Differences in aortic cusp coaptation between the reimplantation and the remodeling techniques of aortic valve-sparing surgery: an in vitro porcine model study

Comparison of hemodynamics and root configurations between remodeling and reimplantation methods for valve-sparing aortic root replacement: a pulsatile flow study

PURPOSE

To compare the characteristics of reimplantation (RI) using grafts with sinuses and remodeling (RM) with/without external suture annuloplasty using a pulsatile flow simulator.

METHODS

Porcine aortic roots were obtained from an abattoir, and six models of RM and RI with sinuses were prepared. External suture annuloplasty (ESA) was performed in the RM models to decrease the root diameter to 22 mm (RM-AP22) and 18 mm (RM-AP18). Valve models were tested at mean pulsatile flow and aortic pressure of 5.0 L/min and 120/80 (100) mmHg, respectively, at 70 beats/min. The forward flow, regurgitation, leakage, backflow rates, valve-closing time, and mean and peak pressure gradient (p-PG) were evaluated. Root configurations were examined using micro-computed tomography (micro-CT).

RESULTS

The backflow rate was larger in the RM models than in the RI models (RI: 8.56% ± 0.38% vs. RM: 12.64% ± 0.79%; p < 0.01). The RM-AP and RI models were comparable in terms of the forward flow, regurgitation, backflow rates, p-PG, and valve-closing time. The analysis using a micro-CT showed a larger dilatation of the sinus of the Valsalva in the RM groups than in the RI group (Valsalva: RI, 26.55 ± 0.40 mm vs. RM-AP22, 31.22 ± 0.55 mm [p < 0.05]; RM-AP18, 31.05 ± 0.85 mm [p < 0.05]).

CONCLUSIONS

RM with ESA and RI with neo-sinuses showed comparable hemodynamics. ESA to RM reduced regurgitation.

4D flow CMR analysis comparing patients with anatomically shaped aortic sinus prostheses, tube prostheses and healthy subjects introducing the wall shear stress gradient: a case control study

BACKGROUND

Anatomically pre-shaped sinus prostheses (SP) were developed to mimic the aortic sinus with the goal to preserve near physiological hemodynamic conditions after valve-sparing aortic root replacement. Although SP have shown more physiological flow patterns, a comparison to straight tube prosthesis and the analysis of derived quantitative parameters is lacking. Hence, this study sought to analyze differences in aortic wall shear stress (WSS) between anatomically pre-shaped SP, conventional straight tube prostheses (TP), and age-matched healthy subjects) using time-resolved 3-dimensional flow cardiovascular magnetic resonance (4D Flow CMR). Moreover, the WSS gradient was introduced and analyzed regarding its sensitivity to detect changes in hemodynamics and its dependency on the expression of secondary flow patterns.

METHODS

Twelve patients with SP (12 male, 62 ± 9yr), eight patients with TP (6 male, 59 ± 9yr), and twelve healthy subjects (2 male, 55 ± 6yr) were examined at 3 T with a 4D Flow CMR sequence in this case control study. Six analysis planes were placed in the thoracic aorta at reproducible landmarks. The following WSS parameters were recorded: WSSavg (spatially averaged over the contour at peak systole), max. WSSseg (maximum segmental WSS), min. WSSseg (minimum segmental WSS) and the WSS Gradient, calculated as max. WSSseg - min. WSSseg. Kruskal-Wallis- and Mann-Whitney-U-Test were used for statistical comparison of groups. Occurrence and expression of secondary flow patterns were evaluated and correlated to WSS values using Spearman's correlation coefficient.

RESULTS

In the planes bordering the prosthesis all WSS values were significantly lower in the SP compared to the TP, approaching the physiological optimum of the healthy subjects. The WSS gradient showed significantly different values in the four proximally localized contours when comparing both prostheses with healthy subjects. Strong correlations between an elevated WSS gradient and secondary flow patterns were found in the ascending aorta and the aortic arch.

CONCLUSION

Overall, the SP has a positive impact on WSS, most pronounced at the site and adjacent to the prosthesis. The WSS gradient differed most obviously and the correlation of the WSS gradient with the occurrence of secondary flow patterns provides further evidence for linking disturbed flow, which was markedly increased in patients compared to healthy sub jects, to degenerative remodeling of the vascular wall.

