Gary K. Lofland

Decellularization reduces calcification while improving both durability and 1-year functional results of pulmonary homograft valves in juvenile sheep

OBJECTIVE The juvenile sheep functional valve chronic implant calcification model was used to compare long-term calcification rates, functional performance, and durability for 3 types of right ventricular outflow tract implants: classically cryopreserved homografts and 2 decellularized pulmonary valved conduits. METHODS Fifteen juvenile sheep were randomly assigned to one of 3 study arms and underwent pulmonary valve replacement. The arms included the following: (1) cryopreserved ovine pulmonary valves; (2) cryopreserved, decellularized, saline (1 degrees C-10 degrees C)-stored ovine pulmonary valves; and (3) cryopreserved, decellularized, glycerolized (-80 degrees C) stored ovine pulmonary valves. Animal growth, serial echocardiographic results (with valve performance assessment), dimensions, and tissue-specific calcification measurements were compared with pre-explant angiographic analysis and right ventricular outflow tract pressure measurements, cardiac magnetic resonance imaging, specimen radiographic analysis, gross explant pathology, and histopathology. Parametric and nonparametric statistical analysis were performed. RESULTS All but 2 study animals receiving implants thrived postoperatively, with similar growth rates, explant valve dimensions, ventricular functions, cardiac output, and indices during the study. As determined by means of echocardiographic analysis, 3 animals in arm 1 (and one in arm 2) had leaflet dysfunction. Valve regurgitation was recognized in 1 survivor each from both arms 1 and 2. Although 1 arm 1 animal died with calcified subacute bacterial endocarditis, and the other 4 had leaflet and conduit wall calcification by the time of death, no arm 2 or arm 3 animals demonstrated leaflet calcium, and no arm 3 and only 1 arm 2 animals had calcium in the conduit wall over the entire year, as determined with any measurement method. All cryopreserved conduit walls had calcium by 20 weeks, whereas only 1 of 10 decellularized conduits (arms 2 plus 3) had wall calcium. CONCLUSION Cryopreserved-decellularized-glycerolized valves retained normal valve function, with absent leaflet and minimal wall calcifications 1 year postoperatively, as opposed to classically cryopreserved allografts. These results might be predictive of the prolonged durability and functionality of a cryopreserved-decellularized-glycerolized allograft valve.

The enhancement of hemodynamic performance in Fontan circulation using pain free spontaneous ventilation.

OBJECTIVE Positive pressure ventilation is known to have a deleterious effect on pulmonary blood flow in patients with Fontan physiology. We evaluated the hemodynamic effects of pain free, spontaneous, non-positive pressure ventilation in patients undergoing Fontan staging procedures or completion. Fontan procedures, with creation of low pressure passive pulmonary circulation. METHODS Between May 1997 and May 1999 50 consecutive patients undergoing either bi-directional Glenn (BDG, n=23) or completion Fontan (n=27), were managed with early extubation. Anaesthetic management included continuous narcotics, caudal block, epidural block, or hyperbaric spinal. Post-operative management included low dose dopamine (3 mcg/kg per min), nitro-glycerine (0.3 mcg/kg per min) and nitroprusside (0.3 mcg/kg per min). Post-operative management was identical for all patients. Twelve patients were randomly selected to undergo continuous cardiac output and cardiac index (CI) determinations utilizing extra vascular Doppler probes placed on the ascending aorta, allowing for continuous aortic diameter and Doppler wave form velocity recordings. All patients were extubated either in the operating room or within one hour post-operatively. There were no deaths and no complications in the series. Mean length of stay (LOS) for BDG was 4.3+/-0.5 days. Mean LOS for Fontan patients was 11+/-4 days. RESULTS Mean pulmonary artery pressure (MPAP) fell from 19+/-3.464 pre-extubation to 14+/-3.271 immediately post-extubation, 13.2+/-2.261 6 h post-extubation, and 11.7+/-2.146 12 h post-extubation. All decreases in MPAP post-extubation were significant (P=<0.05). CI pre-extubation was 3.25+/-1.09, immediately post-extubation 5.05+/-1.297, 12 h post-extubation 6.225+/-1.19. All increases in CI post-extubation were significant (P=<0.05). CONCLUSION Resumption of pain free, spontaneous, non-positive pressure ventilation enhances hemodynamic performance in patients with Fontan circulation and clearly improves outcome.

