Paravalvular Leak After Transcatheter Aortic Valve Implantation: Importance of Preprocedural Variables and Intraprocedural Assessment

Paravalvular leak (PVL) after transcatheter aortic valve implantation (TAVI) is common and reported to occur more frequently than after surgical aortic valve replacement. ¹ In this context, Rooijakkers et al. ² present in this issue of the Journal of the American Heart Association (JAHA) their analyses on the use of hemodynamic indices and videodensitometry (VD) for intraprocedural assessment of PVL after TAVI. In this post hoc analysis of the APPOSE (Assessment of Paravalvular Leak After TAVI by Hemodynamic Measurements and Cardiac Magnetic Resonance Imaging) trial (NCT04281771; an investigator‐initiated, prospective single‐center study evaluating the accuracy of periprocedural assessment of hemodynamic indices to predict relevant PVL), the authors compared the predictive value of the isolated versus combined use of the hemodynamic index diastolic delta (DD) and VD for the incidence of relevant PVL 1 month after TAVI. Their study revealed that DD and VD are both accurate and feasible modalities for the assessment of PVL after TAVI and the synergistic use of both techniques increases the predictive value for relevant PVL after TAVI.

Although the authors evaluated an intraprocedural aspect to predict PVL after TAVI within 1 month, we should first highlight the importance of prerocedural prediction based on the identification of well‐known risk factors for PVL after TAVI about which patients should be informed when choosing between TAVI and surgical aortic valve replacement (Figure).

Figure 1. Paravalvular leak after transcatheter aortic valve implantation.

LVOT indicates left ventricle outflow tract; PVL, paravalvular leak; TAVI, transcatheter aortic valve implantation; and THV, transcatheter heart valve.

Calcification of the native valve leaflets, commissures, or annulus might prevent appropriate sealing of the transcatheter heart valve (THV) in relation to the usual circular tissue of the aortic valve, which increases the risk for PVL. ³ Cutoff values for the Agatston score (aortic valve calcium score) as predictor for moderate PVL have been investigated, suggesting threshold values of 4070 for men, and 2341 for women. ⁴ Furthermore, significant left ventricle outflow tract (LVOT) calcification is associated with moderate/severe PVL in both types of THVs (self‐expanding and balloon‐expandable). ⁵

Although TAVI has revolutionized the therapy for severe aortic stenosis, mixed aortic valve disease treated by TAVI has sparked more interest recently, as those patients represent a more complex cohort when compared with those with isolated aortic stenosis. Mixed aortic valve disease is associated with higher risk for PVL and worse outcomes compared with isolated aortic stenosis. ⁶

Another important consideration is the typical elliptical shape of the aortic annulus, in contrast to the circular shape of THVs, which may result in incomplete apposition of the THV frame. To account for the geometric mismatch between the aortic annulus and THV frames, the eccentricity index—calculated as 1 minus (minimal annular diameter/maximal annular diameter)—was introduced as a metric to quantify aortic annular eccentricity. An eccentricity index >0.35 has been independently associated with significant PVL. ⁷

Bicuspid aortic valves have been also found as a source of anatomic challenges for TAVI because they are associated with risky anatomic features such as large elliptical annulus, fibrotic/calcified raphe, and severe calcification of the leaflets, the annulus, or LVOT. The development of new TAVI techniques and some features of new‐generation THVs have targeted these anatomical concerns, making TAVI procedures reasonably safe in bicuspid aortic valve stenosis. Nevertheless, bicuspid aortic valves remain associated with higher rates of TAVI‐related issues (such as PVL), ⁸ with associated increased risks of long‐term morbidity and mortality due to PVL (even if mild). ⁹ In this scenario, new‐generation balloon‐expandable THVs have been associated with significantly less PVL when compared with new‐generation self‐expanding THVs. ¹⁰ Despite some improvements, moderate/severe PVL still occurs in about 4% of cases of current‐generation THVs in Sievers type 1 bicuspid aortic valve stenosis and is associated with an increased risk of major adverse events including all‐cause death, stroke, or hospitalization for heart failure. ¹¹ Implantation depth, which is highly operator dependent, either excessively deep or shallow, can cause relevant PVL. When the THV is implanted exceedingly high (regardless of bicuspid or trileaflet aortic valve), PVL results from inadequate apposition and anchoring of the THV, which leads to inadequate sealing between the THV and aortic annulus.

