Purpose: To determine whether the acute haemodynamic response (AHR) to CRT is governed by LV lead deployment over the latest electrically activated segment (LEAS; electroanatomical mapping [Ensite]) or latest mechanically activated segment (LMAS; longest time to peak (TTP) circumferential strain on feature-tracking cardiovascular magnetic resonance (FT-CMR).
Methods: In this acute study, 14 CRT recipients with a pre-implantation CMR scan underwent CRT. The AHR was assessed using the change in the rate of rise of LV pressure (?dP/dt), in relation to AAI pacing. The LEAS was defined as a Q-LV>95ms. The LMAS was identified using as the latest contracting segment using TTP circumferential strain on FT-CMR, undertaken during intrinsic rhythm.
Results: There was a correlation between LEAS and ?dP/dt (r=0.66, p=0.01), but not between LMAS and ?dP/dt (r=0.36, p=0.21). In 12/14 (85.7%) patients, the LMAS was either within or adjacent to myocardial scar. There was no agreement between LEAS and LMAS in 11/14 (78.6%) patients.
Conclusion: Targeting LV pacing to LEAS achieves a superior AHR than targeting to LMAS. LMAS are likely to harbour myocardial scars. These findings support the use of an electrical rather than a mechanical (imaging) approach to LV lead deployment in CRT.