentiate myocardial scar from viable tissue. The kinetic modeling of N-13 ammonia permits quantification of blood flow and separation of the metabolic component of its uptake, which may permit differentiation of scar from viable tissue. METHODS: Sixteen patients, > 3 months after myocardial infarction, underwent dynamic N-13 ammonia and F-18 FDG PET imaging. Regions of reduced and normal perfusion were defined on static N-13 ammonia images. Patients were classified into two groups (group I [ischemic viable], n = 6; group II [scar], n = 10) on the basis of percent of maximal F-18 FDG uptake in hypoperfused segments. Nitrogen-13 ammonia kinetic modeling was applied to dynamic PET data, and rate constants were determined. Flow was defined by K1; volume of distribution (VD = K1/k2) of N-13 ammonia was used as an indirect indication of metabolic retention. RESULTS: Fluorine-18 FDG uptake was reduced in patients with scar compared with normal patients with ischemic viable zones (ischemic viable 93 +/- 27% [mean +/- SD]; scar 37 +/- 16%, p < or = 0.01). Using N-13 ammonia kinetic modeling, flow and VD were reduced in the hypoperfused regions of patients with scar (ischemic viable flow: 0.65 +/- 0.20 ml/min per g, scar: 0.36 +/- 0.16 ml/min per g, p < or = 0.01; VD: 3.9 +/- 1.3 and 2.0 +/- 1.07 ml/g, respectively, p < or = 0.01). For detection of viable myocardium in these patients, the sensitivity and specificity were 100% and 80% for N-13 ammonia PET flow > 0.45 ml/min per g; 100% and 70% for VD > 2.0 ml/g; and 100% and 90% for both flow > 0.45 ml/min per g and VD > 2.0 ml/g, respectively. The positive and negative predictive values for the latter approach were 86% and 100%, respectively. CONCLUSIONS: In this cohort, patients having regions with flow < or = 0.45 ml/min per g or VD < or = 2.0 ml/g had scar. Viable myocardium had both flow > 0.45 ml/min per g and VD > 2.0 ml/g. Nitrogen-13 ammonia kinetic modeling permits determination of blood flow and metabolic integrity in patients with previous myocardial infarction and can help differentiate between scar and ischemic but viable myocardium.

Usefulness of intracoronary stenting in acute myocardial infarction.

Data on the feasibility, safety, and clinical outcome of intracoronary stenting in acute myocardial infarction (AMI) are limited. This study examined the immediate angiographic results and the early and late outcomes in 32 patients who had stenting during AMI. Coronary angiograms recorded at the time of stenting were reviewed with quantitative measurements obtained on the "target" coronary lesion before and after stenting. Immediate angiographic success was achieved in 30 patients (94%). The minimal luminal diameter increased from 0.36 +/- 0.37 to 2.58 +/- 0.41 mm (p<0.0001). Two patients died in the hospital. Of the remainder, none had reinfarction or required bypass surgery, whereas 2 required repeat coronary angioplasty for recurrent ischemia. Although thrombus at the infarct-related coronary lesion was initially detected in 41% of the patients, its presence was not associated with adverse procedural outcome. Only 1 patient had persistent thrombus after stenting, which resolved with intracoronary urokinase. At a mean follow-up of 6.1 +/- 4.1 months, there was 1 additional cardiac death, and no patient had AMI or required repeat coronary angioplasty or bypass; among the 29 survivors, 86% were free of angina. Thus, intracoronary stenting of the infarct-related artery in the setting of AMI is associated with excellent immediate angiographic success and a favorable clinical outcome, and remains an option even in the presence of thrombus.

Magnesium and certain other elements and cardiovascular disease.

Cardiovascular disease (CVD) continues to be the major cause of mortality in developed countries. For the past two-and-a-half decades the inverse relationship between water hardness and CVD mortality has stimulated interest among epidemiologists, clinicians and experimental researchers. Much progress has been made in elucidating which element in the water may account for this situation. After reviewing those elements found to have a role in cardiovascular function the authors present the epidemiological evidence and its consistency with recent findings: aside from various trace elements emphasis is placed on magnesium which is recognized as having a vital role.

Measuring drug effectiveness by default: the case of Bendectin.

In 1983, Bendectin was voluntarily removed from the market by Merrell Dow Pharmaceuticals Inc. because of the many product liability suits pending. Earlier, 10 to 25% of pregnancies were exposed to Bendectin and over the years the drug was used in as many as 33 million pregnancies. The scientific evidence available pointed to the safety of Bendectin. This article considers some of the effects of the withdrawal of the drug. In 1983, hospital admissions for excessive vomiting in pregnancy per thousand live births rose by 37% over 1980-82 ratios and by 50% in 1984. In the United States, hospitalization rose by similar amounts. A rough estimate of excess hospital costs over the years 1983-87 is $16 million for Canada and $73 million for the U.S. Such estimates do not take into consideration other costs, such as extra physician visits, increased absenteeism from work, and the effect on quality of life of the pregnant woman and her family. No decrease in rates of congenital malformations could be shown to offset this increased cost to society.

[Use of antibiotics among Danish children in 1998. Consumption on a national basis]. / Danske børns brug of antibiotika i 1998. Forbruget på landsplan.

The aim was to evaluate the use of antibiotics (AB) among Danish children in 1998. Patient specific data was collected on antibacterials for systemic use (ATC-group J01) prescribed for children aged 0-15 years in 1998. Data included a total of 585,491 prescriptions for 331,979 individuals. AB were prescribed for 33% of all Danish children on one or several occasions in 1998. Younger children were more likely to be treated with AB than older children. The one-year-prevalence of the use of AB was 63.2% for the 1-year-olds and 18.3% for 12-year-old children in 1998. The type of AB used varied with age, with younger children more prone to receive broad-spectrum AB. Eighty-three percent of all AB-prescriptions were prescribed by general practitioners. It is concluded, that AB, especially the broad-spectrum AB, are more often prescribed for younger than for older children and adults in Denmark in 1998.

[Utilization of anti-asthmatic drugs among Danish children in 1998]. / Danske børns brug af asthmamedicin i 1998.

INTRODUCTION: The aim of the study was to evaluate the use of anti-asthmatics among Danish children in 1998. METHODS: Patient specific data were collected on anti-asthmatics (ATC-group R03) prescribed for children aged 0-15 years in 1998. Data included a total of 381,557 prescriptions for 139,727 individuals. RESULTS: Anti-asthmatics were prescribed for 13.9% of all Danish children on one or several occasions in 1998. The highest one-year prevalence and incidence rate of drug use was found for children aged 0-2 years. Most children were exclusively treated with either a short acting beta 2-agonist (66.7%) or an inhaled steroid (6.5%). Only 26.2% received both types of anti-asthmatics. CONCLUSION: In conclusion, anti-asthmatics were predominantly prescribed for the youngest children. Most children were exclusively treated with a short acting beta 2-agonist in 1998, which is only recommended in the case of mild intermittent asthma.

'New data from old': epidemiology and record-linkage.

Record linkage in the context of epidemiology refers to the putting together of information (records) on the same person which may have been recorded on different occasions and became part of different data collections. The objective of this article is to provide an overview of the use of record linkage in epidemiology, particularly as it pertains to nutrition and food studies. A short description of epidemiological methodology is provided in order to clarify what epidemiologists expect to achieve by record linkage. A general description of the mechanics of record linkage explains how the methodology relates to the quality of the resulting data sets. The potential impact of the approach of record linkage on epidemiological research is discussed, particularly as it relates to nutritional and other food related studies. Ethical considerations related to record linkage are discussed, and in conclusion the future of record linkage is considered.