Standard Implantable Cardioverter-defibrillator Research Articles

Additional coils mitigate elevated defibrillation threshold in right-sided implantable cardioverter defibrillator generator placement: a simulation study.

The standard implantable cardioverter defibrillator (ICD) generator (can) is placed in the left pectoral area; however, in certain circumstances, right-sided cans may be required which may increase defibrillation threshold (DFT) due to suboptimal shock vectors. We aim to quantitatively assess whether the potential increase in DFT of right-sided can configurations may be mitigated by alternate positioning of the right ventricular (RV) shocking coil or adding coils in the superior vena cava (SVC) and coronary sinus (CS). A cohort of CT-derived torso models was used to assess DFT of ICD configurations with right-sided cans and alternate positioning of RV shock coils. Efficacy changes with additional coils in the SVC and CS were evaluated. A right-sided can with an apical RV shock coil significantly increased DFT compared to a left-sided can [19.5 (16.4, 27.1) J vs. 13.3 (11.7, 19.9) J, P < 0.001]. Septal positioning of the RV coil led to a further DFT increase when using a right-sided can [26.7 (18.1, 36.1) J vs. 19.5 (16.4, 27.1) J, P < 0.001], but not a left-sided can [12.1 (8.1, 17.6) J vs. 13.3 (11.7, 19.9) J, P = 0.099). Defibrillation threshold of a right-sided can with apical or septal coil was reduced the most by adding both SVC and CS coils [19.5 (16.4, 27.1) J vs. 6.6 (3.9, 9.9) J, P < 0.001, and 26.7 (18.1, 36.1) J vs. 12.1 (5.7, 13.5) J, P < 0.001]. Right-sided, compared to left-sided, can positioning results in a 50% increase in DFT. For right-sided cans, apical shock coil positioning produces a lower DFT than septal positions. Elevated right-sided can DFTs may be mitigated by utilizing additional coils in SVC and CS.

QRS duration as an independent risk factor for appropriate shocks and mortality in patients with prophylactic implantable cardioverter-defibrillator

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Community’s 7th Framework Programme FP7/2007-2013 Background The implantable cardioverter defibrillator (ICD) is an established therapy for the prevention of sudden cardiac death (SCD) in high-risk heart failure patients. However, improvements in risk stratification are necessary to increase the efficiency of ICD use. We performed an analysis of the retrospective EU-CERT-ICD registry with respect to QRS duration and effects of cardiac resynchronisation therapy (CRT) on outcomes. Methods/Results A total of 5033 patients (81% males) from 14 European centres had an ICD implanted for primary prophylaxis. Mean age at the time of ICD implantation was 64±11 years and ischemic cardiomyopathy was the underlying pathology in 65% of patients. CRT was used in 43% of the patients. The median follow-up was 2.7 years (IQR 1.4-4.6 years). Predefined primary endpoints were all-cause mortality, first appropriate and first inappropriate shocks. The effect of covariates on the cumulative primary endpoints were assessed through hazard ratios in the Fine and Gray subdistributional hazard models (accounting for the competing risks) stratified by centres. Because of resynchronization by the device, the analysis considered a different influence of QRS on outcomes in the CRT-D and the ICD groups. We observed an increase in the cumulative incidence of the first appropriate shock with increasing QRS values for patients implanted with only an ICD (HR 1.12 per 10ms increase, p&amp;lt;0.001). In patients with CRT-D, increasing QRS values related to a (statistically non-significant) decrease in the cumulative incidence of the first appropriate shocks (HR 0.96 per 10ms, p=0.299). Since a wide QRS is an indication for CRT-D therapy, high QRS values cluster among those patients with implanted CRT-D, while among patients with QRS under 130ms standard ICD implantations are more frequent. This can explain the observed increase in the cumulative incidence of the first appropriate shocks for increasing QRS values up to 130ms in the ICD-group and its decrease for increasing QRS values over 130ms in the CRT-D group. Regarding all-cause mortality, hazard ratios for age, LVEF, NYHA, ICM, AF, diabetes and sex category agreed with the results obtained in previously published meta-analyses. Increased QRS values are associated with higher mortality in the ICD group (HR 1.09 per 10ms increase, p&amp;lt;0.001), but not in the CRT-D group (HR 0.99 per 10ms increase, p=0.695). Conclusion In our study, we confirmed QRS duration as an independent risk factor for appropriate ICD shocks and all-cause mortality in patients with ICD for primary prophylaxis. However, this was only observed in patients with single- or dual-chamber ICD, while there was no correlation in CRT-D patients. The findings suggest that CRT-D exerts a protective effect regarding the occurrence of first appropriate shock and all-cause mortality for patients with QRS values higher than 130 ms and indication for resynchronization.

