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Pacemakers: missing the beat

MagazineFebruary 2002 (Vol. 12 Issue 11)Pacemakers: missing the beat

As 1999 lurched to an end, many people dependent on machines and computers held their breath and waited for the stroke of midnight, when the millennium bug - a malfunction of computer chips not programmed to recognise the change of the century - would strike, causing major microchip havoc

As 1999 lurched to an end, many people dependent on machines and computers held their breath and waited for the stroke of midnight, when the millennium bug - a malfunction of computer chips not programmed to recognise the change of the century - would strike, causing major microchip havoc. Among those holding their breath were people with cardiac pacemakers, electrical devices that keep the heart beating regularly.

The question was: would the more than one million people in the West who depend on these gadgets suddenly experience mass heart failure at the dawn of the new century?

In the end, the bug was a bust and pacemakers continued to function as normal, but the anxiety brought home some difficult questions about what happens when the human body becomes reliant on internal computers to keep it alive.

Cardiac pacemakers are a mechanical solution to irregular or uncoordinated heartbeats - otherwise known as arrhythmias. Broadly speaking, an arrhythmia is a disturbance in the orderly beating of the heart. But the term arrhythmia itself is not a true diagnosis, since arrhythmias can be caused by so many different things (see box below). There are literally dozens of different types of arrhythmias and they range from the trivial to the potentially life-threatening.

Arrhythmias can be slow (bradycardia) or fast (tachycardia) or describe the occasional extra beats of the heart. When the heartbeat is too slow, either a standard pacemaker attached to one chamber of the heart, or a dual-chamber pacemaker that is attached to two chambers, may be recommended. When the heartbeat is too fast, a similar device called an implantable cardiac defibrillator (ICD) may be used.

In some cases, the condition is so severe that implantation of a pacemaker is a lifesaver. And while there is no doubt that some people experience a better quality of life with pacemakers, underneath the success story, there are also problems.

Chief among these are the number of potentially unnecessary pacemakers implanted in people throughout the world. Consumers might never have known about this had it not been for a scandal that broke out in the US in the 1980s. A concerned doctor in Colorado blew the whistle on a pacemaker salesman who was offering surgeons $500, as well as a variety of other 'incentives' such as trips abroad, every time they removed a competing company's unit from a patient and replaced it with the one the salesman was promoting. This led to a congressional investigation involving 400 salespeople, some of whom were making more than $1 million a year.

Expensive surgery, such as cardiac surgery, has been known to be used as a substitute for medical care without necessarily resulting in better outcomes or higher survival rates (N Engl J Med, 1985; 313: 1206).

In a landmark study, Greenspan and colleagues studied the medical charts of 382 patients who had pacemakers implanted at 30 hospitals in Philadelphia County in 1983. They found that 20 per cent of the implants were not medically necessary and that a further 36 per cent of implants were questionable because of inadequate documentation or diagnostic evaluation (N Engl J Med, 1988; 318: 158-63). In other words, less than half the pacemakers implanted were clinically justified.

This fact is even more startling when you consider that the majority (70-80 per cent) of pacemaker recipients are elderly, aged 65 plus (J Am Geriatr Soc, 1999; 47: 1125-35). This is an age group in which surgery can be more risky and where arrhythmias may, in some instances, be better managed with carefully considered drug therapy and lifestyle changes.

Pacemakers also have little to offer in terms of patient longevity. A study of 1,647,955 individuals over 65 who died in the US in 1993 underlined this point (J Am Geriatr Soc, 1998; 46: 1396-400). Among them, 78,941 had pacemakers, 18 per cent (14,158) of which were implanted in the last year of life. The estimated survival time after pacemaker implantation was five months. Also, although the causes of death were not directly related to the pacemaker, the rate of death from acute disorders was 49 per cent in the pacemaker group compared with 19 per cent in the matching general population.

Those with pacemakers still succumb to sudden heart failure at a rate of 1-2 per cent per year, with a cumulative incidence of death of around 10 per cent at five years (Ann Intern Med, 1988; 109: 529-34; J Am Coll Cardiol, 1989; 13: 1353-61; Circulation, 1993; 88: 1083-92). The rates are even higher among those with more severe heart problems (Am Heart J, 1992; 124: 1608-10; Circulation, 1992; 85: 1304-10).