Various techniques are available to diagnose and assess severity of PVL: angiography, echocardiography, invasive hemodynamic parameters, VD, and cardiac magnetic resonance (Figure).

Aortic root angiography (as described by Sellers et al. ¹² ) is the most widely used imaging method for grading PVL and is readily available during TAVI, but it has low reproducibility because the quantification is based on visual estimation and it is highly dependent on technical factors (intensity/projection of fluoroscopy, position of the catheter through which the contrast will be infused, amount/speed of contrast injection, etc.). ³ The reproducibility of PVL grading by angiography can be improved by VD ¹³ and this technique has been validated against cardiac magnetic resonance and echocardiography. ³ , ¹³ , ¹⁴ , ¹⁵ In the study by Rooijakkers et al., ² time‐density curves were generated in the LVOT (region of interest) and in the aortic root where the contrast was injected (reference area). From these time‐density curves, the area under the time‐density curve was automatically computed to represent the time‐density integral. The regurgitant fraction was calculated by dividing the area under the time‐density curve of the LVOT by the area under the time‐density curve of the aortic root. ¹⁴

The Valve Academic Research Consortium‐3 recommends echocardiography as the primary imaging method for the evaluation of PVL. ¹⁶ Transthoracic echocardiography is easily available, inexpensive, and noninvasive. However, transthoracic echocardiography may not be ideal to diagnose posterior PVL jets. ³ , ¹⁷ Transesophageal echocardiography is superior to transthoracic echocardiography with better resolution and image quality to discriminate PVL from central regurgitation and establish the mechanism of PVL. However, transesophageal echocardiography is invasive, frequently requires sedation and may not visualize adequately anterior PVL jets. ³ , ¹⁷

Cardiac magnetic resonance enables precise and reproducible quantitative measurement of regurgitant volume, regardless of morphology, number of the PVL jets, and type of THV, ³ , ¹⁸ but it might slightly overestimate the severity of PVL due to the inclusion of diastolic coronary flow in the calculation of total regurgitant volume ³ , ¹⁹ and it is not available during the TAVI procedure.

Hemodynamic parameters can be derived from transvalvular pressure tracings post‐TAVI and advantageously, these pressure tracings do not require additional procedural time or contrast agents and can be measured immediately after the procedure. ³ In the study by Rooijakkers et al., ² the authors evaluated one of these hemodynamic parameters: the index DD which is defined as “diastolic blood pressure – left ventricle end‐diastolic pressure.” In previous studies, DD ≤18 mm Hg ²⁰ was independently associated with an increased risk of death after TAVI. In the study by Rooijakkers et al., ² the correlation between DD and VD was weak, but both DD and VD showed comparable accuracy to predict relevant PVL. Most important, the combination of DD and VD improved the prediction of relevant PVL, resulting in an increased concordance (86.3%) and positive predictive value (75%) compared with DD alone (76.5% and 40%, respectively), or VD alone (82.3% and 50%, respectively).

One final detail to emphasize in the study by Rooijakkers et al. ² is that it was conducted exclusively with the Abbott Portico valve. This raises two important considerations. First, the use of a single THV limits the direct applicability of the findings to other THVs. Second, the study was conducted between November 2019 and October 2021, before the new iteration of the Portico valve, Navitor, became available.

This is important because the new Navitor iteration has multiple differences from its early iteration. First, it has optimized radial force for expansion, anchoring, stability, and sealing. Next, it has an inner cuff of a fabric material which maintains a low profile. Next, it has an outer cuff which actively synchronizes to the cardiac cycle to seal and mitigate PVL and finally, it has an increased sealing zone in comparison with the previous iteration, which also mitigates PVL. All these features are intended to render this THV less susceptible to PVL and their presence might have substantially changed the findings of this subanalysis of the APPOSE trial.

With the ongoing expansion of TAVI use in younger and lower risk patients with longer life expectancy, the assessment of procedural risk will highly likely move from the “mortality risk assessment” to a more holistic evaluation that will consider other TAVI‐related issues such as risk of PVL, permanent pacemaker implantation, and prosthesis–patients mismatch with some emphasis on the impact of these complications on long‐term patient outcomes. Regarding the risk and assessment of PVL after TAVI, special attention should be paid to this issue before, during and after the procedure because it can affect outcomes and the lifetime management of patients with aortic valve diseases.

Disclosures

None.