Non-contrast magnetic resonance imaging for guiding left ventricular lead position in cardiac resynchronization therapy.

Purpose: A left ventricular lead position concordant to viable myocardium at the site of latest mechanical activation is associated with a better response to cardiac resynchronization therapy (CRT). The present study aimed to guide left ventricular (LV) lead implantation into a vein over the area of latest mechanical activation with no transmural scar as determined by radial strain measured by non-contrast magnetic resonance imaging (MRI).

Methods: Patients admitted for CRT implantation underwent MRI on the day before pacemaker implantation. Time to peak radial strain in ventricular segments was measured to define the site of latest mechanical activation. Areas with peak radial strain less than 16.5% were defined as transmural scar. Venograms were visualized to define the optimal vein for LV lead positioning. Echocardiograms, 6-min hall walk test, and NYHA class were obtained at baseline and after 6 months of follow-up.

Results: Sixteen patients were included. In nine patients the lead was positioned at the primary target site, and in six patients a secondary was used owing to phrenic nerve stimulation (one patient), unstable lead position (two patients) and lack of suitable vein (three patients) at the primary target site. In three patients pre-implant MRI changed the implanters primary target vein.

Conclusion: Non-contrast MRI can be used to detect the site of latest mechanical activation by radial strain to guide LV lead positioning in candidates for CRT. Image guided LV lead implantation in CRT patients may in some patients change the primary target tributary of the coronary sinus.