Ischaemia with no obstructive coronary arteries: a review with focus on the Asian population.

ABSTRACT: Ischaemia with no obstructive coronary arteries (INOCA) has been a diagnostic and therapeutic challenge for decades. Several studies have demonstrated that INOCA is associated with an increased risk of death, adverse cardiovascular events, poor quality of life and high healthcare cost. Although there is increasing recognition of this entity in the Western population, in the Asian population, INOCA remains elusive and its prevalence uncertain. Despite its prognostic significance, diagnosis of INOCA is often delayed. In this review, we identified the multiple barriers to its diagnosis and management, and proposed strategies to overcome them.

Prognostic benefits of His-Purkinje capture in physiological pacemakers for bradycardia.

INTRODUCTION: Clinical outcomes of long-term ventricular septal pacing (VSP) without His-Purkinje capture remain unknown. This study evaluated the differences in clinical outcomes between conduction system pacing (CSP), VSP, and right ventricular pacing (RVP). METHODS: Consecutive patients with bradycardia indicated for pacing from 2016 to 2022 were prospectively followed for the clinical endpoints of heart failure (HF)-hospitalizations and all-cause mortality at 2 years. VSP was defined as septal pacing due to unsuccessful CSP implant or successful CSP followed by loss of His-Purkinje capture within 90 days. RESULTS: Among 1016 patients (age 73.9 ± 11.2 years, 47% female, 48% atrioventricular block), 612 received RVP, 335 received CSP and 69 received VSP. Paced QRS duration was similar between VSP and RVP, but both significantly longer than CSP (p < .05). HF-hospitalizations occurred in 130 (13%) patients (CSP 7% vs. RVP 16% vs. VSP 13%, p = .001), and all-cause mortality in 143 (14%) patients (CSP 7% vs. RVP 19% vs. VSP 9%, p < .001). The association of pacing modality with clinical events was limited to those with ventricular pacing (Vp) > 20% (pinteraction < .05). Adjusting for clinical risk factors among patients with Vp > 20%, VSP (adjusted hazard ratio [AHR]: 4.74, 95% confidence interval [CI]: 1.57-14.36) and RVP (AHR: 3.08, 95% CI: 1.44-6.60) were associated with increased hazard of HF-hospitalizations, and RVP (2.52, 95% CI: 1.19-5.35) with increased mortality, compared to CSP. Clinical endpoints did not differ between VSP and RVP with Vp > 20%, or amongst groups with Vp < 20%. CONCLUSION: Conduction system capture is associated with improved clinical outcomes. CSP should be preferred over VSP or RVP during pacing for bradycardia.

Platform for the interdisciplinary study of cardiovascular, metabolic and neurovascular diseases (PICMAN) protocol.

Through extensive multisystem phenotyping, the central aim of Project PICMAN is to correlate metabolic flexibility to measures of cardiometabolic health, including myocardial diastolic dysfunction, coronary and cerebral atherosclerosis, body fat distribution and severity of non-alcoholic fatty liver disease. This cohort will form the basis of larger interventional trials targeting metabolic inflexibility in the prevention of cardiovascular disease. Participants aged 21-72 years with no prior manifest atherosclerotic cardiovascular disease (ASCVD) are being recruited from a preventive cardiology clinic and an existing cohort of non-alcoholic fatty liver disease (NAFLD) in an academic medical centre. A total of 120 patients will be recruited in the pilot phase of this study and followed up for 5 years. Those with 10-year ASCVD risk ≥ 5% as per the QRISK3 calculator are eligible. Those with established diabetes mellitus are excluded. Participants recruited undergo a detailed assessment of health behaviours and physical measurements. Participants also undergo a series of multimodality clinical phenotyping comprising cardiac tests, vascular assessments, metabolic tests, liver and neurovascular testing. Blood samples are also being collected and banked for plasma biomarkers, 'multi-omics analyses' and for generation of induced pluripotent stem cells (iPSC). Extensive evidence points to metabolic dysregulation as an early precursor of cardiovascular disease, particularly in Asia. We hypothesise that quantifiable metabolic inflexibility may be representative of an individual in his/her silent, but high-risk progression towards insulin resistance, diabetes and cardiovascular disease. The platform for interdisciplinary cardiovascular-metabolic-neurovascular diseases (PICMAN) is a pilot, prospective, multi-ethnic cohort study.

