Ross procedure

Controversy over prosthetic type for aortic valve replacement (AVR) has dropped dramatically in the past 15 years because of the growth in popularity and excellent results obtained with the Ross procedure ( Fig. 1 A and B ). Pulmonary autograft (PA) has become the first choice of AVR in children and adolescents in some institutes . PA shows excellent haemodynamic performance, superior longevity ( Fig. 2 ) , freedom from anticoagulation and haemolysis and decreased susceptibility to endocarditis. PA is also known to have the potential for growth. However, the Ross procedure is a technically demanding procedure and reoperation for bleeding and postoperative conduction abnormality is not as rare as early complications. Freedom from autograft dysfunction, including severe autograft insufficiency, ranges from 75% to 100% depending upon the duration of follow-up . Elkins et al. reported freedom from autograft replacement of 93% and freedom from severe autograft insufficiency or valve-related death of 90% at their 12-year follow-up. Autograft insufficiency is one of the leading causes of reoperation with the Ross procedure and several factors are implicated as risk factors, such as preoperative diagnosis of aortic insufficiency, presence of dilated aortic annulus, bicuspid aortic valve, rheumatic heart disease, technical imprecision, the type of insertion and inherent disease of the pulmonary valve. Elkins et al. reported a freedom from right ventricular outflow tract (RVOT) homograft replacement of 90% at 12 years for children. Rates of freedom from RVOT were also similar for other authors . Because of the diminishing availability of homografts, several conduits are used to reconstruct RVOT; however, their durability seems to be worse than that of homografts . Finally, Elkins et al. reported freedom from all valve-related morbidity of 79% at 11 years.

Ross intervention. After harvesting the pulmonary autograft and left and right coronary arteries (A), the left ventricular outflow tract is reconstructed with the pulmonary autograft and reimplantation of the coronary arteries, and the right ventricular outflow tract is reconstructed with a pulmonary homograft (B). By courtesy of Hodder Education, London.

Freedom from reoperation after initial aortic valve replacement (AVR) stratified by prosthetic type. A multivariable equation was constructed for remaining alive after initial AVR without subsequent valve replacement according to the original competing-risk model and forcing all valve types into the equation. The resulting model was then solved for a hypothetical 10-year-old patient of 40 kg undergoing operation in 1990. The autograft has superior longevity, whereas the tissue valves and allografts have considerably worse durability. The numbers in parentheses represent the total number of AVR episodes for each prosthesis type .

Husain et al. reported that freedom from replacement of the PA was 96% at 10 years. Freedom from replacement of the pulmonary homograft (PH) was 96% at 10 years.

Technical modifications, such as resection and graft replacement of a dilated ascending aorta, annular reinforcement with circumferential felt or Dacron and/or reinforcement of the entire autograft root, are all options to minimize autograft dilation and insufficiency.

In neonates and infants with left ventricular outflow tract (LVOT) obstruction, the Ross procedure, although more complex, provides excellent normalization of haemodynamics and regression of left ventricular hypertrophy by avoiding residual lesions . Despite the need for reoperation and potential for autograft root dilation, the Ross and Ross-Konno procedures remain the best choice for AVR in infants with multilevel LVOT obstruction or severe aortic insufficiency following valvuloplasty .

Mechanical aortic valve replacement

MVs are reserved for children who have connective tissue disorders or whose native pulmonary valves are unsuitable for translocation to the aortic position. AVR using mechanical prosthetic valves in children often requires annular enlargement to insert commercially available prostheses . The Yamaguchi , Manouguian and Konno procedures enable insertion of prostheses two sizes bigger than that of in situ insertion. The Konno procedure requires incision of the ventricular septum, which might cause ventricular dysfunction or conduction abnormality. In the Manouguian procedure, the incision is extended to the anterior mitral leaflet and might cause mitral insufficiency. The Yamaguchi procedure does not damage either the ventricular septum or the mitral leaflet.

