History

Development and Progress of Counter pulsation
The evolution of counter pulsation techniques has been driven by the need to improve the technical performance of equipment, and by the need to explore and demonstrate success in clinical applications.Early research used direct counter pulsation techniques first developed by Harken and associates at Harvard in the late 1950's. Through femoral cutdown and external pulse actuation, this technique withdrew and then returned the blood to the arterial system. In a number of studies this direct technique was used to document increased coronary flow, decreased coronary AVO2 difference, and reduced left ventricular pressure work.

In the early 1960's laboratory studies with animals demonstrated the potential efficacy of counter pulsation as a treatment following coronary occlusion. This finding provided the first evidence that counter pulsation could quickly enhance the development of coronary collateral circulation, suggesting the possible clinical application of counter pulsation to the treatment of patients with coronary insufficiency and angina. While promising, it was also evident that the requirement for femoral cut down and hemolysis caused by this technique severely limited the clinical usefulness of this invasive approach.

Also at Harvard, during this same time period, Birtwell and Clauss, produced counter pulsation by introducing a catheter with a long slender balloon into the ascending aorta via the femoral artery (Intra-aortic Balloon Pump [IABP]). Saline was pumped in and out of this basoon by means of the cournterpulsing actuator. There have been continuing developments in the design of the IABP and its inflation/deflation techniques, and, although surgical insertion is still required, this approach has found clinical application in support of circulation during and after coronary surgery and in cariogenic shock. IABP offers advantages over direct counter pulsation in that its effects are created close to the aorta, and the hemolysis associated with direct counter pulsation is avoided.

In the mid 1960's, several scientists were involved in the evolution of counter pulsation to a noninvasive technique using externally applied pressure generated by hydraulic systems. These systems used various devices to encase the patient's lower limbs and compress the vascular bed displacing arterial and venous blood centrally.Although these early external counter pulsation devices were somewhat primitive, studies with them demonstrated the potential of this approach to increase survival in patients with myocardium infarction and cryogenic shock, and in relief of angina pectoris.

As the evolution of noninvasive external counter pulsation devices progressed, hydraulic systems were replaced with pneumatics, and redesign of compression elements sought to improve results and patient comfort. Clinical applications of this modality, beyond cardiac or circulatory assistance in acute conditions, were also explored with varying degrees of success. In a 1986 review of the progress of external counter pulsation, Soroff and associates reported that mixed results of clinical trials with these systems were owing to technical difficulties with the equipment.

All of the external counter pulsation systems used in studies before the 1970's employed "nonsequenced" pulsation - that is, compression of the vessels was performed simultaneously along the full length of the compression element.During the late 1960', scientists at the National Institutes of Health suggested that results could be improved if blood was expressed from the extremities in a sequential manner. Development and testing of these "sequenced" systems determined that they achieved greater cardiac output and increased the ratio of diastolic to systolic pressures than did nonsequenced systems.

During the 1970's, Zheng and colleagues at Sun Yat Sen University in China, reported on their studies with a newly designed sequenced pulsation system that used four sets of compression bladders on the patient's legs, buttocks, and arms. In these trials, effects of the sequenced system were studied in patients with angina pectoris and acute myocardial infarction. In more than 90% of the 200 patients with angina pectoris, this device provided long-term symptomatic relief with minimal relapse.

These same investigators also compared the hemodynamic effects of sequenced and nonsequenced compression, and various configurations of compression devices in healthy volunteers and patients with coronary heart disease. Results confirmed that sequenced systems were far more effective in raising diastolic pressures.

Favorable results reported by Chinese investigators, led scientists at the Health Sciences Center at the State University of New York at Stony Brook, to reassess the efficacy of this modality in the treatment of patients with chronic angina pectoris. Their studies, which included patients with sub acute pectoris refractory to other medical intervention and with evidence of myocardial ischemia, were performed using a newly developed and "enhanced" counter pulsation system. Designated EECP - Enhanced External Counter pulsation, the system employs a three-cuff compression configuration and sophisticated computerized control of the inflation/deflation sequence. It has been studied for its ability to provide both short-term and sustained relief of symptoms of angina pectoris, and to provide sustained improvements in perfusion of ischemic areas of the myocardium.

• Kantrowitz brothers in 1953

The state-of-the art angina treatment has evolved from a principle described in 1953 by the Kantrowitz brothers at Harvard. The phase-shift, diastolic augmentation principle, led to a better understanding of the myocardial oxygen consumption differences between "flow work" and "pressure work."

This new understanding on improving blood flow to the ischemic myocardium by increasing coronary perfusion became the research objective.Many attempts were made to develop effective means of providing mechanical cardiac assistance for patients with low, cardiac output syndromes.

One of the first techniques developed was the Intra-Aortic Balloon Pump (IABP). The IABP consists of an inflatable balloon catheter that is inserted into the femoral artery and advanced to the descending aorta. Modified and refined over the last 40 years, this device remains a primary therapy for assisting the heart function of patients in cardiogenic shock.

• Soroff, Birtwell, and others at Harvard in the mid-60s

In the mid-60s, Soroff, Birtwell and others at Harvard developed a device for external counter pulsation. It was a hydraulic system that pumped water in and out of cuffs applied to the lower extremities. It was clear that Soroff and Birtwell's device had advantages over the IABP. It was noninvasive, and also increased venous return as it boosted coronary perfusion pressure.

Though cumbersome, this early hydraulic device increased survival rates of patients with acute myocardial infarction and cardiogenic shock and relieved angina. However, in the United States, external counter pulsation was eclipsed by the emergence of coronary bypass surgery and angioplasty

While physicians in the United States turned their attention to these dramatic new developments in invasive treatments, physicians in China adopted the concept of external counter pulsation and refined the technology. Treatment was made easier to administer and more comfortable for patients by using pneumatic cuffs instead of hydraulic cuffs.

• Researchers in the 1970s and Late 1980s

In the 1970s, a group of researchers, led by Dr. Zeng Sheng Zheng at the Sun Yat-sen University of Medical Sciences in the People's Republic of China, began to develop more sophisticated counter pulsation systems. They devised a system in which the pneumatic cuffs inflated sequentially, not simultaneously as they had before.

The Chinese researchers in collaboration with researchers at the State University of New York at Stony Brook continued to refine the technique of external counter pulsation. In 1989, researchers at Stony Brook began clinical studies of enhanced external counter pulsation (EECP) treatment. These studies demonstrated that the treatment produces a number of positive effects that are maintained for at least three years after a full course of treatment.

Multi-center clinical trials have confirmed the Stony Brook results. The trials also showed the extent of treatment benefit with greater accuracy, determined the patients who gained the most from treatment, and measured the effect of treatment on medication requirements, exercise capability, and quality of life.

EECP treatment has evolved and is being used with no reported complications as an outpatient treatment of chronic angina patients. References to the treatment appear in medical literature and are presented at medical conferences. EECP treatment does not require the adoption of new medical practices; it is an improvement of existing medical practices made possible by the advanced technology of a new delivery system.