According to a team of experts from the Massachusetts General Hospital (MGH) Heart Center, levels of a biomarker used in the diagnosis of heart attacks seem to have been roughly elevated in patients who have undergone coronary-artery bypass grafting (CABG). In addition, when the levels of the biomarker namely cardiac troponin T (cTnT) were distinctly elevated, they appeared to be strongly prognostic.
The measurement of cTnT could possibly assist in determining patient prognosis. However, present consensus recommendations regarding the use of cTnT in order to diagnose post-CABG heart attack or myocardial infarction may perhaps be reconsidered reveal experts.
“Although postoperative concentrations of cTnT were powerfully predictive of the risk of complications and death after CABG, we found the currently recommended cut-points for diagnosing myocardial infarction are far too low. But use of cTnT to predict overall postoperative risk does look very promising,†says senior author of the study, James Januzzi, MD, director of the MGH Cardiac Intensive Care Unit.
Patients recovering from bypass surgery appear to be at risk for a number of postoperative complications including heart attack. During bypass surgery, blood supply to the heart muscle is believed to be rerouted around one or more blocked coronary arteries. Contemporary standards for the diagnosis of post-operative myocardial infarction are noted to include consideration of symptoms such as chest pain, electrocardiogram changes and the results of biomarker tests.
Clinicians seem to greatly rely on biomarkers like cTnT in order to diagnose post-CABG heart attacks, since patients recuperating from cardiac surgery appear to certainly suffer from chest pain. Also, the results of postoperative electrocardiograms are believed to be often indistinct.
Previous studies of the prognostic role of cTnT in cardiac surgery patients have found that severe elevations of the enzyme seem to strongly predict the risk of complications and death in the year following surgery. However, that study examined a combination of post-cardiac-surgery patients. Also it failed to consider diagnostic guidelines outlined in a 2007 consensus statement from four organizations, including the American Heart Association and the American College of Cardiology.
The present study was noted to have been designed in order to particularly evaluate the usefulness of cTnT in the diagnosis of post-CABG heart attack and to examine factors associated with postoperative cTnT elevation. Also, how well cTnT levels appear to predict postoperative complications in general seems to have been observed for the study.
For the purpose of the study, experts measured cTnT levels of nearly 850 CABG patients immediately after their procedures and approximately 6, 8, 18 and 24 hours later. These levels were then believed to have been analyzed based on several factors related to the patients’ original illness, surgery, and short-and long-term results.
The findings of the study revealed that cTnT levels seemed to have been elevated in nearly all post-CABG patients, although only about 2 percent actually met postoperative myocardial infarction criteria. Apparently, factors predicting cTnT elevation included the complexity of the early coronary artery blockages, the number of grafts which were placed and the patients’ immediate postoperative condition.
Januzzi, an associate professor of Medicine at Harvard Medical School, further stated that, “These findings imply that the diagnosis of regional post-CABG myocardial infarction should continue to be based largely on clinical judgment and angiographic demonstration of postoperative closure of a bypass graft, which is fortunately a rare situation.â€
“On the other hand, excessive diffuse myocardial injury – as reflected by significant cTnT elevation – may be more common than suspected; and cTnT does an excellent job of identifying those patients destined for complication in the postoperative period. This makes a strong case that troponin testing should be incorporated into overall post-CABG risk assessment, independent of its use for MI diagnosis,†elucidates Januzzi.
Though the near-universality of cTnT elevation appears to have made it a less useful indicator of heart attack, cTnT levels are suppsoedly 10 times higher in contrast to the present consensus guidelines which powerfully and independently predict the risk of death and other postoperative complications. This may perhaps have added to the predictive power of risk-scoring models such as that developed by the Society for Thoracic Surgery.
The findings of the study will be published in the journal Circulation.
