Upgrading right ventricular pacemakers to biventricular pacing or conduction system pacing: a systematic review and meta-analysis.

Guidelines recommend patients undergoing a first pacemaker implant who have even mild left ventricular (LV) impairment should receive biventricular or conduction system pacing (CSP). There is no corresponding recommendation for patients who already have a pacemaker. We conducted a meta-analysis of randomized controlled trials (RCTs) and observational studies assessing device upgrades. The primary outcome was the echocardiographic change in LV ejection fraction (LVEF). Six RCTs (randomizing 161 patients) and 47 observational studies (2644 patients) assessing the efficacy of upgrade to biventricular pacing were eligible for analysis. Eight observational studies recruiting 217 patients of CSP upgrade were also eligible. Fourteen additional studies contributed data on complications (25 412 patients). Randomized controlled trials of biventricular pacing upgrade showed LVEF improvement of +8.4% from 35.5% and observational studies: +8.4% from 25.7%. Observational studies of left bundle branch area pacing upgrade showed +11.1% improvement from 39.0% and observational studies of His bundle pacing upgrade showed +12.7% improvement from 36.0%. New York Heart Association class decreased by -0.4, -0.8, -1.0, and -1.2, respectively. Randomized controlled trials of biventricular upgrade found improvement in Minnesota Heart Failure Score (-6.9 points) and peak oxygen uptake (+1.1 mL/kg/min). This was also seen in observational studies of biventricular upgrades (-19.67 points and +2.63 mL/kg/min, respectively). In studies of the biventricular upgrade, complication rates averaged 2% for pneumothorax, 1.4% for tamponade, and 3.7% for infection over 24 months of mean follow-up. Lead-related complications occurred in 3.3% of biventricular upgrades and 1.8% of CSP upgrades. Randomized controlled trials show significant physiological and symptomatic benefits of upgrading pacemakers to biventricular pacing. Observational studies show similar effects between biventricular pacing upgrade and CSP upgrade.

Standard care vs. TRIVEntricular pacing in Heart Failure (STRIVE HF): a prospective multicentre randomized controlled trial of triventricular pacing vs. conventional biventricular pacing in patients with heart failure and intermediate QRS left bundle branch block.

AIMS: To determine whether triventricular (TriV) pacing is feasible and improves CRT response compared to conventional biventricular (BiV) pacing in patients with left bundle branch block (LBBB) and intermediate QRS prolongation (120-150 ms). METHODS AND RESULTS: Between October 2015 and November 2019, 99 patients were recruited from 11 UK centres. Ninety-five patients were randomized 1:1 to receive TriV or BiV pacing systems. The primary endpoint was feasibility of TriV pacing. Secondary endpoints assessed symptomatic and remodelling response to CRT. Baseline characteristics were balanced between groups. In the TriV group, 43/46 (93.5%) patients underwent successful implantation vs. 47/49 (95.9%) in the BiV group. Feasibility of maintaining CRT at 6 months was similar in the TriV vs. BiV group (90.0% vs. 97.7%, P = 0.191). All-cause mortality was similar between TriV vs. BiV groups (4.3% vs. 8.2%, P = 0.678). There were no significant differences in echocardiographic LV volumes or clinical composite scores from baseline to 6-month follow-up between groups. CONCLUSION: Implantation of two LV leads to deliver and maintain TriV pacing at 6 months is feasible without significant complications in the majority of patients. There was no evidence that TriV pacing improves CRT response or provides additional clinical benefit to patients with LBBB and intermediate QRS prolongation and cannot be recommended in this patient group. CLINICAL TRIAL REGISTRATION NUMBER: Clinicaltrials.gov: NCT02529410.

Multipoint pacing for cardiac resynchronisation therapy in patients with heart failure: A systematic review and meta-analysis.

