Paced or sensed conduction time to determine programming with cardiac resynchronization therapy: The PASED-CRT Trial.

BACKGROUND: Cardiac resynchronization therapy (CRT) is a well-established treatment for patients with drug refractory heart failure. OBJECTIVES: This study sought to compare the longest RVsense to LVsense activation time (sLAT) versus the longest RVpace to LVsense activation time (pLAT) as the programmed site for left ventricular (LV) pacing in CRT patients with quadripolar LV leads at 3 months. METHODS: This single site, double-blinded, prospective trial, randomized patients 1:1 into the sLAT or pLAT group to determine response. LV pacing was programmed at implant and maintained through 3 months of follow-up. The 6-minute hall walk (6MHW) test, NYHA, Minnesota living with heart failure, and clinical composite score (CCS) at the 3 months was compared. RESULTS: N = 92 patients (73M:19F age 66 ± 11.3 years) were randomized implanted and programmed per protocol. Baseline characteristics were comparable. N = 39 sLAT and N = 34 pLAT completed the 3-month visit for final analysis. Significant improvement from baseline to 3 months was seen in the sLAT group from 253.9 (+/-11.5) to 323.1 (+/-11.9) P = .001. Similarly, the pLAT group improved from 274.9 (+/-16.15) to 343.9 (+/-15.9) P = .003. The difference between these groups, however, did not reach significance (P = .86). The pLAT group demonstrated a higher responder rate of (71%) versus the sLAT group (64%) based on the CCS although not reaching significance (P = .56). CONCLUSIONS: Use of both the pLAT and sLAT method of programming demonstrated significant improvement in 6MHW distance at 3 months with pLAT demonstrating a slightly higher responder rate based on CCS (P = .56). pLAT should be considered at minimum as equivalent in patients with no intrinsic conduction.

Rationale and design of a randomized trial to assess the safety and efficacy of MultiPoint Pacing (MPP) in cardiac resynchronization therapy: The MPP Trial.

BACKGROUND: Although the majority of Class III congestive heart failure (HF) patients treated with cardiac resynchronization therapy (CRT) show a clinical benefit, up to 40% of patients do not respond to CRT. This paper reports the design of the MultiPoint Pacing (MPP) trial, a prospective, randomized, double-blind, controlled study to evaluate the safety and efficacy of CRT using MPP compared to standard biventricular (Bi-V) pacing. METHODS: A maximum of 506 patients with a standard CRT-D indication will be enrolled at up to 50 US centers. All patients will be implanted with a CRT-D system (Quartet LV lead Model 1458Q with a Quadra CRT-D, Abbott) that can deliver both MPP and Bi-V pacing. Standard Bi-V pacing will be activated at implant. At 3 months postimplant, patients in whom the echocardiographic parameters during MPP are equal or better than during Bi-V pacing are randomized (1:1) to either an MPP or Bi-V arm. RESULTS: The primary safety endpoint is freedom from system-related complications at 9 months. Each patient's response to CRT will be evaluated using a heart-failure clinical composite score, consisting of a change in NYHA functional class, patient global assessment score, HF events, and cardiovascular death. The primary efficacy endpoint is the proportion of responders in the MPP arm compared with the Bi-V arm between 3 and 9 months. CONCLUSION: This trial seeks to evaluate whether MPP via a single quadripolar LV lead improves hemodynamic and clinical responses to CRT, both in clinical responders and nonresponders.

Less with More: Hospitalization Cost and Event Rates with Quadripolar versus Bipolar CRT-D System.

