A comparison of empiric to physician-tailored programming of implantable cardioverter-defibrillators: results from the prospective randomized multicenter EMPIRIC trial

Sensing and detection in Medtronic implantable cardioverter defibrillators

Ensuring sensing and detection of ventricular tachycardia (VT) and ventricular fibrillation (VF) was a prerequisite for the clinical trials that established the survival benefit of implantable cardioverter defibrillators (ICDs). However, for decades, a high incidence of unnecessary shocks limited patients' and physicians' acceptance of ICD therapy. Oversensing, misclassification of supraventricular tachycardia (SVT) as VT, and self-terminating VT accounted for the vast majority of unnecessary shocks. Medtronic ICDs utilize sensitive baseline settings with minimal blanking periods to ensure accurate sensing of VF, VT, and SVT electrograms. Programmable algorithms reject oversensing caused by far-field R waves, T waves, and non-physiologic signals caused by lead failure. A robust hierarchy of SVT-VT discriminators minimize misclassification of SVT as VT. These features, combined with evidence-based programming, have reduced the 1‑year inappropriate shock rate to 1.5 % for dual-/triple-chamber ICDs and to 2.5 % for single-chamber ICDs.

Ventricular Tachycardia Ablation versus Escalation of Antiarrhythmic Drugs

BACKGROUND

Recurrent ventricular tachycardia among survivors of myocardial infarction with an implantable cardioverter-defibrillator (ICD) is frequent despite antiarrhythmic drug therapy. The most effective approach to management of this problem is uncertain.

METHODS

We conducted a multicenter, randomized, controlled trial involving patients with ischemic cardiomyopathy and an ICD who had ventricular tachycardia despite the use of antiarrhythmic drugs. Patients were randomly assigned to receive either catheter ablation (ablation group) with continuation of baseline antiarrhythmic medications or escalated antiarrhythmic drug therapy (escalated-therapy group). In the escalated-therapy group, amiodarone was initiated if another agent had been used previously. The dose of amiodarone was increased if it had been less than 300 mg per day or mexiletine was added if the dose was already at least 300 mg per day. The primary outcome was a composite of death, three or more documented episodes of ventricular tachycardia within 24 hours (ventricular tachycardia storm), or appropriate ICD shock.

RESULTS

Of the 259 patients who were enrolled, 132 were assigned to the ablation group and 127 to the escalated-therapy group. During a mean (±SD) of 27.9±17.1 months of follow-up, the primary outcome occurred in 59.1% of patients in the ablation group and 68.5% of those in the escalated-therapy group (hazard ratio in the ablation group, 0.72; 95% confidence interval, 0.53 to 0.98; P=0.04). There was no significant between-group difference in mortality. There were two cardiac perforations and three cases of major bleeding in the ablation group and two deaths from pulmonary toxic effects and one from hepatic dysfunction in the escalated-therapy group.

CONCLUSIONS

In patients with ischemic cardiomyopathy and an ICD who had ventricular tachycardia despite antiarrhythmic drug therapy, there was a significantly lower rate of the composite primary outcome of death, ventricular tachycardia storm, or appropriate ICD shock among patients undergoing catheter ablation than among those receiving an escalation in antiarrhythmic drug therapy. (Funded by the Canadian Institutes of Health Research and others; VANISH ClinicalTrials.gov number, NCT00905853.).

Cardiac Resynchronization Therapy and Implantable Cardioverter Defibrillator Therapy in Advanced Heart Failure

Patients with advanced heart failure are at high risk for progression of their disease and sudden cardiac death. The role of device therapy in this patient population continues to evolve and is directed toward improving cardiac pump function and/or reducing sudden arrhythmic death.

Positive Psychotherapy to Improve Autonomic Function and Mood in ICD Patients (PAM-ICD): Rationale and Design of an RCT Currently Underway

BACKGROUND

Improving mental and physical health of patients with implantable cardioverter defibrillators (ICD) is critical because this group is at high risk for ventricular arrhythmias and sudden death and depressed or anxious cardiovascular disease (CVD) patients appear to be at even higher risk for mortality compared to nondepressed or nonanxious CVD patients. Further, autonomic dysfunction is present in these patients, and negative emotions and arrhythmias form a downward spiral further worsening mood, well-being, and cardiovascular health. Much research demonstrates that positive emotion is related to health benefits, improved physiology, and increased survival.

