The “rule-in” process for acute chest pain generates an estimated $600 million per year in unnecessary in-patient expenses.
When a patient presents to the emergency room with acute chest pain, their acute coronary syndrome may include many different entities: ST-elevation myocardial infarction (MI), non-ST-elevation MI, and unstable angina. Accurate diagnosis can most often lead to fast, often life-saving appropriate treatment.
Unfortunately, recent estimates indicate that nearly 2% of patients with acute MI are inappropriately discharged from the emergency room (ER). These discharged patients have had MIs which are missed even though they have undergone proper testing.
In patients whose MI is missed, the mortality rate is around 16%. Therefore, the current diagnostic strategies imaging acute chest pain have their shortcomings which need to be addressed as a matter of urgency.
A prospective study of 161 consecutive patients who presented to the ER with >30 minutes of chest pain compatible with myocardial ischemia, and an ECG not diagnostic of acute MI, was conducted in order to determine whether cardiac MRI could accurately identify patients with acute coronary syndrome.
MRI was performed at rest within 12 hours of presentation, and included perfusion, assessment of left ventricular function, and gadolinium-enhanced MI detection. All patients were followed up at 6 to 8 weeks to ensure that no acute coronary syndrome was missed.
From the study results, resting cardiac MRI does appear suitable for the triage of patients with acute chest pain in the ER. Performed promptly in order to evaluate acute chest pain, MRI accurately detected a high fraction of patients with acute coronary syndrome, including those with enzyme-negative unstable angina.
One important limitation to note is that with cardiac MRI, there is the inability to differentiate acute versus chronic MI. Both have similar delayed enhancement characteristics, and cannot be differentiated.
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