Daniel B. Kramer

HRS Expert Consensus Statement on the Management of Cardiovascular Implantable Electronic Devices (CIEDs) in patients nearing end of life or requesting withdrawal of therapy.

1 RS Expert Consensus Statement on the Management of ardiovascular Implantable Electronic Devices (CIEDs) in atients nearing end of life or requesting withdrawal of therapy his document was developed in collaboration and endorsed by the American College of Cardiology ACC), the American Geriatrics Society (AGS), the American Academy of Hospice and Palliative edicine (AAHPM); the American Heart Association (AHA), the European Heart Rhythm ssociation (EHRA), and the Hospice and Palliative Nurses Association (HPNA).

Ghost Talk: Mitigating EMI Signal Injection Attacks against Analog Sensors

Electromagnetic interference (EMI) affects circuits by inducing voltages on conductors. Analog sensing of signals on the order of a few millivolts is particularly sensitive to interference. This work (1) measures the susceptibility of analog sensor systems to signal injection attacks by intentional, low-power emission of chosen electromagnetic waveforms, and (2) proposes defense mechanisms to reduce the risks. Our experiments use specially crafted EMI at varying power and distance to measure susceptibility of sensors in implantable medical devices and consumer electronics. Results show that at distances of 1-2m, consumer electronic devices containing microphones are vulnerable to the injection of bogus audio signals. Our measurements show that in free air, intentional EMI under 10 W can inhibit pacing and induce defibrillation shocks at distances up to 1-2m on implantable cardiac electronic devices. However, with the sensing leads and medical devices immersed in a saline bath to better approximate the human body, the same experiment decreases to about 5 cm. Our defenses range from prevention with simple analog shielding to detection with a signal contamination metric based on the root mean square of waveform amplitudes. Our contribution to securing cardiac devices includes a novel defense mechanism that probes for forged pacing pulses inconsistent with the refractory period of cardiac tissue.

Time for a Change — A New Approach to ICD Replacement

Of the 100,000-plus implantable cardioverter–defibrillators (ICDs) implanted in the United States annually, at least 25% are generator replacements required for depleted batteries. Should all those patients be receiving replacement ICDs?

Implantable cardioverter-defibrillator lead performance.

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of patients at risk for sudden cardiac death. In the nearly 3 decades since the first human ICD implant,1 millions of devices have been implanted worldwide and innumerable lives have been saved. Successful resuscitation of a potentially lethal ventricular arrhythmia by an ICD system depends on successful arrhythmia detection and timely delivery of therapy. Both the ICD generator and the ICD lead are critical components of this system. The lead, in particular, is literally a lifeline whose purpose is to convey critical information about the heart’s rhythm to the ICD generator and, in turn, to deliver life-sustaining therapy when needed. Failure of an ICD lead may result in significant clinical events, including failure to pace, failure to defibrillate, inappropriate shocks, and even death. Article p 2727 ICD leads, like many medical technologies, have undergone a remarkable transformation. Epicardial leads, which necessitated a thoracotomy for lead placement, have given way to transvenous leads, which are easier to implant, less costly, and associated with decreased morbidity and mortality.2 Important advances in transvenous lead technology, such as the development of steroid elution, smaller diameter leads, novel insulations, and multipolar leads, have translated into meaningful clinical benefits for patients. Although modern ICD leads consist primarily of electrodes, conductors, insulation, and a fixation mechanism to attach the lead to the myocardium, lead design and performance vary from model to model. Indeed, monitoring of performance is critical not only to identify products with increased failure rates but also to provide physicians and patients with realistic expectations of device performance. In the current issue of Circulation , Eckstein et al add to our understanding of ICD lead performance.3 The investigators conducted a retrospective analysis of 1317 consecutive patients who received ICD systems (including 38 different ICD lead …

Development and validation of a risk score to predict early mortality in recipients of implantable cardioverter-defibrillators.

BACKGROUND Current guidelines do not recommend implantable cardioverter-defibrillator (ICD) implantation in patients with a life expectancy of <1 year. Better methods are needed for identifying patients at high risk for early mortality despite ICD therapy. OBJECTIVE To develop and validate a risk prediction score to identify patients at high risk for death within 1 year despite ICD therapy. DESIGN Detailed clinical data were collected on a large observational cohort of ICD patients from 3 tertiary care centers. One-third of the patients were randomly selected to form the prediction group (PG) from which a risk score was developed using logistic regression. This score was then applied to the remaining two-thirds of the cohort (validation group [VG]) to assess the risk scores predictive accuracy. RESULTS The total cohort included 2717 ICD patients (mean age = 64.6 ± 14.5, male = 77.2%, primary prevention = 74.7%). A simple risk score incorporating peripheral arterial disease, age ≥ 70 years, creatinine ≥ 2.0 mg/dL, and ejection fraction ≤20% (PACE) accurately predicted 1-year mortality in the VG. Patients with a risk score of ≥3 had a >4-fold excess 1-year mortality compared with patients with a risk score of <3 (16.5% vs 3.5%; P <.0001). LIMITATION Risk reduction provided by ICD therapy in this cohort is not known given the lack of a control group. CONCLUSIONS A simple risk score accurately predicts 1-year mortality in ICD patients, as patients with a PACE risk score of ≥3 are at high risk despite ICD therapy.

How Does Medical Device Regulation Perform in the United States and the European Union? A Systematic Review

Aaron Kesselheim and colleagues conduct a systematic review to examine the strengths and weaknesses associated with approaches to medical device regulation in the US and EU.

Independent multicenter study of Riata and Riata ST implantable cardioverter-defibrillator leads.