METHODS AND RESULTS

This is a two-arm randomized controlled trial aiming to recruit 60 adult ICD patients comparing 12 individually delivered, weekly sessions of: (1) a positive emotion-focused cognitive-behavioral therapy (Quality of Life Therapy [QOLT]), and (2) Heart Healthy Education. Autonomic functioning, heart rhythm indices, and psychosocial health are measured at baseline, 3 months, and 9 months. The first goal is feasibility and acceptability, with the primary outcome being arrhythmic event frequency data.

CONCLUSION

This study is designed to test whether QOLT produces changes in mood, quality of life/well-being, autonomic function, and arrhythmic and ICD therapy event rates. This feasibility trial is a foundational step for the next trial of QOLT to help determine whether a 3-month QOLT trial can reduce arrhythmias occurrences among ICD patients, and examine a mechanism of autonomic functioning. This study may help to develop and implement new medical or psychological therapies for ICD patients.

Advances in implantable cardioverter defibrillator therapy

Since the first implant in 1980, implantable cardioverter defibrillator (ICD) technology has progressed rapidly. Modern ICD's have hundreds of programmable options with the general goal of preventing inappropriate shocks and providing shocks for truly life threatening symptomatic ventricular arrhythmias. New studies on ICD programming have shown the benefits of prolonged detection intervals in reaching this goal. Anti-tachycardia pacing (ATP) therapy has become an important adjunct to defibrillator shocks. Remote monitoring technologies have surfaced which have been shown to identify arrhythmias and problems with the device in an expedient fashion. The subcutaneous ICD offers the advantage of avoiding intravascular leads and their inherent risks. Lastly, the current understanding of the effects of MRI in ICD patients has advanced creating new opportunities to provide MRI safely to such patients.

Value of The Wearable Cardioverter Defibrillator (WCD) as a Bridging-Therapy before Implantation of a Cardioverter Defibrillator (ICD)

Wearable cardioverter defibrillators (WCD), initially available in 2002, have recently experienced more routine use in many institutions as a means of preventing sudden cardiac death (SCD) prior to implantable cardioverter defibrillator (ICD) evaluation or implantation. WCD differ from ICD by their noninvasive nature, making them well suited for patient populations who have a chance for significant cardiac recovery (such as after an acute myocardial infarction). Despite their noninvasive nature, WCD treatment of sustained ventricular tachyarrhythmias is highly successful. An additional feature is the use of response buttons, which reduces the number of conscious shocks. Duration of use varies by condition but is typically several weeks to several months. Numerous studies have shown good compliance with WCD use and excellent efficacy. Although few prospective studies have been published, several are in progress including a randomized control trial of high risk patients after myocardial infarction. WCD use is rapidly gaining popularity for patients with recent myocardial infarction, recent-onset cardiomyopathies, and acute or subacute myocarditis. Surgical delays in implanting an indicated ICD or after ICD removal are also common. WCD removal occurs when the patient either qualifies for an ICD implantation or is determined to no longer have elevated SCD risk.

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.

Health economic concerns on cardiac rhythm management devices longevity and how to overcome them

The number of device implantations is in constant increase due to the ageing population, extended indications to implant for preventing sudden cardiac death and treating heart failure. An increase in the number of implants is directly related to a higher number of device replacements and that is one of the most important risk factors for device infection. Therefore, all the above mentioned factors contribute to an increase in the cost for health care system. Currently, several methods help to prolong device battery longevity and consequently reduce the costs, such as: a new battery, drug eluting leads, high impedance leads, algorithm to minimize unnecessary pacing, capture management and correct programming to avoid inappropriate and unnecessary shock in Implantable Cardioverter Defibrillators and Cardiac Resynchronization Therapy devices. Furthermore remote monitoring is very promising to reduce health system costs related to devices.

Sinus rhythm R-wave amplitude as a predictor of ventricular fibrillation undersensing in patients with implantable cardioverter-defibrillator

BACKGROUND

Ventricular fibrillation (VF) is induced during implantable cardioverter-defibrillator (ICD) implantation to ensure that the ICD will sense, detect, and defibrillate VF. ICD implant guidelines state that the amplitude of the sinus rhythm R wave recorded from the ventricular electrogram should have amplitude ≥5 mV. No study has tested the relationship between sinus rhythm R-wave amplitude and VF sensing using modern, transvenous sensing electrodes.

