Development and Progress of Counterpulsation

Also at Harvard, during this same time period, Birtwell and Clauss, produced counterpulsation 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 counterpulsation in that its effects are created close to the aorta, and the hemolysis associated with direct counterpulsation is avoided.

In the mid 1960's, several scientists were involved in the evolution of counterpulsation 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 counterpulsation devices were somewhat primitive, studies with them demonstrated the potential of this approach to increase survival in patients with myocardium infarction and cariogenic shock, and in relief of angina pectoris.

As the evolution of noninvasive external counterpulsation 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 counterpulsation, 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 counterpulsation 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 subacute pectoris refractory to other medical intervention and with evidence of myocardial ischemia, were performed using a newly developed and "enhanced" counterpulsation system. Designated EECP - Enhanced External Counterpulsation, 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.