Angiogenesis by endothelial cell transplantation.

PURPOSE: Myocardial angiogenesis may improve regional perfusion and perhaps function after cardiac injury. We evaluated the effect of endothelial cell transplantation into a myocardial scar on angiogenesis and ventricular function, as an alternative to angiogenic gene or protein therapy. METHODS AND RESULTS: A transmural myocardial scar was created in the left ventricular free wall of rat hearts by cryoinjury. Allogeneic aortic endothelial cells were injected into the scar 2 weeks after cryoinjury. A cluster of transplanted cells was identified at the site of injection 1 day and 1 week after transplantation, but not after 2 weeks. The size of this cluster of transplanted cells decreased as vascular density in the transplanted scar tissue increased with time. Six weeks after transplantation, vascular density was significantly greater in transplanted hearts than in control hearts. Regional blood flow, by microsphere analysis, was greater in the transplanted rats. Systolic and diastolic ventricular function was similar between groups. In a second series of experiments, syngeneic aortic endothelial cells labeled with bromodeoxyuridine were transplanted 2 weeks after cryoinjury. Vascular density in the transplanted scar was greater than in controls. Labeled transplanted endothelial cells were identified forming part of the newly developed blood vessels. No difference in vascular density was found between allogeneic and syngeneic cell transplantation. Vascular endothelial growth factor was not expressed at greater levels in the transplanted cells or the myocardial scar. CONCLUSION: Transplanted endothelial cells stimulated angiogenesis, were incorporated into the new vessels, and increased regional perfusion in myocardial scar tissue, but did not improve global function in this cryoinjury rat model.

Enhanced myocardial angiogenesis by gene transfer with transplanted cells.

UNLABELLED: BACKGROUND The combination of myocardial cell transplantation and angiogenic gene transfer may improve postinfarction left ventricular (LV) perfusion. We evaluated the angiogenic effect of heart cells transfected with vascular endothelial growth factor (VEGF) and transplanted into a myocardial scar. METHODS AND RESULTS: Donor rat heart cells were transfected with plasmids encoding VEGF(165) and green fluorescence protein. Syngeneic adult rats underwent LV cryoinjury to create a transmural scar. Three weeks later, 4x10(6) transfected heart cells (n=14), untransfected heart cells (n=13), or culture medium (n=16) were transplanted into the center of the scar. After 5 weeks, LV function, quantitative histology, and regional blood flow were evaluated. Plates of heart cells transfected with VEGF(165) produced 6.1 times more intracellular VEGF than nontransfected cells. Capillary density (mean+/-SEM) per high-power field in the center of the myocardial scar was 1.1+/-0.02 in control rats, 3.9+/-0.11 in untransfected rats, and 6.3+/-0.11 in transfected rats (P=0.0002). Capillary density in the border zone around the scar was 1.9+/-0.03 in control rats, 6.4+/-0.10 in untransfected rats, and 8.7+/-0.16 in transfected rats (P=0.004). Regional blood flow within the scar was 8.8+/-0.8% of normalized flow in control hearts, 10.4+/-0.7% in hearts transplanted with untransfected cells, but 17.6+/-1.2% in hearts transplanted with transfected cells (P=0.03 versus control, P=0.07 versus nontransfected). There was no difference in LV function attributable to transplantation with transfected cells at the time point studied. CONCLUSIONS: Transplantation of heart cells transfected with VEGF induced greater angiogenesis than transplantation of unmodified cells. Combined gene transfer and cell transplantation strategies may improve postinfarction LV perfusion and function.

Lactate release during reperfusion predicts low cardiac output syndrome after coronary bypass surgery.

