Root replacement for all allograft aortic valves: preferred technique or too radical?

Allografts for aortic valve and root replacement: veni vidi vici?

Allografts were introduced in the early 1960s for the replacement of the aortic valve and regarded at the time as a close-to-perfect valve substitute. However, over the past 40 years it has become evident that not all of the high expectations could be met. This review summarizes the past 40 years of clinical experience with allografts for aortic valve replacement, describes the advantages and disadvantages of allografts compared with other aortic valve substitutes and their impact on patient prognosis, and discusses the future role of allografts for the replacement of the aortic valve or root.

Thoracic aortic aneurysm syndrome in children

In contrast with adults, thoracic aortic aneurysms in children are usually associated with connective tissue defect syndromes. As such, there are phenotypic clues to identify patients at risk. Marfan syndrome, Loeys-Dietz syndrome, and bicuspid aortic valve syndrome account for the majority of these aneurysms. Indications for surgery as well as surgical options differ according to diagnosis and are reviewed herein.

Autografts, homografts, and xenografts: overview on stentless aortic valve surgery

Stentless valves, either human (autografts, homografts) or animal (porcine xenografts), were historically among the first substitutes to be used to replace the diseased aortic valve. Forty years after those pioneering days and 15 years after revival of such valves, stentless grafts have become a mainstay in aortic surgery. Although limitations associated with the use of autografts, homografts and xenografts remain, stentless valves have profoundly improved quality of life after aortic valve/root replacement. In addition, stentless surgery has greatly advanced the understanding of aortic root anatomy, physiology and pathology among surgeons.

Homograft Implantation Techniques in the Aortic Position: To Preserve or Replace the Aortic Root?

BACKGROUND

One determinant of durability of the homograft in the aortic position is the implantation technique. This study uses meta-analytical techniques to evaluate the differences in early and long-term outcomes of patients undergoing aortic homograft implantation with either a root replacement or a root preserving technique.

METHODS

A systematic review of the literature (1965-2005) reporting results after homograft implantation in the aortic position with emphasis in the implantation technique was performed. Random and fixed-effects models were used. Cumulative and influential meta-analysis, graphic exploration, and sensitivity analysis were carried out to explain the heterogeneity between studies and to investigate potential publication bias.

RESULTS

Eleven studies were included. None of the studies was randomized. There was no significant difference in early mortality between root replacement and root preserving groups (odds ratio = 2.57 with 95% confidence interval [CI] 0.68-9.72 in random-effects model) and the root replacement group had a significantly lower rate of reoperation during long-term follow-up (hazard ratio = 0.55 with 95% CI 0.38-0.80 in random-effects model). Subgroup analysis focusing on patients having the subcoronary technique for homograft implantation showed similar results. Significant heterogeneity between studies can be detected. No publication bias was found.

CONCLUSIONS

There was no significant difference in early mortality between root replacement and root preserving groups. However, the root replacement technique group had a significantly lower rate of reoperation during long-term follow-up. Excluding outliers identified in a funnel plot reduced the heterogeneity and reached a similar conclusion.

Valve-Related Events After Aortic Root Replacement With Cryopreserved Aortic Homografts

BACKGROUND

Aortic root replacement with aortic homografts for various pathologic conditions involving the aortic root has yielded good early results. To assess mid-term valve-related events, a follow-up study was conducted.

METHODS

From February 1989 through January 2003, 213 patients with a mean age of 51.3 +/- 11.8 years underwent aortic root replacement with a cryopreserved aortic homograft. Bacterial endocarditis (58.7%) was the predominant indication for surgery (native valve endocarditis, n = 73; prosthetic valve endocarditis, n = 52). Of the 197 hospital survivors, 194 were entered in the follow-up study (98.5% complete). Endpoints of the study were death, valve-related death, reoperation for valve failure, endocarditis, thromboembolic events, and anticoagulant-related bleeding events. Follow-up was conducted between February and April 2003.

