Induced Myocardial Ischemia: a Serial Troponin T and Troponin I Measurements

Background Troponin are proteins found in the cardiomyocyte and are a cornerstone in the diagnoses of acute myocardial infarction. Troponin is released to the bloodstream as a result of an cardiomyocyte injury. Troponin is frequently assessed in hospital care for patients with chest pain and dyspnea.

Guidelines recommend troponin assessment at admission and repeated at 3 to 6 hours, depending on the assay. High-sensitivity assays measure concentrations that are ten-times lower than earlier generations of assays. However, the time from when troponin is elevated in the bloodstream after an ischemic injury, measured with high-sensitivity assays, are not fully known.

During an X-ray imaging of the heart's blood vessels (coronary angiogram) it is possible to do a short, controlled occlusion of coronary artery by inflating a small balloon in one of the coronary arteries. Numerous earlier studies in patients have used this method for induced occlusion of one coronary artery for 1 to 3 minutes. Only one of the studies measured troponin I.

The aim with this study is to quantify and compare the release of troponin T and troponin I in the early hours after a controlled induced ischemia.

Study Design This is a prospective, descriptive and experimental study. There will be included 40 patients, without acute ischemic cardiac disease. They will be randomized in 4 groups.

0: 10 patients - control group, no balloon occlusion

1. 10 patients - balloon occlusion for 30 seconds 2. 10 patients - balloon occlusion for 60 seconds 3. 10 patients - balloon occlusion for 90 seconds

Subsequently there will be assessed serial blood samples 0 - 3 hours: Every 15 minutes 3 - 6 hours: Every 30 minutes

Statistics This is a pilot study and it is estimated that ten patients are sufficient number of patients in each group to assess elevation of troponin after occlusion of coronary artery. The thesis is there is a dosage-response correlation between the length of balloon occlusion and the concentration of troponin in blood stream.