Percutaneous transluminal coronary angioplasty led to improved clinical outcomes in low-risk patients with acute MI
ACP J Club. 1997 Nov-Dec;127:59. doi:10.7326/ACPJC-1997-127-3-059
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Zijlstra F, Beukema WP, van't Hof AW, et al. Randomized comparison of primary coronary angioplasty with thrombolytic therapy in low risk patients with acute myocardial infarction. J Am Coll Cardiol. 1997 Apr;29:908-12.
To compare the effectiveness of primary percutaneous transluminal coronary angioplasty with thrombolytic therapy in low-risk patients with acute myocardial infarction (MI).
Randomized controlled trial with 6-month follow-up.
Center in an academic institution in the Netherlands.
95 low-risk patients (mean age 56 y, 77% men) with symptoms of MI for > 30 minutes presenting within 6 hours of symptom onset or between 6 and 24 hours if there were signs and symptoms of ongoing ischemia with ≥ 0.1 mV ST-segment elevation in > 2 leads. Patients were considered low risk if they had no contraindications for thrombolytic therapy; Killip class < 2; no electrocardiographic evidence of anterior wall infarction or of extensive nonanterior infarction defined as ≥ 8 leads with ≥ 0.1 mV ST-segment elevation or depression or both. Exclusion criteria were life expectancy < 6 months or severely impaired quality of life.
45 patients were allocated to angio-plasty and 50 to streptokinase, 1.5 million IU. All patients received heparin intravenously. Aspirin and β-blockers were given to all patients unless contraindicated.
Main outcome measures
The primary end point was death, nonfatal stroke, or reinfarction. Secondary end points were left ventricular ejection fraction and total medical charges at 6 months.
The trial was terminated earlier than planned because of the apparent benefit in the angioplasty group. The primary end point was reached in 2 patients (4.4%) in the angioplasty group compared with 10 patients (20%) in the thrombolysis group (P < 0.02) (Table). The difference primarily resulted from a higher reinfarction rate in the thrombolysis group (0% vs 16%, P < 0.01). Mortality and stroke rates were low and not statistically different in the groups. No differences existed for left ventricular ejection fraction or total medical charges.
Primary percutaneous transluminal coronary angioplasty led to improved clinical outcomes compared with thrombolytic therapy in low-risk patients with acute myocardial infarction.
Source of funding: The Netherlands Heart Foundation.
For article reprint: Dr. F. Zijlstra, Department of Cardiology, Hospital De Weezenlanden, Groot Wezenland 20, 8011 JW Zwolle, The Netherlands. FAX 38-429-91-25.
Table. Angioplasty vs thrombolysis*
|Outcome at 6 mo||Angioplasty (EER)||Thrombolysis (CER)||RRR (95% CI)||ARR |CER-EER|||NNT (CI)|
|Death, nonfatal stroke, or reinfarction||4.4%||20%||78% (16 to 94)||15.6%||7 (3 to 40)|
*Abbreviations defined in Glossary; RRR, ARR, NNT, and CI calculated from data in article.
It is still unclear which patients benefit from primary angioplasty as a treatment for acute MI. In the report by Stone and colleagues, more clinical benefit is derived in high-risk patients. However, Zijlstra and colleagues also report benefit in low-risk patients. Although the numbers in the latter study were small, reinfarction occurred in 16% and more patients reached the combined primary end point after thrombolytic therapy than after primary angioplasty. Reinfarction rates were higher than in most previous studies, which is possibly related to chance in this relatively small investigation. Benefits associated with angioplasty were derived from lower re-infarction rates without statistically significant differences in mortality rates.
Although the use of primary angioplasty seemed to have no extra cost, it can be debated whether the use of this procedure to prevent reinfarction (but with no difference in mortality) is justified, considering the resources required for its widespread use. Perhaps a more cost-conscious way would be to carefully assess patients after thrombolysis and to consider intervention in those who fail to reperfuse (1, 2), so-called rescue angioplasty. Although the clinical criteria used for reperfusion may lack a high positive predictive value, it is clear that 20% to 30% of patients do not have Thrombolysis in Myocardial Infarction (TIMI) grade 2 or 3 perfusion and up to 40% do not achieve grade 3. Careful evaluation of the efficacy of the thrombolytic agent in each individual patient is currently widespread in clinical practice. Full use of early angioplasty in those who seem not to have reperfused could have led to early transfer of high-risk patients who were most likely to benefit in terms of mortality and morbidity to facilities equipped for angioplasty. This strategy of careful early evaluation for failure to reperfuse and invasive management in a targeted group could lead to increased acceptance of a role for angioplasty as a treatment for acute MI.
The cost-effectiveness of primary angioplasty compared with thrombolysis for acute MI remains a contentious issue. It has been fairly well established that, at least in relatively selected patients, primary angioplasty ensures TIMI grade 3 flow in a higher proportion of patients than can currently be achieved with the best thrombolytic therapy. Better TIMI flow has been shown to correspond to improvement in short- and long-term outcomes (3). It is less clear whether the results reported in the PAMI trial can be reproduced in most clinical settings and at what true cost. Should the goal of obtaining the best patency be paramount and, if so, how many balloons, stents, or newer agents, such as ReoPro (Centocor, Malvern, PA), will be required? Although these issues are the subject of ongoing studies, the trial by Stone and colleagues suggests that the outcome benefits have no additional cost; however, some issues that surround the data presented warrant cautious interpretation.
First, it is uncertain whether the high patency rates achieved by angioplasty in the PAMI study can be consistently attained if the technique becomes more widely used by less-skilled operators. Second, readers really want to know what the cost is, not what is charged. The authors acknowledge this potentially serious shortcoming in the discussion section of their paper. Finally, the extra cost of thrombolysis primarily resulted from the need for repeated catheterization and subsequent nonprotocol angioplasty and coronary surgery. Can we be sure that all these further interventions were done according to protocol and not under the pressures physicians may feel to provide a treatment initially denied by randomization in the trial? One important potential resource saving is the shortening of the hospital stay for patients known to have TIMI 3 flow in all arteries after angioplasty.
In the many clinical settings, primary angioplasty may cost more than is suggested by these studies because the start-up costs for new interventional catheter laboratories and the provision of personnel for 24-hour coverage must be included. These substantial funding requirements are likely to limit wide dissemination of primary angioplasty. Also, new trials will need to address improvements in angioplasty techniques as well as in pharmacologic therapies for acute MI (new thrombolytic agents and adjunctive therapies vs stents and ReoPro). Transfer of patients most likely to benefit from intervention may be the preferable option, at least in the short term, but it must be stated that this has not been shown in trials. In the meantime, in situations in which primary angioplasty is available, these studies show that it is a credible clinical option.
A. H. Gershlick, MD
University of LeicesterLeicester, England, UK