Clinical Focus

  • Pediatric Cardiac Surgery
  • Thoracic Surgery (Cardiothoracic Vascular Surgery)

Academic Appointments

Professional Education

  • Board Certification: Thoracic Surgery (Cardiothoracic Vascular Surgery), American Board of Thoracic Surgery (2017)
  • Fellowship:Stanford University Dept of Cardiothoracic Surgery (2018) CA
  • Residency:Stanford University Dept of Cardiothoracic Surgery (2016) CA
  • Medical Education:Columbia University College of Physicians and Surgeons (2010) NY
  • BS, Stanford University, Chemical Engineering (2003)

Research & Scholarship

Current Research and Scholarly Interests

Our lab aims to understand the biomechanics that govern a wide spectrum of congenital heart defects, and how those biomechanics change with contemporary operative repair strategies. We simulate operations virtually via CFD, and in ex vivo and in vivo animal models, and analyze how the changes we make alter fluid flow, pressure, and stresses throughout the system. We hope that these experiments can impact and optimize existing techniques that translate quickly to the operating room.


All Publications

  • Comprehensive Management of Major Aortopulmonary Collaterals in the Repair of Tetralogy of Fallot. Seminars in thoracic and cardiovascular surgery. Pediatric cardiac surgery annual Ma, M., Mainwaring, R. D., Hanley, F. L. 2018; 21: 75–82


    The heterogenous anatomy of Tetralogy of Fallot with major aortopulmonary collateral arteries has engendered a similar degree of diversity in its management and, ultimately, outcome. We summarize our comprehensive treatment paradigm for this lesion evolved over 15 years of experience through 458 patients and the results obtained. An updated analysis of 307 patients treated primarily at our institution is included. A review of recent literature, comparison of management strategies, and discussion of ongoing controversies are provided.

    View details for DOI 10.1053/j.pcsu.2017.11.002

    View details for PubMedID 29425528

  • A novel inflow cannulation strategy for pediatric mechanical circulatory support in small left ventricles. journal of thoracic and cardiovascular surgery Ma, M., Yarlagadda, V. V., Rosenthal, D. N., Maeda, K. 2017

    View details for DOI 10.1016/j.jtcvs.2017.03.034

    View details for PubMedID 28416331

  • Repair of Ductus or Hemi-Truncus to One Lung and Major Aortopulmonary Collaterals to the Other Lung. The Annals of thoracic surgery Mainwaring, R. D., Rosenblatt, T. R., Patrick, W. L., Ma, M., Peng, L., Hanley, F. L. 2018


    BACKGROUND: There are patients born with pulmonary atresia and a ductus arteriosus or hemi-truncus to one lung and major aortopulmonary collateral arteries (MAPCAs) to the contralateral lung. The purpose of this study was to review our surgical results for this relatively rare subset of patients.METHODS: This was a retrospective review of 35 patients with ductus/hemi-truncus in association with pulmonary atresia with ventricular septal defect and MAPCAs. Our surgical algorithm is bifurcated into two strategies: 1) patients with "favorable" MAPCAs are candidates for single stage complete repair, and 2) patients with "unfavorable" MAPCAs undergo a staged approach. The median age at surgery was 3 months (range 1-7 months), and the mean number of MAPCAs was 3.1 ± 1.3.RESULTS: Twenty patients underwent a single stage complete repair. All 20 of these patients are alive with a right ventricle to aortic pressure ratio of 0.34 ± 0.07. The distribution of pulmonary blood flow by lung perfusion scan was 44% to the right and 56% to the left lung. Fifteen patients underwent a staged approach, including unifocalization of the MAPCAs to a central shunt. There were two interim deaths. Twelve patients have undergone complete repair with a right ventricle to aortic pressure ratio of 0.38 ± 0.07. There was one late death after complete repair. The distribution of pulmonary blood flow was 39% to the right and 61% to the left lung.CONCLUSIONS: The data demonstrate that 32 of 35 patients with ductus/hemi-truncus and MAPCAs ultimately achieved complete repair with relatively low pulmonary artery pressures.

    View details for DOI 10.1016/j.athoracsur.2018.03.041

    View details for PubMedID 29684371

  • An analysis of patients requiring unifocalization revision following midline unifocalization for pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals. European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery Mainwaring, R. D., Patrick, W. L., Ma, M., Hanley, F. L. 2018


    OBJECTIVES: Midline unifocalization has been developed for the surgical treatment of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries. All patients will eventually require reoperation because of the presence of a conduit, and some patients may also require revision of the distal unifocalized bed. The purpose of this study was to analyse the need for unifocalization revision following midline unifocalization.METHODS: This was a retrospective review of 241 patients who underwent midline unifocalization for the treatment of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries. Two hundred and four (85.4%) patients had a single-stage complete repair, whereas 37 patients had a unifocalization and placement of a central shunt. Seventy-eight patients have subsequently undergone reoperations at our institution, including 44 operations that required unifocalization revision. These 44 patients were compared with the 191 operative survivors who did not require revision.RESULTS: An analysis of risk factors for requiring unifocalization revision included the following: (i) single-stage complete repair versus unifocalization and shunt (14.7% vs 37.8%, P<0.001), (ii) right ventricle to aortic pressure ratio at the initial repair (0.33±0.07 vs 0.44±0.08, P<0.001) and (iii) absence of central pulmonary arteries (32.8% vs 13.4%, P<0.001).CONCLUSIONS: Data demonstrate that 44 of 241 (18%) patients who underwent midline unifocalization have subsequently required revision of their unifocalization. The need for unifocalization revision was associated with 3 factors, all of which were known at the time of discharge from the initial unifocalization. These data suggest that potentially higher risk patients should be monitored more closely than their lower risk counterparts.