RESULTS

Overall hospital mortality was 7.5% (n = 16; 70% confidence limits, 5.6% to 9.4%). Mean follow-up was 5.8 years (range, 0.3 to 14.3). In total, 20 late deaths occurred (10.3%); of these, 5 were valve-related. The overall survival at 5 and 10 years is 87.3% +/- 2.4% and 70.8% +/- 5.3%, respectively. Twenty-one patients (10.8%) required reoperation, either for structural valve deterioration (n = 12), false aneurysm (n = 3), endocarditis of the homograft (n = 3), or for other reason (n = 3). Mortality for reoperation was 28.6% (n = 6). Five-year and 10-year freedom from reoperation is 94.5% +/- 1.8% and 76.4% +/- 5.3%, respectively. Endocarditis of the homograft was reported in 4 patients (3.2%), of whom 1 patient was treated medically and 3 required reoperation. Thromboembolic events (n = 1) and anticoagulant-related bleeding events (n = 0) were rarely seen. A recent echocardiographic study was available in 124 patients (71.3%). Aortic regurgitation grade I to II was reported in 121 patients (97.6%).

CONCLUSIONS

Cryopreserved aortic homografts function well on mid-term evaluation. The incidence of structural valve failure is acceptable. Reoperations for homograft endocarditis carry a high mortality rate.

Prognosis after aortic root replacement with cryopreserved allografts in adults

BACKGROUND

Aortic root replacement with cryopreserved allografts is associated with excellent hemodynamics, little endocarditis, low thromboembolic event rates, and no need for anticoagulation. There is, however, concern regarding the long-term durability of this valve substitute, especially in younger patients. Meta-analysis and microsimulation were used to calculate age-specific long-term prognosis after allograft aortic root replacement based on current evidence.

METHODS

Our center's experience with cryopreserved allograft aortic root replacement in 165 adult patients was combined in a meta-analysis with reported and individual results from four other hospitals. Using this information, the microsimulation model predicted age- and gender-specific total and reoperation-free and event-free life expectancy.

RESULTS

The pooled results comprised 629 patients with a total follow-up of 1860 patient-years (range 0 to 12.8 years). Annual risks were 0.6% for thromboembolism, 0.05% for bleeding, 0.5% for endocarditis, and 0.5% for nonstructural valve failure. Structural allograft failure requiring reoperation occurred in 15 patients, and a patient age-specific Weibull function was constructed accordingly. Calculated total life expectancy varied from 27 years in a 25-year-old to 12 years in a 65-year-old male; corresponding actual lifetime risk of reoperation was 89% and 35%, respectively.

CONCLUSIONS

Cryopreserved aortic allografts have an age-related limited durability. This results in a considerable lifetime risk of reoperation, especially in young patients. The combination of meta-analysis and microsimulation provides an appropriate tool for estimating individualized long-term outcome after aortic valve replacement and can be useful both for patient counseling and prognostic research purposes.

Update on indications for surgery in aortic insufficiency

Aortic insufficiency is a valvular disease characterized by left ventricular volume overload. This article presents a logical approach for following up patients with aortic insufficiency and helps to determine the optimal timing for valve replacement. The various valve replacement techniques are discussed, and the specific benefits or risks associated with these procedures are described.

Technical evolution of the Ross operation: midterm results in 186 patients

BACKGROUND

The Ross operation approaches the ideal aortic valve replacement. Between February 1995 and February 2000 we performed 186 procedures. This article reviews modifications introduced reflecting our experience.

METHODS

In all patients the Ross operation was performed as root replacement. Echocardiographic follow-up was complete in 94% of patients.

