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ICDs Have Come a Long Way in 40 Years Image Credit: Medtronic plc
Medtronic's Evera MRI ICDs were the first implantable cardioverter defibrillators to receive approval for use in the 1.5T and 3T MR-conditional environment. 

ICDs Have Come a Long Way in 40 Years

A look at the current state of the implantable cardioverter-defibrillator (ICD) market, in honor of the 40th anniversary of the first human implant of an ICD.

Michel Mirowski and his colleagues gave the field of implantable cardioverter-defibrillators (ICDs) a pretty good start, but what's more impressive is how far the technology has advanced since that first human ICD implant in February 1980. In the past 40 years we've seen ICDs become dramatically smaller, longer lasting, more capable, more personalized, subcutaneous (non-transvenous), and even MRI-firendly. And that's not to mention the advanced data connectivity and monitoring capabilities that the latest technologies offer. So without further ado, let's take a look at the current ICD landscape and the companies that are leading this important market.

Boston Scientific's S-ICD Continues to Dominate

Boston Scientific changed the ICD field considerably when it came out with its Emblem subcutaneous ICD (S-ICD), which offers many patients cardiac defibrillation without transvenous leads. Leads can come with complications, such as migration and perforation, and attempts to remove leads can also be risky. The device won the Prix Galien "Best Medical Technology" award in 2013. The S-ICD is mplanted subcutaneously and runs a lead outside of the sternum, not touching the heart. In 2016, FDA approved the third-generation Embelem MRI S-ICD, an MR-conditional device.

In May 2019, Boston Scientific announced acute results from its UNTOUCHED study evaluating the safety and efficacy of the Emblem S-ICD for primary prevention of sudden cardiac death specifically in patients with a left ventricular ejection fraction (LVEF) ≤35%, the most common population to be indicated for ICD therapy. The data were presented at Heart Rhythm 2019, and demonstrated S-ICD therapy had a complication-free rate of 95.8% at 30 days post-procedure and high conversion efficacy (99.2%) of induced ventricular fibrillation, rates comparable to those seen in previous S-ICD and transvenous implantable cardioverter-defibrillator (TV-ICD) studies. The analysis was also published online in the Heart Rhythm Journal

The UNTOUCHED study authors also reviewed procedure techniques and 30-day outcomes in patients implanted with the EMBLEM S-ICD System and found that the majority (69%) of procedures were performed using a two-incision technique. The two-incision technique data demonstrated a mean implant time of 55.8 minutes, which was 8 minutes faster than the mean 63.8 minutes for procedures that leveraged a three-incision implant technique, with comparable complication and conversion success rates.

"We found that the complication rate within this primary prevention population was as low as in prior S-ICD registries, despite the patients having much lower LVEF, more hypertension, and diabetes – underscoring that sicker patients do well with this device for the prevention of sudden death," said Lucas V.A. Boersma, MD, PhD, study principal investigator and electrophysiologist at St. Antonius Hospital, the Netherlands. "These acute outcomes also validate the advantages of the two-incision implant technique, which has continued to gain worldwide adoption in the last few years."

The global, prospective, non-randomized study evaluated data from 1,116 patients with a low LVEF, the majority of whom (54%) had ischemic heart disease.

"The data presented today reiterate the value of the Emblem S-ICD System for a broad group of ICD-indicated patients, enabling them to avoid the long-term complications associated with TV-ICD leads," Kenneth Stein, MD, senior vice president and chief medical officer, global health policy and rhythm management at Boston Scientific, said at the time. "We remain proud of the clinical success of the S-ICD System, which has now been implanted in nearly 60,000 patients worldwide, and we will continue to invest in clinical studies that advance our understanding of the role of the device in patients at risk of sudden cardiac death."

The final results of the UNTOUCHED study, including an analysis comparing inappropriate shock rates of the S-ICD to rates found in previous TV-ICD studies, will be reported after 18-months of patient follow-up.  

Medtronic's EV-ICD Could Fill the Gap

Analysts estimate that Medtronic has been losing market share in ICDs partly due to its lack of a non-transvenous ICD to compete with Boston Scientific's S-ICD. Medtronic is working to fill that product gap, however, with its extravascular ICD (EV-ICD). This device runs a lead just below the sternum and a May 2019 report from Needham & Co.'s Mike Matson suggests that the device could be a meaningful growth driver for Medtronic when it reaches the U.S. market. The lead is implanted closer to the heart than Boston Scientific's S-ICD, so Medtronic estimates that the device will use about half the energy, which in turns means the device can be made smaller with a longer batter life.

