The mechanistic interaction between mechanical dyssynchrony and filling pressure in cardiac resynchronisation therapy candidates

Figures

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  Figure 1. The different ECG-based indices of mechanical dyssynchrony assessment used in our study; (A) shows a still 2D image of the assessment of ApRock and SF (see Supplementary data online, Video S1 1); (B) shows the assessment of systolic stretch index (SSI) in a patient with LBBB which is the sum of the systolic pre-stretch of the lateral wall (SPSlat) and the systolic rebound stretch of the septum (SRSsept); (C) shows pressure-strain loops of the septum (S), and lateral wall (LW) of a patient with LBBB. The loop area represents the myocardial work where the LW–S work difference is the absolute difference in work values, calculated with the strain of each wall averaged over its mid- and basal-segments in the 4CH view. AVO, aortic valve opening; AVC, aortic valve closure.

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  Figure 2. Schematic representation of the computer simulations of the five virtual CRT candidates along with an indication of their mLAP. Starting from baseline normal condition, step one is inducing LBBB [simulation (1)]. Step 2 is simulating two types of LV dilatation with LVEF < 35%; (i) with preserved contractility [simulation (2)] and (ii) reduced contractility [simulation (3)]. Step 3 is increasing intrinsic myocardial stiffness in both simulations of LV dilatation [simulations (4) and (5)]. Note that simulations (1) and (2) were associated with normal mLAP, while simulations (3–5)] were associated with elevated mLAP. CO, cardiac output; HR, heart rate.

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  Figure 3. The association of estimated LAP, stratified into nLAP and eLAP , with ApRock/SF (A); SSI (B), and LW—septum (S) work difference (C).

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  Figure 4. The association of the combined ECG-based assessment of ApRock/SF and baseline LAP (LAP) with CRT outcome in terms of CRT-induced reverse LV remodelling (A) and long-term survival (B). eLAP, elevated LAP; LVESV, left ventricular end-systolic volume; nLAP, normal LAP.

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  Figure 5. CircAdapt simulations showing the association between mLAP and mechanical dyssynchrony in three conditions; LBBB in non-remodelled heart (left panel), LBBB + LV dilatation with ‘preserved’ contractility (middle panel), and LBBB + LV dilatation with ‘preserved’ contractility + increased myocardial stiffness (right panel). Mitral inflow E and A waves are shown in the upper row. Mechanical dyssynchrony is expressed using LV longitudinal strain patterns of the septum and LW (middle row) and difference in work density between the septum and LW (lower row). AVC, aortic valve closure; MVC, mitral valve closure; SRS, systolic rebound stretch (represented by black arrows); ΔW, the difference in work between the septum and LW (represented by the double head black arrow).

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  Figure 6. CircAdapt simulations showing the association between mLAP and mechanical dyssynchrony in three conditions; LBBB in non-remodelled heart (left panel), LBBB + LV dilatation with ‘reduced’ contractility (middle panel), and LBBB + LV dilatation with ‘reduced’ contractility + increased myocardial stiffness (right panel). Mitral inflow E and A waves are shown in the upper row. Mechanical dyssynchrony is expressed using LV longitudinal strain patterns of the septum and LW (middle row) and difference in work density between the septum and LW (lower row). AVC, aortic valve closure; MVC, mitral valve closure; SRS, systolic rebound stretch (represented by black arrows); ΔW, the difference in work between the septum and LW (represented by the double head black arrow).

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  Figure 7. Scatterplot of the five virtual CRT simulations in our study, illustrating the negative correlation between SSI as an index of mechanical dyssynchrony and Eed as an index of operating chamber stiffness). The colour map represents the value of mLAP in each simulation. (1) LBBB in non-remodelled LV; (2) LBBB + LV dilatation with ‘preserved’ contractility; (3) LBBB + LV dilatation with ‘reduced’ contractility; (4) LBBB + LV dilatation with ‘reduced’ contractility + stiffness, and (5) LBBB + LV dilatation with ‘preserved’ contractility + stiffness.