Ross Procedure and Left Ventricular Mass Regression

Aortic Valve Embryology, Mechanobiology, and Second Messenger Pathways: Implications for Clinical Practice

During the Renaissance, Leonardo Da Vinci was the first person to successfully detail the anatomy of the aortic root and its adjacent structures. Ever since, novel insights into morphology, function, and their interplay have accumulated, resulting in advanced knowledge on the complex functional characteristics of the aortic valve (AV) and root. This has shifted our vision from the AV as being a static structure towards that of a dynamic interconnected apparatus within the aortic root as a functional unit, exhibiting a complex interplay with adjacent structures via both humoral and mechanical stimuli. This paradigm shift has stimulated surgical treatment strategies of valvular disease that seek to recapitulate healthy AV function, whereby AV disease can no longer be seen as an isolated morphological pathology which needs to be replaced. As prostheses still cannot reproduce the complexity of human nature, treatment of diseased AVs, whether stenotic or insufficient, has tremendously evolved, with a similar shift towards treatments options that are more hemodynamically centered, such as the Ross procedure and valve-conserving surgery. Native AV and root components allow for an efficient Venturi effect over the valve to allow for optimal opening during the cardiac cycle, while also alleviating the left ventricle. Next to that, several receptors are present on native AV leaflets, enabling messenger pathways based on their interaction with blood and other shear-stress-related stimuli. Many of these physiological and hemodynamical processes are under-acknowledged but may hold important clues for innovative treatment strategies, or as potential novel targets for therapeutic agents that halt or reverse the process of valve degeneration. A structured overview of these pathways and their implications for cardiothoracic surgeons and cardiologists is lacking. As such, we provide an overview on embryology, hemodynamics, and messenger pathways of the healthy and diseased AV and its implications for clinical practice, by relating this knowledge to current treatment alternatives and clinical decision making.

Biomechanics of Pulmonary Autograft as Living Tissue: A Systematic Review

INTRODUCTION

The choice of valve substitute for aortic valve surgery is tailored to the patient with specific indications and contraindications to consider. The use of an autologous pulmonary artery (PA) with a simultaneous homograft in the pulmonary position is called a Ross procedure. It permits somatic growth and the avoidance of lifelong anticoagulation. Concerns remain on the functionality of a pulmonary autograft in the aortic position when exposed to systemic pressure.

METHODS

A literature review was performed incorporating the following databases: Pub Med (1996 to present), Ovid Medline (1958 to present), and Ovid Embase (1982 to present), which was run on 1 January 2022 with the following targeted words: biomechanics of pulmonary autograft, biomechanics of Ross operation, aortic valve replacement and pulmonary autograph, aortic valve replacement and Ross procedure. To address the issues with heterogeneity, studies involving the pediatric cohort were also analyzed separately. The outcomes measured were early- and late-graft failure alongside mortality.

RESULTS

a total of 8468 patients were included based on 40 studies (7796 in pediatric cohort and young adult series and 672 in pediatric series). There was considerable experience accumulated by various institutions around the world. Late rates of biomechanical failure and mortality were low and comparable to the general population. The biomechanical properties of the PA were superior to other valve substitutes. Mathematical and finite element analysis studies have shown the potential stress-shielding effects of the PA root.

CONCLUSION

The Ross procedure has excellent durability and longevity in clinical and biomechanical studies. The use of external reinforcements such as semi-resorbable scaffolds may further extend their longevity.

The Ross procedure is the optimal solution for young adults with unrepairable aortic valve disease

While aortic valve repair remains the ideal intervention to restore normal valvular function, the optimal aortic valve substitute for patients with a non-repairable aortic valve remains an ongoing subject for debate. In particular, younger patients with a non-repairable valve represent a unique challenge because of their active lifestyle and long life expectancy, which carries a higher cumulative risk of prosthesis-related complications. The Ross procedure, unlike prosthetic or homograft aortic valve replacement (AVR), provides an expected survival equivalent to that of the age and gender-matched general population. Contemporary data has shown that the Ross procedure can be performed safely in centers with expertise, and is associated with improved valvular durability, hemodynamics and quality of life.

