Tim Attmann

Gene therapy in cardiac surgery: intramyocardial injection of naked plasmid DNA for chronic myocardial ischemia

OBJECTIVE Growth factor gene therapy represents one current approach in the therapy of myocardial ischemia. We assessed the in vitro and in vivo expression of naked plasmid DNA aiming at preservation of function in a chronically ischemic myocardial model. METHODS In vitro: Primary cardiac fibroblasts were transfected with plasmids encoding enhanced green fluorescent protein, human VEGF(121), human FGF-2, or porcine MCP-1. Protein synthesis was assessed microscopically, by ELISA, Western blotting, or intracellular immunofluorescence. In vivo: A LAD stenosis was created in healthy pigs. One week later, segmental myocardial shortening (SMS) and systemic hemodynamics (left ventricular stroke work index, LVSWI, time derivative of left ventricular pressure, dp/dt(max)) were assessed at baseline. Afterwards, the ischemic area received either intramyocardial injections of naked cytokine plasmid DNA or vector only, or was left untreated. One myocardial sample taken 1 h after plasmid injection was subjected to RT-PCR and PCR. After 3 months, cardiac function was re-examined. RESULTS In vitro: Transfection of cardiac fibroblasts resulted in high gene expression for several days. In vivo: Plasmid-specific DNA and mRNA were found 1 h after plasmid injection (n=1). After 3 months, VEGF, FGF-2, and vector rendered better results of regional contractility at rest and of LVSWI. However, only VEGF and FGF-2 were effective with regard to regional contractility under dobutamine stress and to left ventricular contractility. CONCLUSION In conclusion, intramyocardial injection of naked plasmid DNA encoding VEGF(121) or FGF-2 improved myocardial function in chronic ischemia in more aspects than vector only and was superior to untreated ischemia or MCP-1. This strategy can be considered a successful tool for growth factor stimulated preservation of function in chronic myocardial ischemia.

Comparison of protein with DNA therapy for chronic myocardial ischemia using fibroblast growth factor-2

OBJECTIVE Treatment of coronary disease by growth factors has become an increasingly used strategy for otherwise untreatable patients and is subject to a number of clinical studies. The aim is to stimulate the development of a sufficient collateral circulation and hereby to rescue cardiac function. The objective of our study was to compare the effectiveness of fibroblast growth factor-2 (FGF-2) as protein and as naked plasmid DNA in a porcine model of chronic myocardial ischemia. MATERIALS AND METHODS A severe stenosis of the left anterior descending artery (LAD) artery was created in healthy pigs. After 1 week, perfusion and regional and global contractility was assessed at baseline at rest and under stress. Afterwards, recombinant FGF-2 (n=6) or naked plasmid DNA encoding FGF-2 (n=7) was intramyocardially injected into the LAD territory. Control animals were left untreated (n=5). After 3 months, the animals were re-examined and underwent immunohistologic analysis. One animal received an Enhanced Green Fluorescent Protein plasmid. RESULTS Plasmid-dependent protein synthesis was present in cardiomyocytes. FGF-2 protein as well as plasmid injections resulted in an increased number of capillaries and of arterioles compared with untreated ischemia. The improvement of the regional myocardial blood flow by FGF-2 plasmid therapy at rest might however indicate the effectiveness of the DNA application for the induction of a collateral circulation. A benefit from FGF-2 plasmid therapy was revealed with regard to regional contractility. Systemic hemodynamics were partially improved following plasFGF-2 treatment. CONCLUSIONS In this porcine model of chronic myocardial ischemia, intramyocardial injection of FGF-2 plasmid was more effective than of FGF-2 protein in improving regional perfusion and contractility compared to untreated ischemia.

