IMPLANTABLE MECHANICAL SYSTEM
FOR ASSISTING BLOOD CIRCULATION
FIELD OF THE INVENTION 5
The instant invention relates to a muscle-powered implantable mechanical system for circulatory blood pumps providing a combination of means constituting a prosthesis powered by the skeletal muscle of the patient, for an 10 implantable pump for assisting in chronic refractory heart failure.
BACKGROUND OF THE INVENTION—PRIOR
Treatment of end-stage chronic heart failure (CHF) is still a major challenge for physicians. This is the reason why scientists all over the world have been devoted for many years to the development of mechanical aid systems for blood circulation. Thus, in 1960 Kolff and coworkers, Liotta 20 and coworkers and other researchers developed a series of devices for managing acute heart failure.
On Jul. 18, 1963, for the first time, Liotta et al employed a left ventricular assisting device for the treatment of a 25 patient with acute cardiac disfunction during the postoperative period.
On Apr. 4, 1969, and for the first time in the medicine history, Cooley, Liotta et al implanted a total artificial heart in a patient, thus bridging the two-stage cardiac transplan- 30 tation.
This technique expanded worldwide and was then employed by a large number of clinical centers; such that it may be affirmed that mechanical devices for aiding blood circulation, used as a bridge in cardiac transplantation are at 35 present a general medical practice.
However, the main challenge of modern cardiology: the management of end-stage chronic heart failure (CHF) remains unsolved.
The mortality among CHF patients is reported to range 40 between 10% and 20% a year; i.e. 200,000-400,000 deaths a year are caused by CHF in the United States.
On the other hand, if worldwide deaths are considered, due to the same causes, the number of deaths may range from 1,000,000 to 2,000,000 per year.
Also, there are regions in which additional negative factors area added to these diseases.
This is the case of South America, in which chagasic cardiomyopathy patients due to South American Trypnoso- 50 miasis (Chagas disease), cause that from 18 to 18 million people worldwide are likely to be infected by Trypanosoma Cruzi. 30% to 40% of those persons infected will ultimately have some degree of cardiac involvement.
In Argentina, from 250.000 to 400,000 patients suffer 55 from chagasic cardiomyopathy. Chagasic patients cannot be selected for cardiac transplantation; very shortly the T. Cruzi will be invading the heart silograft.
Several researchers have developed devices for long term treatment of CHF. Thus, 60
Pierce et al have disclosed a DC brushless motor-driven total artificial heart.
Portner & associates have developed an electrically powered solenoid energy converter coupled to a dual $5 pusher-plate sac type blood pump.
A belt skin transformer providing transmission of primary
power across the intact skin during a short period of time.
White tested thermal powered systems comprised by a Stirling engine/hydraulic converter attached to a ventricular assisting device. Liotta et al used a DC brushless motor-driven single pusher plate at an animal laboratory at the early days of artificial heart research; etc. The disadvantage common to these devices is the need of requiring a power source external to the body, through a percutaneous access port.
The life quality is severely restricted and patients are subject to serious complications, such as infections.
Further, the transmission of electrical power through intact skin requires permanent care of the recharging of internal batteries.
Works on remodelling the outstanding properties of skeletal muscle plasticity have lead cardiomyoplasty to treat CHF in man.
The pacing of skeletal muscle grafts with a train of pulses from a muscle stimulator may transform a high power but fatigable skeletal muscle into a somewhat lower power but fatigue-resistant muscle which matches cardiac muscle's work output on a gram-per-gram basis.
Further, the concept of using the autologous skeletal muscle for cardiac assistance is not new, although former attempts had characteristics and features different from those of the instant invention.
In this respect, the first documented attempt was disclosed by Adrian Kantrowitz. Kantrowitz wrapped the left hemidiaphargm of a dog to a segment of the descending thoracic aorta and stimulated diaphragm contraction during diastole.
Apart from dynamic cardiomyoplasty, Stephenson et al reported on the use of muscle energy as an aid in blood pumping. Thus, the Latissimus dorsi muscle is detached from all of its insertion and is wrapped around a conical mandrel to create a ventricular-like shaped skeletal muscle pouch.
Furthermore, Chiu et al have developed a skeletal musclepowered implantable chamber counterpulsator.
Liotta et al have reported the concept of the advantages of the natural linear contraction of the skeletal muscle thus avoiding a major anatomical disruption.
Spitzer proposed the lower insertion of the rectus femoris muscle and attachment thereto to a 200 ml piston implanted in the thigh.
Contraction of the rectus femoris muscle creates physiological pressures capable of driving an artificial heart in the chest.
Ugolini reported that a fluid energy collector should be capable of storing energy from the contraction of the psoas major muscle and transferring it by a hydraulic conduit to an artificial heart pump.
Farrar and Hill disclosed a muscle-powered two-stage mechanical to hydraulic energy convector which could be applied to a circulatory blood pump.
At the animal laboratory (dogs and calves), Ltotta et al reported on physiological studies concerning the linear-pull force and displacement of the LD muscle.
An endogenous source of power employing skeletal muscle for cardiac aid devices is of great advantage. Problems related to the use energizing systems (electrical, pneumatic, hydraulic) outside the body are thus avoided.
SUMMARY OF THE INVENTION
The instant invention proposes to use the mechanical force of the Latiesimus dorsi muscle in its linear pull for maximum efficiency.
The surgical process, which will be described in detail