| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Eur J Cardiothorac Surg 2006;29:S259-S265
© 2006 Elsevier Science NL
a Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
b Option on Bioengineering, California Institute of Technology, Pasadena, CA, USA
c Division of Cardiovascular Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
Received 2 February 2006; accepted 6 February 2006.
* Corresponding author. Address: Department of Surgery, Heart Institute (InCor), University of São Paulo Medical School, Av. Dr. Enéas de Carvalho de Aguiar, 44–5th Floor, 05403-000 São Paulo, SP, Brazil. Tel.: +55 11 3069 5942; fax: +55 11 3069 5092. (Email: sergioaoliveira{at}incor.usp.br).
 |
Abstract |
|---|
 Top Abstract 1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
Key Words: Stem cells • CABG • Ventricular geometry • Late hyper enhancement • Sphericity index • Elliptical shape
|
1. Introduction |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
In 2002, a cell therapy program was established in our Center to test the hypothesis that intramyocardial injection of autologous BMC may act as an adjunctive therapy to surgical myocardial revascularization using either coronary artery bypass grafting (CABG) and/or transmyocardial laser revascularization (TMLR) in patients suffering from a more advanced (diffuse) coronary artery disease [13,14]. Functional data were collected, but this initial study was designed to evaluate safety and tolerability. This report summarizes data from two selected patients to define the potential use of this strategy in segments that could not undergo direct CABG. Each patient retained normal sphericity (length/width dimension), so that the cardiac configuration was elliptical at the time of cell implantation.
This report shows that cell implantation improves contractile function in these two patients with elliptical geometry, and shall explore the potential implications of this preliminary clinical data in the heart failure population with spherical ventricular geometry.
|
2. Methods |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
Myocardial perfusion/contractility was assessed by cardiac magnetic resonance imaging (MRI), and progenitor hematopoetic cells were obtained from the bone marrow before surgery as briefly described below.
2.1 Cardiac MRI
Patients underwent MRI examination in a 1.5 T MR scanner (Signa CV/i, GE Medical Systems, Waukesha, WI, USA). After scout images, first-pass myocardial perfusion left ventricle (LV) short-axis images were obtained 3 min after dipyridamole injection (0.56 mg kg–1 injected over 4 min). After dynamic MR images acquisition was started, 0.05 mM kg–1 of gadolinium-based contrast material (gadodiamide, OminiscanTM, Amersham Health, Princeton, NJ, USA) was injected into the antecubital vein by a power injector at a rate of 5 mL s–1 and followed by a 20-mL saline flush. Immediately after stress perfusion sequence aminophyline was intravenously injected.
Left ventricular function analysis employed a gradient-echo in steady-state acquisition (FIESTA) to acquire LV short- and long-axis views. Resting perfusion was then evaluated, employing the same parameters as the stress perfusion, with a second IV dipyridamole bolus of 0.05 mM kg–1. Myocardial delayed enhancement acquisition to investigate myocardial viability was then determined immediately after a final 0.1 mM kg–1 dipyridamole injection.
2.2 BMC isolation
Immediately prior to surgery, 100 mL of bone marrow was aspirated from the posterior iliac crest and the bone marrow mononuclear fraction was isolated by density gradient on Ficoll-Paque Plus (Amersham Biosciences, Piscataway, NJ, USA). A final volume of 5 mL of cell suspension was prepared. A panel of 12 antibodies was used for cell characterization by flow cytometry. The fractions of lymphocytes (CD19+, CD3+, CD38+), monocytes (CD14+), and hematopoetic progenitor cells (CD34+) were determined for each patient.
|
3. Results |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
The patient was asymptomatic, but had sustained acute myocardial infarction with ST elevation 8 months before this admission. Unstable angina developed 2 months ago and CABG was recommended. The physical examination was unremarkable, but BUN and creatinine were elevated (76 and 1.7 mg/dL, respectively), hemoglobin was low (10.3 g/dL) and fasting glucose level was moderately increased (156 mg/dL).
The electrocardiogram revealed normal sinus rhythm and normal LV axis (SÂQRS = 22°), with an anteroseptal and inferior infarction with nonspecific lateral T wave abnormalities. Chest radiograph disclosed a moderately enlarged left ventricle with mild pulmonary congestion. Cardiac MRI revealed LV ejection fraction of 32% with markedly depressed LV systolic function. Late enhancement by gadolinium MRI imaging was approximately 5%, and the sphericity index was 0.57. An extensive area of ischemia was noted on the LV anteroapical and inferolateral walls during pharmacological stress with dipyridamole, and ventriculography showed a significant systolic dysfunction due to an LV anterior and inferior wall hypokinesia.
