Interim results of coronary artery bypass grafting with concurrent stem cell transplantation for chronic heart failure in coronary heart disease
The decline in the number of surviving cardiomyocytes after severe myocardial infarction in coronary artery disease with hypofunction and the subsequent onset of chronic heart failure are end-stage manifestations with severe disease and poor prognosis. Although medical and surgical treatments can improve coronary blood supply and salvage ischemic myocardium, there is still no solution for necrotic myocardium [1] [2]. Since conventional treatments cannot regenerate and repair diseased necrotic myocardial cells, it is difficult to fundamentally reverse the progression of heart failure. Stem cells have multidirectional differentiation potential, and stem cell transplantation technology may become an effective measure to treat myocardial ischemic necrosis [3]. Several clinical studies on cell regeneration for repairing damaged myocardium have been conducted worldwide in recent years, and some of them have confirmed the safety and efficacy of cell transplantation for acute heart attack [4]. We selected patients with old coronary infarction with cardiac insufficiency requiring surgical treatment, applied coronary artery bypass grafting with simultaneous autologous bone marrow single nucleus cell transplantation, evaluated the adverse events of autologous bone marrow single nucleus cell transplantation, and followed up the survival time and long-term survival quality of patients.
Materials and Methods
Nineteen patients with old coronary infarction voluntarily underwent coronary artery bypass grafting with simultaneous autologous bone marrow single nucleus cell transplantation and signed an informed consent form. There were 17 male and 2 female patients. Their ages ranged from 40 to 71 years old, with a mean age of 57±9 years. The preoperative diagnosis was coronary heart disease, old infarction with left ventricular insufficiency, preoperative combined hypertension in 6 cases, hyperlipidemia in 12 cases, and diabetes mellitus in 3 cases. Coronary angiography showed that all coronary lesions were 3-branch lesions, 6 cases combined with ventricular wall aneurysm, and 2 cases combined with moderate mitral regurgitation or above. The preoperative coronary angiograms were reviewed by two senior cardiac surgeons and met the indications for category I of the “New U.S. 2004 Revised Guidelines for Coronary Artery Bypass Graft Surgery”, with no indications for heart transplantation and no contraindications to surgery. The patient had a large infarcted myocardium on preoperative nuclear evaluation. The preoperative echocardiogram showed a left ventricular ejection fraction of 25% to 45%, with a mean of 36±5.6% (two-dimensional ultrasound Simpson’s method); the left ventricular end-diastolic diameter ranged from 46 to 80 mm, with a mean of 60.8±7.8 mm.
All 19 patients underwent coronary artery bypass grafting and autologous bone marrow cell stem cell transplantation in the operating room under general anesthesia with hypothermic extracorporeal circulation. After general anesthesia in the operating room, the anterior superior iliac crest was sterilely punctured, about 60 ml of bone marrow blood was extracted, and 10 ml of bone marrow single nucleated cells suspension was obtained by density gradient centrifugation. 10 ml of the successfully obtained bone marrow single nucleated cells suspension was drawn onto the operating table with a 10 ml syringe. Transanastomotic endovascular grafts were performed in the ratio of 40% for the anterior descending branch, 30% for the right coronary artery, and 30% for the left coronary artery. The specific operation is as follows: inject 4 ml of cell suspension through the left internal mammary artery to the anastomosis of the anterior descending branch, inject slowly for more than 1 minute, and then briefly open the internal mammary artery to vent, block the blood flow of the internal mammary artery again, knot the suture of the anastomosis, and keep no blood flow in the anterior descending branch for 5 minutes; inject 3 ml of cell suspension from the proximal end of the right coronary bridge vessel, inject slowly for more than 1 minute, and finish with 1 ml of The residual cellular fluid in the bridge vessel was pushed into the myocardium with physiological saline, and the proximal end was clamped to maintain no blood flow for 5 minutes; the cell transplantation in the left coronary vessel was continued in the same way as the cell injection in the right coronary bridge vessel, with a slow injection of 3 ml of cell suspension, and the proximal end was clamped to maintain no blood flow for 5 minutes. After completing all cell transplantation operations, the aortic blocking clamp can be opened and proximal anastomosis anastomosis is performed to complete the CABG procedure. The distal anastomosis is completed under cardiac arrest, and the proximal anastomosis is completed by injecting stem cell suspension via the bridge vessel and the anastomosis. If other procedures such as mitral valvuloplasty or ventricular wall tumor resection were combined at the same time, the simultaneous procedures were performed first and cell transplantation was performed last.
