Advances in Cardiac Implantable Electronic Devices 2016
- Leadless pacemaker: The U.S. Food and Drug Administration (FDA) approved the first-in-man leadless pacemaker (Medtronic, Inc.), in which the entire device is placed within the right ventricle. The revolution of leadless pacing, after more than 50 years of transvenous pacing, entirely avoids device pocket and lead related complications such as thrombosis, lead failure, pneumothorax and tricuspid regurgitation. The battery life is approximately 10 years. The device has been successfully implanted in 719 of 725 patients (99.2%) in the initial multicenter prospective study.1 The major procedure complication rate was lower than the rate in a historical control cohort (4.0% vs. 7.4%; hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001).
- The interest in His Bundle pacing has been increasing to promote physiological atrioventricular (AV) conduction and ventricular synchronization.2-7 The study "Usefulness of His Bundle Pacing to Achieve Electrical Resynchronization in Patients With Complete Left Bundle Branch Block and the Relation Between Native QRS Axis, Duration, and Normalization" examined the relation between native QRS axis in left bundle branch block (LBBB), and QRS normalization in 29 patients with LBBB undergoing His Bundle pacing: 9 patients had frontal plane QRS axes between -60° and -80°, 10 patients from -40° to 0°, and 10 patients from +1° to +90°. QRS narrowing occurred in 24 patients (83%, 44 ± 34 ms, p <0.05). In patients with a QRS normalization after His Bundle pacing, the mean QRS duration was 155 ± 21, compared to 171 ± 8 ms in those without QRS normalization, p = 0.014. The study suggests that proximal His-Purkinje block may cause most cases of LBBB. Therefore, ventricular resynchronization may be achieved with His Bundle pacing even in LBBB patients.8
Implantable Cardioverter Defibrillators (ICDs)
- Ten years after the Sudden Cardiac Death in Heart Failure (SCD-HeFT) trial showed a survival benefit from ICDs in patients with ischemic and nonischemic cardiomyopathy, the DANISH trial (Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure) randomized 1,116 patients with symptomatic systolic heart failure (LVEF ≤35%) not caused by coronary artery disease to receive an ICD (biventricular ICD in applicable candidates) or usual clinical care. The study showed no significant difference in survival between the two groups after a median follow-up period of 67.6 months. Death from any cause had occurred in 21.6% in the ICD group, and in 23.4% in the control group (hazard ratio, 0.87; 95% CI 0.68 to 1.12; P=0.28).9 In this study, 90% of subjects were taking angiotensin-converting-enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) and beta blockers, and 58% of the study patients were receiving cardiac resynchronization therapy (CRT). The study concluded that prophylactic ICD implantation in patients with symptomatic systolic heart failure not caused by coronary artery disease was not associated with a significantly lower long-term rate of death from any cause than was usual clinical care. This study questions the benefit of ICD in the patients with nonischemic cardiomyopathy who have received contemporary medical and resynchronization therapy.
Cardiac Resynchronization Therapy (CRT)
- The SEPTAL CRT Study (Comparison of right ventricular septal (RVS) pacing and right ventricular apical (RVA) pacing in patients receiving cardiac resynchronization therapy defibrillators) randomized 263 patients who underwent cardiac resynchronization therapy defibrillator CRT-D implantation to RVS vs. RVA pacing. Left ventricular end-systolic volume (LVESV) reduction between baseline and 6 months was not different between the two groups (-25.3 ± 39.4 mL in RVS group vs. -29.3 ± 44.5 mL in RVA group, P = 0.79). The percentage of 'echo-responders' defined by LVESV reduction >15% between baseline and 6 months was similar in both. The study concluded septal RV pacing in CRT is non-inferior to apical RV pacing for LV reverse remodeling at 6 months with no difference in the clinical outcome.10
MRI Compatible cardiac Implantable Electronic Devices (CIEDs)
- Following the FDA approval in late 2015 of the first ICD system approved for use during magnetic resonance imaging (MRI) scans, 2016 saw the expansion of additional FDA-approved MRI-conditional CIEDs and lead systems, including CRT-D systems, additional pacing systems, and some conventional pacing leads approved for MRI use with MRI-compatible devices. MRI capability is now approved for some systems for total body use without exclusion of chest MRI, and in some systems for up to 3 Tesla scans. The effect of the devices on image quality remains to be ascertained and is under study.