Coronary angiography demonstrated multivessel coronary artery disease, including severe left main coronary artery disease, together with multiple and diffuse lesions in the distal portions of the coronary arteries. An expert panel considered this patient to be a candidate for an incomplete CABG because of the diffuseness and severity of the lesions, and these findings led to his enrollment in the cell therapy safety trial.
After providing written informed consent and immediately prior to surgery, 100 mL of bone marrow was aspirated from the posterior iliac crest and the bone marrow mononuclear fraction was isolated by density gradient on Ficoll-Paque Plus (Amersham Biosciences). A final volume of 5 mL of cell suspension containing approximately 55.0 x 106 cells mL–1 showed cell viability greater than 90%. The fractions of lymphocytes (CD19+, CD3+, CD38+), monocytes (CD14+), and hematopoetic progenitor cells (CD34+) were 37%, 3.5%, and 1.7%, respectively.
CABG was done during cardiopulmonary bypass and warm blood cardioplegic arrest, including a saphenous vein graft (SVG) to left anterior descending diagonal artery (severely diseased), posterior left ventricular (PLV) artery, and left internal thoracic artery graft to second marginal circumflex artery (CX). BMC were implanted into the ischemic anterior and inferior LV walls that were not grafted, whereby 25 samples of 0.2 mL of cell suspension were injected by a 22-gauge needle. There were no complications during the procedure. The patient recovered uneventfully, and was discharged on the 7th day after surgery.
The patient remained asymptomatic during follow-up over 1 year. Cardiac MRI examination was done at 1 and 12 months after the procedure and compared to baseline. The myocardial infarction area seen at baseline was unchanged after the procedure, corresponding to approximately 5% of the LV mass (Fig. 1 ). Striking improvement of baseline extensive perfusion defects occurred, with almost complete resolution 12 months after the procedure. LV contractility (Fig. 2 ) improved remarkably, as ejection fraction reached 64% at 6 months, and was 55% at 12 months after the procedure. Tagging studies were done by MRI to determine deformation in the muscle, before and after receiving cell implantation. The postoperative study showed normal deformation, which was absent in the preoperative evaluation.
|
|
3.2 Cell therapy plus TMLR
A 74-year-old male was admitted for worsening of angina and exertional dyspnea. Coronary artery bypass graft surgery following myocardial infarction was performed 20 years before this admission. Hypertension and insulin-dependent diabetes existed, without smoking or alcohol history, and he was asymptomatic until 3 years ago.
The patient noticed shortness of breath after walking a short distance 3 years ago, together with unstable angina requiring attempts at balloon angioplasty that were unsuccessful. The ability to perform physical activity was moderately impaired, despite clinical management on medical therapy. Three months ago, symptoms of angina and dyspnea accentuated, resulting in inability to perform any daily physical activity without symptoms. More recently, angina and dyspnea worsened, and occasionally developed at rest, with associated orthopnea. Maximally tolerated medical therapy was started with little improvement of functional status. He was diagnosed as having refractory angina and severe IHD and referred to our Center for further evaluation.
On admission, the patient did not look ill, was breathing comfortably, but had elevated jugular venous pressure. Although cardiac sounds were normal, basal bilateral pulmonary rales were noted, the liver was slightly enlarged, and peripheral edema existed.
Laboratory tests showed normal urea nitrogen, creatinine, and hemoglobin and increased fasting glucose levels. The electrocardiogram revealed sinus tachycardia, right axis deviation (SÂQRS = 123°), left atrial enlargement, anterior infarction, and diffuse ST-T abnormalities. Chest radiograph disclosed an enlarged left ventricle with mild pulmonary congestion.
Cardiac MRI revealed LV ejection fraction of 27% with markedly depressed systolic function. Sphericity Index (width/length) was 0.56. Pharmacological stress with dipyridamole demonstrated extensive ischemia of LV anterior, septal and inferior walls (Fig. 3 ). A late enhancement study by gadolinium was compatible with subendocardial myocardial infarction of antero-septal wall. An area of late enhancement compatible with subendocardial myocardial infarction was observed on the antero-septal wall but was <10%.
|
|
Limited left anterolateral thoracotomy at the 5th left intercostal space provided access for TMLR with the CO2 Heart Laser System (PLC Medical Systems, Milford, MA, USA) that delivered 800 W in pulses 1–99 ms long at energies of 8–80 J to create 1-mm diameter channels at a 1000 W maximum energy output. Eleven laser shots were fired, into the anterior (n = 3), lateral (n = 4), and inferior (n = 4) ventricular walls.
