Chronic right ventricular apical pacing: adverse effects and current therapeutic strategies to minimize them

Conduction System Pacing: Hope, Challenges, and the Journey Forward

PURPOSE OF THE REVIEW

Cardiac pacing has evolved in recent years currently culminating in the specific stimulation of the cardiac conduction system (conduction system pacing, CSP). This review aims to provide a comprehensive overview of the available literature on CSP, focusing on a critical classification of studies comparing CSP with standard treatment in the two fields of pacing for bradycardia and cardiac resynchronization therapy in patients with heart failure. The article will also elaborate specific benefits and limitations associated with CSP modalities of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP).

RECENT FINDINGS

Based on a growing number of observational studies for different indications of pacing therapy, both CSP modalities investigated are advantageous over standard treatment in terms of narrowing the paced QRS complex and preserving or improving left ventricular systolic function. Less consistent evidence exists with regard to the improvement of heart failure-related rehospitalization rates or mortality, and effect sizes vary between HBP and LBBAP. LBBAP is superior over HBP in terms of lead measurements and procedural duration. With regard to all reported outcomes, evidence from large scale randomized controlled clinical trials (RCT) is still scarce. CSP has the potential to sustainably improve patient care in cardiac pacing therapy if patients are appropriately selected and limitations are considered. With this review, we offer not only a summary of existing data, but also an outlook on probable future developments in the field, as well as a detailed summary of upcoming RCTs that provide insights into how the journey of CSP continues.

A case of cardiogenic shock due to ventricular dyssynchrony resolved by atrial pacing

We present a case of a man with ischemic cardiomyopathy and single chamber implantable cardioverter-defibrillator who developed sinus arrest creating sudden dependence on right ventricular (RV) pacing. He presented with cardiogenic shock secondary to abrupt onset ventricular dyssynchrony from RV pacing, which required emergent stabilization and completely resolved with atrial pacing.

Learning objective

To establish a basic understanding of cardiogenic shock management. To reinforce the adverse effects associated with right ventricular pacing.

The degree of permanent pacemaker dependence and clinical outcomes following transcatheter aortic valve implantation: implications for procedural technique

Aims

Conduction abnormalities necessitating permanent pacemaker (PPM) implantation remain the most frequent complication post-transcatheter aortic valve implantation (TAVI), yet reliance on PPM function varies. We evaluated the association of right-ventricular (RV)-stimulation rate post-TAVI with 1-year major adverse cardiovascular events (MACE) (all-cause mortality and heart failure hospitalization).

Methods and results

This retrospective cohort study of patients undergoing TAVI in two high-volume centers included patients with existing PPM pre-TAVI or new PPM post-TAVI. There was a bimodal distribution of RV-stimulation rates stratifying patients into two groups of either low [≤10%: 1.0 (0.0, 3.6)] or high [>10%: 96.0 (54.0, 99.9)] RV-stimulation rate post-TAVI. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated comparing MACE in patients with high vs. low RV-stimulation rates post-TAVI. Of 4659 patients, 408 patients (8.6%) had an existing PPM pre-TAVI and 361 patients (7.7%) underwent PPM implantation post-TAVI. Mean age was 82.3 ± 8.1 years, 39% were women. A high RV-stimulation rate (>10%) development post-TAVI is associated with a two-fold increased risk for MACE [1.97 (1.20, 3.25), P = 0.008]. Valve implantation depth was an independent predictor of high RV-stimulation rate [odds ratio (95% CI): 1.58 (1.21, 2.06), P=<0.001] and itself associated with MACE [1.27 (1.00, 1.59), P = 0.047].

Conclusion

Greater RV-stimulation rates post-TAVI correlate with increased 1-year MACE in patients with new PPM post-TAVI or in those with existing PPM but low RV-stimulation rates pre-TAVI. A shallower valve implantation depth reduces the risk of greater RV-stimulation rates post-TAVI, correlating with improved patient outcomes. These data highlight the importance of a meticulous implant technique even in TAVI recipients with pre-existing PPMs.

Atrioventricular node ablation and pacing for atrial tachyarrhythmias: A meta-analysis of postoperative outcomes

BACKGROUND

Atrioventricular node ablation (AVNA) and pacemaker (PM) is performed in symptomatic atrial fibrillation (AF) unresponsive to medical treatment and percutaneous ablation. This meta-analysis evaluated results after AVNA and PM.

