PTCA IMPROVES COMPLICATION RATES, VESSEL PATENCY COMPARED TO STREPTOKINASE AND ACTIVASE (TPA), STUDIES SHOW; PTCA SEEN AS "PREFERABLE" FOR HIGH-RISK PATIENTS

Executive Summary

Use of percutaneous transluminal coronary angioplasty to treat acute myocardial infarction reduces mortality and other complications and improves vessel patency compared to the thrombolytic agents streptokinase and tissue plasminogen activator, two studies in the March 11 New England Journal of Medicine find. The first study, conducted by Felix Zijlstra, Ziekenhuis de Weezenlanden, Zwolle, The Netherlands, et al. compared clinical outcomes of 142 patients randomly assigned to receive either PTCA or streptokinase. Of 70 patients assigned to the angioplasty group, 65 underwent the procedure; the other five were deemed unsuitable for PTCA. Seventy-two patients received streptokinase therapy. Vessel patency was achieved in 68% of patients in the streptokinase group (49 patients) and 91% of patients in the PTCA group (64 patients). In addition, "quantitative coronary angiography revealed stenosis of 36% ( 20%) of the luminal diameter in the angioplasty group, as compared with 76% ( 19%) in the streptokinase group." Thirty-eight percent of the patients (27) in the streptokinase group experienced recurrent ischemia, compared to 9% (six) in the angioplasty group. Reinfarction occurred in 12.9% of streptokinase patients (nine) and in none of the PTCA group. Death occurred in 6% (four) of the streptokinase patients and in none of the PTCA patients. As measured by ejection fraction, left ventricular function at rest was 45% ( 12%) in the streptokinase group and 51% ( 11%) in the angioplasty group. Similar ejection fraction rates were obtained when measured during exercise. Zijlstra et al. conclude: "Immediate angioplasty after acute myocardial infarction was associated with a higher rate of patency of the infarct-related artery, a less severe residual stenotic lesion, better left ventricular function, and less recurrent myocardial ischemia and infarction than was intravenous streptokinase." A second study published in the same issue of the NEJM compared immediate angioplasty to Genentech's Activase (tissue plasminogen activator or tPA) and drew similar conclusions. Results of the study, conducted by Cindy Grines, MD, William Beaumont Hospital, Royal Oak, Michigan, et al., were reported at an American Heart Association meeting in November 1992 ("The Gray Sheet" Nov. 30, p. 16). Grines et al. compared clinical outcomes of 395 patients randomly assigned to receive either immediate PTCA (195 patients) or tPA therapy (200 patients). Of the 195 patients assigned to the PTCA group, 175 underwent the procedure; the other 20 were deemed unsuitable candidates for the treatment. Both groups received "conservative care" following treatment, with followup conducted after six months. The study found an in-hospital death rate of 2.6% (five patients) in the PTCA group, compared to 6.5% (13 patients) in the tPA group, with statistical significance at the p = .06 level. The mortality benefit of immediate PTCA "was seen mainly among patients who were classified as 'not [at] low risk' of death," Grines et al. comment. For these high-risk patients, the mortality rate was 2% (two patients) in the PTCA group and 10.4% (11 patients) in the tPA group. Recurrent ischemia (including infarction) occurred in 20 PTCA- treated patients (10.3%), compared to 56 patients in the tPA group (28%, p = .02). Intracranial hemorrhage rates also were lower in the PTCA group than the tPA group (0% versus 2%, respectively). Regarding left ventricular function, exercise testing "was clinically positive in 8.6% of the patients in the tPA group and 2.9%" in the PTCA group; reversible defects in the infarct zone were evident on thallium scanning in 38.2% and 26.8% of tPA and PTCA patients, respectively. Six-month followup testing with radionuclide ventriculography "did not differ significantly" between the two groups, Grines et al. report. The authors conclude that the potential benefits of immediate angioplasty outweigh the possible risks. "When the necessary facilities and personnel are available, immediate angioplasty is an attractive alternative to intravenous thrombolysis and may even be preferable for high-risk patients." A third study in the March 11 NEJM, by Raymond Gibbons, MD, Mayo Clinic and Foundation, Rochester, Minnesota, et al., compared PTCA to tPA therapy using myocardial salvage as an end point. Myocardial salvage is an indicator of the amount of tissue damage associated with PTCA and tPA. In cases of anterior infarction, salvage was 27% ( 21%) of the left ventricle in the tPA group compared with 31% (21%) in the PTCA group. For infarcts in other locations, the myocardial salvage rates were 7% (13%) in the tPA group and 5% (10%) in the PTCA group. Based on results of their 108-patient study, Gibbons et al. conclude that "immediate angioplasty does not appear to result in greater myocardial salvage than the administration of a thrombolytic agent followed by conservative treatment, although a small difference between these two therapeutic approaches cannot be excluded." Gibbons et al. also compared the cost of PTCA to tPA therapy. Although significantly lower six-month followup costs, numbers of initial hospital days and numbers of readmissions were observed in the angioplasty group, there was "no significant difference in hospital cost or overall cost," the investigators state. In an accompanying editorial on the three studies, Richard Lange, MD, and David Hillis, MD, University of Texas Southwestern Medical Center, Dallas, comment that the study results indicate that immediate angioplasty should "now be the standard of care" for "a minority of patients" with myocardial infarctions. Myocardial infarction treatment traditionally "seemed attainable with conservative management and without the need for invasive [PTCA] procedures," the commentators note. However, in light of the new study results, "the pendulum now appears to be swinging in the opposite direction" towards use of angioplasty. Patients who may particularly benefit from immediate angioplasty are those with a contraindication to thrombolytic therapy and high-risk patients, Lange and Hillis state. In addition, "since thrombolytic therapy seems to be ineffective in improving survival among patients with cardiogenic shock or sustained hypotension, immediate angiography and angioplasty should be considered in these patients." Conversely, "low-risk patients are likely to do well with either immediate angioplasty or thrombolytic therapy," Lange and Hillis say. They add: "Additional studies should identify more clearly the subgroups likely to gain the most benefit from immediate angioplasty." Lange and Hillis point out that the "strategy of immediate angioplasty for acute myocardial infarction has limited applicability because of the severely restricted accessibility of the procedure." Only 18% of the hospitals in the U.S. have the capability of performing angioplasty, and "even fewer can do it on an emergency basis." They conclude: "The modest long-term benefits and monetary savings...do not justify the huge expense of making angioplasty universally available."