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Background Prolongation of the baseline ECG PR interval is frequently encountered among cardiac resynchronization therapy (CRT) recipients. There are conflicting data regarding the association of a prolonged PR interval with long-term clinical outcome in this patient group. Objective The purpose of this study was to compare clinical outcomes and response to CRT in patients with normal ( Methods In this study, 283 patients (normal PR interval: n=158; prolonged PR interval: n=125) with documented baseline intrinsic PR interval were followed for 3 years after CRT implantation. The study population consisted of 24.7% women (mean age 66 ± 13 years, left ventricular ejection fraction 24% ± 7%). Results A Cox proportional hazard model identified baseline PR interval as a predictor of the composite end-point (all-cause mortality, heart failure hospitalization, left ventricular assist device implantation, and heart transplantation) in univariate analysis (hazard ratio [HR] 1.49, 95% confidence interval [CI] 1.02–2.17, P = .04) but not in multivariate analysis. It also predicted heart failure hospitalization in univariate (HR 1.6, 95% CI 1.1–2.4, P = .02) and multivariate analysis (HR 1.6, 95% CI 1.0–2.3, P = .03). A prolonged PR interval was associated with lower probability of reverse remodeling defined as ≥10% improvement in ejection fraction (64% vs 77%, P = .057), especially in patients with non–left bundle branch block ECG morphology (41% vs 68%, P = .03). Conclusion Among patients with CRT, a prolonged baseline PR interval is an independent predictor of worse prognosis and lower probability of reverse remodeling, especially for patients with non–left bundle branch block morphology on ECG.

Background Chronic anticoagulation is recommended for atrial fibrillation (AF) patients with thromboembolic risk factors regardless of AF duration/frequency. Continuous rhythm assessment with pacemakers (PMs)/implantable cardioverter-defibrillators (ICDs) and use of direct-acting oral anticoagulants (DOACs) may allow anticoagulation only around AF episodes, reducing bleeding without increasing thromboembolic risk. Objective The purpose of this study was to evaluate the feasibility/safety of intermittent DOAC use guided by continuous remote AF monitoring via dual-chamber PMs or ICDs. Methods Patients with nonpermanent AF, current DOAC use, CHADS2 score ≤3, a St. Jude Medical dual-chamber PM or ICD, and rare AF episodes were followed with biweekly and AF-alert based remote transmissions. Patients free of AF episodes lasting ≥6 minutes with a total AF burden Results Among 48 patients (mean age 71.3 years; 65% male; 79% paroxysmal AF; 87% CHADS2 score 1–2), 14,826 days of monitoring were completed. Patients used DOACs for 3763 days, representing a 74.6% reduction in anticoagulation time compared to chronic administration. Adverse events included 2 gastrointestinal bleeds (both on DOAC), 1 fatal intracerebral bleed (off DOAC), and no thromboembolic/stroke events. Conclusion Among patients with rare AF episodes and low-to-moderate stroke risk, PM/ICD-guided DOAC administration is feasible and decreased anticoagulation utilization by 75%. Few adverse events occurred, although the study was not powered to assess these outcomes. PM/ICD-guided DOAC administration may prove a viable alternative to chronic anticoagulation. Future studies are warranted.

Background Repolarization alternans (RA), a pattern of ventricular repolarization that repeats on an every other beat basis, has been closely linked with the substrate associated with ventricular tachycardia/ventricular fibrillation. Objective To evaluate a novel method to suppress RA. Methods We have developed a novel method to dynamically (on R-wave detection) trigger pacing pulses during the absolute refractory period. We have tested the ability of this method to control RA in a structurally normal swine heart in vivo. Results RA induced by triggered pacing can be measured from both intracardiac and body surface leads and the amplitude of R-wave triggered pacing-induced alternans can be locally modulated by varying the amplitude and width of the pacing pulse. We have estimated that to induce a 1 μV change in alternans voltage on the body surface, coronary sinus, and left ventricle leads, a triggered pacing pulse delivered in the right ventricle of 0.04±0.02, 0.05±0.025, and 0.06±0.033 μC, respectively, is required. Similarly, to induce a 1 unit change in K score (ratio of alternans peak to noise), a pacing stimulus of 0.93±0.73, 0.32±0.29, and 0.33±0.37 μC, respectively, is required. We have been able to demonstrate that RA can be suppressed by R-wave triggered pacing from a site that is within or across ventricles. Lastly, we have demonstrated that the proposed method can be used to suppress spontaneously occurring alternans in the diseased heart. Conclusion We have developed a novel method to suppress RA in vivo.