Delayed detection programming significantly reduces inappropriate ICD therapies in patients with left-ventricular assist devices

Abstract Funding Acknowledgements Type of funding sources: None. Background Implantation of a left ventricular assist device (LVAD) is an established therapy for end-stage heart failure, either as bridge to transplantation or as destination therapy. Virtually all LVAD patients carry an implantable cardioverter-defibrillator (ICD) for primary or secondary prevention. The risk of ventricular tachyarrhythmias is significant in LVAD patients, but so is the burden of supraventricular tachycardia and the ensuing risk of inappropriate ICD therapies. The present retrospective study sought to quantify the impact of standard ICD programming vs. a ICD programming with long detection delays on the occurrence of inappropriate ICD therapies. Methods and results We retrospectively identified 337 consecutive patients (292 male, mean age 54.2 ± 12.3 years) who received a continuous-flow LVAD at our institution. Median follow-up duration was 2.3 (IQR 1.3, 3.7) years. Heart failure etiology was ischemic cardiomyopathy in 155 patients (46.0 %) and non-ischemic dilated cardiomyopathy in 150 (44.5 %). Other etiologies accounted for 32 patients (9.4 %). ICDs implanted at the time of LVAD implantation were single chamber devices in 176 patients (52.2 %), dual chamber devices in 45 patients (13.4 %), and CRT-D in 116 patients (34.4 %) A total of 2228 ICD-treated arrhythmia episodes occurred in 153 patients. 2066 (92.6 %) episodes were appropriate interventions for ventricular arrhythmias. 162 (7.3 %) treatments were inappropriate due to supraventricular tachyarrhythmias (n=115; 71.4 %), sinus tachycardia (n=15; 9.3 %) or oversensing (n=21; 12.9%). We retrospectively compared a standard programming (number of intervals for detection [NID] in the slowest therapy zone ≤ 40) and a long delay programming (NID &amp;gt; 40) and investigated the time to the first inappropriate therapy. A total of 285 patients were programmed to NID ≤ 40 at the first ICD interrogation after LVAD implant, 47 were programmed to NID &amp;gt; 40. Therapies were inactive in the remaining 5 patients. Median NID was 30 (IQR 23, 35) in the standard programming group and 60 (IQR 50, 76) in the long delay group, with similar rates for detection (median cycle lengths 340 [IQR 330, 350] ms and 330 [IQR 322, 340] ms for standard and long delay, respectively). Long delay programming was associated with significantly higher freedom from inappropriate therapies during follow-up (Hazard ratio 0.14, p [log rank] 0.027). No significant difference was observed between groups with regard to time to first appropriate therapy. Conclusion A number of intervals for detection greater than 40 in the slowest therapy zone was associated with a significantly increased freedom from inappropriate therapies in this large retrospective single-center cohort of LVAD patients with an ICD and should be considered as the default ICD programming strategy in this population.

Use and outcomes of subcutaneous implantable cardioverter-defibrillator (ICD) after transvenous ICD extraction: An analysis of current clinical practice and a comparison with transvenous ICD reimplantation

