Type of intervention Secondary prevention. Economic study type Cost-effectiveness analysis.

Transcription

1 Economic implications of the prophylactic use of intraaortic balloon counterpulsation in the setting of acute myocardial infarction Talley J D, Ohman E M, Mark D B, George B S, Leimberger J D, Berdan L G, Davidson-Ray L, Rawert M, Lam L C, Phillips H R, Califf R M 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 Intraaortic balloon counterpulsation (IABP) was used as a prophylactic, within 24 hours and continued for 48 hours, in patients who had suffered acute myocardial infarction. This was compared with standard care without the use of IABP unless this was required because of adverse haemodynamic or ischemic events. Type of intervention Secondary prevention. Economic study type Cost-effectiveness analysis. Study population Patients who had suffered acute myocardial infarction followed by emergency angiography and either primary angioplasty, rescue angioplasty after thrombolysis, intravenous thrombolytic therapy or repeat contrast injection. Patients with haemodynamic instability requiring IABP use were excluded as were those with severe peripheral vascular disease, contraindications to extended intravenous heparin therapy, or IRA patency at acute angiography. Setting Hospital. The original clinical study was carried out at 11 hospitals in the USA. The economic study was based on a subset in which costing was carried out at 3 centres: Duke University Medical Center, Durham, North Carolina; Riverside Methodist Hospital, Columbus, Ohio; and The University of Louisville Affiliated Hospitals, Louisville, Kentucky. Dates to which data relate Clinical data from a study published in 1994 were used. Actual dates for the collection of data were not given. Resource use data were collected from a subset of the clinical records and therefore were based on the same dates. Dates of prices were not given, but were based on hospital billing records at the time. Source of effectiveness data Evidence for final outcomes was based on a single study. Link between effectiveness and cost data Costing was based on a subset of the sample used in the effectiveness study. This subset consisted of 56% of the total patients enrolled at three of the eleven centres. Costing was undertaken retrospectively. Page: 1 / 5

2 Study sample 182 patients who had emergency cardiac catheterization within 24 hours of acute myocardial infarction were enrolled in the study. Patients were randomised at the end of the catheterization and/or angioplasty to receive 48 hours of IABP therapy (n = 96) or standard care (n = 86). Details of sample selection, sample size, percentage of refusals and numbers excluded were not given. In the clinical study, the median age was 55 years and 137 of 182 (75%) were men. Of the 102 patients in the economic study subset, 52 were in the IABP group and 50 in the control group. In the IABP group 40 (77%) were male with a median age of 56 years. In the subset studied in the costing the median age was 55 and 75 of 102 (74%) were male. Baseline clinical characteristics of those in the subset and those excluded were given. Study design This study was a multi-centred, randomised controlled trial carried out at 11 sites. Follow-up was for the duration of hospital stay and the primary end point was reocclusion (TIMI grade 0 or 1 flow) of the previously patent (TIMI grade 2 or 3) IRA at 5 to 7 day repeat angiography. Analysis of effectiveness It was not stated whether the analysis was based on intention to treat. Outcomes were given for the patients not included in the subset, for the total subset group and for the IABP and control groups within the subset. Outcomes were given for death, stroke, recurrent ischemia, reinfarction, emergency repeat angioplasty, emergency or urgent bypass, and reocclusion of IRA. Subset patients more often had multiple disease (52% versus 39%, p=0.08) and the right coronary artery as the IRA (52% versus 33%, p=0.05). They had primary angioplasty for acute myocardial infarction less often (51% versus 68%, p=0.024) and needed vascular repair or thrombectomy less often (1% versus 8%, p=0.045). They had the same rate of rescue angioplasty for failed thrombolysis (28%). There were no significant differences in baseline characteristics between the IABP and control groups in the subset. Effectiveness results The authors stated that the randomised IABP trial showed that prophylactic aortic counterpulsation increases sustained coronary artery patency when used for 48 hours. IABP also reduced ischemic events after cardiac catheterization, including the need for repeat emergency angioplasty. In the subset there was less recurrent ischemia in the IABP group (3 cases, 5.8%) than in the control group (12 cases, 24%). There were no significant differences in the other outcomes: death, IABP = 2 (3.8%), control = 1 (2.0%); stroke, IABP = 1 (1.9%), control = 1 (2.0%); reinfarction, IABP = 2 (3.8%), control = 6 (12%); emergency repeat angioplasty, IABP = 1 (1.9%), control = 4 (8.0%); emergency or urgent bypass, IABP = 2 (3.8%), control = 0; reocclusion of IRA, IABP = 6 (12%), control = 10 (20%). Higher rates of vascular or haemorrhagic complications were considered as possible side effects, but no difference was detected: deep venous thrombosis, IABP = 0, control = 1 (2%); vascular repair or thrombectomy, IABP = 1 (1.9%), control = 0; severe haemorrhage, both groups 0. Page: 2 / 5