BACKGROUND: Cardioplegic arrest induces anaerobic myocardial metabolism with a net production of lactate from glycolysis. However, persistent lactate release during reperfusion suggests a delayed recovery of normal aerobic metabolism and may lead to depressed myocardial function necessitating inotropic or intraaortic balloon pump support (low output syndrome [LOS]). We examined the relation between perioperative myocardial metabolism and postoperative clinical outcomes in patients undergoing isolated coronary artery bypass surgery (CABG). METHODS: We reviewed 623 patients who were enrolled in clinical studies evaluating perioperative myocardial metabolism between 1983 and 1996. Arterial and coronary sinus blood samples were obtained intraoperatively to assess myocardial metabolism. Clinical data regarding patient demographics and postoperative outcomes were prospectively collected and entered into our institutional database. RESULTS: Low output syndrome developed in 36 patients (5.8%). Myocardial lactate release was higher in these patients compared with those who did not develop postoperative LOS. Advanced age and poor preoperative left ventricular function were independent predictors of lactate release during reperfusion. Persistent lactate release after 5 minutes of reperfusion was the only independent predictor of postoperative LOS in this low-risk population. CONCLUSIONS: Persistent lactate release during reperfusion occurs in a significant proportion of low-risk patients undergoing isolated CABG and is an independent predictor of postoperative low cardiac output syndrome. Persistent lactate release during reperfusion suggests a delayed recovery of aerobic myocardial metabolism and may be related to intraoperative misadventure or inadequate myocardial protection. Myocardial lactate release may be useful as an alternative end-point in clinical trials evaluating perioperative myocardial protection.

Stroke during coronary bypass surgery: principal role of cerebral macroemboli.

OBJECTIVE: The purpose of this study was to gain insight into the etiology of stroke during coronary bypass surgery. METHODS: Retrospective review of prospectively gathered data on 6682 consecutive coronary bypass patients. Patients undergoing simultaneous procedures, including carotid endarterectomy, were excluded. We performed a systematic chart review of all patients who suffered a perioperative stroke. Predictors of stroke were determined with stepwise logistic regression analysis. RESULTS: The prevalence of stroke was 1.5% (n=98). Stroke patients had significantly increased intensive care unit and hospital length of stays, as well as increased mortality when compared to patients without stroke (all P< 0.001). Independent predictors of stroke were (in decreasing order of magnitude): age >70 years, left ventricular ejection fraction <40%, previous stroke or transient ischemic attack, normothermic cardiopulmonary bypass, diabetes, and peripheral vascular disease. Chart review revealed that the probable cause of stroke was macroemboli, likely from ascending aorta atherosclerosis, in 37% of patients and unknown in 38% of patients. Computerized tomography (CT) scans were obtained in 79 patients (81%). Lesions detected by CT were consistent with a macroembolic etiology: nearly all lesions were ischemic in nature and located in the distribution of major cerebral arteries, particularly the middle cerebral artery. CONCLUSIONS: Stroke is a devastating complication of coronary bypass surgery. Our multivariable risk factors for stroke, chart review, and CT findings all suggest that macroemboli, presumably from the ascending aorta, are the predominant cause of stroke during coronary bypass surgery. Future studies should be directed at minimizing the risk of embolization during cardiac surgery.

The fate of a tissue-engineered cardiac graft in the right ventricular outflow tract of the rat.

OBJECTIVE: The synthetic materials currently available for the repair of cardiac defects are nonviable, do not grow as the child develops, and do not contract synchronously with the heart. We developed a beating patch by seeding fetal cardiomyocytes in a biodegradable scaffold in vitro. The seeded patches survived in the right ventricular outflow tract of adult rats. METHODS: Cultured fetal or adult rat heart cells (1 x 10(6) cells) were seeded into a gelatin sponge (15 x 15 x 1 mm), and the cell number was expanded in culture for 1 or 3 weeks, respectively. The free wall of the right ventricular outflow tract in syngeneic adult rats was resected and repaired with either unseeded patches or patches seeded with either fetal or adult cardiomyocytes (n = 10 for each group). The patches were examined histologically over a 12-week period. RESULTS: A significant inflammatory reaction was noted in the patch at 4 weeks as the scaffold dissolved. At 12 weeks, the gelatin scaffold had completely dissolved. Both types of the seeded cells were detected in the patch with 5-bromo-2'-deoxyuridine staining, and they maintained their continuity. Unseeded patches had an ingrowth of fibrous tissue. The patches became thinner between the fourth and the twelfth weeks in unseeded (P =.003), fetal (P =.0001), and adult (P =.07) cardiomyocyte groups as the scaffold dissolved. The control patch, but not the cell-seeded patches, was thinner than the normal right ventricular outflow tract. The endocardial surface area of each patch was covered with endothelial cells identified by factor VIII staining. CONCLUSIONS: A gelatin patch was used to replace the right ventricular outflow tract in syngeneic rats. The seeded cells survived in the right ventricular outflow tract after the scaffold dissolved 12 weeks after implantation. In addition, the unseeded patches encouraged the ingrowth of fibrous tissue as the scaffold dissolved and the patches remained completely endothelialized.