Valve performance classification in 630 subcoronary Ross patients over 22 years

OBJECTIVE

To define the function of the "Ross valves" and its clinical meaning in a practical valve performance classification as part of the outcome analysis.

METHODS

From 1994 to 2017, 630 consecutive patients underwent the subcoronary Ross procedure at our institution. The valve performance classification combines hemodynamics, symptoms, and management criteria. Median follow-up was 12.5 years (maximum 22.3 years, 7404 patient-years, 99.4% completeness).

RESULTS

The mean age of the patients was 44.7 ± 11.9 years. Hospital deaths was 0.3% (n = 2). Twenty years after the operation survival was 73.1% (95% confidence interval [CI], 65.4%-81.6%) and statistically not different from the age- and gender-matched general population; freedom from reoperation was 85.9% (95% CI, 80.2%-92.0%; 0.6% per patient-year), 89.8% (95% CI, 84.3%-95.7%) for autograft, and 91.0% (95% CI, 86.3%-96.0%) for homograft. Preoperative annulus diameter, aortic regurgitation, annulus reinforcement, sinotubular junction reinforcement, and bicuspid aortic valve type were no significant risk factors for reoperation. At 20 years the probability of a patient being in valve performance class I to IV was 5%, 74%, 19%, and 1%, respectively. Time to reoperation was not different in bicuspid and tricuspid aortic valves; preoperative aortic stenosis tended to have better outcome of autograft function.

CONCLUSIONS

These up to 22 years data show that the subcoronary Ross procedure continues to provide an excellent tissue aortic valve replacement. The suggested valve performance classification emerged as a practical concept for outcome analysis with the probability of 79% being in the favorable class I or II at 20 years.

The Impact of Aortic Valve Replacement on Left Ventricular Remodeling in Children

There are scant data in pediatrics on the optimal timing for aortic valve repair (AVR). This study assesses the midterm response to AVR and possible predictors of poor outcome. From 2001 to 2006, 41 patients had greater than 3-month follow-up after AVR for aortic insufficiency, aortic stenosis, or both. Pre-, peri-, and post-operative data were collected, including demographics and clinical symptoms. Two reviewers measured echocardiographic parameters from the pre-operative and latest follow-up echocardiograms. Ventricular dimensions were indexed to body surface area (z-score). Median age at AVR was 13 years with 83 % having a Ross operation. The average left ventricular end-diastolic dimension pre-op, z-score of +1.3, significantly decreased at last follow-up to a mean z-score of -0.1 (p < 0.001). Similarly the indexed LV mass decreased from +3.9 to +0.5 (p < 0.001). There was no significant correlation between the presence of pre-op symptoms and the presence of post-op LV dilatation, hypertrophy, or dysfunction. In the subset of patients (7/41) with persistent LV dysfunction at last follow-up, there was a significant correlation with pre-op LV dilatation as assessed by both LVEDD (p = 0.02) and LVESD (p = 0.05). Children demonstrate significant reverse remodeling after AVR. Pre-op LV dilatation may predict patients with persistent LV dysfunction post-AVR. Symptoms are less useful in children, suggesting the need for more objective data for functional assessment.

Regression of left ventricular hypertrophy in children following the Ross procedure

OBJECTIVES

Left ventricular hypertrophy (LVH) frequently accompanies the progression of aortic valve disease in children. The extent of LVH regression following surgical relief of aortic valve disease in children has not been clearly elucidated. We hypothesized that significant regression of LVH will occur in children following the Ross procedure.

METHODS

We examined LVH over time in children <18 years of age who underwent the Ross procedure. Left ventricular mass index (LVMI) and corresponding z scores were calculated based on height, age and gender. Left ventricular hypertrophy was defined as an LVMI of > 39 g/m(2.7) and a z score of >1.6.