BACKGROUND: This is a comparative effectiveness study for cardiac resynchronization therapy defibrillator (CRT-D) therapy enabled by quadripolar (QUAD) versus bipolar (BIP) left ventricular (LV) leads.  Heart failure (HF) hospitalization (HFH) rates, associated costs, and 30-day readmissions after index HFH were compared. METHODS: Patients with de novo LV leads implanted as part of a CRT-D system between January 2011 and August 2013 with ≥1-year follow-up were included. Medical history, dates, and locations of HFH were collected thereafter. Patients were divided based on LV lead model: QUAD or BIP. Universal billing records (UB-04) for each HFH and ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification) diagnoses/procedure codes were used to classify hospitalizations as HF or non-HF and calculate concurrent U.S. national-average medicare reimbursement. Rates, associated payer costs, and 30-day readmissions were then compared using nonparametric bootstrapping. RESULTS: Baseline characteristics (N = 69 QUAD and N = 56 BIP) were similar. The inpatient HFH for the QUAD group (0.20/patient-year) was lower than the BIP group (0.31/patient-year, incidence rate ratio [IRR] = 0.62, P = 0.036). The overall HFH rate for the inpatient or outpatient setting for QUAD (0.29/patient-year) was lower than the BIP group (0.42/patient-year, IRR = 0.69, P = 0.055). Average cost of HFH in QUAD ($4,428/patient-year) was lower than BIP ($7,354/patient-year), a 39.8% cost reduction (P = 0.026). The 30-day readmission rate was also lower in QUAD compared to BIP (19% vs 28%, IRR = 0.68, P = 0.18). CONCLUSION: This U.S. economic comparative study demonstrated that QUAD exhibited lower postimplant inpatient HFH rates and reduced healthcare utilization compared to BIP systems.

Performance of the Quadripolar CRT-D system: 5-Year Results from the Quadripolar Pacing Post Approval Study.

BACKGROUND: Cardiac resynchronization therapy (CRT) is associated with challenges such as elevated capture thresholds, diaphragmatic stimulation, and lead instability. OBJECTIVE: Assess the chronic safety and efficacy of the quadripolar CRT-D device system with the Quartet 1458Q Left Ventricular (LV) lead in a CRT-indicated population followed for 5 years and evaluate all-cause mortality and impact of baseline characteristics on survival through 5 years. METHODS: Patients indicated for a CRT-D system were followed every 6 months post-implant for 5 years and assessed device performance and adverse events at each visit. The three primary endpoints were freedom from quadripolar CRT-D system-related complications through 5 years, freedom from Quartet 1458Q LV lead-related complications through 5 years, and the mean programmed pacing capture threshold at 5 years. RESULTS: The study enrolled 1,970 subjects at 71 sites. The quadripolar CRT-D system was successfully implanted in 97.2% of subjects. Freedom from quadripolar CRT-D device system-related complications through 5 years was 89.7% and freedom from Quartet 1458Q LV lead-related complications through 5 years was 95.7%. 3.49 % of subjects had LV lead-related complications and an overall LV lead complication rate was 0.0122 events per subject-year. A mean LV pacing capture threshold was 1.52 ± 1.01 V at 5 years. The 5-year survival rate was 67.4%. CONCLUSION: The quadripolar CRT-D system with the Quartet 1458Q LV lead exhibited low rates of complications and stable electrical performance through 5 years of follow-up and suggested a higher 5-year survival rate compared to traditional CRT systems.

Postoperative performance of the Quartet® left ventricular heart lead.

INTRODUCTION: The Quartet(®) left ventricular (LV) lead is the first with 4 pacing electrodes (tip and 3 rings) that enables pacing from 10 different pacing vectors. Postoperative performance of this lead was evaluated in a prospective, nonrandomized, multicenter IDE study. METHODS: Patients with standard indications for CRT-D were enrolled. Electrical performance and presence of phrenic nerve stimulation (PNS) were assessed during pacing from each of 10 vectors at predischarge (within 7 days), 1 month, and 3 months postimplant. RESULTS: The Quartet LV lead was implanted successfully in 170 patients (95.5% implant success rate, 68 ± 11 years, 68.5% male, LVEF: 25 ± 7%, NYHA class III: 98.3% and class IV: 1.7%). Mean follow-up was 4.7 ± 1.9 months. Capture threshold and impedance for each of the 10 LV lead pacing vectors remained stable during follow-up. LV lead dislodgement occurred in 6 (3.5%) patients and PNS was observed in 23 (13.5%) patients. PNS was resolved noninvasively in all 23 (100%) patients, either by reprogramming to pace from the additional LV lead pacing vectors alone (13 pts, 56.5%), reprogramming to pace from the additional LV lead pacing vectors and reprogramming pacing output (4 pts, 17.4%), or by reprogramming pacing output alone (6 pts, 26.1%). CONCLUSIONS: The Quartet LV lead electrical performance was stable and was associated with a high implant success and low dislodgement rate during 3-month follow-up. In all patients with PNS, the 10 pacing vectors combined with reduced output programming enabled the elimination of PNS noninvasively.

