GUEST LECTURES IN BRIEF

REPERFUSION STRATEGIES IN ACUTE MYOCARDIAL INFARCTION

Issam Moussa, MD, FACC
Director, Interventional Cardiology Research,
Lenox Hill Heart and Vascular Institute, New York, New York, USA

     References

   Significant progress has been made in the treatment of patients with acute ST-segment elevation myocardial infarction (STEMI) during the past decade, but 1 in 10 patients still die of this disease1.  Conceptually, there are three basic steps that contribute to reduced mortality of these patients: early diagnosis, aspirin administration, and rapid reperfusion.  Infarct-related artery reperfusion can be achieved either pharmacologically with thrombolytic therapy or mechanically with percutaneous coronary intervention (PCI). 

   Several prospective, controlled randomized clinical trials comparing thrombolytic therapy with placebo in patients with STEMI, demonstrated that thrombolytic therapy resulted in better left ventricular function and decreased mortality compared with placebo2.  Despite the efficacy of thrombolytic therapy and its ease of use, it has real limitations compared to primary PCI: 1)  Many patients who present with STEMI do not receive thrombolytic therapy due to relative or absolute contraindications or other reasons3; 2) the incidence of intracranial hemorrhage ranges from 0.6% to 1.4% of patients and it primarily affects elderly patients2,3; 3) normal blood flow in the infarct related artery is restored in only about half of patients receiving thrombolytic therapy4; 4) 30% of patients receiving thrombolytic therapy re-occlude the infarct related artery and consequently experience re-infarction within the subsequent 3 months5.  A recent meta-analysis of 23 published randomized controlled clinical trials of thrombolytic therapy vs. primary PCI6 demonstrated that primary PCI was more effective than thrombolytic therapy in reducing short-term and long-term major adverse clinical events, including death.  It was also associated with better clinical outcomes regardless of the type of thrombolytic agent used or whether the patient required emergent transfer to another hospital for primary PCI.

   When primary PCI is chosen for infarct-related artery reperfusion, stent implantation results in reduced restenosis and reocclusion rates during the ensuing 6 months but does not reduce mortality compared to stand alone balloon angioplasty7.  In another study, the platelet GP IIb/IIIa inhibitor abciximab was evaluated in determining whether its administration at the time of primary PCI improved outcomes8.  Abciximab administration reduced subacute thrombosis, recurrent ischemia, and repeat revascularization procedures during the first month after primary PCI or stenting. However, it did not improve the rates of angiographic restenosis, late reocclusion of the infarct related artery, or clinical outcomes at 6 months.  Whether earlier administration of platelet GP IIb/IIIa inhibition leads to improved blood flow in the infarct related artery at baseline is not known. 

   Recently, emphasis has been directed towards the problem of distal embolization during primary PCI.  Currently, several prospective randomized clinical trials are underway to determine whether thrombectomy and/or distal protection devices have a role in further optimizing the outcome of patients undergoing PCI for acute myocardial infarction.¨

References 

1.  Rogers WJ, Canto JG, Lambrew CT, Tiefenbrunn AJ, Kinkaid B, Shoultz DA, Frederick PD,     Every N. Temporal trends in the treatment of over 1.5 million patients with myocardial infarction     in the US from 1990 through 1999: the National Registry of Myocardial Infarction 1, 2 and 3. J     Am Coll Cardiol. 2000;36:2056-2063.

2. Indications for fibrinolytic therapy in suspected acute myocardial infarction: collaborative     overview of early mortality and major morbidity results from all randomised trials of more than     1000 patients. Fibrinolytic Therapy Trialists’ (FTT) Collaborative Group. Lancet.     1994;343:311-322.

3.  Eagle KA, Goodman SG, Avezum A, Budaj A, Sullivan CM, Lopez-Sendon J. Practice variation     and missed opportunities for reperfusion in ST-segment-elevation myocardial infarction: findings     from the Global Registry of Acute Coronary Events (GRACE). Lancet. 2002;359:373-377.

4. Anderson JL, Karagounis LA, Becker LC, Sorensen SG, Menlove RL. TIMI perfusion grade 3     but not grade 2 results in improved outcome after thrombolysis for myocardial infarction.     Ventriculographic, enzymatic, and electrocardiographic evidence from the TEAM-3 Study.     Circulation. 1993;87:1829-1839.

5. Gibson CM, Karha J, Murphy SA, James D, Morrow DA, Cannon CP, Giugliano RP, Antman     EM, Braunwald E. Early and long-term clinical outcomes associated with reinfarction following     fibrinolytic administration in the Thrombolysis in Myocardial Infarction trials. J Am Coll Cardiol.     2003;42:7-16.

6. Keeley EC, Boura JA, Grines CL. Primary angioplasty versus intravenous thrombolytic therapy     for acute myocardial infarction: a quantitative review of 23 randomised trials. Lancet.     2003;361:13-20.

7. Grines CL, Cox DA, Stone GW, Garcia E, Mattos LA, Giambartolomei A, Brodie BR, Madonna     O, Eijgelshoven M, Lansky AJ, O’Neill WW, Morice MC. Coronary angioplasty with or without     stent implantation for acute myocardial infarction. Stent Primary Angioplasty in Myocardial     Infarction Study Group. N Engl J Med. 1999;341:1949-1956.

8. Stone GW, Grines CL, Cox DA, Garcia E, Tcheng JE, Griffin JJ, Guagliumi G, Stuckey T,     Turco M, Carroll JD, Rutherford BD, Lansky AJ. Comparison of angioplasty with stenting, with     or without abciximab, in acute myocardial infarction. N Engl J Med. 2002;346:957-966.