Performance and Morphology of Decellularized Pulmonary Valves Implanted in Juvenile Sheep

BACKGROUND Because of cryopreserved heart valve-mediated immune responses, decellularized allograft valves are an attractive option in children and young adults. The objective of this study was to investigate the performance and morphologic features of decellularized pulmonary valves implanted in the right ventricular outflow tract of juvenile sheep. METHODS Right ventricular outflow tract reconstructions in juvenile sheep (160±9 days) using cryopreserved pulmonary allografts (n=6), porcine aortic root bioprostheses (n=4), or detergent/enzyme-decellularized pulmonary allografts (n=8) were performed. Valve performance (echocardiography) and morphologic features (gross, radiographic, and histologic examination) were evaluated 20 weeks after implantation. RESULTS Decellularization reduced DNA in valve cusps by 99.3%. Bioprosthetic valves had the largest peak and mean gradients versus decellularized valves (p=0.03; p<0.001) and cryopreserved valves (p=0.01; p=0.001), which were similar (p=0.45; p=0.40). Regurgitation was minimal and similar for all groups (p=0.16). No cusp calcification was observed in any valve type. Arterial wall calcification was present in cryopreserved and bioprosthetic grafts but not in decellularized valves. No autologous recellularization or inflammation occurred in bioprostheses, whereas cellularity progressively decreased in cryopreserved grafts. Autologous recellularization was present in decellularized arterial walls and variably extending into the cusps. CONCLUSIONS Cryopreserved and decellularized graft hemodynamic performance was comparable. Autologous recellularization of the decellularized pulmonary arterial wall was consistently observed, with variable cusp recellularization. As demonstrated in this study, decellularized allograft valves have the potential for autologous recellularization.

Effects of cryopreservation, decellularization and novel extracellular matrix conditioning on the quasi-static and time-dependent properties of the pulmonary valve leaflet

Decellularized allografts offer potential as heart valve substitutes and scaffolds for cell seeding. The effects of decellularization on the quasi-static and time-dependent mechanical behavior of the pulmonary valve leaflet under biaxial loading conditions have not previously been reported in the literature. In the current study, the stress-strain, relaxation and creep behaviors of the ovine pulmonary valve leaflet were investigated under planar-biaxial loading conditions to determine the effects of decellularization and a novel post-decellularization extracellular matrix (ECM) conditioning process. As expected, decellularization resulted in increased stretch along the loading axes. A reduction in relaxation was observed following decellularization. This was accompanied by a reduction in glycosaminoglycan (GAG) content. Based on previous implant studies, these changes may be of little functional consequence in the short term; however, the long term effects of decreased relaxation and GAG content remain unknown. Some restoration of relaxation was observed following ECM conditioning, especially in the circumferential specimen direction, which may help mitigate any detrimental effects due to decellularization. Regardless of processing, creep under biaxial loading was negligible.