Shanmugam et al. reported that no rereplacement of prosthesis was required when the patient received a prosthesis 21 mm or larger in size. Masuda et al. reported that freedom from rereplacement of aortic valve was 94% at 15 years and was at least compatible with the results of other series with mechanical prostheses by Shanmugam et al. (92% at 20 years) and Ruzmetov et al. (84% at 19 years) , and was not inferior to the results of PA reported by Elkins et al. (93% at 12 years) and Pasquali et al. (81% at 8 years) . An actuarial survival rate of 92% and a freedom from valve-related complications rate of 86% at 15 years seem quite acceptable . Regression of left ventricular dilatation in children with severe aortic regurgitation can be observed on echocardiography and magnetic resonance imaging after timely AVR .

Concerning anticoagulation problems, Akhtar et al. reported a study assessing long-term survival and anticoagulant-related complications after mechanical VR in adolescents with rheumatic heart disease. Patient survival rates at 30 days, 3 months and 1, 5 and 10 years were 95.5%, 93.2%, 87.5%, 82.9% and 82.9%, respectively. MV thrombosis occurred in 4.5% patients and was fatal in 3.4% of them. Severe haemorrhage required hospital admission in 4.5% of patients.

Although quite durable, MVs require chronic anticoagulation, which can be poorly tolerated and quite difficult to control in some children. Patient growth and acquired patient-prosthesis mismatch are not uncommon problems with mechanical AVR.

Bioprostheses, homografts and xenografts

Bioprostheses, homografts and xenografts in children and adolescents have been largely abandoned due to accelerated degeneration ( Fig. 3 ) . In the younger age group, there is a significant risk of structural valve deterioration, reported to range from 71% to 87% at 10 years .

Kaplan-Meier graph depicting freedom from all valve-related reoperations after homograft or autograft replacement of the aortic valve. Means ± 67% confidence limits for three time intervals are indicated .

Decellularized aortic valve allografts appeared to be more resistant to calcification and did not show any major structural and morphological alteration. If these results are confirmed with longer follow-up periods, this technique may be a promising alternative to AVR for a selected group of patients, especially females .

Mortality

Karamlou et al. identified that younger age and lower weight at initial AVR unfavourably influenced mortality without repeated replacement, especially in the extreme cases of very young age or very low weight. Previously published reports, which showed that neonates and those aged less than 6 months compose the highest-risk group, agree with these findings . There are several reasons for poor outcome in this population. First, young age at initial operation was significantly associated with the presence of other cardiac anomalies, including important mitral valve dysfunction, which accounted for substantial mortality. Others have noted that those with concomitant cardiac lesions fare worse than those with isolated aortic valve disease . Second, the preoperative clinical status of younger patients, especially neonates, is likely to be considerably worse than those undergoing later AVR. Correlation between poor preoperative left ventricular function (fractional shortening < 25%) and late mortality has been established. Finally, younger patients (and those with lower weight) are at highest risk of prosthesis outgrowth necessitating subsequent repeated replacement or intervention, which may contribute to increased mortality. The need for concomitant aortic arch reconstruction or augmentation was also identified as an incremental risk factor for death without a second AVR.

In a recent study, Alsoufi et al. reported on 346 children who underwent AVR (215 Ross procedures; 131 placements of a mechanical prosthesis). Patients undergoing the Ross procedure were younger, more likely to have a congenital cause and less likely to have a rheumatic or connective tissue cause; they had a lower frequency of regurgitation, required more annular enlargement and had less concomitant cardiac surgery. Competing-risk analysis showed that 16 years after AVR, 20% of patients had died without subsequent AVR, 25% had undergone a second AVR and 55% remained alive without further replacement. Factors associated with early-phase death included MV and a non-rheumatic cause. MVs were also associated with constant-phase mortality. Repeated AVR was associated with the Ross procedure and a rheumatic cause. In children who received a mechanical prosthesis, younger age and smaller valve size were significant risk factors for death. Freedom from homograft replacement after the Ross procedure was 82% at 16 years of follow-up. Results from this study showed good outcomes and an acceptable complication rate with both valve choices. Given the significantly increased risk of early and late death in younger children receiving smaller MVs, the Ross procedure confers a survival advantage in this age group at the expense of increased reoperation risk, especially in patients with a rheumatic cause.