Initial Experience with the S-ICD System at Florida Hospital Pepin Heart Institute

Florida Hospital Pepin Heart Institute is a freestanding, dedicated cardiovascular center located at Florida Hospital Tampa, the tertiary hospital for the Florida Hospital Tampa Bay Network. We recently became the first institution in the region to implant Boston Scientific’s S-ICD^™ System, a unique implantable cardiac defibrillator placed subcutaneously beneath the skin. In December 2013, Dr. Asad Sawar and Dr. Kenneth Yamamura, Medical Director of Florida Hospital Pepin Heart Institute’s electrophysiology (EP) lab, worked in conjunction to implant the first two S-ICD Systems.

Florida Hospital Pepin Heart Institute is the all-cardiac care destination providing cutting-edge technology to the Tampa Bay region, and is a leader in cardiovascular patient care, teaching and research. We are known for performing high-quality cardiovascular research with an extensive and growing cardiovascular research program. Our facility was also one of the leading centers in the Boston Scientific INGEVITY lead study, spearheaded by Dr. Yamamura. 

The recent S-ICD implants were performed in our new state-of-the-art EP lab, which officially re-opened in December 2013. This lab hosts a number of high-quality attributes such as the new CartoUnivu Module (Biosense Webster, Inc., a Johnson & Johnson company), of which Florida Hospital Pepin Heart Institute was among the first in the nation to upgrade to this technology. The CartoUnivu Module allows physicians to use very little fluoroscopy, thereby reducing patients’ and physicians’ exposure to additional radiation. EP procedures can use an overlay of a CT or 3D map with a simple fluoroscopy view to help guide catheters nonfluoroscopically, reducing overall exposure to radiation. The lab also hosts a state-of-the-art camera system with the capability to stream live video cases for teaching purposes to conference centers or academic institutions. Large 56-inch screen monitors afford the physicians better views. We also have laminar air flow to help reduce infection risk and improve outcomes. In addition, the lab has an in-suite control room with 180-degree views as well as an anesthesia portal for general or monitored anesthesia care. 

Dr. Yamamura is leading Florida Hospital Pepin Heart Institute into advanced realms of interventional electrophysiology. Sudden cardiac arrest (SCA) is a serious condition that we are committed to treating with options such as the S-ICD System. The S-ICD represents a paradigm shift in ICD therapy, providing patients more choices with this lifesaving therapy. Florida Hospital Pepin Heart Institute’s research hub, the Dr. Kiran C. Patel Research Institute, will also be participating in the U.S. S-ICD System Post Approval implant registry study, which will provide Boston Scientific with long-term longitudinal patient follow-up and post-implant outcomes 

SCA claims more than 350,000 lives per year and affects an estimated 382,800 people per year. Of the patients who experience SCA, approximately 92% do not survive.¹ The Heart Rhythm Society estimates that SCA kills more than 1,000 people per day, which is about equal to one person every 90 seconds.¹ The need for intervention in SCA events is imperative, and the implantable defibrillator has provided up to a 54% reduction in mortality in randomized controlled trials for both ischemic and non-ischemic cardiomyopathy patients.^2-4 Unfortunately, not all patients are optimal candidates for implantable devices due to co-existing health issues, risk of infection, or poor venous access. ICDs also require venous access for the transvenous lead systems. These transvenous leads are placed in a beating heart and are most often the “weak link” in the ICD system, prone to failure and/or infection. The need for an extrathoracic or entirely subcutaneous ICD was evident, and technology has now advanced to provide the first subcutaneous ICD system. The early proof of concept research for the S-ICD System evaluated several configurations and found the best configuration was a parasternal electrode combined with a left lateral thoracic pulse generator.⁵ 

Physicians can implant the S-ICD System using only anatomic landmarks, eliminating the need for fluoroscopy and reducing radiation exposure to the patient, physician, and staff. The pulse generator is placed in the left lateral chest overlying the apex of the left ventricle at the mid-axillary line in the 6th intercostal space. The generator is connected to a 3 mm tripolar parasternal electrode, which is inserted through two parasternal incisions. The electrode is tunneled between the incisions, which are 1-2 cm to the left of and parallel to the sternal midline.⁶ Detecting the cardiac rhythm is performed through three vector configurations utilizing the sensing electrodes or pulse generator. One of the concerns is T wave oversensing — a simple screening using surface ECG comparing the size of the R wave to the T wave can identify patients with inadequate sensing characteristics prior to implant. Vector configurations can include: (a) proximal-to-canister (CAN); (b) distal-to-CAN; or (c) distal to proximal. To prevent double counting and T wave oversensing, there are three different algorithms that are applied to each cardiac signal.⁶ The S-ICD System clinical study enrolled 330 patients with 321 implants. Appropriate detection of VT/VF was confirmed in 897 of 899 inductions, or 99.8% of the time. Conversion of ventricular fibrillation was present in 100% of patients at 65J (standard testing energy). The S-ICD does have a higher mean energy requirement, and the current device has twice the output of a transvenous ICD at 80J.^5,7 The defined therapy is also a unique feature of the S-ICD in that the device is tested at 65J and then all shocks are automatically programmed to 80J.^5,7 Inappropriate shock therapy has recently come to the forefront with the MADIT-RIT trial, which showed that these inappropriate shocks were associated with a higher mortality.⁸ Inappropriate therapy occurred in 13.1% of patients, and this was due mostly to T wave oversensing or supraventricular tachycardia (SVT) in the VF zone (rate only). By using a dual zone configuration utilizing a conditional zone with both rate and morphology discriminators, this was reduced by 56% and 70%, respectively.⁷

