Are Myocardial Infarctions Overdiagnosed?

Lilian White, MD
Posted on January 21, 2025

An estimated 805,000 people have a myocardial infarction (MI) every year. Approximately 25% of these are recurrent MIs, and 20% are not clinically recognized. Since the 1950s, the mortality rate of coronary artery disease has fallen by 70% because of the development of the echocardiography, advanced laboratory testing, and surgical and medical interventions, as well as preventive measures (eg, encouraging smoking cessation). The current age-adjusted mortality rate is 210 deaths per 100,000 people in the United States. In the office setting, there are an estimated 13 million visits annually for a primary diagnosis of coronary artery disease, history of MI, or ischemic heart disease.

Sensitive blood tests for MI were introduced in the late 1970s, leading to increasing numbers of MI diagnoses. The mortality risk associated with an MI did not change significantly, and the reduced case fatality rate declined. However, diagnosing more MIs has not necessarily improved health outcomes for patients. In fact, there is a potential downside to doing so: overdiagnosis. A Lown Right Care article published in the December 2024 issue of American Family Physician highlights key pathophysiologic and clinical considerations in the overdiagnosis of MI.

Type 1 MI is diagnosed when blood troponin levels are elevated in the setting of occlusion of myocardial blood vessels, causing cardiac injury. Type 2 MI occurs when blood troponin levels are elevated in the absence of myocardial blood vessel occlusion. Type 2 MIs have increased with the advent of troponin testing, leading to overdiagnosis and potential overtreatment without significant health benefits. A study over a period of 5 years found no mortality benefit for patients diagnosed with a type 2 MI. These patients also had an increased risk of undergoing invasive cardiac angiography in addition to costs, career ramifications, and depression, among other harms.

Troponin blood levels are nonspecific to type 1 MI and may be elevated in the setting of autoimmune disease, inflammatory disease, chronic renal disease, age older than 70 years, pulmonary embolism, infection, decreased oxygenation, insufficient blood flow to the heart, or significantly strenuous activities (eg, running a marathon). The positive predictive value of troponin testing for type 1 MI is only 11.8% in all-comers to the emergency department. This increases to nearly 60% in the United Kingdom but is only 16% in the United States when limited to physician selection of patients. This is likely due in part to the general trends of overtesting and medical litigation in the United States.

Underdiagnosis of MI, particularly in women, remains a concern; however, overdiagnosis is overall more common. The use of sex-specific thresholds for troponin testing may reduce underdiagnosis in women, but additional studies are needed to understand whether this improves outcomes in women with MI.

To reduce overdiagnosis, it is recommended to limit troponin testing to situations in which subjective symptoms or objective signs supportive of MI occur. Knowledge of causes of false positive troponin testing may also help reduce the overdiagnosis of type 2 MI. Additional information on the diagnosis of MI can be found in a Practice Guideline in American Family Physician.