Imaging, Valvular and Procedural Predictors
Heavy calcium volume has been identified as a predictor for pacemaker
insertion in prior studies. However, different studies have used
different parameters for the measurement of calcium burden including
aortic valve calcium score, porcelain aorta, landing zone calcification,
LVOT calcium, and mitral annulus calcification. In our analysis, high
calcium volume in the area extending below LVOTlc and
LVOTnc was found to be an important predictor. Our study
also determined implant depth to be another major predictor suggesting
the significance of higher deployment of the valve in the aortic area.
Implant depth was reported in individual studies as either
> 25% of stent frame below aortic annulus or
> 6 mm length of an implant from the lower edge of the
non-coronary cusp to the ventricular end of the prosthesis.
Increasing valve to aortic annulus oversizing ratios using multislice
computed tomography (CT) is known to reduce the rate of paravalvular
leak as the valve can fit better in the annulus (46). However, our
analysis determined this size discrepancy, between the valve and the
annulus, is associated with an increase in PPMI. The need for
pre-dilatation balloon valvuloplasty has been substantially reduced as
studies have shown direct TAVR is safe, feasible and has similar
outcomes (35, 47). Our analysis shows that both pre and post balloon
valvuloplasty are significant predictors of PPMI.
Since the introduction of TAVR, two valves have been widely used; the
balloon-expandable ESV and the self-expandable MCRS. The rate of PPMI is
markedly higher in the MCRS valve (44, 48). This higher rate has been
attributed to the difference in stent design, long nitinol frame, and
radial force exerted by the stent into the conduction tissue (49). The
balloon-expandable technology has evolved from XT to S3, and the
self-expandable technology has evolved to the Evolut R system. In the
analysis of 12,381 patients from different trials and registries by
Vlastra et al, new-generation BEV required PPMI less frequently when
compared to the new-generation SEV (S3: 8.9% vs Evolut: 18.1%). This
difference was greater in early-generation valves (ESV: 6.1% and XT:
7.5% vs MCRS: 21.2%) (44). The S3 valves were designed with a longer
stent frame which lead to decrease in the paravalvular leak, but
increased incidence of PPMI (7). Recently, modifications in the
implantation technique by high deployment of the valve has led to a
reduction in the rate of this complication (50).