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External counterpulsation has developed over the past 44 years. It has now become a practical way to increase blood flow to the ischemic myocardium and other organs throughout the body. While it may seem that the theoretical benefits of external counterpulsation are evident, this non-invasive method for treating coronary artery disease had been eclipsed by other technologies until the past few years. The first systems built and tested used water as the compression medium and produced mixed results, however, when augmentation was positive, good results were observed.
Kantrowitz and Kantrowitz first described the principle of "phase shift" diastolic augmentation. Soroff, et al, related this principle to the oxygen consumption difference between flow work and pressure work by the heart. It was this understanding that eventually led to the concept of a mechanically induced counterpulsation to provide assistance to patients with low cardiac output syndromes. Direct counterpulsation techniques first developed by Harken and associates at Harvard resulted in femoral cut-down and external pulse actuation. The technique withdrew and then returned the blood to the arterial system. Studies documented increased coronary flow, decreased coronary AVO2 difference and reduced left ventricular pressure work.
During the early 60's, laboratory studies with animals demonstrated the potential efficacy of counterpulsation as a treatment following coronary occlusion. Jacobey and associates* provided the first evidence that counterpulsation could quickly enhance the development of coronary collateral circulation. It also suggested the possible clinical application of counterpulsation to the treatment of patients with coronary insufficiency and Angina. During this same period at Harvard, Birtwell and Clauss (1) produced counterpulsation by introducing a catheter with a balloon into the ascending aorta via the femoral artery. The Intra-aortic Balloon Pump was thus invented. This approach has found clinical application in support of circulation during and after cardiac surgery and in cardiogenic shock.
During the late 1960's, scientists at the National Institute of Health believed that results could be improved if the blood was moved from the lower limbs in a sequential manner. The development and testing of sequenced systems determined that they achieved greater cardiac output and increased the ratio of diastolic to systolic pressures. (1) Jacobey et. al, 1971, Birtwell et. al., 1970
During the 1970's a great deal of study was done on external counterpulsation. Among the distinguished physicians and scientists publishing on this subject were:
Among those scientists was a group at the Cardiassist Corporation in the Chicago, Illinois area. The team developed a sequenced hydraulic device called CardiAssist. Many years of study (2) and development went into this device. A large multi-center study involving 258 myocardial infarction patients in 25 institutions was undertaken in the late 1970's. (2) Amsterdam et. al., 1980
Results from the 25 institution, 258 myocardial infarction patient, multi-center study* using the Cardiassist device (published in 1980), indicated those patients receiving therapy within the first 24 hours after admission had a mortality rate of 6.5% versus 14.7% in the control group. Zheng and associates* at Sun Yat Sen University in China, reported their studies with a newly designed sequenced pneumatic system which produced excellent results. In trials, effects of the sequenced system were studied producing long-term symptomatic relief from chronic Angina. These favorable results caused numerous U.S. scientists to rethink their approach to external counterpulsation. Cardiomedics, Inc. was incorporated under the laws of the state of Nevada on August 25, 1986. On August 29, 1986, the Company acquired the assets of CardiAssist Corporation. CardiAssist Corporation had been engaged in the development and testing of earlier versions of the Company's external counterpulsation system, which it had acquired from Medical Innovations, Inc., one of the original developers of external counterpulsation at Harvard/MIT. Cardiomedics owns patent, manufacturing and marketing rights to CardiAssist™, a non-invasive, external counterpulsation therapy for patients with coronary artery disease. Since its inception, the Company has been engaged in development and marketing of its CardiAssist™ System. In September of 1987, the Company was the first to receive 510(k) marketing clearance from the FDA for its external counterpulsation system. * Amsterdam et. al., 1980, Zhang et. al, 1983
The Zheng device from China was used extensively at State University at Stony Brook, New York. Studies were performed and published by Lawson and Associates in 1992, 1993, 1995, 1997 and 1998. A New York based company began importing the Chinese device in 1995 following the FDA's clearance to market based on substantial equivalence to the CardiAssist™ device. In order to expand the number of indications and knowledge base regarding
ECP, Cardiomedics intends to conduct a minimum of 3 Multi-Center studies
beginning in 2002. |
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Also in the 1960's, several scientists were involved in the evolution of
counterpulsation to a completely non-invasive technique using externally
applied pressure generated by hydraulic systems. The system used various
materials to encase the patient's lower extremities. It then compressed the
vascular bed, displacing arterial and venous blood centrally. Though these
devices were somewhat primitive, several studies demonstrated the potential
of this approach to increase survival in patients with myocardial infarction
and cardiogenic shock as well as relief of