Occurrence of phrenic nerve stimulation in cardiac resynchronization therapy patients: the role of left ventricular lead type and placement site

Clinical Usefulness of the Active Fixation Quadripolar Left Ventricular Lead Compared With the Passive Fixation Quadripolar Lead in Cardiac Resynchronization Therapy

BACKGROUND

This study compared the stability of the Medtronic Attain Stability Quad (ASQ), a novel quadripolar active fixation left ventricular (LV) lead with a side helix, to that of conventional quadripolar leads with passive fixation (non-ASQ) and evaluated their LV lead performance.

METHODS AND RESULTS

In all, 183 consecutive patients (69 ASQ, 114 non-ASQ) who underwent cardiac resynchronization therapy (CRT) between January 2018 and June 2021 were enrolled. Complications, including elevated pacing capture threshold (PCT) levels, phrenic nerve stimulation (PNS), and LV lead dislodgement, were analyzed during the postimplantation period until the first outpatient visit after discharge. The frequency of LV lead-related complications was significantly lower in the ASQ than non-ASQ group (14% vs. 30%, respectively; P=0.019). Specifically, LV lead dislodgement occurred only in the non-ASQ group, and elevated PCT levels were significantly lower in the ASQ group (7% vs. 23%; P=0.007). Kaplan-Meier analysis confirmed a significantly lower incidence of LV lead-related complications in the ASQ group (log-rank P=0.005). Cox multivariable regression analysis showed a significant reduction in lead-related complications associated with ASQ (hazard ratio 0.44; 95% confidence interval 0.23-0.83; P=0.011).

CONCLUSIONS

The ASQ group exhibited fewer LV lead-related complications requiring reintervention and setting changes than the non-ASQ group. Thus, the ASQ may be a favorable choice for CRT device implantation.

Performance of the quadripolar CRT-D system: Five-year results from the Quadripolar Pacing Post-Approval Study

BACKGROUND

Cardiac resynchronization therapy (CRT) is associated with challenges such as elevated capture thresholds, diaphragmatic stimulation, and lead instability.

OBJECTIVE

This study aimed to assess the long-term safety and efficacy of the quadripolar CRT-defibrillator (CRT-D) device system with the Quartet 1458Q left ventricular (LV) lead in a CRT-indicated population observed for 5 years and to evaluate all-cause mortality and impact of baseline characteristics on survival through 5 years.

METHODS

Patients indicated for a CRT-D system were observed every 6 months after implantation for 5 years, and device performance and adverse events were assessed at each visit. The 3 primary end points were freedom from quadripolar CRT-D system-related complications through 5 years, freedom from Quartet 1458Q LV lead-related complications through 5 years, and mean programmed pacing capture threshold at 5 years.

RESULTS

The study enrolled 1970 participants at 71 sites. The quadripolar CRT-D system was successfully implanted in 97.2% of participants. Freedom from quadripolar CRT-D device system-related complications through 5 years was 89.7%. Freedom from Quartet 1458Q LV lead-related complications through 5 years was 95.7%; 3.49% of participants had LV lead-related complications, and an overall LV lead complication rate was 0.0122 event per patient-year. The mean LV pacing capture threshold was 1.52 ± 1.01 V at 5 years. The 5-year survival rate was 67.4%.

CONCLUSION

The quadripolar CRT-D system with the Quartet 1458Q LV lead exhibited low rates of complications and stable electrical performance through 5 years of follow-up and suggested a higher 5-year survival rate compared with traditional CRT systems.

Conduction System Pacing for Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) via biventricular pacing (BiVP-CRT) is considered a mainstay treatment for symptomatic heart failure patients with reduced ejection fraction and wide QRS. However, up to one-third of patients receiving BiVP-CRT are considered non-responders to the therapy. Multiple strategies have been proposed to maximize the percentage of CRT responders including two new physiological pacing modalities that have emerged in recent years: His bundle pacing (HBP) and left bundle branch area pacing (LBBAP). Both pacing techniques aim at restoring the normal electrical activation of the ventricles through the native conduction system in opposition to the cell-to-cell activation of conventional right ventricular myocardial pacing. Conduction system pacing (CSP), including both HBP and LBBAP, appears to be a promising pacing modality for delivering CRT and has proven to be safe and feasible in this particular setting. This article will review the current state of the art of CSP-based CRT, its limitations, and future directions.

Case report: An unusual case of phrenic nerve stimulation in a patient with single chamber implantable cardioverter defibrillator

Background

Phrenic nerve stimulation is a well-recognized complication related to cardiac implantable electronic devices, in particular with left ventricular coronary sinus pacing leads for cardiac resynchronization therapy.

Case presentation

We report an unusual case of symptomatic phrenic nerve stimulation due to inadvertent placement of a right ventricular defibrillation lead in coronary sinus posterior branch in a patient with heart failure with reduced ejection fraction with a recently implanted single-chamber cardioverter defibrillator.

Discussion

Phrenic nerve stimulation is a relatively common complication of left ventricular pacing. Inadvertent placement of a right ventricular lead in a coronary sinus branch is a rare but possible cause of phrenic nerve stimulation. Careful evaluation of intraprocedural fluoroscopic and electrocardiographic appearance of pacing and defibrillation leads during implantation may prevent inadvertent placement of a right ventricular lead in the coronary sinus.

Therapeutic benefits of distal ventricular pacing in mid-cavity obstructive hypertrophic cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) patients with left ventricular (LV) mid-cavity obstruction (LVMCO) often experience severe drug-refractory symptoms thought to be related to intraventricular obstruction. We tested whether ventricular pacing, guided by invasive haemodynamic assessment, reduced LVMCO and improved refractory symptoms.