The Gallant™ system heart rhythm management device: making a connection.

Implantable cardiac defibrillators have revolutionized the way we prevent sudden cardiac death via arrhythmias. The addition of cardiac resynchronization pacing to defibrillators has broadened that treatment to include patients with heart failure and reduced ejection fraction. As with all technology, new devices and platforms expand the capabilities and interface with patients across the world. This review discusses the evolution from the initial modalities and methods of communication of implantable devices up to the most recent advances in implantable defibrillators and their integration into patient lives and clinical practice. This review is focused on the integration of Bluetooth communication into modern healthcare with the Gallant™ family of devices, the first branded launch by Abbott Laboratories.

The evolution in the ability of implantable cardioverter defibrillators to communicate has evolved quickly since their inception. In parallel, the volume of data and clinical utilities have also adapted how we manage our patients. Fast and reliable access to accurate clinical data allows for more deliberate and timely management of arrhythmia patients. The advent of Bluetooth technology and its recent integration into implantable medical devices may not only satisfy the clinicians needs, but also fill in some longstanding gaps for patients to participate in their own care. We discuss the Gallant™ ICD family of Implantable defibrillators and their advantages and design aspects of integrating Bluetooth technology.

Multipoint Pacing with Fusion-optimized Cardiac Resynchronization Therapy: Using It All to Narrow QRS Duration.

Adaptive atrioventricular (AV)-shortening algorithms have achieved QRS duration (QRSd) narrowing in traditional cardiac resynchronization therapy (CRT) patients. Multipoint pacing (MPP) has also demonstrated benefit in this population. An additional site of activation via intrinsic conduction of the septum may further contribute to CRT; however, the incorporation of all strategies together has yet to be explored. We therefore developed and tested a method combining MPP-CRT and controlled septal contribution to create a multifuse pacing (MFP) technique, establishing four ventricular activation sites for CRT patients using measurements from intracardiac electrograms (EGMs) and incorporating an AV-delay shortening algorithm (SyncAV™; Abbott Laboratories, Chicago, IL, USA) to narrow the QRSd. Patients in sinus rhythm with an AV conduction time of less than 350 ms were included in this analysis and were further stratified by strictly defined left bundle branch block (sLBBB) or nonspecific intraventricular conduction delay (IVCD). EGM-based measurements to determine the QRS septal onset to right ventricular (RV) time (SRAT) and the left ventricular (LV) to RV pacing conduction time were collected and applied to a formula to facilitate MFP. QRSd was compared between before and after programming. A total of 22 patients (19 men and three women) with similar baseline characteristics were compared (all values in mean ± standard deviation). The overall baseline QRSd of 153.31 ± 24.60 ms was decreased to 115.31 ± 16.31 ms after MFP programming (p < 0.0001). The measured SRAT was 59.40 ± 28.49 ms, resulting in a negative AV offset of -20.0 ± 24.97 ms. Patients in the sLBBB group (n = 7) were aged 67.8 ± 13.3 years and had a QRSd of 168.85 ± 27.29 ms that decreased to 113 ± 16.69 ms for a reduction of 55.42 ± 19.3 ms or 32.1% (p = 0.0003). In the IVCD group (n = 15), the baseline QRSd of 146.06 ± 20.29 ms was decreased to 116 ± 16.66 ms for a reduction of 30.07 ± 16.41 ms or 20.62% (p = 0.0001). When comparing the sLBBB and IVCD groups, the sLBBB group was favored by a reduction of 25.35 ms (p = 0.00046). Ultimately, MFP achieved statistically significant reductions in QRSd in all patients tested in this analysis. The benefit was also significantly better in the sLBBB group as compared with in the IVCD group.

