Defibrillation Capability Research Articles

The impact of defibrillation lead position on electrical parameters measured perioperatively and in long-term follow-up

Introduction: Implantable cardioverter-defibrillators (ICD) with transvenous defibrillation leads remain the leading therapeutic method in the treatment of patients at high risk of sudden cardiac death. The lack of clear data confirming the superiority of any position in the right ventricle for placement of the defibrillation lead results in significant individualization of practice between operators.Aims: The study aims to assess the electrical parameters of defibrillation leads obtained intraoperatively and in the long-term follow-up, depending on the position of the lead in the right ventricle.Methods: Between 2018 and 2021, consecutive patients were enrolled in an observational study after the implantation of a device with defibrillation capability. Electrical parameters were measured during each control visit, 3 months after the implantation procedure, and then every 6-months during follow-up visits. The data regarding intraprocedural course (procedure time, an X-ray time, intraprocedural electrical parameters) were collected retrospectively. The patients were divided into two groups depending on the placement of the defibrillation lead in the right ventricle: the RVA (right ventricular apex group) and the non-RVA group consisting of patients with the lead implanted in the alternative position.Results: Of the 167 patients included in the study, 90 patients (54%) were assigned to the RVA group and 77 patients (46%) to the non-RVA group. The mean follow-up time was 26.1 12.6 months. Electrical parameters (pacing threshold, ventricular sensing amplitude and impedance) observed intraoperatively and measured on the first day following the procedure did not differ significantly between the groups. There was no significant difference in the incidence of abnormal electrical parameters between the apical and non-apical electrodes throughout the observation period. A total of 4 patients (4%) in the RVA group and 3 patients (4%) in the non-RVA group required lead replacement during the follow-up period.Conclusions: The position of the defibrillation lead has no clinically significant influence on the electrical parameters observed both intraoperatively and in long-term follow-up.

Adverse Outcomes With Cardiac Sarcoid: New Zealand Experience in the Modern Era

Diagnosis of cardiac sarcoidosis (CS) has increased with availability of multi-modal imaging yet presenting phenotype and natural history of the disease remain highly variable. This study evaluated experience in the Auckland/Northland regions between 2004 and 2022. A retrospective observational study of patients with CS defined according to Heart Rhythm Society (HRS) criteria. Demographics, diagnostic presentation, and adverse clinical outcomes were evaluated, including heart failure, ventricular arrhythmia (VA), device therapy, transplant, and death. Ninety-nine patients met diagnostic criteria for CS; median age was 55±11 years and 52% were male. Clinical presentations included symptomatic conduction disease in 53%, new heart failure in 24%, in VA 16%, and incidental in 6%. Diagnosis was confirmed by imaging studies: cardiac MRI in 85 patients (86%) and/or positive computed tomography-positron emission tomography (CT-PET) in 47 (47%), and positive cardiac biopsy in 24 (24%). Devices were implanted in 84 (85%) patients, with defibrillator capability in 67 (80%). Seventy (71%) patients experienced 158 adverse events: death in 13%, heart failure in 28%, VA in 27%, device therapies in 21%, progressive conduction disease in 7%, atrial arrhythmias in 3%, stroke in 1%, and transplant in 6%. Twenty-two patients (26%) did not meet Class I indications for implantable cardioverter defibrillator, but more than one-third required device therapy. A regimen of high-dose steroid (>30 mg prednisone) with a tapering regimen was used in 65% of patients, with additional steroid sparing agents in 55%. Complete disease suppression was assessed by repeat PET at 3 months was observed in 55%. Adverse cardiovascular events are common with CS. Over 50% of patients experience cardiac arrhythmia and consideration of appropriate device therapy is important at diagnosis.

Defibrillator capability and all-cause mortality in patients receiving cardiac resynchronization therapy for non-ischemic cardiomyopathy: a Korean nationwide cohort study