METHODS

Between December 2008 and December 2017, 16 HCM patients with severe refractory symptoms and LVMCO underwent device implantation with haemodynamic pacing study to assess the effect on invasively defined LVMCO gradients. The effect on the gradient of atrioventricular (AV) synchronous pacing from sites including right ventricular (RV) apex and middle cardiac vein (MCV) was retrospectively assessed.

RESULTS

Invasive haemodynamic data were available in 14 of 16 patients. Mean pre-treatment intracavitary gradient was 77 ± 22 mmHg (in sinus rhythm) versus 21 ± 21 mmHg during pacing from optimal ventricular site (95% CI: -70.86 to -40.57, p < 0.0001). Optimal pacing site was distal MCV in 12/16 (86%), RV apex in 1/16 and via epicardial LV lead in 1/16. Pre-pacing Doppler-derived gradients were significantly higher than at follow-up (47 ± 15 versus 24 ± 16 mmHg, 95% CI: -37.19 to -13.73, p < 0.001). Median baseline NYHA class was 3, which had improved by ⩾1 NYHA class in 13 of 16 patients at 1-year post-procedure (p < 0.001). The mean follow-up duration was 4.6 ± 2.7 years with the following outcomes: 8/16 (50%) had continued symptomatic improvement, 4/16 had symptomatic decline and 4/16 died. Contributors to symptomatic decline included chronic atrial fibrillation (AF) (n = 5), phrenic nerve stimulation (n = 3) and ventricular ectopy (n = 1).

CONCLUSION

In drug-refractory symptomatic LVMCO, distal ventricular pacing can reduce intracavitary obstruction and may provide long-term symptomatic relief in patients with limited treatment options. A haemodynamic pacing study is an effective strategy for identifying optimal pacing site and configuration.

Bipolar versus quadripolar left ventricular leads for cardiac resynchronization therapy: evidence to date

INTRODUCTION

In cardiac resynchronization therapy (CRT) devices, transvenous left ventricular (LV) leads are more prone to instability, high pacing thresholds, and phrenic nerve stimulation (PNS) that may necessitate lead revision, replacement in a suboptimal position, or deactivation of the lead. To overcome some of these challenges, quadripolar (QP) LV leads have been developed and accounted for over 90% of implanted LV leads 5 years after they were introduced.

AREAS COVERED

This review provides an overview of the current evidence of implanting QP leads in CRT as compared with traditional bipolar (BP) leads including details about feasibility, safety and lead performance, clinical outcome and cost-effectiveness.

EXPERT OPINION

Based on the current literature, implantation with a QP lead decreases revision rates but does not affect any clinical outcomes including mortality, hospitalization, symptoms, or echocardiographic parameters. Feasibility and stability do not differ between QP and BP leads. A QP lead should be preferred as first choice over a BP lead due to lower rates of PNS and lower pacing thresholds leading to less frequent lead revisions and battery replacements. In addition, this strategy may be cost saving despite a higher price of QP leads.

Phrenic nerve stimulation, a rare complication of pacemaker: A case report

RATIONALE

The phrenic nerve stimulation (PNS) is a rare complication after pacemaker setting. We report a case report that describes this complication and how it can be resolved.

PATIENT CONCERNS

An 88-year-old man presented himself to the emergency geriatric unit with intermittent painless abdominal contraction due to phrenic nerve stimulation. He has a history of transcatheter aortic valve implantation with cardiac resynchronization therapy pacemaker due to persistent left bundle branch block.

DIAGNOSES

All the usual causes for abdominal spasms were eliminated and the possibility of a link with the pacemaker was considered. The phrenic nerve stimulation is a rare complication of a pacemaker implantation. It can be clinically nonrelevant but challenging to diagnose for those not familiar with cardiac devices technology.

INTERVENTIONS

Initial setting was an axis of stimulation between distal left ventricular (LV) and right ventricular. It was changed to LV and D1-M2.

OUTCOMES

This noninvasive procedure managed to eradicate the involuntary abdominal spasms.

LESSONS

PNS could be challenging to diagnose for those not familiar with cardiac devices technology but easy to manage with noninvasive methods.

Device Adjustment and Recovery in Patients With Heart Failure Undergoing a Cardiac Resynchronization Therapy Implantation: A Longitudinal Study

BACKGROUND

Little is known about risk factors for poor adjustment to the device after cardiac resynchronization therapy (CRT) implantation in patients with heart failure.

PURPOSE

The aim of this study was to explore device adjustment and the postoperative recovery of patients with heart failure undergoing elective CRT device implantation.

METHODS

In this prospective multicenter longitudinal study, data were collected before implantation and after 2 weeks, 6 months, and 1 year, using validated self-reported instruments and investigator-designed, CRT-specific questions.

RESULTS

A total of 133 patients, 79% male, with a mean age of 70 ± 10 years, were included. Patients adjusted to the device over time (P < .001), but 20% of patients had difficulties after 2 weeks, and 11% had difficulties at the 1-year follow-up. Fatigue was the most common health problem before surgery (87%), which was reduced to 65% after 1 year, P < .001. Patients' recovery improved over time (P < .001). Device-specific problems with hiccups (7% vs 14%), pulsation around the device (29% vs 24%), tachycardia (28% vs 29%), appearance of the scar (21% vs 17%), and the device bulging out (65% vs 61%) remained unchanged over time, whereas stiffness in the shoulder (64% vs 28%, P < .001) and wound healing (9% vs 2%, P < .05) improved.

