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Cost-effectiveness of transesophageal echocardiographic-guided cardioversion: a decision analytic model for patients admitted to the hospital with atrial fibrillation |
Seto T B, Taira D A, Tsevat J, Manning W J |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Transesophageal Echocardiographic (TEE)-guided cardioversion as a method for early cardioversion of patients with atrial fibrillation.
Study population A hypothetical prototypic 70-year-old patient admitted to the hospital for initial treatment of atrial fibrillation of more 2 days in duration and for whom elective cardioversion is needed. This excludes patients with atrial fibrillation not admitted to hospital or those who spontaneously revert to sinus rhythm.
Setting Hospital. The study was carried out in Massachusetts and Ohio, USA.
Dates to which data relate The effectiveness data were obtained from studies published in 1992 and 1995. The resource use and cost data corresponded to 1992 and 1993. The price year was 1993.
Source of effectiveness data The estimates for the probability of haemorrhage of a thrombus detected in patients with atrial fibrillation and the probability of stroke after cardioversion, the annual disease-specific mortality of patients in chronic atrial fibrillation and receiving warfarin therapy relative to those not on anticoagulation therapy were derived from a review of previously completed studies.
Modelling A decision analytic model was used to estimate costs and benefits. The model incorporated thehealth states associated with each of the three treatment choices analysed during a period of 2 months, after which the survival was modelled using the Declining Exponential Approximation of Life Expectancy (DEALE) method. The events and end points included in the analysis were the presence or absence of clinical thromboembolism after initial treatment strategy (in cases 2 and 3 above), the detection of left atrial clot (after initial strategies 2 and 3 and sequentially for those cases in which a clot was found and after the corresponding 4 weeks of warfarin therapy) and the incidence of haemorrhage after anticoagulation and stroke at cardioversion.
Outcomes assessed in the review The probability of a thrombus detected in patients with atrial fibrillation and the probability of stroke after cardioversion were the main outcomes assessed in the review. Also, the annual disease-specific mortality of patients in chronic atrial fibrillation and receiving warfarin therapy relative to those not on anticoagulation therapy was assessed.
Study designs and other criteria for inclusion in the review Seven studies were not associated with any particular design. The other studies included one 'prospective 4.5 year' study, a 'randomized pilot' study, one randomized placebo-controlled trial, one nonrandomized prospective study, and three retrospective studies.
Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Fourteen studies were included in the review. For the diagnostic outcomes, 4 studies were used, whilst for the effects of cardioversion on stroke outcomes, 7 studies were included (two of which were already included in the previous set). The effectiveness of anticoagulation therapy in turn was derived from five studies.
Methods of combining primary studies Primary studies were not combined except for the estimate of 'risk of stroke after cardioversion among patients without evidence of atrial thrombi on TEE', which was obtained from prospective data from three trials using a protocol similar to strategy 2 (studies were used to analyse ranges reported in sensitivity analyses).
Investigation of differences between primary studies Results of the review The haemorrhage rates were 0.8% to 2.5% year. TTE, and TEE detect thrombi in 2% and 15% of patients presenting with atrial fibrillation. For those cases with negative TTE, TEE detects thrombi in 14%. The probability of a persistent thrombus with TEE at 1 month follow-up was 15%. The risk of stroke after 1 month of anticoagulation was 0.8%. The risk of stroke after cardioversion among patients without atrial thrombi found on TEE was 0.5% (relative risk of 0.625). The annual disease specific mortality rate for patients in chronic atrial fibrillation and receiving long-term warfarin therapy was 0.027 against the corresponding rate for those same patients not receiving warfarin therapy, which was 0.043.
Measure of benefits used in the economic analysis Quality adjusted life years (QALYs). The utility values were derived from published data.
Direct costs Costs were discounted and some quantities of resource use were reported separately from the costs. The costs measured were those associated with operating and capital costs and costs of complications (stroke included) for the hospital with the outpatients costs included. The costs associated with each strategy were derived from the model. The source of unit costs was a study published in 1992 and actual cost estimates at the authors' institution. The price year was 1993 and all prices were adjusted to this price base by using the medical care component of the consumer price index. The quantity/cost boundary adopted was the hospital.
Sensitivity analysis One- and two-way sensitivity analyses were used to study the effects on the results of the variability in the probabilities of thromboembolism, haemorrhage, complications of TEE, unit costs and utilities. A threshold analysis was also used to describe the critical values of parameters above or below which the strategies turned out to be less desirable in economical terms.
