1. -159º ±180º -90º 0º 90º Pt 1 Lateral position Cardiology Vectorcardiography Madelon van den Heuvel BSc, Marcel van ’t Veer MSc, PhD, Berry van Gelder PhD, Frank Bracke, MD, PhD. Catharina Hospital Eindhoven, April 2012 Vectorcardiographic changes in the heart axis during left ventricular pacing Introduction Cardiac resynchronisation therapy (CRT) can optimize the contraction of the heart by left ventricular stimulation in selected patients with heart failure. One third of the patients do not experience clinical benefit, which might be due to suboptimal position of the left ventricular (LV) lead. The purpose of this study was to examine whether the heart axis obtained from a vectorcardiogram (VCG) can be helpful in localising the left ventricular stimulation site by determining the mutual position of the stimulation electrodes of a LV-lead. The ultimate goal is to define the optimal left ventricular stimulation site through VCG. Methods The Frank VCG was calculated from a standard 12-lead employing the Kors method. This method was applied in 13 CRT patients with a standard dual unipolar or quadripolar LV-lead implanted in a coronary sinus tributary and unipolar stimulation of each electrode. The heart axis during stimulation was calculated from the projection of the maximum vector in the frontal, transversal and sagittal plane. A heart axis more to the left was suggested to be related to an electrode position more to the right, a septal heart axis to a more lateral position and a cranial heart axis to a more caudal position. The calculated position of the electrodes was compared with the position on chest X-ray in two directions. Results In 90 out of 93 two-dimensional VCGs the mutual position of the LV electrodes was correctly described compared to the X-ray: a more left oriented heart axis correlated with a position of the LV electrode to the right in the frontal plane; a more septal heart axis correlated with a lateral position in the transversal plane (see figure 1); a more cranial orientated heart axis correlated with a caudal position in the sagittal plane (see figure 2). Conclusion The VCG calculated using the Kors method is an adequate tool to determine the mutual position of the LV electrodes and might be useful to make an accurate determination of the lead position. These findings appear to make further analysis of the VCG worthwhile for clinical implementation as a non-invasive technique to determine the (optimal) LV-pacing site for CRT in order to minimize the group of non-responders. Figure 2B. The VCG of a patient during distal stimulation showing a more posterior heart axis than during proximal stimulation, suggesting a more caudal position 1.Department of Cardiology, Catharina Hospital 2.Maastricht Universitycontact details: madelon.vd.heuvel@catharinaziekenhuis.nl Figure 2A. The VCG of a patient during proximal stimulation showing a posterior heart axis. Figure 2C. The X-ray confirms a more caudal position of the distal electrode compared to the proximal electrode -157º 0º ±180º 90º -90º -142º -90º 0º 90º ±180º LAO Y X Distal Pt 2 LAO Pt 1 Lateral position -159º ±180º 90º Figure 1. The VCGs in the transversal plane (figure 1A and 1C) suggest a more lateral LV lead position of patient 1 according the heart axis (-159º vs. -39º). This is confirmed by the X-ray (figure 1B) showing a more lateral position of the LV lead compared to patient 2 (figure 1D) showing a posterior position. A C AA Pt 1 Lateral position Pt 1 LAO B Dista l C Pt 2 LAO C Distal Pt 2 Posterior position -90º ±180º 90º 0º -39º Pt 2 LAO D Distal 90º 0º 90º -39º 0º 90º -90º -39º 0º 90º ±180º -90º -39º 0º 90º -90º -39º 0º 90º -90º -39º 0º 90º C ±180º -90º -39º 0º 90º -157º 0º ±180º 90º -90º 0º -90º 90º 0º -90º ±180º 90º 0º -90º -159º ±180º 90º 0º -90º -159º ±180º 90º 0º -90º -159º ±180º 90º 0º -90º -159º ±180º 90º 0º -90º -159º ±180º 90º 0º -90º A