Percutaneous aortic valve replacement: Endovascular resection of human aortic valves in situ

OBJECTIVE Transluminal in vitro resection of severely calcified human aortic valves has already been successfully carried out by our group. The aim of this study was to analyze endovascular laser-assisted resection of human aortic valves in situ in 10 human cadavers. MATERIAL AND METHODS After anterolateral minithoracotomy, the aortic valve isolation chamber system was inserted into the descending aorta and pushed forward transluminally into the aortic position to generate a separate operation space between the subvalvular and the proximal ascending aortic area. After deployment and sealing of the chamber, stable function with a continuous chamber lavage of 1.58 L/min saline solution was established (8/10 cases). The endoscopically guided laser fiber was delivered via the right carotid artery. After fixation of a leaflet by a forceps catheter, the native leaflets were resected each by a thulium:YAG laser with 20-W power rating. Macropathology and micropathology of surrounding anatomic structures were analyzed. RESULTS The duration of transluminal positioning and deployment of the aortic valve isolation chamber took 7.3 +/- 5.8 minutes. Fluoroscopy confirmed sealed chambers. The resection was completed in all leaflets and took, on average, 6.0 +/- 3.5 minutes per leaflet. The aortic wall was moderately injured in 4 of 10 cases and the aortic annulus in two cases with one aortic wall perforation. The surrounding tissue, the coronary ostia, the mitral valve, and the left ventricular outflow tract remained unaffected. CONCLUSION This study demonstrates the feasibility of endovascular resection of human aortic valves in situ. This is a subsequent step toward complete percutaneous replacement (resection and implantation) of human aortic valves.

Future horizons in surgical aortic valve replacement: lessons learned during the early stages of developing a transluminal implantation technique.

The aim of this study was to develop a heart valve prosthesis that could be transluminally inserted through the infrarenal aorta in pigs and the femoral artery in humans. Therefore, this valve prosthesis had to be foldable to a diameter of approximately 8 mm, self-expandable when released in the vascular system, and equipped with an anchoring mechanism.For implantation, a suitable catheter delivery system for insertion via the abdominal aorta in pigs also was designed. Furthermore, an operation method, including positioning of the catheter delivery system and deployment of the valved stent under fluoroscopic and echocardiographic control, was developed.A series of different prototypes of the valved stents and catheter delivery systems was produced to optimize design and handling. These prototypes were tested in vitro in a circulation model, and those showing satisfying hemodynamic properties were implanted in pigs as in vivo studies afterwards.The valved stents had a good hemodynamic function in vitro and in vivo with no more than a mild regurgitation or stenosis. Valve movements were satisfying, and the design proved to be generally feasible. However, positioning and anchoring were still difficult; some stents were tilted in the lumen or migrated after implantation.

Transmyocardial laser revascularization combined with vascular endothelial growth factor121 (VEGF121) gene therapy for chronic myocardial ischemia – do the effects really add up?

OBJECTIVE Different therapy strategies for coronary disease in conventionally untreatable patients have been developed, among them transmyocardial laser revascularization (TMLR) and the application of growth factors. The objective of our study was to determine whether a combined therapy of TMLR with a vascular endothelial growth factor(121) (VEGF(121)) plasmid is able to stimulate the development of sufficient collateral circulation and hereby to preserve cardiac function. MATERIALS AND METHODS A severe stenosis of the left anterior descending artery was created in healthy pigs. After 1 week, perfusion and regional contractility were assessed at baseline. Afterwards, the ischemic area was treated with TMLR (n=8), intramyocardial injection of naked plasmid DNA encoding VEGF(121) (n=7), or both (n=7). Control animals were left untreated (n=8). After 3 months, the animals were re-examined and underwent immunohistological analysis. RESULTS The number of capillaries increased only after injection of VEGF(121) plasmid alone compared to untreated ischemia and to the other therapy groups, whereas the number of arterioles was higher following TMLR treatment alone or in combination with VEGF(121) than it was in the case in untreated ischemic animals. However, only combined VEGF(121)+TLMR therapy resulted in an improvement in regional myocardial blood flow in comparison with 1 week ischemia, indicating the efficient development of collateral circulation. In contrast, better regional contractility compared to the 1-week baseline, as well as restoration of the pre-ischemic values, were achieved by both VEGF(121) and combined VEGF(121)+TLMR therapies. CONCLUSIONS This study of chronic myocardial ischemia with a porcine model indicates a synergistic action of TMLR and VEGF(121) gene therapy. Combined treatment alone achieved an increase of regional myocardial perfusion, which accompanied arteriogenesis and corresponded with the restoration of regional function.