OBJECTIVE

The goal of this study was to determine whether there is a sinus rhythm R-wave amplitude cutoff that can be used to determine which patients are not at risk of VF undersensing.

METHODS

A retrospective analysis of induced and spontaneous VF episodes from 2 clinical trials with 2022 patients was performed. Episodes with undersensing during the initial detection of VF were identified, and the distribution of sinus rhythm R-wave amplitudes for patients with and without VF undersensing was analyzed.

RESULTS

Only 3% of analyzed induced VF episodes were considered to have VF undersensing, and none had clinically significant detection delays. There was no correlation between device-measured, rectified sinus rhythm R-wave amplitude and VF undersensing at the time of implantation or during follow-up, although <4% of patients had sinus rhythm R-waves with amplitude <3 mV.

CONCLUSION

We analyzed true bipolar sensing of induced VF or spontaneous ventricular tachycardia/VF detected in the ICD VF zone. Sensing of VF was so reliable that clinically significant undersensing did not occur. Our findings do not support any recommended minimum sinus rhythm R wave to ensure reliable sensing of VF or the necessity of inducing VF to verify sensing for rectified sinus rhythm R-waves with amplitude ≥3 mV.

[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.

Reduction of inappropriate ICD therapies in patients with primary prevention of sudden cardiac death: DECREASE study

BACKGROUND

A significant number of patients with an implantable cardioverter/defibrillator (ICD) for primary prevention receive inappropriate shocks. Previous studies have reported a reduction of inappropriate therapies with simple modifications of ICD detection settings, however, inclusion criteria and settings varied markedly between studies. Our aim was to investigate the effect of raising the ICD detection zone in the entire primary prevention ICD population.

METHODS AND RESULTS

543 patients receiving an ICD for primary prevention were randomized to either conventional or progressive ICD programming. The detection rate was programmed at 171 bpm for ventricular tachycardia (VT) and 214 bpm for ventricular fibrillation (VF) in the Conventional group and 187 bpm for VT and 240 bpm for VF in the Progressive group. 43 % of patients received single-chamber and 57 % dual-chamber detection devices (DDD-ICD 19 %; CRT-D 38 %). The primary endpoint consisted of inappropriate therapies and untreated VT/VF. The primary endpoint was reached in 35 patients (13 %) in the Conventional group and 17 patients (6 %) in the Progressive group (p = 0.004). Progressive ICD programming led to significantly fewer amount of patients with ICD therapies (26 vs. 14 %; p < 0.001) and shocks (11 vs. 5 %; p = 0.023) compared to conventional ICD programming. Sub-analyses showed the greatest reduction of inappropriate therapies and shocks in dual-chamber detection devices with progressive compared to single-chamber detection devices with conventional ICD programming (p < 0.001).

CONCLUSIONS

Progressive ICD programming reduces the number of inappropriate therapies and shocks in a broad primary prevention ICD population particularly in combination with dual-chamber detection algorithms.

CLINICAL TRIAL REGISTRATION

http://clinicaltrials.gov ; ClinicalTrials.gov identifier NCT01217528.

Programming implantable cardioverter-defibrillator therapy zones to high ranges to prevent delivery of inappropriate device therapies in patients with primary prevention: results from the RISSY-ICD (Reduction of Inappropriate ShockS bY InCreaseD zones) trial