RESULTS

No operative death or early mortality occurred, nor did thromboembolic or hemorrhagic events. One patient died at 25 months from hemoptysis with pulmonary valve vegetations. Three patients required reoperation for autograft insufficiency. In 1 patient a tethered cusp was repairable and in 2 patients progressive autograft dilatation required autograft replacement. After routinely incorporating support into the aortic annulus and replacing all dilated ascending aorta, autograft dilatation did not recur. For the pulmonary homograft, one outflow patch was placed to relieve a symptomatic gradient. Nine patients with elevated gradients were under observation. Echocardiography revealed autograft median peak systolic gradients of 4.6+/-2.8 mm Hg, pulmonary homograft gradients of 14.8+/-9.6 mm Hg, and nil or insignificant regurgitation.

CONCLUSIONS

The aortic annulus must be supported and the dilated ascending aorta replaced. Root replacement with a short autograft allows consistent results. Pulmonary homograft dysfunction is rare but unpredictable.

Cryopreserved aortic allografts for aortic root reconstruction: a single institution's experience

BACKGROUND

An evaluation of early and long-term results of aortic root replacement with cryopreserved aortic allografts and echocardiographic follow-up of allograft valve function was performed.

METHODS

From September 1989 through May 1998, 132 patients aged 17 to 77 years (mean, 50.8 +/- 14.8 years) underwent freestanding aortic root replacement with a cryopreserved aortic allograft. Eighty-six (65.1%) patients had New York Heart Association class III or IV functional status before operation, and 27 (20.5%) patients underwent emergency operation. Fifty-nine (44.7%) patients had undergone previous cardiac operations. The cause of aortic disease was acute endocarditis in 63 (47.7%) patients, healed endocarditis in 15 (11.3%), degenerative in 20 (15.2%), congenital in 20 (15.2%), failed prosthesis in 10 (7.6%) and rheumatic in 4 (3.0%). Follow-up was complete, with a mean of 42 months.

RESULTS

There were 12 hospital deaths (9.1%; 70% confidence limits [CL], 6.6% and 11.6%); 9 of them were operated on for active endocarditis (p = 0.062). Multivariate analysis determined age older than 65 years (p = 0.012) and emergency operation (p = 0.009) as independent risk factors for hospital mortality. During follow-up, 6 (5.0%; 70% CL, 3.0% and 7.0%) patients died. Cumulative survival rate for the entire group was 81.8% +/- 5.4% at 8 years. Freedom from reoperation for structural valve failure was 100%, freedom from reoperation for any cause was 96.3% +/- 1.8% at 8 years. Freedom from endocarditis at 8 years was 97.9% +/- 1.4%. Follow-up of allograft valve function showed no or trivial aortic regurgitation in 97% of patients and absence of stenosis of the allograft in 100%.

CONCLUSIONS

Aortic root replacement with cryopreserved aortic allografts can be performed with acceptable hospital mortality and long-term results. The durability of cryopreserved aortic allografts is good, and reoperation for structural valve failure is absent at 8 years.

Aortic allografts and pulmonary autografts for replacement of the aortic valve and aortic root

BACKGROUND

Extensive experience has accumulated with the use of aortic and pulmonary autografts for replacement of the aortic valve and the aortic root. Three general techniques for insertion have been used: subcoronary (free-hand) valve implantation, mini- or inclusion-root implantation, and aortic root replacement. Thirty-day mortality for elective operations with all of these techniques has not exceeded 5%. Thromboembolic episodes have been rare, and endocarditis has occurred infrequently. Early hemodynamic performance has been excellent, without significant gradients or valve regurgitation in the majority of patients.

METHODS AND RESULTS

Progressive aortic regurgitation has been observed with continued follow-up, and is the most important complication of both types of valves. Leaflet failure and technical problems are the major causes of reoperation for patients receiving aortic allografts. There is some evidence to suggest that the prevalence of these complications is lower with the root replacement technique than with the intraaortic implantation methods.

CONCLUSIONS

Reoperation for regurgitation of the neoaortic valve is the major complication of the pulmonary autograft procedure. The incidence of reoperation appears to be lowest with the root replacement technique. Certain conditions (acute rheumatic fever, juvenile rheumatoid arthritis, systemic lupus, ankylosing spondylitis, Libman-Sachs endocarditis, and possibly a dilated aortic root) may be contraindications to the use of a pulmonary autograft. Reoperation on the pulmonary allograft that is used to replace the autograft may be necessary in up to 20% of patients at 20 years.

