PET imaging of cardiac hypoxia: opportunities and challenges

Myocardial hypoxia is a major factor in the pathology of cardiac ischemia and myocardial infarction. Hypoxia also occurs in microvascular disease and cardiac hypertrophy, and is thought to be a prime determinant of the progression to heart failure, as well as the driving force for compensatory angiogenesis. The non-invasive delineation and quantification of hypoxia in cardiac tissue therefore has the potential to be an invaluable experimental, diagnostic and prognostic biomarker for applications in cardiology. However, at this time there are no validated methodologies sufficiently sensitive or reliable for clinical use. PET imaging provides real-time spatial information on the biodistribution of injected radiolabeled tracer molecules. Its inherent high sensitivity allows quantitative imaging of these tracers, even when injected at sub-pharmacological (≥pM) concentrations, allowing the non-invasive investigation of biological systems without perturbing them. PET is therefore an attractive approach for the delineation and quantification of cardiac hypoxia and ischemia. In this review we discuss the key concepts which must be considered when imaging hypoxia in the heart. We summarize the PET tracers which are currently available, and we look forward to the next generation of hypoxia-specific PET imaging agents currently being developed. We describe their potential advantages and shortcomings compared to existing imaging approaches, and what is needed in terms of validation and characterization before these agents can be exploited clinically.

Detection of intracoronary thrombus by magnetic resonance imaging in patients with acute myocardial infarction

BACKGROUND

Persistent intracoronary thrombus after plaque rupture is associated with an increased risk of subsequent myocardial infarction and mortality. Coronary thrombus is usually visualized invasively by x-ray coronary angiography. Non-contrast-enhanced T1-weighted magnetic resonance (MR) imaging has been useful for direct imaging of carotid thrombus and intraplaque hemorrhage by taking advantage of the short T1 of methemoglobin present in acute thrombus and intraplaque hemorrhage. The aim of this study was to investigate the use of non-contrast-enhanced MR for direct thrombus imaging (MRDTI) in patients with acute myocardial infarction.

METHODS AND RESULTS

Eighteen patients (14 men; age, 61±9 years) underwent MRDTI within 24 to 72 hours of presenting with an acute coronary syndrome before invasive x-ray coronary angiography; MRDTI was performed with a T1-weighted, 3-dimensional, inversion-recovery black-blood gradient-echo sequence without contrast administration. Ten patients were found to have intracoronary thrombus on x-ray coronary angiography (left anterior descending, 4; left circumflex, 2; right coronary artery, 4; and right coronary artery-posterior descending artery, 1), and 8 had no visible thrombus. We found that MRDTI correctly identified thrombus in 9 of 10 patients (sensitivity, 91%; posterior descending artery thrombus not detected) and correctly classified the control group in 7 of 8 patients without thrombus formation (specificity, 88%). The contrast-to-noise ratio was significantly greater in coronary segments containing thrombus (n=10) compared with those without visible thrombus (n=131; mean contrast-to-noise ratio, 15.9 versus 2.6; P<0.001).

CONCLUSION

Use of MRDTI allows selective visualization of coronary thrombus in a patient population with a high probability of intracoronary thrombosis.

Quantitative analysis of transmural gradients in myocardial perfusion magnetic resonance images

Conventional quantitative assessments of myocardial perfusion analyze the temporal relation between the arterial input function and the myocardial signal intensity curves, thereby neglecting the important spatial relation between the myocardial signal intensity curves. The new method presented in this article enables characterization of sub-endocardial to sub-epicardial gradients in myocardial perfusion based on a two dimensional, "gradientogram" representation, which displays the evolution of the transmural gradient in myocardial contrast uptake over time in all circumferential positions of the acquired images. Moreover, based on segmentation in these gradientograms, several new measurements that characterize transmural myocardial perfusion distribution over time are defined. In application to clinical image data, the new two-dimensional representations, as well as the newly defined measurements revealed a clear distinction between normal perfusion and inducible ischaemia. Thus, the new measurements may serve as diagnostic markers for the detection and characterization of epicardial coronary and microvascular disease.

[Pars plana vitrectomy for idiopathic macular hole--visual improvement or merely surgical stress?]

BACKGROUND

The aim of this study was to compare the functional results of surgical treatment of idiopathic macular holes in controlled clinical studies with those of the "real world" in the clinical routine.

METHODS

The operated eyes of patients of a rural district (Saalfeld-Rudolstadt, Germany) during 2000-2009 were analysed based on the documentation of the postoperative care of all ophthalmologists in this region.

RESULTS

37 eyes of 37 patients (age 71 years, 45; 80) (median, [min; max]) operated in 7 clinical institutes were analysed. The past medical history until surgery was 4 months (1; 72) and the preoperative visual acuity (VA) 0.2 (0.01; 0.5). The observational period after surgery was 2.3 years (1; 6 years), all eyes were documented over more then 1 year thereafter. At the last control the VA improved ≥ 2 lines in 17 eyes (46%) and decreased ≥ 2 lines in 8 (22%). 13 eyes (35%) obtained a VA ≥ 0.5. A short preoperative period corresponded with a visual improvement (K = 0.40, p = 0.01). A further increase of VA after one year could be observed only due to cataract surgery or Nd:YAG laser capsulotomy. 8 eyes (22%) needed at least one more vitreoretinal surgery.

DISCUSSION

Reasons for the disappointing functional results compared with the literature could be long medical history, not differentiated grades of macular holes and developing surgical techniques during the analysis period. Retrospective analyses of the outcome of routine practical work seems to be a necessary complement of controlled clinical studies despite their methodical deficits. New prognostic criteria are needed for a better indication for surgery and an improved counselling of the patient.