METHODS

Primary and secondary endpoints were early/late overall/cardiac-related mortality and early/late postoperative complications. Meta-regression explored mortality and preoperative characteristics relation.

RESULTS

We selected 93 studies with 11,340 patients: 9105 right ventricular (RV)-PM, and 2235 biventricular PM (cardiac resynchronization therapy, CRT). Malignant arrhythmia (2.5%), heart failure (2.4%), and lead dislodgement (2.0%) were most common periprocedural complications. Pooled estimated 30-day mortality was 1.08% (95%CI:0.65-1.77). At 19.9 months median follow-up (IQR: 10.3-34 months), rehospitalization (0.79%/month) and heart failure (0.48%/month) were the most frequent complications. Overall mortality incidence rate (IR) was 0.43%/month (95%CI:0.36-0.51), and cardiac death IR 0.27%/month (95%CI:0.22-0.32). No mortality determinants emerged in the AVNA CRT subgroup. AVNA RV-PM subgroup univariable meta-regression showed inverse relationship between age, ejection fraction (EF), and late cardiac death (Beta = -0.0709 ± 0.0272; p = 0.0092 and Beta = -0.0833 ± 0.0249; p = 0.0008). Coronary artery disease (CAD) was directly associated to follow-up overall/cardiac mortality at univariable (Beta = 0.0550 ± 0.0136, p < 0.0001; Beta = 0.0540 ± 0.0130, p < 0.0001) and multivariable (Beta = 0.0460 ± 0.0189, p = 0.152; Beta = 0.0378 ± 0.0192, p = 0.0491) meta-regression.

CONCLUSIONS

Solid long-term evidence supporting AVNA and pace is lacking. Younger patients with reduced LVEF% have increased follow-up cardiac mortality after AVNA RV and may require CRT. Alternative strategies to maintain sinus rhythm and ventricular synchronism should be compared to AVNA to support future treatment strategies.

Comparison of the Acute Effects of Different Pacing Sites on Cardiac Synchrony and Contraction Using Speckle-Tracking Echocardiography

Background: Cardiac pacing in patients with bradyarrhythmia may employ variable pacing sites, which may have different effects on cardiac function. Left bundle branch pacing (LBBP) is a new physiological pacing modality, and the acute outcomes on cardiac mechanical synchrony during LBBP remain uncertain. We evaluated the acute effects of four pacing sites on cardiac synchrony and contraction using speckle-tracking echocardiography, and comparisons among four different pacing sites were rare.

Methods: We enrolled 21 patients with atrioventricular block or sick sinus syndrome who each sequentially underwent acute pacing protocols, including right ventricular apical pacing (RVAP), right ventricular outflow tract pacing (RVOP), His bundle pacing (HBP), and left bundle branch pacing (LBBP). Electrocardiograms and echocardiograms were recorded at baseline and during pacing. The interventricular mechanical delay (IVMD), the standard deviation of the times to longitudinal peak strain during 17 segments (PSD), and the Yu index were used to evaluate ventricular mechanical synchrony. Layer-specific strain was computed using two-dimensional speckle tracking technique to provide in-depth details about ventricular synchrony and function.

Results: Left ventricular ejection fraction (LVEF) and tricuspid annulus plane systolic excursion (TAPSE) were significantly decreased during RVAP and RVOP but were not significantly different during HBP and LBBP compared with baseline. RVAP and RVOP significantly prolonged QRS duration, whereas HBP and LBBP showed non-significant effects. IVMD and PSD were significantly increased during RVAP but were not significantly different during RVOP, HBP, or LBBP. LBBP resulted in a significant improvement in the IVMD and Yu index compared with RVAP. No significant differences in mechanical synchrony were found between HBP and LBBP.

Conclusion: Among these pacing modalities, RVAP has a negative acute impact on cardiac synchrony and contraction. HBP and LBBP best preserve physiological cardiac synchrony and function.

New carotid plaque, but not the progression of intima-media thickness, predicts the progression of high-risk coronary plaque

BACKGROUND

Carotid intima-media thickness (CIMT) is regarded as a controversial risk marker for cardiovascular disease (CVD). We aimed to evaluate the role of CIMT and carotid plaque progression as predictors for the progression of coronary plaque and compositions.

