Human or animal homograft: could they have a future as a biological scaffold for engineered heart valves?

Tissue-engineered heart valves (TEHVs) promise to be the ideal heart valve replacement: they have the potential to grow and repair within the host, to minimise inflammatory and immunological responses and to limit thromboembolism. Viable cells included in TEHVs can theoretically adapt to a growing and changing environment exactly as a native biological structure. This could be extremely important in case of paediatric applications, where reoperations are frequently required to replace failed valve substitutes or to accommodate the growth of the patient. At present time the biological matrix from allogenic or xenogenic decellularized valves represents an appropriate valve scaffold in TEHVs, showing theoretically an ability to grow and repair within the host. Viable cells included in extracellular valve matrix can theoretically adapt to a growing and changing environment like the native biological structure. The aim of this paper is to present a review concerning the use of homograft and allograft valves as an ideal substrate for cardiac engineered tissue valves that represent an exciting possibility for in situ regeneration and repair of heart valves.

Direct minimally invasive intramyocardial injection of bone marrow-derived AC133+ stem cells in patients with refractory ischemia: preliminary results.

BACKGROUND: Bone marrow-derived stem cells (BMSC) may represent a viable option for patients with myocardial ischemia refractory to conventional treatments. MATERIAL AND METHODS: In 5 patients (4 males and 1 female, mean age 64 +/- 8 years) with untreatable angina pectoris (Canadian Cardiovascular Society Class III/IV), myocardial segments with stress-induced ischemia as assessed by gated single-photon emission computed tomography were injected with 4 to 12 million CD133+ BMSC. Cells were injected into the myocardium (2 anterior, 2 lateral, 1 inferior wall) through minimally invasive approaches (left minithoracotomy [n = 4] and subdiaphragmatic approach [n = 1]). At baseline, at 6 months and at 1 year of follow-up, an exercise test, gated single-photon emission computed tomography (SPECT), 2-D echocardiography and coronary angiography were performed to assess exercise capacity, myocardial perfusion, LV function and coronary anatomy. RESULTS: Intramyocardial injection of autologous CD133+ BMSC cells was safe. No early or long-term complications were observed. After an average of 3.8 weeks from cell inoculation, all patients experienced a significant improvement of CCS class (from 3.8 to 1.8 at 6 months) and serial SPECT documented improvements of rest and stress perfusion in the injected territories at 6 months from operation. In 3 cases, coronary angiography showed an increase in the collateral score of the target areas. Clinical improvements still persist unchanged in 4 out of 5 cases at a mean of 36.5 months postoperatively. CONCLUSIONS: After stand-alone BMSC transplantation for refractory myocardial ischemia, we observed long-term clinical and perfusion improvements in the absence of adverse events.

Tissue factor induction by protease-activated receptor 1 requires intact caveolin-enriched membrane microdomains in human endothelial cells.

BACKGROUND: Protease-activated receptors (PARs) comprise a family of G-protein-coupled receptors with a unique mechanism of proteolytic activation. PARs regulate a broad range of cellular functions and are active in the pathogenesis of disorders characterized by chronic inflammation or activation of the coagulation cascade. Signaling through PAR1 and PAR2 shifts the endothelium towards a prothrombotic phenotype, thereby exacerbating the initial pathophysiologic condition. OBJECTIVES: This study aimed to analyze the localization of PARs in the cell membrane and how their compartmentalization affects tissue factor (TF) in human endothelial cells. METHODS: TF expression was determined by quantitative real-time polymerase chain reaction analysis and by activity assays. The interaction of PARs with caveolin was investigated through: (i) caveolin-1 gene knockdown performed by transfection with specific small interfering RNA (siRNA); (ii) caveolin-enriched membrane microdomain disruption; and (iii) coimmunoprecipitation assay. RESULTS: We have shown that PAR1, but not PAR2, is present in endothelial caveolin-enriched membrane microdomains, where it is bound to caveolin-1, and that these structures must be intact if PAR1-induced signaling is to increase TF activity. Cholesterol depletion of endothelial cells by cholesterol-sequestering agents caused the PAR1 to relocate to high-density membranes, and impaired the induction of TF (P < 0.01) without affecting the PAR2-mediated procoagulant effect. In addition, siRNA directed against caveolin-1 inhibited TF activation by PAR1 (P < 0.01 and P < 0.01, respectively). CONCLUSIONS: PAR1 localization in the caveolin-enriched membrane microdomain, bound to caveolin-1, represents a crucial requirement for TF induction in endothelial cells.