Comparison of Pacing Performance and Clinical Outcomes Between Left Bundle Branch and His Bundle Pacing.

BACKGROUND: Left bundle branch (LBBP) and His-bundle pacing (HBP) provide physiological ventricular activation. OBJECTIVES: This study investigated differences in feasibility, device performance, and clinical outcomes between LBBP and HBP. METHODS: Consecutive patients with LBBP and HBP from 2018 to 2021 in 2 centers were prospectively studied. The primary endpoint was optimal device performance during follow-up, defined as the presence of pacing thresholds <2.5 V, R-wave amplitude ≥5 V, and absence of conduction system pacing (CSP)-related complications. The secondary endpoint was the composite of heart failure hospitalizations or all-cause mortality. RESULTS: Among 338 patients, 282 underwent successful CSP (119 HBP, 163 LBBP). Success rates, CSP-related complications, and need for reoperations did not differ between LBBP and HBP (P > 0.05). Pacing thresholds were lower, whereas R-wave amplitudes and lead impedance were higher in LBBP (P < 0.05). The primary endpoint was more frequent in LBBP than HBP (79% vs 34%; P < 0.001), with LBBP independently associated with 9-fold increased odds of optimal device performance (adjusted OR: 9.31; 95% CI: 5.14-16.86). LBBP was less likely to have increased pacing thresholds by >1 V (1% vs 19% HBP, P < 0.001). The secondary outcome was less frequent in LBBP than HBP (9% vs 24%, P = 0.001), with LBBP trending towards higher event-free survival (HR: 0.62; 95% CI: 0.31-1.23). The secondary outcome was independent of pacing burden or pacing indication. CONCLUSIONS: Despite similar feasibility and safety profiles, LBBP confers additional benefits in pacing performance and reliability, shows trends towards improved survival compared to HBP, and should be the preferred first-line CSP modality of choice.

Conduction system versus biventricular pacing in heart failure with non-left bundle branch block.

INTRODUCTION: The benefits of cardiac resynchronization therapy (CRT) with biventricular pacing (BiV) is significantly lower when applied to heart failure (HF) patients with non-left bundle branch block (LBBB) conduction delay. We investigated clinical outcomes of conduction system pacing (CSP) for CRT in non-LBBB HF. METHODS: Consecutive HF patients with non-LBBB conduction delay undergoing CSP were propensity matched for age, sex, HF-etiology, and atrial fibrillation (AF) in a 1:1 ratio to BiV from a prospective registry of CRT recipients. Echocardiographic response was defined as an increase in left ventricular ejection fraction (LVEF) by ≥10%. The primary outcome was the composite of HF-hospitalizations or all-cause mortality. RESULTS: A total of 96 patients were recruited (mean age 70 ± 11years, 22% female, 68% ischemic HF and 49% AF). Significant reductions in QRS duration and LV dimensions were seen only after CSP, while LVEF improved significantly in both groups (p < 0.05). Echocardiographic response occurred more frequently in CSP than BiV (51% vs. 21%, p < 0.01), with CSP independently associated with four-fold increased odds (adjusted odds ratio 4.08, 95% confidence interval [CI] 1.34-12.41). The primary outcome occurred more frequently in BiV than CSP (69% vs. 27%, p < 0.001), with CSP independently associated with 58% risk reduction (adjusted hazard ratio [AHR] 0.42, 95% CI 0.21-0.84, p = 0.01), driven by reduced all-cause mortality (AHR 0.22, 95% CI 0.07-0.68, p < 0.01), and a trend toward reduced HF-hospitalization (AHR 0.51, 95% CI 0.21-1.21, p = 0.12). CONCLUSIONS: CSP provided greater electrical synchrony, reverse remodeling, improved cardiac function and survival compared to BiV in non-LBBB, and may be the preferred CRT strategy for non-LBBB HF.

Clinical Outcomes in Conduction System Pacing Compared to Right Ventricular Pacing in Bradycardia.

