Efficacy Evaluation of Observation Unit Cardiac Magnetic Resonance Imaging (MRI) in Patients With Intermediate Risk Acute Chest Pain

Despite spending $12 billion annually on the emergency evaluation of chest pain in the US, only 15% of admitted patients have a cardiac cause of their presenting symptoms. Observation units (OU) improve resource utilization, are endorsed by the ACC/AHA guidelines, but have seen limited implementation in non-low risk chest pain patients due to limitations of traditional cardiac testing. Cardiac magnetic resonance imaging (CMR) is sensitive and specific for ischemia, can simultaneously assess cardiac function and myocardial perfusion, and could revolutionize the diagnostic process for intermediate risk patients with chest pain. The superior accuracy of CMR could decrease testing resulting from false positive results. The high sensitivity for ongoing ischemia could allow imaging in parallel with cardiac markers.

Research hypotheses:

OU-CMR will have superior therapeutic efficacy to OU-conventional testing.

An OU-CMR strategy will have higher diagnostic thinking efficacy than OU-conventional testing.

Methods summary:

To address the question of feasibility of a CMR approach to managing patients at intermediate risk for ACS, we propose a randomized clinical trial of 120 patients at intermediate risk of ACS that present to the ED of Wake Forest University Baptist Medical Center (WFUBMC) for evaluation of chest pain. All patients will receive care in an OU, and will be randomized to CMR, or conventional testing. CMR participants will undergo cardiac markers and CMR testing; conventional testing participants will undergo serial cardiac markers followed by conventional cardiac testing. ACS (infarction, death, coronary revascularization, unstable angina) will be assessed by evaluation of hospital course and phone follow-up at 30 days. Cost of hospital care will be compared among groups.

Inclusion criteria

• Age greater than or equal to 18 years
• Chest discomfort or other symptoms consistent with possible ACS
• TIMI risk score ≥ 1 or physician impression* of intermediate or high likelihood symptoms represent ACS
• Patient requires an inpatient or observation unit evaluation for their chest pain
• The treating physician feels the patient could be discharged home if cardiac disease was excluded
• ED attending feels patient is safe for observation unit care**

Exclusion criteria

• Initial troponin I > 1.0 ng/ml
• New ST-segment elevation (≥1mV) or depression (≥2 mV)
• Contra-indications to MRI (listed below)
• Unable to lie flat
• Hypotension (systolic < 90 mm Hg)
• Renal insufficiency (estimated GFR < 45 cc/min) or end stage renal disease
• Life expectancy less than 3 months
• Patient refusal of medical record review and follow-up at 30 days
• Pregnancy
• Liver, heart, or kidney transplant
• Chronic liver disease
• Unable to speak English or Spanish
• The ED attending feels that cardiac catheterization is indicated
• The ED care provider intends to order a CT coronary angiogram

(*)Physicians are encouraged to use the 2007 ACC/AHA guidelines for the management of patients with NSTE ACS as a framework for this assessment.(1)

(**)These patients should generally not be considered for observation unit care: PCI / CAGB in past 6 months, multiple stents, multiple prior MIs

Contraindications to MRI: (Pacemaker, defibrillator, cerebral aneurysm clips, metallic ocular foreign body, implanted devices, claustrophobia)