Determinants of late outcome after minimally invasive direct coronary artery bypass.

AIM: Minimally invasive direct coronary artery bypass (MIDCAB) is a reliable method to revascularize the left anterior descending (LAD) coronary artery. However, a more consistent body of knowledge is needed to assess factors influencing long-term outcome. With this study, we retrospectively investigated the long-term determinants of survival and freedom from cardiac morbidity and revascularization in patients who underwent MIDCAB. METHODS: From 1997 to 2005, 109 patients underwent MIDCAB. Seventy-five (68.8%) presented isolated LAD disease and 34 (31.2%) multivessel disease. The first 57 patients (53.2%) in the series underwent early postoperative angiographic reinvestigation. All 109 patients were subsequently followed-up at our outpatient clinic. Follow-up (mean 50.7 months, range 3-93) was completed in 100% of cases. RESULTS: No in-hospital deaths occurred; 2 patients (1.8%) experienced perioperative myocardial infarction. At early postoperative angiographic reinvestigation, the anastomotic perfect patency rate was 54/57 (94.7%); survival was 100% and 95.8% at 1 and 5 years, respectively. Overall freedom from repeated revascularization was 95.3% and 88.3% at 1 and 5 years respectively; freedom from LAD revascularization was 95.3% and 91.6% at 1 and 5 years, respectively; cardiac event-free survival was 95.3% and 80.8% at 1 and 5 years respectively. At multivariable analysis (Cox regression), women were found to have a higher risk of repeated LAD revascularization (hazard ratio [HR] 30.24; P<0.001); female sex and left ventricular dysfunction were the only predictors affecting long-term cardiac outcome (hazard ratio 29.35; P<0.001 and 5.1; P<0.001), respectively. CONCLUSIONS: A key factor in the long-term success of MIDCAB seems to be appropriate patient selection. Special attention should be reserved for female patients, as they appear to have a worse cardiac outcome and a higher probability of repeated revascularization on LAD. MIDCAB may represent a viable option for treating multivessel disease when complete revascularization is unfeasible or a hybrid procedure is envisaged.

Abdominal aortic aneurysm repair in octogenarians: outcomes and predictors.

OBJECTIVES: This study was undertaken to evaluate predictors and outcomes of octogenarians who underwent abdominal aortic aneurysm repair. DESIGN: A prospective observational study. MATERIALS AND METHODS: Between January 1st, 1997 and April 15th, 2005, 31 octogenarians were admitted to our Department with the diagnosis of abdominal aortic aneurysm. Mean follow-up time was 53.7+/-27.2 months. All patients were in good clinical condition and represented a selected healthy group of octogenarians. RESULTS: The overall perioperative (30-days) mortality rate was 3.1%. The total in-hospital morbidity rate was 22.6%. Overall survival estimates at 48 and 96 months were 81+/-8% and 46+/-21%, respectively. The actuarial freedom from aneurysm-related death at 48 and 96 months was 96+/-4% and 96+/-4%, respectively. The actuarial freedom from aneurysm-unrelated death at 48 and 96 months was 84+/-7% and 48+/-21%. Only coronary artery disease was a significant predictor of survival using multivariate stepwise logistic regression analysis. CONCLUSIONS: In this series, AAA surgery was carried out in selected octogenarians without affecting long-term survival.

Long-lasting improvement of myocardial perfusion and chronic refractory angina after autologous intramyocardial PBSC transplantation.