BACKGROUND: Conduction system pacing (CSP) provides more physiological ventricular activation than right ventricular pacing (RVP). OBJECTIVES: This study evaluated the differences in clinical outcomes in patients receiving CSP and RVP. METHODS: Consecutive patients with pacemakers implanted for bradycardia from 2016 to 2021 in 2 centers were prospectively followed for the primary composite outcome of heart failure (HF) hospitalizations, upgrade to biventricular pacing, or all-cause mortality, stratified by ventricular pacing burden (Vp) . RESULTS: Among 860 patients (mean age 74 ± 11 years, 48% female, 48% atrioventricular block), 628 received RVP and 231 received CSP (95 His-bundle pacing, 136 left bundle branch pacing). The primary outcome occurred in 217 (25%) patients, more commonly in patients with RVP than CSP (30% vs 13%, P < 0.001). In multivariable analyses, CSP was independently associated with 47% reduction of the primary outcome (adjusted hazard ratio [AHR]: 0.53; 95% CI: 0.29-0.97; P = 0.04) and HF hospitalization alone (AHR: 0.40; 95% CI: 0.17-0.95; P = 0.04), among only patients with Vp >20%. The incidence of the primary outcome was highest among RVP with Vp >20% and lowest in CSP with Vp >20% (35% vs 10%, P < 0.001). Compared with RVP with Vp >20%, both CSP with Vp >20% (AHR: 0.51; 95% CI: 0.28-0.91; P = 0.02) and all patients with Vp ≤20% (AHR: 0.73; 95% CI: 0.54-0.99; P = 0.04) were independently associated with reduced primary outcome, driven primarily by reductions in HF hospitalizations (P < 0.05). Event-free survival was similar between CSP with Vp >20% and those needing ≤20% Vp. CONCLUSIONS: CSP significantly reduced adverse clinical outcomes for bradycardic patients requiring ventricular pacing and should be the preferred pacing modality of choice.

Combined balloon guide catheter, aspiration catheter, and stent retriever technique versus balloon guide catheter and stent retriever alone technique: a systematic review and meta-analysis.

BACKGROUND: The use of a combination of balloon guide catheter (BGC), aspiration catheter, and stent retriever in acute ischemic stroke thrombectomy has not been shown to be better than a stent retriever and BGC alone, but this may be due to a lack of power in these studies. We therefore performed a meta-analysis on this subject. METHODS: A systematic literature search was performed on PubMed, Scopus, Embase/Ovid, and the Cochrane Library from inception to October 20, 2021. Our primary outcomes were the rate of successful final reperfusion (Treatment in Cerebral Ischemia (TICI) 2c-3) and first pass effect (FPE, defined as TICI 2c-3 in a single pass). Secondary outcomes were 3 month functional independence (modified Rankin Scale score of 0-2), mortality, procedural complications, embolic complications, and symptomatic intracranial hemorrhage (SICH). A meta-analysis was performed using RevMan 5,4, and heterogeneity was assessed using the I2 test. RESULTS: Of 1629 studies identified, five articles with 2091 patients were included. For the primary outcomes, FPE (44.9% vs 45.4%, OR 1.04 (95% CI 0.90 to 1.22), I2=57%) or final successful reperfusion (64.5% vs 68.6%, OR 0.98 (95% CI 0.81% to 1.20%), I2=85%) was similar between the combination technique and stent retriever only groups. However, the combination technique had significantly less rescue treatment (18.8% vs 26.9%; OR 0.70 (95% CI 0.54 to 0.91), I2=0%). This did not translate into significant differences in secondary outcomes in functional outcomes, mortality, emboli, complications, or SICH. CONCLUSION: There was no significant difference in successful reperfusion and FPE between the combined techniques and the stent retriever and BGC alone groups. Neither was there any difference in functional outcomes, complications, or mortality.

Percutaneous coronary intervention in patients aged 80 years old and above: a systematic review and meta-analysis.