METHODS

In the Garlic 4 study, asymptomatic patients with intermediate CVD risk (Framingham risk score 6-20%) were recruited for a serial carotid ultrasound, and coronary artery calcium score (CAC)/coronary computed tomography angiography (CCTA) studies for subclinical atherosclerosis at a baseline and 1 year. The association between progression of quantitatively measured coronary plaque compositions and the progression of CIMT/carotid plaque was analyzed. A P value <0.05 is considered as statistically significant.

RESULTS

Forty-seven consecutive patients were included. The mean age was 58.5 ± 6.6 years, and 69.1 % were male. New carotid plaque appeared in 34.0 % (n = 16) of participants, and 55.3 % (n = 26) of subjects had coronary plaque progression. In multilinear regression analysis, adjusted by age, gender, and statin use, the development of new carotid plaque was significantly associated with an increase in noncalcified coronary plaque [β (SE) 2.0 (0.9); P = 0.025] and necrotic core plaque (1.7 (0.6); P = 0.009). In contrast, CIMT progression was not associated with the progression of coronary plaque, or coronary artery calcium (CAC) (P = NS).

CONCLUSION

Compared to CIMT, carotid plaque is a better indicator of coronary plaque progression. The appearance of a new carotid plaque is associated with significant progression of necrotic core and noncalcified plaque, which are high-risk coronary plaque components.

Progressive tricuspid regurgitation and elevated pressure gradient after transvenous permanent pacemaker implantation

Background

The association of postimplant tricuspid regurgitation (TR) and heart failure (HF) hospitalization in patients without HF and preexisting abnormal TR and TR pressure gradient (PG) remain unclear.

Hypothesis

This study aimed to explore the clinical outcomes of progressive postimplant TR after permanent pacemaker (PPM) implantation.

Methods

A total of 1670 patients who underwent a single ventricular or dual‐chamber transvenous PPM implantation at our hospital between January 2003 and December 2017 were included in the study. Patients with prior valvular surgery, history of HF, and baseline abnormal TR and TRPG were excluded. Finally, a total of 1075 patients were enrolled in this study. Progressive TR was defined as increased TR grade of ≥2 degrees and TRPG of >30 mmHg after implant.

Results

In 198 (18.4%) patients (group 1) experienced progressive postimplant TR and elevated TRPG, whereas 877 patients (group 2) did not have progressive postimplant TR. Group 1 had larger change in postimplant TRPG (group 1 vs. group 2; 12.8 ± 9.6 mmHg vs. 1.1 ± 7.6 mmHg; p < .001) than group 2. Group 1 had a higher incidence of HF hospitalization compared to group 2 (13.6% vs. 4.7%; p < .001). Preimplant TRPG (HR: 1.075; 95% confidence interval [CI]: 1.032–1.121; p = .001) was an independent predictor of progressive postimplant TR.

Conclusions

After a transvenous ventricular‐based PPM implantation, 18.4% of patients experienced progressive postimplant TR and elevated TRPG. Higher preimplant TRPG was an independent predictor of progressive postimplant TR.

Pre-implant global longitudinal strain as an early sign of pacing-induced cardiomyopathy in patients with complete atrioventricular block

Introduction

Long‐term right ventricular pacing is the only treatment for patients with a complete atrioventricular block (CAVB); however, it frequently triggers ventricular dys‐synchrony with left ventricular (LV) dysfunction. Previous studies showed that an early decline of LV global longitudinal strain (GLS) predicts pacing‐induced LV dysfunction. We aimed to investigate the potential ability of the initial LV strain to predict pacing‐induced cardiomyopathy (PICM) through long‐term follow‐ups.

Methods

We retrospectively enrolled 80 patients with CAVB with normal LV function who were implanted with dual‐chamber pacemakers between 2008 and 2018. Echocardiographic data and parameters (including longitudinal, radial, and circumferential strain based on speckle‐tracking) were analyzed for the pre‐implant (≤6 months) and post‐implant periods. PICM was defined as a ≥10% reduction in the left ventricular ejection fraction (LVEF) resulting in an LVEF of <50% during the post‐implant period. Predictors of PICM were identified using Cox proportional hazard models.

Results

Patients who developed PICM were more likely to exhibit lower baseline LV GLS, as well as wider native and pacing QRS durations, than those who did not develop PICM (P = .016, P = .011, and P = .026, respectively). In the multivariate analysis, pre‐implant LV GLS (hazard ratio: 1.27; 95% confidence interval 1.009–1.492; P = .004) was independently associated with the development of PICM.

