Cardiac imaging in the SCA survivor aims to (i) assess cardiac morphology and function, (ii) characterize the cardiomyopathy, and (iii) stratify risk of adverse clinical outcomes and guide therapeutic interventions. This process often requires different imaging modalities. Echocardiography and cardiac MRI represent the dominant imaging modalities in clinical practice.
Echocardiography in the presence of good acoustic windows is a reliable imaging modality for the assessment of cardiac size/function and valvular abnormalities, but may be inadequate for the phenotypic characterization of the cardiomyopathy. In contrast to echocardiography, cardiac MRI has unrestricted range of tomographic planes and high spatial resolution, allowing excellent delineation of endocardial and epicardial borders and more reproducible data. As a result, cardiac MRI is now considered the ‘gold standard’ for the assessment of cardiac anatomy, chamber volumes and ventricular function. Angiography by cardiac MRI can also be used to assess coronary artery anomalies.
Cardiac MRI can identify and quantify myocardial scar/fibrosis by using specific inversion recovery gradient echo sequences at least 10 min after the intravenous injection of gadolinium-chelated contrast agents (late gadolinium enhancement). The pattern/distribution of late gadolinium enhancement can distinguish ischemic (typically sub-endocardial or transmural) from non-ischemic cardiomyopathy (mid-myocardial or epicardial). In addition, T2- -weighted imaging, which highlights unbound water in the myocardium, can identify areas of edema associated with inflammation (such as myocarditis and sarcoidosis) or acute ischemia. Myocardial fibrosis detected by late gadolinium enhancement on cardiac MRI is associated with increased frequency of ventricular arrhythmias in patients with idiopathic dilated cardiomyopathy and hypertrophic cardiomyopathy.
T1-weighted images (with and without fat suppression) on cardiac MRI have been used to identify areas of fatty infiltration in the right ventricular wall, but this parameter has poor sensitivity and specificity for the diagnosis of ARVC. In contrast, global or regional right ventricular wall motion abnormalities are specific (in experienced hands) and recognized as a criterion for the diagnosis of ARVC.