Background Predictable progression to battery depletion is necessary for device management in patients with pacemakers or implantable cardioverter-defibrillators, particularly in patients who either are pacemaker dependent or have required implantable cardioverter-defibrillator therapies. Objective To determine the incidence and characteristics of unexpected battery depletion in patients implanted with a cardiac resynchronization therapy – defibrillator (CRT-D) device. Methods All patients with a St Jude Atlas+ HF or Atlas II HF CRT-D device implanted between 2004 and 2007 at the Massachusetts General Hospital and the Nashville VA Medical Center (Vanderbilt University) were studied. All patients with early generator depletion (transition of generator voltage above specified elective replacement indicator [ERI] to end of life [EOL] in less than 90 days) were evaluated further. Results Eight cases (mean age 69.6 ± 9 years) with abrupt battery depletion were identified among 191 patients (4.2%) implanted with a St Jude Atlas CRT-D device. The longevity of 8 premature depletion devices was 46.4 ± 10 months (median 45 months). The battery voltage in these 8 devices decreased from a mean of 2.48 ± 0.03 V (above ERI) to 2.3 ± 0.08 V (below ERI) over 33.3 ± 23 days (range 1–59 days; median 38.5 days). One device reached EOL status within 1 day of having battery voltage above ERI and another device within 12 days. Conclusion The incidence of abrupt battery depletion was 4.2% in patients implanted with a St Jude Atlas CRT-D device. No common mechanism has been identified for this failure. Close monitoring of battery voltage and timely generator replacement are required in patients with these devices.

The optimal pacing site for cardiac resynchronization therapy (CRT) is along the left ventricle (LV) lateral or posterolateral wall. However, little is known about the impact of segmental pacing site on outcomes.We assessed the impact of segmental LV lead position on CRT outcomes.Patients (n = 115) undergoing CRT were followed prospectively. Segmental LV lead position along the longitudinal axis (apical, midventricle, or basal) was determined retrospectively by examining coronary sinus (CS) venograms and chest X-rays. The primary outcome was a combined endpoint of heart failure hospitalization, cardiac transplantation, or all-cause mortality. Secondary outcomes included change in New York Heart Association (NYHA) functional class and degree of LV reverse remodeling.Patients were divided into two groups based on LV lead position: apical (n = 25) and basal/midventricle (n = 90). The apical group was older (72.9 +/- 8.9 vs. 66.5 +/- 13.3 years; P = .010) and more likely to have ischemic cardiomyopathy (77% vs. 52%, P.001). During a mean follow-up of 15.1 +/- 9.0 months, event-free survival was significantly lower in the apical group: 52% vs. 79%, hazard ratio [HR] 2.7 (95% confidence interval [CI] 1.5-5.5, P = .006). The adverse impact of apical lead placement remained significant after adjusting for clinical covariates: HR 2.3 (95% CI 1.1-4.8, P = .03). The apical group also experienced less improvement in NYHA functional class and less LV reverse remodeling.Apical LV lead placement is associated with worse CRT outcomes. Preferential positioning of LV leads in the basal/midventricle segments may improve outcomes.

