1. Field of the Invention
This invention relates to a method and apparatus for delivering material to the veins of the heart during open heart surgery. More particularly, this method and apparatus allows cardioplegia type material to be transported into the coronary veins through the coronary sinus of the heart such that the cardioplegia is distributed in a substantially homogenous manner throughout the heart.
2. Discussion
During open heart surgery it has been found that it is very advantageous to distribute cardioplegia type material within the coronary veins of the heart. The functions of such cardioplegia include keeping the heart cold thereby providing protection during surgery, washing away metabolic waste products, providing metabolic nutrients in order to satisfy the heart's existing energy requirements, and keeping the heart electrically quiescent. Because of these important cardioplegic functions it is known to be very desirable to have the cardioplegia evenly and completely distributed within the entire coronary vein system of the heart. This complete homogeneous distribution of cardioplegia assures that the entire heart is subject to these aforementioned favorable cardioplegia functions. A failure to homogeneously distribute cardioplegia to the heart, during surgery, is known to possibly cause a deterioration of the heart's functioning in the post operative period. Cardioplegia distribution is therefore known to possibly be a very important factor in the ability of the heart to recover from such heart surgery.
In the past, the cardioplegia was usually delivered to the arteries of the heart through the aorta root. It has been found however that this method will not always result in a truly homogeneous distribution of cardioplegia within the coronary arteries. For example, if the heart has a general coronary atherosclerosis condition, its coronary artery passages may be blocked to a very large extent. The cardioplegeia that had been injected through the aorta root may therefore, not be able to pass through these narrow artery passages. This may result in a non-homogeneous distribution of cardioplegia within the coronary arteries. To alleviate this potential problem, various methods have been employed which have sought to deliver cardioplegia directly (i.e in a retrograde manner) to the coronary sinus. These methods have chosen the coronary sinus because it is known that such coronary obstructive type diseases never occur in the coronary venous system and because such cardioplegic delivery, directly into the coronary sinus (which comprises a large vein), could provide for the desired homogeneous cardioplegic distribution.
One example of such a coronary sinus method requires the cannulation of the coronary sinus by directly injecting cardioplegic solution therein. This approach has many potential drawbacks. For example, placing a cannula within the coronary sinus has been found to be very difficult. Once the cannula has been placed within the coronary sinus it has been found to be equally as difficult to keep it in position for a length of time necessary to allow all of the cardiopelgia to be placed within the sinus. Such direct cannulation procedures may even cause extensive damage to the sinus itself. Lastly, it has been found that a relationship exists between the resultant homogeneity of cardioplegic distribution and the distance in which the cannula is placed within the sinus. Such a critical relationship evidences the fact that such a cannulation procedure might arguably produce poorer cardioplegic distributions than even the aforementioned aortic root technique.
Other presently used methods for introducing cardioplegia into the coronary venous system and more particularly into the coronary sinus itself, includes the steps of cannulating both the superior and inferior vena cavas; opening the right heart atrium; and then cannulating the coronary sinus under direct vision or manipulating the coronary sinus manually, with a cannula in place. These methods are extremely difficult to perform and again include the step of direct cannulation of the coronary sinus. They therefore suffer from the same drawbacks as was associated with the first method discussed (i.e. only requiring direct sinus cannulation). It is clear then, that an improved technique is needed to allow for the homogeneous distribution of cardioplegia within the coronary veins of a heart, even under such heart conditions such as coronary atherosclerosis. It is equally clear, that such a new and improved technique should avoid direct cannulation of the coronary sinus and should avoid the aforementioned problems and drawbacks associated with the prior techniques.