Aortic Root Rupture

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Aortic Root Rupture

Aortic root rupture after TAVI shares several aspects with coronary occlusion: 1) the frequency: a recent meta-analysis and a multicentre study reported a cumulative LVOT and annulus rupture rates of 1.1 % and 0.9 %, respectively;^2,7 2) this complication is a particular concern with balloon-expandable prostheses because of the significant force applied during balloon deployment;^7,17 3) clinical presentation, which can be dramatic: patients experiencing aortic root rupture (particularly those with uncontained rupture) develop sudden haemodynamic compromise and cardiogenic shock often unresponsive to inotropes.⁷

In such cases, median sternotomy and conversion into conventional aortic valve replacement usually represents the sole resort. Nevertheless, uncontained aortic root rupture is burdened by a very high mortality rate (75 % in our previous series). Differently, periaortic haematoma (also named ‘contained aortic root rupture’) carries a better prognosis, even though it belongs to the spectrum of the same pathology.^7,17 Indeed, among 11 cases of periaortic haematoma reported in the same study, all patients were alive at 30 days.⁷

The question is: is it possible to predict aortic rupture and to apply any strategy to prevent it? In this context, 3D MDCT has been shown to provide a deeper understanding of aortic annular geometry and allow for prediction of aortic rupture.¹⁰ Recently, we showed that there are at least two important features associated with annular rupture/periaortic haematoma: 1) moderate or severe LVOT/subannular calcification (see Figure 6), and 2) significantly oversized prostheses (≥20 % area oversizing).⁷ Calcification in the LVOT is a particular concern in the context of TAVI, because this is a rigid, thin-walled structure. Therefore, detailed assessment of the distribution of calcium within the aortic root and LVOT may provide important additional information regarding the risk of aortic root injury. A recent observation suggests high LVOT/subannular region it is calcium located below the non-coronary cusp that is most predictive of aortic root injury.¹⁸ The reason for this finding is not entirely clear. Previous observations have suggested that the left aortic sinus may be the most vulnerable area with regard to aortic root injury possibly due to lack of supporting cardiac structures in this area.^17,19 However, it may be speculated whether the culprit site is located at the site of calcification or at the aortic wall opposite to the calcification due to THV migration away from hard calcified areas during balloon expansion.

Historically, it has been shown that a certain degree of annular oversizing (5–1 5 % by area) is essential to mitigate the risk of significant paravalvular regurgitation with balloon-expandable valves.²⁰ However, greater oversizing (>20 % by area) is indicated in borderline or transitional annulus, considering that available balloon-expandable valves have been available in 3 mm diameter increments, with nominal expanded diameters of 20, 23, 26 and 29 mm.²¹ In such situations (particularly when significant LVOT calcification, shallow sinuses of Valsalva or highly calcified aortic cusps are present), it may be safer to proceed with self-expanding (CoreValve, etc.) or inflatable (Direct Flow) TAVI platforms, which are rarely associated with annular rupture, when post-dilation is not performed. Alternatively, a recent approach of intentionally underexpanding balloon-expandable THVs by underfilling the deployment balloon has been proposed;²¹ this technique produced predictable reduction of THV expansion without adversely affecting procedural or short-term clinical or echocardiographic outcomes.²¹

Finally, in those cases of incomplete THV expansion causing residual paravalvular regurgitation, greater caution should be taken when performing balloon postdilatation in patients with significant LVOT calcification or shallow sinuses of Valsalva. This important factor will be likely addressed with the introduction of the new generation of balloon-expandable THV (SAPIEN 3, Edwards Lifesciences, Irvine, CA). In fact, it was recently demonstrated that a lesser degree of MDCT area oversizing might be employed for this new balloon-expandable THV.²²