Inappropriate shock is a frequently seen clinical problem despite advanced technologies used in modern implantable cardioverter-defibrillator (ICD) devices. Our aim was to investigate whether simply raising the ICD detection zones can decrease inappropriate therapies while still providing appropriate therapy. We randomized 223 patients with primary prevention to either the conventional programming group with 3 zones as VT1 (167 to 182 beats/min) with discriminators, VT2 (182 to 200 beats/min) with discriminators, and ventricular fibrillation (>200 beats/min) (n=100) or the high-zone programming group with 3 zones as VT1 (171 to 200 beats/min) with discriminators, VT2 (200 to 230 beats/min) with discriminators, and ventricular fibrillation (>230 beats/min; n=101). Twenty-two patients were lost to follow-up. The primary objectives were the first episode of appropriate and inappropriate therapies. The secondary objectives were all-cause mortality and hospitalization for heart failure. During 12-month follow-up, the first episode of appropriate therapy was higher (22% vs 10%, hazard ratio [HR] 2.18, 95% confidence interval [CI], 1.09 to 4.36, p=0.028) and the first episode of inappropriate therapy was lower (5% vs 28%, HR 0.18 [95% CI 0.07 to 0.44], p<0.001) in the high-zone group compared with the conventional group. Although all-cause mortality did not differ (2% for the high-zone group vs 3% for the conventional group, HR 0.65 [95% CI 0.11 to 3.99], p>0.05), hospitalization for heart failure was significantly higher in the conventional group (13% vs 4%, HR 0.28 [95% CI 0.09 to 0.88], p=0.021). In conclusion, in a real-world population, high-zone settings of the single-, dual-, and triple-chamber ICDs were associated with reduction in inappropriate therapy while still providing appropriate therapy.

Antitachycardia pacing for reduction of implantable cardioverter-defibrillator shocks

Antitachycardia pacing (ATP) strategies represent safe, effective, and painless therapy for ventricular tachyarrhythmias, with a large body of clinical evidence supporting their routine use in both primary and secondary implantable cardioverter-defibrillator recipients. This article details the evidence supporting the use of standardized and validated ATP strategies for primary prevention patients and the conceptual framework to design effective ATP strategy for secondary prevention patients.

Clinical course and prognostic relevance of antitachycardia pacing-terminated ventricular tachyarrhythmias in implantable cardioverter-defibrillator patients

AIMS

In patients with an implantable cardioverter-defibrillator (ICD), ICD shocks due to ventricular tachycardia (VT) or ventricular fibrillation (VF) have been associated with an increased mortality. It is not known whether patients with antitachycardia pacing (ATP)-terminated VT/VF episodes have a similar worse outcome. The aim of this study was to evaluate the clinical course and prognostic impact of ATP-terminated episodes on mortality in ICD patients.

METHODS AND RESULTS

A total of 1398 consecutive patients of the prospective single-centre ICD-registry Ludwigshafen who underwent an ICD implantation between 1992 and 2008 for primary or secondary prevention of sudden cardiac death were analysed. Patients treated with ATP were compared with patients with appropriate ICD shocks or patients without any appropriate ATP or ICD shock. During the median follow-up time of 6 years, 749 (54%) patients experienced 17 827 episodes of VT or VF which were terminated by ATP in 74% and by shock in 26% of patients. In approximately half (n = 321/749) of those patients with VT/VF, the first episode was terminated by ATP. In a multivariate analysis adjusted for different baseline confounding parameters, the occurrence of first ATP therapy was associated with a higher mortality rate [hazard ratio (HR) 2.60, 95% confidence interval (CI) 2.02-3.35]. When excluding all patients with appropriate ICD shocks first ATP therapy remained associated with a worse prognosis (HR 1.92, 95% CI 1.38-2.67).

CONCLUSIONS

In ICD patients, about three-fourths of ventricular arrhythmias are terminated by ATP. The occurrence of ATP-terminated episode is associated with an increased mortality rate.

The implantable cardioverter-defibrillator: An update

The implantable cardioverter-defibrillator (ICD) provides life-saving therapy to prevent sudden cardiac death. ICDs have been implanted in millions of patients worldwide since the first human implant in 1980. Clinical trials have helped establish guidelines for ICD implantation in primary and secondary prevention of sudden cardiac death. Recent trials have also tested and compared various programing strategies to avoid unnecessary shocks and improve survival among ICD recipients. ICDs may also assist with monitoring for heart failure management. In this review, we discuss the clinical science to date that has helped define the role of ICDs in current practice.

Examination of the differential impacts of antitachycardia pacing vs. shock on patient activity in the EMPIRIC study

AIMS

Implantable cardioverter defibrillators (ICDs) have demonstrated mortality advantages over antiarrhythmic drug therapy, but ICD shock has known detrimental effects on quality of life and psychologic functioning. However, it remains unknown how patient activity level is affected by shock, or by antitachycardia pacing (ATP), which was developed to reduce the treatment burden of shocks. Examine the differential impact of ICD shock and ATP on patient activity level as a novel way to capture the relative behavioural repercussions of these ICD therapies.

