In case of a heart attack, every minute counts, and is often a matter of life and death. However, a reliable diagnosis is not always easy based only on the symptoms. Sometimes, the ECG, i.e. the measurement of the cardiac current curve, is not informative enough to clearly determine or rule out a heart attack. This is because a certain section of the ECG curve, the so-called ST segment, is not always elevated. In the case of such a non-ST elevation infarct, the diagnosis “heart attack” can only be made if special laboratory values are positive in the blood test.
In this examination, the biomarkers Troponin I and T primarily indicate whether it is an ST elevation infarct or non-ST elevation infarct. Troponin is a protein complex that is present exclusively in the heart muscle and only enters the bloodstream when the muscle cells are damaged. The result of the test usually takes about 60 minutes and is repeated 6-9 and 12-24 hours after the first test respectively if it is not conclusive enough. An eternity in an acute infarct.
An international research team led by the University Heart and Vascular Centre of the University Hospital Hamburg-Eppendorf (UKE) has now developed a risk calculator for patients suspected of having a heart attack. With its help, a faster and more reliable diagnosis will be possible. With the so-called “Compass MI“, a new risk calculator that is also available online, cardiologists will be able to assess more quickly and reliably whether a heart attack has actually occurred.
Reliable diagnosis within one hour
The scientists explain that the diagnostic aid is based on modern tests that can also detect very low concentrations of troponin. “With the help of the troponin values measured and the exact time between the measurements, and by taking into account the type of blood test used, it is now possible to calculate the probability of the patient having an acute heart attack. This is a novelty,” explains Dr. Johannes Neumann, Department of General and Interventional Cardiology at the University Cardiovascular Center.
The decisive factor for the diagnosis is not, as before, a fixed threshold value for the troponin concentration in the blood, but the increase in the troponin values during the measurement period. “We have broken the concept for the diagnosis of an acute heart attack that was written down in the medical guidelines,” said Prof. Dr. Stefan Blankenberg, Medical Director of the University Heart and Vascular Centre. In other words, even if the ECG does not show any clear signs of a heart attack, doctors can still reach a reliable diagnosis within about an hour and initiate the necessary therapeutic measures. Due to unreliable results, doctors had to wait up to twelve hours to definitely diagnose or rule out a heart in the past.
Worldwide study with 22,000 patients
The new findings are the result of a data analysis of more than 22,000 patients from 13 countries worldwide. Therefore, during the first examination, doctors immediately measured the concentration of troponin I or troponin T in the blood of all patients who came to an emergency room with suspicion of a heart attack. Further examinations using highly sensitive blood tests followed up to three and a half hours later. “We developed the algorithm here in Hamburg. We harmonized the worldwide data and then used it as a common data set for analysis,” explains Dr. Neumann, one of the two main authors of the study.
The analysis also revealed that only 15 percent of the patients actually had a heart attack. “Low initial concentrations of troponin and a small increase in concentration were associated with a low probability of a heart attack,” the researchers write. In addition, these patients had a low risk of further cardiovascular complications in the next 30 days. “With an initial troponin I concentration of less than 6 nanograms per litre (<6 ng/L) and only a small increase (<4 ng/L) within 45 to 120 minutes, more than half of all patients (57%) belonged to this low-risk group.”
According to the scientists, the study provided them with valuable data for creating the algorithm. In a second step, they were able to develop a risk calculator that will help doctors diagnose a heart attack and decide on further therapeutic measures in the future.
The results of the study were published in the New England Journal of Medicine.
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