Clinical performance of the St. Jude Medical Riata defibrillation lead in a large patient population.

OBJECTIVE: The purpose of this large multicenter study was to evaluate the long-term reliability of an implantable cardioverter defibrillator (ICD) lead to determine the incidence of adverse events (AEs). BACKGROUND: A recent concern has been the performance of cardiac defibrillator leads. There have been conflicting reports regarding the rate of lead perforation and other AEs. METHODS: Medical records from patients implanted from 6-1-2001 to 11-27-2007 with the St. Jude Medical Riata family of RV leads at 23 US (N = 12,969) and 5 German (N = 2,418) centers were reviewed for chronic lead-related AEs. These included perforation, dislodgment, conductor fracture and insulation damage. The mean follow-up period was 18.0 months. AEs were defined as those that required Riata lead revision, extraction, or replacement. RESULTS: The incidence of lead AEs was <1% for each AE type. Perforation occurred in 0.38%, dislodgement in 0.93%, conductor fracture in 0.18%, and insulation damage in 0.21% of patients studied. CONCLUSIONS: During the follow-up of the 15,387 patients with Riata leads, the incidence of AEs which included perforation, dislodgement, conductor fraction and insulation damage was low and within the range of what is considered clinically acceptable.

An Alarming Change: What Caused an Instance of Inappropriate Detection in a Wearable Cardioverter-defibrillator?

We describe the case of a patient who received cardiac resynchronization pacemaker therapy (CRT-P) incorporating bridge protection via a wearable cardioverter-defibrillator (WCD) while awaiting final evaluation for permanent placement of an implantable CRT device with defibrillation capabilities. In an attempt to mitigate symptoms of heart failure, reprogramming of the CRT-P with a V-V offset caused an unusual interaction and alarm from the WCD. This case highlights a unique interaction not previously reported and is clinically relevant to patients awaiting final evaluation for implantable defibrillator system placement.

Left Ventricular Enlargement, Cardiac Resynchronization Therapy Efficacy, and Impact of MultiPoint Pacing.

BACKGROUND: Left ventricular (LV) epicardial pacing results in slowly propagating paced wavefronts. We postulated that this effect might limit cardiac resynchronization therapy efficacy in patients with LV enlargement using conventional biventricular pacing with single-site LV pacing, but be mitigated by LV stimulation from 2 widely spaced sites using MultiPoint pacing with wide anatomic separation (MPP-AS: ≥30 mm). We tested this hypothesis in the multicenter randomized MPP investigational device exemption trial. METHODS: Following implant, quadripolar biventricular single-site pacing was activated in all patients (n=506). From 3 to 9 months postimplant, among patients with available baseline LV end-diastolic volume (LVEDV) measures, 188 received biventricular single-site pacing and 43 received MPP-AS. Patients were dichotomized by median baseline LVEDV indexed to height (LVEDVIMedian). Outcomes were measured by the clinical composite score (primary efficacy end point), quality of life, LV structural remodeling (↑EF >5% and ↓ESV 10%) and heart failure event/cardiovascular death. RESULTS: LVEDVIMedian was 1.1 mL/cm. Baseline characteristics differed in patients with LVEDVI>Median versus LVEDVI≤Median. Among patients with LVEDVI>Median, biventricular single-site pacing was less efficacious compared to patients with LVEDVI≤Median (clinical composite score, 65% versus 79%). In contrast, MPP-AS programming generated greater clinical composite score response (92% versus 65%, P=0.023) and improved quality of life (-31.0±29.7 versus -15.7±22.1, P=0.038) versus biventricular single-site pacing in patients with LVEDVI>Median. Reverse remodeling trended better with MPP-AS programming. In patients with LVEDVI>Median, heart failure event rate increased following the 3-month randomization point with biventricular single-site pacing (0.0150±0.1725 in LVEDVI>Median versus -0.0190±0.0808 in LVEDVI ≤Median, P=0.012), but no heart failure event occurred in patients with MPP-AS programming between 3 and 9 months in LVEDVI>Median. All measured outcomes did not differ in patients receiving MPP-AS and biventricular single-site pacing with LVEDVI≤Median. CONCLUSIONS: Conventional biventricular single-site pacing, even with a quadripolar lead, has reduced efficacy in patients with LV enlargement. However, the greatest response rate in patients with larger hearts was observed when programmed to MPP-AS pacing.