All patients completed clinical assessment of cardiac function and angina pectoris grading. Coronary angiography to evaluate coronary artery lesions, nuclear examination to evaluate surviving myocardium, echocardiography to evaluate left ventricular function, and Holter to evaluate preoperative heart rhythm were also completed within 2 weeks before surgery.
Postoperative repeat echocardiography was used as a follow-up evaluation. The HP SONOS 5500 color echocardiograph with a probe frequency of 2.5/2.0 MHz was used for echocardiography, and the left ventricular long-axis views, mitral papillary muscle horizontal views, apical left ventricular four-chamber views, five-chamber views and two-chamber views were taken, and the endocardium of the left ventricle in end-diastole and isovolumic systole were traced on the apical four-chamber and apical two-chamber maps, respectively, and entered into the automatic analysis system, and the endocardium was automatically derived according to the biplane Simpson ‘s method to automatically calculate the left ventricular ejection fraction.
Follow-up evaluations were performed to assess the improvement of cardiac function, improvement of angina pectoris, the presence of recurrent heart failure episodes, the occurrence of malignant arrhythmias, and the occurrence of MACCE events. This study protocol was approved by the ethics committee and agreed to proceed. The data obtained were analyzed by applying SPSS10.0 statistical software to the collected data. The measurement data were expressed in the form of mean ± standard deviation. Direct comparisons of preoperative data information and postoperative outcomes in this group were made, and the metric data were analyzed by Student t-test. The graded count data were analyzed by nonparametric test. p < 0.05 was considered a statistically significant difference.
Results
The number of bone marrow single nucleated cells obtained in 19 patients ranged from 1.8 to 12×107, with a mean of 8.23±4.03×107, and the percentage of surviving cells was >99%. Microbiological assay, cell culture were all sterile growth. Bone marrow cells were cultured in vitro, and primary cells gradually formed clone-like growth at 10 days of culture, and then passed on to form a generation of cells after 12 to 14 days.
Nineteen patients underwent coronary artery bypass grafting and autologous bone marrow single nucleated cell transplantation, including 6 cases of ventricular wall aneurysm resection and 2 cases of mitral valvuloplasty at the same time. The mean number of bypass branches was 4.3±0.8. The average extracorporeal circulation time was 126±38 minutes and the average block time was 73±19 minutes. IABP was implanted in 4 patients during surgery, and all of them were discharged successfully; 7 patients were implanted with left heart assist, and BVS5000 left heart assist was applied, among which 1 patient had a sudden cerebral embolism on the third day of left heart assist, and the stroke eventually led to the patient’s death.
The duration of postoperative ventilator assistance was less than 24 hours in 12 patients, 24 to 72 hours in 4 patients, and more than 72 hours in 3 patients; the duration of postoperative ICU stay was within 3 days in 5 patients, 3 to 7 days in 8 patients, and more than 7 days in 6 patients. 19 patients had no myocardial infarction in the early postoperative period and no new Q waves on the ECG. The mean value of CK before surgery was 79.2±41.3 IU/L, and the mean value of CK after surgery was 449.1±430.1 IU/L. The mean value of CK-MB before surgery was 12.6±3.9 IU/L, and the mean value of CK-MB after surgery was 29.2±29.3 IU/L. MB mean value was 29.2±24.8 IU/L after surgery.
There was no hepatic failure in the whole group. The mean preoperative GOT was 37±19 IU/L and the mean preoperative GPT was 28±11 IU/L; the mean postoperative GOT was 53±45 IU/L and the mean postoperative GPT was 49±28 IU/L. No renal failure occurred in the whole group. The average preoperative blood creatinine was 88±17 mmol/L, and the average postoperative blood creatinine was 118±40 mmol/L. No pulmonary embolism occurred in the whole group of patients.