The effect of insulin cardioplegia on atrial fibrillation after high-risk coronary bypass surgery: a double-blinded, randomized, controlled trial.

UNLABELLED: Atrial fibrillation after coronary bypass (CABG) surgery is an important cause of morbidity and increased resource utilization. Insulin-enhanced cardioplegia may reduce postoperative arrhythmias by improving aerobic myocardial metabolism and mitigating the deleterious effects of ischemia. We performed a double-blinded, randomized, controlled clinical trial to determine if insulin-enhanced cardioplegia decreases the risk of post-CABG atrial fibrillation in a high-risk patient population. We randomized 501 patients undergoing urgent CABG to receive insulin-enhanced (Humulin R 10 IU/L, Insulin group, n = 243) or standard (Control group, n = 258) blood cardioplegia during cardiopulmonary bypass. Patients were monitored by using continuous electrocardiography for a minimum of 3 days postoperatively. All standard cardiac medications, including beta-adrenergic blockers, were continued postoperatively. Insulin-enhanced cardioplegia did not result in a significant reduction in postoperative atrial fibrillation. Furthermore, we failed to detect a difference in the incidence of conduction defects, ventricular tachycardia, or pacemaker requirements between insulin and placebo patients. Atrial fibrillation was the most common arrhythmia, occurring in 31% of all patients. Independent predictors of atrial fibrillation were elderly age, preoperative atrial fibrillation, and renal insufficiency. Right bundle branch block was the most common conduction abnormality. Predictors of right bundle branch block were elderly age, female sex, and circumflex coronary artery disease. The incidence of postoperative ventricular tachycardia, left bundle branch block, and permanent pacemaker requirement was small. We conclude that insulin-enhanced cardioplegia does not reduce the incidence of postoperative atrial fibrillation in high-risk CABG patients. IMPLICATIONS: We conducted a double-blinded, randomized, placebo-controlled trial of insulin-enhanced cardioplegia in 501 patients undergoing urgent coronary bypass surgery. Insulin did not decrease the incidence of postoperative atrial fibrillation when compared with placebo. We also failed to demonstrate a difference in the incidence of other postoperative arrhythmias between the two groups of patients.

Neuropsychologic impairment after coronary bypass surgery: effect of gaseous microemboli during perfusionist interventions.