Does size really matter? A comparison of the Riata lead family based on size and its relation to performance.

BACKGROUND: Recently, the performance and safety of smaller diameter implantable cardioverter defibrillator (ICD) leads has been questioned. The purpose of this analysis was to determine the impact of size on lead performance and perforation rates by comparing the performance of 7 French (7F) and 8 French (8F) leads with similar design characteristics implanted by a single operator. METHODS: Patients implanted with a Riata 1580 (8F) or 7000 (7F) series leads (St. Jude Medical, Sylmar, CA, USA) over a 2-year period were evaluated to compare performance and perforation rates. RESULTS: There were 357 Riata 8F leads and 357 Riata 7F leads implanted in 714 patients. Follow-up ranged from 1 to 24 months. The 8F leads were implanted in the right ventricular apex more often than were 7F leads (129 or 37% vs 72 or 20%, P < 0.0001). Oversensing that did not result in therapy occurred in 2 pts (0.56%) with 8F leads and 1 pt. (0.28%) with a 7F lead (P = 0.56). Oversensing with therapy occurred once in both groups (0.28%, P = NS). One perforation occurred in each group (0.28%, P = NS). Both occurred in leads that were implanted in the right ventricular apex (P = 0.02). CONCLUSIONS: The performance of St. Jude Medical 7F and 8F Riata leads was similar. The incidence of lead-related adverse events was within or below the low end of published acceptable ranges for ICD lead perforation and sensing anomalies. Perforations were less likely to occur in leads that were implanted in nonapical positions.

Acute evaluation of programmer-guided AV/PV and VV delay optimization comparing an IEGM method and echocardiogram for cardiac resynchronization therapy in heart failure patients and dual-chamber ICD implants.

INTRODUCTION: Intracardiac delay optimization of biventricular and dual-chamber pacing devices currently relies on time-consuming echocardiographic measurements. A novel intracardiac electrogram (IEGM) method for atrioventricular (AV/PV) and interventricular (VV) delay optimization was developed, which can be performed during routine device follow-up. METHODS AND RESULTS: In this prospective, nonrandomized, multi-center trial, patients previously implanted with St. Jude Medical cardiac resynchronization therapy defibrillator (CRT-D) devices or dual-chamber implantable cardioverter defibrillators (ICDs) underwent standard AV/PV and/or VV delay optimization guided by Doppler echocardiogram measurements of the maximum aortic velocity time integral (aortic VTI). Aortic VTI measurements applying the IEGM method recommended delays were then obtained in all patients. Fifty-eight patients (age: 68 +/- 11 years; 81% male; 74% ischemic) and 57 patients (age: 71 +/- 10 years; 74% male; 71% ischemic) were enrolled for AV/PV and VV delay evaluation, respectively. An independent core lab determined the maximum aortic VTIs. Data analysis of the AV, PV, and VV delays demonstrated the concordance correlation coefficient (CCC) between the standard method aortic VTI values and the IEGM method aortic VTI values was 97.5%, 96.1%, and 96.6%, respectively. All analyses demonstrated that the CCC > 90% (P < 0.05). CONCLUSION: The automated programmer-based IEGM method provides a reliable and simpler alternative to standard techniques for the optimization of AV/PV and VV delay settings in patients with CRT-D devices and dual-chamber ICDs.

Safety and Efficacy of Multipoint Pacing in Cardiac Resynchronization Therapy: The MultiPoint Pacing Trial.