Conclusion

A lower baseline LV GLS predicts an increased risk of PICM. Patients with CAVB exhibiting low GLS are at increased risk of PICM. More frequent follow‐up visits are warranted in these patients, who may also require de novo His‐bundle pacing or an upgrade to biventricular pacing.

Unexpected findings before hospital discharge in a patient implanted with a dual-chamber pacemaker

A case of a patient implanted with a dual-chamber pacemaker in which routine ECG before discharge shown unexpected findings.

Incidence and predictors of pacemaker induced cardiomyopathy: A single-center experience

BACKGROUND

Pacemaker induced Cardiomyopathy (PICM) is an easily overlooked cause of heart failure with reduced ejection fraction. Data regarding this complication are sparse. Therefore, the aim of this study was to identify the incidence and predictors of PICM.

METHODS

Between 2011 and 2017, 857 consecutive patients undergoing pacemaker (PM) implantation, were reviewed, and according to our inclusion criteria 173 individuals were enrolled in this retrospective single center study. All patients included had normal left ventricular ejection fraction (LVEF) before implantation, underwent single-chamber ventricular or dual-chamber PM implantation, had RV pacing burden ≥20%, and repeated echocardiogram was available ≥1 year after implantation. PICM was defined as deterioration LVEF ≥10%, resulting in LVEF <50%, which cannot be explained by other causes.

RESULTS

During a mean follow-up of 39.9 ± 21.0 months, PICM occurred in 26 patients (16%). RV pacing percentage did not differ significantly between the both groups (76.5 vs 76.2%, p = 0.65). The PICM group patients were likely to be men (p = 0.002) and had a lower rate of arterial hypertension (p = 0.01). Multivariate analysis revealed male sex (HR 6.45, 0.95 CI 1.90-21.86, p = 0.003) and wider paced QRS complex (HR 1.04, 95% CI 1.02-1.07, p < 0.001) as predictors of PICM.

CONCLUSIONS

In patients with frequent RV pacing, the prevalence of PICM is not uncommon. Male sex and wider paced QRS complex are independent predictors of PICM and these patients may require closer follow-up.

Post-pacemaker implant QRS duration and heart failure admission in patients with sick sinus syndrome and complete atrioventricular block

AIMS

High demand right ventricular pacing may elicit left ventricular systolic dysfunction known as pacing-induced cardiomyopathy, increasing the risks of heart failure (HF) hospitalization. Percentage of demand ventricular pacing is different between patients with sick sinus syndrome (SSS) and those with complete atrioventricular block (CAVB). This study aims to compare the incidence of HF admission and pacing-induced cardiomyopathy between patients with SSS and CAVB.

METHODS AND RESULTS

A total of 824 patients who received single ventricular or dual-chamber pacemaker implantation at our hospital between January 2003 and December 2012 were recruited for the study. Patients with HF, those without complete cardiac echocardiography, and those with significant coronary artery disease were excluded. Finally, 315 patients with SSS and 289 patients with CAVB were enrolled in this study. The CAVB group had a higher pacing percentage (39.37 ± 9.17% vs. 83.82 ± 33.06%; P < 0.001), longer pacing QRS duration (142.56 ± 33.02 ms vs. 156.63 ± 25.18 ms; P < 0.001), and higher prevalence of follow-up left ventricular ejection fraction ≤40% (1.3% vs. 4.2%; P = 0.040). However, the incidence of HF admission was similar between the two groups (log-rank P = 0.647). Age [hazard ratio (HR), 95% confidence interval (CI): 1.121, 1.054-1.193], diabetes mellitus (HR, 95% CI: 2.667, 1.159-6.136), pacing QRS duration ≥163 ms (HR, 95% CI: 3.506, 1.491-8.247), and left atrial size (HR, 95% CI: 1.070, 1.012-1.131) were independent predictors of HF admission. The Kaplan-Meier curve showed a significant difference in HF admission over a 3.5 year follow-up period (3.5 years: P value = 0.004; 5 years: P value = 0.002) between patients with pacing QRS duration ≥163 and <163 ms.

CONCLUSIONS

There was no difference in HF admission between patients with SSS and CAVB, although the CAVB group had a higher pacing percentage. Post-pacemaker implant pacing QRS duration ≥163 ms was the most important predictor of HF admission.

