Cardiac magnetic resonance imaging for the diagnosis of patients presenting with chest pain, raised troponin, and unobstructed coronary arteries

Myocardial Infarction With Non-obstructive Coronary Arteries - Diagnosis and Management

MI with non-obstructive coronary arteries (MINOCA) is an enigma that is being increasingly recognised with the frequent use of angiography following acute MI. To diagnose this condition, it is important to determine the multiple potential underlying mechanisms that may be responsible, many of which require different treatments. This review evaluates the contemporary diagnosis and management of MINOCA.

Usefulness of the troponin-ejection fraction product to differentiate stress cardiomyopathy from ST-segment elevation myocardial infarction

The presentation of stress cardiomyopathy (SC) with nonobstructive coronary artery disease mimics that of ST-segment elevation myocardial infarction (STEMI) due to coronary occlusion. No single parameter has been successful in differentiating the 2 entities. We thus sought to develop a noninvasive clinical tool to discriminate between these 2 conditions. We retrospectively reviewed 59 consecutive cases of SC at our institution from July 2005 through June 2011 and compared those with 60 consecutives cases of angiographically confirmed STEMI treated with primary percutaneous coronary intervention in the same period. All patients underwent acute echocardiography, and the peak troponin I level was determined. The troponin-ejection fraction product (TEFP) was derived by multiplying the peak troponin I level and the echocardiographically derived left ventricular ejection fraction. Comparing the SC and STEMI groups, the mean left ventricular ejection fraction at the time of presentation was 30 ± 9% versus 44 ± 11%, respectively (p <0.001), and the peak troponin I was 7.6 ± 18 versus 102.2 ± 110.3 ng/dl, respectively (p <0.001). The mean TEFP was thus 182 ± 380 and 4,088 ± 4,244 for the SC and STEMI groups, respectively (p <0.001). Receiver operating characteristic curve analysis showed that a TEFP value ≥250 had a sensitivity of 95%, a specificity of 87%, a negative predictive value of 94%, a positive predictive value of 88%, and an overall accuracy of 91% to differentiate a true STEMI from SC (C-statistic 0.91 ± 0.02, p <0.001). In conclusion, for patients not undergoing emergent angiography, the TEFP may be used with high accuracy to differentiate SC with nonobstructive coronary artery disease from true STEMI due to coronary occlusion.

Chest pain with elevated troponin assay in adolescents

OBJECTIVE

We sought to describe the evaluation, treatment, and follow-up of adolescents who presented to a single institution with chest pain and an elevated troponin I value in the absence of typical symptoms of pericarditis or myocarditis. Materials and methods We performed a retrospective review of patients in the age group of 10-18 years of age with no history of significant heart disease admitted to our institution from 2000 to 2010 after presenting with chest pain and an elevated troponin I value.

RESULTS

A total of 16 patients were identified with a median age of 16.5 years (range 11.2-17.8 years). Of these 13 (81%) were male and 10 (63%) showed evidence of localised ST elevations on electrocardiogram. The median peak troponin I level was 17.8 nanograms per millilitre (range 0.89-227, normal less than 0.4). There were eight patients (50%) with a diagnosis of coronary vasospasm, three patients (20%) with atypical myopericarditis, one patient with coronary anomaly, one patient with hypercoagulable disorder, and one patient with prolonged supraventricular tachycardia. In two patients, no definitive diagnosis was made. There was one patient who needed catheter-based intervention, which involved stenting of a coronary artery after a procedure-related complication.

CONCLUSIONS

In our cohort of adolescents without history of significant cardiac disease, chest pain and elevated troponin I levels were attributed to a variety of causes. Although coronary vasospasm and atypical myopericarditis were seen most commonly, coronary anomaly was identified in one case. Magnetic resonance imaging proved a useful diagnostic tool to assess coronary artery anatomy and myocardial changes suggestive of myocarditis. On the basis of these results and a review of the literature, a general evaluation algorithm is presented.

Myocardial infarction with normal coronary arteries is common and associated with normal findings on cardiovascular magnetic resonance imaging: results from the Stockholm Myocardial Infarction with Normal Coronaries study

OBJECTIVES

Myocardial infarction with angiographically normal coronary arteries (MINCA) is an important subtype of myocardial infarction; however, the prevalence, underlying pathophysiology, prognosis and optimal management of this condition are still largely unknown. Cardiovascular magnetic resonance (CMR) imaging has the potential to clarify the underlying pathology in patients with MINCA. The objective of this study was to investigate the diagnostic value of CMR imaging in this group of patients.

DESIGN

The prospective, multicentre, observational Stockholm Myocardial Infarction with Normal Coronaries (SMINC) study.

SETTING

Coronary care units in the Stockholm metropolitan area.

SUBJECTS

Patients between 35 and 70 years of age with MINCA were consecutively included in the screening phase of the SMINC study. All patients had a typical clinical presentation, fulfilling the universal definition of myocardial infarction and had normal coronary angiography finding. Patients with known structural or coronary heart disease or other known causes of elevated troponin levels were excluded.

RESULTS

In total, 176 patients with MINCA were screened from 2007 to 2011. Of these, 152 underwent CMR imaging. The investigation was performed a median of 12 (interquartile range 6-28) days after hospital admission; 67% of the findings were normal, whereas 19% of patients had signs of myocardial necrosis and 7% had signs of myocarditis. The remaining patients (7%) had either unrecognized hypertrophic cardiomyopathy or could not be classified.

CONCLUSION

In this consecutive series of patients with MINCA, CMR imaging may help to differentiate between those with myocarditis, myocardial necrosis and normal myocardium. The incidence of MINCA was higher than previously reported. After excluding cases of myocarditis, MINCA consists of a large group of patients with normal CMR imaging results and a smaller group with myocardial necrosis. The aetiologies of these different imaging findings need to be explored.

Diagnostic and prognostic value of cardiovascular magnetic resonance in non-ischaemic cardiomyopathies

Cardiovascular Magnetic Resonance (CMR) is recognised as a valuable clinical tool which in a single scan setting can assess ventricular volumes and function, myocardial fibrosis, iron loading, flow quantification, tissue characterisation and myocardial perfusion imaging. The advent of CMR using extrinsic and intrinsic contrast-enhanced protocols for tissue characterisation have dramatically changed the non-invasive work-up of patients with suspected or known cardiomyopathy. Although the technique initially focused on the in vivo identification of myocardial necrosis through the late gadolinium enhancement (LGE) technique, recent work highlighted the ability of CMR to provide more detailed in vivo tissue characterisation to help establish a differential diagnosis of the underlying aetiology, to exclude an ischaemic substrate and to provide important prognostic markers. The potential application of CMR in the clinical approach of a patient with suspected non-ischaemic cardiomyopathy is discussed in this review.