Emergency percutaneous coronary intervention (PCI) for the care of patients with ST-elevation myocardial infarction (STEMI).Minerva Cardioangiol. 2007 Oct; 55(5):593-623.MC
There is general consensus that emergency percutaneous coronary intervention (PCI) is the preferred treatment for patients with ST-elevation myocardial infarction (STEMI), so long as it can be delivered in a timely fashion, by an experienced' operator and cardiac catheterization laboratory (CCL) team. STEMI is both a functional and structural issue. Although it has been recognized since the work of pioneering cardiologists and surgeons in Spokane, Washington, that approximately 88% of patients presenting within 6 hours of onset of STEMI have an occluded coronary artery, it is the pathophysiology of myocardial necrosis, and the varied consequences of necrosis that characterize STEMI. Accordingly, experience' of both primary operator and cardiac catheterization laboratory (CCL) crew, in performing an emergency PCI for STEMI, are as much a function of experience with the treatment of complex MI patients, as experience with coronary intervention. Rapidly achieving normal coronary artery flow, at both the macro and micro vascular levels, is the recognized key to aborting the otherwise progressive wavefront' of myocardial necrosis. The time urgency of decisions (Time is muscle') make emergency PCI for patients with on-going necrosis, more like emergency room (ER) care, than like most in-hospital or outpatient care. In general, most patients with acute coronary syndromes (ACS) are currently thought to have plaque rupture and/or erosion with subsequent thrombosis and embolization. Consequences of thrombo-embolism, such as slow flow' or no-reflow' are in addition to, the structural (anatomic) considerations of PCI in stable patients (such as ostial location; bifurcation involvement; heavy calcification; tortuosity of lesion or access to it; length of disease; caliber of infarct-artery; etc.). Good quality studies have provided strong support for the specific added value of glycoprotein IIb/IIIa inhibitors (especially abciximab), dual antiplatelet therapy (the addition of the thienopyridine, clopidogrel, to aspirin use), and bare-metal stents (BMS), for a broad range of STEMI patients. The added value of drug-eluting stents (DES) to bare-metal stents (BMS), primarily in terms of reducing restenosis and repeat revascularization, is supported by several randomized trials, and a number of registries, despite its being off-label' from a regulatory standpoint. The recognition of late stent thrombosis (LST) has raised additional issues, in choosing between these two options for specific STEMI patients. The added value of a number of other mechanical approaches to coronary thrombus, such as thrombus removal devices, and/or distal protection, are more controversial, and perhaps, patient specific. Whether intravascular ultrasound guidance (IVUS) for stent use should be used for the majority, or even a specific minority, of STEMI patients, is also controversial; late-stent thrombosis provides a counter-point. The advantages of developing a network approach to STEMI care, so as to optimize the number of patients receiving timely reperfusion, have been demonstrated in Prague, Denmark, and Minneapolis, among many places. The benefits of both bivalirudin (anti-thrombin drug with efficacy against clot-bound thrombin, which does not appear to stimulate platelets) and abciximab (glycoprotein IIb/IIIa inhibitor which is antibody to platelet receptors), as PCI adjuncts generally, and for STEMI patients, in particular, are supported by multiple trials. The specific choice of administering the bolus dose of either, or both, drugs via intra-coronary (IC) injection follows the precedents' of IC thrombolytics, and IC small-vessel vasodilators for no-reflow', but it has not been tested by prospective, randomized trials. Although rapid reperfusion is the first objective, one cannot ignore the other components of the oxygen delivery chain, and the importance of each of these components to on-going delivery of oxygen to all vital organs. A balance must be struck between doing those control' things which serve to stabilize other vital components of the oxygen-delivery chain, without digressing too long from the job of re-establishing brisk coronary flow. The clinical and angiographic heterogeneity of STEMI patients and the array of available therapeutic approaches make it impossible to obtain specific randomized trial direction for many of the clinical decisions in an individual emergency PCI for STEMI. There are a range of reasonable/ appropriate therapeutic choices for a given emergent PCI performed by multiple experienced and competent operators. The treatment of STEMI, and high-risk non-STEMI, patients, by means of emergent PCI, is among the most challenging and rewarding arenas in contemporary medicine.