Degeneration of biological heart valve grafts in a rat model of superoxide dismutase-3 deficiency.

While oxidative stress is known as key element in the pathogenesis of atherosclerosis and calcific aortic valve disease, its role in the degeneration of biological cardiovascular grafts has not been clarified yet. Therefore, the present study aimed to examine the impact of oxidative stress on the degeneration of biological cardiovascular allografts in a standardized chronic implantation model realized in rats exhibiting superoxide dismutase 3 deficiency (SOD3(-) ). Rats with SOD3 loss-of-function mutation (n = 24) underwent infrarenal implantation of cryopreserved valved aortic conduits, while SOD3-competent recipients served as controls (n = 28). After a follow-up period of 4 or 12 weeks, comparative analyses addressed degenerative processes, hemodynamics, and evaluation of the oxidative stress model. SOD3(-) rats presented decreased circulating SOD activity (p = .0079). After 12 weeks, 58% of the implant valves in SOD3(-) rats showed regurgitation (vs. 31% in controls, p = .2377). Intima hyperplasia and chondro-osteogenic transformation contributed to progressive graft calcification (p = .0024). At 12 weeks, hydroxyapatite deposition (p = .0198) and the gene expression of runt-related transcription factor-2 (Runx2) (p = .0093) were significantly enhanced in group SOD3(-) . This study provides the first in vivo evidence that impaired systemic antioxidant activity contributes to biological cardiovascular graft degeneration.

A Role for Peroxisome Proliferator-Activated Receptor Gamma Agonists in Counteracting the Degeneration of Cardiovascular Grafts.

ABSTRACT: Aortic valve replacement for severe stenosis is a standard procedure in cardiovascular medicine. However, the use of biological prostheses has limitations especially in young patients because of calcifying degeneration, resulting in implant failure. Pioglitazone, a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist, was shown to decrease the degeneration of native aortic valves. In this study, we aim to examine the impact of pioglitazone on inflammation and calcification of aortic valve conduits (AoC) in a rat model. Cryopreserved AoC (n = 40) were infrarenally implanted into Wistar rats treated with pioglitazone (75 mg/kg chow; n = 20, PIO) or untreated (n = 20, controls). After 4 or 12 weeks, AoC were explanted and analyzed by histology, immunohistology, and polymerase chain reaction. Pioglitazone significantly decreased the expression of inflammatory markers and reduced the macrophage-mediated inflammation in PIO compared with controls after 4 (P = 0.03) and 12 weeks (P = 0.012). Chondrogenic transformation was significantly decreased in PIO after 12 weeks (P = 0.001). Calcification of the intima and media was significantly reduced after 12 weeks in PIO versus controls (intima: P = 0.008; media: P = 0.025). Moreover, echocardiography revealed significantly better functional outcome of the AoC in PIO after 12 weeks compared with control. Interestingly, significantly increased intima hyperplasia could be observed in PIO compared with controls after 12 weeks (P = 0.017). Systemic PPAR-gamma activation prevents inflammation as well as intima and media calcification in AoC and seems to inhibit functional impairment of the implanted aortic valve. To further elucidate the therapeutic role of PPAR-gamma regulation for graft durability, translational studies and long-term follow-up data should be striven for.

The impact of socio-demographic factors on health-related quality of life after coronary artery bypass surgery.

OBJECTIVES: To achieve a beneficial impact on long-term outcome after coronary artery bypass grafting (CABG), the goal of the present study was the early identification of patients at risk of impaired postoperative health-related quality of life (HRQoL), particularly evaluating the significance of socio-demographic variables. METHODS: In this prospective, single-centre cohort study of patients having an isolated CABG (January 2004-December 2014), preoperative socio-demographic (preSOC) and preoperative medical variables as well as 6-month follow-up data including the Nottingham Health Profile were analysed in 3,237 patients. RESULTS: All preSOC (gender, age, marriage and employment) and follow-up (chest pain, dyspnoea) variables proved to have significant influence on HRQoL (P < 0.001), male patients below 60 years being particularly impaired. The effects of marriage and employment on HRQoL are modulated by age and gender. The significance of the predictors of reduced HRQoL differs between the 6 Nottingham Health Profile domains. Multivariable regression analyses revealed explained proportions of variance amounting to 7% for preSOC and 4% for preoperative medical variables. CONCLUSIONS: The identification of patients at risk of impaired postoperative HRQoL is decisive for providing additional support. This study reveals that the assessment of 4 preoperative socio-demographic characteristics (age, gender, marriage, employment) is more predictive of HRQoL after CABG than are multiple medical variables.