CONCLUSIONS

Most patients with heart failure recover and adjust early after their CRT implantation and improve even more during follow-up. However, recovery and adjustment are problematic for some patients, and many experience bodily discomforts because of the device. Early screening for poor adjustment and psychological distress can lead to appropriate interventions and timely referrals. This is important in the era of remote monitoring with less face-to-face contact.

Clinical outcome of cardiac resynchronization therapy in patients randomized to an active fixation bipolar left ventricular lead versus a passive quadripolar lead

Objectives: To compare the clinical outcome of cardiac resynchronization therapy (CRT) in patients receiving a bipolar left ventricular (LV) lead with a side helix for active fixation to the outcome in patients receiving a quadripolar passive fixation LV lead.Design: Sixty-two patients (mean age 72 ± 11 years) were blindly and randomly assigned to the active fixation bipolar lead group (n = 31) or to the quadripolar lead group (n= 31). The LV leads were targeted to the basal LV segment in a vein concordant to the LV segment with the latest mechanical contraction chosen on the basis of preoperative radial strain (RS) echocardiography.Results: At the 6-month follow-up (FU), the reduction in LV end-systolic volume and LV reverse remodelling responder rate, defined as LV end-systolic volume reduction >15%, was 77% in the active fixation group and 83% in the quadripolar group, which was not significantly different. At the 12-month FU, the LV ejection fraction (LVEF) did not differ between the groups. There were no significant differences between the two groups in changes in New York Heart Association (NYHA) functional class or Minnesota Living with Heart Failure Questionnaire score. The occurrence of phrenic nerve stimulation (PNS) was 19% in the active fixation group versus 10% in the quadripolar group (p=.30), and all cases were resolved by reprogramming the device. All patients were alive at the 12-month FU. There was no device infection.Conclusions: There were no significant differences between the active fixation group of patients and the quadripolar group of patients concerning improvement in echocardiographic parameters or clinical symptoms.ClinicalTrials.gov number, NCT04632472.

Single- and dual-site ventricular pacing entirely through the coronary sinus for patients with prior tricuspid valve surgery

PURPOSE

Transvenous right ventricular pacing has traditionally been avoided after surgical tricuspid valve repair or replacement because of possible valvular dysfunction. Epicardial pacing has been used but it requires surgical thoracotomy and has higher lead failure rates when compared to transvenous pacing. We evaluated the lead stability and clinical outcomes in patients with isolated coronary sinus (CS) lead due to relative contraindication to transvenous pacing from prior tricuspid valve (TV) surgery.

METHODS

We retrospectively examined a single-center cohort of 34 patients with TV disease and/or surgery who underwent permanent pacemaker implantation with a left ventricular CS lead as the only ventricular pacing lead (to avoid crossing the TV). The clinical outcome, echocardiographic data, and pacing thresholds were evaluated at follow-up.

RESULTS

We implanted 19 patients with a single-CS lead and 15 patients with dual-CS leads. The average left ventricular ejection fraction was 56 ± 13% prior to lead implantation and remained stable at 2-year follow-up. The tricuspid regurgitation remained mild at follow-up. The average lead pacing threshold was 1.2 ± 0.6 V × ms at implant and 1.1 ± 0.4 V × ms at 2-year follow-up (P = 0.39). For patients with dual-CS leads, the pacing threshold was 1.2 ± 0.7 V × ms at implant and 1.1 ± 0.5 V × ms at 2-year follow-up (P = 0.52).

CONCLUSIONS

The use of ventricular pacing entirely through the CS is an effective and minimally invasive method that provides stable pacing for patients with prior TV surgery in whom transvenous lead placement either is not possible or is relatively contraindicated.

Quadripolar versus bipolar leads in cardiac resynchronization therapy: An analysis of the National Cardiovascular Data Registry

BACKGROUND

The introduction of quadripolar (QP) cardiac resynchronization therapy (CRT) leads aimed to improve procedural and clinical outcomes.

OBJECTIVE

The National Cardiovascular Data Registry was analyzed to characterize the use as well as the procedural and clinical outcomes of QP leads in comparison with unipolar and bipolar (BP) leads.

METHODS

We evaluated data on 175,684 procedures reported between September 1, 2010, and December 31, 2015. Clinical outcomes were analyzed using Centers for Medicare & Medicaid Services claims data.

RESULTS

Among all CRT device implants, there was a drop in reported lead placement failure from 6.04% to 5.21% (P < .0001 for trend) and a drop in the reported diaphragmatic stimulation rates from 0.07% to 0.01% (P < .007 for trend) between the last quarters of 2010 and 2015. No significant difference in procedural complication rates between QP and BP leads occurred (1.34% and 1.39%, respectively; P = .50). Among patients linked to Centers for Medicare & Medicaid Services claims data, no statistically significant difference in the combined primary outcome of death, congestive heart failure admission, device malfunction, and reoperation between BP and QP leads was observed (34.15 and 34.19 events per 100 patient-years, respectively; P = .89).

CONCLUSION

Since the introduction of QP leads, there was a reduction in CRT lead placement failure rates and a reduction in diaphragmatic stimulation rates. However, no statistically significant difference in long-term clinical outcomes between BP and QP leads was observed in elderly patients undergoing CRT implantation.

Clinical outcomes after implantation of quadripolar compared to bipolar left ventricular leads in patients undergoing cardiac resynchronization therapy: a systematic review and meta-analysis

Aims

Some retrospective and prospective studies in heart failure patients with indication for cardiac resynchronization therapy (CRT) suggest better clinical outcomes for quadripolar (QP) left ventricular (LV) leads over bipolar (BP) leads. Although, lead failure remains an important safety concern, when using these more complex, novel electrodes. To evaluate safety and efficacy outcomes for QP vs. BP LV leads in patients receiving CRT.