The Nonfenestrated Extracardiac Fontan Procedure: A Cohort of 145 Patients

BACKGROUND There are limited data available on the outcomes of single-ventricle patients who have undergone a nonfenestrated extracardiac Fontan procedure. This study examined the clinical experience of a large cohort of patients from a single institution who received this procedure. METHODS A retrospective data set of 145 patients who underwent a nonfenestrated extracardiac Fontan procedure from July 1997 to September 2008 was reviewed. RESULTS The hospital survival was 94.5%. Takedown of the Fontan conduit was necessary in 4 patients (2.8%), and 3 of these 4 patients were also operative deaths. Although female sex (p = 0.048), cardiopulmonary bypass time (p = 0.002), and aortic cross-clamp time (p = 0.007) were found to be significant in the univariate analysis, only sex (p = 0.035; odds ratio, 3.869; 95% confidence limits, 1.097 to 13.644) and cardiopulmonary bypass time in minutes (p = 0.001; odds ratio, 1.023; 95% confidence limits, 1.009 to 1.037) were found to be significant in the multivariate analysis for hospital survival. The late survival was 95.6% (131 of 137 patients) with a mean follow-up of 3.3 years (range, 0.0 to 10.8 years). The freedom from Fontan failure was 92% at 1 year, 89% at 5 years, and 82% at 10 years. Stepwise logistic regression found cardiopulmonary bypass time (p = 0.003; odds ratio, 1.023; 95% confidence limits, 1.008 to 1.039) to be a significant risk factor for late survival. CONCLUSIONS The nonfenestrated extracardiac Fontan procedure can be successfully used in the palliation of single-ventricle patients.

Bioengineered human and allogeneic pulmonary valve conduits chronically implanted orthotopically in baboons: Hemodynamic performance and immunologic consequences

OBJECTIVE This study assesses in a baboon model the hemodynamics and human leukocyte antigen immunogenicity of chronically implanted bioengineered (decellularized with collagen conditioning treatments) human and baboon heart valve scaffolds. METHODS Fourteen baboons underwent pulmonary valve replacement, 8 with decellularized and conditioned (bioengineered) pulmonary valves derived from allogeneic (N = 3) or xenogeneic (human) (N = 5) hearts; for comparison, 6 baboons received clinically relevant reference cryopreserved or porcine valved conduits. Panel-reactive serum antibodies (human leukocyte antigen class I and II), complement fixing antibodies (C1q binding), and C-reactive protein titers were measured serially until elective sacrifice at 10 or 26 weeks. Serial transesophageal echocardiograms measured valve function and geometry. Differences were analyzed with Kruskal-Wallis and Wilcoxon rank-sum tests. RESULTS All animals survived and thrived, exhibiting excellent immediate implanted valve function by transesophageal echocardiograms. Over time, reference valves developed a smaller effective orifice area index (median, 0.84 cm(2)/m(2); range, 1.22 cm(2)/m(2)), whereas all bioengineered valves remained normal (effective orifice area index median, 2.45 cm(2)/m(2); range, 1.35 cm(2)/m(2); P = .005). None of the bioengineered valves developed elevated peak transvalvular gradients: 5.5 (6.0) mm Hg versus 12.5 (23.0) mm Hg (P = .003). Cryopreserved valves provoked the most intense antibody responses. Two of 5 human bioengineered and 2 of 3 baboon bioengineered valves did not provoke any class I antibodies. Bioengineered human (but not baboon) scaffolds provoked class II antibodies. C1q(+) antibodies developed in 4 recipients. CONCLUSIONS Valve dysfunction correlated with markers for more intense inflammatory provocation. The tested bioengineering methods reduced antigenicity of both human and baboon valves. Bioengineered replacement valves from both species were hemodynamically equivalent to native valves.

Intraoperative Hyperglycemia and Postoperative Bacteremia in the Pediatric Cardiac Surgery Patient

BACKGROUND Intraoperative hyperglycemia has been found to be associated with a higher incidence of postoperative infections in the adult cardiac surgery population. The goal of this study was to determine the association of intraoperative hyperglycemia and postoperative bacteremia in the pediatric population. METHODS A retrospective chart review of all cardiac surgical cases for patients 18 years of age or younger requiring cardiopulmonary bypass support between June 2002 and July 2007 yielded 1,132 total cases representing 992 unique patients. Patient demographic and clinical data of interest were collected. Descriptive statistics and regression analyses were performed to investigate the hypothesized relationship between glucose levels and infection rates. RESULTS From the 992 patient records examined, 15 patients exhibited a bacteremia within 14 days of surgery (1.5%). The association between the highest glucose during cardiopulmonary bypass and bacteremia reached statistical significance when the glucose level reached 175 mg/dL (chi(2) = 4.59, 1 degree of freedom; p = 0.032). A patient was more than three times as likely to have a postoperative bacteremia when the glucose level reached this amount or exceeded it (odds ratio, 3.3, 95% confidence interval, 1.04 to 10.39). Ten of the 15 (66.7%) postoperative infections occurred in patients with peak bypass glucose levels of at least 175 mg/dL. CONCLUSIONS Intraoperative hyperglycemia was found to be associated with a higher risk of postoperative bacteremia in the pediatric cardiac surgery population.

