Hassina Baraki

Orthotopic replacement of the aortic valve with decellularized allograft in a sheep model

Tissue engineered (TE) allografts have been successfully applied in pulmonary circulation. The behavior of TE valves based on decellularized scaffolds in systemic circulation remains unexplored. We investigated the function, histological changes, potential of in-vivo re-endothelialization of decellularized aortic valve allografts in orthotopic position in sheep. Ovine aortic valve conduits (n=12) were decellularized with detergents and implanted as an aortic root in lambs (35-45kg). For controls, fresh native ovine aortic valve conduits (n=6) were implanted. The valves were explanted at 3 and 9 months. In the experimental group, the valves exhibited trivial regurgitation and normal morphology with no signs of graft dilatation, degeneration or rejection. In some animals (n=2), we documented minimal calcification in the area of arterial anastomosis and in one, microthrombi formation on the leaflet surface. The luminal sides of the grafts were partially covered with an endothelial cell monolayer, neovasculogenesis was observed at the adventitial side. The valves in the control group appeared thickened, shrunken with marked calcification/degeneration signs, and advanced valve insufficiency. Detergent decellularized aortic valve allografts satisfy the higher requirements of the systemic circulation in sheep. As valve conduits become repopulated by endothelial and interstitial cells, they may re-gain the potential for growth.

Long-term results after aortic valve-sparing operation (David I)

OBJECTIVE Aortic valve-sparing David procedure has gained broad acceptance. However, few long-term results have been published. We present our results. METHODS More than 450 David procedures have been performed in our institution so far. Of these, 126 patients were operated between July 1993 and December 2000. Median age was 57 (8-83) years and 46 (36.5%) were female. As many as 26 (20.6%) had Marfan syndrome, 21 (16.7%) had acute aortic dissection type A (AADA) and 67 (53.2%) had additional procedures. RESULTS There were six (4.8%) deaths in 30 post-operative period (POD), four of whom had AADA. In the follow-up, there were 32 (25.4%) late deaths, 11 (34.4%) of these were caused by cardiac or underlying disease or op-related. As many as 15 (11.9%) patients were re-operated; six (40%) were Marfan patients and two (13.3%) had early endocarditis. Follow-up echocardiography of 76 (60.3%) event-free patients showed valve insufficiency (AI)≤AI I° in 68 (89.5%) and grade II in 7 (9.2%) patients. Leaflet degeneration due to proposed leaflet contact with the straight Dacron graft was not observed. A total of 36 (47.4%) patients were in New York Heart Association (NYHA) class I, 33 (43.4%) in NYHA II, and five (6.6%) were in class III. During the entire follow-up of 790 patient-years, there was no stroke or major bleeding. Survival at 1, 5 and 10 years was 93%, 85% and 70%, respectively. Freedom from valve replacement at 1, 5 and 10 years was 96%, 91% and 87%, respectively. CONCLUSIONS Regardless of the underlying pathology, valve-sparing David I procedure has acceptable long-term results. Valve-related complications such as stroke or major bleeding is exceedingly low.

Pacemaker dependency after isolated aortic valve replacement: do conductance disorders recover over time?

OBJECTIVES Permanent pacemaker (PPM) implantation is required in 3-8% of all patients undergoing aortic valve replacement (AVR). Our aim was to evaluate long-term PPM dependency and recovery of atrioventricular (AV) conduction disorders during follow-up in these patients. METHODS Since January 1997, a total of 2106 consecutive patients underwent isolated AVR at our institution. Of these, 138 patients (6.6%, 72 female, median age 71 (37-89) years) developed significant conduction disorders leading to PPM implantation postoperatively. Preoperative ECG showed normal sinus rhythm (n = 64), first degree AV block (n = 19), left bundle branch block (n = 13), right bundle branch block (n = 16), left anterior hemiblock (n = 14) and AV block with ventricular escape rhythm (n = 10). Atrial fibrillation was present in 23 patients. Pacemakers were implanted after a median of 7 (1-30) days following AVR. PPM dependency was analysed by ECG and pacemaker check during follow-up. RESULTS A total of 45 of 138 patients with postoperative PPM Implantation died during a mean follow-up time of 5.3 ± 4.7 years. A further 9 patients were lost to follow-up. Long-term survivals at 1, 5 and 10 years were 88%, 79% and 59%, respectively. Only 8 (10%) of 84 survivors were no longer pacemaker-dependent. The majority of patients (n = 66, 79%) required permanent ventricular stimulation, and the remaining 10 (13%) showed intermittent stimulation with a mean ventricular stimulation fraction of 73% (22-98%). CONCLUSIONS The majority of patients do not recover from AV conduction disorders after AVR. Since higher-grade AV blocks expose patients to a high risk of sudden death after surgery, we recommend early implantation of permanent pacemaker.