Allograft heart valve viability and valve-processing variables

BACKGROUND

The impact of allograft valve viability on valve durability remains controversial. Analyses of our clinical results have demonstrated the superiority of the cryopreserved valve viable at the time of implantation over the 4 degrees C stored valve nonviable at the time of implantation. In this study, we quantitatively assessed the effects on viability of current and past valve-processing protocols at The Prince Charles Hospital.

METHODS

The viability of pulmonary valves was quantitatively analyzed by thin-layer autoradiography to assess the effects of donor type, antibiotics, and valve storage.

RESULTS

Control valve segments obtained from beating-heart donor valves had a higher initial viability (0.92+/-0.02) than nonbeating-heart donor valves (0.66+/-0.03). Cryopreservation after low-dose antibiotic sterilization significantly reduced viability to 50% to 60% of the control, and in the presence of amphotericin B, viability dropped further to 10% to 36% of the control. After 7 days' storage at 4 degrees C, viability was reduced to 2% of control and to 0% viability after 21 days.

CONCLUSIONS

For maximal preimplantation viability, valves should be procured as soon as possible after cessation of heart beat and should be cryopreserved if they are not to be clinically implanted within 1 to 2 days. Amphotericin B should not be used in conjunction with cryopreservation if viability is to be maximized.

Aortic valve replacement with biological substitute

In the quest for an ideal aortic valve substitute, homografts and autografts are well-established options. We reviewed our results with homografts and autografts for aortic valve replacement during the last 5 years. From March 1992 through July 1997, 189 patients (138 male and 51 female), age 8 months to 68 years (mean 31.0+/-4.2 years), underwent aortic valve replacement with a human biological substitute. Of these, 93 patients received a cryopreserved or antibiotic-preserved aortic/pulmonary homograft, whereas 96 patients underwent a Ross procedure. Etiology was rheumatic in 143 (75.6%) patients, bicuspid aortic valve in 40 (21.2%), Marfan's disease in 5 (2.6%), and myxomatous aortitis in 1 (0.5%). Among the homograft group, a scalloped subcoronary implantation technique was used in 54 patients, whereas 32 patients underwent root replacement. Five patients required aortic root and ascending aortia replacement for annuloaortic ectasia. In all patients undergoing the Ross procedure, a root replacement technique was used. Operative mortality was 7.4% (14 patients). Late mortality was 5.3% (10 patients). Follow-up ranged from 1 to 46 months postoperatively. In patients with homograft aortic valve replacement, 76 patients (91.5%) had trivial to mild aortic regurgitation, while 7 patients (8.4%) had important aortic regurgitation. In patients with the Ross procedure, 78 patients (89.6%) had trivial to mild regurgitation. Moderate to severe aortic regurgitation was present in 9 patients (10.3%), all of whom had rheumatic heart disease and were young (< 30 years at surgery). We conclude that homografts and autografts provide an excellent substitute for the diseased aortic valve. Young age (< 30 years) with rheumatic etiology is a major risk factor for early progressive aortic regurgitation in patients undergoing the Ross procedure.

Comparison of techniques for implantation of aortic valve allografts

BACKGROUND

Various implantation techniques for allograft aortic valve replacement have evolved over the years. Our objective was to examine the effects of different implantation methods on subsequent valve performance and durability.