No malignant ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation) occurred in all patients during the postoperative period in the ICU.
All 18 surviving patients completed more than 1 year of clinical follow-up observation, and there were no deaths during the follow-up period, which ranged from 12 to 40 months with a mean of 26.3±9.0 months. In the postoperative follow-up examination with the application of echocardiography, the left ventricular ejection fraction (LVEF) increased from 36.0±5.6% to 42.6±7.0% before surgery, with a statistically significant P=0.0044 by statistical test; the left ventricular end-diastolic diameter (LVEDD) decreased from 60.8±7.6mm to 57.7±9.6mm before surgery, with a statistically significant P= 0.3964, which was not statistically significant.
After surgery, 4 patients had another heart failure episode, which was relieved by treatment, and their cardiac function was graded from 1 to 3, with a mean of 1.9±0.6. After surgery, angina symptoms disappeared in 5 patients and were significantly relieved in 11 patients (Canadian angina classification of grade 1); 2 patients had another chest tightness episode after 1 year of follow-up, and their symptoms were relieved by increasing the dose of nitrate. The non-parametric test analyzed the improvement of cardiac function grading before and after surgery, P<0.001, which was statistically significant; the non-parametric test analyzed the improvement of angina grading before and after surgery, P<0.001, which was statistically significant.
The whole group of 18 patients had no postoperative infarction and did not receive re-vascularization treatment. No neurological accidents such as cerebral embolism and cerebral hemorrhage occurred during the follow-up period in the whole group. 1 patient developed symptomatic arrhythmias, Holter showed: 4163 ventricular premature, 164 paired, 249 ventricular tachycardia, 51 per 1000 of ventricular premature occurrence, 6 supraventricular tachycardia and 253 supraventricular premature. This patient was discharged without regular antiarrhythmic therapy and still had a left ventricular end-diastolic diameter of 75 mm on ultrasound at 26 months postoperatively. this patient was found to have a peripheral type tumor in the lung at 16 months postoperatively and underwent a wedge resection of the lung lobes, which was pathologically confirmed as adenocarcinoma of the lung, and is still alive at 36 months of follow-up.
Discussion
Cell transplantation for repair of infarcted myocardium has been the focus of research in recent years by scholars in China and abroad. The present study was conducted to observe the clinical safety of coronary artery bypass grafting with simultaneous autologous bone marrow single nucleus cell transplantation for heart failure after myocardial infarction and to preliminarily analyze its clinical efficacy. Cell transplantation via intracoronary injection of the opened coronary artery is the most frequently used cell transplantation method in clinical studies [5]. The transplanted cells can be infused into the target area through the bridge vessel, and the cells are uniformly distributed and form an effective treatment locally in the coronary microvasculature of the injured or infarcted area. However, during treatment, the attached graft cells are washed away by intracoronary blood flow, and the myocardial survival of graft cells is low, with different literature reporting that only 1% to 3% of the cells remain in the infarct area [6]. In our study, the cell suspension was slowly injected via the bridge vessel under cardiac arrest. In the state of arrest, there is no blood flow in the coronary arteries, and the cells have a long contact time with the endothelium and an increased adhesion capacity; at the same time, in the state of arrest, the capillaries are in a diastolic state without blood flow pressure, and the vascular permeability is strong, so the proportion of transplanted cells adhering to the endothelium entering the myocardial tissue through the vessel wall is greater.
Ventricular remodeling and pump failure secondary to myocardial infarction in coronary artery disease is a thorny problem in the treatment of coronary artery disease. Hemodialysis alone only addresses myocardial tonus and hibernating myocardium, whereas extensive degenerative, necrotic and fibrotic scar tissue is ineffective for hemodialysis. The literature reports that patients with old infarction with left ventricular hypoperfusion treated with CABG alone have a 1-year survival rate of 87% and a 3-year survival rate of 80% [2]. Stem cell transplantation can improve LVEF by 5% to 10% in patients with severe cardiac insufficiency in old infarction with coronary artery disease [5]. The mean left ventricular ejection fraction in our patients improved from 36.0% to 42.6%, LVEF increased by 18.3% compared with the preoperative level, and the cardiac function class decreased from 2.9±0.8 to 1.6±0.7. This result is due to the adulteration of the improvement of left ventricular function by CABG, thus it does not confirm the effect of stem cell transplantation on improving cardiac function in such patients, and must be The efficacy of stem cell transplantation must be evaluated in a rigorous randomized controlled study.
