1. Field of the Invention
The present invention relates in general to a device and method for coronary perfusion, and in particular to an intra-aortic coronary perfusion device. Still more particularly, the present invention relates to a piston-action balloon device which creates a high blood pressure region in the ascending aorta for the purpose of simultaneously perfusing the left and right coronary arteries in an injured or diseased patient's heart.
2. Description of the Prior Art
Heart disease is the leading cause of death in the United States and Europe. It is estimated that one in five individuals over the age of 60 will die of a heart attack resulting from heart disease in the United States. The primary cause of heart attacks are inadequate coronary blood supply, an anatomical disorder, or conduction disturbances. The particular cause of heart attacks and heart failures, and the damage that ensues, is the result of ischemic injury.
A tissue is ischemic when it receives an inadequate supply of oxygen because of inadequate blood flow. The most common cause of ischemic injury to the heart, or myocardial ischemia, is atherosclerosis of the coronary arteries. This is an occlusion of the arteries that supply the heart muscle, the coronary arteries, with oxygenated blood. The result of this blockage is a loss of blood flow to the heart muscle, thus a lack of oxygen to these tissues. Another major cause of ischemic injury is operative procedures on the heart, during which blood flow may be diverted or occluded from at least a portion of the cardiac tissue. Myocardial cells (heart tissue cells) are adapted to respire aerobically and cannot respire anaerobically for more than a few minutes. If ischemia and anaerobic respiration continues for more than a few minutes, necrosis (cellular death) will occur in areas of the heart where oxygen is most lacking. Thus, treatment of myocardial ischemia is critically time dependent.
There are a number of devices that are designed to treat blocked coronary arteries. Many of the devices to date share a common feature in that they are directed towards placement of a perfusion tube into either the left or right coronary artery, thus perfusing a particular coronary artery with oxygenated blood. These devices include the Karcher et al. (U.S. Pat. No. 4,804,358) device, which places a perfusion tube downstream from an occlusion in a coronary artery and uses an external oxygenated blood supply, the Scribner (U.S. Pat. No. 5,395,353) device, which is directed to a catheter that can be guided within the aorta into a particular coronary artery, then being placed near the ostium of the coronary artery, and the Pierpont (U.S. Pat. No. 5,484,412) device, which is several inflatable balloons acting to anchor a perfusion tube, while another balloon is used in an angioplasty procedure, being placed at the occlusion within a particular coronary artery. These devices are advantageous in directing an extra surge of oxygenated blood to where it is most needed--ischemically injured myocardium. However, these devices have the disadvantage of being difficult to use. Valuable time and expertise is necessary to determine which coronary artery to perfuse. Still more time is lost in inserting the device into the aorta and locating the ostium of the coronary artery. Further, these devices also incorporate extra-corporeal blood pumps that require an external source of blood, adding to the undesirability of these devices.
Ischemic injury can also occur to the cardiac tissue after surgery is performed on the heart and after procedures are performed on the coronary circulation to restore coronary blood flow. Surgical procedures on the heart often deplete the cardiac tissues of oxygen or produce other damage, which can result in prolonged depression of contractile function (stunned myocardium), even if not in fully developed ischemic injury to the myocardium. Procedures to restore coronary blood flow by thrombolysis or agioplasty can produce re-perfusion injury, which also results in stunned myocardium. Stunned myocardium gradually recovers normal contractile function if coronary blood flow can be maintained. As a result of myocardial stunning, the blood pressure can be diminished, thus resulting in loss of blood flow through the coronary arteries. As a result, the blood pressure can be diminished, thus resulting in loss of blood flow through the coronary arteries. This exacerbates recovery of the myocardium and can lead to more damage to the heart tissue. Post-operative measures are often taken to improve coronary artery blood pressure, thus normalizing heart function and improving the patient's overall blood pressure. The most common method used to improve the blood pressure post-operatively is a heart-lung machine. However, a heart-lung machine is limited in its usefulness due to the mechanical stresses placed on the blood elements. Anticoagulants such as heparin must be used in large quantities to inhibit blood clotting, but this can also lead to detrimental side effects such as excessive bleeding of the patient. When blood pressure is diminished following procedures to restore coronary blood flow, drugs can be administered to elevate the blood pressure, but this produces an additional burden on the heart.
Several devices have been designed to treat ischemic heart injury by placing a pumping balloon into the ascending portion of the aorta near the left and right coronary artery ostiums. Karcher et al. (U.S. Pat. No. 4,697,574) disclose a device that includes a propulsion balloon and a obturation balloon. The obturation balloon is placed upstream from the left subclavian artery, left common carotid artery, and brachiocephalic trunk to block the flow of blood during diastole. The propulsion balloon is placed in the space created by the obturation balloon and the heart valves, and is a simple rounded balloon designed to be inflated during diastole, decreasing the volume within the ascending artery and thus forcing oxygenated blood into the coronary arteries. The Singh (U.S. Pat. No. 4,785,795) invention is a modification of the Karcher et al. (U.S. Pat. No. 4,697,574) device, the Singh invention having an elongated balloon that can be used at a higher pumping frequency. Finally, there is a balloon device called SUPERCOR.TM. (ABIOMED.TM., Inc.) used to displace blood in the ascending aorta and thus, improve coronary diastolic blood flow.
Although an improvement on the prior state of the art, the Singh and Karcher et al. devices are limited to applying pressure upon the blood already within the space created by the blocking balloon and the heart valves. The present invention is an improvement on the prior art in that it incorporates the advantages of supplying an extra pulse of oxygenated blood to the coronary arteries through a blood flow control means, while closing off the blood flow from the ascending aorta and creating a high pressure region in the ascending aorta.