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The Development of Mechanical Circulatory Systems: “The Labors of Hercules”

A large variety of mechanical systems is now available to support patients with ventricular dysfunctions which include: profound heart failure, lethal ventricular arrhythmias, cardiogenic shock, stone heart or stunned myocardium, following surgery. Their introduction in the treatment of patients initiated some 25 years ago and the development of clinical experience in the past 10 years today permits a reevaluation of the real problems faced by clinicians and engineers, leading to the suggestion of a reorientation of clinical research and technological development for the coming years. These problems may be grouped into seven chapters, the seven labors, imposed on Hercules in order to gain immortality. The current experience in mechanical circulatory support may be grossly approached by analyzing the International Registry organized and updated every year by W. Pae and W. Pierce at Hershey. This Registry made up of voluntary reports is obviously not fully satisfactory per se. Nevertheless, it clearly shows that the systems have been used mostly as bridging devices either to the recovery of the native heart function (n = 1076 until 1992) or to a cardiac transplantation (n = 534). The overall success of the strategy is illustrated very simply by the number of patients actually being weaned off the device (46%) and the number of live patients being discharged from the hospital (25%) in the first group and by the number of patients being actually transplanted (67%) and becoming long term survivors (44%) in the second group. Analysis of risk factors points out the role of timing of the implantation, of severe associated organ dysfunction, of age and body weight and finally, in a few circumstances the role of the system itself: centrifugal pump assistance in patients unweanable off bypass offers the best chance for recovery. Implantable left ventricular devices allow a lower risk of transplantation. A second observation is related to the complications observed during the period of assistance. Problems related to thrombo-embolism or hemorrhage, to the natural evolution of the initial organ dysfunction and to infectious complications are by far the most critical issues, clearly reflecting the less than acceptable bio-compatibility of the materials. The almost unpredictable evolution of major organ dysfunction as restoration of an adequate arterial flow is achieved is another unsolved issue. This short summary of the current experience, which has been previously analyzed more extensively suggests that major efforts should be pursued in many different directions to allow a real significant change in the role of mechanical assistance in the wide armentorium of techniques available today in cardiology. These are at least seven major issues, requiring efforts as intense as the seven labors given to Hercules.