Background: Ischaemic heart disease remains the main cause of death in the world. With increasing age, frailty and comorbidities, senior patients aged 80 years old and above who undergo percutaneous coronary intervention (PCI) are at higher risk of mortality and other complications. Aims: We aimed to examine the overall outcomes for this group of patients. Methods: Four databases (PUBMED, EMBASE, SCOPUS and CENTRAL) were searched. Studies with patients aged 80 years old and above who underwent PCI for all indications were included. Pooled outcomes of all-cause death, cardiac death, in-hospital death, subsequent stroke/transient ischaemic attack (TIA), subsequent myocardial infarction (MI), subsequent congestive cardiac failure (CCF), and overall major adverse cardiac events (MACE) were obtained for meta-analysis. Results: From 2,566,004 patients, the pooled cumulative incidence of death was 19.22%, cardiac death was 7.78%, in-hospital death was 7.16%, subsequent stroke/TIA was 1.54%, subsequent MI was 3.58%, subsequent CCF was 4.74%, and MACE was 17.51%. The mortality rate of all patients was high when followed up for 3 years (33.27%). ST-elevation myocardial infarction patients had more outcomes of in-hospital death (14.24% vs 4.89%), stroke/TIA (1.93% vs 0.12%), MI (3.68 vs 1.55%) and 1-year mortality (26.16% vs 13.62%), when compared to non-ST-elevation myocardial infarction patients. Conclusions: There was a high mortality rate at 1 year and 3 years post-PCI in the overall population of senior patients aged 80 years old and above, regardless of indication. This necessitates further studies to explore the implications of these observations.

Symptomatic intracerebral hemorrhage after non-emergency percutaneous coronary intervention: Incidence, risk factors, and association with cardiovascular outcomes.

Objective: To investigate the incidence, risk factors, and association with cardiovascular outcomes of patients who developed symptomatic intracerebral hemorrhage (ICH) after non-emergency percutaneous coronary intervention (PCI). Methods: We conducted a single-institution retrospective study of patients who developed symptomatic ICH after non-emergency PCI. To identify associations between clinical variables and outcomes, Cox-proportional hazards regression models were constructed. Outcomes analyzed include (1) all-cause mortality, (2) acute ischemic stroke (AIS) or transient ischemic attack (TIA), and (3) major adverse cardiovascular events (MACE). Results: A total of 1,732 patients were included in the analysis. The mean (±SD) age was 61.1 (±11.3) years, and 1,396 patients (80.6%) were male. The cumulative incidence of symptomatic ICH after non-emergency PCI was 1.3% (22 patients). Age, chronic kidney disease, and prior coronary artery bypass graft surgery were independently associated with a higher risk of ICH after PCI, while hyperlipidemia was independently associated with a lower risk of ICH after PCI. ICH after PCI was independently associated with a higher risk of all-cause mortality and AIS or TIA after PCI. Conclusion: Patients who are older, who have chronic kidney disease, and who have had prior coronary artery bypass graft surgery should be monitored for symptomatic ICH after non-emergency PCI.

Use of extendable helix leads for conduction system pacing: Differences in lead handling and performance lead design impacts conduction system pacing.

INTRODUCTION: Pacing leads with extendable-retractable helix (EHL) are alternatives to fixed-helix leads (FHL) for conduction system pacing (CSP), but data on handling characteristics are limited. This study evaluated a dual-center experience of lead handling and performance during CSP. METHODS AND RESULTS: Consecutive patients with His-bundle pacing (HBP) or left bundle branch pacing (LBBP) were evaluated for the primary outcome of lead failure, defined as structural damage to the lead necessitating lead replacement. Differences in pacing characteristics were compared. Among 280 patients (mean age 74 ± 11 years, 44% male, 50% LBBP), 246 (88%) received FHL and 34 (12%) received EHL. Of 299 leads used, lead failure occurred more frequently among patients with EHL than FHL (29% vs. 2%, p < .001), regardless of CSP modality. Majority of damaged leads (89%) in the form of helix deformation were successfully removed, with failure occurring in only two patients, both EHL, leading to helix fracture and retention within the septal myocardium. EHL, compared to FHL, was associated with 25-fold increased odds of lead failure (odds ratio: 25.21, 95% confidence interval: 7.35-86.51), and persisted after adjustment in turn for age, pacing modality and indication. CSP implant success rates did not differ by lead design (FHL 80% vs. EHL 71%, p = .18), with similar pacing thresholds at implant and follow-up. CONCLUSION: Helix deformation and fracture were more frequent with EHL in CSP despite similar implant success. These findings have significant implications for lead selection during CSP and raises concerns about the long-term extractability of EHL in CSP.

Clinical Characteristics and Long-Term Outcomes of Patients With Differing Haemoglobin Levels Undergoing Semi-Urgent and Elective Percutaneous Coronary Intervention in an Asian Population.