OBJECTIVE: Neuropsychologic impairment is a common complication of coronary bypass surgery. Cerebral microemboli during cardiopulmonary bypass are the principal cause of cognitive deficits after coronary bypass grafting. We have previously demonstrated that the majority of cerebral emboli occur during perfusionist interventions (ie, during the injection of air into the venous side of the cardiopulmonary bypass circuit). The purpose of this study was to determine whether an increase in perfusionist interventions is associated with an increased risk of postoperative cognitive impairment. METHODS: Patients undergoing elective coronary artery bypass grafting (n = 83) underwent a battery of neuropsychologic tests preoperatively and 3 months postoperatively. Patients were divided into 2 groups according to the median value of perfusionist interventions during cardiopulmonary bypass. Group 1 patients (n = 42) had fewer than 10 perfusionist interventions, and group 2 patients (n = 41) had 10 or more interventions. RESULTS: The 2 groups of patients were similar for all preoperative, intraoperative, and postoperative variables, with the exception of longer cardiopulmonary bypass times in group 2 patients (P <.001). Group 2 patients had lower mean scores on 9 of 10 neuropsychologic tests, with 3 (Rey Auditory Verbal Learning, Digit Span, and Visual Span) being statistically significant. Group 2 patients had worse cognitive test scores, even when controlling for increased bypass times. Group 2 patients had a nonsignificant trend toward an increased prevalence of neuropsychologic impairment 3 months postoperatively. CONCLUSIONS: Introduction of air into the cardiopulmonary bypass circuit by perfusionists, resulting in cerebral microembolization, may contribute to postoperative cognitive impairment.

Effects of metabolic stimulation on cardiac allograft recovery.

BACKGROUND: We previously demonstrated that continuous perfusion of cardiac allografts during hypothermic storage with donor blood harvested at the time of organ retrieval improves myocardial recovery after transplantation. However, myocardial metabolism and function remain depressed compared to base line values. This study evaluated the use of a continuous infusion of donor blood enhanced with insulin to augment aerobic myocardial metabolism during and after hypothermic storage. METHODS: Yorkshire pigs (45 to 50 kg) were used to perform 14 orthotopic cardiac transplants using either continuous perfusion with donor blood (blood group, n = 7) or perfusion with donor blood enhanced with 10 IU/L insulin (insulin group, n = 7). After heparinization, hypothermic (4 degrees C) cardioplegic arrest, and donor heart extraction, donor blood (2,844 +/- 210 mL) was harvested in both groups and perfused at room temperature (20 degrees C) at a pressure of 60 mm Hg for 3 hours. Blood cardioplegia was delivered after each anastomosis in both groups and arterial and coronary sinus blood samples were obtained to examine myocardial metabolism. A Millar micromanometer was used to measure left ventricular developed pressure and the rate-pressure product at varying preloads. RESULTS: There were no differences in either myocardial lactate or acid release between the two groups. Hearts in the insulin group displayed higher myocardial oxygen extraction than those in the blood group. The recovery of developed pressure was higher in the insulin group compared to the blood group (91% +/- 19% vs 73% +/- 2%, p = 0.04). CONCLUSIONS: In this model, continuous perfusion of cardiac allografts with donor blood and insulin preserves myocardial metabolism during hypothermic storage and improves metabolic and functional recovery after orthotopic cardiac transplantation.

Reoperative coronary bypass surgery: effect of patent grafts and retrograde cardioplegia.

OBJECTIVE: To determine the effects of patent or diseased aorta-coronary bypass grafts and retrograde cardioplegia on mortality during reoperative coronary bypass surgery. METHODS: We conducted a retrospective review of prospectively gathered data, supplemented by systematic chart review, of all patients (n = 744) undergoing reoperative coronary bypass surgery at our institution between 1990 and 1997. Independent predictors of survival were determined by stepwise logistic regression analysis. RESULTS: At least one patent or stenosed graft to the left anterior descending artery was present in 50% of patients, to the circumflex territory in 27% of patients, and to the right coronary artery territory in 33% of patients. The previous left anterior descending graft was a saphenous vein in 82% and a left internal thoracic artery in 18% of patients. In-hospital mortality occurred in 42 (5.6%) patients. Patent or diseased grafts of any coronary artery territory did not significantly increase the risk of mortality. Retrograde cardioplegia use increased in more recent years, was more frequent in patients with stenosed grafts, and was associated with improved survival. Independent predictors of mortality were as follows (with odds ratios and 95% confidence intervals in parentheses): failure to use retrograde cardioplegia (odds ratio 2.81; 1.28-6.20), New York Heart Association class (odds ratio 2.69; 1.25-5.81), peripheral vascular disease (odds ratio 2.60; 1.25-5.41), and left ventricular grade (2.07; 1.31-3.27). CONCLUSIONS: In this series, patent or stenosed grafts were not associated with an increased risk of mortality during reoperative coronary bypass surgery, possibly because of increased use of retrograde cardioplegia in this patient group. We strongly recommend the routine use of retrograde cardioplegia during redo coronary bypass surgery.

