Late enhancement
Late gadolinium enhancement is a technique used in cardiac magnetic resonance imaging for cardiac tissue characterization, in particular, the assessment of regional scar formation and myocardial fibrosis .
Terminology
Late gadolinium enhancement is also known under the terms ‘late enhancement’ or ‘delayed enhancement’.
Radiographic features
MRI
Late gadolinium enhancement is based on the shortening of T1 and different regional distribution patterns of gadolinium-based contrast agents within the extracellular space of the myocardium. It also depends on varying uptake and washout patterns within the normal myocardium and those different disease processes. This is depicted by applying an inversion pulse in order to null the inherent signal of the myocardium after a certain amount of time .
Acquisition
Image acquisition for late gadolinium enhancement is usually conducted with an inversion recovery prepared T1 gradient echo and either manually adapted inversion time or as PSIR sequence with a phase-sensitive inversion-recovery based reconstruction algorithm .
Typically late gadolinium enhancement is measured around 10-20 min after administration of a gadolinium-based contrast agent.
Interpretation
Late gadolinium enhancement is a result of regional differences in myocardial extracellular volume and different uptake and washout patterns within the extracellular space and is seen in myocardial injury e.g. myocyte necrosis, myocardial edema, myocardial scar tissue and focal areas of fibrosis, and can be related to different cardiac diseases in regard to its distribution and other tissue properties and clinical parameters .
Clinical applications
It is applied in the various clinical scenarios and can help to detect and characterize various myocardial diseases :
- myocardial infarction
- detection and quantification of regional myocardial fibrosis and myocardial scar tissue
- LGE is considered a surrogate for infarct size
- detection of microvascular obstruction (MVO)
- strong predictor of outcome (superior to ventricular volumes and function)
- myocarditis
- patchy mid myocardial and/or focal subepicardial enhancement as an expression of potentially irreversible injury (myocyte necrosis, fibrosis, edema)
- can represent one of two main criteria in the diagnosis of acute myocarditis
- cardiac sarcoidosis
- patchy mid myocardial and/or focal subepicardial enhancement as an expression of potentially irreversible injury
- linked to cardiac arrhythmia even with preserved left ventricular function
- cardiac amyloidosis
- subendocardial enhancement in a non-coronary distribution and poor contrast difference between blood and myocardium due to abnormal blood-pool/tissue gadolinium kinetics
- dilated cardiomyopathy
- detection of intramyocardial midwall fibrosis
- predictor of ventricular arrhythmia and sudden cardiac death (SCD)
- hypertrophic cardiomyopathy
- patchy/streaky intramyocardial patterns at the right ventricular insertion sites within the hypertrophied myocardium suggest fibrosis
- prognostic value with increased risk of sudden cardiac death (SCD)
- Anderson-Fabry disease
- characteristic midwall or subepicardial enhancement in the basal inferolateral wall
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