INTRODUCTION: Multipoint pacing (MPP) has been proposed as an effective way to improve cardiac resynchronisation therapy (CRT) response. We performed a systematic review and meta-analysis evaluating the efficacy of CRT delivered via MPP compared to conventional CRT. METHODS: A literature search was performed from inception to January 2021 for studies in Medline, Embase and Cochrane databases, comparing MPP to conventional CRT with a minimum of 6 months follow-up. Randomised and nonrandomised studies were assessed for relevant efficacy data including echocardiographic (left ventricular end systolic volume [LVESV] and ejection fraction) or functional changes (New York Heart Association [NYHA] class/Clinical Composite Score). Subgroup analyses were performed by study design and programming type. RESULTS: A total of 7 studies with a total of 1390 patients were included in the final analysis. Overall, MPP demonstrated greater echocardiographic improvement than conventional CRT in nonrandomised studies (odds ratio [OR]: 5.33, 95% confidence interval [CI]: [3.05-9.33], p < .001), however, was not significant in randomised studies (OR: 1.86, 95% CI: [0.91-3.79], p = .086). There was no significant difference in LVESV reduction >15% (OR: 1.96, 95% CI: [0.69-5.55], p = .20) or improvement by ≥1 NYHA class (OR: 2.49, 95% CI: [0.74-8.42], p = .141) when comparing MPP to conventional CRT. In a sub analysis, MPP programmed by widest anatomical separation (MPP-AS) signalled greater efficacy, however, only 120 patients were included in this analysis. CONCLUSION: Overall MPP was more efficacious in nonrandomised studies, and not superior when assessed in randomised studies. There was considerable heterogeneity in study design making overall interpretation of results challenging. Widespread MPP programming in all CRT patients is currently not justified. Further large, randomised studies with patient-specific programming may clarify its effectiveness.

Feasibility of intraprocedural integration of cardiac CT to guide left ventricular lead implantation for CRT upgrades.

BACKGROUND: Optimal positioning of the left ventricular (LV) lead is an important determinant of cardiac resynchronization therapy (CRT) response. OBJECTIVE: Evaluate the feasibility of intraprocedural integration of cardiac computed tomography (CT) to guide LV lead implantation for CRT upgrades. METHODS: Patients undergoing LV lead upgrade underwent ECG-gated cardiac CT dyssynchrony and LV scar assessment. Target American Heart Association segment selection was determined using latest non-scarred mechanically activating segments overlaid onto real-time fluoroscopy with image co-registration to guide optimal LV lead implantation. Hemodynamic validation was performed using a pressure wire in the LV cavity (dP/dtmax) ). RESULTS: 18 patients (male 94%, 55.6% ischemic cardiomyopathy) with RV pacing burden 60.0 ± 43.7% and mean QRS duration 154 ± 30 ms underwent cardiac CT. 10/10 ischemic patients had CT evidence of scar and these segments were excluded as targets. Seventeen out of 18 (94%) patients underwent successful LV lead implantation with delivery to the CT target segment in 15 out of 18 (83%) of patients. Acute hemodynamic response (dP/dtmax ≥ 10%) was superior with LV stimulation in CT target versus nontarget segments (83.3% vs. 25.0%; p = .012). Reverse remodeling at 6 months (LV end-systolic volume improvement ≥15%) occurred in 60% of subjects (4/8 [50.0%] ischemic cardiomyopathy vs. 5/7 [71.4%] nonischemic cardiomyopathy, p = .608). CONCLUSION: Intraprocedural integration of cardiac CT to guide optimal LV lead placement is feasible with superior hemodynamics when pacing in CT target segments and favorable volumetric response rates, despite a high proportion of patients with ischemic cardiomyopathy. Multicentre, randomized controlled studies are needed to evaluate whether intraprocedural integration of cardiac CT is superior to standard care.

Emerging evidence for a mechanistic link between low-frequency oscillation of ventricular repolarization measured from the electrocardiogram T-wave vector and arrhythmia.

Strong recent clinical evidence links the presence of prominent oscillations of ventricular repolarization in the low-frequency range (0.04-0.15 Hz) to the incidence of ventricular arrhythmia and sudden death in post-MI patients and patients with ischaemic and non-ischaemic cardiomyopathy. It has been proposed that these oscillations reflect oscillations of ventricular action potential duration at the sympathetic nerve frequency. Here we review emerging evidence to support that contention and provide insight into possible underlying mechanisms for this association.

Scar shape analysis and simulated electrical instabilities in a non-ischemic dilated cardiomyopathy patient cohort.