RESULTS

Twenty-five children underwent the Ross procedure. The left ventricular mass increased proportionally with the growth of the child from baseline to the latest follow-up at 7.3 ± 2.9 years (121.1 ± 81.5 vs 133.1 ± 79.8 g, P = 0.4). However, 96% (24/25) of children demonstrated LVMI regression from baseline. Mean LVMI decreased from 70.8 ± 31.2 to 41.8 ± 16.6 g/m(2.7) (P < 0.001). Similarly, LVMI z scores decreased from 2.2 ± 1.2 to 0.2 ± 1.9 (P < 0.001). Freedom from LVH was 83% at 10 years. Examination of LVMI and z scores over time demonstrated that the largest decrease occurred after the first year, with continued gradual decline over 10 years of follow-up.

CONCLUSIONS

The Ross procedure is effective in reversing LVH in children with aortic valve disease.

Neoaortic root diameters and aortic regurgitation in children after the Ross operation

BACKGROUND

For children who require aortic valve replacement, the Ross operation provides a unique advantage of growth potential of the pulmonary autograft in the aortic position. This study assessed the progression of autograft root diameters and its effect on aortic regurgitation (AR).

METHODS

Neoaortic echo dimensions from 48 children (<16 years) undergoing Ross operation who had follow-up echocardiograms before age 20 were analyzed (mean follow-up, 5.1 +/- 3.3 years).

RESULTS

The mean age at the time of the Ross operation was 10.0 +/- 4.3 years. Mean z values of the neoaortic annulus (1.5 +/- 0.4), sinus (2.5 +/- 0.4), and sinotubular junction (2.6 +/- 0.9) when the autograft was implanted were significantly larger compared with normal values (p < 0.001, all). The mean z values significantly increased with follow-up at the level of the sinus (0.5 +/- 0.1/year, p < 0.001) and the sinotubular junction (0.7 +/- 0.2, p < 0.001), but not at the level of the annulus (0.1 +/- 0.1, p = 0.59). AR increased with follow-up time (0.07 +/- 0.02 grade/year, p < 0.001). AR increased with sinotubular junction diameter (p = 0.028), but there was not significant evidence of an association with annulus diameter (p = 0.25) or sinus diameter (p = 0.40).

CONCLUSIONS

Children undergoing Ross operation have larger neoaortic root dimensions than healthy children. Growth of the annulus matches somatic growth. The diameters of the sinus and the sinotubular junction increase significantly relative to somatic growth. The latter may explain the development of AR.

The Ross Procedure

Background— Reports on outcome after the Ross procedure are limited by small study size and show variable durability results. A systematic review of evidence on outcome after the Ross procedure may improve insight into outcome and potential determinants.

Methods and Results— A systematic review of reports published from January 2000 to January 2008 on outcome after the Ross procedure was undertaken. Thirty-nine articles meeting the inclusion criteria were allocated to 3 categories: (1) consecutive series, (2) adult patient series, and (3) pediatric patient series. With the use of an inverse variance approach, pooled morbidity and mortality rates were obtained. Pooled early mortality for consecutive, adult, and pediatric patients series was 3.0% (95% confidence interval [CI], 1.8 to 4.9), 3.2% (95% CI, 1.5 to 6.6), and 4.2% (95% CI, 1.4 to 11.5). Autograft deterioration rates were 1.15% (95% CI, 1.06 to 2.06), 0.78% (95% CI, 0.43 to 1.40), and 1.38%/patient-year (95% CI, 0.68 to 2.80), respectively, and for right ventricular outflow tract conduit were 0.91% (95% CI, 0.56 to 1.47), 0.55% (95% CI, 0.26 to 1.17), and 1.60%/patient-year (95% CI, 0.84 to 3.05), respectively. For studies with mean patient age >18 years versus mean patient age ≤18 years, pooled autograft and right ventricular outflow tract deterioration rates were 1.14% (95% CI, 0.83 to 1.57) versus 1.69% (95% CI, 1.02 to 2.79) and 0.65% (95% CI, 0.41 to 1.02) versus 1.66%/patient-year (95% CI, 0.98 to 2.82), respectively.

Conclusions— The Ross procedure provides satisfactory results for both children and young adults. Durability limitations become apparent by the end of the first postoperative decade, in particular in younger patients.

