Cardiac Magnetic Resonance Imaging Strategy for the Management of Patients With Acute Chest Pain and Detectable to Elevated Troponin

In the evaluation of patients with possible acute coronary syndrome, serum troponin measurement is a critical determinant of myocardial necrosis. The recent implementation of high-sensitivity troponin assays allows detection of lower levels of serum troponin than possible with less sensitive predecessors. As a result, 30% more patients are diagnosed with myocardial injury but the optimal management of these patients is unclear. Guidelines from the American Heart Association and American College of Cardiology recommend an invasive management strategy (Class 1a) but acknowledge that data supporting an invasive strategy were based on less sensitive troponin assays than those available today. Clinical trials of an invasive strategy in patients with detectable to minimally elevated troponin values demonstrate conflicting results. Observational data suggest aggressive medical therapy rather than increased use of revascularization drives improved outcomes in these patients. Meanwhile, these patients with minimally elevated serum troponin values have experienced a near doubling in the rate of invasive angiography. In short, it is uncertain whether patients with detectable to minimally elevated troponin results benefit from current invasive-based care strategies. As an alternative, cardiac magnetic resonance (CMR) imaging is highly accurate for detecting significant coronary disease and the need for coronary revascularization.

Objectives: The broad, long-term objective is to improve outcomes by optimizing healthcare delivery processes for patients with detectable to elevated serum troponin. To achieve this goal, we propose a clinical trial (n=312) involving emergency department patients with intermediate to high-risk chest pain and detectable to minimally elevated serum troponin within 6 hours of evaluation.

Methods: Participants will be randomized to one of two care strategies: a) invasive-based guideline-adherent strategy, or b) CMR-guided. Outcomes will be assessed over an average of 2.3 years. The specific aims of this proposal are 1) Test whether a CMR-guided strategy (versus invasive-based guideline-adherent strategy) reduces the composite of death, nonfatal myocardial infarction, and cardiac-related hospital readmission over the study duration, and 2) Test whether a CMR-guided strategy (versus invasive-based guideline-adherent strategy) reduces invasive angiography, coronary revascularization, recurrent cardiac testing, and cardiac-related emergency department visits.

Inclusion criteria

• Age greater than or equal to 21 years of age at the time of enrollment
• Symptoms consistent with acute coronary syndrome
• At least 1 troponin > lower limit of detection and ≤1.0 ng/ml within 6 hours of the initial evaluation

Exclusion criteria

• Any troponin >1.0 ng/ml at the time of consent
• New ST-segment elevation (≥ 1 mV) or depression (≥ 2 mV)
• Hemodynamic instability (symptomatic systolic BP <90 mmHg, dysrhythmia)
• Ongoing, unrelieved symptoms thought to represent cardiac ischemia and requiring immediate cardiac catheterization
• Known severe multi-vessel CAD previously determined to be not amendable to mechanical intervention
• Coronary revascularization in the past 6 months
• Contra-indications to magnetic resonance imaging Examples: Unable to lie flat, pacemaker, defibrillator, cerebral aneurysm clips, metallic ocular foreign body, implanted devices, severe claustrophobia, pregnancy
• Life expectancy less than 12 months
• Increased risk for nephrogenic systemic fibrosis i. Creatinine clearance < 30 ml/min at the time of enrollment ii. clinical concern for acute kidney injury and/or acute renal failure* iii. Hepato-renal syndrome or chronic liver disease with a creatinine clearance of <60 ml/min at the time of enrollment iv. History of liver, heart, or kidney transplant

• This may be manifested by a recent or concurrent rise in serum creatinine, or a reduction in baseline creatinine clearance.