The advantages of the S-ICD System are multifold. The initial development of this system was intended for those individuals who were not candidates for transvenous ICDs or those with congenital heart abnormalities. Several qualities of the S-ICD System make this a unique but advantageous option for patients. Those individuals with a high risk for systemic infection, such as patients with diabetes, immunocompromised patients, previous device infections, endocarditis, or artificial heart valves, would be ideal candidates. The S-ICD System is expected to have a lower incidence of infection and easier removal should infection occur, avoiding the potential risks of endovascular lead extraction. Patients who have limited vascular access or need to preserve their vascular access, such as those on hemodialysis, may also benefit from this system, as well as patients who are younger who lead very active lifestyles and are at a higher risk for lead fracture.⁶ This group would include patients with inherited conditions for SCA such as long QT syndrome, Brugada syndrome, and hypertrophic cardiomyopathy. The need for this therapy is obvious when it is estimated that 15% of all ICD leads will fail over time and by eight years, up to 40% of ICD leads will fail.⁹

The S-ICD System is not appropriate for all populations requiring ICD therapy. Those individuals requiring pacing for bradyarrhythmias, cardiac resynchronization therapy or anti-tachycardia pacing for stable monomorphic VT still require a transvenous system. The S-ICD System does provide 30 seconds of backup pacing for post-shock asystole, but it is transthoracic.⁶

The addition of the new S-ICD System to our electrophysiology lab brings one more option for the patients of Tampa Bay and West Central Florida to receive optimal care. This new leading-edge technology, combined with a state-of-the-art EP lab in a renowned center of excellence, differentiates Florida Hospital Pepin Heart Institute from other cardiovascular programs in the region. 

Disclosures: The authors do not have any conflicts of interest to report regarding the content herein. Outside the submitted work, Dr. Yamamura reports having received honoraria and travel/accommodations expenses covered or reimbursed from Biosense Webster, Inc., and Boston Scientific. 

Dr. Kenneth Yamamura is the Medical Director of the Electrophysiology Lab at Florida Hospital Pepin Heart Institute, and is in private practice based in both Hillsborough and Pasco counties. He is board certified in Internal Medicine, Cardiology and Cardiac Electrophysiology. In addition, Dr. Yamamura maintains long-term research interests and serves as principal investigator on several electrophysiology and cardiovascular studies. 

Brian Nordgren is a physician assistant at Florida Hospital Pepin Heart Institute, practicing in interventional and cardiovascular research. Brian has a Doctorate of Health Science and enjoys working in stem cell/device research with interventional cardiology and electrophysiology.

Dr. Asad Sawar is an interventional cardiologist practicing at Florida Hospital Tampa Pepin Heart Institute and is in private practice at Tampa Cardiovascular Associates. Dr. Sawar has been in practice for more than 12 years and has interests in Cardiac Catheterization, Interventional Cardiology, Thrombectomy (clot removal), Peripheral Vascular Disease, Venous Ablation, and Device Implantation.

References

1. Sudden Cardiac Arrest Facts. Heart Rhythm Society. Available online at https://www.hrsonline.org/News/Fact-Sheets/SCA-Facts#axzz2rnQQbxcB. Accessed January 29, 2014.
2. Moss AJ, Hall WJ, Cannom DS, et al. Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter Automatic Defibrillator Implantation Trial Investigators. N Engl J Med. 1996;335:1933-1940. 
3. Moss AJ, Zareba W, Hall WJ, et al, for the Multicenter Automatic Defibrillator Implantation Trial II Investigators. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002;346:877-883. 
4. Bardy GH, Lee KL, Mark DB, et al, for the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) Investigators. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med. 2005;352:225-237. 
5. Bardy G, Smith W, Hood M, et al. An entirely subcutaneous implantable cardioverter-defibrillator. N Engl J Med. 2010;363:36-44. 
6. Rowley C, Gold M. Subcutaneous implantable cardioverter defibrillator. Circ Arrhythm Electrophysiol. 2012;5:587-593. 
7. Weiss R, Knight B, Gold M, et al. Safety and efficacy of a totally subcutaneous implantable-cardioverter defibrillator. Circulation. 2013;128:944-953.
8. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med. 2012;367:2275-2283.
9. Kleeman T, Becker T, Doenges K, et al. Annual rate of transvenous defibrillation lead defects in implantable cardioverter-defibrillators over a period of  >10 years. Circulation. 2007;115:2474-2480.