Assessment of Permanent Selective His Bundle Pacing in Left Ventricular Synchronization Using 3-D Speckle Tracking Echocardiography

The study described here aimed to evaluate left ventricular (LV) systolic mechanical synchronization during permanent selective His bundle pacing (SHBP) using 3-D speckle-tracking echocardiography post-operatively and 6 mo after pacemaker implantation in 62 patients randomly assigned to SHBP (n = 32) or right ventricular apical pacing (RVAP, n = 30). A standard apex four-chamber view was exposed and was transformed into full-volume mode under 3-D echocardiography. Three-dimensional speckle-tracking echocardiography was analyzed offline. The primary endpoint was LV mechanical synchronization post-operatively and during the 6-mo follow-up. Significant LV dyssynchrony was detected while evaluating the maximum time difference and standard deviation of 16-segment systolic time to peak 3-D strain at 1 wk and 6 mo. The pacing thresholds were significantly higher in the SHBP than in the RVAP group throughout follow-up. The R-wave amplitude was significantly lower in the SHBP group than with RVAP. The pacing parameters during SHBP were as stable as during conventional RVAP during the mid-term follow-up. In conclusion, 3-D speckle-tracking echocardiography is feasible and provides a more convenient method for evaluating LV synchrony.

Recurrent, late-onset pleural effusions in elderly patients receiving pacemaker therapy

Late-onset pacemaker-related pleural effusions (PEs) are rare and are often misdiagnosed with other entities. Our study aimed to detail the clinical features and management of PEs long after pacemaker insertion.We conducted a review of 6 consecutive elderly patients with PEs, who had undergone a new pacemaker insertion from September 2014 to January 2017. Also, the clinical characteristics and therapeutic courses of PEs were summarized.Two cases involved fluids after the first implantations, with pacing durations of 3 and 7 months. Two other cases developed PEs 3 or 4 months after the first replacement, with pacing durations of 6 and 11 years. Another 2 cases developed PEs 3 or 5 months following the second replacement, with total pacing durations of 16 and 18 years, respectively. The average interval was 4.17 months for the 6 cases from the time of the new pacemaker insertion to the occurrence of PEs. During the course, they had to be hospitalized repeatedly for thoracenteses because conventional treatments had only short-term effects. After the pacing settings were adjusted, PEs in all cases disappeared gradually. No patients were readmitted for PEs during the median follow-up period of 13 months.For elderly patients following implantation of a new pacemaker, PEs should be considered due to improper pacing settings, and corresponding adjustments to the device should be made.

Adverse effects of left ventricular electrical dyssynchrony on cardiac reverse remodeling and prognosis after aortic valve surgery

BACKGROUND

Electrical dyssynchrony (ED) is one of the important contributing mechanisms in the progression of heart failure. We hypothesized that ED would interfere with cardiac reverse remodeling and affect prognosis after aortic valve surgery.

METHODS

A total of 411 consecutive patients (233 males, mean age 65±11 years) who underwent aortic valve surgery were retrospectively analyzed. The patients were divided into two groups according to the presence of ED [Group 1: no ED (n=382, 93%), Group 2: ED (n=29, 7%)]. ED was defined as either left ventricular bundle branch block, or electrical pacing rhythm. Cardiac reverse remodeling was assessed at 1 year after surgery by the changes in left ventricular ejection fraction (LVEF), LV end-systolic volume (LVESV), and left atrial volume index (LAVI). The primary endpoint was a composite of hospitalization for heart failure, and all-cause mortality.

RESULTS

At 1 year after surgery, group 2 showed lower LVEF (58±15% vs. 64±9%, p=0.044), and higher LAVI (42±18ml/m² vs. 33±13ml/m², p=0.018) than group 1. However, LVESV values (55±38ml vs. 42±24ml, p=0.076) were not significantly different. In particular, in patients with reduced preoperative LVEF, the LVEF was markedly increased in group 1 but not in group 2 after 1 year. During a median follow-up of 39 months, group 2 showed a worse clinical outcome than group 1 (20.7% vs. 7.6%, p=0.031). After adjusting for confounding factors in the multivariate analyses, age [hazard ratio (HR) 1.11, 95% confidence interval (CI) 1.06-1.16, p<0.001] and the presence of ED (HR 2.43, 95% CI 1.01-5.89, p=0.046) were found to be independent predictors of clinical outcomes.

CONCLUSIONS

ED after aortic valve surgery negatively affected cardiac remodeling and prognosis.

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.

Summary

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.