METHODS AND RESULTS

Accelerometer-derived activity data were analysed for a subset of patients (males = 83%; mean age = 62 years) enrolled in the EMPIRIC trial who received shock (n = 71) or ATP (n = 103). Differences in activity between a week pre-therapy and a week post-therapy were examined to assess the behavioural repercussions of shock vs. ATP when one, few (2-4), or many (5+) therapies were delivered. For patients receiving shock, a significant reduction in activity was observed for few (-26%) and many shocks (-34%) in the first week post-therapy (P < 0.05). In weeks 2-4, activity levels recovered towards baseline levels. In contrast, no level of ATP-only therapy significantly reduced patients' activity levels at any time following therapy.

CONCLUSION

This study is the first to evaluate objective, behavioural effects of shock, and whether these effects are comparable with ATP therapy alone. In tandem with existing literature, current results highlight that ICD shocks and ATP have divergent effects on behavioural outcomes, with ATP's effect profile in these domains appearing somewhat favourable.

ICD programming to reduce shocks and improve outcomes

Despite the clinical benefit of implantable cardioverter defibrillator (ICD), there is a high frequency of inappropriate ICD therapy associated with impaired quality of life, unwanted health care resource utilization, and adverse clinical outcome. Alternative strategies of ICD programming are needed to reduce the risk of inappropriate and "unnecessary" ICD therapies and to improve patient outcome. In this review, we provide an overview of the rate of inappropriate and appropriate ICD therapies in clinical trials and large registries as well as a review of current trials evaluating novel ICD programming to reduce inappropriate ICD therapy to avoid unnecessary ICD therapy. Based on recent studies including a large randomized trial, we recommend a simple programming approach involving high-rate device therapy beginning at 200 bpm with a 2.5 sec delay for it reduces inappropriate therapy, unnecessary therapy, and all-cause mortality in patients receiving ICD or CRT-D devices for primary prevention indications.

Programming implantable cardioverter/defibrillators and outcomes

Implantable cardioverter-defibrillators are complex technical devices with a multitude of programming options for the physician. In recent years, numerous randomized trials have been performed to define the optimal programming strategies and have provided valuable insights, especially in primary prevention patients. This article provides an actual overview on the existing evidence on the most important programming features for accurate detection and therapy of ventricular arrhythmias.

Effectiveness of antitachycardia pacing therapy after primary prophylaxis implantation of implantable defibrillators in coronary artery disease patients

PURPOSE

Effectiveness of implantable defibrillators (ICD) has been proven with large randomized trials. Unfortunately, ICD discharge is painful and potentially threatening for the patient despite its life saving effects. We analyzed influence of the clinical parameters present before implantation on the effectiveness of antitachycardia pacing therapy (ATP) in terminating ventricular tachycardia (VT) slower than 200 bpm in the coronary artery disease patients with prophylactic implanted ICD in a single centre retrospective trial.

PATIENTS/METHODS

We analyzed 121 consecutive coronary disease patients with ICD implanted in primary prophylaxis between 2001 and 2007, with the mean age of 62 ± 10 years. The mean follow-up was 876 ± 538 days.

RESULTS

32 of them had VT. In 27 persons (84.4%) at least one ATP attempt terminate VT. ATP was always successful in 21 patients. We analyzed age, sex, LVEF, NYHA class, widening of QRS complex, atrial fibrillation, type of myocardial infarction or diabetes. There were no significant differences in clinical features between patients with successful and unsuccessful ATP therapy.

CONCLUSIONS

High effectiveness of ATP was shown in this group. There were no clinical factors indicating success of this type of therapy. That could justify programming ATP as the first line therapy in the VT zone in primary prophylaxis coronary artery disease patients to reduce application of shock therapy. It should be possible to apply a single mode of programming when discharging patients after the implantation procedure regardless of the patient's clinical condition. This could help to control and programme the devices, thus reducing the risk of errors.

Spinal cord stimulation is safe and feasible in patients with advanced heart failure: early clinical experience

AIMS

Pre-clinical work suggests that upper thoracic spinal cord stimulation (SCS) may have therapeutic effects in the treatment of heart failure (HF). We therefore aim to assess the safety and feasibility of SCS in HF patients.

