Economic evaluation in the field of cardiology: theory and practice.

Economic evaluations figure largely in health care. Economic evaluation aims at offering structured information about the balance between costs and effects of a intervention in comparison to another intervention. Four basic types of economic evaluation studies exist: cost-minimization analysis, cost-effectiveness analysis, cost-utility analysis, and cost-benefit analysis. In deciding which types of evaluation should be used in the analysis, the aim of the analysis is determinative. This article illustrates the theory of economic evaluation and concentrates on its use within cardiology. Finally, this article describes the project "Appropriate Medical Care," a project developed by the Royal Dutch Medical Association. In this project results from cost-effectiveness analysis will be taken into consideration in forming guidelines for the treatment of coronary artery diseases.

Coronary artery disease: arterial remodelling and clinical presentation.

OBJECTIVE: To investigate the hypothesis that in coronary artery disease large plaques in compensatorily enlarged segments are associated with acute coronary syndromes, whereas smaller plaques in shrunken segments are associated with stable angina pectoris. METHODS: Patients selected for percutaneous transluminal coronary angioplasty (PTCA) were divided into two groups, one with stable angina pectoris (stable group, n = 37) and one with unstable angina or postmyocardial infarction angina of the infarct related artery (unstable group, n = 32). In both groups, remodelling at the culprit lesion site was determined by intravascular ultrasound before the intervention. Remodelling was calculated as relative vessel area: [vessel area culprit lesion site / mean vessel area of both proximal and distal reference sites] x 100%. Compensatory enlargement was defined as remodelling of >/= 105%, whereas shrinkage was defined as remodelling of

[Economic evaluation of cardiology; background and application]. / Economische evaluatie binnen de cardiologie; achtergrond en toepassing.

Effectiveness research is increasingly attracting the attention not only of policy makers but also of the medical profession. Economic evaluation may provide structured information about the cost-effect balance of an intervention as compared with that of a different intervention. Costs can be subdivided into direct and indirect medical costs and direct and indirect non-medical costs. Effects are preferably expressed in life years gained (corrected for quality). A cost-effectiveness ratio indicates the additional costs per additional life year gained (corrected for quality). Economic evaluation can be performed using local, national or international research data. It may use studies that have been completed or in which the economic evaluation is included. A (planned) subgroup analysis may help to define a group of patients for whom the cost-effectiveness ratio is most favourable. The duration of a randomized clinical trial is usually relatively brief; with the aid of a mathematical model it is possible to collect the available information and to calculate extrapolations for longer periods.

Shrinkage of human coronary arteries is an important determinant of de novo atherosclerotic luminal stenosis: an in vivo intravascular ultrasound study.

OBJECTIVE: To assess the occurrence of arterial remodelling types and its relation with the severity of luminal stenosis in atherosclerotic coronary arteries. PATIENTS AND METHODS: Twenty one de novo coronary lesions of 20 patients, who were scheduled for percutaneous transluminal coronary angioplasty (PTCA), were investigated with intravascular ultrasound before PTCA. Local arterial remodelling at the lesion site was studied by measuring the cross sectional area circumscribed by the external elastic lamina (EEL) relative to the reference site: (EEL area lesion/reference EEL area) x 100%. Three groups were defined. Group A: relative EEL area of less than 95% (shrinkage), group B: relative EEL area between 95% and 105% (no remodelling), group C: relative increase in EEL area of more than 105% (compensatory enlargement). RESULTS: All three types of remodelling were observed at the lesion site: group A (shrinkage) n = 8, group B (no remodelling) n = 5, group C (compensatory enlargement) n = 8. The mean (SD) relative EEL area at the lesion site in group A and C was 83(9)% and 132(30)%, respectively. In group A, 33% of the luminal area stenosis at the lesion site was caused by shrinkage of the artery. In contrast, group C showed that 87% of the plaque area did not contribute to luminal area stenosis because of compensatory arterial enlargement. CONCLUSIONS: These results show that both compensatory enlargement and paradoxical shrinkage occurs in the atherosclerotic coronary artery. Next to plaque accumulation, the type of atherosclerotic remodelling is an important determinant of luminal narrowing.