Abstract Funding Acknowledgements Type of funding sources: None. Background Concerns exist about the benefit of cardiac resynchronization therapy with a defibrillator (CRT-D) compared to those without a defibrillator (CRT-P), especially in patients with non-ischemic cardiomyopathy. We evaluated the association between defibrillator capability and all-cause mortality in patients receiving cardiac resynchronization therapy (CRT) for non-ischemic cardiomyopathy. Methods From patients with nationally registered cardiomyopathy in the Korea National Health Insurance Service (KNHIS) database, after the exclusion of those with ischemic heart disease, 1,478 patients with newly-implanted CRT-P (n=258) or CRT-D (n=1220) were identified from 2008 to 2020. The association between defibrillator capability and all-cause mortality was assessed with propensity score (PS) weighting to correct for differences between the groups. Results Compared with patients receiving CRT-D, those receiving CRT-P included more subjects older than 75. After PS weighting, over a mean follow-up period of 52.9 months (interquartile interval: 23.5-75.8), CRT-D was associated with a lower rate of mortality (6.5 vs 9.2 per 100 person-years) compared with CRT-P. The weighted risk of all-cause death in patients with CRT-D was lower than those with CRT-P within 1 year (hazard ratio [HR]: 0.70 [95% CI, 0.53–0.91]; p = 0.009) and 5 years (HR: 0.71 [95% CI, 0.61–0.83]; p < 0.001). Results were consistent regardless of subgroups, such as age, sex, year of registration, and comorbidities. Conclusions In Korean patients with non-ischemic cardiomyopathy, the defibrillator capability of CRT was associated with reduced 1-year and 5-year all-cause mortality. This association was consistent across all the investigated subgroups.

A long-term cost-effectiveness analysis of cardiac resynchronisation therapy with or without defibrillator based on health claims data

BackgroundIn Germany, CRT devices with defibrillator capability (CRT-D) have become the predominant treatment strategy for patients with heart failure and cardiac dyssynchrony. However, according to current guidelines, most patients would also be eligible for the less expensive CRT pacemaker (CRT-P). We conducted a cost-effectiveness analysis for CRT-P devices compared to CRT-D devices from a German payer’s perspective.MethodsLongitudinal health claims data from 3569 patients with de novo CRT implantation from 2014 to 2019 were used to parametrise a cohort Markov model. Model outcomes were costs and effectiveness measured in terms of life years. Transition probabilities were derived from multivariable parametric survival regression that controlled for baseline differences of CRT-D and CRT-P patients. Deterministic and probabilistic sensitivity analyses were conducted.ResultsThe Markov model predicted a median survival of 84 months for CRT-P patients and 92 months for CRT-D patients. In the base case, CRT-P devices incurred incremental costs of € − 13,093 per patient and 0.30 incremental life years were lost. The ICER was € 43,965 saved per life year lost. In the probabilistic sensitivity analysis, uncertainty regarding the effectiveness was observed but not regarding costs.ConclusionThis modelling study illustrates the uncertainty of the higher effectiveness of CRT-D devices compared to CRT-P devices. Given the difference in incremental costs between CRT-P and CRT-D treatment, there would be significant potential cost savings to the healthcare system if CRT-D devices were restricted to patients likely to benefit from the additional defibrillator.

Survival of patients undergoing cardiac resynchronization therapy with or without defibrillator: the RESET-CRT project.

AimsCardiac resynchronization therapy (CRT) is an established treatment for heart failure. There is contradictory evidence whether defibrillator capability improves prognosis in patients receiving CRT. We compared the survival of patients undergoing de novo implantation of a CRT with defibrillator (CRT-D) option and CRT with pacemaker (CRT-P) in a large health claims database.Methods and resultsUsing health claims data of a major German statutory health insurance, we analysed patients with de novo CRT implantation from 2014 to 2019 without indication for defibrillator implantation for secondary prevention of sudden cardiac death. We performed age-adjusted Cox proportional hazard regression and entropy balancing to calculate weights to control for baseline imbalances. The analysis comprised 847 CRT-P and 2722 CRT-D patients. Overall, 714 deaths were recorded during a median follow-up of 2.35 years. A higher cumulative incidence of all-cause death was observed in the initial unadjusted Kaplan–Meier time-to-event analysis [hazard ratio (HR): 1.63, 95% confidence interval (CI): 1.38–1.92]. After adjustment for age, HR was 1.13 (95% CI: 0.95–1.35) and after entropy balancing 0.99 (95% CI: 0.81–1.20). No survival differences were found in different age groups. The results were robust in sensitivity analyses.ConclusionIn a large health claims database of CRT implantations performed in a contemporary setting, CRT-P treatment was not associated with inferior survival compared with CRT-D. Age differences accounted for the greatest part of the survival difference that was observed in the initial unadjusted analysis.

Cardiac Resynchronization Therapy With or Without Defibrillation: A Long-Standing Debate.