METHODS AND RESULTS

A prospective, randomized, double-blind, crossover pilot study was conducted in symptomatic HF patients receiving optimal medical therapy. Patients were implanted with an SCS system and randomized to an SCS-ACTIVE, delivered at 90% paraesthesia threshold, or an SCS-INACTIVE phase for 3 months, followed by a 1-month washout period and crossover to the alternative phase. The safety of SCS therapy was assessed by death and cardiac events. Implantable cardioverter defibrillator (ICD) function in the presence of SCS was tested by defibrillation testing during SCS system implant and review of real-time and stored electrograms during follow-up. The efficacy of SCS therapy was assessed by changes in patient symptoms, LV function, and BNP level. Nine patients were investigated. In all cases, ICD sensing, detection, and therapy delivery were unaffected by SCS. During follow-up, one patient died and one was hospitalized for HF while in the SCS-INACTIVE phase, and two patients had HF hospitalizations during the SCS-ACTIVE phase. Symptoms were improved in the majority of patients with SCS, while markers of cardiac structure and function were, in aggregate, unchanged.

CONCLUSION

This study shows that an SCS system can be safely implanted in patients with advanced HF and that the SCS system does not interfere with ICD function.

Reduction of the inappropriate ICD therapies by implementing a new fuzzy logic-based diagnostic algorithm

AIMS

The aim of the study was to analyze the value of a completely new fuzzy logic-based detection algorithm (FA) in comparison with arrhythmia classification algorithms used in existing ICDs in order to demonstrate whether the rate of inappropriate therapies can be reduced.

METHODS

On the basis of the RR intervals database containing arrhythmia events and controls recordings from the ICD memory a diagnostic algorithm was developed and tested by a computer program. This algorithm uses the same input signals as existing ICDs: RR interval as the primary input variable and two variables derived from it, onset and stability. However, it uses 15 fuzzy rules instead of fixed thresholds used in existing devices. The algorithm considers 6 diagnostic categories: (1) VF (ventricular fibrillation), (2) VT (ventricular tachycardia), (3) ST (sinus tachycardia), (4) DAI (artifacts and heart rhythm irregularities including extrasystoles and T-wave oversensing-TWOS), (5) ATF (atrial and supraventricular tachycardia or fibrillation), and 96) NT (sinus rhythm). This algorithm was tested on 172 RR recordings from different ICDs in the follow-up of 135 patients.

RESULTS

All diagnostic categories of the algorithm were present in the analyzed recordings: VF (n = 35), VT (n = 48), ST (n = 14), DAI (n = 32), ATF (n = 18), NT (n = 25). Thirty-eight patients (31.4%) in the studied group received inappropriate ICD therapies. In all these cases the final diagnosis of the algorithm was correct (19 cases of artifacts, 11 of atrial fibrillation and 8 of ST) and fuzzy rules algorithm implementation would have withheld unnecessary therapies. Incidence of inappropriate therapies: 3 vs. 38 (the proposed algorithm vs. ICD diagnosis, respectively) differed significantly (p < 0.05). VT/VF were detected correctly in both groups. Sensitivity and specificity were calculated: 100%, 97.8%, and 100%, 72.9% respectively for FA and tested ICDs recordings (p < 0.05).

CONCLUSIONS

Diagnostic performance of the proposed fuzzy logic based algorithm seems to be promising and its implementation could diminish ICDs inappropriate therapies. We found FA usefulness in correct diagnosis of sinus tachycardia, atrial fibrillation and artifacts in comparison with tested ICDs.

ICD programming

BACKGROUND

Appropriate ICD programming is the key to prevent inappropriate shock delivery, that is closely associated to a negative patients' outcome.

METHODS

Review of the literature on ICD therapy to generate ICD programmings that can be applied to the broad population of ICD and CRT-D carriers.

RESULTS

Arrhythmia detection should occur with a detection time ranging 9″-12″ in the VF zone, and 15″-60″ in the VT zone. Discriminator should be applied at least up to 200 bpm. ATP therapy is applied to all VTs up to 250 bpm, with a success rate of 70%. Inappropriate shocks should occur in <3.6% of patients.

