[Magnetic resonance imaging early after acute myocardial infarction. A visual analysis of myocardial perfusion based on a 17 segment model]

The value of cardiac magnetic resonance in patients with acute coronary syndrome and normal coronary arteries

INTRODUCTION AND OBJECTIVES

A number of different conditions can present with symptoms similar to acute coronary syndrome (ACS): chest pain, electrocardiographic changes and elevated levels of markers of myocardial damage. Even after coronary angiography has been performed, differential diagnosis can be challenging. The aim of this study was to evaluate the usefulness of cardiac magnetic resonance (CMR) for diagnosing conditions that present like ACS but in which the coronary arteries are normal.

METHODS

The study involved 80 patients with suspected ACS and normal coronary arteries. Their mean age was 48+/-15 years and their mean troponin-T (TnT) level was 1.8+/-0.9 ng/ml. A CMR study, which involved T2-weighted imaging to detect edema and delayed contrast-enhancement (DCE) imaging 10 minutes after gadolinium administration, was performed.

RESULTS

In 51 patients (63%), the final diagnosis was acute myocarditis. In all these cases, DCE was observed in subepicardial and middle segments of the myocardium. The final diagnosis was acute myocardial infarction in 12 patients (15%), all of whom exhibited subendocardial or transmural DCE. In the 9 (11%) who exhibited abnormal contractility on baseline echocardiography with subsequent normalization, CMR did not show DCE, a finding that is characteristic of Takotsubo cardiomyopathy. In addition, 4 patients had a final diagnosis of pericarditis, while no diagnosis could be established in another 4.

CONCLUSIONS

The clinical presentation of acute myocarditis and Takotsubo syndrome can be similar to that of ACS. The presence and distribution of DCE on CMR are of great help in establishing a diagnosis.

Late enhancement using multidetector row computer tomography: A feasibility study with low dose 80kV protocol

AIMS

Detecting stenoses of coronary arteries with multidetector row computer tomography (MDCT) is a well feasible non-invasive method. However, there is still the problem of deciding whether a stenosis is hemodynamically relevant or not. Objective of the present study was to validate the feasibility of a low dose protocol for MDCT using 80 kV for detecting late enhancement.

METHODS AND RESULTS

Using a Alderson-Rando Phantom evaluation of the effective dose of this LE protocol was performed. Ten patients (six male, four female, mean age 61) with known coronary artery disease and scheduled for a conventional coronary angiogram in our facility were subsequently recruited. All patients underwent CT-angiography (CTA) 1 day prior to magnetic resonance imaging. Five minutes after the application of 100ml contrast agent for the CTA scan, a low dose late enhancement scan (80 kV, 400 mA s maximum, ECG pulsed scan, 64 mm x 0.6mm collimation, 0.33 s tube rotation) was performed. Phantom dose measurements showed an effective dose for this protocol of 1.19 mSv (male) and 1.61 mSv (female). Fifty-six percent (5/9) of the patients showed a late enhancement on the MRI scan. Three transmural late enhancements and all four negative findings were correctly identified by CT. This represents a sensitivity of 78% (3/5), specificity of 100% (3/3), NPV of 100% (4/4) and a PPV of 97%.

CONCLUSION

We were able to show that the low dose protocol is feasible and, furthermore, preliminary results look promising.

[Contribution of cardiac MRI in the etiologic diagnosis of chest pain syndrome with a normal angiographic aspect of the coronary arteries]

The etiologic diagnosis of chest pain with elevation of specific cardiac enzymes, repolarization abnormalities and a normal angiographic aspect of the coronary arteries is difficult. In this situation, the role of cardiac MRI is growing, frequently allowing to precise the etiology of the chest pain. We present a literature review concerning the semiology of the cardiac MRI in the three main involved etiologies: myocarditis, takotsubo syndrome, and myocardial ischemia with a normal angiographic aspect of the coronary arteries.