Human cell-derived tissue-engineered heart valve with integrated Valsalva sinuses: towards native-like transcatheter pulmonary valve replacements

Transcatheter valve replacement indication is currently being extended to younger and lower-risk patients. However, transcatheter prostheses are still based on glutaraldehyde-fixed xenogeneic materials. Hence, they are prone to calcification and long-term structural degeneration, which are particularly accelerated in younger patients. Tissue-engineered heart valves based on decellularized in vitro grown tissue-engineered matrices (TEM) have been suggested as a valid alternative to currently used bioprostheses, showing good performance and remodeling capacity as transcatheter pulmonary valve replacement (TPVR) in sheep. Here, we first describe the in vitro development of human cell-derived TEM (hTEM) and their application as tissue-engineered sinus valves (hTESVs), endowed with Valsalva sinuses for TPVR. The hTEM and hTESVs were systematically characterized in vitro by histology, immunofluorescence, and biochemical analyses, before they were evaluated in a pulse duplicator system under physiological pulmonary pressure conditions. Thereafter, transapical delivery of hTESVs was tested for feasibility and safety in a translational sheep model, achieving good valve performance and early cellular infiltration. This study demonstrates the principal feasibility of clinically relevant hTEM to manufacture hTESVs for TPVR.

In vivo assessment of aortic root geometry in normal controls using 3D analysis of computed tomography

Aims

Understanding normal asymmetry in the aortic root could aid in the development of new surgical repair techniques or devices with improved haemodynamic performance. The purpose of this study was to assess geometric asymmetry and age-related changes in the normal aortic root using 3D computed tomography.

Methods and Results

The institutional review board approved this retrospective study of 130 normal subjects (mean age, 51.4 years; 58 men). Specialized 3D software measured individual cusp sinus volumes (CSVs), cusp surface areas (CSAs), and intercommissural distances (ICDs). Age-related aortic root changes were evaluated with simple correlation, ANOVA test among age groups, and multivariable linear regression analyses. The CSV and CSA of left coronary cusp (LCC) were significantly smaller than those of right coronary cusp (RCC) and non-coronary cusp (NCC) (both, P < 0.001) in all age groups. The mean ratios of RCC or NCC-to-LCC were 1.38 and 1.36 for CSV, 1.19 and 1.20 for CSA, and 1.21 and 1.06 for ICD, respectively. The CSV and ICD increased in older age with weak-to-moderate correlation coefficients in both men and women. By multivariable linear regression, CSVs and ICDs of all cusps showed a positive correlation with age (P < 0.05), and the female gender was associated with a smaller size of the CSV and CSA.

Conclusions

The LCC was significantly smaller than the other two cusps, and the aortic root size increased with age.

Aortic Valvuloplasty or Rootplasty for Aortic Regurgitation

At present, aortic valvuloplasty is considered an effective procedure for treatment of aortic regurgitation in pediatric patients. It has encouraging mid- and long-term results. The improved outcome is primarily related to better understanding of the functional anatomy of the normal valve and the different factors that alter it. It is also related to the realization that outcome after valvuloplasty is dependent on comprehensive repair of all of the involved components of the aortic root. Refinement in preoperative diagnosis has helped identify these abnormal components and focus the surgical approach on the needed reconstruction. Although the technical aspects of valvuloplasty are well defined, suboptimal long-term results still occur in some cases because the patch material used for valve repair can become fibrotic or calcified. This review summarizes the surgical approach to and the management of the different abnormal root components in pediatric patients with significant aortic valve regurgitation.

Should the annulus be fixed in aortic valve-sparing root replacement with remodeling?

OBJECTIVES

If the aortic root dilates after native aortic valve-sparing root reconstruction with remodeling, aortic regurgitation may recur. However, it has not been demonstrated clearly that the aortic root dilates after remodeling.

