"Why Does It Hurt When They Say My Blood Vessels Are Fine?" A New Way to Detect Heart Risks [Health Check]

[Financial News] Coronary microvascular dysfunction was identified in approximately one out of every three patients who underwent coronary angiography for suspected ischemic heart disease. Their risk of cardiovascular events was found to be nearly twice that of patients with normal microvascular function.
Coronary microvascular dysfunction (CMD) is a condition in which the small blood vessels that supply blood to the heart muscle fail to function properly and cannot deliver sufficient blood flow. It can cause myocardial ischemia and chest pain even when there is no significant narrowing in the major coronary arteries.
Microvascular dysfunction has traditionally been assessed using measures such as coronary flow reserve (CFR) and the index of microvascular resistance (IMR). Recently, however, microvascular resistance reserve (MRR) has drawn attention as a new indicator because it evaluates the function of the microvasculature itself after accounting for the effects of the epicardial coronary arteries. MRR indicates how much the coronary microvasculature can reduce vascular resistance when increased blood flow is needed; a lower value indicates impaired microvascular function.
Because of these characteristics, MRR has been proposed as a potential complement to existing indicators. However, clinical evidence of its usefulness in actual patients has remained limited.
A research team led by Joo Myung Lee of the Department of Cardiology at Samsung Medical Center, along with Hong Young-jun, Lee Seung-heon, and Joon Ho Ahn of Chonnam National University Hospital, evaluated the prevalence and prognostic impact of coronary microvascular dysfunction using MRR. The multicenter study was published in the latest issue of the European Heart Journal (EHJ), a leading cardiology journal published by the European Society of Cardiology, which has an impact factor of 45.3.
The study analyzed 1,003 patients who underwent coronary angiography with physiological assessment for suspected ischemic heart disease. They were enrolled in the Multicenter FLOW-CMD Registry, a multicenter study involving seven medical institutions in South Korea between April 2022 and November 2024. The study was led by Joo Myung Lee of Samsung Medical Center.
The researchers defined microvascular dysfunction as an MRR of 2.5 or lower and classified the patients accordingly. Microvascular dysfunction was identified in 334 of the 1,003 patients, or 33.3%.
During a median follow-up period of 1.9 years, patients with microvascular dysfunction had a 1.94-fold higher risk of major cardiovascular events than those without the condition. Major cardiovascular events were assessed using a composite measure of all-cause death, myocardial infarction, target-vessel revascularization, and hospitalization for heart failure. The estimated two-year incidence of major cardiovascular events was also significantly higher in the microvascular dysfunction group, at 18.2%, compared with 8.6% in the normal group.
These findings suggest that MRR may not only assess impaired coronary microvascular function but also help identify patients at high risk of future cardiovascular disease.
Lee Seung-heon said, "This study suggests that microvascular dysfunction, which has traditionally been assessed by considering several indicators together, may be evaluated more simply using a single measure called microvascular resistance reserve." He added, "The significance of this study lies in confirming that the new assessment indicator is also associated with patients’ actual prognosis."
Joo Myung Lee, the study’s principal investigator, said, "Coronary microvascular dysfunction is difficult to detect through coronary angiography alone, so even when patients report chest pain, it can sometimes be difficult to identify the exact cause." He added, "We hope this study will help establish a new standard for more precisely diagnosing microvascular dysfunction and assessing patients’ risk."
The study was selected for the Late-Breaking Clinical Trial session at ESC Congress 2026, held in Munich. Joo Myung Lee presented the findings in person on the 28th, local time.


[email protected] Medical Specialist Jung Myung-jin Reporter