This paper presents a morphological analysis of fibrotic scarring in non-ischemic dilated cardiomyopathy, and its relationship to electrical instabilities which underlie reentrant arrhythmias. Two dimensional electrophysiological simulation models were constructed from a set of 699 late gadolinium enhanced cardiac magnetic resonance images originating from 157 patients. Areas of late gadolinium enhancement (LGE) in each image were assigned one of 10 possible microstructures, which modelled the details of fibrotic scarring an order of magnitude below the MRI scan resolution. A simulated programmed electrical stimulation protocol tested each model for the possibility of generating either a transmural block or a transmural reentry. The outcomes of the simulations were compared against morphological LGE features extracted from the images. Models which blocked or reentered, grouped by microstructure, were significantly different from one another in myocardial-LGE interface length, number of components and entropy, but not in relative area and transmurality. With an unknown microstructure, transmurality alone was the best predictor of block, whereas a combination of interface length, transmurality and number of components was the best predictor of reentry in linear discriminant analysis.

High mean entropy calculated from cardiac MRI texture analysis is associated with antitachycardia pacing failure.

BACKGROUND: Antitachycardia pacing (ATP), which may avoid unnecessary implantable cardioverter-defibrillator (ICD) shocks, does not always terminate ventricular arrhythmias (VAs). Mean entropy calculated using cardiac magnetic resonance texture analysis (CMR-TA) has been shown to predict appropriate ICD therapy. We examined whether scar heterogeneity, quantified by mean entropy, is associated with ATP failure and explore potential mechanisms using computer modeling. METHODS: A subanalysis of 114 patients undergoing CMR-TA where the primary endpoint was delivery of appropriate ICD therapy (ATP or shock therapy) was performed. Patients receiving appropriate ICD therapy (n = 33) were dichotomized into "successful ATP" versus "shock therapy" groups. In silico computer modeling was used to explore underlying mechanisms. RESULTS: A total of 16 of 33 (48.5%) patients had successful ATP to terminate VA, and 17 of 33 (51.5%) patients required shock therapy. Mean entropy was significantly higher in the shock versus successful ATP group (6.1 ± 0.5 vs 5.5 ± 0.7, P = .037). Analysis of patients receiving ATP (n = 22) showed significantly higher mean entropy in the six of 22 patients that failed ATP (followed by rescue ICD shock) compared to 16 of 22 that had successful ATP (6.3 ± 0.7 vs 5.5 ± 0.7, P = .048). Computer modeling suggested inability of the paced wavefront in ATP to successfully propagate from the electrode site through patchy fibrosis as a possible mechanism of failed ATP. CONCLUSIONS: Our findings suggest lower scar heterogeneity (mean entropy) is associated with successful ATP, whereas higher scar heterogeneity is associated with more aggressive VAs unresponsive to ATP requiring shock therapy that may be due to inability of the paced wavefront to propagate through scar and terminate the VA circuit.

Leadless left ventricular endocardial pacing in nonresponders to conventional cardiac resynchronization therapy.

BACKGROUND: Endocardial pacing may be beneficial in patients who fail to improve following conventional epicardial cardiac resynchronization therapy (CRT). The potential to pace anywhere inside the left ventricle thus avoiding myocardial scar and targeting the latest activating segments may be particularly important. The WiSE-CRT system (EBR systems, Sunnyvale, CA) reliably produces wireless, endocardial left ventricular (LV) pacing. The purpose of this analysis was to determine whether this system improved symptoms or led to LV remodeling in patients who were nonresponders to conventional CRT. METHOD: An international, multicenter registry of patients who were nonresponders to conventional CRT and underwent implantation with the WiSE-CRT system was collected. RESULTS: Twenty-two patients were included; 20 patients underwent successful implantation with confirmation of endocardial biventricular pacing and in 2 patients, there was a failure of electrode capture. Eighteen patients proceeded to 6-month follow-up; endocardial pacing resulted in a significant reduction in QRS duration compared with intrinsic QRS duration (26.6 ± 24.4 ms; P = .002) and improvement in left ventricular ejection fraction (LVEF) (4.7 ± 7.9%; P = .021). The mean reduction in left ventricular end-diastolic volume was 8.3 ± 42.3 cm3 (P = .458) and left ventricular end-systolic volume (LVESV) was 13.1 ± 44.3 cm3 (P = .271), which were statistically nonsignificant. Overall, 55.6% of patients had improvement in their clinical composite score and 66.7% had a reduction in LVESV ≥15% and/or absolute improvement in LVEF ≥5%. CONCLUSION: Nonresponders to conventional CRT have few remaining treatment options. We have shown in this high-risk patient group that the WiSE-CRT system results in improvement in their clinical composite scores and leads to LV remodeling.

Understanding non-response to cardiac resynchronisation therapy: common problems and potential solutions.