Introduction: This study aimed to investigate the impact of anaemia on long-term clinical outcomes in patients who underwent semi-urgent and elective percutaneous coronary intervention (PCI) in an Asian population. Although the effects of anaemia on outcomes in Asian patients are well studied for acute coronary syndrome, its impact on Asian patients undergoing semi-urgent and elective PCI is unclear. Methods: This was a retrospective cohort study of patients who underwent semi-urgent and elective PCI from January 1, 2014, to December 31, 2015, at a tertiary academic centre. A total of 1,685 patients were included. They were stratified into three groups: normal (≥12 g/dL), intermediate (10-11.9 g/dL), and low (<10 g/dL) haemoglobin levels. Demographics, risk factors, and end-points including the 5-point major adverse cardiac and cerebrovascular events (MACCE) (all-cause death, subsequent stroke, myocardial infarction, congestive cardiac failure, and target lesion revascularisation), cardiovascular death, and bleeding events were analysed. Results: Patients in intermediate and low haemoglobin level groups were older with more comorbidities. Compared to the normal haemoglobin level group, low haemoglobin level group patients were associated with an increased risk of composite endpoints of all-cause death, subsequent stroke, myocardial infarction, congestive cardiac failure, and target lesion revascularisation [adjusted hazard ratio (aHR) 1.89, 95% confidence interval (CI):1.22, 2.92; p = 0.004]. This was driven by the increased risk of target lesions revascularisation observed in the low haemoglobin level group compared to the normal haemoglobin level group (aHR 17.74, 95% CI: 1.74, 180.80; p = 0.015). The patients in the low haemoglobin level group were also associated with a higher risk of bleeding events compared to the normal haemoglobin level group (aHR 7.18, 95% CI: 1.13, 45.40; p = 0.036). Conclusion: In our Asian cohort, patients with anaemia undergoing PCI were associated with a higher comorbid burden. Despite adjustments for comorbidities, these patients had higher mortality and worse cardiovascular outcomes following contemporary PCI.

Comparison of the Efficacy and Safety of Non-vitamin K Antagonist Oral Anticoagulants with Warfarin in Atrial Fibrillation Patients with a History of Bleeding: A Systematic Review and Meta-Analysis.

BACKGROUND: Patients with atrial fibrillation (AF) require oral anticoagulation to prevent ischemic stroke. However, oral anticoagulation may cause bleeding, and patients with AF and a history of bleeding were excluded from pivotal trials comparing non-vitamin K antagonist oral anticoagulants (NOACs) and warfarin. We therefore aimed to assess the efficacy and safety of NOACs compared with warfarin in patients with AF and a history of bleeding. METHODS: We conducted a systematic review of retrospective studies and clinical trials using the PubMed, EMBASE, SCOPUS, Cochrane Library, and Web of Science databases to May 2021. RESULTS: Overall, 56,697 patients from six studies were included. NOACs significantly reduced the risk of ischemic stroke (hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.59-0.91; p = 0.005), fatal ischemic stroke (HR 0.49, 95% CI 0.39-0.61; p < 0.001), all-cause mortality (HR 0.70, 95% CI 0.50-0.98; p = 0.04), major bleeding events (HR 0.75, 95% CI 0.67-0.84; p < 0.001), intracranial hemorrhage (ICH; HR 0.63, 95% CI 0.48-0.82; p < 0.001), fatal ICH (HR 0.33, 95% CI 0.20-0.56, p < 0.001), and gastrointestinal bleeding (HR 0.83, 95% CI 0.72-0.96; p = 0.01). CONCLUSIONS: NOACs showed better efficacy and safety profile compared with warfarin in patients with AF and a history of bleeding. Randomized controlled trials are warranted to validate these findings.

Impact of the COVID-19 pandemic on hospital admissions of nursing home residents.

OBJECTIVE: The coronavirus disease 2019 (COVID-19) pandemic has impacted nursing home care and activities in profound ways. We sought to understand whether the COVID-19 pandemic had any impact on hospital admissions of nursing home residents. METHODS: A retrospective analysis of hospital admissions of nursing home residents to a tertiary general hospital in Singapore during the COVID-19 pandemic in 2020 was conducted and compared to admissions in the preceding year. Patients' demographics, length of stay, primary diagnosis on admission, death and causes of death were recorded. RESULTS: Our study found reduced number of hospital admissions of nursing home residents to a tertiary hospital in Singapore. There was a significant decrease in pneumonia (p < 0.001) and fall (p = 0.001) as a primary diagnosis on admission and a decrease in pneumonia as the cause of death (p < 0.001) for nursing home residents admitted to hospital during the COVID-19 pandemic. CONCLUSIONS: This suggests that measures implemented during the pandemic may have impacted outcomes of nursing home residents. Further study is warranted to lead to practise changing outcomes for nursing home settings.

