< back

Cardiac

Principal Investigator:
David F. Torchiana, M.D.

Group Members:
Arvind K. Agnihotri, M.D.
Jennifer White, M.D.
James Titus

Located in Edwards 112, the cardiac surgical research laboratory has historically focused on improving intra-operative myocardial protection through studies of cardioplegia, ischemia and reperfusion. In addition to this continued effort we are presently engaged in development efforts for devices and techniques to facilitate minimally invasive and novel approaches to cardiac surgery. We are working in a large animal model to develop the many complex steps needed to perform endoscopic coronary revascularization including using a robotic interface, anastomotic devices and surgical sealants. We are working on an autologous tissue valve and a new type of expandable cannula for peripheral vascular access. We have a relationship with a start up company that is developing a device for direct coronary revascularization from the ventricular cavity. The techniques and technologies employed center largely on large animal models, surgical procedures involving cardiopulmonary bypass and the latest devices in minimally invasive surgery as well as extensive grounding in cardiovascular physiology.

Myocardial Protection:
In recent studies we have evaluated the effects of normothermic cardioplegic solutions looking at myocardial metabolism during ischemic intervals using repeated non-destructive measurements of metabolites in an isolated perfused canine model supported in an NMR magnet. We have also studied the effect of cardioplegic temperature on coronary resistance and the ratio of subendocardial to subepicardial perfusion using radiolabelled microspheres in a porcine model. Both studies were published in the Annals of Thoracic Surgery last year. In follow-up to the latter study we completed an evaluation of a normothermic "microcardioplegia" system containing adenosine to determine the effect of this additive on the efficacy of arrest, coronary resistance and delivery. We found an improvement in the ability of a normothermic solution to maintain arrest with adenosine added as well as a beneficial reduction in coronary vascular resistence.

Endoscopic Coronary Artery Bypass:
Over the past two years we have used one of the commercially available Robotics system to perform totally endoscopic coronary artery bypass procedures using both internal mammary arteries in dogs supported by cardiopulmonary bypass. The procedure uses 3D visualization with a headmounted display and a voice activated robotic camera. Future modifications of the procedure will include the development of an image guided "Virtual Fixturing" technique in conjunction with Professor Robert Howe of the Harvard School of Engineering to enable automated image guided robotic actions as a part of the IMA harvest procedure. We have also used an endoscopically deployed anastomotic device to create proximal aortic anastomoses to enable multivessel grafting and complete revascularization and to enable aortic cross clamping and antegrade cardioplegia delivery without an endoaortic balloon. Clinical use of the robotics system began with a prospective randomised trial of endoscopic IMA mobilization which started in the Spring of 2001.

Surgical Sealants:
We have conducted several studies using Focalseal, a polyethylenegycol based hydrogel, which has proven to be a remarkably effective hemostatic adjunct without tissue toxicity or deleterious effects on coronary vessels/anastomoses. In the last year these results have been presented at the International Society for Minimally Invasive cardiac surgery and a manuscript published in the Heart Surgery Forum. We plan further evaluation of the sealant for use as an external stent for venous bypass grafts to limit intimal hyperplasia and medial hypertrophy to improve long term graft patency. These studies will be conducted in a chronic animal model.

Direct Coronary Revascularization:
We are in the early stages of development of a device designed to create a communication from the LV cavity directly into distal coronary arteries to provide distal perfusion in ischemic heart disease. The development effort is concentrated on working with engineers to perfect the devices necessary and to define and understand the physiology of this unique form of coronary perfusion.

Other Projects:
We are in the early stages of developing an autologous aortic valve substitute fashioned from the wall of the pulmonary artery. Dr. Torchiana work as a scientific advisor to several start-ups developing minimally invasive methods for the treatment of atrial fibrillation, one of which is currently in clinical trials at MGH, BWH and Columbia. We are in the early stages of development of a novel expandable cannula design for peripheral and central vascular access.

Principal Investigator:
Gus J. Vlahakes, M.D.

Senior Technician:
J. Luis Guerrero

Hemoglobin-Based Oxygen Carrying Solutions, Physiology and Application in Cardiac Surgery:
Dr. Vlahakes' laboratory has focused on cardiac surgical applications of hemoglobin polymer solutions. The work deals with oxygen transport physiology, and the experimental models in use include models involving extracorporeal circulation and models designed to assess long-term effects. The majority of the work is in large-animal surgical models.

Right-Heart Function:
The laboratory has had an ongoing interest and effort in physiologic studies of right heart function and failure. This has been directed towards issues related to the management of heart transplant patients and has helped devise treatment strategies for this often-challenging clinical problem.

The Thymus and Immune Tolerance:
In conjunction with Dr. Joren Madsen, we are currently investigating techniques to simultaneously transplant donor thymus gland along with the heart in an attempt to have a cardiac recipient regard the donor heart as "self." In the current stage of this work, we are developing techniques to permit transplantation of this organ which has a complex blood supply and venous drainage. In subsequent experiments, we will be examining immunologic issues such as the duration (age) during which time the thymus can exert this function. This work is open-ended, in that in addition to generating new information, each experimental protocol also generates new questions that must be answered to permit possible clinical application of simultaneous thymus transplantation.

Cardiac Tissue Engineering:
In the next year, the laboratory will be starting a research effort in tissue engineering, with the goal of developing heart valves for use on the left side of the circulation. This work will be done in conjunction with tissue engineering efforts currently underway at MGH.

Principal Investigator:
Joren Madsen, M.D.

For a description of Dr. Madsen's research activities, please see the "Cardiothoracic Transplantation Laboratory" in the TBRC.

back to top