Tricuspid Regurgitation
Tricuspid regurgitation (TVR) is a well-documented complication of both TVPs and LPs. A study assessing the impact of LPs on atrioventricular valve function over a 12-month period showed TVR to be graded more severe in 43% of patients as discussed above [9]. Compared to the mechanisms of TVR due to TVPs discussed above, potential mechanisms for TVR after LP implantation include valve damage during implantation, chronic mechanical interaction of the device with the valve or sub valvular apparatus, or pacing-induced dyssynchrony resulting in ventricular dysfunction and increased filling pressures [9 15]. However, the degree of TVR worsening after LP implantation is likely lower than after TVP implantation due to the difference in mechanism, but the data on TVR after LP implantation is not robust.
Unlike PICM, the degree of RV pacing has not been shown to correlate with new onset or worsening TR in TVPs. Additionally, a recent study of patients with LPs showed no evidence of worsening TVR in the first 2 months post-implantation, making it unlikely that damage during implantation is a major contributor to worsening TVR in this population [16]. A recent study showed a 15% increase in the odds for worse TVR for each 1mm increase in distance between the LP and the tricuspid valve annulus [15]. The likely mechanical impact of the LP on TVR may be due to more chronic fibrotic changes that interfere with the chordae tendineae, sub-valvular apparatus, or valve more directly.
The change in the degree of tricuspid valve regurgitation was highly variable in our study with TVR graded to be more severe than baseline in 37% of patients, unchanged in 32%, and improved in 30%. Additionally, the average change was an increase in TVR by 0.28 grades. As a result, our study did not clearly show LP having a significant impact on TVR. Statistical analysis revealed no pattern of TVR that would predict patients who were more likely to have worsening of their TVR post-implantation.
Interestingly, though the LP implantation did not have a significant effect on TVR severity overall, the average degree of TVR worsening was higher in the mid septum group with an average increase in TVR by 0.67 grades. This is in comparison to the apical septum group which had an average increase of only 0.04 grades. The study population is too small to generate conclusions based on this pattern, but it could suggest that implantation of LPs on the mid septum leads to increased interaction with the tricuspid valve apparatus thereby leading to increased TVR.