The concept of providing counter-pulsation support for the failing heart has been known since the pioneering work of Kantrowitz. Counter-pulsation causes displacement of a volume of a patient's blood in the patient's aorta while the patient's heart is dilating in diastole and after the aortic valve has closed. This assists to move blood around the patient's peripheral vasculature as well as into the coronary arteries. The timed volume displacement in the aorta on the blood within the aorta just in advance of systolic ejection of blood from the heart reduces the afterload on the heart, by causing a transient low pressure above the aortic valve.
It is known from the use of counter-pulsation in Intra-Aortic Blood Pumps (IABPs) that counter-pulsation can provide short term support for the failing heart. These devices require a balloon to be inserted percutaneously into the descending aorta. The balloon is inflated and deflated in counter-pulsation with the heart by the transmission of a gas, usually helium, between the balloon and a bedside console. These devices suffer from the problem that there is a high risk of thrombo-embolism if the balloon remains in the vasculature for a prolonged period, which can lead to ischemic leg complications.
There have been a number of attempts to provide counter-pulsation support for the failing heart by applying counter-pulsation pressure to the outside of the aorta. These proposals are contained in the following patent specifications:
PCT99/04833USA4,014,318USA4,583,523USA4,979,936USA6,030,336USA6,045,496A similar arrangement is described by Furman, New York Journal of Medicine, Aug. 1, 1970, pp 1964-1969. In all of these arrangements means are provided to surround, or at least substantially surround, the aorta and to apply a squeezing pressure substantially uniformly around the circumference of the aorta. The present inventors have found that there are substantial advantages if the counter-pulsation pressure is applied to only a part of the circumference of the aorta.
It is also known to resect a part of the aorta for the purpose of inserting a patch or other graft into the aorta and to cause such patch or graft to counterpulsate. Such a system is described in the following patent specifications:
PCT01/13974USA4,630,597
The device described in these specifications is for insertion into the descending aorta which is straight. There is no suggestion of how to deal with the more complex issues that arise in placing the device into the ascending aorta which is curved along its length.