Machines in Our Hearts: The Cardiac Pacemaker, the Implantable Defibrillator, and American Health Care

CHAPTER 7: The Pacemaker Becomes a Flexible Machine

CHAPTER 7 THE PACEMAKER BECOMES A FLEXIBLE MACHINE A succession of radical innovations in cardiac pacing broke up the brief era of stability that had begun in the late 1960s. New themes emerged: doctors’ uneasiness about the growing complexity of cardiac pacing, the public’s anxieties about the possible dangers of a lifesustaining technology, and broadly shared concerns about the growth dynamic of the field of pacing. These matters will occupy the next three chapters. The fact that these issues had moved to center stage by the middle and late 1970s indicated that the postwar era of unquestioning enthusiasm for new medical technology was coming to an end. In the 1970s, the device manufacturers drove technological innovation with some of the most important new features coming from small start-ups. Companies innovated partly to adapt the pacemaker to a wider range of heart-rhythm disorders, but also because innovation brought prestige to a company and helped it build its portfolio of patents; and because, through innovation , the industry avoided the commodification of the pacemaker. Manufacturers sought to balance several goals: meeting the expressed wants of their customers, displaying their virtuosity in design and manufacture, and continually reassuring the public that implantable pacemakers were safe and ‘‘friendly’’—all this in the context of evolving public attitudes about modern medicine and shifting government policies toward the device industry. Once a manufacturer had introduced a new pacemaker that included some significant novelty, doctors had choices to make. They could get acquainted with the new model and try to put its capabilities to work for their patients; they could avoid the new device; or they could treat it as if it were an older model by ignoring or underutilizing the new features. In this complex set of interactions between manufacturers and physicians, the uses of the pacemaker repeatedly came up for redefinition.1 A NEW DISORDER OF HEART RHYTHM By about 1970, manufacturers and pacemaker implanters had grown accustomed to working with noncompetitive pacemakers and transvenous leads. 162 MACHINES IN OUR HEARTS CPI’s Microlith-P Pacemaker and Model 2000 Programmer, 1978. The Microlith-P embodied the major innovations of the 1970s in cardiac pacing: hybrid circuitry, a longlived lithium battery, a hermetically sealed titanium shell, and noninvasive programmability for the rate and amplitude of the pacing stimulus. CPI offered a six-year product warranty on this pacer and emphasized that its Model 2000 programmer was easy for the busy doctor, nurse, or technician to set up and use. (Courtesy of Guidant Corp.) THE PACEMAKER BECOMES A FLEXIBLE MACHINE 163 Sudden device failures were becoming uncommon. After a decade of development , the field of implantable cardiac pacing had attained a measure of stability. At a pacing conference in November 1968, virtually every paper assumed that heart block remained the sole indication for permanent pacing. That same year, academic cardiologists began to discuss a new disorder of heart rhythm that they called sinus node disease, or the sick sinus syndrome (SSS). These names lumped together several known disturbances of the heartbeat involving default of the sinus node, the source of the electrical impulses that trigger atrial and then ventricular contraction—the heart’s natural pacemaker. If heart block is a failure to pass the heartbeat on from the atria to the ventricles, SSS is a set of disorders in the formation of the heartbeat.2 The sick sinus syndrome covered a diverse list of symptoms: persistent and noticeable slowdown of the firing rate of the sinus node; an inadequate pickup in the heart rate when a person became more active; sinus slowdown alternating with a rapid atrial rate. All could begin episodically but later become fixed. In more severe forms, the impulse might fail to spread beyond the sinus node. In the absence of their normal signal, the atria might fibrillate transiently or continuously and the ventricles might adopt a slow rate of contraction dissociated from the atria. Many elderly people have a bit of sinus bradycardia, and their hearts may not speed up as promptly or as energetically as the hearts of the young. These are mild symptoms of SSS. But investigators reported that some people experienced more troubling symptoms, such as dizziness, fatigue, transient blackouts, and organ failure. Most of the symptoms, however, were not unique to SSS and could vary greatly from one patient to another. The same patient could manifest a range of symptoms from one...