The autologous BMC cell suspension, containing approximately 21.5 x 106 cells mL–1 was delivered by multiple intramyocardial injections in the anterior, septal, and lateral walls without complications. The fractions of lymphocytes (CD19+, CD3+, CD38+), monocytes (CD14+), and hematopoetic progenitor cells (CD34+) were 26%, 3.5%, and 0.9%, respectively.
Postoperative atrial fibrillation developed on 2nd day, and was successfully returned to sinus rhythm by electric cardioversion, which was maintained by oral amiodarone treatment. Pulmonary congestion was managed by IV loop diuretics and the patient was discharged at the 10th day after the procedure.
Functional status increased during the first 6 postoperative months afterwards, allowing reduction of diuretic treatment, but short-acting nitrates were retained for daily activities. Cardiac MRI at 6 months showed striking improvement of the baseline perfusion defect, with near complete resolution of prior extensive changes (Fig. 3). The small area of hyper enhancement did not change. Ejection fraction rose from 27% to 43% as LV contractility improved in the conical ventricle as shown in Fig. 3, coupled with increased end-systolic and end-diastolic wall thickness.
|
4. Comment |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
These data of functional improvement support other information [15] about the value of using autologous BMC as an adjunctive therapy to surgical myocardial revascularization, in patients suffering from diffuse CAD, who were not optimal candidates for complete conventional surgical myocardial revascularization. Furthermore, the implications of this evaluation that joins cell implantation, MRI technology for extent of viability and improved ventricular function of a chamber with a normal configuration initiates an operative approach that may provide novel insight into future treatment of ischemic and nonischemic dilated cardiomyopathy.
Mechanisms responsible for the observed results are beyond the scope of this report, but the improved perfusion supports angiogenesis in newly injected areas. It is uncertain whether transdifferentiation of transplanted cells into vascular endothelial cells [16,17], the action of cytokines and growth factors released locally either after TMLR or by the injected cells themselves [18], or both factors acted synergistically to allow angiogenesis and subsequent functional improvement. The presence of a sustained ischemic background may play an important role in cell engraftment (homing) necessary for the therapeutic effect on any cell-based strategy [19]. Moreover, alternative or additional explanation for improvement in contractility may involve differentiation of the injected cells into cardiomyocytes although direct evidence for this phenomenon remains elusive.
Whatever the mechanism, the initial target of this study to improve myocardial perfusion and contractility in patients with advanced CAD, was achieved in the myocardial region that could not undergo CABG, and supports the effectiveness of cell transplantation. These early data set the stage for development of questions to be addressed in controlled studies with a larger series of patients and longer follow-up. This potential future option is selected because the early findings suggest the procedure is safe, allowing room for a cautious optimism regarding improvement in cardiac function associated with cell therapy approaches, and may ignite the scientific community to fill the gaps in our knowledge by moving this experimental approach into the clinical environment.
In this regard, a number of questions will have to be properly addressed. First, what is the best cell source to be used? Second, we will likely find different cells for different purposes. Therefore, how many cells shall be administered and by which route? Additionally, during myocardial infarction or large burn injury, nature has developed efficient mechanisms not only to mobilize cells from different stores, but also to turn on local magnets to attract and retain the progenitor cells to the desired site of repair.
Often in recent times we are succeeding to identify a number of new tissue stores of pluripotent cells but how to manipulate the magnet for therapeutic strategies remains largely unknown. Therefore, the efficacy of delivering cells by different routes including systemic, intracoronary, or directly into the myocardium will have to be determined and novel strategies devised to improve the number of viable cells that remain at the site of repair. Another issue evolving from the preclinical work is that there are several potential mechanisms underlying the reported improvements associated to cell therapy approaches. These processes may involve the simple-minded cell differentiation concept whereby transplanted pluripotent cells replace the lost ones in the proper manner considering that the just right environment suffices to correctly control the transdifferentiation process. There is also evidence for cell fusion or cell mediated modifications of the microenvironment via secretion of factors that may limit cell death, further attract progenitor cells or improve function of the remaining cells, but at present, the relative contribution of each of these processes are not known.