Estimated benefits used in the economic analysis The TEE-guided cardioversion strategy turned out to be associated with 8.49 QALYs, whilst the TEE-guided cardioversion with TTE strategy had 8.48 QALYs. The conventional strategy was associated with 8.48 QALYs. These results were obtained after discounting of benefits at an annual rate of 5%.
Cost results By using a 5% annual discount rate, the total cost of TEE-guided cardioversion was $2,774, whilst the TEE-guided cardioversion with TTE strategy and the conventional strategy had costs of $3,106 and $3,070, respectively.
Synthesis of costs and benefits Costs and benefits were not combined since TEE-guided cardioversion was the dominant strategy. The sensitivity analysis focused on the TEE-guided cardioversion strategy relative to the conventional strategy only, since the TEE-guided cardioversion with TTE strategy was always dominated by the former option. The results were relatively insensitive to the estimates of morbidity from TEE, cost of TTE, cost of hospital admissionfor cardioversion, and utilities associated with the different health states. If the relative risk (RR) of stroke was less than 0.56 then TEE-guided cardioversion was more effective than conventional therapy, even if the risk of first-month haemorrhage was as low as 0.2. On the other hand, if the RR of stroke after cardioversion was more than 4.7 (0.625 at baseline), then conventional therapy was more effective, even with a first-month haemorrhage risk equivalent to 2.4% (0.32% at baseline).
Authors' conclusions The study showed that TEE-guided early cardioversion, without initial TTE is a reasonable and potentially cost-saving alternative to current conventional therapy for patients admitted to the hospital with new atrial fibrillation. Sensitivity analysis showed that these conclusions are dependent on the risk of cardioversion-related thromboembolism after negative TEE being slightly lower than the risk associated with conventional therapy. By avoiding 1 month of anticoagulation, the TEE approach also appears particularly beneficial for those with an increased risk of haemorrhagic complications.
CRD COMMENTARY - Selection of comparators The reason for the choice of comparators is clear. The administration of three to four weeks of warfarin therapy (for prophylaxis during recovery of atrial mechanical function) before and after cardioversion was reported as the conventional therapy for patients presenting with atrial fibrillation of more than 48 hours duration. You, as a user of this database, should consider whether these are widely used health technologies in your own setting.
Validity of estimate of measure of benefit The internal validity of the study results cannot be properly assessed without additional information regarding the methodology used in the literature review. It should be noted that the utility values were derived from the literature.
Validity of estimate of costs The cost analysis implicitly provided some quantities of resource use, with adequate details of the methods of cost estimation being provided.
Other issues The conclusions were justified in terms of the sensitivity analysis. The authors made clear that the study results are not generalisable to patients with atrial fibrillation not admitted to the hospital or those who spontaneously revert to sinus rhythm.
Implications of the study Further studies are needed in order to support the results found in this study, which pointed to the desirability of carrying out clinical studies of the TEE option, without initial TTE, for patients admitted to hospital with atrial fibrillation.
Source of funding Dr Manning is supported in part by the Edward Mallinckrodt Jr Foundation, Saint Louis, Missouri.
Bibliographic details Seto T B, Taira D A, Tsevat J, Manning W J. Cost-effectiveness of transesophageal echocardiographic-guided cardioversion: a decision analytic model for patients admitted to the hospital with atrial fibrillation. Journal of the American College of Cardiology 1997; 29(1): 122-130 Indexing Status Subject indexing assigned by NLM MeSH Aged; Anticoagulants /therapeutic use; Atrial Fibrillation /economics /therapy; Cerebrovascular Disorders /epidemiology /prevention & Cost-Benefit Analysis; Costs and Cost Analysis; Decision Support Techniques; Echocardiography /economics; Echocardiography, Transesophageal /economics; Electric Countershock /economics /methods; Female; Heart Diseases /ultrasonography; Hemorrhage /chemically induced /epidemiology; Humans; Male; Quality-Adjusted Life Years; Risk Factors; Sensitivity and Specificity; Thrombosis /ultrasonography; Time Factors; Warfarin /therapeutic use; control AccessionNumber 21997000193 Date bibliographic record published 28/02/1999 Date abstract record published 28/02/1999 |
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