BACKGROUND Riata and Riata ST leads (St Jude Medical, Sylmar, CA) are prone to failure. There are no independent multicenter reports regarding Riata or Riata ST lead performance. OBJECTIVE To conduct a retrospective multicenter study of Riata and Riata ST leads that were implanted and followed at 7 centers. METHODS The study included adults who received St Jude Medical Riata or Riata ST leads. Data for Quattro Secure leads were obtained from an earlier study. RESULTS From 2002 to 2010, 1081 patients received a Riata (n = 774) or Riata ST (n = 307) lead. Follow-up was longer for Riata than Riata ST leads (4.2 ± 2.4 years vs 3.3 ± 1.7 years; P<.0001). During the study, 67 leads failed (6.2%), including 62 of 774 Riata (8.0%) and 5 of 307 Riata ST (1.6%) leads. Forty-seven of 67 lead failures (70.1%) were caused by electrical malfunction, and 20 lead failures (29.9%) were due to externalized conductors (ECs) that were electrically intact. Of 110 leads examined fluoroscopically, ECs were found in 26 of 81 Riata (32%) and 1 of 29 Riata ST (3.4%) leads. Of 26 Riata leads with ECs, 7 (27%) were malfunctioning. Riata leads had lower overall and malfunction free survival compared to Quattro leads (P<.0001), while Riata ST lead survival was not different (P = .422). CONCLUSIONS The survival of Riata (but not Riata ST) leads was lower than Quattro leads; however, Riata ST leads had significantly shorter follow-up than Riata leads. ECs were common in Riata leads, and more than a quarter of Riata leads that had ECs were malfunctioning. Our observations suggest that systematic fluoroscopic examination of patients with Riata leads is appropriate.

Long-QT syndrome.

Acquired and hereditary long-QT syndromes are important causes of sudden cardiac death. Both categories are characterized by abnormally prolonged cardiac repolarization arising from a complex interaction between genetic and environmental factors. This produces a potentially dangerous substrate for polymorphic ventricular tachycardia and sudden cardiac death. In this review, the pathophysiologic, diagnostic, and prognostic features of long-QT syndromes, as well as recommendations regarding therapy, are reviewed.

Premarket clinical evaluation of novel cardiovascular devices: quality analysis of premarket clinical studies submitted to the Food and Drug Administration 2000-2007.

The quality of clinical data submitted by manufacturers to support Food and Drug Administration cardiovascular device premarket approval (PMA) applications varies widely and formal quality assessment has not been previously performed. This study evaluated all original cardiovascular device PMAs with Food and Drug Administration decisions between January 1, 2000, and December 31, 2007, to assess the quality of clinical investigations submitted by manufacturers. Effectiveness and safety end points were judged high quality if they were clearly defined and associated with a specific time point for analysis. Subject accounting was high quality if 90% or greater of the original cohort was accounted for at study conclusion. In total, 88 cardiovascular device PMAs (77.3% permanent implants), 132 clinical studies, 37,328 study subjects (age 61.0 ± 14.5 years, 33.9% women, 86.3% white), and 29,408 device recipients were analyzed. All PMAs contained clinical data. Primary effectiveness end points, primary safety end points, and subject accounting were deemed high quality in 81.8%, 60.2%, and 77.3% of pivotal studies, respectively. Key cardiovascular comorbidities (coronary artery disease 51.1%, diabetes 36.6%, hypertension 35.2%, heart failure 37.5%, tobacco use 31.8%) and race (14.8%) were infrequently reported, and studies rarely included patients younger than 18 years of age (10.2% of studies). Poorly defined safety and effectiveness end points, poor patient accounting, and incomplete collection of important patient comorbidities make device safety and effectiveness assessments more challenging. Women, pediatric, and nonwhite populations are underrepresented in premarket cardiovascular clinical trials. Manufacturers, regulators, and the clinical community should collaborate to address these study shortcomings to ensure that patients are treated with reliable, safe, and clinically useful medical devices.

Characteristics and Outcomes of Patients Receiving New and Replacement Implantable Cardioverter-Defibrillators Results From the NCDR

Background—Little is known about the clinical features, procedural risks, or survival of patients receiving replacement versus new implantable cardioverter-defibrillators (ICDs). Methods and Results—Entries in the National Cardiovascular Data Registry (NCDR) ICD Registry from 2005 through 2010 were eligible for inclusion (n=463 978). Baseline demographic data, clinical information, and procedural variables were compared between patients receiving new (n=359 993; 77.6%) and replacement (n=103 985; 22.4%) ICDs and entered into a propensity match model to determine adjusted survival rates. Patients receiving replacement ICDs were older (70.7 versus 67.5 years of age) and more likely to have atrial fibrillation (41.8% versus 31.4%; P<0.001) and ventricular tachycardia (60.5% versus 33.9%; P<0.001) compared with patients receiving new ICDs. Median battery life was only 4.6 years (25%–75% interquartile range, 3.7–5.8) for all replaced devices, 5.8 (25%–75% interquartile range, 4.2–7.5) for single-chamber, 5.1 (25%–75% interquartile range, 4.1–6.1) for dual-chamber, and 3.9 (25%–75% interquartile range, 3.2–4.6) years for biventricular devices. Patients receiving replacement ICDs had lower rates of index admission complications (0.9% versus 3.2%; P<0.001) but greater risk for death compared receiving patients receiving new ICDs in unadjusted analysis (hazard ratio, 1.18; 95% confidence interval, 1.16–1.20; P<0.0001) and after propensity-score matching (hazard ratio, 1.28; 95% confidence interval, 1.25–1.30; P<0.0001). Conclusions—Patients receiving replacement ICDs are older and at greater risk for death compared with those receiving initial ICD implants. The battery life of initial ICDs is shorter than previously reported.