Clinical guidelines and standardized order sets are as integral to the practice of medicine in the digital age as the stethoscope and the chest x-ray. Rigorously developed guidelines and order sets aim to bring the most current, evidence-based medicine to the bedside and decrease unwanted variability in health care delivery. The JAMA Performance Improvement article in this issue of JAMA by Gupta and colleagues, however, illustrates the potential risks inherent in the incorporation of these tools into practice.1 In this case, a 58-year-old man with acute ST-segment elevation myocardial infarction (STEMI) was successfully treated with percutaneous coronary intervention (PCI) involving the right coronary artery but had bradycardia and complete heart block following the procedure. The patient was admitted to the coronary care unit, and the admitting physician placed orders via the electronic medical record using the “STEMI admission order set.” Within an hour of admission, the patient received medications, including atorvastatin and carvedilol, based on the order set. Over the next few hours, he developed dyspnea, bradycardia, and hypotension. This case demonstrates how a flawed guideline, incorporated into an inadequately updated order set, can undermine a physician’s intention and lead to patient harm.