Myocardial infarction (MI) is the irreversible death, known as necrosis, of heart muscle due to prolonged restriction of blood flow and oxygen. A diagnosis of MI is made by obtaining a history of the presenting illness, a physical examination with electrocardiogram (EKG) findings and a blood test for cardiac enzymes. Once a diagnosis is made, the treatment of choice is primary angioplasty whereby the artery obstruction is treated with percutaneous coronary intervention (PCI) to allow reperfusion of the infarcted tissue.
According to the American Heart Association, there are approximately 920,000 new and recurrent heart attacks per year in the United States and about 34 percent of those individuals will die within a year. Myocardial infarction may lead to impairment of heart function and to increased predisposition to arrhythmias and congestive heart failure with the concomitant costs of care including but not limited to defibrillator (ICD) and pacemaker insertions as well as repeated hospitalizations.
Infarct Expansion and Myocardial Reperfusion Injury
Considerable attention has been directed to achieving timely reperfusion of occluded coronary arteries to interrupt the infarction expansion with the hope that the resultant limitation of infarct size will improve ventricular function and therefore subject survival. In 2004, the American College of Cardiology and the American Heart Association published extensive guidelines regarding treatment of subjects with suspected STEMI. They recommended that for subjects with ST elevation on a 12-lead ECG and with symptoms of STEMI, reperfusion therapy should be initiated as soon as possible but optimally percutaneous coronary intervention (PCI) should be initiated with 90 minutes of hospital arrival (door to balloon time).
While early PCI is intended to salvage as much myocardium as possible and to prevent further complications, reperfusion of cardiac tissue which has been subjected to prolonged ischemia results in a phenomenon known as myocardial reperfusion injury. The etiology of reperfusion injury is multifactoral but may be responsible for up to 50% of the final infarct size. Since reperfusion injury may contribute significantly to the final size of a myocardial infarct, strategies to reduce the extent of reperfusion injury are clinically important. Multiple animal models have demonstrated that left ventricular unloading decreases myocardial infarct size presumably by preventing reperfusion injury.
The TRIS Trial
The TandemHeart to Reduce Infarct Size (TRIS) Trial will evaluate the effectiveness of ventricular unloading on the reduction of infarct size for patients who have suffered a severe heart attack. Patients enrolled in the TRIS Trial will be randomized to receive either conventional therapy or a TandemHeart device to unload the left ventricle along with percutaneous coronary intervention (PCI). The primary efficacy endpoint of the study is improvement in myocardial salvage index (MSI). Additionally, the economic impact of TandemHeart therapy will be studied through secondary endpoints including long term mortality and the rates of repeat hospitalization and implantable cardioverter-defibrillator (ICD) usage. A reduction in these rates could decrease the total cost of treatment for this patient population.
The TRIS Trial is expected to begin enrollment in early 2013 and will include up to 20 hospitals, with leadership from Principle Investigators Biswajit Kar, M.D., Chief of the Center for Advanced Heart Failure at Memorial Hermann Heart and Vascular Institute in Houston, Texas, and David Holmes, M.D., Professor of Medicine at the Mayo Clinic College of Medicine in Rochester, Minnesota, and Immediate Past President of the American College of Cardiology (ACC).
If you would like to request more information regarding the TRIS Trial, or would like to be considered as a participating hospital site, please contact us here.
 Krumholz HM, et al. ACC/AHA Task Force on Performance Measures for ST-elevation and non-ST-elevation myocardial infarction. Circulation. 2008 Dec 9; 118(24):2596-648.
 Wright RS et al. ACC/AHA focused update on the guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction. J Am Coll Cardiol. 2011; 57(19)1920-1959.
 Park JL, Lucchesi BR. Mechanisms of myocardial reperfusion injury. Ann Thorac Surg. 1999 Nov; 68(5):1905-12.
 Yellon DM, Hausenloy DJ. Myocardial reperfusion injury. N Engl J Med. 2007 Sep 13; 357(11):1121-35.
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