Impact of geriatric syndromes on anticoagulation prescription in older adults with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is common in older adults. CHA2DS2-VASC (congestive heart failure, hypertension, age ≥75 (doubled), diabetes mellitus, prior stroke or transient ischemic attack (doubled), vascular disease, age 65-74, female) and HASBLED(Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly) are the most established risk stratification tools in assessing suitability for anticoagulation in AF. However, there are no established screening tools for geriatric syndromes on anticoagulation risks in older adults. OBJECTIVE: This study examined the association of anticoagulation prescription with geriatric syndromes. METHODS: Older adults 65 years and above admitted to a tertiary hospital with atrial fibrillation and CHA2DS2-VASC score ≥ 2. Data on demographics, function (modified Barthel's Index (MBI)), cognition (mini-cog), frailty (Edmonton Frail Scale (EFS) and FRAIL), geriatric syndromes (EFS), sarcopenia (SARC-F), HASBLED and CHA2DS2-VASC were collected. RESULTS: 150 patients aged 65 and above (mean age 79.4 ± 7.1 years) with AF were recruited. 101 (67%) participants were anticoagulated, in univariate analysis comparing those who were anticoagulated with those who were not, age (OR 0.94; 95% CI 0.89-0.99), chronic kidney disease (OR 0.39; 95% CI 0.19-0.80), frailty (OR 0.77; 95% CI 0.60-0.98) and functional status by Barthel's Index (OR 0.75; 95% CI 0.57-0.97) were significantly associated with anticoagulation prescription. In multivariate analysis, age (OR 0.93; 95% CI 0.88-0.99) and CKD (OR 0.35; 95% CI 0.16-0.76) remained significant. There was no significant difference in CHA2DS2-VASC, HASBLED, MBI or falls between the groups. CONCLUSIONS: Age and CKD were significantly associated with anticoagulation prescription in patients with AF. Further studies on the impact of geriatric syndromes on anticoagulation prescription and outcomes in older adults are needed with specific guidelines for patients with geriatric syndromes and AF.

Adopting permanent His bundle pacing: learning curves and medium-term outcomes.

AIMS: This study aims to determine procedural characteristics, acute success rates, and medium-term outcomes of consecutive patients undergoing His bundle pacing (HBP); and learning curves of experienced electrophysiologists adopting HBP. METHODS AND RESULTS: Consecutive HBP patients at three hospitals were recruited. Clinical characteristics, acute procedural details, and medium-term outcomes were extracted from electronic medical records. Two hundred and thirty-three patients [mean age 74.6 ± 10.1 years, 48% female, 68% narrow QRS, 71% normal left ventricular ejection fraction (LVEF), 55.8% atrioventricular block] underwent HBP. Acute procedural success was 81.1% (mean procedural and fluoroscopic times of 105.5 ± 36.5 and 13.8 ± 9.3 min). Broad QRS was associated with lower HBP success (odds ratio 0.39, P = 0.02). Fluoroscopic and procedural times decreased and plateaued after 30-40 cases per operator. Implant HBP threshold was 1.3 ± 0.7 V at 1.0 ± 0.2 ms and R wave was 5.0 ± 3.9 mV. During follow-up, loss of HBP occurred in a further 12.4% and 11.3% of patients experienced a ≥1 V increase in HBP threshold. Five (2.6%) patients required HBP revision for pacing difficulties. About 8.6% of patients had a >50% decrease in R wave but lead revision for sensing issues was not necessary. On an intention to treat basis, 56.7% of patients in whom HBP was attempted had persisting HBP capture and thresholds of <2 V. CONCLUSION: Physicians adopting HBP should be cognizant of the learning curve and preferentially select non-dependent patients with normal QRS and LVEF, to minimize risk of lead revision. Further rises in HBP threshold may increase battery drain and need for reoperations, important considerations when choosing HBP for cardiac resynchronization therapy.