Introduction Left bundle branch block (LBBB) is common following trans-catheter aortic valve implantation (TAVI) and has been linked to increased mortality, although whether this is due to the development of a TAVI-induced LBBB cardiomyopathy is unclear.
Methods 48 patients undergoing TAVI for severe aortic stenosis were evaluated. 24 patients with TAVI-induced LBBB (LBBB-T) were matched with 24 patients with a narrow post-procedure QRS (nQRS). Patients underwent comprehensive Cardiovascular Magnetic Resonance (CMR) imaging prior to and 6m post-TAVI. Measured cardiac reverse remodelling parameters included left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and left sided chamber size. Inter and intraventricular dyssynchrony was determined using time to peak radial strain derived from CMR Feature Tracking.
Results In the nQRS group there was no change in QRSd (93 ± 17 to 96 ± 11 ms, p = 0.098). In the LBBB-T group, QRSd increased by a mean of 55 ms from 96 ± 14 to 151 ± 12 (p=<0.001). There was a significant difference in change in LVEF and GLS according to post-procedure QRS duration (LVEF: nQRS 4.6 ± 7.8 vs LBBB-T -2.1 ± 6.9%, p = 0.002; GLS: nQRS 2.1 ± 3.6 vs. LBBB-T -0.2 ± 3.2%, p = 0.024) (Figure 1). Those in the nQRS group had a significant improvement in LVEF (54.1 ± 11.5 to 58.7 ± 9.0%, p = 0.010) and GLS (15.6 ± 3.9 to 17.7 ± 2.7, p = 0.010) at 6 m follow up. There was a trend towards a reduction in LVEF in the LBBB-T group (56.6 ± 10.5 to 54.4 ± 9.3%, p = 0.092). The change in LVEF was driven by a reduction in indexed end-systolic volume in the nQRS group not seen in the LBBB-T group (nQRS -7.9 ± 14.0 vs. LBBB-T -0.6 ± 10.2 ml/m2, p = 0.02). Further CMR characteristics can be seen in Table 1. Those with LBBB-T exhibited significant interventricular dyssynchrony 6m follow up compared with the nQRS population (LBBB-T 130 ± 73 ms vs nQRS 23 ± 86 ms, p=<0.001). Intraventricular dyssynchrony was also demonstrated in the LBBB-T at 6 m; 118 ± 103 ms compared with 13 ± 106 ms (p = 0.001) in the nQRS group. There was a significant correlation between post procedure QRS and interventricular and intraventricular dyssynchrony (r = 0.57, p=<0.001 and r = 0.49, p=<0.001 respectively). Neither group experienced any change in right ventricular longitudinal function (nQRS 21.7 ± 7.0 to 21.5 ± 6.2 mm, p = 0.817, LBBB-T 18.9 ± 5.8 to
18.6 ± 5.8 mm, p = 0.773). Post-procedure aortic regurgitant fraction was similar between groups (nQRS 5.4 ± 5.7 vs LBBB-T 5.5 ± 3.3%, p = 0.948). There was an inverse correlation between QRS duration and change in LVEF (r=-0.46, p = 0.001) and QRS duration and change in LV GLS (r=-0.37, p = 0.010).
Conclusion LBBB-T is associated with less favourable cardiac reverse remodelling at medium term follow up. In view of this, every effort should be made to prevent TAVI-induced LBBB, especially as TAVI is extended to a younger, lower risk population.
- Transcatheter aortic valve implantation
- Left bundle branch block
- Left ventricular ejection fraction
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