Cardiac resynchronization therapy (CRT) was shown to improve cardiac function, reduce heart failure hospitalizations, improve quality of life and prolong survival in patients with severe left ventricular dysfunction and intraventricular conduction disturbances, mainly left bundle branch block, on optimal medical therapy with ACE-inhibitors, β-blockers and mineralocorticoid receptor antagonists up-titrated to maximum tolerated evidence-based doses. CRT can be achieved by means of pacemaker systems (CRT-P) or devices with defibrillation capabilities (CRT-D). CRT-Ds offer an undoubted advantage in the prevention of arrhythmic death, but such an advantage may be of lesser degree in nonischemic heart failure etiologies. Moreover, the higher CRT-D hardware complexity compared to CRT-P may predispose to device/lead malfunctions and the higher current drainage may cause a shorter battery duration with consequent premature replacements and the well-known incremental complications. In a period of financial constraints, also device costs should be carefully evaluated, with recent reports suggesting that CRT-Ps may be favored over CRT-Ds in patients with nonischemic cardiomyopathy and no prior history of cardiac arrhythmias from a cost-effectiveness point of view. The choice between a CRT-P or a CRT-D device should be patient-tailored whenever straightforward defibrillator indications are not present. The Goldenberg score may facilitate this decision-making process in ambiguous settings. Age, comorbidities, kidney disease, atrial fibrillation, advanced functional class, inappropriate therapy risk, implantable device infections, and malfunctions are factors potentially reducing the expected benefit from defibrillating capabilities. In the future, prospective randomized controlled trials are warranted to directly compare the efficacy and safety of CRT-Ps and CRT-Ds.

Sudden cardiac death after implantation of a cardiac resynchronization therapy pacemaker: a case report illustrating that not always less is more.

BackgroundCardiac resynchronization therapy (CRT) improves symptoms and survival in selected patients with systolic heart failure and ventricular conduction delay. In subjects without prior life-threatening ventricular arrhythmia, clinicians have to select between implanting a CRT pacemaker (CRT-P) or a more complex device with additional defibrillator capability (CRT-D). This individual decision can be challenging in light of the available evidence and the potential risks and benefits.Case summaryA 76-year-old male with non-ischaemic cardiomyopathy, heart failure New York Heart Association Class III, left bundle branch block (QRS duration 185 ms) and a left ventricular ejection fraction of 30% despite optimal medical therapy was indicated for CRT. In light of the patient characteristics and clinical condition, a CRT-P device was implanted. No complication occurred, and the patient was discharged after an appropriate device function was confirmed. Despite the clinical improvement, he died suddenly without prior symptoms approximately 2 months thereafter. Post-mortem device interrogation provided no evidence for device malfunction and confirmed sudden cardiac death (SCD) due to spontaneous ventricular fibrillation.DiscussionPatients indicated for CRT often have overlapping internal cardioverter defibrillator indication for the primary prevention of SCD. By weighing individual risks and potential benefits, clinicians have to decide whether to implant a CRT-P (less is more) or a more complex and costly CRT-D device. Despite careful consideration of patient characteristics and clinical conditions, however, SCD can occur in subjects categorized as low risk and implanted with a CRT-P. More data from randomized clinical trials are needed to better support physicians in the often challenging process of selecting the most appropriate device for CRT.

Atrial fibrillation burden and subsequent heart failure events in patients with cardiac resynchronization therapy devices.

Atrial fibrillation (AF) and heart failure (HF) often coexist but little is known on how AF burden associates with subsequent episodes of HF. The aim of this study was to quantitatively assess the short- and long-term association of AF burden with subsequent episodes of HF events in patients with reduced ejection fraction. Patients with cardiac resynchronization therapy (CRT) devices with at least 90 days of device data were included in the study. Time-dependent Cox regression with a 7-day window was used to evaluate the association of short- and long-term AF burden with subsequent HF events. Each patient with HF was matched to two control patients without an HF event based on age, gender, year of implant and CRT defibrillation capability. In our cohort with 2:1 matching (N = 549), 183 patients developed HF events and 275 (50.1%) had AF over an average follow-up of 24 ± 11 months. A 1-hour increase in short-term AF burden was associated with a 3% increased risk of HF events (HR, 1.034; 95% confidence interval [CI], 1.012-1.056; P = .01; HR for 24-hour = 2.23). In contrast, the association between long-term AF burden and subsequent HF events was not statistically significant (HR, 1.009; 95% CI, 0.992-1.026; P = .373). A 24-hour increase in AF burden is associated with a more than two-fold increased risk of HF events over the subsequent week while the long-term AF burden is not significantly associated with HF events.