Decellularized aortic allografts versus pulmonary autografts for aortic valve replacement in the growing sheep model: haemodynamic and morphological results at 20 months after implantation

OBJECTIVES Pulmonary autografts (PAs) represent the substitute of choice for aortic valve (AV) replacement, especially in children and young adults. Similarly, decellularized aortic valve allografts (DAVAs) have shown excellent mid-term function when implanted in the systemic circulation. The aim of this study was to compare the performance of DAVAs with that of pulmonary autografts after a Ross procedure in the growing sheep model. METHODS AV root replacement was performed in female lambs (25 ± 3.4 kg) using either DAVAs (n = 5) or pulmonary autografts (n = 5) as in the Ross procedure. Sheep undergoing the Ross procedure received a decellularized pulmonary allograft in place of pulmonary valve. Haemodynamics was investigated by echocardiography and magnetic resonance imaging. The roots were explanted at 20 months and examined by histology to determine the degree of repopulation and quality of the extracellular matrix, and by immunohistochemistry to characterize the repopulating cells. RESULTS The mean valve diameter increased from 16 to 21 and from 16 to 25 mm in DAVAs and PAs, respectively. At explantation, one PA and one DAVA exhibited moderate insufficiency. Significant differences in transvalvular gradient were only found in PAs between implantation and prior to explantation. The cusps of all implants were soft, pliable and showed no major signs of degeneration. In the decellularized allografts, cell repopulation occurred at the wall and cusp level with a well-maintained, three-layered cusp structure. Ventricular cusp surface of decellularized allografts was more strongly repopulated than the arterial surface. Cusps were covered with cells positive for endothelial markers and were also repopulated by interstitial cells. CONCLUSIONS DAVAs and PAs provide adequate haemodynamics after AV replacement in the growing sheep. While decellularized grafts are repopulated by endothelial and interstitial cells, autografts maintain in general their native cell distribution. Maintenance of valvular competence during enlargement of the valve ring is, in our opinion, representative of the capacity for physiological growth in both graft types.

Substantial Early Loss of Induced Pluripotent Stem Cells Following Transplantation in Myocardial Infarction

The limited success of cardiac stem cell therapy has lately generated discussion regarding its effectiveness. We hypothesized that immediate cell loss after intramyocardial injection significantly obscures the regenerative potential of stem cell therapy. Therefore, our aim was to assess the distribution and quantity of induced pluripotent stem cells after intramyocardial delivery using in vivo bioluminescence analysis. In this context, we wanted to investigate if the injection of different cell concentrations would exert influence on cardiac cell retention. Murine-induced pluripotent stem cells were transfected for luciferase reporter gene expression and transplanted into infarcted myocardium in mice after left anterior descending coronary artery ligation. Cells were delivered constantly in aqueous media (15 μL) in different cell concentrations (group A, n = 10, 5.0 × 10(5) cells; group B, n = 10, 1.0 × 10(6) cells). Grafts were detected using bioluminescence imaging. Organ explants were imaged 10 min after injection to quantify early cardiac retention and cell biodistribution. Bioluminescence imaging showed a massive early displacement from the injection site to the pulmonary circulation, leading to lung accumulation. Mean cell counts of explanted organs in group A were 7.51 × 10(4) ± 4.09 × 10(3) (heart), 6.44 × 10(4) ± 2.48 × 10(3) (left lung), and 8.06 × 10(5) ± 3.61 × 10(3) (right lung). Respective cell counts in group B explants were 1.69 × 10(5) ± 7.69 × 10(4) (heart), 2.11 × 10(5) ± 4.58 × 10(3) (left lung), and 3.25 × 10(5) ± 9.35 × 10(3) (right lung). Applying bioluminescence imaging, we could unveil and quantify massive early cardiac stem cell loss and pulmonary cell accumulation following intramyocardial injection. Increased injection concentrations led to much higher intracardiac cell counts; however, pulmonary biodistribution of transplanted cells still persisted. Therefore, we recommend applying tissue engineering techniques for cardiac stem cell transplantations in order to improve cardiac retention and limit biodistribution.