3 Clinical conclusions The prophylactic use of IABP in patients at high risk of infarct artery reocclusion provides sustained clinical benefit. Measure of benefits used in the economic analysis The outcomes measured were: death, stroke, recurrent ischemia, reinfarction, emergency repeat angioplasty, emergency or urgent bypass and reocclusion of IRA. Clinical benefit would result from a reduction of any of these. The length of follow up was the length of hospital stay (median of 8 days for all groups). Side effects were not considered relevant in the economic analysis. Direct costs The viewpoint was the hospital. Hospital costs were assessed using hospital billing data and correction factors to convert charges to costs. Total index hospital costs (admission to discharge) included all diagnostic and therapeutic procedures, but fees and costs after discharge were not included. Statistical analysis of costs Costs were summarised as means (+/- SD) and medians plus the 25th and 75th percentile. The Wilcoxon rank-sum test was used to test the statistical significance of differences and a p value less than 0.05 was taken to indicate statistical significance. Indirect Costs These were not considered. Currency US dollars ($). Sensitivity analysis No sensitivity analysis was performed. Estimated benefits used in the economic analysis The authors stated that the randomised IABP trial showed that prophylactic aortic counterpulsation increases sustained coronary artery patency when used for 48 hours. IABP also reduced ischemic events after cardiac catheterization, including the need for repeat emergency angioplasty. In the subset, there was less recurrent ischemia in the IABP group (3 cases, 5.8%) than in the control group (12 cases, 24%). There were no significant differences in the other outcomes: death, IABP = 2 (3.8%), control = 1 (2.0%); stroke, IABP = 1 (1.9%), control = 1 (2.0%); reinfarction, IABP = 2 (3.8%), control = 6 (12%); emergency repeat angioplasty, IABP= 1 (1.9%), control = 4 (8.0%); emergency or urgent bypass, IABP = 2 (3.8%), control = 0; reocclusion of IRA, IABP = 6 (12%), control = 10 (20%). Cost results Page: 3 / 5

4 There were no statistically significant differences in total costs although there was a statistically significant difference in the cost of supplies. Total costs for the IABP group were (mean +/- SD) $22,357 (+/- 14,369), and for the control group were $19,211 (+/-8,414), (p=0.45). Supplies for the IABP group were $2,273 (+/-2,177) and for the control were $1,328 (+/- 938), (p=0.0005). There were no significant differences in the costs of the following categories; catheterization, laboratory, intensive/coronary units, monitored/unmonitored beds, or pharmacy. Synthesis of costs and benefits No synthesis was carried out because the intervention was the dominant strategy. Authors' conclusions The prophylactic use of IABP in patients at high risk of infarct artery reocclusion within 24 hours of acute myocardial infarction provides sustained clinical benefit without substantially increasing hospital costs. Limitations to the study were: (1) costs were collected from only 3 centres; and (2) the power of the study to distinguish small cost differences was limited because of low numbers. CRD COMMENTARY - Selection of comparators The reason for the choice of comparator is clear. Validity of estimate of measure of benefit The estimate of benefit in this study tends to be unclear because findings are taken from a subset, rather than from the findings of the main study. Claims are reiterated regarding clinical benefits, but unfortunately without re-presenting the evidence. Further, there are instances where data from the subset do not support all the claims and using the subset may have compromised the validity of the selection and randomisation methods. Validity of estimate of costs Quantities and prices were not presented, although the categorisation of costs was adequate. The absence of dates and prices makes it difficult to generalise costs. Other issues The authors' conclusions are unlikely to be justified based on the clinical data presented from the subset. A better and more valid case may have been to use the complete clinical data with costs taken only from the subset, even though the small numbers in the subset reduce the power of the study to distinguish small differences in costs. Source of funding None stated. Bibliographic details Talley J D, Ohman E M, Mark D B, George B S, Leimberger J D, Berdan L G, Davidson-Ray L, Rawert M, Lam L C, Phillips H R, Califf R M. Economic implications of the prophylactic use of intraaortic balloon counterpulsation in the setting of acute myocardial infarction. American Journal of Cardiology 1997; 79(5): PubMedID Other publications of related interest Ohman E M, George B S, White C J et al. Use of aortic counterpulsation to improve sustained coronary artery patency during acute myocardial infarction. Results of a randomized trial. Circulation 1994;90: Page: 4 / 5

5 Powered by TCPDF ( Indexing Status Subject indexing assigned by NLM MeSH Aged; Cerebrovascular Disorders /economics; Coronary Angiography /economics; Coronary Vessels /pathology; Death, Sudden, Cardiac; Emergencies; Female; Hospital Charges; Hospital Costs; Hospitalization /economics; Humans; Intra- Aortic Balloon Pumping /economics; Male; Medicare /economics; Middle Aged; Myocardial Infarction /economics /therapy; Myocardial Ischemia /economics /prevention & control; Myocardial Revascularization /economics; Recurrence; Risk Factors; Treatment Outcome; United States; Vascular Patency AccessionNumber Date bibliographic record published 31/08/1999 Date abstract record published 31/08/1999 Page: 5 / 5