Ross' first homograft replacement of the aortic valve

Milestone Operations in Heart Valve and Aortic Replacement: Anniversaries Worth Remembering

Seventy years ago, in 1952, Charles A. Hufnagel implanted a caged-ball prosthesis into the descending thoracic aorta, to treat a patient with aortic valve insufficiency. In 1962, 60 years ago, the first aortic homograft was implanted in a subcoronary position by Donald N. Ross and Brian G. Barratt-Boyes. Forty years ago, in 1982, the first anticalcification treatment was introduced in commercially manufactured porcine bioprostheses. All such important or even milestone events should be remembered, since they witness efforts made by those who have significantly influenced the clinical history of aortic and valvular diseases.

Heart valve disease: a journey of discovery

In the centenary year of the British Cardiovascular Society (BCS), this review article outlines the influence of UK cardiologists and surgeons on the field of heart valve disease, many of whom can rightly claim 'world firsts' in the field. From the description of endocarditis as we know it today at the turn of the 20th century, to the first mitral valvotomy, heart valve replacement and invention of the Ross procedure. These advances have transformed the outlook of patients with symptomatic valve disease from palliation and certain death to curative treatment and near normal life expectancy. Transcatheter aortic valve implantation (TAVI) was adopted early in the UK, and thanks to the comprehensive national database, the UK TAVI registry is one of the world's largest, contributing real-world patient data to inform clinical practice. The more recent concepts of 'Heart Valve Centres of Excellence' and specialist valve clinics have been developed by the BCS-affiliated British Heart Valve Society which continues to drive improved standards for patients with heart valve disease. The next 100 years will no doubt be equally thrilling in terms of innovation for heart valve disease, with artificial intelligence, transcatheter therapies and cutting-edge technology continuing to improve patient care and clinical outcomes.

Immune Privilege of Heart Valves

Immune privilege is an evolutionary adaptation that protects vital tissues with limited regenerative capacity from collateral damage by the immune response. Classical examples include the anterior chamber of the eye and the brain. More recently, the placenta, testes and articular cartilage were found to have similar immune privilege. What all of these tissues have in common is their vital function for evolutionary fitness and a limited regenerative capacity. Immune privilege is clinically relevant, because corneal transplantation and meniscal transplantation do not require immunosuppression. The heart valves also serve a vital function and have limited regenerative capacity after damage. Moreover, experimental and clinical evidence from heart valve transplantation suggests that the heart valves are spared from alloimmune injury. Here we review this evidence and propose the concept of heart valves as immune privileged sites. This concept has important clinical implications for heart valve transplantation.

Tissue-type plasminogen activator gene targets thrombolysis in atriums

Our previous investigations showed that retroviral gene transfer of tissue-type plasminogen activator (tPA) effectively targeted thrombolysis in vitro and in the model of inferior caval veins of rabbits. This study is to identify the target thrombolysis of retroviral vector recombinant pLEGFP-N1-tPA transferred into the tissue around the Dacron patch (the same materials making of the ring of mechanical valve) in left atriums of rabbits. 70 Dacron patches were transplanted into the left atriums of 70 New Zealand white rabbits. The rabbits were randomly divided into three groups according to the different handling methods, including local pLEGFP-N1-tPA transferred group (gene therapy group, 30 animals), pLEGFP-N1 transferred group (control group, 20 animals), medium DMEM + 10% neonate calf serum (NCS) injected group (blank control group, 20 animals). Samples of blood, Dacron pieces and left atriums (auricles) wall from half of above in each group were harvested on second day and another half were harvested on 75th day after surgery. The EGFP expression of harvested left atriums (auricles) wall were observed under the confocal. The thrombi on the surface of Dacron patches were detected by stereoscope and electron microscope. The tPA expression in left atriums (auricles) wall and in blood from left atriums were detected by Western blot and their thrombolysis and activities were observed and calculated in plasma plates. ELISA were used to identify the contents of tPA. No thrombus was seen on the surface of Dacron patches that were transplanted in left atriums by tPA locally transferring around them. Activity and content of tPA were high in local tissue of left atrium and in blood of left atrium. It demonstrated effectively thrombolysis by tPA rapidly, efficiently and long expressing. This puts the foundation of mechanical valve replacement model for tPA gene valve, next.

Systolic aortic valve compression from partial dehiscence of an aortic valve homograft

Implantation of valve prostheses provide improvement of symptoms and prolongation of life in selected patients with valvular heart disease. Meticulous follow-up of patients after valve surgery is essential as complications of valve failure, valve dehiscence, valve thrombosis, and infection may occur. The major mode of failure of aortic valve homografts is valve regurgitation, which is readily detected by physical examination. We report a case of left ventricular outflow obstruction after implantation of an aortic valve homograft.

Ventricular outflow tract reconstructions with cryopreserved cardiac valve homografts. A single surgeon's 10-year experience

OBJECTIVE

From January 1, 1985 through December 31, 1994, one surgeon implanted cryopreserved valved homografts into 149 patients--65 since December 1988. This latter series (II) was accomplished in a single hospital, facilitating patient follow-up with biannual echocardiograms. Analysis of these 65 patients is the primary focus of this report; the indications and early surgical results for the two parts of the series (I and II) are compared to assess the evolution of a single surgeon's use of homografts in a mixed pediatric and adult practice.