Magnetic resonance imaging of soft tissue infection with iron oxide labeled granulocytes in a rat model.

Object We sought to detect an acute soft tissue infection in rats by magnetic resonance imaging (MRI) using granulocytes, previously labeled with superparamagnetic particles of iron oxide (SPIO). Materials and Methods Parasternal infection was induced by subcutaneous inoculation of Staphylococcus aureus suspension in rats. Granulocytes isolated from isogenic donor rats were labeled with SPIO. Infected rats were imaged by MRI before, 6 and 12 hours after intravenous injection of SPIO-labeled or unlabeled granulocytes. MR findings were correlated with histological analysis by Prussian blue staining and with re-isolated SPIO-labeled granulocytes from the infectious area by magnetic cell separation. Results Susceptibility effects were present in infected sites on post-contrast T2*-weighted MR images in all animals of the experimental group. Regions of decreased signal intensity (SI) in MRI were detected at 6 hours after granulocyte administration and were more pronounced at 12 hours. SPIO-labeled granulocytes were identified by Prussian blue staining in the infected tissue and could be successfully re-isolated from the infected area by magnetic cell separation. Conclusion The application of SPIO-labeled granulocytes in MRI offers new perspectives in diagnostic specificity and sensitifity to detect early infectious processes.

Transplantation of purified iPSC-derived cardiomyocytes in myocardial infarction

Background Induced pluripotent stem cells (iPSC) can be differentiated into cardiomyocytes and represent a possible autologous cell source for myocardial repair. We analyzed the engraftment and functional effects of murine iPSC-derived cardiomyocytes (iPSC-CMs) in a murine model of myocardial infarction. Methods and results To maximize cardiomyocyte yield and purity a genetic purification protocol was applied. Murine iPSCs were genetically modified to express a Zeocin™ resistance gene under control of the cardiac-specific α-myosin heavy chain (α-MHC, MYH6) promoter. Thus, CM selection was performed during in vitro differentiation. iPSC-CM aggregates (“cardiac bodies”, CBs) were transplanted on day 14 after LAD ligation into the hearts of previously LAD-ligated mice (800 CBs/animal; 2-3x106 CMs). Animals were treated with placebo (PBS, n = 14) or iPSC-CMs (n = 35). Myocardial remodeling and function were evaluated by magnetic resonance imaging (MRI), conductance catheter (CC) analysis and histological morphometry. In vitro and in vivo differentiation was investigated. Follow up was 28 days (including histological assessment and functional analysis). iPSC-CM purity was >99%. Transplanted iPSC-CMs formed mature grafts within the myocardium, expressed cardiac markers and exhibited sarcomeric structures. Intramyocardial transplantation of iPSC-CMs significantly improved myocardial remodeling and left ventricular function 28 days after LAD-ligation. Conclusions We conclude that iPSCs can effectively be differentiated into cardiomyocytes and genetically enriched to high purity. iPSC derived cardiomyocytes engraft within the myocardium of LAD-ligated mice and contribute to improve left ventricular function.