    View details for DOI 10.1093/ejcts/ezy017

    View details for PubMedID 29447337

  • Current status of domino heart transplantation. Journal of cardiac surgery Shudo, Y., Ma, M., Boyd, J. H., Woo, Y. J. 2017; 32 (3): 229-232


    Domino heart transplant, wherein the explanted heart from the recipient of an en-bloc heart-lung is utilized for a second recipient, represents a unique surgical strategy for patients with end-stage heart failure. With a better understanding of the potential advantages and disadvantages of this procedure, its selective use in the current era can improve and maximize organ allocation in the United States. In this report, we reviewed the current status of domino heart transplantation.

    View details for DOI 10.1111/jocs.13104

    View details for PubMedID 28219115

  • Recovery of a Missile Embolus From the Right Ventricle. Annals of thoracic surgery Marshall, C. D., Ma, M. R., Park, J., Sheckter, C. C., Massoudi, R. A., Ligman, C. M., Jou, R. M., Ogden, W. D. 2017; 103 (1): e69-e71


    Missile embolism is a clinical entity in which a projectile object enters a blood vessel and is carried to a distant part of the body. We present a case of the discovery of an iliac vein to right ventricle missile embolus in a young man, with successful extraction through a right atriotomy. We provide a historical overview of the literature concerning missile embolism, and we argue that whereas acute embolized projectiles should be removed in almost all cases, it may be reasonable to simply observe an asymptomatic chronic missile embolus.

    View details for DOI 10.1016/j.athoracsur.2016.06.107

    View details for PubMedID 28007279

  • Pulmonary Valve Repair for Patients With Acquired Pulmonary Valve Insufficiency ANNALS OF THORACIC SURGERY Said, S. M., Mainwaring, R. D., Ma, M., Tacy, T. A., Hanley, F. L. 2016; 101 (6): 2294-2301


    Pulmonary valve (PV) insufficiency is often an acquired condition after treatment for pulmonary stenosis. It is recognized that PV insufficiency has serious deleterious effects. Although surgical replacement of the PV is efficacious, artificial valves inevitably fail and require re-intervention. The purpose of this study was to summarize our experience with PV repair in patients with acquired PV insufficiency.This was a retrospective review of 16 patients with marked PV insufficiency who underwent PV repair. Thirteen of these patients were born with tetralogy of Fallot (TOF) and had undergone a previous transannular patch repair. Three patients were born with critical pulmonary stenosis and had a surgical valvotomy or balloon valvuloplasty.The 13 patients with TOF had resection of their previously placed transannular patch with re-approximation of the anterior commissure. All 13 patients experienced a marked reduction in the degree of pulmonary insufficiency. None of these patients have experienced any increase in insufficiency during follow-up. The 3 patients with critical pulmonary stenosis had a variety of pathologic findings identified at the surgical procedure. One patient had a large gap between a commissure and underwent closure of that commissure. The second and third patients had torn leaflets repaired with pericardial and Gore-Tex patches (Gore, Inc, Flagstaff, AZ). The degree of PV insufficiency was decreased to mild in all 3 patients. However, 2 of these 3 patients have subsequently had an increase in the degree of pulmonary insufficiency.Patients with TOF who underwent a previous transannular patch may be candidates for bicuspidization of their native PV, and the results of this procedure have been quite stable at follow-up. PV repair for torn leaflets was effective in the short term but was less stable over time.

    View details for DOI 10.1016/j.athoracsur.2016.01.035

    View details for Web of Science ID 000376502600043

    View details for PubMedID 27083251

  • Anatomic Factors Associated With Truncal Valve Insufficiency and the Need for Truncal Valve Repair. World journal for pediatric & congenital heart surgery Patrick, W. L., Mainwaring, R. D., Carrillo, S. A., Ma, M., Reinhartz, O., Petrossian, E., Selamet Tierney, E. S., Reddy, V. M., Hanley, F. L. 2016; 7 (1): 9-15


