talkhealth Blog

Many of our ICD patients will have seen recent newspaper articles with headlines from the USA such as this in The Daily Mail ‘Faulty pacemakers killing 2,000 a year: Third of unexpected deaths among patients thought to be caused by malfunctions’.  Most may have suspected that this headline may not be completely accurate, but wondered whether there is some truth behind the research by Dr Zian Tseng and anything to be concerned about.  The research from Dr Zian Tseng’s team suggests that we may not be detecting all pacemaker and ICD malfunctions.

All the media coverage was about Dr Zian Tseng’s research published in the Journal of the American Medical Association in June this year.  His team collected information over a 3 year period from 2011 to 2013 in San Francisco, USA.  During that time there were 517 people who suffered sudden cardiac deaths (SCD).  These are deaths that occur within 1 hr of becoming unwell if witnessed, or within 24 hrs if unwitnessed.  14 of the 517 people who died from SCD had pacemakers and 8 had ICDs.

There was some evidence of pacemaker malfunction in 3 of the 14 people with a pacemaker.  One person had rapid unexpected battery depletion.  One had an electrical ‘break’ in the pacemaker lead so that the pacing signal didn’t reach the heart.  There was a similar concern in another patient, but ultimately it was ruled that pneumonia was the main cause of death.  There was a 4th patient who would normally have been offered an ICD, who died of an abnormal heart rhythm called ventricular fibrillation (VF).  We can’t classify this as a pacemaker malfunction because pacemakers cannot treat VF.  Detail isn’t provided in the publication, but this 4th patient was either offered an improper device or decided to have an improper device after counselling.

We are not told how many patients have pacemakers in San Francisco, but based on USA figures of 3 million patients with pacemakers, the percentage of patients per year suffering potentially avoidable SCD is 0.01-0.02% (1 in 5,000-10,000).

There was evidence of ICD malfunction in 7 of the 8 patients who died from SCD during the three year period.  3 patients had VF, but the ICD did not detect the abnormal rhythm and consequently did not deliver any shocks.  In 2 patients, the ICD detected VF, but the shocks were delayed because the ICD tried to deliver a program of pacing which is useful for ventricular tachycardia (VT), but not VF.  These two people did receive shocks, but they were delayed and hence had less chance of correcting the abnormal rhythm.  1 patient had ventricular tachycardia, but the speed of the ventricular tachycardia was below the programmed rate set for the ICD to deliver treatment.   1 ICD delivered 3 shocks appropriately, but on the 4th shock the lead developed an electrical ‘break’ and so the shock energy did not reach the heart.  This is a hardware failure and unlike the other cases could not have been avoided with more stringent programming.

We know that there were 712 San Francisco residents who had ICDs, and during the 3 years of the study 109 of these patients died.  101 deaths were non-sudden death and therefore not considered in this research.  In the three year study period therefore, 0.3% (1 in 300) of ICD patients suffered a potentially avoidable SCD per year.

This is a much higher number than for patients with pacemakers, but ICD patients have more serious cardiac problems and ICDs are expected to treat more cardiac rhythm problems than pacemakers.  The rate of hardware failure is low, but the number that could be avoided to more stringent programming is a cause for concern, although the research doesn’t tell us exactly what could have been done with programming to avoid SCD.

Many of the patients across Surrey have ICDs and pacemakers which are monitored remotely.  In fact, St Peter’s Hospital, Chertsey, participated in a number of trials showing the effectiveness of remote monitoring and received a ‘Gold Award’ from Biotronik for remote monitoring.  Remote monitoring allows us to detect lead problems, battery problems and episodes of VT/VF.  If the VT/VF is unheralded then remote monitoring doesn’t help, but in many cases there are warning signs that remote monitoring does detect.  The same goes for lead and battery problems.  We can usually predict when there is going to be a problem.

Pacing and ICD checks also monitor the battery, leads and episodes of VT/VF.  These checks are 3-12 monthly dependent on the device implanted and patient history.  If there are any concerns then monitoring is more frequent.

Most modern ICDs charge while delivering pacing to stop VT and VF.  If the pacing (called anti-tachycardia pacing or ATP) doesn’t work then a shock is delivered without any further delay. Research has shown that ATP is not associated with adverse outcomes.

Our local Implantable Cardioverter Defibrillator club (ICDC Surrey), based at St Peter’s Hospital, Chertsey, and offering support to all hospitals in Surrey, teaches CPR training at every event. We know that this works because shortly after one of our sessions a patient was resuscitated by his very well educated wife.  There are also national drives to improve CPR training, and to provide external defibrillators for all potential patients including ICD patients. We support this initiative.

All the ICD manufacturers will examine their programs to make sure that VF is sensed as much as possible.  We will probably never reach 100% detection rates because VF has many different appearances. If we program so as never to miss VF then the ICDs will deliver too many shocks for rhythms that are not dangerous and, potentially, these inappropriate shocks could be dangerous. Our patients’ ICDs are programmed to suit the individual, and depend on their level of activity, cardiac function and our knowledge of previous rhythm problems. As a patient’s medical condition changes, the zones programmed for the device are also considered, in an attempt to ensure that VT is detected and treated in a way that benefits our patients; be that monitoring, ATP or shocks.

There is some extra work that we should do in partnership with the Coroners Office.  We should ask the Coroner to allow a pacing technician to check all pacemakers and ICDs from patients suffering SCD.  This will allow us to learn from any concerns regarding pacemakers and ICDs.

Please bear in mind that the scale of the problem is not large and that the majority of pacemakers and ICDs function well and save many lives.

The Cardiology Team at St Peter’s Hospital is already addressing these concerns. Please do not hesitate to ask one of the team for more information.

Patient and carer or family education and support through ICDC Surrey and similar organisations can help to identify problems, and early intervention is often life-saving.

The newspaper headlines from the USA do seem to overstate the concern regarding ICDs and pacemakers. We are not ignoring the concerns raised by this recent research, but we do have systems in place to help avoid and detect pacemaker and ICD malfunction. We will keep working in partnership with patients and suppliers to make ICDs and pacemakers as safe as possible.

Dr Ian Beeton is a Consultant Cardiologist, Ashford and St Peter’s Hospitals NHS Foundation Trust and is Patron of ICDC Surrey.

Thank you to Nicola Hutchison, Cardiac Investigations Manager, Ashford and St Peter’s Hospitals NHS Foundation Trust, for help in the preparation of this article.