The subcutaneous implantable cardioverter-defibrillator (S-ICD) does not require the insertion of any leads into the cardiovascular system. The aims of the study were to describe current practice and to measure outcomes associated with S-ICD or standard single-chamber transvenous ICD (TV-ICD) use after TV-ICD explantation. We analyzed all consecutive patients who underwent transvenous extraction of an ICD and subsequent implantation of an S-ICD or a single-chamber TV-ICD at 12 Italian centers from 2011 to2017. A total of 229 patients were extracted and subsequently reimplanted with an S-ICD (90; 39%) or a single-chamber TV-ICD (139; 61%). S-ICD implantation increased from 9% in 2011 to 85% in 2017 (P< .001). Patients reimplanted with an S-ICD were younger (53 ± 13 years vs 60 ± 18 years; P = .011) and more frequently had undergone extraction owing to infection (73% vs 52%; P<.001). The rates of complications at follow-up were comparable between groups (hazard ratio 0.97; 95% confidence interval 0.49-1.92; P = .940). No lead failures, systemic infections, or system-related deaths occurred in the S-ICD group. In the TV-ICD group, 1 lead fracture occurred and 2 systemic infections were reported, resulting in death in 1 case. In the S-ICD group, the rate of complications was lower when the generator was positioned in a sub- or intermuscular pocket (hazard ratio 0.21; 95% confidence interval 0.05-0.87; P = .048). Our results show an increasing use of S-ICD over the years in patients undergoing TV-ICD explantation. An S-ICD is preferably adopted in young patients, mostly in the case of infection. The complication rate was comparable between groups and decreased when a sub- or intermuscular S-ICD generator position was adopted.

Prospective Randomized Evaluation of Implantable Cardioverter‐Defibrillator Programming in Patients With a Left Ventricular Assist Device

BackgroundVentricular arrhythmias are common in patients with left ventricular assist devices (LVADs) but are often hemodynamically tolerated. Optimal implantable cardioverter defibrillator (ICD) tachy‐programming strategies in patients with LVAD have not been determined. We sought to determine if an ultra‐conservative ICD programming strategy in patients with LVAD affects ICD shocks.Methods and ResultsAdult patients with an existing ICD undergoing continuous flow LVAD implantation were randomized to standard ICD programming by their treating physician or an ultra‐conservative ICD programming strategy utilizing maximal allowable intervals to detection in the ventricular fibrillation and ventricular tachycardia zones with use of ATP. Patients with cardiac resynchronization therapy (CRT) devices were also randomized to CRT ON or OFF. Patients were followed a minimum of 6 months. The primary outcome was time to first ICD shock. Among the 83 patients studied, we found no statistically significant difference in time to first ICD shock or total ICD shocks between groups. In the ultra‐conservative group 16% of patients experienced at least one shock compared with 21% in the control group (P=0.66). There was no difference in mortality, arrhythmic hospitalization, or hospitalization for heart failure. In the 41 patients with CRT ICDs fewer shocks were observed with CRT‐ON but this was not statistically significant: 10% of patients with CRT‐ON (n=21) versus 38% with CRT‐OFF (n=20) received shocks (P=0.08).ConclusionsAn ultra‐conservative programming strategy did not reduce ICD shocks. Programming restrictions on ventricular tachycardia and ventricular fibrillation zone therapy should be reconsidered for the LVAD population. The role of CRT in patients with LVAD warrants further investigation.Clinical Trial RegistrationURL: https://www.clinicaltrials.gov. Unique identifier: NCT01977703.

Implantable Cardioverter-Defibrillators With Versus Without Resynchronization Therapy in Patients With a QRS Duration >180 ms