METHODS

Between May 1985 and January 1994, 137 patients underwent allograft aortic valve replacement. The first 59 aortic valve allografts were inserted by the freehand scalloped technique with removal of the aortic sinuses, and the last 78 valves were inserted by the cylinder technique, in which the aortic sinuses and sinotubular junction were retained. The mean age of the 91 men and 46 women was 53.7 years (range, 18 to 83 years). Preoperative diagnoses were aortic stenosis (n = 57), aortic regurgitation (AR, n = 40) and aortic stenosis/AR (n = 40); 27 patients had prior aortic valve operations and 1 patient had a previous heart transplantation. Active endocarditis was present in 29 patients. Associated procedures included coronary artery bypass (n = 33), ascending aneurysm repair (n = 4), left ventricular aneurysmectomy (n = 3), repair of atrial septal defect (n = 2), mitral valve repair or replacement (n = 6), and aortic root enlargement (n = 24). Follow-up was complete in 133 patients (97%) a mean of 4.9 years (range, 1 day to 9.8 years) after allograft aortic valve replacement.

RESULTS

Operative mortality was 6.5% for all patients but only 1.9% for patients without infection having isolated aortic valve replacement. Early echocardiography (mean of 8.4 days postoperatively) demonstrated no AR or mild AR and a mean gradient of 10.6 +/- 6.2 mm Hg in all patients. The cumulative risk of development of grade III or IV AR at 7 years postoperatively was 26.2% +/- 6.3% in the scallop group and 12.4% +/- 5.6% in the cylinder group (p = 0.4). Late postoperatively, transvalvular gradient by echocardiography was 13.1 +/- 9.4 mm Hg, and was similar in the two study groups. Late AR led to reoperation in 13 patients (22%) who had initial implantation with the scallop method and only 4 patients (5.4%) who had the valve inserted with the cylinder method. However, because duration of follow-up was longer for patients in the scallop group, cumulative risk of reoperation was similar at 5 years postoperatively (scallop, 13.7% [95% confidence interval, 76.7% to 95.8%]; cylinder, 11.5% [95% confidence interval, 75.5% to 99.1%]).

CONCLUSIONS

The insertion of an aortic valve allograft as a cylinder, retaining the sinotubular junction, appears to result in less aortic regurgitation at 7 years postoperatively, and with additional follow-up may result in less reoperation for AR.

Allograft aortic valve replacement: long-term follow-up

Aortic valve replacement using an allograft aortic valve has been performed on 804 patients. From December 1969 to May 1975, 124 patients received a nonviable allograft valve sterilized by incubation with low-dose antibiotics and stored for weeks by refrigeration at 4 degrees C (series 1). From June 1975 to January 1994, 680 patients received viable allograft valves, now cryopreserved early within 2 hours of collection from transplant recipient donors, 6 hours for multiorgan donor valves and 23 hours (mean) for autopsy valves from donor death. The 30-day mortality was 8.9% +/- 5% (95% confidence limits) for series I and 2.8% +/- 1% (95% confidence limits) for series II. Actuarial patient survival including hospital mortality at 15 years was 56% +/- 5% for series I and 62% +/- 5% for series II. The probability of a thromboembolic event was low, freedom at 15 years being 95% +/- 1% for patients receiving allografts with or without associated coronary bypass procedures and 81% +/- 5% for patients having allografts with other associated procedures (eg, mitral valve operations). Actuarial freedom from endocarditis was similar for the two series, 91% +/- 3% (series I) and 94% +/- 2% (series II) at 15 years. The freedom from valve incompetence, from reoperation for all causes, and from structural deterioration demonstrated clearly the inferiority of the 4 degrees C stored allograft valves. For structural deterioration as identified clinically, at reoperation and at death, freedom from this event at 15 years was 45% +/- 6% for series I and 80% +/- 5% for series II (p value for the difference is 0).(ABSTRACT TRUNCATED AT 250 WORDS)

Allograft aortic root replacement: standardization and simplification of technique

A variety of surgical techniques for implantation of an allograft aortic valve have been described. Compounding this confusion, the host pathologic processes necessitating aortic valve or root replacement are many, often associated with asymmetry of the aortic root and valve annulus. These complexities can now be negated by routinely performing allograft aortic root replacement with pedicle coronary artery reimplantation in all situations. This procedure is described in a simple step-by-step manner that makes it amenable to all cardiac surgeons independent of experience.