OBJECTIVES: The MultiPoint Pacing (MPP) trial assessed the safety and efficacy of pacing 2 left ventricular sites with a quadripolar lead in patients with heart failure indicated for a CRT-D device. BACKGROUND: Cardiac resynchronization therapy nonresponse is a complex problem where stimulation of multiple left ventricular sites may be a solution. METHODS: Enrolled patients were indicated for a CRT-D system. Bi-ventricular (Bi-V) pacing was activated at implant. Three months later, clinical response was assessed and the patient was randomized (1:1) to receive Bi-V pacing or MPP. Patients were followed for 6 months post-randomization and clinical response was again assessed. RESULTS: The CRT-D system was successfully implanted in 455 of 469 attempted implants (97%). A total of 381 patients were randomized to Bi-V or MPP at 3 months. The primary safety endpoint was met with freedom from system-related complications of 93.2%. The primary efficacy endpoint of the noninferiority comparison of nonresponder rates between the 2 arms was met. Patients randomized to MPP arm and programmed to pace from anatomically distant poles (MPP-AS) responded to therapy at significantly higher rates than MultiPoint pacing-other programmed settings (MPP-Other). Within this group, 87% were responders at 9 months, 100% designated as nonresponders at 3 months converted to responders at 9 months, and 54% experienced an incremental response compared to MPP-Other. Also within MPP-AS, 92% of patients with de novo CRT-D implant were classified as responders compared with patients with MPP-Other. CONCLUSIONS: MPP is safe and effective for treating heart failure. The study met the pre-specified hypothesis that response to MPP is noninferior to Bi-V pacing with a quadripolar left ventricular lead. (MultiPoint Pacing IDE Study [MPP IDE]; NCT01786993).

What is the cost of non-response to cardiac resynchronization therapy? Hospitalizations and healthcare utilization in the CRT-D population.

BACKGROUND: Cardiac resynchronization therapy (CRT) is an effective treatment for heart failure (HF) with left ventricular systolic dysfunction and prolonged QRS interval. However, one third of patients do not benefit from treatment. This study compares the heart failure hospitalization (HFH) rates and corresponding costs between responders and non-responders to CRT. METHODS: At a single center in New Jersey, we enrolled patients with de novo CRT-D implants between January 2011 and July 2013. Medical history at implant and all subsequent hospitalizations were collected. A retrospective chart review of the cardiology visit at or closest to 12 months post-CRT implant was performed, and patients were classified into responders and non-responders. Universal billing records (UB-04), ICD-9-CM diagnoses, and procedure codes were used to determine whether each hospitalization was due to HF. For each heart failure hospitalization (HFH), an MS-DRG-based US national average Medicare reimbursement was determined. HFH rates and associated payor costs were compared between responders and non-responders using negative binomial regression and non-parametric bootstrapping (×10,000), respectively. RESULTS: CRT response was determined in 135 patients (n = 103 responders, n = 32 non-responders, average follow-up 1.4 years). Demographics, pre-implant HF characteristics, NYHA Class, QRS duration, ejection fraction (EF), left bundle branch block (LBBB) status, and co-morbidities were not statistically different between the two groups. The HFH rate was significantly lower in responders (0.43/patient year) compared to non-responders (0.96/patient year, IRR = 0.45, 95 % CI (0.23 0.90), P = 0.0197). Average US national Medicare reimbursement for the responder group (US$7205/patient year) was 48 % lower than that for the non-responder group (US$13,861/patient year, P = 0.035). CONCLUSION: In this single-center retrospective study, responders to CRT had significantly lower rates of post-implant heart failure hospitalization rate and reduced associated payor costs compared to non-responders. Therapies that increase CRT response rates can substantially reduce healthcare utilization.

Profile of St. Jude Medical's Allure Quadra quadripolar pacemaker system for cardiac resynchronization therapy.