Preparation of hemp nanofibers from agricultural waste by mechanical defibrillation in water

Industrial hemp is a green economic plant for biogas and fuel. It is also used mainly in construction, paper, and textile industries. After harvested, the stubs of hemp are left as wastes. Therefore, the added value of this part is considered in this study. Mechanical defibrillation is an interesting method which does not require any harmful chemicals to be involved for size reduction. In this work, high-pressure homogenization by microfluidizer was carried out to defibrillate hemp fibers. Three investigating parameters, which were chemical pretreatment (delignification and hemicellulose removal), fiber concentration, and defibrillation time, were studied. It was found that chemical pretreatment enhanced capability of mechanical defibrillation in which nanofibrillated cellulose could be obtained shortly by microfluidizer (starting from only 15 min defibrillation to obtain 20–50 nm fiber diameters). Higher fiber concentration during defibrillation provided greater degree of polymerization and slightly higher thermal degradation temperature. Meanwhile, longer defibrillation time resulted in smaller and more uniformity of size of nanofibers and provided significant lower degree of polymerization and minor decrease in thermal degradation temperature. However, no significant change on crystallinity was observed. From the obtained results, 0.7% w/v of fiber concentration and 120 min defibrillation time using chemi-mechanical method provided the most uniformity of fiber size and the highest transparency of an aqueous suspension as well as its cast film.

The Relationship Between Level of Adherence to Automatic Wireless Remote Monitoring and Survival in Pacemaker and Defibrillator Patients

BackgroundRemote monitoring (RM) technology embedded within cardiac rhythm devices permits continuous monitoring, which may result in improved patient outcomes. ObjectivesThis study used “big data” to assess whether RM is associated with improved survival and whether this is influenced by the type of cardiac device and/or its degree of use. MethodsWe studied 269,471 consecutive U.S. patients implanted between 2008 and 2011 with pacemakers (PMs), implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) with pacing capability (CRT-P)/defibrillation capability (CRT-D) with wireless RM. We analyzed weekly use and all-cause survival for each device type by the percentage of time in RM (%TRM) stratified by age. Socioeconomic influences on %TRM were assessed using 8 census variables from 2012. ResultsThe group had implanted PMs (n = 115,076; 43%), ICDs (n = 85,014; 32%), CRT-D (n = 61,475; 23%), and CRT-P (n = 7,906; 3%). When considered together, 127,706 patients (47%) used RM, of whom 67,920 (53%) had ≥75%TRM (high %TRM) and 59,786 (47%) <75%TRM (low %TRM); 141,765 (53%) never used RM (RM None). RM use was not affected by age or sex, but demonstrated wide geographic and socioeconomic variability. Survival was better in high %TRM versus RM None (hazard ratio [HR]: 2.10; p < 0.001), in high %TRM versus low %TRM (HR: 1.32; p < 0.001), and also in low %TRM versus RM None (HR: 1.58; p < 0.001). The same relationship was observed when assessed by individual device type. ConclusionsRM is associated with improved survival, irrespective of device type (including PMs), but demonstrates a graded relationship with the level of adherence. The results support the increased application of RM to improve patient outcomes.

Association of BNP and Troponin Levels with Outcome among Cardiac Resynchronization Therapy Recipients.

We conducted a prospective multicenter study to assess the prognostic value of combined baseline preimplant plasma levels of the biomarkers cardiac troponin T (TnT) and B-type natriuretic peptide (BNP) among cardiac resynchronization therapy (CRT) with or without defibrillator capability (CRT-D) recipients. At CRT-D implant, patients were stratified based on detectable TnT (≥0.01 ng/mL) and elevated BNP (predefined as >440 pg/mL) levels. Patients were classified into three groups: high (both detectable TnT and high BNP), intermediate (either detectable TnT or high BNP), or low (nondetectable TnT and low BNP). Patients were followed for 12 months. Survival curves free from mortality or heart failure hospitalizations (HFH) were assessed. To assess the predictive value of biomarker category, we constructed a multivariate Cox regression model, including the covariates of age, New York Heart Association class, left ventricular ejection fraction (LVEF), and QRS duration. A total of 267 patients (age 66 ± 12 years, males 80%, LVEF 25% ± 8%, ischemic cardiomyopathy 52%, QRSd 155 ± 26 ms) were studied. After 1 year, there were 13 deaths and 25 HFH events. A significant difference in event-free survival among the three groups was observed, with high and intermediate categories having worse survival than low (log-rank test, P < 0.001). In the multivariate model, risk category was a significant predictor of outcome: hazard ratios were 7.34 (95% confidence interval [CI]: 2.48-21.69) and 2.50 (95% confidence interval [CI]: 1.04-6.04) for high-risk and intermediate-risk groups, respectively (P < 0.0001). Among CRT-D recipients, baseline TnT and BNP values alone or in combination provide significant prognostic value for the outcome of mortality or HFH.

