Características de mezclado y aplicaciones

A. General Principles

As discussed in Section III, coronary angiography is useful for defining the coronary artery anatomy in patients with UA/NSTEMI and for identifying subsets of high-risk patients who may benefit from early revascularization. Coronary revascularization (PCI or CABG) is carried out to improve prognosis, relieve symptoms, prevent ischemic complications, and improve functional capacity. The deci- sion to proceed from diagnostic angiography to revascular- ization is influenced not only by the coronary anatomy but also by a number of additional factors, including anticipated life expectancy, ventricular function, comorbidity, func- tional capacity, severity of symptoms, and quantity of viable myocardium at risk. These are all important variables that must be considered before revascularization is recom- mended. For example, patients with distal obstructive cor- onary lesions or those who have large quantities of irrevers- ibly damaged myocardium are unlikely to benefit from revascularization, particularly if they can be stabilized with medical therapy. Patients with high-risk coronary anatomy are likely to benefit from revascularization in terms of both symptom improvement and long-term survival (Fig. 12). The indications for coronary revascularization in patients with UA/NSTEMI are similar to those for patients with chronic stable angina and are presented in greater detail in the ACC/AHA/ACP-ASIM Guidelines for the Manage- ment of Patients With Chronic Stable Angina (26), as well as in the ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery (274).

Plaque rupture with subsequent platelet aggregation and thrombus formation is most often the underlying patho- physiological cause of UA (1,18). The management of many patients with UA/NSTEMI often involves revascularization of the underlying CAD with either PCI or CABG. Selec- tion of the appropriate revascularization strategy often depends on clinical factors, operator experience, and extent of the underlying CAD. Many patients with UA/NSTEMI have coronary disease that is amenable to either form of therapy. However, some patients have high-risk features, such as reduced LV function, that places them in a group of patients who experience improved long-term survival rates with CABG. In other patients, adequate revascularization with PCI may not be optimal or even possible, and CABG may be the better revascularization choice.

Findings in large registries of patients with CAD suggest that the mode of clinical presentation should have little bearing on the subsequent revascularization strategy. In a series of 9,263 patients with CAD, an admission diagnosis of UA (vs. chronic stable angina) had no influence on 5-year

survival rates after CABG, PTCA, or medical treatment (288). An initial diagnosis of UA also did not influence survival 3 years after either CABG or PTCA in 59,576 patients treated in the state of New York (289). Moreover, long-term survival rates after CABG are similar for UA patients who present with rest angina, increasing angina, new-onset angina, or post-MI angina (290). These obser- vations suggest that published data that compare definitive treatments for patients who initially present with multiple clinical manifestations of CAD can be used to guide management decisions for patients who present with UA/ NSTEMI. Consequently, the indications for coronary re- vascularization in patients with UA/NSTEMI are, in gen- eral, similar to those for patients with stable angina. The principal difference is that the impetus for some form of revascularization is stronger in patients with UA/NSTEMI by the very nature of the presenting symptoms (290).

Recommendations for Revascularization With PCI and CABG in Patients With UA/NSTEMI (see Table 20) Class I

1. CABG for patients with significant left main CAD. (Level of Evidence: A)

2. CABG for patients with 3-vessel disease; the sur- vival benefit is greater in patients with abnormal LV

function (EF<0.50).(Level of Evidence: A)

3. CABG for patients with 2-vessel disease with sig- nificant proximal left anterior descending CAD and

either abnormal LV function (EF<0.50) or demon-

strable ischemia on noninvasive testing. (Level of

Evidence: A)

4. PCI or CABG for patients with 1- or 2-vessel CAD without significant proximal left anterior descend- ing CAD but with a large area of viable myocar- Figure 12. Revascularization strategy in UA/NSTEMI. *There is conflicting information about these patients. Most consider CABG to be preferable to PCI.

dium and high-risk criteria on noninvasive testing. (Level of Evidence: B)

5. PCI for patients with multivessel coronary disease with suitable coronary anatomy, with normal LV

function and without diabetes.(Level of Evidence: A)

6. Intravenous platelet GP IIb/IIIa inhibitor in UA/

NSTEMI patients undergoing PCI.(Level of Evi-

dence: A) Class IIa

1. Repeat CABG for patients with multiple saphe- nous vein graft (SVG) stenoses, especially when there is significant stenosis of a graft that supplies

the LAD.(Level of Evidence: C)

2. PCI for focal SVG lesions or multiple stenoses in

poor candidates for reoperative surgery. (Level of

Evidence: C)

3. PCI or CABG for patients with 1- or 2-vessel CAD without significant proximal left anterior descend- ing CAD but with a moderate area of viable myo-

cardium and ischemia on noninvasive testing.(Lev-

el of Evidence: B)

4. PCI or CABG for patients with 1-vessel disease with significant proximal left anterior descending CAD.(Level of Evidence: B)

5. CABG with the internal mammary artery for pa- tients with multivessel disease and treated diabetes

mellitus.(Level of Evidence: B)

Class IIb

1. PCI for patients with 2- or 3-vessel disease with significant proximal left anterior descending CAD, with treated diabetes or abnormal LV function, and with anatomy suitable for catheter-based therapy. (Level of Evidence: B)

Class III

1. PCI or CABG for patients with 1- or 2-vessel CAD without significant proximal left anterior descend-

ing CAD or with mild symptoms or symptoms that are unlikely due to myocardial ischemia or who have not received an adequate trial of medical therapy and who have no demonstrable ischemia on

noninvasive testing.(Level of Evidence: C)

2. PCI or CABG for patients with insignificant cor-

onary stenosis (<50% diameter). (Level of Evi-

dence: C)

3. PCI in patients with significant left main coronary

artery disease who are candidates for CABG.(Level

of Evidence: B)