Permanent cardiac pacemakers have historically been considered a contraindication to magnetic resonance imaging (MRI).The purpose of the ProMRI Phase B Study, a multicenter, prospective, single-arm, nonrandomized study, was to evaluate the clinical safety of the Biotronik ProMRI pacemaker system in patients undergoing thoracic spine and cardiac MRI.The ProMRI Phase B study enrolled 245 patients with stable baseline pacing indices implanted with an Entovis pacemaker (DR-T or SR-T) and Setrox 53-cm and/or 60-cm lead(s). Device interrogation was performed at enrollment, pre- and post-MRI scan, and 1 and 3 months post-MRI. End-points were (1) freedom from MRI- and pacing system-related serious adverse device effects through 1 month post-MRI; (2) freedom from atrial and ventricular MRI-induced pacing threshold increase (0.5 V); and (3) freedom from P- and R-wave amplitude attenuation (50%), or P wave1.5 mV, or R wave5.0 mV at 1 month post-MRI.In total, 216 patients completed the MRI and 1-month post-MRI follow-up. One adverse event possibly related to the implanted system and the MRI procedure occurred, resulting in a serious adverse device effect-free rate of 99.6% (220/221; P.0001. Freedom from atrial and ventricular pacing threshold increase was 100% (194/194, P.001) and 100% (206/206, P.001) respectively. Freedom from P- and R-wave amplitude attenuation was 98.2% (167/170, P.001) and 100% (188/188, P.001) respectively.The results of the ProMRI Phase B study demonstrate the clinical safety and efficacy of the ProMRI pacemaker system in patients subjected to thoracic spine and cardiac MRI conditions.

Intracardiac electrograms can be used to guide left ventricular (LV) lead placement during implantation of cardiac resynchronization therapy (CRT) devices. Although attempts often are made to ensure that the LV lead is positioned at a site of maximal electrical delay, information on whether this is useful in predicting the acute hemodynamic response and long-term clinical outcome to CRT is limited.The purpose of this study was to assess the ability of intracardiac (electrogram) measurements made during LV lead placement in patients undergoing CRT for predicting acute hemodynamic response and long-term clinical outcome to CRT.Seventy-one subjects with standard indications for CRT underwent electrogram measurements and echocardiograms performed in the acute phase of this study. The LV lead electrical delay was measured intraoperatively from the onset of the surface ECG QRS complex to the onset of the sensed electrogram on the LV lead, as a percentage of the baseline QRS interval. Echocardiographic assessment of the hemodynamic response to CRT was measured as an intra-individual percentage change in dP/dt over baseline (DeltadP/dt, derived from the mitral regurgitation Doppler profile) with CRT on and off. dP/dt was measurable in 48 subjects, and acute responders to CRT were defined as those with DeltadP/dtor=25%. Long-term response was measured as a combined endpoint of hospitalization for heart failure and/or all cause mortality at 12 months. Time to the primary endpoint was estimated by the Kaplan-Meier method, with comparisons made using the log rank test.LV lead electrical delay correlated weakly with DeltadP/dt of the combined group (n = 48, r = 0.311, P = .029) but was strongly correlated with DeltadP/dt in the nonischemic subgroup (n = 20, r = 0.48, P = .027). LV lead electrical delay (%) was significantly longer in acute responders (69.6 +/- 23.9 vs 31.95 +/- 11.57, P = .002) among patients with nonischemic cardiomyopathy. A reduced LV lead electrical delay (50% of the QRS duration) was associated with worse clinical outcome within the entire cohort (hazard ratio: 2.7, 95% confidence interval: 1.17-6.68, P = .032) as well as when stratified into ischemic and nonischemic subgroups.Measuring LV lead electrical delay is useful during CRT device implantation because it may help predict hemodynamic response and long-term clinical outcome.