Methods and results

We performed a comprehensive literature search through 2018 in PubMed, Cochrane Library, and Google Scholar databases to identify studies comparing patients with QP and BP LV CRT leads. A total of 12 studies were selected for analysis comprising 31 403 patients (QP lead: 22 429 patients; BP lead: 8974 patients). Eight studies examined the effects of CRT on survival. In these studies, use of QP electrodes was associated with significantly better survival compared to patients with BP LV leads (OR 0.61, 95% CI 0.50–0.76; P < 0.01). Clinical improval measured in New York Heart Association functional class (OR 0.59, 95% CI 0.34–1.01; P = 0.05) and hospitalization rates (OR 0.67, 95% CI 0.55–0.83; P < 0.01) were also improved in patients receiving QP leads. Lead malfunctions defined as LV lead failure resulting in lead deactivation (OR 0.57, 95% CI 0.34–0.98; P = 0.04) or LV lead dislodgement requiring LV lead replacement/repositioning (OR 0.48; 95% CI 0.31–0.75; P < 0.01) were more often encountered among patients with BP leads compared to patients with QP leads.

Conclusion

Our meta-analysis suggests distinct benefits of QP over BP electrodes in patients undergoing CRT.

Cost-Effectiveness Analysis of Quadripolar Versus Bipolar Left Ventricular Leads for Cardiac Resynchronization Defibrillator Therapy in a Large, Multicenter UK Registry

OBJECTIVES

The objective of this study was to evaluate the cost-effectiveness of quadripolar versus bipolar cardiac resynchronization defibrillator therapy systems.

BACKGROUND

Quadripolar left ventricular (LV) leads for cardiac resynchronization therapy reduce phrenic nerve stimulation (PNS) and are associated with reduced mortality compared with bipolar leads.

METHODS

A total of 606 patients received implants at 3 UK centers (319 Q, 287 B), between 2009 and 2014; mean follow-up was 879 days. Rehospitalization episodes were costed at National Health Service national tariff rates, and EQ-5D utility values were applied to heart failure admissions, acute coronary syndrome events, and mortality data, which were used to estimate quality-adjusted life-year differences over 5 years.

RESULTS

Groups were matched with regard to age and sex. Patients with quadripolar implants had a lower rate of hospitalization than those with bipolar implants (42.6% vs. 55.4%; p = 0.002). This was primarily driven by fewer hospital readmissions for heart failure (51 [16%] vs. 75 [26.1%], respectively, for quadripolar vs. bipolar implants; p = 0.003) and generator replacements (9 [2.8%] vs. 19 [6.6%], respectively; p = 0.03). Hospitalization for suspected acute coronary syndrome, arrhythmia, device explantation, and lead revisions were similar. This lower health-care utilization cost translated into a cumulative 5-year cost saving for patients with quadripolar systems where the acquisition cost was <£932 (US $1,398) compared with bipolar systems. Probabilistic sensitivity analysis results mirrored the deterministic calculations. For the average additional price of £1,200 (US $1,800) over a bipolar system, the incremental cost-effective ratio was £3,692 per quality-adjusted life-year gained (US $5,538), far below the usual willingness-to-pay threshold of £20,000 (US $30,000).

CONCLUSIONS

In a UK health-care 5-year time horizon, the additional purchase price of quadripolar cardiac resynchronization defibrillator therapy systems is largely offset by lower subsequent event costs up to 5 years after implantation, which makes this technology highly cost-effective compared with bipolar systems.

Bipolar active fixation left ventricular lead or quadripolar passive fixation lead? An Italian multicenter experience

AIMS

About one-third of patients receiving cardiac resynchronization therapy (CRT) are not responders, due to either patient selection or technical issues. Left ventricular quadripolar passive fixation leads (QPL) and bipolar active fixation (BAF) leads have been designed to ensure a targeted left ventricular stimulation area, minimizing lead dislodgments and phrenic nerve stimulation (PNS). The aim was to compare real-world safety and efficacy of BAF (Attain Stability, Medtronic Plc.) and QPL (Attain Performa, Medtronic Plc.).

METHODS

We performed a retrospective analysis examining procedural and follow-up data of 261 BAF and 124 QPL (programmed to single-site left ventricular pacing), included in the ClinicalService project from 16 Italian hospitals.

RESULTS

At median follow-up of 12 months, no difference in left ventricular pacing threshold was recorded between BAF and QPL (1.3 ± 0.9 V @0.4 ms vs. 1.3 ± 1.0 V @0.4 ms; P = 0.749). Total left ventricular lead dislodgement rate was 1.43/100 patient-years in BAF vs. 2.9/100 patient-years in QPL (P = 0.583). However, no dislodgements occurred among BAF after hospital discharge. Events requiring repeated surgery or permanently turning CRT off occurred in 0.8% of BAF, as compared with 4.0% of QPL (P = 0.025). There was no difference between groups in the echo CRT responders' rate (70% of BAF and 66% of QPL; P = 0.589) or in the annual rate of heart failure hospitalization (P = 0.513).

CONCLUSIONS

BAF resulted in noninferior clinical outcome and CRT responders' rate in comparison to QPL. Moreover, BAF ensured more precise and stable placement in cardiac veins, with comparable electrical performance and less than 1% patients with unsolved PNS.

Super-response to cardiac resynchronization therapy may predict late phrenic nerve stimulation

Aims

Changes in the anatomical relationship between left phrenic nerve and coronary veins may occur due to the reverse remodelling observed in super-responders to cardiac resynchronization therapy (CRT) and might be the underlying mechanism in patients developing late-onset phrenic nerve stimulation (PNS) without evidence of lead dislodgement (LD). In this study, we sought to evaluate the role of super-response (SR) to CRT as a potential predictor of late-onset PNS.

