With the progress of medicine, new treatments have positively been attempted to apply to various cases, wherein to save patients by conventional treatments is difficult, and many good results have been obtained. Among them, regarding treatments for heart diseases such as cardiac infarction, valvular disease of the heart and the like, the saving rate of patients has significantly been improved by development of pharmacotherapy as well as technical improvement in cardiotomy due to the progress of pump-oxygenators and cardiomuscular protection. Further, for patients suffering from depression of heart function, circulation assisting devices such as intra-aortic balloon pumping (hereinafter abbreviated as "IABP"), veno-arterial bypass (hereinafter abbreviated as "VAB") and the like have been developed and it is possible to assist heart function for several days to several weeks. IABP is used for assisting heart function by inserting an elongated balloon into the aorta from the femoral artery and inflating and deflating the balloon in the aorta. VAB is used for draining (or drainaging) venous blood from a patient, oxygenating the blood by an artificial lung and returning the oxygenated blood to the patient by a pump. However, even IABP and VAB are yet insufficient for assisting heart function and, therefore, some patients cannot be saved by IABP and VAB. For such patients, a systemic heart assisting artificial heart having larger efficiency for assisting heart function is used in the clinical field. Such a systemic heart assisting artificial heart is used by inserting a draining cannula in the left atrium during thoracotomy, connecting a blood prefusion cannula to the aorta and connecting both cannulas to the inlet and outlet of a blood pump placed outside the body, respectively and driving the pump to assist heart function. For the systemic heart assisting artificial heart, the shape and insertion site of the cannula upon draining from the left atrium are of importance. Because of its nature, the device is requested to assist heart function for several days. During this period of time, the chest is closed and only the cannulas penetrate the wall of the chest to protrude outside the body. Therefore, when the cannulas oppress the heart or other organs, sufficient dehematization cannot be obtained. Further, the oppressed organs are adversely affected and, therefore, shape fitness for the living body is more important in comparison with that of cannulas used in ordinary cardiotomy.
For this purpose, the cannula should have an enough diameter for obtaining shape fitness for the living body as well as sufficient draining and, therefore, a special shape is required. In view of this, one cannula for the assisting artificial heart is proposed in Japanese Patent Kokai No. 58-177664.
One key problem which is usually encountered with in the use of the assisting artificial heart is that to fit and remove the device require much time and labor. The assisting artificial heart is fitted by inserting a draining cannula and a blood perfusion cannula under extracoporeal circulation with a pump-oxygenator after exposing the heart by thoracotomy. Therefore, it is difficult to use it for a patient requiring urgent treatment. Further, when the assisting artificial heart is removed after heart function is recovered, repair must be made after withdrawal of the cannulas by thoracotomy. This problem is not yet solved even by using the above cannula disclosed in Japanese Patent Kokai No. 58-177664.