Stratifying patients at the risk of heart failure hospitalization using existing device diagnostic thresholds

BackgroundHeart failure hospitalizations (HFHs) cost the US health care system ∼$20 billion annually. Identifying patients at risk of HFH to enable timely intervention and prevent expensive hospitalization remains a challenge. Implantable cardioverter defibrillators (ICDs) and cardiac resynchronization devices with defibrillation capability (CRT-Ds) collect a host of diagnostic parameters that change with HF status and collectively have the potential to signal an increasing risk of HFH. These device-collected diagnostic parameters include activity, day and night heart rate, atrial tachycardia/atrial fibrillation (AT/AF) burden, mean rate during AT/AF, percent CRT pacing, number of shocks, and intrathoracic impedance. There are thresholds for these parameters that when crossed trigger a notification, referred to as device observation, which gets noted on the device report. We investigated if these existing device observations can stratify patients at varying risk of HFH. MethodsWe analyzed data from 775 patients (age: 69 ± 11 year, 68% male) with CRT-D devices followed for 13 ± 5 months with adjudicated HFHs. HFH rate was computed for increasing number of device observations. Data were analyzed by both excluding and including intrathoracic impedance. HFH risk was assessed at the time of a device interrogation session, and all the data between previous and current follow-up sessions were used to determine the HFH risk for the next 30 days. Results2276 follow-up sessions in 775 patients were evaluated with 42 HFHs in 37 patients. Percentage of evaluations that were followed by an HFH within the next 30 days increased with increasing number of device observations. Patients with 3 or more device observations were at 42× HFH risk compared to patients with no device observation. Even after excluding intrathoracic impedance, the remaining device parameters effectively stratified patients at HFH risk. ConclusionAvailable device observations could provide an effective method to stratify patients at varying risk of heart failure hospitalization.

An ontology-based annotation of cardiac implantable electronic devices to detect therapy changes in a national registry.

The patient population benefitting from cardiac implantable electronic devices (CIEDs) is increasing. This study introduces a device annotation method that supports the consistent description of the functional attributes of cardiac devices and evaluates how this method can detect device changes from a CIED registry. We designed the Cardiac Device Ontology, an ontology of CIEDs and device functions. We annotated 146 cardiac devices with this ontology and used it to detect therapy changes with respect to atrioventricular pacing, cardiac resynchronization therapy, and defibrillation capability in a French national registry of patients with implants (STIDEFIX). We then analyzed a set of 6905 device replacements from the STIDEFIX registry. Ontology-based identification of therapy changes (upgraded, downgraded, or similar) was accurate (6905 cases) and performed better than straightforward analysis of the registry codes (F-measure 1.00 versus 0.75 to 0.97). This study demonstrates the feasibility and effectiveness of ontology-based functional annotation of devices in the cardiac domain. Such annotation allowed a better description and in-depth analysis of STIDEFIX. This method was useful for the automatic detection of therapy changes and may be reused for analyzing data from other device registries.

Cardiac resynchronization therapy

Consensus guidelines define indications for cardiac resynchronization therapy (CRT), but the variability in implant rates in 'real world' clinical practice, as well as the relationship with the epidemiology of heart failure are not defined. In Emilia-Romagna, an Italian region with around 4.4 million inhabitants, a registry was instituted to collect data on implanted devices for CRT, with (CRT-D) or without defibrillation (CRT-P) capabilities. Data from all consecutive patients resident in this region who underwent a first implant of a CRT device in years 2006-2010 were collected and standardized (considering each of the nine provinces of the region). The number of CRT implants increased progressively, with a 71% increase in 2010 compared to 2006. Between 84 and 90% of implants were with CRT-D devices. The variability in standardized implant rates among the provinces was substantial and the ratio between the provinces with the highest and the lowest implant rates was always greater than 2. Considering prevalent cases of heart failure in the period 2006-2010, the proportion of patients implanted with CRT per year ranged between 0.23 and 0.30%. The application in 'real world' clinical practice of CRT in heart failure is quite heterogeneous, with substantial variability even among areas belonging to the same region, with the need to make the access to this treatment more equitable. Despite the increased use of CRT, its overall rate of adoption is low, if a population of prevalent heart failure patients is selected on the basis of administrative data on hospitalizations.