Transplantation of cryopreserved cardiomyocytes.

BACKGROUND: The present study examined the survival and rate of contraction of (1) cardiomyocytes cultured from cryopreserved fetal rat myocardium and (2) cryopreserved cultured cardiomyocytes. In addition, the effects of transplantation of cryopreserved fetal cardiomyocytes were evaluated. METHODS: Segments of fetal rat myocardial tissue (0.2, 2.0, and 6.0 mm(3) mince size) and cultured cardiomyocytes were cryopreserved in liquid nitrogen for 1, 2, and 4 weeks. After cryopreservation, the tissue samples and cultured cardiomyocytes were thawed at 37 degrees C and cultured, and cell proliferation and rate of contraction were determined. Cultured cryopreserved (n = 5) and noncryopreserved (control, n = 5) fetal cardiomyocytes were transplanted into the subcutaneous tissue and into a transmural left ventricular free wall scar of Sprague-Dawley rats (n = 3). The survival and rate of contraction of these transplanted cells were also examined. RESULTS: Cryopreservation of cultured fetal cardiomyocytes resulted in viable and functional cardiomyocytes although the cell number and percentage of beating cells were diminished. Survival of cardiomyocytes isolated from cryopreserved fetal myocardium was a function of tissue size before cryopreservation; the lowest survival was recorded in tissues with the largest mince size (6.0 mm(3)). The subcutaneous transplants contracted spontaneously and regularly with an idioventricular rhythm. In addition, the transplanted cardiomyocytes were elongated and formed a myocardium-like pattern with blood vessels present within the contractile tissue. In the transmural left ventricular scar, both control and experimental fetal cardiomyocyte transplants formed myocardium-like tissue. CONCLUSIONS: The present study uncovers the following key observations: (1) cryopreservation of fetal cardiomyocytes and cardiomyocytes isolated from cryopreserved myocardial tissue results in viable and functional cells, (2) cryopreserved fetal cardiomyocytes can be successfully transplanted into subcutaneous and myocardial scar tissue, and (3) improvements in cryopreservation techniques are required to augment the rates of cardiomyocyte survival observed in the study.

Optimal time for cardiomyocyte transplantation to maximize myocardial function after left ventricular injury.

BACKGROUND: This study was designed to determine the optimal time for cell transplantation after myocardial injury. METHODS: The left ventricular free wall of adult rat hearts was cryoinjured and the animals were sacrificed at 0, 1, 2, 4, and 8 weeks for histologic studies. Fetal rat cardiomyocytes (transplant) or culture medium (control) were transplanted immediately (n = 8), 2 weeks (n = 8), and 4 weeks (n = 12) after cryoinjury. At 8 weeks, rat heart function, planimetry, and histologic studies were performed. RESULTS: Cryoinjury produced a transmural injury. The inflammatory reaction was greatest during the first week but subsided during the second week after cryoinjury. Scar size expanded (p < 0.01) at 4 and 8 weeks. Cardiomyocytes transplanted immediately after cryoinjury were not found 8 weeks after cryoinjury. Scar size and myocardial function were similar to the control hearts. Cardiomyocytes transplanted at 2 and 4 weeks formed cardiac tissue within the scar, limited (p < 0.01) scar expansion, and had better (p < 0.001) heart function than the control groups. Developed pressure was greater (p < 0.01) in the hearts with transplanted cells at 2 weeks than at 4 weeks. CONCLUSIONS: Cardiomyocyte transplantation was most successful after the inflammatory reaction resolved but before scar expansion.

Heart cell transplantation improves heart function in dilated cardiomyopathic hamsters.