BackgroundMore than 20% of Medicare beneficiaries receiving cardiac resynchronization therapy defibrillators (CRT-D) have a very wide (≥180 ms) QRS complex duration (QRSD). Outcomes of CRT-D in these patients are not well-established because they have been underrepresented in clinical trials. ObjectivesThis study examined outcomes in patients with CRT-D in a very wide QRSD with left bundle branch block (LBBB) versus those without LBBB. MethodsMedicare patients from the Implantable Cardioverter Defibrillator Registry (January 1, 2005, through April 30, 2006) with a CRT-D and confirmed Class I or IIa indications for CRT-D were matched to implantable cardioverter-defibrillator (ICD) patients without CRT despite having Class I or IIa indications for CRT. Mortality and heart failure hospitalizations over 4 years with CRT-D versus standard ICDs based on QRSD and morphology were analyzed. ResultsWe analyzed 24,960 patients. Among those with LBBB, patients with a QRSD ≥180 ms had a greater adjusted survival benefit with CRT-D versus standard ICD (hazard ration [HR] for death: 0.65; 95% confidence interval [CI]: 0.59 to 0.72) compared with those having a QRSD 120 to 149 ms (HR: 0.85; 95% CI: 0.80 to 0.92) and 150 to 179 ms (HR: 0.87; 95% CI: 0.81 to 0.93). CRT-D versus ICD was associated with an improvement in survival in those with non-LBBB and a QRSD ≥180 ms (adjusted HR for death: 0.78; 95% CI: 0.68 to 0.91), but not in those with non-LBBB and a QRSD 150 to 179 ms (adjusted HR for death: 1.06; 95% CI: 0.95 to 1.19). ConclusionsImprovements in both survival and heart failure hospitalizations with CRT-D were greatest in patients with a QRSD ≥180 ms with or without LBBB, whereas patients with a QRSD 150 to 179 ms without LBBB had no improvement in survival with CRT-D, and those with a QRSD 150 to 179 ms and LBBB had only a modest improvement.

The subcutaneous implantable cardioverter defibrillator: state-of-the-art review.

The subcutaneous implantable cardioverter defibrillator (ICD) provides therapy for the prevention of sudden cardiac death while avoiding the numerous complications associated with transvenous leads. This relatively novel device employs an innovative approach to sensing and defibrillation from outside of the thoracic cage. Substantial data from cohort studies and registries have accrued and can be used to inform patient eligibility, implant technique, and efficacy compared with the standard transvenous ICD. This review serves to update the clinician as to current evidence and the nuances involved in the optimal utilization of this innovative technology.

Abstract 117: Application Of A Delphi Method To Develop A Patient Decision Aid For Implantable Cardioverter Defibrillator Candidates

Background: Development of patient decision aids (PtDA) requires decision making about the facts, risks, and benefits to present to patients. Delphi process methodology has been employed successfully as a consensus-building tool across several disciplines. This work represents the first phase of a Canadian study that is developing a PtDA for prophylactic implantable cardioverter defibrillator (ICD) candidates. Our aim was to engage healthcare providers, ICD stakeholders, and patients in decisions about the content and format of the PtDA, using a modified Delphi process. Method: Twenty healthcare professionals, 1 stakeholder representative, and 16 people living with ICDs were invited to participate. Our Delphi approach utilized electronic and paper based response systems that included 1) anonymity, 2) iteration, 3) controlled feedback and, 4) statistical group response options. The first Delphi round comprised 39 evidence-based survey items including ICD facts, risks, benefits, and values. A review panel of decision aid experts, cardiovascular researchers, and electrophysiologists selected the content items. Participants completed the survey by rating each category item on a 5-point likert scale from “1= not important” to “5 = extremely important”. A predetermined cut-off of &gt; 75%, wherein participants rated an item as “very important” or higher, guided the selection of items during the two Delphi rounds completed. To provide participants with statistical group responses, the second round participants received the anonymous first round item rankings prior to rating the 11 remaining items. Results: Twenty-seven participants completed round one of the Delphi (14 ICD patients). Mean (SD) age of ICD patients was 66.8 (7.1) years. The number of years of experience in healthcare reported by non-ICD respondents ranged from 2 to30 years. Of the 39 items included in round one, 14 items were retained ( &gt; 75% agreement), 14 items were removed (&lt;60% agreement), and 11 items proceeded to the second round (60-74% agreement). During the second Delphi round (n=27), 6 of the 11 items that did not reach agreement in round one were retained ( &gt; 75% agreement). Examples from item categories include: 1) Risk items - i ) Lead problems over the long term, ii ) Possible complications during the surgical procedure to insert the ICD. 2) Benefit items- i ) Prevent cardiac arrest from a dangerous heart rhythm, ii ) Assurance that a dangerous heart rhythm can be corrected. 3) Fact, Value &amp; Preferences - i ) What a standard ICD cannot do, ii ) The wish for a natural death, iii ) Driving restrictions if the ICD delivers a shock. Conclusion: The results from this Delphi survey informed the content that will be incorporated into a PtDA for new ICD candidates. The next phase will include field-testing of the PtDA. Ultimately, the goal is to support quality decision making in ICD candidates.