[BEO'S - physical activity and healthy eating at schools in Oberfranken, Bavaria concept and first results of a resource-oriented, systemic approach in school-based health promotion]

BACKGROUND

The high prevalence of overweight among children and adolescents has led to an increase in school-based prevention programmes. The aim of the present paper is to present the concept of an initiative called "BEO'S" as well as the experience made with the implementation und acceptance of this programme in the participating schools.

METHODS

Different from the majority of school-based projects for healthy eating and physical activity, BEO'S pursues a systemic approach that includes the whole school and is tailored to the school's respective resources. Characteristics are (1) the participation of teachers, students, parents, and caretakers, (2) the motivation and empowerment of schools to plan and implement activities by themselves, (3) the focus on environmental approaches, and (4) addressing and considering the individual school's needs and resources. The university project team supports the schools by individual counselling as well as providing information materials, trainings and workshops for teachers, an internet page, newsletters, and financial support. In the school years 2007/08 and 2008/09, BEO'S was conducted at 14 primary and secondary schools in the district of Oberfranken, Bavaria. It was extended to other schools in 2009/10. The short- and mid-term goals are the improvement of the school's environments as well as the eating behaviour and physical activity of the students. In the long run, it is intended to prevent obesity and improve the students' health and school performance.

RESULTS

The implementation processes showed that the teachers for physical education and domestic science as well as the headmasters were especially committed. The participation of the teaching staff, the students and the parents proved to be difficult, however. The schools implemented many activities for healthy eating and physical activity, but the planning process was not very systematic: needs assessment, status quo analysis, identification of successful strategies and definition of aims was difficult for the schools. The provided financial support, training programmes and workshops, and the exchange with other schools were widely used, in contrast to the offered internet-based tools. The acceptance of BEO'S was (very) good by teachers (n=97), students (n=674) and their parents (n=522). The teachers preferred the workshops and trainings to the internet page. The students appreciated the possibilities for physical activity and the emphasis on healthy eating; primary school students and girls more than secondary school students and boys. One third of the parents would like to be involved to a higher degree.

CONCLUSION

BEO'S was well received by all the people involved. Yet, there are still deficits concerning the implementation process, especially in the participation of students and parents.

[Social marketing--seduction with the aim of healthy behavior?]

SOCIAL MARKETING - SEDUCTION WITH THE AIM OF HEALTHY BEHAVIOR? Social marketing is the use of marketing principles to design and implement programs that promote socially beneficial behaviour change. Contrary to the marketing of consumption goods, social marketing does not deal with material products, but with behaviour, e. g. not smoking. This 'product' has a basic benefit (i. e. reduction of health risks in the long run), which is, however, difficult to convey. Therefore, the intended change in behaviour has to be related to a further reward which consists of symbolic goods, e. g. social appreciation or a better body feeling. The communication policy is essential for information on and motivation for the preventive issue. Social marketing campaigns whose development and management follow the principles of classical marketing can render preventive efforts more effective. In addition, social marketing can lead to a better quality management as compared to conventional preventive activities. These advantages can be explained by a) tailoring the campaign more specifically to the target group's needs and motives, b) presenting health risks more convincingly, and c) continuously analysing and evaluating the campaign and its effects. On the other hand, the marketing of preventive aims through mass media can bear several risks, as exemplified by different national and international public health campaigns. The necessity to communicate briefly and succinctly can lead to misleading simplifications and, in case of cancer screening, to the trivialization of a behaviour's consequences and adverse effects. Also, many campaigns do not intend to educate and inform, but try to persuade target persons of a certain behaviour, using emotions such as fear. This has led to social marketing being criticized as manipulation. Sometimes, social marketing campaigns cause stigma and discrimination of certain population subgroups, e. g. obese or HIV-positive people. Health promoters who plan mass media campaigns can be recommended to follow marketing principles in order to improve the campaign's impact. However, they should also consider possible adverse effects of the communication strategy on the social perception of health behavior, health risks and the responsibility of certain subgroups.

[Transparency of medical quality data. Ethical obligation to deliver or instrument to create unfair competitive advantage?]

Annually about 100,000 acute cardiac deaths occur in Germany. For this reason, there is the obvious need, from a public health perspective, to inform the population about possible measures of their prevention and treatment. Ultimately every patient or admission referring doctor can be thought of as a recipient of "marketing". Other than within the context of economics, in medicine the subject of marketing is likely to produce a negative response. Any doctor engaging in marketing is quickly considered to be engaging in unfair competition at the expense of colleagues ("economic competitors"). However, despite some reservations it would seem sensible to provide transparency concerning the results of treatment. If the manner of competition is the right one, i.e. one that has as its aim to improve patient care, it can at the same time improve such care, motivate doctors and frequently also reduce costs. Transparency of the various aspects of improved medical care in this way represent a "pay-back" to everyone working in the health services. It is desirable to establish an external process of assessing any published data and, as far as possible, exclude all incorrect data from relevant measures of comparison. Competition can then be to the patient's benefit.

[Prevention of overweight and obesity--the role of government, the food industry and the individual]

Obesity is a growing health problem in Germany and other industrial nations. There is an urgent need for action in order to stop this development. Government and food industry, as well as individuals, have to act. Governmental interventions could consist in direct regulation - as in, e. g., regulations on food offered in schools and restrictions on advertising unwholesome nutrition for children, -, or in economic incentives like taxes on unhealthy food and subsidisation of wholesome school food and information (food education, campaigns, food labelling etc.). The government should provide an environment that makes a healthy life style easy. But, at present, governmental interventions are too much focused on personal behaviour and responsibility. The role of the food industry could, for example, consist in clear food labelling and the production of healthy food. Each individual holds a personal responsibility for his or her health, but there are limits to it, like social, financial, biological, and other environmental factors. Especially social factors ought to be considered more seriously. Hence, personal responsibility should only be demanded in an adequate environment.