RT Journal A1 Scirica BM, Morrow DA T1 POtassium levels after acute myocardial infarction—reply JF JAMA JO JAMA YR 2012 FD April 18 VO 307 IS 15 SP 1578 OP 1580 DO 10.1001/jama.2012.488 UL http://dx.doi.org/10.1001/jama.2012.488 AB In Reply: Dr Robey highlights the challenges of interpreting population-based research and the need to individualize the treatment of hypokalemia or hyperkalemia based on the patient's underlying pathophysiology. Current practice guidelines1 based on small, observational studies recommend maintenance of normal potassium levels, in particular among patients with significant ventricular ectopy. Despite a lack of compelling clinical data, many hospitals routinely implement automated algorithms for potassium supplementation that target potassium levels above 3.5 or 4.0 mEq/L in a broad range of hospitalized patients, including those presenting with AMI. Thus, the widespread assumption that routine potassium repletion is medically necessary persists, and achieving these targets requires significant resources. The report by Goyal et al2 is one of the largest studies to evaluate the relationship between potassium level and outcomes in AMI. Despite the inherent limitations of any observational, population-based study, the findings from Goyal et al are a substantial step forward from the previous small reports and should remind clinicians of the value of reevaluating habitual clinical practices based on sparse data.