Methods and results

Consecutive patients implanted with a left ventricular (LV) lead in a single centre were retrospectively analysed. Phrenic nerve stimulation was classified as 'early' when it occurred within 3 months of implantation and 'late' for occurrences thereafter. 'Late' PNS was considered related to LD (LD-PNS) when LV threshold differed by > 1 V or impedance >250 Ω from baseline values or in case of radiological displacement. Cases not meeting the former criteria were classified as 'non-LD-PNS'. Super-response was defined as a decrease ≥30% of the left ventricluar end-systolic volume at 1-year echocardiography. At 32 ± 7 months follow-up, PNS occurred in 20 of 139 patients. Late non-LD-PNS incidence was significantly higher in the SR group (8/61; 13.1%) when compared with the non-SR (1/78; 1.3%) (P = 0.010). Super-response remained the only predictor of non-LD-PNS at multivariate analysis (odds ratio: 11.62, 95% confidence interval 1.41-95.68, P = 0.023).

Conclusion

Incidence of late non-LD-PNS is higher among SR to CRT, suggesting a potential role of the changes in the anatomical relationship between left phrenic nerve and coronary veins.

Cardiac resynchronization therapy: a comparison among left ventricular bipolar, quadripolar and active fixation leads

We evaluated the performance of 3 different left ventricular leads (LV) for resynchronization therapy: bipolar (BL), quadripolar (QL) and active fixation leads (AFL). We enrolled 290 consecutive CRTD candidates implanted with BL (n = 136) or QL (n = 97) or AFL (n = 57). Over a minimum 10 months follow-up, we assessed: (a) composite technical endpoint (TE) (phrenic nerve stimulation at 8 V@0.4 ms, safety margin between myocardial and phrenic threshold <2V, LV dislodgement and failure to achieve the target pacing site), (b) composite clinical endpoint (CE) (death, hospitalization for heart failure, heart transplantation, lead extraction for infection), (c) reverse remodeling (RR) (reduction of end systolic volume >15%). Baseline characteristics of the 3 groups were similar. At follow-up the incidence of TE was 36.3%, 14.3% and 19.9% in BL, AFL and QL, respectively (p < 0.01). Moreover, the incidence of RR was 56%, 64% and 68% in BL, AFL and QL respectively (p = 0.02). There were no significant differences in CE (p = 0.380). On a multivariable analysis, "non-BL leads" was the single predictor of an improved clinical outcome. QL and AFL are superior to conventional BL by enhancing pacing of the target site: AFL through prevention of lead dislodgement while QL through improved management of phrenic nerve stimulation.

Long-term electrical performance of Attain Performa quadripolar left ventricular leads with all steroid-eluting electrodes: Results from a large worldwide clinical trial

BACKGROUND

Steroid-eluting (SE) electrodes suppress local inflammation and lower pacing capture thresholds (PCT); however, their effectiveness on quadripolar left ventricular (LV) leads in the cardiac vein is not fully studied. We evaluated the effectiveness of SE on all four LV pacing electrodes in human subjects enrolled in the Medtronic Attain® Performa™ quadripolar LV lead study.

METHODS

A total of 1,097 subjects were included in this evaluation. At each follow-up visit (1, 3, 6, and 12 months), LV PCT and pacing impedance were measured using either manual or automated testing methods. Summary statistics for PCT and impedance values were obtained for implant and each scheduled follow-up visit for all lead models.

RESULTS

Average extended bipolar (LV electrode to right ventricular Coil) PCTs for the four LV SE pacing electrodes (LV1, LV2, LV3, and LV4) on the three shapes of the quadripolar LV leads were 1.06 ± 0.97 V, 1.38 ± 1.26 V, 1.51 ± 1.33 V, and 2.25 ± 1.63 V, respectively, at 0.5-ms pulse width. PCTs remained low and stable throughout the 12-month follow-up period.

CONCLUSION

This clinical trial demonstrated that SE on all LV pacing electrodes is associated with low and stable PCTs for all quadripolar LV lead electrodes, resulting in multiple viable vectors for LV pacing. The large number of available vectors facilitates basal pacing, avoidance of PNS, and potentially prolongs generator longevity due to lower PCTs.

Impact of intraoperative mechanical ventilation on left ventricular lead function in cardiac resynchronization therapy

BACKGROUND

Intraoperative controlled mechanical ventilation (CMV) changes the intrathoracic geometry and may impact postoperative left ventricular (LV) lead function after CRT implantation. This multicenter study investigates the effect of intraoperative ventilation setting (spontaneous breathing [SB] vs CMV) on postoperative LV lead function taking into account patients' body mass index (BMI).

METHODS

CRT implantation was performed at two centers during SB in 92 and during CMV in 73 patients. Follow-up was carried out after 3 ± 5 and 36 ± 53 days. Functional lead parameters (FLP; pacing threshold and impedance), postoperative adverse events (A;  phrenic nerve stimulation [PNS] and lead malfunction), and patients' BMI were assessed. Delta values of FLP between baseline and follow-up visits were analyzed applying an analysis of covariance model to detect subclinical alterations in LV lead function.

RESULTS

AE occurred in a total of 36 (21%) patients. PNS was observed in 26 (15%) patients and LV lead repositioning due to malfunction was necessary in 10 (6%) patients. Both AE and FLP delta values between baseline and follow-up were not associated with intraoperative ventilation settings nor the patients' BMI.