    Truncus arteriosus is a complex and heterogeneous form of congenital heart defect. Many of the risk factors from several decades ago, including late repair and interrupted aortic arch, have been mitigated through better understanding of the entity and improved surgical techniques. However, truncal valve dysfunction remains an important cause of morbidity and mortality. The purpose of this study was to evaluate the anatomic factors associated with truncal valve dysfunction and the need for truncal valve surgery.This was a retrospective review of 72 infants who underwent repair of truncus arteriosus at our institution. The median age at surgery was nine days, and the median weight was 3.1 kg. Preoperative assessment of truncal valve insufficiency by echocardiography revealed no or trace insufficiency in 30, mild in 25, moderate in 10, and severe in 7. The need for truncal valve surgery was dictated by the severity of truncal valve insufficiency.Sixteen (22%) of the 72 patients undergoing truncus arteriosus repair had concomitant truncal valve surgery. Anatomic factors associated with the need for truncal valve surgery included an abnormal number of truncal valve cusps (P < .005), presence of valve dysplasia (P < .005), and the presence of an anomalous coronary artery pattern (P < .005). Fifteen (94%) of the sixteen patients who underwent concomitant surgery had two or all three of these anatomic factors (sensitivity = 94%, specificity = 85%).This study demonstrates that the presence of specific anatomic factors was closely associated with the presence of truncal valve insufficiency and the need for concomitant truncal valve surgery. Preoperative evaluation of these anatomic factors may provide a useful tool in determining who should undergo concomitant truncal valve surgery.

    View details for DOI 10.1177/2150135115608093

    View details for PubMedID 26714988

  • Post-Transplant Hemodialysis Drastically Reduces One-Year Survival in Patients Entering Liver Transplantation without Renal Dysfunction. 9th Joint Meeting of the American-Society-of-Transplant-Surgeon/American-Society-of-Transplantation Ma, M., Brennan, T., Reyes, I., Tamura, M., Feng, S. WILEY-BLACKWELL. 2009: 261–261
  • Transplantation of hNT neurons into the ischemic cortex: Cell survival and effect on sensorimotor behavior JOURNAL OF NEUROSCIENCE RESEARCH Bliss, T. M., Kelly, S., Shah, A. K., Foo, W. C., Kohli, P., Stokes, C., Sun, G. H., Ma, M., Masel, J., Kleppner, S. R., Schallert, T., Palmer, T., Steinberg, G. K. 2006; 83 (6): 1004-1014


    Cell transplantation offers a potential new treatment for stroke. Animal studies using models that produce ischemic damage in both the striatum and the frontal cortex have shown beneficial effects when hNT cells (postmitotic immature neurons) were transplanted into the ischemic striatum. In this study, we investigated the effect of hNT cells in a model of stroke in which the striatum remains intact and damage is restricted to the cortex. hNT cells were transplanted into the ischemic cortex 1 week after stroke induced by distal middle cerebral artery occlusion (dMCAo). The cells exhibited robust survival at 4 weeks posttransplant even at the lesion border. hNT cells did not migrate, but they did extend long neurites into the surrounding parenchyma mainly through the white matter. Neurite extension was predominantly toward the lesion in ischemic animals but was bidirectional in uninjured animals. Extension of neurites through the cortex toward the lesion was also seen when there was some surviving cortical tissue between the graft and the infarct. Prolonged deficits were obtained in four tests of sensory-motor function. hNT-transplanted animals showed a significant improvement in functional recovery on one motor test, but there was no effect on the other three tests relative to control animals. Thus, despite clear evidence of graft survival and neurite extension, the functional benefit of hNT cells after ischemia is not guaranteed. Functional benefit could depend on other variables, such as infarct location, whether the cells mature, the behavioral tests employed, rehabilitation training, or as yet unidentified factors.

    View details for DOI 10.1002/jnr.20800

    View details for Web of Science ID 000237217100008

    View details for PubMedID 16496370

  • Transplanted human fetal neural stem cells survive, migrate, and differentiate in ischemic rat cerebral cortex PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kelly, S., Bliss, T. M., Shah, A. K., Sun, G. H., Ma, M., Foo, W. C., Masel, J., Yenari, M. A., Weissman, I. L., Uchida, N., Palmer, T., Steinberg, G. K. 2004; 101 (32): 11839-11844


    We characterize the survival, migration, and differentiation of human neurospheres derived from CNS stem cells transplanted into the ischemic cortex of rats 7 days after distal middle cerebral artery occlusion. Transplanted neurospheres survived robustly in naive and ischemic brains 4 wk posttransplant. Survival was influenced by proximity of the graft to the stroke lesion and was negatively correlated with the number of IB4-positive inflammatory cells. Targeted migration of the human cells was seen in ischemic animals, with many human cells migrating long distances ( approximately 1.2 mm) predominantly toward the lesion; in naive rats, cells migrated radially from the injection site in smaller number and over shorter distances (0.2 mm). The majority of migrating cells in ischemic rats had a neuronal phenotype. Migrating cells between the graft and the lesion expressed the neuroblast marker doublecortin, whereas human cells at the lesion border expressed the immature neuronal marker beta-tubulin, although a small percentage of cells at the lesion border also expressed glial fibrillary acid protein (GFAP). Thus, transplanted human CNS (hCNS)-derived neurospheres survived robustly in naive and ischemic brains, and the microenvironment influenced their migration and fate.

    View details for DOI 10.1073/pnas.0404474101

    View details for Web of Science ID 000223276700056

    View details for PubMedID 15280535

    View details for PubMedCentralID PMC511061