Heart failure is a complex clinical syndrome associated with a significant morbidity and mortality burden. Reductions in left ventricular (LV) function trigger adaptive mechanisms, leading to structural changes within the LV and the potential development of dyssynchronous ventricular activation. This is the substrate targeted during cardiac resynchronisation therapy (CRT); however, around 30-50% of patients do not experience benefit from this treatment. Non-response occurs as a result of pre-implant, peri-implant and post implant factors but the technical constraints of traditional, transvenous epicardial CRT mean they can be challenging to overcome. In an effort to improve response, novel alternative methods of CRT delivery have been developed and of these endocardial pacing, where the LV is stimulated from inside the LV cavity, appears the most promising.

Transvenous lead extraction in patients with cardiac resynchronization therapy devices is not associated with increased 30-day mortality.

AIMS: Transvenous lead extraction (TLE) may be necessary due to system infection/erosion or lead malfunction. Cardiac resynchronization therapy (CRT) patients undergoing TLE may be at greater risk due to increased comorbidities. We examined whether patients with CRT systems undergoing TLE had more comorbidities and higher 30-day mortality than those with non-CRT devices. METHODS AND RESULTS: All TLEs between October 2000 and December 2016 were prospectively collected. During this period 925 TLEs occurred (CRT group 231, non-CRT group 694). Cardiac resynchronization therapy patients were older (68.1 ± 10.8 years vs. 64.3 ± 16.1 years, P = 0.024); more likely male (85.7% vs. 69%, P < 0.001); had lower mean left ventricular ejection fraction (34.1 ± 12.7% vs. 48.3 ± 12.9%, P < 0.001); had higher prevalence of renal impairment (33.8% vs. 13.7%, P < 0.001) and were more likely to have ≥2 comorbidities (84% vs. 40.1%, P < 0.001). Mean lead dwell time was lower in the CRT group (5.6 ± 5.5 years vs. 7.6 ± 7.1 years, P = 0.002). There was no significant difference in all-cause 30-day mortality rates between CRT (3.0%, n = 7) and non-CRT patients (2.0%, n = 14) (P = 0.443). The majority of deaths in both groups were due to sepsis. Univariate and multivariate analysis showed age, renal impairment and sepsis were associated with increased risk of 30-day mortality. Transvenous lead extraction of a CRT system did not predict 30-day mortality. CONCLUSION: Transvenous lead extraction in CRT patients was not associated with increased 30-day mortality when compared with non-CRT patients. Age, renal impairment and sepsis were independent predictors of 30-day mortality. Sepsis was the main cause of 30-day mortality.

Out-of-hospital cardiac arrest due to idiopathic ventricular fibrillation in patients with normal electrocardiograms: results from a multicentre long-term registry.

AIMS: To define the clinical characteristics and long-term clinical outcomes of a large cohort of patients with idiopathic ventricular fibrillation (IVF) and normal 12-lead electrocardiograms (ECGs). METHODS AND RESULTS: Patients with ventricular fibrillation as the presenting rhythm, normal baseline, and follow-up ECGs with no signs of cardiac channelopathy including early repolarization or atrioventricular conduction abnormalities, and without structural heart disease were included in a registry. A total of 245 patients (median age: 38 years; males 59%) were recruited from 25 centres. An implantable cardioverter-defibrillator (ICD) was implanted in 226 patients (92%), while 18 patients (8%) were treated with drug therapy only. Over a median follow-up of 63 months (interquartile range: 25-110 months), 12 patients died (5%); in four of them (1.6%) the lethal event was of cardiac origin. Patients treated with antiarrhythmic drugs only had a higher rate of cardiovascular death compared to patients who received an ICD (16% vs. 0.4%, P = 0.001). Fifty-two patients (21%) experienced an arrhythmic recurrence. Age ≤16 years at the time of the first ventricular arrhythmia was the only predictor of arrhythmic recurrence on multivariable analysis [hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.18-0.92; P = 0.03]. CONCLUSION: Patients with IVF and persistently normal ECGs frequently have arrhythmic recurrences, but a good prognosis when treated with an ICD. Children are a category of IVF patients at higher risk of arrhythmic recurrences.

Prolonged lead dwell time and lead burden predict bailout transfemoral lead extraction.

