The investigators wish to examine whether a novel 'nanoparticle' of iron oxide, administered intravenously allows an area of heart muscle damage after heart attack to be visualised using a magnetic resonance scanner.

Using ferumoxtran (Feraheme) as a USPIO contrast agent for magnetic resonance imaging at 3 Tesla, we aim to conduct the first clinical study to examine the utility of this novel contrast agent to image myocardial inflammation after myocardial infarction.

We will test the following hypotheses in patients who have suffered recent acute myocardial infarction.

1. Intravenous injection of ferumoxytol accumulates at the site of myocardial infarction and this can be visualised by magnetic resonance imaging.
2. The spatial extent of the MRI signal change evoked by ferumoxytol in the myocardium is proportional to the volume of infarcted myocardium (as assessed by a gadolinium late-enhancement study).
3. Myocardial MRI signal change evoked by ferumoxytol is positively correlated with blood markers of systemic inflammation.

Inclusion Criteria:

• Presentation with myocardial infarction (either 'ST-elevation' myocardial infarction or 'non-ST-elevation' myocardial infarction
• Troponin I ≥ 10 IU/mL at 12 hours after the onset of chest pain
• Age 18 - 80 years inclusive

Exclusion Criteria:

• Known critical (≥95%) left main stem coronary artery disease
• Continued symptoms of angina at rest or minimal exertion
• Atrial fibrillation
• Symptomatic heart failure; Killip Class ≥2.
• Hepatic failure (Childs-Pugh grade B or C) or renal failure (estimated glomerular filtration rate <25 mL/min)
• Contraindication to magnetic resonance imaging
• Past history of systemic iron overload/haemochromatosis
• Patients with known allergy to dextran- or iron-containing compounds