Imaging in cardiac resynchronization therapy: what does the clinician need?

In the guidelines, criteria to select patients for cardiac resynchronization therapy (CRT) are based only on the QRS duration on surface electrocardiogram (ECG) as a marker of cardiac dyssynchrony. From a theoretical point, imaging techniques would be useful to improve patient's selection with an analysis of the atrio-ventricular, interventricular and intraventricular dyssynchrony. Imaging techniques may also identify physiopathological issues such as the presence of scar, right ventricular dysfunction, or severe pulmonary hypertension. New echocardiographic techniques appear promising, but the role of echocardiography in the identification of mechanical dyssynchrony remains to be clearly defined in prospective multicentre trials. The positioning of left ventricular lead could be optimized using different imaging techniques to assess the site of latest activation and the coronary sinus anatomy. Finally, imaging techniques may have an important role to optimize the programming of the device, especially the different cardiac timings. In the present article, we focused on echocardiography, multislices-computed tomography, and magnetic resonance imaging being discussed elsewhere.