We report the case of a 60-year-old man with patent coronary by-pass grafts on the left anterior descending and circumflex coronary arteries, who experienced recurrent Canadian class IV angina refractory to medical and interventional treatments for a dominant right coronary artery occlusion. He underwent autologous PBSC transplant into the inferior ventricular wall through a minimally invasive approach as a stand-alone therapy, in an attempt to induce therapeutic angiogenesis. Six months after the operation, angina significantly ameliorated; scintigraphy and coronary angiography showed a marked improvement in perfusion of the target injection area. These benefits had persisted at 25 months after stem cell transplant.

Coronary blood flow, metabolism, and function in dysfunctional viable myocardium before and early after surgical revascularisation.

OBJECTIVES: To assess the link between perfusion, metabolism, and function in viable myocardium before and early after surgical revascularisation. DESIGN: Myocardial blood flow (MBF, thermodilution technique), metabolism (lactate, glucose, and free fatty acid extraction and fluxes), and function (transoesophageal echocardiography) were assessed in patients with critical stenosis of the left anterior descending coronary artery (LAD) before and 30 minutes after surgical revascularisation. SETTING: Tertiary cardiac centre. PATIENTS: 23 patients (mean (SEM) age 57 (1.7) years with LAD stenosis: 17 had dysfunctional viable myocardium in the LAD territory, as shown by thallium-201 rest redistribution and dobutamine stress echocardiography (group 1), and six had normally contracting myocardium (group 2). RESULTS: LAD MBF was lower in group 1 than in group 2 (58 (7) v 113 (21) ml/min, p < 0.001) before revascularisation and improved postoperatively in group 1 (129 (133) ml/min, p < 0.001) but not in group 2 (105 (20) ml/min, p = 0.26). Group 1 also had functional improvement in the LAD territory at intraoperative echocardiography (mean regional wall motion score from 2.6 (0.85) to 1.5 (0.98), p < 0.01). Oxidative metabolism, with lactate and free fatty acid extraction, was found preoperatively and postoperatively in both groups; however, lactate and free fatty acid uptake increased after revascularisation only in group 1. CONCLUSIONS: MBF is reduced and oxidative metabolism is preserved at rest in dysfunctional but viable myocardium. Surgical revascularisation yields immediate perfusion and functional improvement, and increases the uptake of lactate and free fatty acids.

Vascular prosthetic graft infection: epidemiology, bacteriology, pathogenesis and treatment.

UNLABELLED: Vascular prosthetic graft infection remains a major surgical challenge. Prevention of risk factors and antibiotic therapy can reduced but not eradicate it. Management of infected vascular grafts depends on several factors, including the location of the infected prosthesis, the extent of infection, and the underlying micro-organism. Classic treatment consists of extra-anatomic bypass grafting. The disappointing results due to the high mortality and amputation rate have kindled interest in alternative approaches, such as in situ reconstruction with antibiotic-bonded prostheses, autogenous veins or arterial allografts. PURPOSE: We focused on the treatment of aortic graft infection by means of both fresh and cryopreserved arterial allograft. Here, the experience of the Italian Collaborative Vascular Homograft Group is reported. METHODS: Between March 1994 and December 2000 seventy-nine patients with aortic graft infection were treated. The results of 68 patients are analysed. Eleven patients were treated with fresh, and 57 with cryopreserved homograft. Emergency surgical procedures were performed in 12 patients (17%). Aortoenteric fistula was diagnosed in 22 patients. The mean interval between the first procedure and the insertion of a homograft for patients with infected aortic graft was 3 years (range 1-15). The mean duration of follow-up was 30 months (range 1-68). Clinical and duplex scanning evaluation were routinely performed. Computer tomography (CT), magnetic resonance (MR), or arteriography were performed on the basis of duplex scanning results. RESULTS: The analysis was performed on 68 cases for which there were sufficient reliable data. Eleven deaths occurred during the early postoperative period (30 days), a mortality rate of 16%. There were also seventeen late deaths, a mortality rate of 25%. Eleven patients had graft occlusion; six cases were successfully treated with thrombectomy. In three cases leg amputation was necessary. The results of fresh and cryopreserved homografts were compared. No significant differences of early postoperative mortality, late mortality, homograft-related mortality, graft failure were observed. The presence of aortoenteric fistula is a negative predicting factor of perioperative early mortality, which causes a rapid decline in the survival curve. Thirty-six months after the surgery the actuarial survival of the patients was 57% and the actuarial patency of the allograft was 41%. CONCLUSION: No significant difference in terms of clinical outcome was observed when using fresh, rather than cryopreserved homografts. The only factor that significantly influenced the survival rate appeared to be the aorto-enteric fistula.