VT begets VT—and other bad stuff—in patients treated with CRT-D

Clinical trials have helped clarify the role of cardiac resynchronization therapy (CRT) in patients with heart failure. Early trials demonstrated reduction in mortality and heart failure hospitalization in patients with electrical dyssynchrony and moderate to severe functional impairment, and more recent trials showed that these benefits extend to heart failure patients even with mild symptoms. Most patients with a class 1 or 2 indication for CRT also have an appropriate indication for an implantable cardioverterdefibrillator (ICD) on the basis of the presence of ischemic or nonischemic cardiomyopathy, so the vast majority of CRT is delivered via a CRT with defibrillator (CRT-D). In fact, the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) study randomized 1820 patients with cardiomyopathy of any etiology with left ventricular ejection fraction ≤30%, QRS duration ≥130 ms, and mild heart failure (New York Heart Association class I or II) to either standard ICD or CRT-D, and it showed that CRT-D leads to improved outcome compared with ICD alone in this population. The MADIT-CRT study design has enabled the investigators to also examine the effect of CRT on ventricular arrhythmic events. In a recent report, this group showed that CRT-D was associated with a 29% reduction in the risk of a first episode of ventricular tachyarrhythmic events compared with ICD alone. Importantly, this arrhythmia risk reduction was not homogeneous across the entire study population. Among patients with left bundle branch block (LBBB), CRT-D conferred a 42% reduction in the risk of first arrhythmic event compared with standard ICD, but in nonLBBB patients, CRT-D provided no such advantage, a finding that mirrors the general lack of clinical response to CRT seen in non-LBBB patients. Conversely, one might wonder what effect arrhythmic events have on subsequent outcome in CRT-D treated patients compared with that in standard ICD recipients. In this issue of HeartRhythm, Kutyifa et al addresses this very question, once again taking the advantage of the rich database provided by the MADIT-CRT trial. These investigators sought to evaluate the prognostic value of ventricular tachyarrhythmias, categorized as slow ventricular tachycardia

Clinical Experience and Procedural Outcomes Associated with the DF4 Implantable Cardioverter Defibrillator System: The SJ4 Postapproval Study

Current implantable cardioverter defibrillators (ICDs) employ two or three low- and high-voltage lead connectors, adding complexity and bulk, sometimes resulting in incorrect connections and adverse events. The SJ4 study evaluates the performance of a novel integrated single-lead DF4 connection system by characterizing lead measurements, handling characteristics, and outcomes. Patients with standard guidelines-based ICD indications were enrolled and implanted with a St. Jude Medical™ DF4 system (St. Jude Medical, Sylmar, CA, USA; right ventricular high-voltage DF4 lead models 7120Q, 7121Q, 7122Q, or 7170Q with compatible ICD). Device electrical measurements, handling characteristics, and any adverse events were collected at implant and during each scheduled 6-month follow-up. Among 1,701 patients (65 ± 13 years, 72% male, left ventricular ejection fraction 29 ± 12%) enrolled at 58 centers, there were 1,697 successful implants (99.8% implant success; ICD; n = 999, cardiac resynchronization therapy-defibrillator n = 698). Implanting physicians reported that implantation of the DF4 lead was normal or easier than normal in 94% of cases with successful implant. These patients have been followed for 1.7 ± 0.5 years with a maximum follow-up of 2.5 years. The complication rate was 0.017 per patient year of follow-up (95% confidence interval: 0.013-0.023), which included abnormal defibrillation impedance, elevated pacing thresholds, failure to detect ventricular tachycardia/ventricular fibrillation, lead dislodgement, lead fracture, loss of capture, and lead perforation. There were no set screw-related complications at implant or during follow-up. The DF4 system overall performed very well with few complications at implant and in follow-up.

