Cardiac Rhythm Management


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In this illustrative presentation, Dr. Martin Burke evaluates the safety and efficacy of the subcutaneous implantable defibrillator (S-ICD System) for the management of patients at risk of SCA, featuring a review of clinical evidence through an assessment of significant study data.

An Emerging Technology Expert Interview with Martin C. Burke, DO, FRCP

dr-burkeDr. Martin Burke, Professor of Medicine at the University of Chicago and Director of the Medical Center’s Heart Rhythm Center, shares his expert insights surrounding the role and impact of S-ICD therapy for the treatment of patients at risk for SCA.  This interview was conducted by the editorial department of The Journal of Innovations in Cardiac Rhythm Management.

Cardiac Rhythm Management

What is the S-ICD System? 

Dr. Burke
The S-ICD System introduces a new class of implantable defibrillators that enables clinicians to offer a new ICD implant solution to patients at risk for sudden cardiac arrest. The S-ICD System was developed using 10 years of research to render the current device. Like traditional transvenous ICDs (TV-ICDs), the system utilizes a pulse generator capable of delivering life-saving high energy shocks to convert ventricular arrhythmias. Unlike TV-ICDs, the system is implanted in the lateral thoracic region of the body and utilizes a subcutaneous electrode, instead of a transvenous lead, to both sense and deliver therapy. The system utilizes highly sophisticated technology to identify and classify the actual heart rhythm – rather than counting individual beats – to effectively sense, discriminate and convert VT/VF.

What are the main findings in the study?

Dr. Burke
The main findings of the study are that the S-ICD is safe and effective at sensing and defibrillating life threatening arrhythmia in patients at high risk of sudden cardiac death.  The freedom from device and procedurally related complications was seen in 92% of the implant population compared to a benchmark set by the FDA of 79%.  Furthermore the device was effective at terminating ventricular fibrillation and tachycardia during acute implant testing in 98% of the patients at the low testing energy of 65 Joules and 100% of the spontaneous episodes at the device ambulatory prescribed 80 Joules.  Both of these findings far exceeded the historical control objective performance criterion determined by the FDA, from prior ICD investigational studies, at 88%.

Were you surprised by any of these findings?

Dr. Burke
No, the effectiveness data was expected as there was a large amount of work choosing the defibrillation energy requirements and vector leading up to the pivotal study.  However, the safety data was particularly strong given that the S-ICD System is a new implant platform and was rolled out to at least 28 centers that had no prior experience with the device or its implant. The lessons learned from the IDE study helped to decrease the wound infection rate through better prep techniques and allowed for better programming to cut the inappropriate shock rate in half.  

What are the implications of this data for clinicians and patients?

Dr. Burke
The S-ICD is a safe, viable and an important addition to an electrophysiologist’s "tool box” for the treatment and prevention of sudden cardiac arrest. The implant procedure was shown to be safe and predictable with early experience demonstrating a quick learning curve for implantation success by experienced electrophysiologists who already implant ICD's transvenously today. Additionally, patients absolutely get the fact that there is no lead in the heart. Enrollment in the pivotal S-ICD device trial was very brisk due to the enticement of not having a wire directly in the heart. Patients carefully weighed preventing the attendant risks of insulation breaks, wire fracture and systemic infection seen with chronic indwelling leads within the vasculature when considering their choice of ICD. They easily accepted the entirely subcutaneous implant platform as a great option. 

Who is the patient candidate for the S-ICD System?

Dr. Burke
The majority of patients who meet the guidelines for ICD implantation or replacement are viable candidates for the S-ICD System; this includes both primary and secondary prevention indications.   Also, there are specific patient populations with underlying conditions that may benefit from this unique technology:

  • Those with no blood vessel access to the heart
  • Those born without enough chambers to accommodate a transvenous electrode in the heart
  • Those at risk for infection either from a previous TV-ICD infection or due to co-morbidities
  • Those who are younger of age

Basic S-ICD System benefits such as lower complication rates and an uncompromised venous system should be considered when evaluating these patients.  

Patients with an indication for a pacing or who have recurrent VT that is reliably terminated with ATP are not candidates for the SICD.

What future research would you like to see on the S-ICD System?

Dr. Burke
The S-ICD System is in its first generation with early experience showing an outstanding safety and efficacy across a broad cardiac disease population at risk of sudden death.  We look forward to combining data from the US experience and the experience of those in other global markets to report on outcomes from spontaneous events and specific patient populations that may receive the S-ICD such as patients with Congenital Heart Disease, Long QT Syndrome, Arrhythmic Cardiomyopathy and Hypertrophic Cardiomyopathy to name just a few. Downsizing and remote monitoring are short term additions to the device that should be considered. This is a first generation implant platform with broad potential. Future research into leadless pacing of the heart combined with the SICD left lateral pulse generator would be an obvious and purposeful benefit to both the patients in need of pacing or VT termination as well as the ICD therapy in general.

Cardiac Rhythm Management

Dr. Burke has disclosed that he serves as a consultant for and recipient of research support from Cameron Health, Inc., and has served as a consultant for and recipient of research grants from Boston Scientific Corporation.