Mitral valved stent implantation: An overview

Abstract To date, transcatheter valve implantation is limited to the replacement of pulmonary and aortic valves. The aim of this study was to analyze a valved stent for minimally invasive implantation in the mitral position. A self-expanding mitral valved stent was designed for transapical implantation. Thirty pigs underwent off-pump mitral valved stent implantation with follow-up times of 60 minutes (n = 17) and seven days (n = 13). Transesophageal echocardiography and computed tomography were used to evaluate stent function and positioning. After valved stent deployment, accurate adjustment of the intra-annular position reduced paravalvular leakage in all animals. Accurate positioning was established in all but five animals. The average mean transvalvular gradient across the mitral valve and the left ventricular outflow tract recorded immediately after deployment, six hours and one week were 1.85 ± 0.95 mmHg, 3.45 ± 1.65 mmHg, 4.15 ± 2.3 mmHg and 1.35 ± 1.35 mmHg, 1.45 ± 0.7 mmHg, 1.9 ± 0.65 mmHg, respectively. No valved stent migration, embolization, systolic anterior movement or left ventricular outflow tract obstruction was observed. The mitral valved stent can be deployed in a reproducible manner to achieve reliable stent stability, minimal gradients across the left ventricular outflow tract and adequate stent function in acute and short term experimental settings.

Octogenarians Undergoing Combined Aortic Valve Replacement and Myocardial Revascularization: Perioperative Mortality and Medium-Term Survival

OBJECTIVE Aim of the study was to answer the question whether the mortality and morbidity of octogenarians undergoing combined aortic valve replacement and myocardial revascularization (AVR + CABG) is higher than that of younger patients. PATIENTS AND METHODS Between 01/1995 and 12/2002, 242 patients underwent AVR + CABG in our institution. 37 patients were older than 80 years (16 male, 21 female, median pressure gradient over the aortic valve: 53 mmHg, median EF: 62%), 205 patients were younger than 80 years (133 male, 72 female, median gradient 48 mmHg, median EF: 61%). NYHA class, aortic valve area and valve calcification were worse in the 80+ group. Biological valve prostheses were implanted in 94.6% of the older and in 45.4% of the younger patients (p < 0.001). RESULTS Perioperative complications occurred more often (p = 0.0188) in the 80+ group (86.5% experienced 1 or more complications) than in the 80- group (66.3%). Similarly, the MACE (Major Adverse Cardiovascular Events) rate was higher (p = 0.0448) in the 80+ group than in the 80- group. Bleeding occurred (p = 0.092) more often in younger (9.3%) than in older (0%) patients, while renal insufficiency was more frequent (p = 0.0164) in older (21.6%) than in younger patients (7.8 %). The 30-day mortality was higher (p = 0.0045) in older (21.6%) than in younger patients (5.8%). Multivariate analysis revealed an odds ratio for early death of 2.9 (CI 1.014-8.397) for patients older than 80 years. The late death rate within the first 5 years after surgery was comparable in both groups (80- group 24.4%, 80+ group 24.3%). Postoperative quality of life was significantly worse in the 80+ group in 4 out of 8 functions. CONCLUSIONS Octogenarians undergoing AVR + CABG have a relatively high perioperative complication rate and mortality, but show a stable medium-term survival. The perioperative complication rate is higher in older than in younger patients, and the postoperative quality of life with regard to bodily functions is acceptable but significantly worse than that of younger patients.