Use of myocardial scar characterization to predict ventricular arrhythmia in cardiac resynchronization therapy

There is insufficient evidence to implant a combined cardiac resynchronization therapy (CRT) device with defibrillation capabilities (CRT-D) in all CRT candidates. The aim of the study was to assess myocardial scar size and its heterogeneity as predictors of sudden cardiac death (SCD) in CRT candidates. A cohort of 78 consecutive patients with dilated cardiomyopathy and class I indication for CRT-D were prospectively enrolled. Before CRT-D implantation, a contrast-enhanced cardiac magnetic resonance (ce-CMR) was performed. The core and border zone (BZ) of the myocardial scar were characterized and quantified with a customized post-processing software. The first appropriate implantable cardioverter defibrillator (ICD) therapy was considered as a surrogate of SCD. During a mean follow-up of 25 months (25-75th percentiles, 15-34), appropriate ICD therapy occurred in 11.5% of patients. In a multivariate Cox proportional hazards regression model for clinical and ce-CMR variables, the scar mass percentage [hazards ratio (HR) per 1% increase 1.1 (1.06-1.15), P < 0.01], the BZ mass [HR per 1 g increase 1.06 (1.04-1.09), P < 0.01], and the BZ percentage of the scar [HR per 1% increase 1.06 (1.02-1.11), P < 0.01], were the only independent predictors of appropriate ICD therapy. Receiver-operating characteristic curve analysis showed that a scar mass <16% and a BZ < 9.5 g had a negative predictive value of 100%. The presence, size, and heterogeneity of myocardial scar independently predict appropriate ICD therapies in CRT candidates. The ce-CMR-based scar analysis might help identify a subgroup of patients at relatively low risk of SCD.

Cardiac resynchronization therapy to prevent life-threatening arrhythmias in patients with congestive heart failure

Various clinical data demonstrate that cardiac resynchronization therapy (CRT) provides a favorable structural as well as electrical remodeling. The CArdiac Resynchronization–Heart Failure study, which tested the pure effect of CRT (using CRT devices without the capability of defibrillation) clearly showed a significant reduction in the total mortality by partly preventing sudden cardiac death. The antiarrhythmic effects of CRT are explained, at least in part, by ionic and genetic modulation of ventricular myocytes. It has been revealed in animal experiments to mimic disorganized ventricular contraction that CRT reverses down-regulation of certain K+ channels and abnormal Ca2+ homeostasis in the failing heart. However, CRT can be proarrhythmic in some particular cases especially in the early phase of this therapy. According to our study, proarrhythmic effects after CRT can be observed in approximately 10% of patients. The relatively high incidence of the proarrhythmic effects of CRT may promote a trend toward selecting CRT-D rather than CRT-P.

Indications for a Wearable Cardioverter-Defibrillator

The wearable cardioverter-defibrillator (WCD) is an alternative antiarrhythmic device that provides continuous cardiac monitoring and defibrillation capabilities through a noninvasive electrode-based system. Although the WCD has been shown to be highly effective at restoration of sinus rhythm in patients with a ventricular tachyarrhythmia, randomized trials using the WCD in patient populations at elevated risk for arrhythmic death have not been reported. Clinical indications for WCD use are varied and continue to evolve as further experience with this relatively new technology emerges.