Simultaneously, a second target for use of autologous BMC is generated from these preliminary results, relating to the common theme of MRI and ventricular shape in the two patients. The MRI demonstrated viable muscle with <50% gadolinium hyper enhancement, supporting the capacity of this region to improve contractile function following the revascularization achieved by cell implantation. The findings in this study mirrored the improved performance recently reported following coronary revascularization recently reported [20] when late hyper enhancement is <50% [15].
|
5. Implications |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
This matching does not occur in dilated cardiomyopathy of nonischemic or ischemic origin, since the natural elliptical shape becomes spherical. The natural history of augmented size and shape is evident from the studies of White et al. [21], who showed the correlation of end systolic volume index with survival in ischemic patients. More importantly, this adverse parameter of spherical shape can be changed by ventricular restoration that rebuilds the elliptical scaffold by surgically excluding the scar that is the stimulus for remote muscle dilation and improves late survival [22,23]. A similar benefit happens in nonischemic cardiomyopathy, when surgical ventricular restoration excludes the most damaged region [24].
A novel interaction between cell biology, MRI technology, and surgical creation of the scaffold unfolds for the dilated cardiomyopathy population from the data presented herein. The entry point is that functional improvement follows autologous BMC injection into ischemic patients who had a conical form and received injections into muscle that MRI gadolinium scanning showed as predominantly viable. Translation of this information into the population of dilated cardiomyopathy requires three phases, together with knowledge about the commonality that exists between the ischemic and nonischemic cohort.
First, the spherical chamber is the unified geometry in these disease states, and surgical restoration rebuilds the elliptical form to create the elliptical scaffold that was already present in these two patients in this report. Second, many ischemic patients also have scar in remote muscle, so that MRI hyper enhancement may define which remote muscle has <50% hyper enhancement and can thus receive cell implantation at the time of surgical restoration in ischemic disease; the scar responsible for dilation is excluded by restoration and is not the cell implantation target. Furthermore, distribution of scar in nonischemic disease shows a nonhomogeneous allotment [25], so that restoration excludes the predominant disease, but leaves some disease in retained remote muscle. Third, future efforts at restoration and cell implantation can potentially be planned for (a) remote viable muscle in ischemic disease with MRI documented smaller infarction and (b) remote nonischemic muscle that has some retained disease. A macroscopic/microscopic marriage between surgical creation of the scaffold and microscopic growth from cell implantation into muscle documented by MRI to contain functionally recoverable muscle after revascularization. Conceivably, TMLR can be used if grafting is not possible.
These implications are introduced to expand the surgical capacity to create a macroenvironment that may also play a role in the success following cell transplantation. The goal is blending the instillation of new viable cellular tissue into the surgically developed scaffold for cell attachment of an organ with the proper shape. Conversely, injection of these potentially useful and necessary ingredients into a fully dilated heart may not be the right ground for biological repair. From example, viable muscle exists in the dilated hearts of patients with ejection fraction <40%, who undergo successful mitral or aortic valve repair or replacement for valvular heart disease; long-term mortality is 
70%, with deaths from congestive heart failure or arrhythmias, as ventricular form is not changed by valve implantation.
We suspect retention of this structural deficit will not be remedied by cell injection into these hearts with impaired contraction, since shape is not restored simultaneously. A similar result may occur in nonischemic or ischemic patients following cell implantation if the macroenvironment is not restored surgically. This macroscopic/microscopic marriage is a dual effect, whereby changes in macro—as well as the microenvironment must be considered when devising strategies aimed at biological repair of adult organs.
|
6. Conclusions |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
The implications of these findings are that a similar result may exist if the dilated cardiomyopathy was surgically rebuilt into a normal scaffold by restoration, and autologous stem cells were implanted in the retained remote muscle that has viability previously demonstrated by MRI imaging. Perhaps the merging of two simple concepts involving cell-mediated interventions in a proper tissue ground that is optimized to offer the right scaffold will open a new arena that improves function, the key ingredient for the success of biological cardiac repair; build the scaffold and inject the cells.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
Read at 10th RESTORE meeting in San Francisco, California, April 9, 2005. |
References |
|---|
|
TopAbstract1. Introduction2. Methods3. Results4. Comment5. Implications6. ConclusionsReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  G. D. Buckberg and the RESTORE Group Form versus disease: optimizing geometry during ventricular restoration Eur. J. Cardiothorac. Surg., April 1, 2006; 29(Suppl_1): S238 - S244. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