CONCLUSIONS

This study demonstrates that there is no impact of the intraoperative ventilation setting (SB vs CMV) on postoperative FLP or the occurrence of AE. This is also the case taking into account the BMI. With respect to these findings both approaches-sedation only or general anaesthesia including CMV-can be safely implemented during CRT implantation.

A comparison of the different features of quadripolar left ventricular pacing leads to deliver cardiac resynchronization therapy

INTRODUCTION

Cardiac Resynchronization therapy (CRT) improves the quality of life and reduces morbidity and mortality of certain patients with heart failure. However, not all patients respond positively after CRT and about one third of cases do not experience benefit. Suboptimal biventricular pacing may account for this and quadripolar left ventricular (LV) leads have emerged in the last years to address issues relating to inadequate delivery of CRT.

AREAS COVERED

This review article concisely summarizes the main technical characteristics of the quadripolar LV leads either currently available in the market today or under final stages of development. Focus is given in recent advancements in the area and challenging aspects and controversies, future implications as well as opportunities for further development.

EXPERT COMMENTARY

Quadripolar LV pacing leads have now become the standard of care in CRT. Currently a multitude of lead options is available to the clinician. The selection process of the most appropriate lead is far from the 'one size fits all' concept. Further development of quadripolar LV leads is currently ongoing and it is anticipated to contribute towards the release of more technologically advantageous leads which will enable the delivery of optimal CRT therapy with the lowest rate of complications.

Minimal Invasive Left Ventricular Lead Repositioning is Safe and Effective in Distal Left Ventricular Lead Positions

BACKGROUND

Treatment of left ventricular electrode dislocation and phrenic nerve stimulation remains an issue in the era of new electrode designs.

METHODS

Safety and efficacy of minimal invasive lead repositioning and pocket opening reposition procedures were evaluated between December 2005 and December 2012 at our center. Minimal invasive method was developed and widely utilized at our center to treat phrenic nerve stimulation. The distally positioned left ventricular lead is looped around by a deflectable catheter in the right atrium introduced from the femoral vein access and then pulled back. Coronary stent implantation was used afterwards for lead stabilization in some patients.

RESULTS

42 minimal invasive and 48 electrode repositions with pacemaker pocket opening were performed at 77 patients for left ventricular lead problems. Minimal invasive reposition could be carried out successfully in 69% of (29 patients) cases. Note that in 14.3% of the cases (six patients) minimal invasive procedures were acutely unsuccessful and crossover was necessary. In 16.6% of the cases (seven patients) lead issues were noted later during follow-up. Opening of the pocket could be carried out successfully in 81.2% (39 patients) and was unsuccessful acutely in 6.25% (three patients). Repeated dislocation was noticed, 12.5%, in this group (six patients). Complication during minimal invasive procedures was electrode injury in one case. Pocket openings were associated with several complications: atrial fibrillation, pericardial effusion, fever, hematoma, and right ventricular electrode dislodgement.

CONCLUSION

Minimal invasive procedure-as the first line approach-is safe and feasible for left ventricular electrode repositioning in selected cases.

A Meta-Analysis Of Quadripolar Versus Bipolar Left Ventricular Leads On Post-Procedural Outcomes

Objective: We aimed to perform a meta-analysis from eligible studies to analyze the true impact of QL when compared with BL with regard to post-procedural outcomes including lead deactivation, revision or replacement. Background: Many observational and retrospective studies showed that quadripolar left ventricular leads (QL) are associated with better outcomes and fewer complications when compared with bipolar leads (BL). Methods: We performed a comprehensive literature search through June 30, 2015 using: quadripolar, bipolar, left ventricular lead and CRT in Pubmed, Ebsco and google scholar databases. Results: The analysis included 8 studies comparing QL and BL implantation. Post-procedural outcomes such as lead deactivation, revision or replacement were used as primary outcome and assessed with Mantel-Haenszel risk ratio (RR). Secondary outcomes included total fluoroscopy/procedure time, occurrence of phrenic nerve stimulation (PNS) and all-cause mortality on follow up. Follow-up duration for the studies ranged from 3 to 60 months. Compared with BL, the use of QL is associated with 52 % reduction (relative risk 0.48; 95% CI: 0.36-0.64, p=0.00001) in the risk of deactivation, revision or replacement of the LV lead. QL had significantly lower fluoroscopy/procedure time, PNS and all-cause mortality when compared with BL. Conclusion:Our meta-analysis shows that QL implantation was associated with decreased risk of LV lead deactivation, revision or replacement when compared with BL.

Bipolar left ventricular pacing is associated with significant reduction in heart failure or death in CRT-D patients with LBBB

BACKGROUND

There are limited data on the significance of left ventricular (LV) lead pacing polarity to predict clinical outcomes.

OBJECTIVES

We aimed to determine the association between the LV lead pacing polarity for heart failure (HF) or death and ventricular tachyarrhythmias (VTA) in patients enrolled in MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy), receiving a cardiac resynchronization therapy device with implanted cardioverter-defibrillator (CRT-D).

METHODS

We retrospectively analyzed LV pacing polarity. Patients with LV bipolar leads paced between LV ring and LV tip were identified as True Bipolar, while those with LV bipolar leads paced between LV tip or LV ring and right ventricular coil or unipolar leads were identified as Unipolar/Extended Bipolar. Kaplan-Meier survival analyses and multivariate Cox proportional hazards regression models were used.