Both anatomic and electrical locations of the left ventricular (LV) lead have been identified as important predictors of clinical outcomes in cardiac resynchronization therapy (CRT). The impact of LV lead location on incident device-treated ventricular arrhythmia (VA), however, is not well understood.To assess the relationship between electrical and anatomic LV lead location and device treated VAs in CRT.Sixty-nine patients undergoing CRT implantation for standard indications were evaluated. Anatomic LV lead location was assessed by means of coronary venography and chest radiography and categorized as apical or nonapical. Electrical LV lead location was assessed by LV electrical delay (LVLED) and was calculated as the time between the onset of the native QRS on the surface electrocardiogram and sensed signal on the LV lead during implantation and corrected for native QRS. Incident appropriate device-treated VA was assessed via device interrogation.Apical lead placement was an independent predictor of VAs (hazard ratio 5.29; 95% confidence interval 1.69-16.5; P = .004). Among patients with a nonapical lead, LVLED50% native QRS was an independent predictor of VAs (hazard ratio 6.90; 95% confidence interval 1.53-31.1; P = .012). Those with a nonapical lead and LVLED ≥ 50% native QRS were at substantially lower risk for first incident and recurrent VAs when compared to all other patients.The apical lead position is associated with an increased risk of VAs in CRT patients. Among patients with a nonapical lead position, an LVLED of50% of the native QRS is associated with an increased risk of VAs.

Background Pulmonary vein isolation (PVI) is recognized as a potentially curative treatment for atrial fibrillation (AF). Ablation of complex fractionated atrial electrograms (CFAEs) in addition to PVI has been advocated as a means to improve procedural outcomes, but the benefit remains unclear. Objective This study sought t synthesize the available data testing the incremental benefit of adding CFAE ablation to PVI. Methods We performed a meta-analysis of controlled studies comparing the effect of PVI with CFAE ablation vs. PVI alone in patients with paroxysmal and nonparoxysmal AF. Results Of the 481 reports identified, 8 studies met our inclusion criteria. There was a statistically significant increase in freedom from atrial tachyarrhythmia (AT) with the addition of CFAE ablation (relative risk [RR] 1.15, P = .03). In the 5 reports of nonparoxysmal AF (3 randomized controlled trials, 1 controlled clinical trial, and 1 trial using matched historical controls), addition of CFAE ablation resulted in a statistically significant increase in freedom from AT (n = 112 of 181 [62%] for PVI+CFAE vs. n=84 of 179 [47%] for PVI alone; RR 1.32, P = .02). In trials of paroxysmal AF (3 randomized controlled trials and 1 trial using matched historical controls), addition of CFAE ablation did not result in a statistically significant increase in freedom from AT (n = 131 of 166 [79%] for PVI+CFAE vs. n=122 of 164 [74%] for PVI alone; RR 1.04, P = .52). Conclusion In these studies of patients with nonparoxysmal AF, addition of CFAE ablation to PVI results in greater improvement in freedom from AF. No additional benefit of this combined approach was observed in patients with paroxysmal AF.

Background Three-dimensional (3D) reconstruction of the left atrium (LA) can be performed using real-time intracardiac echocardiography (ICE) to facilitate image integration during atrial fibrillation (AF) ablation. Current users of this technology generally image the LA indirectly from the right atrium (RA). Objective The purpose of this study was to assess the feasibility and accuracy of image integration with placement of the ICE catheter directly in the LA to visualize the LA. Methods Thirty consecutive patients undergoing an AF ablation with the CARTO-Sound system were enrolled. A 10-Fr phased-array ICE catheter was used to obtain two-dimensional echocardiographic images of the LA; in 15 patients the ICE probe was placed in the LA, and in 15 patients it was placed only in the RA. Sequential images were obtained and merged with a preacquired computed tomography/magnetic resonance image. The accuracy of image integration was assessed by the value of the average image integration error after surface registration. Results Thirty patients (60% paroxysmal AF, LA size=42 ± 7 mm, ejection fraction=62% ± 10%) were studied. There was no difference in the time required to create the LA anatomic map and perform image integration with imaging from the LA versus the RA (22 ± 22 vs. 24 ± 16 minutes; P = .8). The number of ultrasound contours obtained was also similar (LA = 26 ± 17 vs. RA=24 ± 16; P = .7). The average integration error was less with direct LA imaging (LA = 1.83 ± 0.32 vs. RA=2.52 ± 0.58 mm; P = .0004). Conclusion Direct LA imaging with ICE is feasible and results in improved LA visualization and image integration.