Congestive heart failure is a major public health epidemic and economic burden in the USA and worldwide. Cardiac resynchronization therapy is an effective therapy for treating congestive heart failure in conjunction with pharmacologic therapy. The average congestive heart failure admission costs approximately US$ 8 billion annually. Current cardiac resynchronization therapy pacemaker systems from various manufacturers deliver therapy-utilizing bipolar leads including the left ventricle, with electrode spacing ranging from 8 to 22 mm. The Quartet LV™ lead model 1458Q (St. Jude Medical Sylmar, CA) is a quadripolar lead with a 4.0 Fr. tip electrode and three 4.7 Fr. ring electrodes located 20, 30 and 47 mm from the tip. The Quartet lead and Allure Quadra TM allows 14 pacing configurations, providing benefits, including reductions in phrenic nerve stimulation, reduced pacing thresholds, improved battery longevity and potential reductions, in non-responders to cardiac resynchronization therapy. In addition, there is cost benefit data from utilizing quadripolar technology compared with traditional bipolar cardiac resynchronization therapy.

Role of Bi-Atrial Pacing In Slowing The Progression of Paroxysmal Atrial Fibrillation To Permanent Atrial Fibrillation.

Introduction: Bi-atrial lead placement combined with atrial overdrive pacing has demonstrated a reduction in percent time mode switched and mode switches per day. This retrospective analysis compared long term outcomes of patients with right atrial overdrive pacing alone (DAO) to patients having atrial overdrive with bi-atrial leads (BIA) in slowing the progression of paroxysmal atrial fibrillation (PAF) to permanent continuous atrial fibrillation (CAF). Methods: Thirty-three patients age 76.6 (+/-1.96) from our prior investigation were selected. The DAO control group (N=16) had received a standard right atrial pacing lead. The BIA group (N=17) had pacing leads placed in the right atrium and coronary sinus. Patients were followed for a mean 1217 days (+/-838). Days of CAF was classified as the date of final mode switch until analysis. Results: A total of 40,171 follow-up days were evaluated. The mean follow-up for both cohorts was 1217 days (+/-838). The DAO group consisted of 15,318 days (mean 957 +/-761) and the BIA group 24,853 days (mean 1461 +/-854). A lower total number of days were spent in CAF in the BIA group versus the DAO group, 1380 vs 2197 respectively. Corrected for follow-up duration, 5.55% days in CAF was seen in the BIA group vs. 14.34% in the DAO group which did not reach statistical significance. Conclusions: Although BIA overdrive pacing initially demonstrated reduced time in mode switch compared to DAO alone, this analysis did not detect a reduction in progression to CAF. More subjects or a longer follow up would be needed.

Feasibility of using multivector impedance to monitor pulmonary congestion in heart failure patients.

PURPOSE: Pulmonary edema (PE) is associated with fluid accumulation in the lungs. Device-based impedance measurements have been used to detect fluid overload prior to hospitalization. However, studies have reported a high false positive rate (FPR). The objective of this study was to develop and test a new multivector impedance-based algorithm that reliably tracks PE clinical events. METHODS: We enrolled patients with implanted CRT-Ds in 23 US centers within 2 weeks of device implant. Six-vector impedance data was collected automatically by the CRT-Ds every 30 min during emergency department visits/hospitalizations and every 2 h at all other times. Detection algorithms for cardiac resynchronization therapy defibrillator (CRT-D) and implantable cardiac defibrillator (ICD) devices were developed using those impedance vectors that would be available in corresponding devices and retrospectively evaluated. RESULTS: There were 75 patients (69 % male), mean age 66 ± 12 years, with a LVEF of 23 ± 6 % and QRS of 149 ± 25 ms. Twenty-one major clinical events occurred over 8.2 ± 2.6 months of follow-up time. CRT-D vector combinations resulted in a sensitivity of 71.4 % (95 % confidence interval 47.8-88.7) and a FPR of 0.56 (0.30-0.94) false positives per patient-year (FPs/pt-yr); ICD vector combinations resulted in a sensitivity of 61.9 % (38.4-81.9) and a FPR of 0.63 (0.36-0.90) FPs/pt-yr. In comparison, the single-vector RVCoil-Can implementation of this algorithm resulted in a sensitivity of 57.1 % (34.0-78.2) and a FPR of 0.74 (0.44-1.12) FPs/pt-yr. CONCLUSIONS: This multivector impedance algorithm was effective in tracking PE clinical events in this patient population. Additional studies are needed to prospectively evaluate the performance of this algorithm in a larger population.