Initial Pediatric Cardiac Experience With Decellularized Allograft Patches

PURPOSE This study examines use patterns, early outcomes, and technical surgical adaptability of a newly approved decellularized allograft pulmonary artery patch for right ventricular outflow tract reconstructions in neonates and infants, including primary operations and reoperations. DESCRIPTION The study includes the 44 consecutive initial patients in which 46 patches were used for cardiovascular reconstruction between September 2009 and September 2010. Recorded variables include sex, age at operation, adverse outcome end points (eg, death, stenosis, aneurysm), congenital diagnoses, postoperative complications, and number, type, and location of patches. EVALUATION Patients were a mean age of 290±343 days at operation, and 54.5% were boys. Three types of patch were used: 58.7% thin, 21.7% thick, and 19.6% hemipulmonary. No device-related deaths or adverse events occurred. A biopsy specimen of one patch at elective reoperation demonstrated active recellularization, with no inflammation. CONCLUSIONS These patches have a wide range of applicability. Handling and technical flexibility is excellent and superior to standard options. There appears to be potential for autologous revitalization of the tissue.

Streptococcus Pneumoniae Causing Mycotic Aneurysm in a Pediatric Patient with Coarctation of the Aorta

Mycotic aneurysms are rare in patients with congenital heart disease, but may occur in those with aortic coarctation and abnormal aortic valve. Rapid diagnosis of mycotic aneurysm is of extreme importance given the significant reported incidence of morbidity and mortality across all age groups. Aortic aneurysm is uncommon before the second decade of life, and here we report a 10-year-old male patient with new diagnosis of aortic coarctation and bicuspid aortic valve, who developed a rapidly enlarging mycotic aneurysm from Streptococcus pneumoniae. Cardiac magnetic resonance imaging was crucial in making the diagnosis, as well as in follow-up.

Pulmonary Arterioplasty With Decellularized Allogeneic Patches

BACKGROUND Decellularized allogeneic nonvalved pulmonary artery patches for arterioplasty are a relatively new option compared with cryopreserved allogeneic, crosslinked xenogeneic bioprosthetic or synthetic materials. This study examines the midterm experience with a new decellularized allogeneic patch for congenital cardiac reconstructions. METHODS For this prospective postmarket approval, nonrandomized, inclusive observational study, we collected data on a consecutive cohort of 108 patients with cardiovascular reconstructions using 120 decellularized allogeneic pulmonary artery patches (MatrACELL; LifeNet Health, Inc, Virginia Beach, VA) between September 2009 and December 2012. One hundred of the patches were used for pulmonary arterioplasties. Two patients were lost early to follow-up and excluded from subsequent survival and durability analyses. Data included demographics, surgical outcomes, subsequent reoperations, and catheter reinterventions. These variables were also collected for an immediately preceding retrospective consecutive cohort of 100 patients with 101 pulmonary arterioplasty patches who received classical cryopreserved pulmonary artery allografts (n=59 patches and patients) or synthetic materials (n=41 patients with 42 patches) for pulmonary arterioplasties between 2006 and 2009. RESULTS In 106 patients with 118 decellularized patches, there were no device-related serious adverse events, no device failures, and no evidence of calcifications on chest roentgenograms. In contrast, the prior comparative pulmonary arterioplasty cohort of 100 patients experienced an overall 14.0% patch failure rate requiring device-related reoperations (p<0.0001) at mean duration of 194±104 days (range, 25 to 477 days). CONCLUSIONS The intermediate-term data obtained in this study suggest favorable performance by decellularized pulmonary artery patches, with no material failures or reoperations provoked by device failure.