Background Recent studies have reported a possible increased risk of delayed perforation with the St. Jude Riata defibrillator lead. Objective The purpose of this study was to determine the incidence and time of occurrence of this complication in a large number of patients who underwent implantationm at a single center. Methods We reviewed the data and clinical course on all patients who underwent implantation of the St. Jude Riata (1580/1581, 1590/1591, and the 7000/7001 ST series) right ventricular defibrillator lead at the Massachusetts General Hospital between June 2001 and October 2007. Data were compared with all Medtronic Sprint Fidelis leads implanted during the same time period. Results Of a total of 416 implanted Riata leads, follow-up data at 6 weeks and 3 months was available for 87% and 75% of patients, respectively. There were 6 cases of lead perforation (6 of 233, 2.6%) with the 1580/1581 series, no cases of lead perforation (0 of 92) with the 1590/1591 series, and 2 cases of perforation (2 of 92, 2.2%) with the 7000/7001 ST series. Interrogation the day after implantation did not reveal any abnormalities. Patients with perforation developed symptoms of chest pain or shortness of breath within 3 weeks post-implantation; interrogation revealed pacing thresholds of >5 V at 0.5 ms within the first follow-up period of 6 weeks. Conclusion All cases of perforation with the St. Jude Riata lead occurred within 6 weeks post-implantation and showed pacing thresholds >5 V at 0.5 ms. There were no cases of delayed perforation after 6 weeks in 307 patients with at least 3 months of follow-up.

Background With the increasing use of implantable cardioverter-defibrillators (ICDs), device complications are becoming more common. Fungal-related ICD infections have rarely been reported, and little is known about the presentation, prevalence, and treatment options for these morbid infections. Objectives The purpose of this study was to characterize the clinical features, treatment, and outcomes of patients with fungal ICD infections. Methods We performed a retrospective review of ICD procedures performed at a single academic center and identified all ICD-related infections managed between 1983 and 2005. Results Among a total of 3,648 ICD-related procedures performed between 1983 and 2005, we identified 47 (1.3%) cases of ICD infections, of which 5 (0.1%) were due to a fungal pathogen. Fungal infections were more likely to be associated with abdominal devices, to have a local rather than systemic infection, and to have a longer duration from the original implant to presentation. All patients were treated with ICD system explantation and antifungal therapy. Conclusion Fungal infection of ICDs is a rare but serious complication of device implantation that must be treated aggressively with complete hardware explantation and prolonged antifungal therapy. Because most infections are late complications and have indolent onsets, a high level of clinical suspicion is required for early diagnosis.

A 48-year-old man with a history of ischemic cardiomyopathy and coronary artery bypass surgery (left ventricular ejection fraction 15%), New York Heart Association class III congestive heart failure, and a left bundle branch block (QRS duration 146 ms) was scheduled for elective placement of cardiac resynchronization therapy (CRT) combined with a defibrillator. He had been completely free of angina since bypass surgery, and he had no history of arterial or venous spasm. The right atrial pacing lead and right ventricular pacing/defibrillator lead were placed via the left cephalic vein, and a guiding catheter (Guidant/Boston Scientific Corp.) was placed via a left subclavian puncture and manipulated easily into the coronary sinus (CS). Contrast CS venography performed in the left anterior oblique view (LAO) with a balloon-tipped occlusion catheter revealed a widely patent CS with favorable branches for left ventricular (LV) lead placement supplying the lateral LV (Figure 1A).