Off-pump redo coronary artery bypass grafting: technical aspects and early results.

BACKGROUND: Redo coronary artery bypass grafting (CABG) represents an high-risk surgical procedure, because of an increased incidence of perioperative death, myocardial infarction and stroke. Theoretically, the avoidance of cardiopulmonary bypass may reduce surgical traumatism and ameliorate early results. MATERIALS AND METHODS: From January 1995 to May 2001, we performed 123 redo CABGs, of which 53 (44%) off-pump. Off-pump procedure represented respectively 90% of redo CABG in the period 2000-2001 versus 30% in the 1995-1999 period. The mean age was 66.4 years, males were 39 (73%). The mean 2D-echo ejection fraction was 56% and in 9 cases (17%) was less than 40%. Three operations (5.6%) were performed on an urgent base. The access was median sternotomy in all cases. The mean number of grafts per patient was 1.9 (1.7 in the period 1995-99 vs. 2.3 in the period 2000-01, p=0.01). In 20 cases (38%) we grafted the circumflex artery branches (19% in the period 1995-99 vs. 55.5% in the period 2000-01, p=0.015). Improvements in surgical techniques were achieved over time. The current operative strategy includes the use of deep traction stitches in the posterior pericardium and wall stabilizers to expose target vessels, coronary intraluminal shunts during construction of the anastomoses and continuous trans-esophageal echocardiographic monitoring. Urgent conversion to on-pump procedure was not required in any case. RESULTS: We recorded no in-hospital death, one perioperative myocardial infarction (1.9%), one fifth postoperative day-stroke (1.9%) and 9 atrial fibrillations (17%). Mediastinal re-exploration for bleeding was performed in no one patient; 13 patients (24.5%) required postoperative blood transfusion. The mean length of postoperative stay was 7.5 days, ranging from 6 to 18 days. CONCLUSIONS: In our experience off-pump redo CABG is a safe and effective alternative to on-pump procedure and now off-pump is our first choice-technique in redo CABG. A complete revascularization is technically feasible with a low incidence of perioperative complications.

Increase of bradykinin in plasma of patients undergoing cardiopulmonary bypass: the importance of lung exclusion.

STUDY OBJECTIVES: Hemodynamic complications including hypotensive episodes are frequently associated with cardiopulmonary bypass (CPB) and can be attributed to a generalized inflammatory response in which bradykinin may be a mediator. The purpose of this study was to determine the plasma levels of bradykinin-(1-9)nonapeptide in patients during CPB and the physiologic elimination of bradykinin by the lungs. DESIGN: Prospective, observational study. SETTING: University hospital, cardiac surgery unit. PATIENTS AND METHODS: Intra-arterial BP was monitored and serial blood samples were obtained from 27 patients undergoing CPB for cardiac surgery. We measured plasma bradykinin and parameters of coagulation, fibrinolysis, complement, contact system, and the cytokine tumor necrosis factor (TNF). RESULTS: Mean arterial pressure fell progressively until the end of CPB (- 18 mm Hg, p = 0.001) but returned to baseline by the end of surgery. The venous bradykinin level, normal in basal conditions (median, 1.90 fmol/mL), was increased (p = 0.001) from 15 min after the beginning of CPB (5.71 fmol/mL) to the end of the operation (7.07 fmol/mL), with a peak at the end of CPB (9.81 fmol/mL; p = 0.0001); it was normal at recovery 24 h later (2.81 fmol/mL). Bradykinin plasma levels fell 60% across the lung when the pulmonary circulation was fully restored while the patients were still receiving CPB. Activated-factor XII, thrombin-antithrombin complexes, prothrombin fragment F1 + 2, plasmin-antiplasmin complexes, C(3)a, and TNF increased significantly after the beginning of the surgical procedure, rising further during CPB, and remained elevated until the end of surgery, but they all returned to normal within 24 h. Changes in plasma bradykinin levels were not correlated with any of the other variables. CONCLUSIONS: During CPB, there is a progressive increase of plasma bradykinin that is at least partially due to reduced catabolism as a consequence of shunting the lungs. The increase in bradykinin may contribute to the fall in BP.