Bilateral Internal Thoracic Artery Minimally Invasive CABG Management in COPD.

Background Off-pump multi-arterial minimally invasive coronary surgery via anterolateral mini-thoracotomy has become a feasible and safe procedure. Case Description We report on a 61-year-old patient with a coronary one-vessel disease with severely stenotic left anterior descending artery and diagonal branch, additionally suffering from chronic obstructive pulmonary disease with severely impaired lung function. Using a fan technique allowing for double lung ventilation, the patient was successfully operated grafting both internal thoracic arteries via a left anterolateral mini-thoracotomy. Conclusion Anaortic, minimally invasive off-pump coronary artery bypass grafting is an excellent technique to achieve myocardial revascularization with both internal thoracic arteries even in patients with impaired lung function.

Impact of PPAR-gamma activation on the durability of biological heart valve prostheses in hypercholesterolaemic rats.

OBJECTIVES: Hypercholesterolaemia and obesity are risk factors for the development of calcified aortic valve disease and common comorbidities in respective patients. Peroxisome proliferator-activated receptor gamma activation has been shown to reduce the progression of native aortic valve sclerosis, while its effect on bioprosthetic valve degeneration is yet unknown. This project aims to analyse the impact of pioglitazone, a peroxisome proliferator-activated receptor gamma agonist, on the degeneration of biological aortic valve conduits in an implantation model in obese and hypercholesterolaemic rats. METHODS: Cryopreserved allogenic rat aortic valve conduits (n = 40) were infrarenally implanted into Wistar rats on high-fat (34.6%) diet. One cohort was treated with pioglitazone (75 mg/kg chow; n = 20, group PIO) and compared to untreated rats (n = 20, group control). After 4 or 12 weeks, conduits were explanted and analysed by (immuno-)histology and real-time polymerase chain reaction. RESULTS: A significantly decreased intima hyperplasia occurred in group PIO compared to control after 4 (P = 0.014) and 12 weeks (P = 0.045). Calcification of the intima was significantly decreased in PIO versus control at 12 weeks (P = 0.0001). No significant inter-group differences were shown for media calcification after 4 and 12 weeks. Echocardiographically, significantly lower regurgitation through the implanted aortic valve conduit was observed in PIO compared to control after 4 (P = 0.018) and 12 weeks (P = 0.0004). Inflammatory activity was comparable between both groups. CONCLUSIONS: Systemic peroxisome proliferator-activated receptor gamma activation decreases intima hyperplasia and subsequent intima calcification of cryopreserved allografts in obese, hypercholesterolaemic recipients. Additionally, it seems to inhibit functional impairment of the implanted aortic valve. Further preclinical studies are required to determine the long-term impact of peroxisome proliferator-activated receptor gamma agonists on graft durability.

Dichloroacetate inhibits the degeneration of decellularized cardiovascular implants.