Beating Heart Versus Arrested Heart Isolated Tricuspid Valve Surgery

We analyzed the long-term results of two surgical techniques (beating versus non-beating) for isolated tricuspid valve (TV) surgery.The long-term results of 92 consecutive patients who underwent isolated TV surgery were analyzed. We compared patients with beating heart (BH) surgery (n = 48) with patients undergoing arrested heart (AH) surgery (n = 44).BH surgery was more frequently chosen in urgent/emergent operations (P = 0.029) and in redo-operations (P < 0.001). Preoperatively, the rates of renal insufficiency (P = 0.002) and EuroSCORE (P = 0.019) were higher in the BH group than in the AH group. There were no differences in perioperative outcomes and 30-day mortality between the groups. However, freedom from reoperation was significantly lower in the BH group compared to the AH group (P = 0.039). We observed a trend towards lower survival rates at 1, 5, and 10 years in the BH group (77%, 54%, and 41%) compared to those of the AH group (86%, 75%, and 72%, P = 0.062). Multivariate Cox hazard model analysis revealed preoperative heart rhythm (P = 0.014, odds ratio [OR] = 2.296) and EuroSCORE (P = 0.022, OR = 1.049) as independent risk factors for mortality after isolated TV surgery.The superiority of BH surgery over AG surgery was not proven. Surgical intervention should be considered early, since patients with elevated EuroSCORES and arrhythmia have significantly higher mortality rates.

Macroscopic fluorescence imaging: a novel technique to monitor retention and distribution of injected microspheres in an experimental model of ischemic heart failure.

Background The limited effectiveness of cardiac cell therapy has generated concern regarding its clinical relevance. Experimental studies show that cell retention and engraftment are low after injection into ischemic myocardium, which may restrict therapy effectiveness significantly. Surgical aspects and mechanical loss are suspected to be the main culprits behind this phenomenon. As current techniques of monitoring intramyocardial injections are complex and time-consuming, the aim of the study was to develop a fast and simple model to study cardiac retention and distribution following intramyocardial injections. For this purpose, our main hypothesis was that macroscopic fluorescence imaging could adequately serve as a detection method for intramyocardial injections. Methods and Results A total of 20 mice underwent ligation of the left anterior descending artery (LAD) for myocardial infarction. Fluorescent microspheres with cellular dimensions were used as cell surrogates. Particles (5×105) were injected into the infarcted area of explanted resting hearts (Ex vivo myocardial injetions EVMI, n = 10) and in vivo into beating hearts (In vivo myocardial injections IVMI, n = 10). Microsphere quantification was performed by fluorescence imaging of explanted organs. Measurements were repeated after a reduction to homogenate dilutions. Cardiac microsphere retention was 2.78×105±0.31×105 in the EVMI group. In the IVMI group, cardiac retention of microspheres was significantly lower (0.74×105±0.18×105; p<0.05). Direct fluorescence imaging revealed venous drainage through the coronary sinus, resulting in a microsphere accumulation in the left (0.90×105±0.20×105) and the right (1.07×105±0.17×105) lung. Processing to homogenates involved further particle loss (p<0.05) in both groups. Conclusions We developed a fast and simple direct fluorescence imaging method for biodistribution analysis which enabled the quantification of fluorescent microspheres after intramyocardial delivery using macroscopic fluorescence imaging. This new technique showed massive early particle loss and venous drainage into the right atrium leading to substantial accumulation of graft particles in both lungs.

Do Patients Profit from Third Time CABG

Introduction It has been shown that in experienced hands repeated CABG is doable procedure. However the quality of life after third time CABG has not been evaluated so far. Patients and Methods The peri-operative data of 25 (22 male, mean age of 65.5 ± 8.0 years) consecutive patients in a single centre undergoing third time-CABG from 4/96 to 11/06 were studied. Quality of life (QoL) was assessed by Short Form (SF)-36 Questionnaire. Results 30 day mortality was 12% (3/25). Seven died during follow-up. In 15 survivors median follow-up was 94 months (2–122 months). 1-, 5-, and 10-year survival were 77.8%, 65.0%, and 53.1%, respectively. Present NYHA status was significantly improved in comparison to preoperative values (2.4 ± 0.8 vs. 3.2 ± 0.56, p = 0.012). QoL was comparable with an age matched general population with heart insufficiency. Conclusion Third time CABG can be performed with acceptable peri-operative mortality. Significant improvement of NYHA status and acceptable quality of life results justifies our surgical approach in this challenging patient cohort.