Among the medical procedures performed by cardiologists is the angiographic examination of a patient's coronary arteries and treatment of those arteries by angioplasty to dilate or remove obstructions (stenoses) in the coronary arteries. The coronary arteries, which branch off the aorta, carry oxygenated blood back to the heart muscle itself to nourish and sustain the heart muscle (myocardium). The angiographic examination of the coronary arteries involves a brief injection of radiopaque contrast liquid. During the interval that the radiopaque contrast liquid is in the coronary arteries, the patient is observed under X-ray fluoroscopy. The radiopaque contrast liquid provides an X-ray image of the shape and anatomy of the patient's coronary arteries under investigation. Once the shape and anatomy of the coronary arteries, and the presence and nature of the stenosis has been determined, a balloon dilatation catheter or other type of angioplasty catheter is advanced to the site of the stenosis to dilate that portion of the artery or to remove the stenotic material.
In brief, the coronary angioplasty procedure involves the use of several catheters, guidewires and related devices. Initially, a guiding catheter is inserted percutaneously into the patient's arterial system, usually by a percutaneous puncture made in the femoral artery in the groin. The guide catheter is advanced, with the aid of a guidewire, upwardly through the patient's aorta to the region of the heart. The distal end (the end inside the patient) of the guide catheter is specially formed so that when it is disposed in the region of the heart, it will assume a shape that facilitates placement of the distal outlet tip of the catheter at the entrance to (the ostium) one of the two main coronary arteries. Typically, the distal tip of the guiding catheter will enter the ostium very slightly so as to be securely positioned. Once the guiding catheter has been so positioned, it provides a direct path for the subsequent balloon dilatation or other angioplasty catheters that are intended to enter into the coronary arteries to treat the stenosis.
In addition to providing a direct path to the entrance to the coronary arteries for purposes of inserting and removing angioplasty catheters, guidewires, and the like, the guide catheter also provides a means by which radiopaque contrast liquid may be injected into the coronary artery. Such injections and fluoroscopic examinations may be performed a number of times during an angioplasty procedure in order to examine and monitor the progress of the angioplasty treatment.
Conventional use of guide catheters in angioplasty and angiographic catheters in diagnostic procedures presents several problems. Among them is that when the distal tip of the catheter is firmly engaged with a narrowed coronary ostium, the catheter itself obstructs the flow of blood from the aorta into the coronary artery. It is necessary, of course, for blood to continue to flow into the coronary artery in order to nourish the myocardium and, for that reason, some catheters are provided with one or more side holes near the distal tip of the catheter by which blood can flow from the aorta through the side hole and the distal tip of the catheter into the coronary artery. The presence of such side holes, however, impairs the delivery of radiopaque contrast liquid to the coronary arteries. It is desired that the contrast liquid be injected into the coronary artery quickly and at a relatively high concentration so that the contrast liquid will spread throughout the coronary artery tree and remain in sufficient concentration to present a clear fluoroscopic image. If the concentration of contrast liquid is too low, the image may be weak and inadequate. When radiopaque contrast liquid is injected through a guide catheter having side holes, a significant portion of the contrast liquid may be emitted through the side holes and into the aorta, rather than into the coronary artery. Consequently, the flow rate and concentration of radiopaque contrast liquid entering the coronary artery is significantly reduced. In order to assure that there is a sufficient concentration of contrast media for sufficient visualization of the artery, typically it is necessary to increase the amount and injection rate of the contrast liquid. This results in injection of a significantly increased amount of contrast media into the patient's body which may have a detrimental effect on the patient.
There is a need, therefore, for cardiovascular catheters including guiding catheters and angiographic diagnostic catheters and other interventional cardiovascular catheters that enable flow of blood from the aorta into the coronary artery even while the guide catheter is intubated in the coronary ostium without impairing the ability of the guide catheter to deliver quickly contrast liquid in desirably high concentrations. There is also a need for interventional cardiovascular catheters possessing similar capabilities. It is among the general objects of the invention to provide such a guide catheter.