Predischarge Risk Stratification

The use of noninvasive testing in the prethrombolytic era for risk stratification after AMI has been extensively reviewed (65-67). The predictive value of noninvasive testing for cardiac events is somewhat less in patients who received thrombolysis or direct coronary angioplasty; the patients tend to be younger, have better preserved left ventricular function, and have less extensive multivessel coronary disease (Fig. 5) (68). A substantial number of patients who undergo early coronary angiography have high-risk anatomy and are subsequently revascularized. This results in a relative low-risk patient population at the time of hospital discharge with a subsequent anticipated lower number of cardiac events to be investigated by noninvasive testing. The 1-yr mortality rates

80-d

80-d

Number of Diseased Vessel;!

Fig. 5. Comparison of angiographic findings in reperfusion trials with the pooled data from studies done in the prethrombolytic era. Reproduced with permission from ref. 68.

Number of Diseased Vessel;!

Fig. 5. Comparison of angiographic findings in reperfusion trials with the pooled data from studies done in the prethrombolytic era. Reproduced with permission from ref. 68.

in patients who survive to hospital discharge range from 2 to 3.3% in the TIMI II and the Should We Intervene Following Thrombolysis? (SWIFT) trials, respectively (69-71). Thus, according to Bayesian theory, noninvasive testing would need to be extremely precise to separate the 98 patients who survive from the 2 to 3 patients that will die in the year following AMI.

Acute coronary syndrome patients with an uncomplicated course that are ambulatory at the time of hospital discharge are generally lower risk individuals, since those with a complicated course have either died or received coronary revascularization procedures. Guidelines for the noninvasive evaluation of low risk patients at or around the time of hospital discharge were reviewed in the 1999 ACC/AHA Update of Acute Myocardial Infarct Guidelines. Three classes of recommendations for the noninvasive evaluation are published. Class I indications are conditions for which there is general evidence or general agreement that a given procedure or treatment is beneficial, useful, and effective. Class II indications are conditions for which there is conflicting evidence or divergent opinion about the usefulness/efficacy of a procedure or treatment. A class IIA guideline indicates the weight of evidence/opinion is in favor of usefulness/efficacy, whereas a class IIB indication is less well established by evidence/opinion. The class III indication are conditions for which there is evidence or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful. Table 1 illustrates the three different class indications for the use of noninvasive test procedures for lower risk postmyocardial infarct survivors.

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