>From the patient's perspective, surgery is always an aggressive solution. But implanting a pacemaker has become an easy option for physicians. It's quick, it's relatively easy to do and it requires fewer follow-ups than when a patient is put on drugs (Pacing Clin Electrophysiol, 1996; 19: 1219-24). There are no pills to take, no schedules to maintain and no associated side-effects, and the rate of patient compliance is high because the patient rarely has to do anything except consent to surgery. This would appear to make a strong case for the use of pacemakers. However, although in theory the pacemaker should do the job with-out a need for drugs, a significant number of patients go on to have both the pacemaker and the drugs.

The production line
The heart is a muscle with four chambers: the right and left atria form the upper portion while the right and left ventricles form the lower part. In a healthy heart, the body's own natural cardiac pacemaker, the sinoatrial (SA) node, emits small electrical currents which prompt each of these chambers to contract simultaneously to pump blood around the body.

A pacemaker is made up of a generator that produces an electrical signal and a lead that attaches to the heart to take over the job of the SA node. It is usually attached to standard locations - either on the right side of the heart or, with dual-chamber pacemakers, on both lower chambers.

But a recent small study suggests that implanting the device in a production-line manner, without considering where the patient needs it most, can mean that it functions less efficiently (which may explain why some patients still need drugs to support the work of the pacemaker).

In a study of 18 patients with dilated cardiomyopathy (DCM) - a potentially fatal form of heart failure in which the heart's main pumping chambers (the ventricles) are stretched and weakened - researchers at Johns Hopkins in Maryland found that placing the electrode on the right ventricle had no benefit and placing it on both ventricles yielded only a 13 per cent improvement in pumping action. But placing a pacemaker at the area of the heart which is most out of synch improved the heart pumping action by around 25 per cent (Circulation, 1999; 99: 1567-73).

Infections and more
More serious complications can occur, often within three months of pacemaker implantation; in 11 per cent of cases, further surgery is required to correct the problem (Pacing Clin Electrophysiol, 1999; 22: 711-20).

The majority of pacemakers are transvenous - the leads going from the device to the heart are inserted into a vein via an incision below the collarbone. Among the most serious of the problems that can occur is venous obstruction. Several case reports have documented thromboembolic complications related to pacemakers (Cardiology, 2000; 93: 142-8). In a 10-year study in India of 6256 patients, 25 had symptoms of venous obstruction such as pain, swelling or dilated superficial veins in the face, upper limbs or upper chest. This represents an occurrence rate of nearly four per 1000, much higher than the usually quoted one per 1000 (Indian Heart J, 2000; 52: 431-3).

Overall, around 10 per cent of pacemaker leads may either fail or become infected. But removal of old leads isn't always successful, and the chances of removal failure increases with each year the lead has been in place (Pacing Clin Electrophysiol, 1999; 22: 1348-57).

Because of the complications and the need for a high level of competency on the part of the surgeon, many leads - particularly if they have failed rather than become infected - are simply left in the body and a new one inserted elsewhere. However, five per cent of those left in the body lead to problems such as venous occlusion and infection (J Interv Card Electrophysiol, 2000; 4: 493-9).

Indeed, pacemaker lead infection is becoming more common and is a potentially serious complication (Arch Mal Coeur Vaiss, 1998; 91: 753-7). Several causal organisms have been identified, including several species of Candida (albicans, glabrata and tropicalis), Staphylococcus epidermidis, which can grow on plastic, and S. aureus (J Infect, 2000; 41: 275-6, 176-8; Heart, 1999; 81: 88-91; Pacing Clin Electrophysiol, 1996; 19: 1105-11). Such infection can often lead to endocarditis, a potentially fatal inflammation of the heart membrane.

Even when a lead is infected, some doctors recommend antibiotic treatment rather than lead removal. However, in one 1998 US study examining the treatment options for infected leads, antibiotic treatment failed in 100 per cent of cases and even resulted in two deaths. The authors concluded that removal of the infected leads was absolutely necessary for successful treatment (Ann Thorac Surg, 1998; 65: 596-7).