Comparison of endothelium-dependent vasoactivity of internal mammary arteries from hypertensive, hypercholesterolemic, and diabetic patients.

BACKGROUND: Endothelium-dependent relaxation is abnormal in a variety of diseased states. Despite the widespread use of the internal mammary artery (IMA) in coronary artery bypass grafting, there is a lack of comparative studies on IMA endothelial-dependent function in patients with major cardiovascular risk factors. METHODS: An IMA segment from 48 selected patients undergoing coronary artery bypass grafting was harvested intraoperatively and assigned to one of four groups (n = 12): diabetics requiring therapy, hypertensives, hypercholesterolemic, and nondiabetic-normotensive-normocholesterolemic patients. Internal mammary artery specimens were cut into rings and suspended in organ bath chambers, and the isometric tension of vascular tissues was recorded. The IMA rings were (1) precontracted with norepinephrine, and the endothelium-derived relaxation was evaluated by cumulative addition of acetylcholine, (2) contracted with cumulative concentrations of endothelin-1, and (3) contracted with the nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine. Furthermore, the release of prostacyclin by the IMA rings was directly measured during basal tone conditions and at the end of the various pharmacologic interventions. Histology of IMA rings was randomly performed. RESULTS: The results obtained in these experiments showed that IMA rings harvested from hypertensive patients have the greatest impairment of endothelium-dependent response to relaxant and contracting stimuli (p < 0.01 versus nondiabetic-normotensive-normocholesterolemic tissues; p < 0.05 versus hypercholesterolemic and diabetic tissues) and prostacyclin release in normal and stimulated conditions. To a lesser extent, hypercholesterolemic and diabetic tissues show similar depression (diabetic > hypercholesterolemic) both of relaxation and prostacyclin production, with respect to nondiabetic-normotensive-normocholesterolemic specimens (p < 0.05). Histology findings (scanning electron microscopy) did not differ in multiple sections from vessel studies. CONCLUSIONS: Major cardiovascular risk factors affect the endothelium-dependent vasoactive homeostasis of human IMA differently. Depression of relaxation is highest in patients with a history of hypertension. These findings may be pertinent to early and long-term treatment of patients undergoing coronary artery bypass grafting.

[Banks of vascular homografts]. / Banking degli omoinnesti vascolari.

We define as Banking of the tissues all the procedures that include the finding, preparation, conservation and distribution of the homograft. The vascular homografts are taken and put into a solution of transportation at +4 degrees C and kept at this temperature till their arrival at the Bank. The following step is the dissection of the homograft which will have to be performed as quickly as possible at most 24 hours after the taking in conditions of maximum sterility. At the Italian Homograft Bank at Centro Cardiologico, the vascular homografts are kept at +4 degrees C for 96 hours on average with antibiotics. After a phase of sterilization at +4 degrees C the tissue is frozen according to a homogeneous and controlled thermic decrease and stored at -150 degrees C/-180 degrees C in fumes of liquid nitrogen till the moment of their employment allowing a long term conservation. The aim of all these procedures of cryopreservation is to keep the structural and functional integrity of cells and tissues. The thermic decrease of the tissues must occur so that to avoid all the damages of the cellular vitality and functionality and especially of the tissue structure in toto. In order to limitate these events some cryoprotector agents are employed because they reduce the concentration of the solutes, the cellular dehydration, the formation of micro-macro crystals. Another step to establish if the homograft is proper is the study of bacteriological and viral aspects. The viral screenings are performed on the donor's blood and the bacteriological tests are performed on the tissue and on the liquids. For each phase of the banking a series of information about the donor and about the tissues are recorded and filed both on paper and database so that to grant always a right conduct of the material.