First-in-human data for the EV-ICD (in 21 patients) presented at Heart Rythm 2019 showed that the device can be implanted without major complications, and it can sense, pace, and defibrillate the heart.

Just recently, Medtronic won CE mark approval in Europe for its Cobalt and Crome portfolio of ICDs and cardiac resynchronization therapy-defibrillators (CRT-Ds). CRT-Ds are designed to send small electrical impulses to the lower chambers of the heart to help them beat in more synchronized patterns and reduce patient symptoms.

"Cobalt and Chrome heart devices deliver the opportunity of a personalized approach to defibrillator therapy, demonstrating how far we have come in this field," said Klaus Witte, MD, of the School of Medicine, University of Leeds, United Kingdom. "Moreover, these devices offer seamless patient care through their ability to transmit device and patient data via smartphone or tablet."

Medtronic's newest generation of implantable heart devices also includes several "smart" features: 

  • Intrinsic ATP (iATP), available on Cobalt XT ICDs and CRT-Ds. The iATP is an automated algorithm designed to adapt to a patient's irregular heart rhythms and attempt to reset them with pacing therapy, possibly avoiding the need for shocks.  This ventricular anti-tachycardia pacing (ATP) provides individualized therapy in real-time and is paired with Medtronic's SmartShock 2.0 shock-reduction technology. The devices also feature improved longevity and energy output, the company said.
  • The new portfolio also offers connected health with BlueSync technology, designed to enable the devices to communicate with the tablet-based CareLink SmartSync device manager for physicians, and the MyCareLink Heart mobile app for patients.

"These advancements will help physicians respond to patients' individual needs through informed clinical decision making, potentially improving the outcomes of patients around the world," said Rob Kowal, MD, PhD, chief medical officer of the cardiac rhythm and heart failure division, which is part of Medtronic's cardiac and vascular group.

Biotronik Is Not-So-Secret Anymore

Back in 2016, Marlou Janssen, former president of Biotronik, told MD+DI that the German medical device company was the best-kept secret in cardiac rhythm management. That doesn't seem to be the case today, as the privately-held company has become known for introducing the first FDA-approved single-lead ICD capable of performing both pacing and atrial sensing.

The technology provides the benefits of the single and dual-chamber in a single-lead device. This was important because single-chamber ICDS were designed to only sense changes in ventricular rhythm and were unable to sense atrial arrhythmias, such as atrial fibrillation, which increased the patient's risk of an inappropriate shock or potentially even a stroke. Because there is only one lead to implant, Biotronik's device also represented an opportunity for less complex and less costly procedures, along with fewer lead-related complications.

Last year the Journal of Cardiac Electrophysiology published results of the company's SENSE trial, which showed that Biotronik's DX system was equivalent to dual-chamber ICDs in detecting atrial high-rate episodes (AHREs). Trial data also demonstrated the DX system was superior to single-chamber ICDs, the company noted at the time.

“We’ve proven that the DX system gathers significant data with a single lead. Having the benefits of dual-chamber diagnostics without the need for an atrial lead is a true advantage for electrophysiologists,” said George Thomas, MD, a primary investigator of the study, and a physician at Weill Cornell Medical College in New York, NY. “The system can be trusted to deliver appropriate therapy while providing exceptional diagnostic data that improves patient care and outcomes.”

The Biotronik DX system, featured in both ICD and CRT-D devices, is designed to detect a true atrial signal without the need for an atrial sensing lead — reducing costs, procedure complexity and implant time compared to dual-chamber ICDs. The SENSE trial analyzed the efficacy of the DX system in detecting AHREs compared to single-chamber ICDs and dual-chamber ICDs. This prospective cohort-controlled trial enrolled 150 patients with a DX system at eight study centers in the U.S. and compared results to retrospective single and dual-chamber age, sex and left ventricular ejection fraction matched cohorts. The AHRE detection rates at 12-months post implant are below:

  • DX: 13.0%
  • Dual-Chamber: 13.0%
  • Single-Chamber: 5.3%

DX patients received zero inappropriate shocks, where traditional single-chamber patients had an inappropriate shock rate of 3.3%, the researchers reported.

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