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Prevalence and Presentation of Externalized Conductors and Electrical Abnormalities in Riata Defibrillator Leads After Fluoroscopic Screening

Background— The Riata family of implantable cardioverter-defibrillator (ICD) leads is prone to a specific insulation abrasion characterized by externalization of conductor cables. The objective of this study was to determine the prevalence of externalized conductors and electrical abnormalities in Riata ICD leads by fluoroscopic screening and standard ICD interrogation. Methods and Results— All ICD implantation centers were contacted by the Netherlands Heart Rhythm Association Device Advisory Committee to identify all patients with an active Riata ICD lead and to perform fluoroscopic screening of the lead. In addition, the electrical integrity of the lead was assessed. As of March 1, 2012, data for 1029 active Riata leads were available; 47% of these were 8-F Riata and 53% were 7-F Riata ST. Externalized conductors were observed in 147 leads (14.3%). Proportion of externalized conductors was higher in 8-F Riata compared with 7-F Riata ST (21.4% vs 8.0%; P &lt;0.001). Median time from implantation to detection of externalized conductors was 65.3 months. The estimated rates of externalized conductors were 6.9% and 36.6% at 5 and 8 years after implantation, respectively. Of the 147 leads with externalized conductors, 10.9% had abnormal electrical parameters vs 3.5% in nonexternalized leads ( P &lt;0.001). Conclusions— The prevalence of externalized conductors in Riata leads is significantly high (14.3%) using fluoroscopic screening. The majority of externalized conductors are not detectable with standard ICD interrogation. Screening with fluoroscopy is reasonable.

Cardiac Resynchronization Therapy in Patients With Permanent Atrial Fibrillation

Background— Cardiac resynchronization (CRT) prolongs survival in patients with systolic heart failure and QRS prolongation. However, most trials excluded patients with permanent atrial fibrillation. Methods and Results— The Resynchronization for Ambulatory Heart Failure Trial (RAFT) randomized patients to an implantable cardioverter defibrillator (ICD) or ICD+CRT, stratified by the presence of permanent atrial fibrillation. Patients with permanent atrial fibrillation were randomized to CRT-ICD (n=114) or ICD (n=115). Patients receiving a CRT-ICD were similar to those receiving an ICD: age (71.6±7.3 versus 70.4±7.7 years), left ventricular ejection fraction (22.9±5.3% versus 22.3±5.1%), and QRS duration (151.0±23.6 versus 153.4±24.7 ms). There was no difference in the primary outcome of death or heart failure hospitalization between those assigned to CRT-ICD versus ICD (hazard ratio, 0.96; 95% CI, 0.65–1.41; P =0.82). Cardiovascular death was similar between treatment arms (hazard ratio, 0.97; 95% CI, 0.55–1.71; P =0.91); however, there was a trend for fewer heart failure hospitalizations with CRT-ICD (hazard ratio, 0.58; 95% CI, 0.38–1.01; P =0.052). The change in 6-minute hall walk duration between baseline and 12 months was not different between treatment arms (CRT-ICD: 19±84 m versus ICD: 16±76 m; P =0.88). Patients treated with CRT-ICD showed a trend for a greater improvement in Minnesota Living with Heart Failure score between baseline and 6 months (CRT-ICD: 41±21 to 31±21; ICD: 33±20 to 28±20; P =0.057). Conclusions— Patients with permanent atrial fibrillation who are otherwise CRT candidates appear to gain minimal benefit from CRT-ICD compared with a standard ICD. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00251251.

Implant and Long‐Term Evaluation of Atrial Signal Amplification in a Single‐Lead ICD

In patients without clinical indications for pacing the use of a single-lead implantable cardioverter defibrillator (ICD) implementing atrial sensing capability with proper signal amplification management may represent a useful therapeutic option, combining the positive features of both single and dual-chamber devices. The aim of the study was to evaluate the atrial signal amplification and its long-term stability in a single-lead ICD system adding atrial sensing to a standard single-chamber ICD. P-wave amplitudes were collected and compared at implant both with a conventional external device ("unfiltered" P wave) and telemetrically with the implanted ICD ("filtered" P wave). Filtered/unfiltered P-wave ratio (amplification factor, AmF) was evaluated at implant and during follow-up. In 43 enrolled patients (38 men, age 64 ± 16 years), the mean filtered P wave at implant was significantly higher than the unfiltered P wave (3.85 ± 0.81 mV vs 2.0 ± 1.49 mV; P < 10(-11) ), with a mean AmF value of 2.77 ± 1.62. In seven patients with atrial fibrillation at implant, the AmF was higher (4.62 ± 1.94) than in patients in sinus rhythm (2.41 ± 1.30; P < 0.001). A significant linear correlation was found between the inverse of P wave and the AmF (R = 0.82, P < 0.00001). In 25 patients followed for 384 ± 244 days, atrial undersensing was never documented and AmF did not change from implant (3.19 ± 1.82; P = 0.24), also in different body position and breathing conditions. The single-lead ICD system evaluated reliably amplified P-wave amplitudes by a factor of about three, maintaining this performance during the observed follow-up.