BACKGROUND: Transvenous lead extraction (TLE) may be performed by superior approach using the original implant vein or via a femoral approach; however, limited comparative data exists. We compare outcomes between femoral versus nonfemoral TLE approaches and determine predictors of bailout transfemoral lead extraction in patients undergoing initial TLE via the original implant vein by a superior approach. METHODS: All consecutive TLEs between October 2000 and March 2018 were prospectively collected (n = 1052). Patients were dichotomized into femoral (n = 118) and nonfemoral (n = 934) groups. RESULTS: Demographics were balanced between femoral vs nonfemoral groups. Patients in the femoral group had significantly higher mean lead dwell times (11.6 ± 9.7 vs 6.6 ± 6.6 years, P < .001), mean number of leads extracted (2.7 ± 1.3 vs 2.0 ± 1.0, P < .001), 30-day procedure related major complications (including deaths) (8.5% vs 1.1%, P < .001) and emergency thoracotomy rates (4.2% vs 0.7%, P = .007). All-cause 30-day mortality rates were similar between groups (3.4% vs 2.0%, P = .315). Prolonged lead dwell time and increased number of leads extracted were predictive of a bailout transfemoral approach at multivariable analysis. CONCLUSION: Femoral approach TLE is associated with increased risk of 30-day procedure related major complications but not 30-day all-cause mortality. Prolonged lead dwell time and increased number of leads extracted are independent predictors for bailout transfemoral lead extraction. Such patients should be considered high risk of major complications and performed by high-volume lead extraction centers with experience in multiple approaches and techniques including experience with transfemoral lead extraction.

Predictors of mortality and outcomes in transvenous lead extraction for systemic and local infection cohorts.

BACKGROUND: Transvenous lead extraction (TLE) may be necessary due to infective and noninfective indications. We aim to identify predictors of 30-day mortality and risk factors between infective versus noninfective groups and systemic versus local infection subgroups. METHODS: A total of 925 TLEs between October 2000 and December 2016 were prospectively collected and dichotomized (infective group n = 505 vs noninfective group n = 420 and systemic infection n = 164 vs local infection n = 341). RESULTS: All-cause major complication including deaths was significantly higher (5.1%, n = 26 vs 1.2%, n = 5, P = 0.001) as well as 30-day mortality (4.0%, n = 20 vs 0.2%, n = 1, P < 0.001) in the infective group compared to the noninfective group. Both subgroups (systemic vs local infection) were balanced for demographics. All-cause major complication including deaths was significantly higher (9.1%, n = 15 vs 3.2%, n = 11, P = 0.008) as well as all-cause 30-day mortality (7.9%, n  = 13 vs 2.1%, n = 7, P = 0.003) in the systemic infection subgroup compared to the local infection subgroup. CONCLUSION: Patients undergoing TLE for infective indications are at greater risk of 30-day all-cause mortality compared to noninfective patients. Patients undergoing TLE for systemic infective indications are at greater risk of 30-day all-cause mortality compared to patients with local infection. Renal impairment, systemic infection, and elevated preprocedure C-reactive protein are independent predictors of 30-day all-cause mortality in patients undergoing TLE for an infective indication.

Variation in activation time during bipolar vs extended bipolar left ventricular pacing.

BACKGROUND: Cardiac resynchronization therapy (CRT) is typically delivered via quadripolar leads that allow stimulation using either true bipolar pacing, where stimulation occurs between two electrodes (BP) on the quadripolar lead, or extended bipole (EBP) left ventricular (LV) pacing, with the quadripolar electrodes and right ventricular coil acting as the cathode and anode, respectively. True bipolar pacing is associated with reductions in mortality and it has been postulated that these differences are the result of enhanced electrical activation. MATERIALS AND METHODS: Patients undergoing a CRT underwent an electrocardiographic imaging study where electrical activation data were recorded while different LV pacing vectors were temporarily programmed. RESULTS: There were no differences in the total electrical activation times or dispersion of electrical activation between biventricular pacing with bipolar or corresponding EBP LV vector configurations (left ventricular total activation time [LVtat] BP 74.70 ± 18.07 vs EBP 72.4 ± 22.64; P = 0.45). When dichotomized according to etiology, no difference was observed in the activation time with either BP or EBP pacing (LVtat BP ischemic cardiomyopathy 72.2 ± 17.4 vs BP dilated cardiomyopathy 79.9 ± 18.9; P = 0.38). CONCLUSIONS: Bipolar pacing alters the mechanical activation sequence of the LV and is associated with reductions in all-cause mortality. It has been postulated these benefits derive from improvements in electromechanical activation of the LV. Our study would suggest that true bipolar pacing does not necessarily result in more favorable activation of the LV or improved electrical resynchronization and other mechanisms should be explored.