OBJECTIVES: Intima hyperplasia is a major issue of biological cardiovascular grafts resulting in progressive in vivo degeneration that particularly decreases the durability of coronary and peripheral vascular bypasses. Previously, dichloroacetate (DCA) has been reported to prevent the formation of hyperplastic intima in injured arteries. In this study, the effect of DCA on the neointima formation and degeneration of decellularized small-caliber implants was investigated in a rat model. METHODS: Donor rat aortic grafts (n = 22) were decellularized by a detergent-based technique, surface-coated with fibronectin (50 µl ml-1, 24 h incubation) and implanted via anastomoses to the infrarenal aorta of the recipients. Rats in the DCA group (n = 12) received DCA via drinking water during the whole follow-up period (0.75 g l-1), while rats without DCA treatment served as controls (n = 10). At 2 (n = 6 + 5) and 8 (n = 6 + 5) weeks, the grafts were explanted and examined by histology and immunofluorescence. RESULTS: Systemic DCA treatment inhibited neointima hyperplasia, resulting in a significantly reduced intima-to-media ratio (median 0.78 [interquartile range, 0.51-1.27] vs 1.49 [0.67-2.39] without DCA, P < 0.001). At 8 weeks, neointima calcification, as assessed by an established von Kossa staining-based score, was significantly decreased in the DCA group (0 [0-0.25] vs 0.63 [0.06-1.44] without DCA, P < 0.001). At 8 weeks, explanted grafts in both groups were luminally completely covered by an endothelial cell layer. In both groups, inflammatory cell markers (CD3, CD68) proved negative. CONCLUSIONS: Systemic DCA treatment reduces adverse neointima hyperplasia in decellularized small-caliber arterial grafts, while allowing for rapid re-endothelialization. Furthermore, DCA inhibits calcification of the implants.

Controlled autologous recellularization and inhibited degeneration of decellularized vascular implants by side-specific coating with stromal cell-derived factor 1α and fibronectin.

Optimized biocompatibility is crucial for the durability of cardiovascular implants. Previously, a combined coating with fibronectin (FN) and stromal cell-derived factor 1α (SDF1α) has been shown to accelerate the in vivo cellularization of synthetic vascular grafts and to reduce the calcification of biological pulmonary root grafts. In this study, we evaluate the effect of side-specific luminal SDF1α coating and adventitial FN coating on the in vivo cellularization and degeneration of decellularized rat aortic implants. Aortic arch vascular donor grafts were detergent-decellularized. The luminal graft surface was coated with SDF1α, while the adventitial surface was coated with FN. SDF1α-coated and uncoated grafts were infrarenally implanted (n = 20) in rats and followed up for up to eight weeks. Cellular intima population was accelerated by luminal SDF1α coating at two weeks (92.4 ± 2.95% versus 61.1 ± 6.51% in controls, p < 0.001). SDF1α coating inhibited neo-intimal hyperplasia, resulting in a significantly decreased intima-to-media ratio after eight weeks (0.62 ± 0.15 versus 1.35 ± 0.26 in controls, p < 0.05). Furthermore, at eight weeks, media calcification was significantly decreased in the SDF1α group as compared to the control group (area of calcification in proximal arch region 1092 ± 517 µm2 versus 11 814 ± 1883 µm2, p < 0.01). Luminal coating with SDF1α promotes early autologous intima recellularization in vivo and attenuates neo-intima hyperplasia as well as calcification of decellularized vascular grafts.

A magnetic resonance imaging-compatible small animal model under extracorporeal circulation.

The impact of different extracorporeal circulation (ECC) scenarios on arterial blood flow profiles has not yet been revealed. To allow for exact measurements, magnetic resonance imaging (MRI) during ECC is required. Therefore, the present study addressed the feasibility of a high-resolution MRI-compatible animal model of ECC. For usage in New Zealand White rabbits, we developed an ECC device, the tubes of which were long enough to eliminate impacts of the magnetic field on the blood pump and heart-lung control machine. The miniaturized ECC system via thoracic access comprised an infant oxygenator, a pulsatile centrifugal pump, 1/8″ tubes, a 10-Fr aortic cannula and a 12-Fr venous cannula for vacuum-assisted drainage. This miniaturized ECC system has very low priming volume (230-255 ml) to reduce the system-inherent haemodilution to 50%. Consequently, haemoglobin rates remained high enough to guarantee adequate oxygenation (arterial pressure of oxygen >200 mmHg). Optimized venous drainage by an additionally inserted pulmonary artery vent catheter resulted in sufficient blood flow (31.6-65.8 ml/min/kg) that was maintained for 60 min with pulsatility. The current study demonstrates the feasibility of MRI-compatible ECC in rabbits, and this model allows for real-time blood flow profile measurements during different ECC scenarios in future projects.