The recent clinical guidelines on myocardial infarction risk stratification [1] are meant to represent evidence-based medicine, but they seem to recommend discharge on day 4 or 5 in patients with an uncomplicated course who have only had an electrocardiographic stress test. The data provided to support early discharge include PAMI-2 (Primary Angioplasty in Myocardial Infarction-2) participants, who had already been identified as low risk by their coronary anatomy from emergent cardiac catheterization [2]; a small trial of patients treated with lytic therapy who had negative results on stress thallium tests [3]; and several statistical analyses attempting to identify low-risk patients without actual trials of early discharge. The small trial [3] randomly assigned 80 patients with uncomplicated infarctions and negative results on exercise thallium tests to early (day 3) or conventional (day 7 to 10) discharge. The authors of this study state that "Before this strategy can be widely recommended, however, its safety must be confirmed in larger prospective clinical trials" [3].

Additional evidence used to obviate the need for imaging methods in predischarge testing is summarized in Table 3 of the guideline [1]. Exercise thallium testing has an average negative predictive value for cardiac death or myocardial infarction of 0.96; exercise electrocardiography has an average negative predictive value of 0.90. Thus, 10 of 100 patients with a negative result on exercise electrocardiography will have cardiac death or myocardial infarction compared with only 4 of 100 patients with a negative result on exercise thallium testing. I would guess that at least 6 of 100 patients with negative results on echocardiographic stress tests would find this information clinically relevant.