New methods in diagnostic and therapy
New applications of cardiovascular magnetic resonance to guide cardiac resynchronization therapy

Introduction

Cardiac resynchronization therapy (CRT) is a treatment of proven efficacy in patients with heart failure, impaired left ventricular ejection fraction and wide QRS complex. It has been demonstrated that CRT has a good effect on left ventricular remodelling, and improves outcome and quality of life. However, in 1/3 of patients this therapy brings no expected benefit. There are many variables that may influence the response to resynchronization described in the literature. Among others, the presence of mechanical dyssynchrony of the left ventricle and the amount of myocardial fibrosis assessed with cardiovascular magnetic resonance (CMR) have been mentioned [1]. The assessment of left ventricular contraction dyssynchrony in CMR is based on post-processing multi-stage data, which makes this method difficult to use in clinical practice. In contrast, evaluation of delayed enhancement (DE), which corresponds with myocardial fibrosis, is a relatively simple and well-documented technique. The CMR study with fibrosis imaging guides the procedure of left ventricular lead placement to avoid the scar. Furthermore, the assessment of the scar enables one to evaluate the amount of viable left ventricular myocardium ready to undertake synchronised contractile activity after CRT implantation. Along with the dynamic development of magnetic resonance imaging technique and better understanding of its clinical usefulness, new applications of CMR in patients referred for CRT have been reported. Apart from previously mentioned methods of dyssynchrony and delayed enhancement assessment, the growing role of evaluation of right ventricular function and scar homogeneity has been shown.

Assessment of right ventricle

The interest of scientists in multi-centre randomized clinical trials on patients with CRT has been mainly focused on the assessment of left ventricular systolic function prior to device implantation and the evaluation of left ventricular remodelling as a result of the therapy. Therefore the guidelines of the European Society of Cardiology, which are based on the data from clinical trials, contain only the criterion of left ventricular ejection fraction. Whereas right ventricular dysfunction and its impact on the response to CRT are not fully documented.

The presence of systolic dysfunction of the right ventricle is a strong and independent predictor of death in patients with chronic heart failure [2, 3]. The results of studies...


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