Major determinant of the occurrence of pacing-induced cardiomyopathy in complete atrioventricular block: a multicentre, retrospective analysis over a 15-year period in South Korea

OBJECTIVES

The predictors of pacing-induced cardiomyopathy (PICM) for complete atrioventricular block (CAVB) have not yet been defined. The aim of this study was to investigate the major determinant of the occurrence of PICM.

SETTING

This is a multicentre, retrospective analysis of CAVB from tertiary referral centres in Daejeon, South Korea.

PARTICIPANTS

A cohort of 900 consecutive patients with an implanted pacemaker was collected from December 2001 to August 2015. Of these, a total of 130 patients with CAVB with pacing-dependent rhythm who underwent ECG and echocardiogram before and after implantation were analysed for the occurrence of PICM.

OUTCOME MEASURES

Cox proportional hazards models evaluated the determinant of PICM by ECG, device parameters and echocardiogram over a mean of 4.5 years.

RESULTS

PICM was observed in 16.1% (n=21) of all patients with CAVB (age, 64±11 years; male, 36.2%). The preimplant left ventricular (LV) ejection fraction (66%±9% vs 66%±8%) and non-apical pacing (40.4% vs 33.3%) were similar; however, the native QRS duration (124±34 ms vs 149±32 ms) and the paced QRS duration (pQRSd) (139±29 ms vs 167±28 ms) were significantly different between the two groups. The postimplant LV ejection fraction (61%±7% vs 31%±8%) was also significantly different at the end of follow-up. A pQRSd significantly correlated with PICM (HR 1.05, 95% CI 1.02 to 1.09, P=0.001). A pQRSd with a cut-off value of above 140 ms had a sensitivity of 95% while a pQRSd with a cut-off value of above 167 ms had a specificity of 90% for PICM.

CONCLUSION

In patients with CAVB with pacing-dependent rhythm, regardless of the pacing site, the pQRSd is a major determinant of the occurrence of PICM.

Knowing About Device Algorithms to Understand the Rhythm and Role of Managed Ventricular Pacing

A 66-year-old patient with a DR pacemaker for intermittent atrioventricular block presented with an electrocardiogram (ECG) showing some P waves non followed by QRS complexes, raising suspicion of device dysfunction. The device was equipped with a special algorithm (Managed Ventricular Pacing; Medtronic), and the observed ECG tracing was a normal consequence of the function of such algorithms. Being aware of the function of specific algorithms is essential to adequately analyze rhythms.

Genetic Mechanisms Contribute to the Development of Heart Failure in Patients with Atrioventricular Block and Right Ventricular Apical Pacing

Right ventricular apical (RVA) pacing can lead to progressive left ventricular dysfunction and heart failure (HF), even in patients with normal cardiac structure and function. Our study conducted candidate gene screening and lentivirus transfected neonatal rat cardiomyocytes (NRCMs) to explore the genetic and pathogenic mechanisms of RVA pacing induced cardiomyopathy in third degree atrioventricular block (III AVB) patients. We followed 887 III AVB patients with baseline normal cardiac function and RVA pacing. After a median follow-up of 2.5 years, 10 patients (four males, mean age 47.6 ± 10.0 years) were diagnosed with RVA pacing induced HF with left ventricular ejection fraction (LVEF) reducing dramatically to 37.8 ± 7.1% (P  < 0.05). Candidate genes sequencing found cardiomyopathy associated genetic variations in all ten HF patients and six SCN5A variations in 6 of 20 control patients. Transfected NRCMs of Lamin A/C mutations (R216C and L379F) disrupted Lamin A/C location on nucleus membrane and finally resulted in increased apoptotic rate after serum starvation. In conclusion, cardiomyopathy associated genetic variations play an essential role in occurrence of newly onset HF in the III AVB patients with RVA pacing. RVA pacing, serving as extra stimulator, might accelerate the deterioration of cardiac structure and function.

Late deterioration of left ventricular function after right ventricular pacemaker implantation

Objectives:

Right ventricular (RV) pacing induces a left bundle branch block pattern on ECG and may promote heart failure. Patients with dual chamber pacemakers (DCPs) who present with progressive reduction in left ventricular ejection fraction (LVEF) secondary to RV pacing are candidates for cardiac resynchronization therapy (CRT). This study analyzes whether upgrading DCP to CRT with the additional implantation of a left ventricular (LV) lead improves LV function in patients with reduced LVEF following DCP implantation.