BACKGROUND: Little is known about the effect of heart cell transplantation into the dilated cardiomyopathic myocardium. This study was designed to evaluate the effect of heart cell transplantation into dilated cardiomyopathic hamsters. METHODS AND RESULTS: Ventricular heart cells were isolated from 4-week-old BIO 53. 58 hamsters and cultured for 2 weeks before transplantation. The cells were labeled with bromodeoxyuridine (BrdU) before transplantation for identification. Adult hamsters (17 weeks old) were used as recipients. Heart cells (4 x 10(6) cells) or culture medium was transplanted into the left ventricular free wall (transplantation and control groups, respectively, n=12 each). Sham-operated hamsters (n=12) underwent the surgery but not the transplantation. Cyclosporine A was administered subcutaneously to all hamsters daily after the operation. Four weeks after the transplantation, heart function was evaluated with the use of a Langendorff preparation. Histology showed severe focal myocardial necrosis in all groups. BrdU-stained tissue was found at the cell transplantation sites. The transplanted hearts had greater (P:<0. 001) developed pressures at all balloon volumes and improved dP/dt (transplantation 915+/-253 versus control 453+/-120 and sham 530+/-187 mm Hg/s, P:<0.001, balloon volume of 15 microL). No differences in ventricular function were found between control and sham-operated hamsters. CONCLUSIONS: The transplanted ventricular heart cells formed cardiac-like tissue in cardiomyopathic myocardium and improved its contractile function.

Autologous smooth muscle cell transplantation improved heart function in dilated cardiomyopathy.

BACKGROUND: Transplantation of myocytes into scarred myocardium has been shown to inhibit ventricular remodeling and maintain myocardial contractility. However, the effect of cell transplantation on hearts with global rather than regional dysfunction is unknown. Therefore, we evaluated the effect of transplantation of autologous smooth muscle cells on the morphometry and function of dilated cardiomyopathic hearts. METHODS: Smooth muscle cells were isolated from the ductus deferens of 13-week-old BIO 53.58 hamsters with dilated cardiomyopathy, and cultured for 4 weeks before transplantation. Smooth muscle cells (4 x 10(6) cells) or culture medium were injected into 17-week-old animals in the transplantation and control groups (n = 12 each), respectively. Prelabeling of the smooth muscle cells with 5-bromo-2'-deoxyuridine was performed before transplantation in a group of transplanted hamsters. Another group (sham, n = 12) underwent the operation but did not receive an injection either of smooth muscle cells or of culture medium. Four weeks after transplantation, heart function was evaluated in a Langendorff preparation. RESULTS: Musclelike tissue, labeled with 5-bromo-2'-deoxyuridine, was found at the site of transplantation in the cell-transplanted animals. The cell-transplanted hearts were smaller (p < 0.001), and had greater developed pressures and maximum rate of increase of left ventricular pressure (both p < 0.001) than control and sham hearts. Control hamsters injected with culture medium did not differ from sham-operated animals. CONCLUSIONS: Transplantation of autologous smooth muscle cells prevented cardiac dilatation and improved ventricular function in hamsters with dilated cardiomyopathy.

The changing pattern of reoperative coronary surgery: trends in 1230 consecutive reoperations.

