Why Heart Attacks are Missed in the Emergency Department
Published on March 16, 2026
Contact Terrell CV DownloadThe Starting Point: What the Data Actually Tells Us
When litigation attorneys examine a case involving a missed acute myocardial infarction, they often begin with a question that seems straightforward: how could a physician miss a heart attack? The natural assumption is that the answer involves either negligence or knowledge gaps. The clinical reality, however, is considerably more complex.
Understanding that complexity requires stepping back from the specific case to examine why missed MI diagnoses occur at such a high rate across American Emergency Departments. Research consistently places this rate at approximately one-third of acute MI cases being initially missed.
This statistic deserves careful interpretation. A missed MI diagnosis means a patient with acute infarction was evaluated in an Emergency Department, did not receive admission or appropriate observation, and left the department without a diagnosis of MI.
The infarction was subsequently identified later, sometimes hours or days afterward, when the patient returned to the hospital after deterioration or when a subsequent evaluation revealed the prior MI. These are not cases where the diagnosis was technically correct but merely delayed.
These are cases where the diagnostic process failed to identify an active, serious condition that warranted immediate intervention.
The prevalence of this phenomenon is not limited to poorly resourced or unusually incompetent institutions. It occurs in academic medical centers with cardiology services on site. It occurs in hospitals with modern laboratory capabilities and experienced emergency physicians.
The consistency of this finding across different settings and different time periods suggests that the explanation involves something more systemic than individual provider error.
The Distinction Between Knowledge and Performance
A critical distinction exists between knowing something and doing it consistently under pressure. An emergency physician can possess comprehensive knowledge of MI presentations, understand troponin kinetics, and be able to explain ECG interpretation, yet still miss an acute MI in a specific patient encounter.
This is not because the knowledge was absent but because the conditions under which that knowledge is applied create pressures that interfere with consistent performance.
The Emergency Department operates under a unique set of constraints that distinguish it from other medical settings. Decisions must be made rapidly with incomplete information. Patient flow pressures create time-based incentives that pull toward disposition decisions.
The environment is cognitively demanding, with simultaneous competing tasks and frequent interruptions. Patients arrive with undifferentiated complaints that could represent dozens of different conditions. Against this backdrop, the human mind employs cognitive shortcuts, called heuristics, that generally work well but sometimes fail spectacularly.
Consider a practical example. An experienced emergency physician has seen hundreds of patients with chest pain. Most of those patients did not have MI. The physician’s brain has developed pattern recognition that efficiently categorizes incoming patients into high-risk and low-risk groups based on initial presentation. This pattern recognition is valuable. It allows rapid mental triage that generally works. But pattern recognition can also fail. When a patient presents with features that fit the pattern for a low-risk diagnosis (for instance, pleuritic chest pain in a young woman with a history of anxiety), the mind experiences a sense of closure. The pattern feels complete and correct. The diagnostic search stops. Yet this specific combination of features does not exclude MI.
Atypical Presentations: Why the Template Fails
The fundamental challenge in emergency MI diagnosis stems from the reality that acute MI presentations exist on a spectrum far broader than the textbook description most physicians learned in training. Medical students learn about the “classic” MI: a middle-aged or older patient with substernal chest pressure radiating to the arm, associated with sweating. This presentation does occur, and when it does, it is usually recognized appropriately.
The problem emerges with the presentations that deviate from this template. Chest pain in acute MI may be completely absent. It may be present but so fleeting that the patient cannot reliably describe its timing or character. The pain may be described as sharp or stabbing rather than pressure-like. It may be pleuritic, worsening with respiration. It may be localized to the epigastrium and feel indistinguishable from indigestion. It may be located in the back, the neck, or the jaw with little or no chest involvement.
Beyond the location and character of pain, the primary complaint itself may not be chest-related at all. Dyspnea, or shortness of breath without chest discomfort, represents a particularly important atypical presentation. In elderly patients especially, dyspnea may be the dominant or even sole presenting symptom of acute MI. Yet the mental template most physicians carry for MI includes dyspnea as an associated symptom, not as the primary complaint. When dyspnea is the primary reason for the ED visit, the diagnostic consideration for MI must be actively engaged rather than automatically triggered.
Patient Populations and Hidden Risk
The gap between textbook presentations and real-world presentations is not distributed evenly across the population. Certain groups present with atypical features more frequently, and simultaneously, certain groups receive less aggressive diagnostic evaluation when they do present. This divergence creates a particular vulnerability.
Women younger than 55 years with possible cardiac ischemia tend to present with features that deviate from the classic male presentation. Research examining this population finds both that atypical features are genuinely more common and that these patients are less likely to be admitted for observation and testing compared to older men with similar presentations. The mechanism of this disparity likely involves a combination of factors: atypical features that lower clinical suspicion, cognitive biases about which patients “should” have MI, and time pressures that influence disposition differently for different patient groups.
Diabetic patients represent another population at particular risk. Diabetic neuropathy can blunt pain perception, resulting in “silent” or minimally symptomatic MIs. Yet when a diabetic patient presents with any constellation of symptoms that could represent ischemia (chest discomfort, dyspnea, nausea, malaise), the diagnostic bar should not be raised simply because pain is absent. The absence of typical pain in a diabetic should lower the threshold for testing, not raise it.
Elderly patients with dyspnea-predominant presentations constitute a third vulnerable group. The assumption that dyspnea must represent pulmonary disease or deconditioning, without active consideration of cardiac causes, represents a systematic source of missed diagnosis in this population.
The Architecture of Misdiagnosis
Understanding why one-third of acute MIs are missed requires recognizing that the explanation is not uniform across all cases. Some misses result from failure to order appropriate testing. Others result from ordering tests but misinterpreting results. Some involve failure to recognize the limitations of negative test results. Others involve anchoring bias, which means locking onto an alternative diagnosis and ceasing to consider other possibilities.
What ties these mechanisms together is that they are not primarily problems of knowledge. An emergency physician can know that troponin takes time to rise, yet still discharge a patient based on a single normal troponin drawn within two hours of symptom onset. A physician can understand that elderly patients present with atypical symptoms, yet still lower the diagnostic consideration for an elderly patient presenting with dyspnea without chest pain.
The misses occur at the intersection of knowledge and performance, where the pressures and structure of the emergency environment interact with how human cognition actually functions under those conditions. Recognizing this distinction helps understand why these cases occur and what factors influenced diagnostic decision-making in any specific situation.
Terrell Swanson is an emergency medicine expert witness who can testify in court for cases requiring objective medical analysis of causation.
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