Cardiac Biomarkers for the Quantification of Myocardial Damage After Cardiac Surgery

The aim of the study is to clarify whether the perioperative release of the cardiac biomarkers troponin I, troponin T and CK-MB consistently correlate with visualizable myocardial damage, and to what extent these biomarkers are comparable by means of their kinetics and dynamics.

Due to the uncertainty regarding the validity of cardiac biomarkers in the diagnosis of myocardial infarction, the answer to these questions could have a considerable influence on internationally valid guidelines and definitions. International studies, especially in the field of coronary surgery and coronary artery disease treatment refer to these definitions, in particular, the adequate treatment of affected patients is directly dependent on them.

In the course of a myocardial infarction, the death of cardiomyocytes leads to the release of specific cardiac biomarkers (CK-MB, troponin I and T). Since there is a general risk of perioperative infarction in cardiac surgery, the standard monitoring includes appropriate diagnostics. These are based on clinical symptoms, ECG, imaging (echocardiography or coronary angiography) and, in particular, the elevation of these cardiac biomarkers. Recently, the latter have been regularly moved into the foreground as the sole indicators of perioperative myocardial infarction, and first definitions allow the diagnosis solely based on troponin or CK-MB elevation.

However, biomarker elevations may not be accompanied by an image-morphologically detectable perfusion defect (myocardial infarction). Such phenomena have been described outside of cardiac surgery, for example, in marathon runners4, but also due to comorbidities such as renal insufficiency or neurological diseases. Even in patients undergoing cardiac surgery without coronary artery disease (e.g., isolated valve surgery), biomarker elevations up to the infarct-defining range are regularly observed. Whether in the latter case the perioperative routinely observed troponin or CK-MB elevation are indeed related to surgery-induced chronic perfusion disturbance has not yet been investigated.

To date, there is no study that quantitatively correlates purely perioperatively induced ischemic damage with the release of cardiac biomarkers. In addition, the three most commonly used biomarkers for perioperative infarct diagnosis differ considerably in their temporal release and release dynamics. Moreover, a direct comparison of all three parameters has never been performed so far.

Therefore, the aim of this study is to quantify and compare the release of troponin T, I and CK/CK-MB in the postoperative course in patients without relevant coronary artery disease undergoing elective isolated heart valve surgery. These findings will subsequently be correlated with classical diagnostics (clinic, ECG, echocardiography) and image morphological quantification of perioperatively induced myocardial damage by magnetic resonance imaging (LGE-cMRI).

Eligibility Criteria:
Inclusion Criteria:

* Indication for isolated aortic or mitral valve surgery
* Written informed consent
* Age ≥ 18 years

Exclusion Criteria:

* Presence of coronary artery disease (excluded within the last 6 months)
* Allergy to gadolinium
* Cochlear implant
* Deep brain stimulation
* Individual factors excluding the performance of an MRI (e.g. claustrophobia of the patient)
* Significantly reduced renal function (GFR \< 30ml/min)
* Perioperative complications that may lead to myocardial damage (discontinuation of the study for the patient and exclusion from the analysis after primary study inclusion)
* Need for extension of surgery (additional procedures on other heart valves, aorta, myocardium, or similar; exclusion after primary study inclusion possible)
* Pregnancy or lactation