The safety of cell transplantation has always been a matter of concern. The safety of cell transplantation has always been a concern for scholars, as different routes of transplantation and types of transplanted cells may cause different complications, with particular attention to malignant ventricular arrhythmias after transplantation. In this study, we focused on the occurrence of arrhythmias in patients. One patient developed symptomatic arrhythmias after cell transplantation, but no pharmacological treatment for the arrhythmias was administered; Holter showed frequent premature ventricular contractions. This patient had a preoperative left ventricular end-diastolic diameter of 80 mm and Holter: frequent premature ventricular contractions. The patient’s left ventricular end-diastolic diameter was still 75 mm on ultrasound review 26 months after surgery, and the analysis of frequent ventricular premature contractions may be related to an enlarged heart with low cardiac function. Arrhythmias associated with stem cell transplantation are reported in the literature to occur mainly after intracardiac injection transplantation of skeletal muscle myogenic cells [7] [8]. Some scholars believe that arrhythmias occur due to the inability of skeletal muscle myogenic cells to form intercellular gap junctions and conduct electrical activity at the same rate as cells in situ, resulting in dyschronism, and may also be related to myogenic cells and intracardiac injection transplantation [9]. However, the pathogenesis may be multifaceted, with differences in ion channels between myogenic and cardiac myocytes, and the release of inflammatory mediators local to the injection. In contrast, no significant arrhythmias were found in studies using both bone marrow cells and peripheral blood precursor cells.
The literature reports that acute myocardial ischemia and subacute microinfarction were found after intracoronary injection of bone marrow MSCs into the coronary arteries of dogs in animal studies. Pathological sections of the dog heart showed small typical foci of myocardial infarction with fibrous tissue deposition and mononuclear cell infiltration in the myocardial tissue supplied by the gyral branch of the coronary artery [10]. However, no such reports have been made in clinical trials. Most of the cells used clinically are bone marrow or peripheral blood mononuclear cells, which are uncultured with a diameter of about 10 μm and rarely form cell clumps, and are less likely to cause fine coronary artery occlusion. We applied primary bone marrow single nucleated cells with small cell diameters, and this was able to avoid the occurrence of tiny infarcts. Also in this group of cases, which are patients with old myocardial infarction, the patient’s heart has already received an ischemic infarction blow to produce and establish an extensive adaptive collateral circulation, so the cells lodged in the microvascular bed of the coronary artery will not cause the occurrence of myocardial infarction. Early results of our study found that, except for one patient with left heart assisted implantation, none of the 16 patients had myocardial enzymes CK and CK-MB exceeding four times normal values on day 1 after surgery, while no new Q waves or ST-T elevation on ECG were observed.
The proportion of stem cells surviving in the heart after transcoronary transplantation has been reported in the literature to be about 5%, with the majority distributed to the lung, liver and spleen [11]. In our study, no pulmonary embolism was observed in the early post-operative period; no liver failure occurred, and transaminase elevations due to extracorporeal circulation and left heart assist were between two and three times the normal standard; and no renal failure was observed in the early post-operative period. During the follow-up of our study, one patient was found to have peripheral type tumor of the lung at 16 months postoperatively and underwent wedge resection of the lung lobes, which was pathologically confirmed as adenocarcinoma of the lung, and is still alive at 36 months of follow-up. There is still no conclusive evidence internationally on whether stem cell transplantation can increase tumorigenesis. A more rigorous observational evaluation remains to be performed.
References
1, Mickleborough 2.Elefteriades 3, Fuster 4,Vassalli 5,Dohmann 6, Perin EC, Silva GV.Stem cell therapy for cardiac diseases.Curr Opin Hematol.2004 Nov;11(6):399-403. 7, Mesenche 8, Smit 9,Assmus Circulation 2002; 106: 3009C17. 10, Vulliet 11, Zhang