JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY

VOL. 70, NO. 7, 2017

ª 2017 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION PUBLISHED BY ELSEVIER

ISSN 0735-1097/$36.00 http://dx.doi.org/10.1016/j.jacc.2017.06.055

EDITORIAL COMMENT

Subcutaneous Implantable Cardioverter-Defibrillator Finding a Place in Sudden Cardiac Death Prevention Emerging or Emerged?* Jeanne E. Poole, MD, Jordan M. Prutkin, MD, MHS

T tions

he subcutaneous implantable cardioverter-

was 99.0% and the all-cause complication-free rate

defibrillator

was 92.1%. This study led to U.S. Food and Drug

(S-ICD)

was

developed

in

response to endovascular lead complica-

with

traditional

transvenous

Administration approval of the S-ICD.

implantable

Early S-ICD adoption was low, in part due to

cardioverter-defibrillators (ICDs). These include lead

consideration of the S-ICD as only a niche device, and

malfunction due to conductor or insulation failure;

also due to delayed third-party insurance coverage.

acute implantation risks, such as pneumothorax or

Over the past few years, however, the use of the S-ICD

cardiac perforation; long-term complications, such

in the United States has increased (4), although there

as venous stenosis or tricuspid valve damage; and

has been hesitancy in its use due to the lack of pacing

the consequences of device infection (e.g., sepsis,

capabilities. Some physicians have been concerned

lead-related endocarditis, and lead extraction risks).

that patients will later need bradycardia pacing or

Although these are all causes for concern at any

cardiac resynchronization therapy (CRT), although

age, the risk is particularly problematic in younger pa-

the need for pacing appears to be low if the patient

tients who face years, if not decades, of complex lead

does not require pacing at the time of implantation

management, including possible extractions.

(5). It is important to note that pacemakers (trans-

The S-ICD underwent over 10 years of preclinical

venous or “leadless”) can be used safely following

studies (1,2), followed ultimately by the Investiga-

S-ICD implantation (6). In addition, some clinicians

tional Device Exemption (IDE) trial (3). The primary

want the ability to use the antitachycardia pacing

efficacy endpoint for the IDE trial, which was the

(ATP) available with transvenous lead systems, which

acute conversion rate of induced ventricular fibrilla-

may terminate slower monomorphic ventricular

tion (VF) at the time of device implantation, exceeded

tachycardia (VT) and reduce shock episodes.

the threshold of 88%, with a first-shock efficacy of

Recently, the ongoing S-ICD Post-Approval Study

94.7% (3). The device also successfully converted all

reported the clinical profile and peri-implant com-

of the 38 spontaneous episodes occurring in 21 pa-

plications of 1,637 S-ICD patients (7). Of the 1,412

tients. At 180 days, the primary safety endpoint,

subjects who underwent acute conversion testing of

freedom from serious device-related complications

induced VF, 98.7% were successful. At 30 days, the freedom from S-ICD complication rate was 99.0%, and the freedom from device- and procedure-related

*Editorials published in the Journal of the American College of Cardiology

complication rate was 96.2%. The inappropriate

reflect the views of the authors and do not necessarily represent the

shock rate was 0.2% at 30 days, a low rate due to

views of JACC or the American College of Cardiology.

newer sensing algorithms and near-universal use of

From the Division of Cardiology, Department of Medicine, University of

dual-zone programming.

Washington, Seattle, Washington. Dr. Poole has received honoraria for speaking or serving on advisory boards from Abbott, Biotronik, Boston

In this issue of the Journal, Boersma et al. (8)

Scientific, Kestra Inc., and Medtronic. Dr. Prutkin has reported that he has

present the safety and efficacy results from the

no relationships relevant to the contents of this paper to disclose.

complete dataset of the EFFORTLESS (Evaluation of

Poole and Prutkin

JACC VOL. 70, NO. 7, 2017 AUGUST 15, 2017:842–4

Has the S-ICD Finally Emerged?

Factors ImpacTing Clinical Outcome and Cost Effec-

and 4%, respectively. In the ADVANCE III (Avoid

tiveneSS of the S-ICD) registry (8). Data on the first

Delivering Therapies for Nonsustained Arrhythmias

472 patients were previously reported, as were the

in ICD Patients III) trial, the programming included a

results of a pooled analysis combining 561 patients

therapy zone of >188 beats/min for 18 of 24 beats

from the EFFORTLESS registry and the 321 patients

versus 30 of 40 beats (14). The longer detection time

enrolled into the U.S. Food and Drug Administration’s

led to a reduction in inappropriate shocks from 11 to

IDE trial (total of 882 patients) (9,10). The current

5 per 100 patient-years. In the current EFFORTLESS

study now reports an analysis of all 985 patients

study, mean time to therapy was 18.4  4.3 s, which

followed for a minimum of 1 year and a median of

allows for nonsustained episodes to self-terminate

3.1 years.

and was 1 reason inappropriate shock rates were low. The longer time to therapy of the S-ICD due to

SEE PAGE 830

higher shock energy is consistent with recommended

The primary outcomes were the complication and

contemporary programming strategies.

inappropriate shock rates. The results from this study

ICD infections are a major concern, and in all major

are consistent with those reported earlier (3,7,9,10).

S-ICD studies, no patient has developed endocarditis

Complications considered to be directly due to the

(1,8–11). A pocket infection, however, may occur with

S-ICD system at 30 and 360 days were 0.3% and

transvenous or subcutaneous ICD systems. Unlike the

2.0%, respectively, the most common of which were

randomized clinical trials of the transvenous ICD, in

oversensing,

causing

inappropriate

shocks,

and

S-ICD studies, superficial skin infections (i.e., cellu-

device discomfort. All-cause complications totaled

litis) have been counted as a device infection. Most

4.1% at 30 days and 8.4% at 360 days.

cellulitis infections do not progress deeper and can be

The rate of inappropriate and unnecessary shocks

treated with antibiotics alone. The rate of patients

is of special interest in S-ICD studies, as this device

needing S-ICD removal for infection has been small.

only offers shock therapy. The inappropriate shock

In the current EFFORTLESS study, 2.4% of infections

rate in the IDE trial was 11.8%, of which 4.7% was

required device removal. Over time, with more

for atrial fibrillation (AF) or other supraventricular

experience, the infection rates decreased. Almost all

tachyarrhythmias (SVTs) and 7.5% was for over-

infections presented symptomatically in the first year

sensing. An important lesson learned from the IDE

after implant, although rare patients had late in-

trial was the importance of using dual-zone pro-

fections. This is interesting, as transvenous device

gramming.

zone

infection studies have shown that up to 50% of pa-

(usually