METHODS

Fifty-one variables for each patient (series II) were entered into a computerized database and analyzed (multivariate and univariate) using SPSS 6.1 software (Statistical Products and Service Solutions, Chicago, IL). Cox proportional hazard model was used to identify the independent contribution of each variable for patient mortality and homograft failure. Cumulative survival estimates were made using Kaplan-Meier analysis. Homograft failure was defined as requirement for replacement or death. In series I, there were 41 left ventricular outflow tract (LVOT) reconstructions (31 adult) and 43 right ventricular outflow tract (RVOT) reconstructions (42 pediatric). In series II, there were 55 RVOT reconstructions (52 pediatric) and 10 LVOT reconstructions (7 adult).

RESULTS

There were no technical surgical failures. Total surgical mortality rate was 6% (5/84) in series I (3 LVOT, 2 RVOT) and 15% (10/65) in series II (2 LVOT, 8 RVOT) (I vs. II NS; p = 0.11, two-tailed Fisher exact test). By the Cox analysis, only age < 2 years (p < 0.03) and cross-clamp time > 120 minutes (p < 0.05) were significant predictors for death. Age-based survival curves were compared in a sequential bivariate analyses (log rank test) and age < 2 years again was a significant predictor of decreased patient survival (p < 0.006). Actuarial freedom from patient death or reoperation for homograft failure was 82% +/- 7% at 1000 days and 77% +/- 10% at 2000 days. Three patients required re-replacement for homograft failure (5.4%); one of these patients died. The only significant predictor of homograft failure was postoperative endocarditis (p < 0.05). Homograft performance was evaluated by an extensive echocardiography protocol: in surviving patients and homografts, three valved conduits were judged to have severely impaired performance (stenosis or regurgitation), awaiting surgical replacement for a putative total homograft-related structural failures rate of 11% at 5 1/2 years.

CONCLUSIONS

Comparisons of series I and II shows, in one surgeon's practice, an evolution away from use of cryopreserved homografts for LVOT reconstructions except when needed for destructive bacterial endocarditis or complex congenital anatomy. Homograft efficacy and durability were similar in RVOT and LVOT positions, with 78.5% of patients surviving at 5 1/2 years; in surviving patients, 89% of homografts have continued to function well. Homografts are not immune to prosthetic bacterial endocarditis, and its occurrence is associated with accelerated deterioration. Cryopreserved homograft valves are an imperfect but satisfactory biological material for specific ventricular outflow reconstructions.

Pulmonary autograft. An aortic valve replacement alternative

In selected patients, the pulmonary autograft procedure utilizing cryopreserved homografts for reconstruction of the right ventricular outflow tract is becoming an increasingly popular aortic valve replacement alternative. Longitudinal statistical reports show that patients need reoperation less often with this procedure. Because the valve is autogenous tissue, all indications to date show that the valve continues to function for extended periods of time in all patients and can accommodate growth in children. At the same time, transfer of the pulmonary valve to the aortic position provides a natural valvular flow pattern and freedom from the degenerative changes associated with bioprosthetic valves or the need for anticoagulation associated with mechanical valves.

High energy phosphate depletion in leaflet matrix cells during processing of cryopreserved cardiac valves

Preimplantation preparation of cardiac valves includes three major steps: (1) harvesting with accompanying ischemia (warm time from cessation of donor heart beat), (2) antibiotic disinfection, and (3) controlled-rate cryopreservation. To define the interdependent injury effects of these manipulations on leaflet matrix cells and specifically the potential for prolonged harvest-related ischemia to predispose greater injury by the subsequent steps, 96 semilunar valves were harvested from pigs in a manner analogous to human heart valve retrievals and randomly allocated to study groups as follows: 48 control valves were exposed to increasing harvested-related ischemic times, (2, 6, 12, 24 hr) and immersed in liquid nitrogen to arrest metabolic activity (i.e., prior to cryopreservation) and conclude the ischemia; another 48 were similarly harvested, subjected to identical ischemic times, then disinfected in 4 degrees C RPMI medium with standard antibiotics for 24 hr and dimethylsulfoxide cryopreserved at -1 degrees C/min to -170 degrees C (i.e., formal cryopreservation protocol). At thawing, each valve was extracted in 12% trichloroacetic acid and assayed by high performance liquid chromatography for components of the adenine nucleotide pool including ATP, lower energy nucleotides (total adenine nucleotides, [TAN] = [ATP] + [ADP] + [AMP]), adenosine, and the diffusible purines. Results are reported as nanomoles metabolite/milligram of leaflet cell protein (Lowry) and reflect a maintenance of total high energy phosphates in the control groups (5.41 +/- 0.29 nmole TAN at 2 hr; 8.34 +/- 0.67 nmole TAN at 24 hr), which fell significantly in all cryopreserved groups (1.27 +/- 0.33 nmole TAN at 2 hr; 0.34 +/- 0.22 nmole TAN at 24 hr).(ABSTRACT TRUNCATED AT 250 WORDS)