Comparison of non-invasive mapping with 12-lead ECG for the identification of left ventricular lateral wall activation

Abstract Background R-wave peak time (RWPT) is a measurement from the onset of the QRS complex to the apex of the R-wave. It reflects the time taken for excitation to spread from the endocardial to epicardial surface. RWPT in the unipolar chest leads reflect the depolarisation of the cardiac muscle immediately below it, where RWPT in V6 is considered a surrogate for lateral left ventricular activation in routine clinical care(1). However, the placement of V6 can vary between operators in addition to variation in the cardiac size and position, and so whether V6 truly remains representative of the left lateral wall is unknown. This has become more pertinent in recent years with the use of RWPT in confirmation of conduction tissue capture during conduction system pacing (CSP)(2). Purpose In this study we look to compare the gold standard and validated left ventricular lateral wall activation times of non-invasive electrical mapping with RWPT in multiple ECG leads to firstly confirm whether RWPT in V6 does represent lateral wall activation and secondly if this is the optimal lead to use for this purpose. Methods Patients undergoing CSP with left bundle branch area pacing (LBBAP) or His-bundle pacing (HBP) with simultaneous non-invasive mapping and 12-lead ECG annotation at a tertiary cardiac centre were identified. The left lateral wall was defined anatomically using non-invasive mapping and cardiac CT. The non-invasive left ventricular lateral wall activation time (LWAT) was measured from the stimulation artifact to the predefined anatomical area. These were compared with RWPT measurements taken from all leads in the same patients where an R-wave was apparent using an electrophysiology annotation system. Mean difference (MD), standard deviation of the difference (SD) and R2 were used to assess the agreement and correlation between the two measures. Results 39 patients undergoing CSP were identified. Several patients underwent more than one form of pacing during the same procedure. 16 patients underwent HBP, 15 underwent LBBAP and 26 underwent right ventricular pacing (RVP). Our results demonstrate the best correlation was seen in AVL followed by V6 in all parameters during LBBAP (MD 8.24; SD 70.36; R2 0.44 (P=0.013) vs MD 9.6; SD 79.45; R2 0.28 (P=0.042) respectively) with other leads showing poor agreement. During all forms of pacing (HBP, LBBAP, RVP), although weaker agreement was seen, AVL and V6 showed the best parameters, with AVL being better fitted across mean difference and R2 together (MD 7.26; SD 142.38; R2 0.056 (P=0.093) vs MD 14.96; SD 104.97; R2 0.15 (P=0.006) for AVL and V6 respectively). Conclusion We have identified that V6 RWPT does show reasonable correlation with lateral wall activation, however, AVL being a bipolar lead produced better agreement. This may be because limb leads have a more fixed position compared to chest leads and are less susceptible to the variation seen in cardiac size and position.