The Visible Heart® is a live beating heart functioning outside of the body under simulated physiologic conditions. Standard cardiac transplant procedures are employed to arrest a donor heart and prepare it for reanimation. As with clinical heart recoveries, during the time required to remove the heart and transplant it into the recipient, the heart remains inactive and is inhibited from spontaneously contracting. This is accomplished by cooling the heart in an ice slurry (hypothermia) and infusing a cold high potassium solution cardioplegia through the coronary arteries. These same conditions or experimental modifications are employed and analyzed for effective need in our laboratory studies.

The isolated heart apparatus is an experimental simulation of the donor recipient, providing oxygen and metabolic substrates for the heart to survive. However, in order to view the internal structures of the beating heart, non-transparent blood is replaced by a clear synthetic blood-like solution (which does not contain red blood cells.)

As the coronary system of the heart, which enables the transport of oxygen and metabolic substrates to the heart, relies on the pressure created by the heart itself for flow, initially the heart must be externally assisted after transplantation. This is accomplished by pumping fluid directly into the coronary system and removing fluid from the heart’s chambers to ease the burden, a technique called the Langendorff mode of perfusion. Once the heart is capable of maintaining pressures and flows independently, it is weaned (a slow transition) out of Langendorff mode and the native flow pattern is re-established. Now the heart has fluid movement through all four chambers and is responsible for the work required to maintain the flow through the coronary system, hence the name Four Chamber Working Mode.

This preparation was reviewed and approved by the University of Minnesota Animal Use and Care Committee. All animals received humane care in compliance with the “Guide for the Care and Use of Laboratory Animals” published by the National Institutes of Health. Similarly, the use of the isolated human hearts has be reviewed and approved by the University of Minnesota human subjects committee.

Human hearts are obtained as generous gifts from LifeSource Upper Midwest Organ Procurement Organization, Inc, St. Paul, Minnesota. This research is made possible due to the generous gifts of individuals whose hearts have been donated for research purposes. Their final act of generosity will enhance understanding of the inner workings of the human heart and contribute to lifesaving advances in cardiac medicine.