RESULTS

Of the 969 patients, 421 had True Bipolar pacing while the remainder (n = 548) had Unipolar/Extended Bipolar pacing. Among patients with left bundle branch block (LBBB), True Bipolar pacing was associated with lower cumulative incidence of death (P = .022) and HF/death (P = .046) compared to those with Unipolar/Extended Bipolar LV pacing. After adjustment for clinical covariates, bipolar LV pacing in LBBB patients was associated with 54% lower risk for death (HR: 0.46; 95% CI: 0.24-0.88; P = .020) and 32% lower risk for HF/death (HR: 0.68; 95% CI: 0.46-1.00; P = .048) compared to Unipolar/Extended Bipolar LV pacing, but not in those with non-LBBB. No association was seen with risk of ventricular tachyarrhythmia.

CONCLUSION

True Bipolar LV pacing configuration is associated with a significantly lower risk of HF/death and all-cause mortality in CRT-D patients with LBBB.

A Case of Useful Short-Spaced Bipolar Pacing of a Left Ventricular Lead to Avoid Phrenic Nerve Stimulation

A 48-year-old woman underwent cardiac resynchronization therapy defibrillator implantation. Coronary sinus (CS) venography showed only one adequate anterior branch for a left ventricular lead. We were able to introduce a quadripolar left ventricular lead (Medtronic 4398-88 cm) to the distal portion of the anterior branch. Although phrenic nerve stimulation (PNS) occurred due to distal bipolar pacing (distal 1-mid 2, with 21-mm distance) and proximal pacing (mid 3-proximal 4, distance 21mm), short-spaced bipolar pacing (mid 2-3, distance 1.3 mm) did not induce PNS until 9V pacing. Shared bipolar pacing from each left ventricular electrode (distal 1 to proximal 4) as cathode and a right ventricular (RV) coil as anode resulted in PNS by 3.0V at 0.4 ms. Although quadripolar pacing could avoid PNS by switching the pacing site (ie, from distal bipolar to proximal bipolar), it might not avoid PNS in cases where the phrenic nerve and CS branch are parallel and in close proximity. We found that even though the phrenic nerve and CS branch were parallel and close, short-spaced bipolar pacing could avoid PNS. In conclusion, short-spaced bipolar pacing selected by quadripolar pacing might be beneficial to avoid PNS when the implantable branch is limited.

Active fixation of a thin transvenous left-ventricular lead by a side helix facilitates targeted and stable placement in cardiac resynchronization therapy

AIMS

Suboptimal placement, phrenic nerve stimulation, and dislodgements of left-ventricular (LV) leads are main challenges in cardiac resynchronization therapy. We investigated the handling, performance, safety, and stability for a novel 4Fr LV lead with a small side helix located proximal to the ring electrode for active fixation of the LV lead.

METHODS AND RESULTS

The novel LV lead was successfully implanted in 103 of 106 patients. Patients with dislodged LV leads and with demanding coronary vein anatomies were included. The lead body was rotated clockwise to engage the active fixation side helix in the vein wall. The stimulating electrode was located in basal LV segment and middle LV segment in 54 and 46% of the patients, respectively. The lead was targeted to a vein concordant to the LV segment with latest mechanical activation. Concordant LV lead placement was achieved in 73% of the patients and in adjacent segment in 24%. The average pacing capture threshold (PCT) at implantation was 1.04 ± 0.6 V (n = 103) and at an average follow-up at 7 months, the PCT remained low and no dislodgements have been observed. During follow-up, four leads have been explanted without complications.

CONCLUSION

Active fixation of this 4Fr LV lead by using a side helix, offers flexibility to place the lead precisely in targeted vein segments over a wide range of vein anatomies. The average LV pacing threshold was low at implantation and follow-ups. The lead seems to be extractable and no late dislodgements have been observed.

Percutaneous Epicardial Pacing using a Novel Insulated Multi-electrode Lead

INTRODUCTION

Epicardial cardiac resynchronization therapy (CRT) permits unrestricted electrode positioning. However, this requires surgical placement of device leads and the risk of unwanted phrenic nerve stimulation. We hypothesized that shielded electrodes can capture myocardium without extracardiac stimulation.

METHODS

In 6 dog and 5 swine experiments, we used a percutaneous approach to access the epicardial surface of the heart, and deploy novel leads housing multiple electrodes with selective insulation. Bipolar pacing thresholds at prespecified sites were tested compare electrode threshold data both facing towards and away from the epicardial surface.

RESULTS

In 151 paired electrode recordings (70 in 6 dogs; 81 in 5 swine), thresholds facing myocardium were lower than facing away (median [IQR] mA: dogs 0.9 [0.4-1.6] vs 4.6 [2.1 to >10], p<0.0001; swine 0.5 [0.2-1] vs 2.5 [0.5-6.8], p<0.0001). Myocardial capture was feasible without extracardiac stimulation at all tested sites, with mean ± SE threshold margin 3.6±0.7 mA at sites of high output extracardiac stimulation (p=0.004).

CONCLUSION

Selective electrode insulation confers directional pacing to a multielectrode epicardial pacing lead. This device has the potential for a novel percutaneous epicardial resynchronization therapy that permits placement at an optimal pacing site, irrespective of the anatomy of the coronary veins or phrenic nerves.

Cardiac Resynchronization Therapy Delivered Via a Multipolar Left Ventricular Lead is Associated with Reduced Mortality and Elimination of Phrenic Nerve Stimulation: Long-Term Follow-Up from a Multicenter Registry

INTRODUCTION

Cardiac resynchronization therapy (CRT) using quadripolar left ventricular (LV) leads provides more pacing vectors compared to bipolar leads. This may avoid phrenic nerve stimulation (PNS) and allow optimal lead placement to maximize biventricular pacing. However, a long-term improvement in patient outcome has yet to be demonstrated.