CONCLUSION

Tailored ICD programming can be achieved following evidence from large ICD trials. Pre-defined settings that are saved on the programmer and that can be uploaded at device implantation help to ensure optimal programming and to avoid random errors.

Usefulness of sleep-disordered breathing to predict occurrence of appropriate and inappropriate implantable-cardioverter defibrillator therapy in patients with implantable cardioverter-defibrillator for primary prevention of sudden cardiac death

Advanced heart failure (HF) is associated with severe sleep-disordered breathing (SDB). In addition, most patients with HF are treated with an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death. The incidence of ICD therapy in such a patient cohort with SDB has never been investigated. The present study sought to determine the effect of SDB on the incidence of appropriate and inappropriate ICD therapy in patients with a categorical primary prevention ICD indication. A total of 133 consecutive ICD patients with New York Heart Association class II-III HF and depressed left ventricular function (≤35%) with no history of ventricular arrhythmia underwent a sleep study before ICD implantation and were followed for 24 ± 8 months, prospectively. A relevant SDB was defined as an apnea-hypopnea index of ≥10 events/hour. Of these 133 patients, 82 (62%) had SDB. Overweight (body mass index >29.1 vs 24.7 kg/m(2); p <0.001) was identified as the only independent risk factor for SDB. Appropriate ICD therapy intervention was significantly greater among patients with SDB than among patients without SDB (54% vs 34%, p = 0.03). Inappropriate ICD therapy intervention was documented more often in patients with SDB (n = 24 [29%] vs 7 [14%]; p = 0.04). An apnea-hypopnea index >10 events/hour was an independent predictor of appropriate ICD therapy on multivariate analysis (odds ratio 2.5, 95% confidence interval 1.8 to 4.04; p = 0.01). In conclusion, the present study is the first trial exploring the effect of SDB on the incidence of appropriate and inappropriate ICD therapy in patients with HF with a primary prevention indication. These results indicate that a preimplantation sleep study will identify patients with HF prone to receive appropriate and inappropriate ICD therapy.

Primary prevention of sudden cardiac death in a nonischemic dilated cardiomyopathy population: reappraisal of the role of programmed ventricular stimulation

BACKGROUND

We considered the role of programmed ventricular stimulation in primary prevention of sudden cardiac death in an idiopathic dilated cardiomyopathy population.

METHODS AND RESULTS

One hundred fifty-eight patients with idiopathic dilated cardiomyopathy underwent programmed ventricular stimulation. Ventricular tachycardia/ventricular fibrillation was triggered in 44 patients (group I, 27.8%) versus 114 patients (group II), where ventricular tachycardia/ventricular fibrillation was not induced. Sixty-nine patients with idiopathic dilated cardiomyopathy underwent implantable cardioverter-defibrillator (ICD) implantation: 41/44 in group I and 28/114 in group II. The major end points of the study were overall mortality and appropriate ICD activation. Overall mortality during the 46.9 months of mean follow-up was not significantly different between the 2 groups. Patients with left ventricular ejection fraction ≤35% (n=119) demonstrated a higher overall mortality rate compared with the patients with left ventricular ejection fraction >35% (n=39; 16.8% versus 10.3%, log-rank P=0.025). Advanced New York Heart Association class (III and IV versus I and II) was the single independent and strongest prognostic factor of overall mortality (hazard ratio, 11.909; P<0.001; confidence interval, 3.106-45.65), as well as of cardiac mortality (hazard ratio, 14.787; P=0.001; confidence interval, 2.958-73.922). Among ICD recipients, ICD activation rate was significantly higher in group I compared with group II (30 of 41 patients-73.2% versus 5 of 28 patients-17.9%; log-rank P=0.001), either in the form of antitachycardia pacing (68.3% versus 17.9%; log-rank P=0.001) or in the shock delivery form (51.2% versus 17.9%; log-rank P=0.05). Induction of ventricular tachycardia/ventricular fibrillation during programmed ventricular stimulation in contrast to left ventricular ejection fraction was the single independent prognostic factor for future ICD activation (hazard ratio, 4.195; P=0.007; confidence interval, 1.467-11.994).

CONCLUSIONS

Inducibility of ventricular tachycardia/ventricular fibrillation was associated with an increased likelihood of subsequent ICD activation and sudden cardiac death surrogate.