Methods:

Twenty-two patients (13 males) implanted with DCPs and a high RV pacing percentage (>90%) were evaluated in term of new-onset heart failure symptoms. The patients were enrolled in this retrospective single-center study after obvious causes for a reduced LVEF were excluded with echocardiography and coronary angiography. In all patients, DCPs were then upgraded to biventricular devices. LVEF was analyzed with a two-sided t-test. QRS duration and brain natriuretic peptide (BNP) levels were analyzed with the unpaired t-test.

Results:

LVEF declined after DCP implantation from 54±10% to 31±7%, and the mean QRS duration was 161±20 ms during RV pacing. NT-pro BNP levels were elevated (3365±11436 pmol/L). After upgrading to a biventricular device, a biventricular pacing percentage of 98.1±2% was achieved. QRS duration decreased to 108±16 ms and 106±20 ms after 1 and 6 months, respectively. There was a significant increase in LVEF to 38±8% and 41±11% and a decrease in NT-pro BNP levels to 3088±2326 pmol/L and 1860±1838 pmol/L at 1 and 6 months, respectively.

Conclusion:

Upgrading to CRT may be beneficial in patients with DCPs and heart failure induced by a high RV pacing percentage.

MR feature tracking in patients with MRI-conditional pacing systems: The impact of pacing

PURPOSE

To develop feature tracking (FT) software to perform strain analysis on conventional (nontagged) cardiac magnetic resonance imaging (MRI) function images. With the advent of MRI-conditional pacemaker systems, effects of cardiac pacing on myocardial strain can be studied using MR. In this study the impact of pacing on left ventricular (LV) strain was investigated using MR-FT in patients with an MRI-conditional cardiac implantable electronic device (CIED).

MATERIALS AND METHODS

FT was performed on 32 1.5T MR studies (16 patients with an MRI-conditional CIED and 16 control patients with normal scans). Short- and long-axis steady state free precession (SSFP) cines were used for the FT analysis. Strain was assessed using CVI(42) software (Circle Cardiovascular Imaging, Alberta, Canada). In addition, the intra- and interobserver variability was determined using the intraclass correlation coefficient.

RESULTS

Of the 16 patients with an MRI-conditional CIED, five patients were paced during the MRI exam. Despite the occasional presence of susceptibility artifacts induced by the CIED, radial, circumferential, and longitudinal strain parameters could be derived for all patients. Peak radial strain and peak circumferential strain were reduced during pacing when compared to the control group; for radial strain: 20.1 ± 4.7% vs. 33.1 ± 6.9%, P < 0.001, and for circumferential strain -7.5 ± 3.5% vs. -14.9 ± 3.2%, P < 0.05. Peak strain parameters were reproducible on an intra- and interobserver level.

CONCLUSION

MR-FT is feasible in patients with an MRI-conditional CIED and can be used to quantify regional wall motion. J. MAGN. RESON. IMAGING 2016;44:964-971.

Non-invasive focus localization, right ventricular epicardial potential mapping in patients with an MRI-conditional pacemaker system - a pilot study

Background

With the advent of magnetic resonance imaging (MRI) conditional pacemaker systems, the possibility of performing MRI in pacemaker patients has been introduced. Besides for the detailed evaluation of atrial and ventricular volumes and function, MRI can be used in combination with body surface potential mapping (BSPM) in a non-invasive inverse potential mapping (IPM) strategy. In non-invasive IPM, epicardial potentials are reconstructed from recorded body surface potentials (BSP). In order to investigate whether an IPM method with a limited number of electrodes could be used for the purpose of non-invasive focus localization, it was applied in patients with implanted pacing devices. Ventricular paced beats were used to simulate ventricular ectopic foci.

Methods

Ten patients with an MRI-conditional pacemaker system and a structurally normal heart were studied. Patient-specific 3D thorax volume models were reconstructed from the MRI images. BSP were recorded during ventricular pacing. Epicardial potentials were inversely calculated from the BSP. The site of epicardial breakthrough was compared to the position of the ventricular lead tip on MRI and the distance between these points was determined.

Results

For all patients, the site of earliest epicardial depolarization could be identified. When the tip of the pacing lead was implanted in vicinity to the epicardium, i.e. right ventricular (RV) apex or RV outflow tract, the distance between lead tip position and epicardial breakthrough was 6.0 ± 1.9 mm.

Conclusions

In conclusion, the combined MRI and IPM method is clinically applicable and can identify sites of earliest depolarization with a clinically useful accuracy.