Equally worrying is the possibility of the development of breast cancer. One case study has shown a potential link with the development of breast cancer near the site of implantation (Kyobu Geka, 1999; 52: 496-9). In the UK, two women developed breast malignancies around the site of 'migrated' pacemaker generators. Given other reports of such cases in the literature, the authors noted that whether this is more than just a coincidence has yet to be determined. But, as yet, there is little large-scale research conducted to test the hypothesis (Postgrad Med J, 1993; 69: 883-5).

The body-machine
Western technology sees the body as a machine that can be repaired by other machines. But such a view can be the source of considerable emotional trauma. When your life depends on the correct functioning of a machine, the psychological impact may be considerable. The heart, in particular, has profound psychological associations (Pacing Clin Electrophysiol, 1990; 13: 399-404).

Changing the language by referring to 'pacemaker therapy' rather than to 'surgery' or 'device' hasn't altered the sometimes considerable emotional impact of having a pacemaker implanted. Psychoemotional problems such as depression, anxiety, a loss of energy and hypochondria have all been reported (Pacing Clin Electrophysiol, 1997; 20: 1628-32; Int J Psychiatr Med, 1976; 6: 359; Heart Lung, 1986; 15: 93-100; Ann Med Psychol, 1990; 148: 110-2).

Another challenge to implanted patients is 'pacemaker panic' which, say researchers, includes feelings of physical deterioration and concerns about being dependent on a mechanical device for life support (Am J Cardiol, 1972; 30: 705).

These pacemaker challenges have led to a syndrome dubbed 'pacemaker twiddler's syndrome'. Recently, this has been documented among recipients of ICDs as well (PACE, 1990; 13: 1073-4; Am Heart J, 1992; 123: 1079-82). In this syndrome - which has been documented since the 1960s - the recipient either consciously or unconsciously, deliberately or inadvertently, fiddles with and twists the device - which is accessible as it is implanted just under the skin of the chest or the abdomen - so as to dislodge the electrodes and cause the device to 'malfunction' (Can Med Assoc J, 1968; 99: 371-3; Ann Emerg Med, 1994; 23: 136-8).

The fact that these devices are not guaranteed, but come instead with a 'limited warranty', may also create concerns with malfunction, a concern that becomes even more heightened with the increasing number of device recalls (J Cardiovasc Nurs, 1991; 5: 65-76; Owen P, Implantable devices, in Riegel B, Ehrenreich D, Psychological Aspects of Critical Care Nursing, Rockville, MD: Aspen, 1989: 171-86).

A recent study into the frequency of recalls and safety alerts for cardiac devices made for disturbing reading (JAMA, 2001; 286: 793-9). The authors reviewed all weekly US Food and Drug Administration enforcement reports from 1990 to 2000, looking for news of pacemaker and ICD malfunctions. The enforcement reports include device failures discovered by manufacturers during their own monitoring programmes as well as other recalls and safety alerts.

The reviewers found that the number of patients in the US living with implanted devices increased by 49 per cent over the 10-year study period. Around 600,000 individuals have pacemakers and 150,000 have defibrillators. Of these, more than 520,000 permanent pacemakers and ICDs were subject to recalls or alerts (called advisories) between 1990 and 2000, with recall rates rising most sharply since 1995. Most of these safety alerts were because of manufacturing defects, component failure, poor design, electrical or circuitry problems, and battery failures. This, say the authors, translates into advisories affecting around one in 15 persons with pacemakers and one in six of those with ICDs.

While not all such safety alerts result in repeat surgery, a significant number does. At any rate, pacemakers are not meant to work indefinitely. Most will last only between five to seven years, with 10 years considered the longest amount of time a person can go without having the pacemaker replaced. In one study of adverse events related to dual-chamber pacemakers, only 46 per cent remained malfunction-free over a five-year period (Pacing Clin Electrophysiol, 2000; 23:1010-3).

The treatment of arrhythmias has changed in recent years, with pacemakers becoming the 'therapy' of choice, especially for elderly individuals. These devices, however, often do not work with machine-like precision (Z Kardiol, 1996; 85: 237-47) and can be associated with serious complications. Clearly, any patient offered the opportunity of a pacemaker should seriously consider any other options before agreeing to the procedure.

Pat Thomas


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