TY - JOUR
T1 - Myocardium at risk and infarct size after thrombolytic therapy for acute myocardial infarction
T2 - Implications for the design of randomized trials of acute intervention
AU - Gibbons, Raymond J.
AU - Christian, Timothy F.
AU - Hopfenspirger, Mona
AU - Hodge, David O.
AU - Bailey, Kent R.
N1 - Funding Information:
Front the Division of Cardikwmcular Diseases and Internal Medicine and the Section of Medical Research Statistics, Mayo Clinic, Rochester, Minnesota . This study was supported by grants from Burroughs Wellcome, Research Triangle Park. North Carolina: and DuPont Merck Pharmaceutical Co ., North Billerica, and C. R. Bard, Billerica, Massachusetts. Manuscript received November 21190-1 . revised manuscript received March 28. 1994. accepted March 13, 1941. Address for correspotdencg: Dr. Raymond J. Gibbons, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905 .
PY - 1994/9
Y1 - 1994/9
N2 - Objective. The purpose of this study was to estimate the effect of an improved reperfusion therapy for acute myocardial infarction on myocardial salvage find ventricular function for anterior and inferior infarctions and to ascertain the sample size required to detect such an effect. Background. There are significant differences in myocardium at risk between anterior and inferior infarctions that affect the benefit of reperfusion therapy. Methods. We studied 58 patients with acute myocardial infarction (24 anterior, 34 inferior) treated with intravenous recombinant tissue-type plasminogen activator and angioplasty when necessary. Tomographic imaging with technetium-99m sestamibi was performed to measure myocardium at risk, final infarct size and myocardial salvage and to estimate the beneficial effects of an improved therapy. Results. A new therapy that was 30% more effective than existing therapy (with respect to salvage) would increase salvage (and reduce mean infarct size) by 5.2% of the left ventricle and increase late ejection fraction by only 0.012 (95% confidence interval [CI] 0.009 to 0.015) in inferior infarction and by 0.038 (95% CI 0.027 to 0.047) in anterior infarction, if anterior and inferior infarctions occurred with equal frequency, a sample size of 140 patients in each treatment group would be required to detect such a change with 80% power. In a trial of inferior infarctions alone, a sample size of 236 patients in each treatment group would be required compared with only 98 patients in a trial of anterior infarctions alone. Conclusions. The anticipated mean benefit from an improved reperfusion therapy in individual patients with inferior infarction is very small and of questionable clinical significance. The anticipated benefit in anterior infarction is greater and easier to detect. Future randomized trials should be stratified for infarct location and should consider the greater absolute benefit of treatment in anterior infarction.
AB - Objective. The purpose of this study was to estimate the effect of an improved reperfusion therapy for acute myocardial infarction on myocardial salvage find ventricular function for anterior and inferior infarctions and to ascertain the sample size required to detect such an effect. Background. There are significant differences in myocardium at risk between anterior and inferior infarctions that affect the benefit of reperfusion therapy. Methods. We studied 58 patients with acute myocardial infarction (24 anterior, 34 inferior) treated with intravenous recombinant tissue-type plasminogen activator and angioplasty when necessary. Tomographic imaging with technetium-99m sestamibi was performed to measure myocardium at risk, final infarct size and myocardial salvage and to estimate the beneficial effects of an improved therapy. Results. A new therapy that was 30% more effective than existing therapy (with respect to salvage) would increase salvage (and reduce mean infarct size) by 5.2% of the left ventricle and increase late ejection fraction by only 0.012 (95% confidence interval [CI] 0.009 to 0.015) in inferior infarction and by 0.038 (95% CI 0.027 to 0.047) in anterior infarction, if anterior and inferior infarctions occurred with equal frequency, a sample size of 140 patients in each treatment group would be required to detect such a change with 80% power. In a trial of inferior infarctions alone, a sample size of 236 patients in each treatment group would be required compared with only 98 patients in a trial of anterior infarctions alone. Conclusions. The anticipated mean benefit from an improved reperfusion therapy in individual patients with inferior infarction is very small and of questionable clinical significance. The anticipated benefit in anterior infarction is greater and easier to detect. Future randomized trials should be stratified for infarct location and should consider the greater absolute benefit of treatment in anterior infarction.
UR - http://www.scopus.com/inward/record.url?scp=0028040573&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028040573&partnerID=8YFLogxK
U2 - 10.1016/0735-1097(94)90005-1
DO - 10.1016/0735-1097(94)90005-1
M3 - Article
C2 - 8077529
AN - SCOPUS:0028040573
SN - 0735-1097
VL - 24
SP - 616
EP - 623
JO - Journal of the American College of Cardiology
JF - Journal of the American College of Cardiology
IS - 3
ER -