OBJECTIVE: We noted an increasing risk profile of patients undergoing reoperative coronary surgery. We evaluated the risk compared with primary procedures, our results over a 16-year span, and the predictors of hospital outcomes after redo surgery. METHODS: We analyzed 20,614 patients undergoing isolated coronary surgery at our institution from 1982 to 1997. Of these, 1230 (6.0%) were undergoing reoperation. Independent predictors of outcomes were identified by multivariable regression. RESULTS: The prevalence of reoperation peaked in 1994 at 8.2%. Patients undergoing reoperation were more likely to be male, to have left ventricular dysfunction and worse symptoms, and to require an urgent operation than patients undergoing a primary operation (P <.0001). Perioperative myocardial infarctions (3.7% vs 7.4%), low-output syndrome (9.0% vs 24.0%), and death (2.4% vs 6.8%) were more common in patients undergoing reoperation (all P <.0001). Over the years, the risk profile of patients undergoing reoperation increased. Age, left ventricular dysfunction, severity of symptoms, extent of coronary artery disease, left main stenosis, and requirement for urgent or emergency operations increased with time (P <.05). However, mortality, myocardial infarction, and low-output syndrome have remained constant. The independent predictors of mortality after reoperative surgery were increased age, greater Canadian Cardiovascular Society symptom class, earlier year of operation, and greater left ventricular dysfunction. After 1990, analysis of an expanded data set also identified peripheral vascular disease and failure to use retrograde cardioplegia as predictors of mortality. CONCLUSIONS: Improving results of reoperative surgery have been offset by an increasing patient risk profile. Meticulous operative technique and retrograde cardioplegia may permit good results in these high-risk patients.

Insulin cardioplegia for elective coronary bypass surgery.

BACKGROUND: Improved methods of myocardial preservation are required to reduce the morbidity and mortality of coronary bypass surgery for high-risk subgroups. Metabolic stimulation with insulin, glucose solutions, or both has been proposed as a method to preserve the ischemic myocardium. We performed a prospective, double-blind, randomized trial to evaluate the effects of insulin and glucose as cardioplegic additives when used as part of a tepid continuous blood cardioplegic strategy. METHODS: We randomized 56 male patients undergoing elective isolated coronary bypass surgery to 1 of 4 cardioplegic groups containing either 42 or 84 mmol/L glucose with or without 10 IU/L of insulin. Perioperative assessments of myocardial metabolism and left ventricular function were performed. RESULTS: Insulin-enhanced cardioplegia was associated with beneficial effects on both myocardial metabolic and functional recovery after cardioplegic arrest. Insulin's effect was independent of the ambient glucose concentration. CONCLUSIONS: Cardioplegic formulations containing a 42 mmol/L concentration of glucose and a 10 IU/L concentration of insulin provide significant benefit to patients undergoing isolated coronary bypass surgery. The clinical effect of these formulations will need to be assessed in high-risk subgroups of patients, such as those with unstable angina, recent myocardial infarction, or poor left ventricular function.

Construction of a bioengineered cardiac graft.

OBJECTIVES: Currently available graft materials for repair of congenital heart defects cause significant morbidity and mortality because of their lack of growth potential. An autologous cell-seeded graft may improve patient outcomes. We report our initial experience with the construction of a biodegradable graft seeded with cultured rat or human cells and identify their 3-dimensional growth characteristics. METHODS: Fetal rat ventricular cardiomyocytes, stomach smooth muscle cells, skin fibroblasts, and adult human atrial and ventricular cardiomyocytes were isolated and cultured in vitro. These cells were injected into or laid onto biodegradable gelatin meshes, and their rate of proliferation and spatial location within the mesh was evaluated by using a cell counter and histologic analysis. RESULTS: Rat cardiomyocytes, smooth muscle cells, and fibroblasts demonstrated steady proliferation over 3 to 4 weeks. The gelatin mesh was slowly degraded, but this process was most rapid after seeding with fibroblasts. Human atrial cardiomyocytes proliferated within the gelatin meshes but at a slower rate than that of fetal rat cardiomyocytes. Human ventricular cardiomyocytes survived within the gelatin mesh matrix but did not increase in number during the 2-week duration of evaluation. Grafts seeded with rat ventricular cells exhibited spontaneous rhythmic contractility. All cell types preferentially migrated to the uppermost surface of each graft and formed a 300- to 500-microm thick layer. CONCLUSIONS: Fetal rat ventricular cardiomyocytes, gastric smooth muscle cells, skin fibroblasts, and adult human atrial cardiomyocytes can grow in a 3-dimensional pattern within a biodegradable gelatin mesh. Similar autologous cell-seeded constructs may eventually be applied to repair congenital heart defects.