Contemporary and future trends in cardiac resynchronization therapy to enhance response

The rationale for cardiac resynchronization therapy (CRT), expectations in terms of patient benefit, patient selection for CRT, selection of a CRT pacemaker (CRT-P) vs CRT plus implantable cardioverter-defibrillator (CRT-D) platform, and studies evaluating device programming to enhance benefit from CRT are reviewed. The notion of an "optimal" left ventricular (LV) pacing site, the rationale for identifying and avoiding LV pacing in regions of scar, the use of anatomic, hemodynamic, and electrical parameters to identify an optimal LV pacing site, and the potential utility of multisite LV pacing to enhance benefit from CRT are discussed. Finally, the advantages and disadvantages of the various methods for LV lead delivery are reviewed.

Prospective comparison of discrimination algorithms to prevent inappropriate ICD therapy: Primary results of the Rhythm ID Going Head to Head Trial

Inappropriate therapy for supraventricular arrhythmias remains a significant source of morbidity in implantable cardioverter-defibrillator (ICD) recipients. The Rhythm ID Goes Head to Head Trial (RIGHT) was designed to compare rhythm discrimination and inappropriate therapies among patients with ICDs from 2 manufacturers. Patients with standard ICD indications were randomized to receive a Guidant VITALITY 2 with Rhythm ID or selective Medtronic pulse generators using the Enhanced PR Logic or Wavelet discrimination algorithms. A single- or dual-chamber device was implanted based on clinical indications and programmed in 2 detection zones with detection enhancements enabled for rates between 150 and 200 bpm. Algorithm performance was compared between randomization groups, stratified by single or dual chamber, for the primary end point of first inappropriate therapy (shock or antitachycardia pacing) for supraventricular arrhythmias. There were 1962 patients enrolled and followed for 18.3 ± 9.2 months, with no difference in all-cause mortality between groups. There were 3973 treated episodes where electrograms were available and adjudicated. The primary end point of inappropriate therapy occurred in 246 of 985 VITALITY 2 patients vs 187 of 977 specific Medtronic ICD patients (hazard ratio = 1.34; confidence interval = 1.11-1.62; P = .003). Differences in inappropriate therapy were confined to single-chamber ICDs. Inappropriate shocks were more frequent in VITALITY 2 ICDs (hazard ratio = 1.63; confidence interval = 1.29-2.06; P < .001), with most therapies and performance differences occurring at slower rhythms (rates < 175 bpm). Rhythm discrimination performed better in the specific Medtronic than in VITALITY 2 ICDs evaluated, particularly for single-chamber devices. Inappropriate therapies, and differences in performance, may be reduced with the use of rate cutoff above 175 bpm.

Comparison of a Novel, Single-Lead Atrial Sensing System With a Dual-Chamber Implantable Cardioverter-Defibrillator System in Patients Without Antibradycardia Pacing Indications

