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.