Low inappropriate shock rates in patients with single- and dual/triple-chamber implantable cardioverter-defibrillators using a novel suite of detection algorithms: PainFree SST trial primary results

Results of ENHANCED Implantable Cardioverter Defibrillator Programming to Reduce Therapies and Improve Quality of Life (from the ENHANCED-ICD Study)

Novel implantable cardioverter defibrillator (ICD) discrimination algorithms and programming strategies have significantly reduced the incidence of inappropriate shocks, but there are still gains to be made with respect to reducing appropriate but unnecessary antitachycardia pacing (ATP) and shocks. We examined whether programming a number of intervals to detect (NID) of 60/80 for ventricular tachyarrhythmia (VT)/ventricular fibrillation (VF) detection was safe and the impact of this strategy on (1) adverse events related to ICD shocks and syncopal events; (2) ATPs/shocks; and (3) patient-reported outcomes. The "ENHANCED Implantable Cardioverter Defibrillator programming to reduce therapies and improve quality of life" study (ENHANCED-ICD study) was a prospective, safety-monitoring study enrolling 60 primary and secondary prevention patients at the University Medical Center Utrecht. Patients implanted with any type of ICD with SmartShock technology and aged 18 to 80 years were eligible to participate. In all patients, a prolonged NID 60/80 was programmed. The cycle length for VT/fast VT/VF was 360/330/240 ms, respectively. Programming a NID 60/80 proved safe for ICD patients. Because of the new programming strategy, unnecessary ICD therapy was prevented in 10% of ENHANCED-ICD patients during a median follow-up period of 1.3 years. With respect to patient-reported outcomes, levels of distress were highest and perceived health status lowest at the time of implantation, which both gradually improved during follow-up. In conclusion, the ENHANCED-ICD study demonstrates that programming a NID 60/80 for VT/VF detection is safe for ICD patients and does not negatively impact their quality of life.

Reduction of inappropriate anti-tachycardia pacing therapies and shocks by a novel suite of detection algorithms in heart failure patients with cardiac resynchronization therapy defibrillators: a historical comparison of a prospective database

AIMS

Implantable cardioverter defibrillators improve survival of patients at risk for ventricular arrhythmias, but inappropriate shocks occur in up to 30% of patients and have been associated with worse quality of life and prognosis. In heart failure patients with cardiac resynchronization therapy defibrillators (CRT-Ds), we evaluated whether a new generation of detection and discrimination algorithms reduces inappropriate shocks.

METHODS AND RESULTS

We analysed 1983 Medtronic CRT-D patients (80% male, 67 ± 10 years), 1368 with standard devices (Control CRT-D) and 615 with new generation devices (New CRT-D). Expert electrophysiologists reviewed and classified the electrograms of all device-detected ventricular tachycardia/fibrillation episodes. Total follow-up was 3751 patients-years. Incidence of inappropriate shocks at 1 year was 2.8% [95% confidence interval (CI) = 2.0-3.5] in Control CRT-D and 0.9% (CI = 0.4-2.2) in New CRT-D (hazard ratio = 0.37, CI = 0.21-0.66, P < 0.001). In New CRT-D, inappropriate shocks were reduced by 77% [incidence rate ratio (IRR) = 0.23, CI = 0.16-0.35, P < 0.001] and inappropriate anti-tachycardia pacing by 81% (IRR = 0.19, CI = 0.11-0.335, P < 0.001). Annual rate per 100 patient-years for appropriate VF detections was 3.0 (CI = 2.1-4.2) in New CRT-D and 3.2 (CI = 2.1-5.0) in Control CRT-D (P = 0.68), for syncope was 0.4 (CI = 0.2-0.9) in New CRT-D and 0.7 (CI = 0.5-1.0) in Control CRT-D (P = 0.266), and for death was 1.0 (CI = 0.6-1.6) in New CRT-D and 3.5 (CI = 3.0-4.1) in Control CRT-D (P < 0.001).

CONCLUSION

Detection and discrimination algorithms used in new generation CRT-D significantly reduced inappropriate shocks when compared with standard CRT-D. This result, with no compromise on VF sensitivity or risk of syncope, has important implications for patients' quality of life and prognosis.