CIED Implant Complication
- The BRUISE CONTROL INFECTION Study (Clinically Significant Pocket Hematoma Increases Long-Term Risk of Device Infection) prospectively examined the association between clinically significant pocket hematoma and subsequent device infection. The study included 659 patients and found an overall 1-year device-related infection rate of 2.4% (16 of 659). Infection occurred in 11% of patients with and in 1.5% without previous pocket hematoma. Unfortunately, empiric antibiotics upon development of hematoma did not reduce long-term infection risk.11
- While there have been many advances in CIEDs, the year was also marked by battery recalls. A potential for sudden loss of pacing of a new leadless pacemaker system (St. Jude Nanostim) led to cessation of new implants and a recommendation for device replacement in pacemaker dependent patients. Another potential battery malfunction due to deposits of lithium clusters led to an advisory in a family of ICDs and CRT-Ds (St. Jude Medical) after there were reports of 2 deaths and syncope or dizziness in several other patients.
- Reynolds D, Duray GZ, Omar R, et al. A Leadless Intracardiac Transcatheter Pacing System. N Engl J Med 2016;374:533-41.
- Sharma PS, Ellenbogen KA, Trohman RG. Permanent His Bundle Pacing: The Past, Present and Future. J Cardiovasc Electrophysiol 2016. [Epub ahead of print].
- Upadhyay GA, Tung R. Selective versus non-selective his bundle pacing for cardiac resynchronization therapy. J Electrocardiol 2016;50:191-4.
- Mulpuru SK, Cha YM, Asirvatham SJ. Synchronous ventricular pacing with direct capture of the atrioventricular conduction system: Functional anatomy, terminology, and challenges. Heart Rhythm 2016;13:2237-46.
- Deshmukh A, Deshmukh P. His bundle pacing: Initial experience and lessons learned. J Electrophysiol 2016;49:658-63.
- Dandamudi G, Vijayaraman P. How to perform permanent His bundle pacing in routine clinical practice. Heart Rhythm 2016;13:1362-6.
- Dandamudi G, Vijayaraman P. The Complexity of the His Bundle: Understanding Its Anatomy and Physiology through the Lens of the Past and the Present. Pacing Clin Electrophysiol 2016;39:1294-7.
- Teng AE, Lustgarten DL, Vijayaraman P, et al. Usefulness of His Bundle Pacing to Achieve Electrical Resynchronization in Patients With Complete Left Bundle Branch Block and the Relation Between Native QRS Axis, Duration, and Normalization. Am J Cardiol 2016;118:527-34.
- Kober L, Thune JJ, Nielsen JC, et al. Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure. N Engl J Med 2016;375:1221-30.
- Leclercq C, Sadoul N, Mont L, et al. Comparison of right ventricular septal pacing and right ventricular apical pacing in patients receiving cardiac resynchronization therapy defibrillators: the SEPTAL CRT Study. Eur Heart J 2016;37:473-83.
- Essebag V, Verma A, Healey JS, et al. Clinically Significant Pocket Hematoma Increases Long-Term Risk of Device Infection: BRUISE CONTROL INFECTION Study. J Am Coll Cardiol 2016;67:1300-8.
Keywords: Angiotensin Receptor Antagonists, Angiotensin-Converting Enzyme Inhibitors, Anti-Bacterial Agents, Cardiac Resynchronization Therapy, Cardiac Resynchronization Therapy Devices, Arrhythmias, Cardiac, Cardiomyopathies, Coronary Artery Disease, Defibrillators, Implantable, Heart Failure, Systolic, Heart Ventricles, Magnetic Resonance Imaging, Syncope, Thrombosis, Tricuspid Valve Insufficiency
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