No follower of medical device technology can be unaware of the unfolding issue relating to so-called externalisation of certain implantable cardioverter/defibrillator leads, most famously St.Jude’s Riata and Riata ST models. Back in December 2011, the UK’s regulatory authority the MHRA issued a Medical Device Alert(MDA) recommending enhanced patient follow-up for all patients implanted with these specific models. A new MDA has been issued today because of the evolutionary changes to the pattern of device failure as time has progressed and also because the full picture from St.Jude’s own study will not be available for over a year, leaving a potential void in the treatment guidance.
St Jude Medical issued a Field Safety Notice in July 2012 detailing phase I of a Riata lead evaluation study to investigate the prevalence of externalised cables using fluoroscopy. According to the MDA issued today, the clinical significance of externalised cables will not become evident until phase II of the study is completed, most likely deep into 2013. Consequently this MDA is focusing on detection of early signs of functional lead failure, as these lead models continue to fail at a higher rate. Furthermore it draws attention to the suggestion from the evolving data is that the difference in prevalence of externalised cables between 8Fr and 7Fr lead models is decreasing.
Today’s MDA, targeted at Cardiologists and Cardiac electrophysiologists, guides these specialists to continue following up all patients implanted with Riata or Riata ST ICD lead models to identify any changes in lead performance.
Clinicians are asked to undertake this at three month intervals to monitor for HV lead noise using an unused EGM channel and turn on RV AutoCaptureTM (or equivalent) pacing to monitor pacing thresholds.
At six-month intervals guidance is that follow up should be in the clinic, where high voltage lead integrity (HVLI) test should be performed at box change. If a decision is made to continue to use the lead, the replacement device must have remote/advanced monitoring capabilities.
If lead failure is suspected clinicians should consider the need for further examination e.g. by ECG or fluoroscopy, although the need for fluoroscopy should be balanced against the risks from radiation exposure.
If a lead failure is confirmed, the risks and benefits of lead replacement options should be evaluated on a case-by-case basis in discussion with the patient although the prophylactic explantation of leads is not recommended, other than in exceptional clinical circumstances.
The above guidance is distilled from the full MDA, which can be found here.