Impact of an Interleukin-1 Receptor Antagonist and Erythropoietin on Experimental Myocardial Ischemia/Reperfusion Injury

Background. Revascularization of infarcted myocardium results in release of inflammatory cytokines mediating myocardial reperfusion injury and heart failure. Blockage of inflammatory pathways dampens myocardial injury and reduces infarct size. We compared the impact of the interleukin-1 receptor antagonist Anakinra and erythropoietin on myocardial ischemia/reperfusion injury. In contrast to others, we hypothesized that drug administration prior to reperfusion reduces myocardial damage. Methods and Results. 12–15 week-old Lewis rats were subjected to myocardial ischemia by a 1 hr occlusion of the left anterior descending coronary artery. After 15 min of ischemia, a single shot of Anakinra (2 mg/kg body weight (bw)) or erythropoietin (5000 IE/kg bw) was administered intravenously. In contrast to erythropoietin, Anakinra decreased infarct size (P < 0.05, N = 4/group) and troponin T levels (P < 0.05, N = 4/group). Conclusion. One-time intravenous administration of Anakinra prior to myocardial reperfusion reduces infarct size in experimental ischemia/reperfusion injury. Thus, Anakinra may represent a treatment option in myocardial infarction prior to revascularization.

Percutaneous Valve Replacement: Significance of Different Delivery Systems In Vitro and In Vivo

Background and purposePercutaneous heart valve replacement is an exciting growing field in cardiovascular medicine yet still with some major problems. Only sophisticated improvement of the instruments could make it a real alternative to conventional surgery. Therefore, the aim of this study was to evaluate different delivery devices for percutaneous heart valve replacement in vitro and in vivo.MethodsA catheter prototype designed by our group, and two commercially available devices for the delivery of esophageal stents and aortic endoprostheses, were tested. After in vitro experiments, an ovine animal model of transfemoral pulmonary valve implantation was established using biological valved self-expanding stents. Only the delivery device for aortic endografts (Medtronic, Talent, Santa Rosa, CA, USA) allowed fast in vitro procedures without material fatigue. This device was chosen for the in vivo tests.ResultsTechnical success was achieved in 9 of 10 animals (90%). One animal died after perforation of the ventricular wall. Orthotopic pulmonary placement was performed in 6 animals and intentional supravalvular valved stent placement in 3 animals.ConclusionsAn adequate in vitro model for this evolving field of interventional heart valve replacement is presented. Furthermore, the present study pinpoints the key characteristics that are mandatory for a delivery system in percutaneous pulmonary valve implantation. With regard to the delivery device’s ductility observed during this “venous” study, an approach to transfemoral aortic valve implantation seems feasible.

Percutaneous aortic valve replacement: gross anatomy and histological findings after transapical and endoluminal resection of human aortic valves in situ,

OBJECTIVE Transluminal resection of the aortic valve was already successfully carried out by our group. The aim of this study was the analysis of the gross anatomy and the histology of the surrounding tissue after resection. METHODS Aortic valve resection was performed in postmortem human hearts (endoluminal (EL) n=9, transapical (TA) n=4). After deployment of the aortic valve isolation chamber, the leaflets were resected with a Thullium:YAG laser scalpel (cw, 20W). After resection, the hearts were analyzed to check for lesions caused by resectioning the associated tools. Therefore, gross anatomy and histological analysis were performed (H&E staining). RESULTS Lesions of the aortic annulus were seen in 3/9 (EL) (depth: 583+/-186 microm) and 2/4 (TA) (120 microm and one complete perforation), lesions of the aorta (ascending-arch-descending) in 4-9-0/9 (EL) and 0-0-0/4 (TA), lesions of the mitral valve in 0/9 (EL) and 0/4 (TA), lesions of the papillary muscle in 0/9 (EL) and 2/4 (TA) (depth: 400 microm and 450 microm), lesions of the endomyocardium in 0/9 (EL) and 4/4 (TA) (depth: 258+/-102 microm). The coronary ostia remained unaffected. CONCLUSIONS This study shows fewer severe lesions in the aorta after transapical antegrade access compared to the transluminal retrograde approach. Especially noteworthy is that the aortic arch remains unaffected by the transapical procedure. These data demonstrate the transapical approach as less hazardous.