The role of transvenous lead extraction in the management of redundant or malfunctioning pacemaker and defibrillator leads post ELECTRa.

Cardiac implantable electronic devices implantation rates have increased over the past decade due to broader indications and an ageing population. Similarly, device and lead complications have also risen. The management of pacemaker/defibrillator leads that are no longer required (redundant) or malfunctioning, can be contentious. There is a need to balance the risk of transvenous lead extraction (TLE) against those of lead abandonment. The recently published European Lead Extraction ConTRolled Registry (ELECTRa) study provides contemporary outcomes for TLE across Europe with important implications for the management of redundant and/or malfunctioning leads. This review article discusses the potential complications for each interventional approach when managing redundant or malfunctioning pacemaker leads.

Electrical latency predicts the optimal left ventricular endocardial pacing site: results from a multicentre international registry.

Aims: The optimal site for biventricular endocardial (BIVENDO) pacing remains undefined. Acute haemodynamic response (AHR) is reproducible marker of left ventricular (LV) contractility, best expressed as the change in the maximum rate of LV pressure (LV-dp/dtmax), from a baseline state. We examined the relationship between factors known to impact LV contractility, whilst delivering BIVENDO pacing at a variety of LV endocardial (LVENDO) locations. Methods and results: We compiled a registry of acute LVENDO pacing studies from five international centres: Johns Hopkins-USA, Bordeaux-France, Eindhoven-The Netherlands, Oxford-United Kingdom, and Guys and St Thomas' NHS Foundation Trust, London-UK. In all, 104 patients incorporating 687 endocardial and 93 epicardial pacing locations were studied. Mean age was 66 ± 11 years, mean left ventricular ejection fraction 24.6 ± 7.7% and mean QRS duration of 163 ± 30 ms. In all, 50% were ischaemic [ischaemic cardiomyopathy (ICM)]. Scarred segments were associated with worse haemodynamics (dp/dtmax; 890 mmHg/s vs. 982 mmHg/s, P < 0.01). Delivering BiVENDO pacing in areas of electrical latency was associated with greater improvements in AHR (P < 0.01). Stimulating late activating tissue (LVLED >50%) achieved greater increases in AHR than non-late activating tissue (LVLED < 50%) (8.6 ± 9.6% vs. 16.1 ± 16.2%, P = 0.002). However, the LVENDO pacing location with the latest Q-LV, was associated with the optimal AHR in just 62% of cases. Conclusions: Identifying viable LVENDO tissue which displays late electrical activation is crucial to identifying the optimal BiVENDO pacing site. Stimulating late activating tissue (LVLED >50%) yields greater improvements in AHR however, the optimal location is frequently not the site of latest activation.

Predictors and outcomes of patients requiring repeat transvenous lead extraction of pacemaker and defibrillator leads.

BACKGROUND: A proportion of patients who undergo an initial lead extraction procedure will require a second, repeat extraction. Data regarding this clinical entity are scarce and neither the predisposing risk factors for, nor outcomes from, these procedures have been described previously. We sought to determine the incidence, risk factors, and outcomes of repeat lead extraction. METHODS: A database of extraction procedures from 2001 to 2015 was analyzed. Repeat extraction procedures were identified and the indication for extraction was dichotomized into infection and lead-related problems. Univariate and multivariate analyses were performed to identify predictors of repeat extraction. RESULTS: 807 extraction procedures were identified in 755 patients of whom 6% required a repeat extraction. At multivariate analysis, only suffering a major complication at the initial extraction procedure (odds ratio [OR] 21.5, 95% confidence interval [CI] 2.69-171.92; P < 0.01), complexity of device (cardiac resynchronization devices/implantable cardioverter defibrillators) (OR 2.58, 95% CI 1.2-5.2; P = 0.01), and age (OR 1.02 per year, 95% CI 1.0-1.4; P  =  0.03) were significant predictors of repeat extraction. When repeat extraction was required for infection there was a significant increase in mortality compared with those who did not require a second procedure (36% vs 23%; P  =  0.02). CONCLUSIONS: Repeat lead extraction is required in 6% of cases. Complexity of device, age at extraction, and a major complication at the first extraction were predictors of repeat extraction. Mortality is significantly increased where the repeat procedure is for infection. Clinicians should alert patients to the potential need for further extraction and the increased risks of repeat procedures when indicated for infection.