Electronic supplementary material

The online version of this article (doi:10.1007/s10840-015-0054-9) contains supplementary material, which is available to authorized users.

Atrioventricular Junction Ablation In Atrial Fibrillation: Choosing The Right Patient And Pacing Device

Atrial fibrillation (AF) is the most common cardiac arrhythmia and despite advancements in rhythm control through direct catheter ablation, maintaining sinus rhythm is not possible in a large proportion of AF patients, who therefore are subject to a rate control strategy only. Nonetheless, in some of these patients pharmacological rate control may be ineffective, often leaving the patient highly symptomatic and at risk of developing tachycardia-induced cardiomyopathy and heart failure (HF). Catheter ablation of the atrioventricular junction (AVJ) with subsequent permanent pacemaker implantation provides definite rate control and represents an attractive therapeutic option when pharmacological rate control is not achieved. In patients with reduced ventricular function, cardiac resynchronization therapy (CRT) should be considered over right ventricular apical (RVA) pacing in order to avoid the deleterious effects associated with a high amount of chronic RVA pacing. Another group of patients that may also benefit from AVJ ablation are HF patients with concomitant AF receiving CRT. In this patient cohort AVJ ablation ensures near 100% biventricular pacing, thus allowing optimization of the therapeutic effects of CRT.

Cardiac resynchronization therapy is appropriate for all patients requiring chronic right ventricular pacing: the pro perspective

Long-term right ventricular pacing has deleterious effects on the left ventricle (LV). The risk of pacemaker-induced cardiomyopathy (PICM) seems to be lower in patients with a normal LV ejection fraction (LVEF). Patients developing PICM respond favorably to a cardiac resynchronization therapy upgrade, suggesting that the dysfunction is partially reversible. Biventricular pacing has emerged as a treatment and/or prevention of PICM. Cumulative pacing greater than 40% of the time is considered the most important risk factor for PICM. No organizational guidelines exist for preventive biventricular pacing. The decision to pursue biventricular pacing should be individualized.

The changing landscape of cardiac pacing

A number of trials have shown that irrespective of baseline QRS duration, left ventricular (LV) dysfunction and heart failure are more common in patients with right ventricular (RV) than in those with biventricular (BiV) pacing. By contrast, preliminary results of the BIOPACE trial (follow-up 5.6 years) yielded a disappointing comparison of RV vs. BiV pacing. Pacemaker-induced cardiomyopathy (PIC) may occur in patients with normal and abnormal LV ejection fractions (LVEF) and tends to occur if there is RV pacing more than 40 % of the time. Yet, some pacemaker-dependent patients do not develop LV dysfunction. PIC can be improved in about two thirds of patients by upgrading to a BiV system and the results are comparable to de novo BiV pacing in patients with a wide QRS complex. The findings of the BLOCK HF trial (2013) suggested that patients requiring pacing virtually 100 % of the time might benefit from BiV pacing irrespective of the LVEF (< 50 %), manifestations of heart failure, QRS duration, or functional class. These characteristics would generate many patients for BiV pacing. However, these recommendations should now be weighed against a more conservative approach based on the recently announced results of the BIOPACE trial. Organizational guidelines recommend BiV pacing for bradycardia irrespective of QRS duration for patients with LVEF < 35 %. At this time, BiV pacing for antibradycardia therapy (irrespective of QRS duration) has to be individualized in the setting of a normal or decreased LVEF (> 35 %) and according to the expected percentage of RV pacing. The benefit of BiV pacing should be considered against procedural complications, which are more frequent than with traditional RV pacing.

The role of biventricular pacing in the prevention and therapy of pacemaker-induced cardiomyopathy

Right ventricular (RV) pacing produces well-known long-term deleterious effects not only on already compromised, but also on the normal left ventricle (LV). The activation pattern mimicks that of left bundle branch block, with delayed activation of the LV free wall, and results in electrical and mechanical dyssynchrony. Long-term mandatory (100%) RV pacing, increases LV dimensions and decreases the ejection fraction. Many of these negative effects of pacing can be overcome by biventricular pacing. In this review, we describe the characteristics of pacemaker-induced cardiomyopathy, its incidence, and the use of cardiac resynchronization therapy (CRT) for its therapy and prevention. The gaps in the current organizational guidelines for using CRT in the treatment of bradycardia are identified, and goals for future research are discussed.