Cardiac MRI in the prediction of outcomes in advanced cardiomyopathy

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Nearly 50% of patients with systolic heart failure suffer sudden cardiac death (SCD). In patients with ischaemic cardiomyopathy (ICM) and an LV ejection fraction (LVEF) of <30%, primary prevention ICD implantation reduced mortality at 20 months follow-up compared to medical therapy alone. Trials in NICM patients suggested similar findings but failed to reach statistical significance - statistical significance was only achieved when both ICM and NICM groups were combined. urrent clinically based guidelines focus on the importance of symptoms (NYHA Class) and LVEF in determining suitability for ICD implantation. Nonetheless, ICD implantation, despite its mortality benefit in selected patient populations, infers significant morbidity in terms or device related complications including tamponade, infections, inappropriate device therapy (which itself has been linked to increased mortality). Consequently, uptake of prophylactic ICD therapy in Australia has been variable with many major centres failing to comply with international guidelines. Hence, many authors have called for the urgent re-evaluation of current guidelines. Clearly there is a need for further risk stratification to assess the vulnerability of the heart failure population to sudden cardiac death, and other long term morbidities associated with the condition. Myocardial fibrosis is a fundamental event in the development of cardiac failure, and is a common feature in all patients with advanced cardiac failure regardless of the aetiology of cardiomyopathy. Myocardial fibrosis in animal models is associated with worsening ventricular systolic function, abnormal cardiac remodelling and may predispose to ventricular arrhythmia. Also, increasing myocardial fibrosis results in progressive deterioration of myocardial function, with more extensive myocardial fibrosis identified histologically in the hearts of patients with advanced heart failure. Cardiac fibrosis has been identified as a key component of remodelling associated particularly idiopathic cardiomyopathy and our group has demonstrated a clear association with arrhythmogenesis (including VT and VF) in patients with systolic heart failure. For example, recently, our group published compelling data supporting the role of contrast-enhanced cardiac magnetic resonance imaging (CMR) in identifying low risk patients who meet current criteria for ICD implantation yet are unlikely to benefit this intervention. We feel that the cardiac MRI evaluation, particularly its ability to detect both regional and diffuse fibrosis, may be a useful tool in predicting the outcomes of patients with heart failure. This trail seeks to establish a long term prospective data registry to evaluate predictive value of CMR in determining the long term outcome of patients with advanced cardiomyopathy.

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