Chronic Right Ventricular Pacing in the Heart Failure Population.

PURPOSE OF REVIEW: We review the trials that have demonstrated potentially harmful effects from right ventricular (RV) apical pacing as well as reviewing the evidence of alternative RV pacing sites and cardiac resynchronization therapy (CRT) for patients who have heart failure and atrioventricular (AV) block. RECENT FINDINGS: The role of CRT in patients with AV block and impaired left ventricular function remains an important consideration. The BLOCK HF trial demonstrated better outcomes with CRT pacing over RV pacing in patients with left ventricular systolic dysfunction (LVSD) and AV block who were expected to have a high RV pacing burden, but failed to demonstrate a mortality benefit. CRT seems to have a beneficial effect on left ventricular reverse remodeling, systolic function, and clinical outcomes in patients with New York Heart Association (NYHA) functional class I-III heart failure, moderate to severe LVSD, and AV block compared to RV pacing. However, it is less clear whether there is a similar benefit from CRT in patients with a high percentage of RV pacing who have normal or mild LVSD in the treatment of AV block.

The Emerging Role of Cardiac Magnetic Resonance Imaging in the Evaluation of Patients with HFpEF.

PURPOSE OF REVIEW: To give an update on the emerging role of cardiac magnetic resonance imaging in the evaluation of patients with heart failure with preserved ejection fraction (HFpEF). This is important as the diagnosis of HFpEF remains challenging and cardiac imaging is pivotal in establishing the function of the heart and whether there is evidence of structural heart disease or diastolic dysfunction. Echocardiography is widely available, although the gold standard in quantifying heart function is cardiac magnetic resonance (CMR) imaging. RECENT FINDINGS: This review includes the recently updated 2016 European Society of Cardiology guidelines on diagnosing HFpEF that define the central role of imaging in identifying patients with HFpEF. Moreover, it includes the pathophysiology in HFpEF, how CMR works, and details current CMR techniques used to assess structural heart disease and diastolic function. Furthermore, it highlights promising research techniques that over the next few years may become more used in identifying these patients. CMR has an emerging role in establishing the diagnosis of HFpEF by measuring the left ventricular ejection fraction (LVEF) and evidence of structural heart disease and diastolic dysfunction.

Substrate-dependent risk stratification for implantable cardioverter defibrillator therapies using cardiac magnetic resonance imaging: The importance of T1 mapping in nonischemic patients.

INTRODUCTION: The role of implantable cardioverter defibrillators (ICDs) in nonischemic cardiomyopathy is unclear and better risk-stratification is required. We sought to determine if T1 mapping predicts appropriate defibrillator therapy in patients with nonischemic cardiomyopathy. We studied a mixed cohort of ischemic and nonischemic patients to determine whether different cardiac magnetic resonance (CMR) applications (T1 mapping, late gadolinium enhancement, and Grayzone) were selectively predictive of therapies for the different arrhythmic substrates. METHODS AND RESULTS: We undertook a prospective longitudinal study of consecutive patients receiving defibrillators in a tertiary cardiac center. Participants underwent CMR myocardial tissue characterization using T1 mapping and conventional CMR scar assessment before device implantation. QRS duration and fragmentation on the surface electrocardiogram were also assessed. The primary endpoint was appropriate defibrillator therapy. One-hundred thirty patients were followed up for a median of 31 months (IQR ± 9 months). In nonischemic patients, T1_native was the sole predictor of the primary endpoint (hazard ratio [HR] 1.12 per 10 millisecond increment in value [95% confidence interval [CI] 1.04-1.21; P ≤ 0.01]). In ischemic patients, Grayzone_2SD-3SD was the strongest predictor of appropriate therapy (HR 1.34 per 1% left ventricular increment in value [95% CI 1.03-1.76; P = 0.03]). QRS fragmentation correlated well with myocardial scar core (receiver operating characteristic area under the curve [ROC AUC] 0.64; P = 0.02) but poorly with T1_native (ROC AUC 0.4) and did not predict appropriate therapy. CONCLUSIONS: In the medium-long term, T1_native mapping was the only independent predictor of therapy in nonischemic patients, whereas Grayzone was a better predictor in ischemic patients. These findings suggest a potential role for T1_native mapping in the selection of patients for ICDs in a nonischemic population.