Autograft regurgitation and aortic root dimensions after the Ross procedure: the German Ross Registry experience

BACKGROUND

Autograft regurgitation and root dilatation after the Ross procedure is of major concern. We reviewed data from the German Ross Registry to document the development of autograft regurgitation and root dilatation with time and also to compare 2 different techniques of autograft implantation.

METHODS AND RESULTS

Between 1990 and 2006 1014 patients (786 men, 228 women; mean age 41.2+/-15.3 years) underwent the Ross procedure using 2 different implantation techniques (subcoronary, n=521; root replacement, n=493). Clinical and serial echocardiographic follow up was performed preoperatively and thereafter annually (mean follow up 4.41+/-3.11 years, median 3.93 years, range 0 to 16.04 years; 5012 patient-years). For statistical analysis of serial echocardiograms, a hierarchical multilevel modeling technique was applied. Eight early and 28 late deaths were observed. Pulmonary autograft reoperations were required in 35 patients. Initial autograft regurgitation grade was 0.49 (root replacement 0.73, subcoronary 0.38) with an annual increase of grade 0.034 (root replacement 0.0259, subcoronary 0.0231). Annulus and sinus dimensions did not exhibit an essential increase over time in both techniques, whereas sinotubular junction diameter increased essentially by 0.5 mm per year in patients with root replacement. Patients with the subcoronary implantation technique showed nearly unchanged dimensions. Bicuspid aortic valve morphology did not have any consistent impact on root dimensions with time irrespective of the performed surgical technique.

CONCLUSIONS

The present Ross series from the German Ross Registry showed favorable clinical and hemodynamic results. Development of autograft regurgitation for both techniques was small and the annual progression thereof is currently not substantial. Use of the subcoronary technique and aortic root interventions with stabilizing measures in root replacement patients seem to prevent autograft regurgitation and dilatation of the aortic root within the timeframe studied.

A Critical Reappraisal of the Ross Operation

Background— The autograft procedure, an option in aortic valve replacement, has undergone technical evolution. A considerable debate about the most favorable surgical technique in the Ross operation is still ongoing. Originally described as a subcoronary implant, the full root replacement technique is now the most commonly used technique to perform the Ross principle.

Methods and Results— Between June of 1994 and June of 2005, the original subcoronary autograft technique was performed in 347 patients. Preoperative, perioperative, and follow-up data were collected and analyzed. Mean patient age at implantation was 44±13 years (range 14 to 71 years; 273 male, 74 female). Bicuspid valve morphology was present in 67%. The underlying valve disease was aortic regurgitation in 111 patients, stenosis in 46 patients, combined lesion in 188 patients, and active endocarditis in 22 patients (in 2 patients without stenosis or regurgitation). Concomitant procedures were performed in 130 patients. Clinical and echocardiographic follow-up visits were obtained annually (mean follow up 3.9±2.7 years, 1324 patient-years; completeness of follow-up 99.4%). The in-hospital mortality rate was 0.6% (n =2), and the late mortality was 1.7% (n=6), with 5 noncardiac deaths (4 cancer, 1 multiorgan failure after noncardiac surgery) and 1 cardiac death (sudden death). At last follow-up, 94% of the surviving patients were in New York Heart Association class I. Ross procedure–related valvular reoperations were necessary in 9 patients: Three received autograft explants, 5 received homograft explants, and 1 received a combined auto- and homograft explant. At last follow-up visit, autograft/homograft regurgitation grade II was present in 5/10 patients and grade III in 4/0. Maximum/mean pressure gradients were 7.4±6.2/3.7±2.1 mm Hg across the autograft and 15.3±9.4/7.6±5.0 mm Hg across the right ventricular outflow tract, respectively. Aortic root dilatation was not observed. Freedom from any valve-related intervention was 95% at 8 years (95% confidence interval 91% to 99%).

Conclusion— Midterm follow-up of autograft procedures according to the original Ross subcoronary approach proves excellent clinical and hemodynamic results, with no considerable reoperation rates. Revival of the original subcoronary Ross operation should be taken into account when considering the best way to install the Ross principle.