[Myocarcial revascularisation without extracorporeal circulation: current indications, surgical technique and results]. / La rivascolarizzazione coronarica senza circolazione extracorporea. Indicazioni attuali, tecnica chirurgica e risultati.

BACKGROUND: This study was undertaken to assess our experience of the evolution, over time, of beating heart surgery in the Cardiologic Center Foundation Monzino. METHODS: From March 1995 to June 2000, 506 patients underwent myocardial revascularization on beating heart: 313 until May 1999, and 193 between June 1999 and June 2000, after the advent of coronary artery stabilizers and shunts, to keep the surgical field bloodless, with minimal motion and continuous myocardial perfusion. Surgical accesss was via a median sternotomy for 408 cases and via a left anterior thoracotomy for 98 cases. RESULTS: The indications by choice increased, from I to II period, from 61% to 83% with special situations in which patients had three-vessel coronary artery disease raised from 33% to 50%, concerning also bypass grafts performed on circumflex artery and right coronary increased. Postoperative mortality in hospital decreased from 1.3% to 0.5% and perioperative IMA (acute myocardial infarction) from 3.8% to 0.5% in patients undertaken to median thoracotomy. Hospital stay decreased from 8 to 7 days about [no significant differences with patients who underwent CPB (cardiopulmonary bypass)]; in patients who underwent to MTS (left anterior minithoracotomy) there was no deaths, IMA decreased from 3.9% to 0% and hospital stay from 6 to 5 days. Grafts patency increased from 92.3% to 100%. CONCLUSIONS: To perform completed revascularisations is possible now even on the beating heart, and also to make precise anastomosis as on pump CABG, in a reproducible and easy way. The beating heart procedure, that is also more economical, might be expanded to all patients, not only high risk patients.

A preoperative index of mortality for patients undergoing surgery of type A aortic dissection.

BACKGROUND: The aim of this study was to identify and stratify the most important preoperative factors for in-hospital death after surgery for type A aortic dissection. METHODS: From January 1985 to June 1998, 108 patients underwent surgery for type A aortic dissection. 89.9% of the patients had an acute type A dissection (AD), whereas 11.1% had a chronic dissection (CD). Cardiac tamponade and shock occurred in 22% and 14.8% of the patients, respectively. The location of the primary intimal tear was in the ascending aorta in 71.2% of the cases, in the arch in 16.6% and in the descending aorta in 7.4%. Univariate and multivariate analyses were conducted to identify non-embolic variables independently correlated to in-hospital death. A predictive model of in-hospital mortality was then constructed by means of a mathematical method with the variables selected from logistic regression analysis. RESULTS: The overall in-hospital mortality rate was 20.3% (22/108 patients), being 9% for CD and 21.6% for AD. Emergent procedures had an in-hospital mortality rate of 47.6%, whereas non-emergent operations had an in-hospital mortality rate of 13.7% (p<0.01). Univariate analysis revealed among 39 preoperative and operative variables, age (years), age >70 years, remote myocardial infarction, cerebrovascular dysfunction, diabetes, preoperative renal failure, shock, cardiopulmonary bypass time (minutes), emergency operation as factors associated to in-hospital death (p<0.05). Stepwise logistic regression analysis selected as independent predicting variables (p<0.05), remote myocardial infarction (p=0.006), preoperative renal failure (p=0.032), shock (p=0.001), age >70 years (p=0.007). Finally, a probability table of death risk was obtained with the logistic regression coefficients. The lower death probability (10.6%) was calculated in absence of risk variables; the higher one in presence of all of them (79.7%). Between these extremes, a total of 64 combinations of death risk were obtained. CONCLUSIONS: Increasing age, shock, coronary artery disease and renal failure are variously associated to a high risk of in-hospital death after surgical correction of type A aortic dissection. This predictive model of death probability allows to collocate preoperatively patients with type A aortic dissection at different levels of risk for in-hospital death.