METHODS

A total of 721 consecutive patients with conventional CRTD criteria implanted with quadripolar (n = 357) or bipolar (n = 364) LV leads were enrolled into a registry at 3 UK centers. Lead performance and mortality was analyzed over a 5-year period.

RESULTS

Patients receiving a quadripolar lead were of similar age and sex to those receiving a bipolar lead, although a lower proportion had ischemic heart disease (62.6% vs. 54.1%, P = 0.02). Both groups had similar rates of procedural success, although lead threshold, impedance, and procedural radiation dose were significantly lower in those receiving a quadripolar lead. PNS was more common in those with quadripolar leads (16.0% vs. 11.6%, P = 0.08), but was eliminated by switching pacing vector in all cases compared with 60% in the bipolar group (P < 0.001). Furthermore, LV lead displacement (1.7% vs. 4.6%, P = 0.03) and repositioning (2.0% vs. 5.2%, P = 0.03) occurred significantly less often in those with a quadripolar lead. All-cause mortality was also significantly lower in the quadripolar compared to bipolar lead group in univariate and multivariate analysis (13.2% vs. 22.5%, P < 0.001).

CONCLUSIONS

In a large, multicenter experience, the use of quadripolar LV leads for CRT was associated with elimination of PNS and lower overall mortality. This has important implications for LV pacing lead choice.

Left ventricular three-dimensional quadripolar lead acute clinical study: the LILAC study

AIMS

This multicenter acute clinical study was designed to verify novel three-dimensional (3D) quadripolar lead designs that can achieve ≤2.5 V average pacing capture threshold (PCT) not only at the apex, but also at the base of the left ventricle with phrenic nerve stimulation (PNS) avoidance for cardiac resynchronization.

METHODS

During the implant procedure, up to two different left ventricular investigational leads were introduced and tested in the same target coronary vein based on the coronary sinus venogram in a wedged and unwedged position. Adverse events were collected in 30 days following the procedure.

RESULTS

Eighty-seven leads were tested in 50 patients. When the best performing spiral electrode was chosen from each lead testing, the average of the best PCT on spiral in a wedged position was similar to the unwedged position (1.7 ± 1.5 V vs 1.9 ± 1.5 V, P = ns) and was similar to the wedged tip electrode average PCT (1.7 ± 1.5 V vs 1.6 ± 1.6 V, P = ns). In the majority of patients (89-96%), pacing was achievable in a mid-basal ventricular location without PNS.

CONCLUSIONS

This acute study demonstrated that a 3D quadripolar spiral lead design can achieve acceptable PCTs and avoid PNS without repositioning the lead at implant in the vast majority of patients. It also demonstrated that this lead design can achieve mid-basal ventricular stimulation with low PCT and good acute stability.

Right ventricular septal pacing as alternative for failed left ventricular lead implantation in cardiac resynchronization therapy candidates

AIMS

To compare the effects on left ventricular (LV) function of right ventricular (RV) septal pacing vs. cardiac resynchronization therapy (CRT) in patients with an indication for the latter. Cardiac resynchronization therapy is an effective therapy in patients with drug-refractory heart failure. Despite advances in implantation techniques, LV lead placement can be impossible in up to 10% of cases. We, therefore, assessed the effects of RV septal pacing from mid septum (RVmIVS) and outflow tract (RVOT) on cardiac performance, in comparison with CRT.

METHODS AND RESULTS

Twenty-two patients scheduled for CRT underwent dual-chamber temporary pacing. The ventricular lead was placed at the RV apex (RVA), RVmIVS, and RVOT in random order. Comprehensive echocardiography was performed in a baseline AAI mode and then at each RV position in dual chamber pacemaker function (D pacing, D sensing, D dual responses) mode and repeated on the next day following CRT implantation. Right ventricular apex pacing did not change any of the assessed echocardiography parameters. Both RVmIVS and RVOT pacing increased LV ejection fraction (EF): 29 ± 7% at baseline vs. 32 ± 6% (P = 0.02) and 32 ± 5% (P = 0.04) with RVmIVS and RVOT pacing, respectively. Similarly, the dyssynchrony index (Ts-SD) decreased: 50 ± 19 ms at baseline vs. 39 ± 17 ms (P = 0.04) and 37 ± 17 ms (P = 0.006) with RVmIVS and RVOT pacing, respectively. Cardiac resynchronization therapy further improved LVEF and Ts-SD to 36 ± 7% and 34 ± 15 ms, respectively, however, only LVEF was significantly higher compared with RVmIVS and RVOT pacing (P = 0.03 and P = 0.01 respectively). There were no significant differences in either LVEF or Ts-SD between RVmIVS and RVOT.

CONCLUSION

Right ventricular septal pacing from mid septum or RVOT pacing improves LVEF and LV synchrony in CRT candidates. Further improvement in LVEF was achieved by CRT, which remains the 'gold standard' therapy in these patients. However, RV septal pacing is worthy of further study as an alternative strategy when LV lead implantation fails.

Multisite left ventricular pacing in cardiac resynchronization therapy

Cardiac resynchronization therapy is an effective treatment for selected patients with heart failure and left bundle branch block dyssynchrony. Unfortunately, about a third of patients, so-called nonresponders, do not display any symptomatic or structural improvements after the treatment. In another 5% of patients, the left ventricular lead cannot be implanted due to technical limitations. Novel quadripolar pacing lead and associated multisite pacing technology has the potential to help improve both of these problems. The technology and applications of these leads are reviewed and the novel technique of multisite pacing from two poles of one quadripolar lead is discussed. This technology may improve response to cardiac resynchronization therapy for some patients.