Background— Supraventricular tachyarrhythmias are the main cause for inappropriate therapy by implantable cardioverter-defibrillators (ICDs). For better rhythm discrimination, an atrial electrogram is helpful and usually obtained from an additional atrial lead, even in the absence of sinus node or atrioventricular nodal disease. An A+-ICD system with integrated atrial sensing rings mounted 15 to 18 cm from the tip of an ICD lead may obviate the need to implant a separate atrial lead. The aim of the study was to compare the novel A+-ICD and a conventional dual-chamber (DR)-ICD. Methods and Results— Two hundred forty-nine patients with standard ICD indications but no requirement for antibradycardia pacing were randomized to receive an A+-ICD (n=124) or a DR-ICD (n=125). Implantation details, need for ICD system revision, long-term sensing, documented arrhythmia episodes, and the respective rhythm discrimination during follow-up were analyzed. The implantation time was significantly shorter in the A+-ICD group (67±30 vs 79±30 minutes, P =0.003). Mean P-wave amplitudes were 3.5±0.8 mV (A+-ICD) and 3.2±0.6 mV (DR-ICD) and remained stable during the follow-up period of 12 months. Surgical revision was necessary in 13 patients in the DR-ICD and 10 in the A+-ICD group. All 593 ventricular tachyarrhythmia episodes were correctly discriminated. Sensitivity and specificity of supraventricular tachyarrhythmia discrimination were not different between the study groups. Conclusions— The novel A+-ICD system can be implanted faster and is equivalent to a standard DR-ICD with regard to the detection of ventricular tachyarrhythmias and supraventricular tachyarrhythmias. It represents a useful alternative to obtain atrial sensing. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00324662.

Improvements in 25 Years of Implantable Cardioverter Defibrillator Therapy

In 1980, Dr. Michel Mirowski and his team inserted the first implantable cardioverter defibrillator (ICD) in a patient. Initially, ICD therapy was not widely accepted, and many physicians actually considered this therapy unethical. Large secondary and primary prevention trials, demonstrating a beneficial effect of ICD therapy in selected patients not only on arrhythmic death but also on all-cause mortality, stimulated a rapid growth in the number of implants and increased patient’s and physician’s acceptance. Improvements in size and weight, arrhythmia discrimination capabilities, battery technology, shock waveform and output, monitoring capabilities and defibrillator electrode technology eventually resulted in the current large number of yearly implants. Today, almost 40 years after the conception of the ICD and 25 years after the first human implant, ICD therapy is the treatment of choice for patients at risk for life-threatening arrhythmias either as secondary or primary prevention. Furthermore, with the more recent addition of resynchronisation therapy to standard ICD therapy, it became possible to treat selected patients with advanced symptoms of heart failure and to lower the risk of sudden death.

Bundle-Branch Block Morphology and Other Predictors of Outcome After Cardiac Resynchronization Therapy in Medicare Patients

Clinical trials of cardiac resynchronization therapy (CRT) have enrolled a select group of patients, with few patients in subgroups such as right bundle-branch block (RBBB). Analysis of population-based outcomes provides a method to identify real-world predictors of CRT outcomes. Medicare Implantable Cardioverter-Defibrillator Registry (2005 to 2006) data were merged with patient outcomes data. Cox proportional-hazards models assessed death and death/heart failure hospitalization outcomes in patients with CRT and an implantable cardioverter-defibrillator (CRT-D). The 14 946 registry patients with CRT-D (median follow-up, 40 months) had 1-year, 3-year, and overall mortality rates of 12%, 32%, and 37%, respectively. New York Heart Association class IV heart failure status (1-year hazard ratio [HR], 2.23; 3-year HR, 1.98; P<0.001) and age ≥ 80 years (1-year HR, 1.74; 3-year HR, 1.75; P<0.001) were associated with increased mortality both early and late after CRT-D. RBBB (1-year HR, 1.44; 3-year HR, 1.37; P<0.001) and ischemic cardiomyopathy (1-year HR, 1.39; 3-year HR, 1.44; P<0.001) were the next strongest adjusted predictors of both early and late mortality. RBBB and ischemic cardiomyopathy together had twice the adjusted hazard for death (HR, 1.99; P<0.001) as left BBB and nonischemic cardiomyopathy. QRS duration of at least 150 ms predicted more favorable outcomes in left BBB but had no impact in RBBB. A secondary analysis showed lower hazards for CRT-D compared with standard implantable cardioverter-defibrillators in left BBB compared with RBBB. In Medicare patients, RBBB, ischemic cardiomyopathy, New York Heart Association class IV status, and advanced age were powerful adjusted predictors of poor outcome after CRT-D. Real-world mortality rates 3 to 4 years after CRT-D appear higher than previously recognized.