The results of a new MRI multicenter study led by Innsbruck cardiologist Sebastian Reinstadler give reason to revise a previously valid guideline for heart attack prognosis. According to the study, the bleeding into the heart muscle (IMH) visible on MRI and not microvascular occlusions (MVO) as previously used should be used as markers for risk calculation and for the development of future therapies after an ST-elevation myocardial infarction (STEMI)*. The specialist journal Journal of the American College of Cardiology reports.
Cardiac magnetic resonance imaging has proven to be the gold standard for assessing the function and tissue damage of the heart muscle after a heart attack. Especially after STEMI, which affects around 40 percent of heart attack patients, the assessment of the individual prognosis using MRI is crucial.
“After the successful reopening of the blocked coronary artery, we see so-called microvascular occlusions in the MRI in around 50 percent of STEMI patients. These are untreatable, but were previously considered a marker for a poor prognosis. Therefore, previous studies aimed to find new targets for the treatment of MVO,” explains study leader Sebastian Reinstadler from the University Clinic for Internal Medicine III, Cardiology and Angiology (Director: Axel Bauer), where around 1,000 heart attack patients are treated acutely each year.
With IMH (intramyocardial hemorrhage), a pattern of damage that is found in about half of patients with MVO and indicates extensive inflammation with iron deposits in the heart muscle, the researchers have now succeeded in identifying a new independent prognosis marker. The renowned journal Journal of the American College of Cardiology reports.
This result is particularly relevant not only for optimizing risk assessment, but also for developing new therapeutic strategies that target microvascular damage. “The question now is whether specific therapeutic strategies after a heart attack (STEMI) improve the outcome of patients with IMH. This hypothesis is now the subject of further studies,” emphasizes Reinstadler.
In order to examine the prognostic relevance of various patterns of damage to the heart muscle that can be visualized using MRI, data from a total of 1,109 STEMI patients – the largest STEMI population ever included in a clinical study – from four heart centers (Innsbruck, Lübeck, Leipzig and Glasgow) were prospectively analyzed. The cohort was divided into three groups: patients without microvascular tissue damage (neither MVO nor IMH), patients with microvascular vascular occlusions but without bleeding into the heart muscle (MVO+/IMH) and patients with bleeding into the heart muscle (IMH+). “We found that in the group of patients with bleeding into the heart muscle, an adverse cardiac event occurred more frequently after an average of twelve months than in the other two subgroups,” confirms lead author Ivan Lechner. Patients with microvascular occlusions and without intramyocardial hemorrhage, however, had a similar prognosis to patients without any microvascular damage.
“It is assumed that in the remodeling process after a heart attack, blood vessels break open, allowing red blood cells to enter the infarcted tissue, where they are taken up by macrophages, large immune cells, and deposit iron there. This could drive inflammatory processes that promote a poor prognosis,” explains Ivan Lechner. These molecular principles and the question of whether the size of the infarct is decisive for the extent of the IMH require further clarification.
Even if intramyocardial hemorrhage cannot currently be prevented, clinical research into new therapeutic approaches for IMH should be a priority. In the meantime, affected patients should be closely monitored. The independent prognostic significance of IMH in assessing the risk after STEMI will in any case be included in a revised consensus paper on risk stratification after a heart attack, the study authors are certain.
*) The ST segment is a curve section of the electrocardiogram, the changes of which have a high diagnostic value with regard to the blood flow to the heart muscle, especially after a heart attack.
About the people:
Sebastian Reinstadler studied medicine at the universities of Innsbruck and Padua. His passion for cardiology led to a specialization in the field of interventional cardiology. Since 2019 he has been working as a senior physician and since 2023 as 2nd Deputy Director at the University Clinic for Internal Medicine III (Cardiology and Angiology). In addition to clinical care and teaching, he is dedicated to research in the areas of cardiovascular imaging, myocardial infarction and atrial fibrillation.
Ivan Lechner is training to be a cardiologist at the Medical University of Innsbruck. In his doctoral thesis, he examined the significance of tissue damage at the microvascular level after an acute heart attack. In addition to his scientific work, he is a nucleus member of the “Cardiologists of Tomorrow” of the Austrian Society of Cardiology and an “Embassador” for cardiac magnetic resonance imaging of the European Association for Cardiac Imaging (EACVI).
About the research work:
Clinical Outcomes Associated With Various Microvascular Injury Patterns Identified by Cardiac MRI After STEMI. https://www.jacc.org/doi/10.1016/j.jacc.2024.03.408
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