Cardiac Resynchronization in Patients with Atrial Fibrillation

Atrial fibrillation (AF) occurs in one of four patients undergoing cardiac resynchronization therapy (CRT).-Without special therapy, the prognosis of AF patients with CRT has been generally worse than those in sinus rhythm. The importance of a high percentage of biventricular pacing (BIV%) was confirmed in a large study where the mortality was inversely associated with BIV% both in the presence of normal sinus and atrial paced rhythm and with AF. The greatest reduction in mortality was observed with BIV% >98%. Patients with BIV% >99.6% experienced a 24% reduction in mortality (p < 0.001) while those with BIV% <94.8% had a 19% increase in mortality. The optimal BIV% cut-point was 98.7%. This cutoff would appear mandatory but it would be best to approach 100%. Careful evaluation of device interrogation data upon which the BiV% is based is essential because the memorized data can vastly overestimate the percentage of truly resynchronized beats since it does not account for fusion and pseudofusion between intrinsic (not paced) and paced beats. The recently published randomized CERTIFY trial provides unequivocal proof of the value of AV junctional (AVJ) ablation in CRT patients with AF. This trial confirmed the favorable results of AVJ ablation by many other studies and two important meta-analyses and therefore established the firm recommendation that the procedure should be performed in most, if not all, patients with permanent AF as well as those with frequent and prolonged episodes of paroxysmal AF. Patients after AVJ have improved mortality with a mortality similar to those in sinus rhythm. The AVJ ablation procedure carries the theoretical risk of device failure and death in pacemaker dependent patients. An inappropriate first ICD shock for AF seems to increase mortality. Increased long-term mortality after an inappropriate shock may be due to the underlying atrial arrhythmia substrate as opposed to the effect of the shock itself.

Incidence of arrhythmias in a large cohort of patients with current implantable cardioverter-defibrillators in Spain: results from the UMBRELLA Registry

AIMS

The benefit of implantable cardioverter-defibrillators (ICDs) in patients at risk of sudden death has been established in randomized clinical trials (RCTs) using the ICD models available at the time. However, observational large-scale data on the incidence of arrhythmias in up-to-date ICDs implanted according to the current guidelines are scarce. The aim was to assess the incidence of arrhythmias in a large, current ICD population based on a blinded peer review of the detected episodes.

METHODS AND RESULTS

UMBRELLA is a multicentre, observational registry of ICD patients followed by remote monitoring. Stored episodes were classified by a blinded committee of experts. Subgroup analyses were based on clinical profiles established by previous pivotal RCTs of ICDs. Of 1514 enrolled patients, 605 (39.9%) patients had 5951 episodes after 26 ± 17 months follow-up, being 3353 of them (56.3%) sustained ventricular arrhythmias (SVA), and 13.2% of SVA were self-terminated. Appropriate and inappropriate shocks occurred in 11.6 and 5% of patients, respectively. The 3 years cumulative incidence of SVA was 25% (95% CI: 21-28%) in primary prevention patients and 41% (95% CI: 36-47%) in secondary prevention patients (P < 0.001). Male gender, secondary prevention, and atrial fibrillation as basal rhythm were significantly related to a higher incidence of SVA.

CONCLUSION

This real-world analysis suggests that modern ICD patients have a low rate of appropriate and inappropriate shocks. The risk of SVA in secondary prevention patients is less than what has been reported in RCTs.

A case of inappropriate implantable cardioverter defibrillator therapy induced by T-wave oversensing due to hyperkalemia

There have been reports of hyperkalemia-induced T-wave oversensing in patients with implantable cardioverter defibrillators (ICDs). However, a comparison of T-wave amplitudes and morphologies between the surface 12-lead electrocardiogram (ECG) and ICD electrogram has not been reported. We present the case of a 70-year-old man who received inappropriate ICD shocks due to hyperkalemia-induced T-wave oversensing. The T-wave amplitudes on both the ICD electrogram and 12-lead ECG corresponded and normalized after normalization of the potassium level.

[Inappropriate ICD therapies: All problems solved with MADIT-RIT?]

The MADIT-RIT study represents a major trial in implantable cardioverter-defibrillator (ICD) therapy that was recently published. It highlights that different programming strategies (high rate cut-off or delayed therapy versus conventional) reduce inappropriate ICD therapies, leave syncope rates unaltered and can improve patient's survival. The study should motivate cardiologist and electrophysiologists to reconsider their individual programming strategies. However, as the study represents largely patients with ischemic or dilated cardiomyopathy for primary prevention of sudden cardiac death supplied with a dual chamber or cardiac resynchronisation therapy ICD, the results may not easily be transferable to other entities or other device types. Despite the success of the MADIT-RIT study efforts still need to be taken to further optimise device algorithms to avert inappropriate therapies. Optimised ICD therapy also includes the avoidance of unnecessary ICD shocks as well as the treatment of all aspects of the underlying cardiac disease.