Do implantable cardioverter defibrillators improve survival in patients with severe left ventricular systolic dysfunction after coronary artery bypass graft surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether implantable cardioverter defibrillators (ICD) improve survival in patients with severe left ventricular systolic dysfunction (LVSD) after coronary artery bypass graft (CABG) surgery. ICDs are designed to terminate potentially fatal cardiac tachyarrhythmias. A right ventricular lead is mandatory for detection, pacing and defibrillation capabilities. Dual chamber ICDs have an additional right atrial lead and are used for patients with conventional atrioventricular pacing indications. More sophisticated, biventricular devices exist to provide cardiac resynchronisation therapy (CRT) in addition to defibrillation (CRT-D). ICDs have been extensively investigated in patients with LVSD post myocardial infarction and in patients with non-ischaemic cardiomyopathy for both secondary prevention (history of ventricular arrhythmias) and primary prevention (deemed high risk for ventricular arrhythmias). This best evidence topic aims to review the evidence and its applicability to patients post CABG. Nine hundred and sixteen papers were identified using the search method outlined. Eight randomised controlled trials, two meta-analyses, and one non-randomised trial, in addition to international guidelines presented the best evidence to answer the clinical question. The current evidence base and guidelines suggest that ICDs should be considered for all patients with LVSD [ejection fraction (EF) ≤30-40%] receiving optimal pharmacological management, who are ≥40days post MI [four weeks for National Institute for Health and Clinical Excellence (NICE)] and in New York Heart Association (NYHA) class I-III. UK NICE guidelines require in addition; non-sustained ventricular tachycardia (NSVT) on a Holter monitor and inducible ventricular tachycardia at electrophysiological study for EF between 30 and 35%; or a QRS >120ms if EF <30%. The North American guidelines recommend EF <30% as a threshold for those with NYHA class I symptoms. The evidence is applicable to patients post CABG, provided all the other criteria are met. European Society of Cardiology (ESC) guidelines recommend waiting at least three months (consensus opinion) after revascularisation prior to assessment for an ICD, to allow time for potential recovery of ventricular function.

Survival of Patients With Implantable Cardioverter Defibrillators in the Era of Remote-Monitoring: The 5000-Foot, High-Altitude View

Large randomized trials have demonstrated unequivocally that implantable cardioverter defibrillators (ICDs) improve outcome for individuals with defined clinical characteristics known to be associated with a high risk of ventricular arrhythmias. However, less is known about outcomes of patients receiving ICDs in the “real world.” The National Cardiovascular Data Registry provides extensive and detailed clinical information about patients receiving ICDs at the time of implant, but does not include longitudinal data on mortality or shocks except in a small subset.1 Industry databases of ICD patients undergoing remote (transtelephonic) monitoring, which provide extensive information on therapies received, thus present a unique opportunity to fill this gap in knowledge. Article see p 2359 In this issue of Circulation , Saxon et al2 describe data on 69 556 patients followed remotely (in addition to in-office) and 124 450 patients followed in-office alone, which was generated by the Altitude project, a prospectively designed database generated by a single ICD manufacturer to store data regarding patients receiving its devices. Survival data are obtained through cross-referencing with the Social Security death index, and data on treated arrhythmias are obtained from the transtelephonic transmissions. The authors use this database to answer four distinct questions: (1) whether remote monitoring impacts survival; (2) whether shocks are associated with mortality; (3) how survival compares among patients receiving ICDs, ICDs with cardiac resynchronization (CRT) capability (CRT-D), and CRT devices without defibrillation capability; and (4) how survival of “real-world” patients compares with that of patients enrolled in trials. The study is limited by lack of detailed information about the patients' …

Is cardiac resynchronization therapy cost-effective?

Cardiac resynchronization therapy (CRT) is a treatment of proven efficacy for selected patients with heart failure and associated conduction disturbances. The increasing financial burden that healthcare systems face has increased the interest in cost-effectiveness and cost-utility estimates, focused on devices with defibrillation capabilities (CRT-D), with a high upfront cost, as well as on simpler devices providing only biventricular pacing (CRT-P). Available economic estimates are largely dependent on data source, assumptions, modelling technique, time horizon, and perspective, leading to some variability in cost-effectiveness and cost-utility estimates. As a whole, cost-effectiveness and cost-utility estimates of both CRT-P and CRT-D improve as the time horizon examined is lengthened and appear to be below US$50,000 per quality-adjusted life-year, a threshold value commonly adopted for coverage of healthcare interventions in the USA and quite comparable with similar thresholds used within Europe. Limited data are available on the comparative cost-effectiveness or cost-utility of CRT-P and CRT-D devices. Moreover, more data on the effectiveness and long-term benefits of CRT-D and CRT-P are needed in order to estimate better the value of these treatments in the 'real world, as well as for attempts to improve cost-effectiveness through improved patient selection.