Myocardial work analysis of aortic stenosis parients with right ventricular pacing: interaction of afterload and mechanical dyssynchrony?

It is well known that left ventricular (LV) performance is substantially influenced by the corresponding loading conditions and LV synchrony. Notably, data are scarce about the interaction of these factors: previous studies suggest that patients with left bundle branch block (LBBB) has increased afterload sensitivity. This phenomenon may have special importance in certain clinical situations, such as aortic stenosis (AS) patients with concomitant right ventricular pacing (RVP).

Accordingly, our aim was to investigate the effects of RVP on LV function in patients with severe AS before and after transcatheter aortic valve replacement (TAVR).

Patients with a previously implanted pacemaker and significant AS undergoing TAVR in our Institute were screened. Only subjects with intrinsic non-LBBB QRS were enrolled (n=31). Detailed echocardiographic protocol suitable for speckle-tracking and myocardial work analysis was obtained. Myocardial work measures were calculated by estimating LV pressure as the sum of the systolic blood pressure and the mean aortic gradient. The patients underwent two sets of echocardiographic examinations: one with their narrow QRS rhythm and one with RVP. Those patients (n=19), who did not develop LBBB or complete AV-block also underwent a post-TAVI protocol. We measured LV ejection fraction (EF), global longitudinal strain (GLS) and also global work index (GWI) and global wasted work (GWW).

Preoperatively, RVP resulted in significantly lower LV EF (55±9 vs. 49±10%, p≤0.001), GLS (-14.2±3.6 vs. -11.9±3.5%, p≤0.001) and GWI (1830±502 vs. 1322±546 mmHg%, p≤0.001) compared to narrow QRS rhythm, while GWW was markedly higher (222±129 vs. 344±146 mmHg%, p≤0.001). After TAVR, LV EF was comparable (55±9 vs. 52±8%, p=0.11), while GLS (-13.8±.3.8 vs. -11.4±3.8%, p≤0.001) and GWI (1360±403 vs. 1018±385 mmHg%, p≤0.01) was lower in RVP. Notably, the relative change in GWI in response to RVP was significantly lower after TAVR (-31±21 vs. -22±20%, p≤0.05).

In patients with severe AS, LV dyssynchrony associated with RVP results in markedly lower LV functional measures. TAVR alleviates LV pressure overload, and the detrimental effect of RVP may dampen with the afterload reduction. Significant AS and RVP may have a highly unfavorable interaction raising the need for early interventions in this population.