ACTIVE ENDOCARDIAL COOLING OF EXPLANTED HEARTS BY ICED SALINE CIRCULATED VIA NOVEL INTRA VENTRICULAR BALLOON CATHETERS

Abstract

Hypothermia is an important component of cardiac myocyte preservation during organ procurement and ischemic arrest. At the time of organ implantation passive rewarming occurs. This re-warming can be partially prevented by employing an external cooling jacket but these devices are cumbersome and often obstruct the surgical field. We have developed a novel approach that provides active endocardial cooling via intraventricular cooling balloons. An intracardiac cooling device was created using a modified surgical glove secured to the end of a hemodyalysis catheter. Use of a dual port catheter allowed for continuous circulation of saline to the balloon. Two such catheters were then connected in parallel and placed in the right and left ventricles via the pulmonic and aortic roots respectively. Saline was added through a side port to allow for precise control of intraventricular volume. A roller pump directed saline through cooling coils to the balloons. An explanted diseased human heart was obtained from the recipient at the time of transplantation and placed in a simulated thoracic cavity that consisted of a shallow pool of 32°C saline circulating in a metal basin. Needle temperature probes were placed in the right and left ventricular walls. Temperature curves were recorded during passive re-warming and compared to active cooling using either the intraventricular balloon device or direct ventricular filling with iced saline (4°C). Between experiments the heart was submerged in an iced saline bath for 10 minutes to obtain maximal global cooling. Right and left ventricular temperatures increased 18.0°C (from 9°C to 27°C) and 14.3°C (from 12°C to 26.5°C) respectively during the 75-minute period of passive cooling. This represents an average increase of 1.1°C/5 minute interval. With the addition of the device, ventricular temperatures rose 6.5°C (from 12.5°C to 19.0°C) and 5.3°C (from 13.2°C to 18.5°C). an average 0.4°C/5 minute interval. Lastly, the temperature in the right and left ventricles directly filled with iced saline increased only 1.8°C (from 10°C and 11.8°C) and 5.5°C (from 11°C to 16.5°C) respectively, an average rise of only 0.25°C/5 minute interval. Myocardial cooling during organ implantation can be accomplished by active circulation of iced saline to the ventricular endocardium. While not as efficient as direct iced saline ventricular filling, with design modifications such a device may provide a measurable benefit on organ preservation and subsequent ventricular function.