METHODS

This study enrolled 15 patients who underwent an aortic valve-sparing operation with remodeling (2002-2014) but without any ventriculo-aortic junction (VAJ) fixation. Technically, special care was taken to pass the sutures through the fibrous annulus. The diameter of the aortic root (VAJ, neosinus of Valsalva, and sinotubular junction), degree of aortic regurgitation, and effective height of the aortic valve were measured in the patients. All patients had postoperative follow-up, and the median follow-up period was 7.3 (IQR: 3.1-8.3) years.

RESULTS

The mean preoperative diameters of the VAJ, sinus of Valsalva, and sinotubular junction were 23.5 ± 2.3 (20-27) mm, 51.1 ± 7.2 (43-60) mm, and 42.4 ± 9.4 (29-58) mm, respectively. The postoperative diameters of the VAJ changed from 21.6 ± 2.6 (early) to 21.8 ± 2.9 mm (late) (p = 0.75). The diameters of the sinus of Valsalva and sinotubular junction changed from 26.5 ± 3.0 (early) to 28.5 ± 4.2 mm (late) (p = 0.0013), and 22.4 ± 3.0 (early) to 24.3 ± 3.3 mm (late) (p = 0.0003), respectively. The effective height of the aortic valve changed from 9.7 ± 1.3 (early) to 8.9 ± 2.0 mm (late) (p = 0.08). The degree of aortic regurgitation (grade: 0-4) changed from 0.3 ± 0.5 (early) to 1.2 ± 0.8 (late) (p = 01558).

CONCLUSIONS

Significant VAJ dilation and changes in aortic valve configuration after our remodeling procedure were not observed. Therefore, fixation of the annulus with remodeling may not be needed for cases without preoperative dilation of the annulus.

Impact of aortic annular geometry on aortic valve insufficiency: Insights from a preclinical, ex vivo, porcine model

OBJECTIVES

We sought to create a model of aortic insufficiency in a left heart simulator combined with 3-dimensional echocardiography and finite element modeling of the aortic valve. We examined the effects of aortic root geometry alteration on aortic insufficiency.

METHODS

Porcine aortic roots were analyzed on a left heart simulator before (control, n = 8) and after intervention (n = 8). Intervention entailed 3 vertical incisions at the sinotubular junction with diamond-shaped patches incorporated into the defects to increase the sinotubular junction diameter. Hemodynamic parameters were assessed, including regurgitant volume and fraction. Video and echocardiography images evaluated aortic valve function, coaptation surface area, aortic insufficiency, and effective regurgitant orifice area. Finite element modeling corroborated relationships between root geometry and aortic insufficiency, and examined cusp stress.

RESULTS

The intervention resulted in a sinotubular junction diameter increase of 55% ± 4%. The sinotubular junction to ventriculo-aortic junction diameter ratio was significantly higher in the intervention group (1.89 ± 0.16 vs 1.47 ± 0.04, P = .02). Increased sinotubular junction diameter resulted in aortic insufficiency assessed by regurgitant volume (28 ± 7 mL vs 5 ± 2 mL, P = .004), regurgitant fraction (36% ± 5% vs 7% ± 1%, P < .001), and effective regurgitant orifice (15 ± 5 mm(2) vs 0 mm(2), P = .016). Intervention coaptation surface area was smaller (1.03 ± 0.11 cm(2) vs 1.80 ± 0.08 cm(2), P < .001). There was a linear correlation between increased sinotubular junction/ventriculo-aortic junction ratio and regurgitant fraction (R(2) = 0.65, P = .003). The finite element modeling demonstrated a similar relationship between increasing sinotubular junction diameter and aortic insufficiency severity, and between end-diastolic cusp stresses and sinotubular junction diameters (R(2) = 0.98, P < .001).

CONCLUSIONS

In this model, increasing sinotubular junction diameter is linearly related to reduced coaptation surface area and increasing aortic insufficiency severity. This model provides new insights into aortic insufficiency mechanisms and may be used to evaluate novel interventions for aortic valve repair.

Is thoracic aortic disease a growing problem in Japan?

An article by Okita was recently published in General Thoracic and Cardiovascular Surgery. The paper thoroughly reviewed the surgical treatments for thoracic aortic disease in Japan. Valve-sparing aortic root operation, cerebral protection during aortic arch aneurysmectomy, and spinal cord protection during thoracoabdominal aneurysm repair are discussed in the present editorial.