Right Ventricular Outflow Tract Placement of Defibrillation Leads:. Five Year Experience

Apical versus Non-Apical Lead: Is ICD Lead Position Important for Successful Defibrillation?

INTRODUCTION

We aim to compare the acute and long-term success of defibrillation between non-apical and apical ICD lead position.

METHODS AND RESULTS

The position of the ventricular lead was recorded by the implanting physician for 2,475 of 2,500 subjects in the Shockless IMPLant Evaluation (SIMPLE) trial, and subjects were grouped accordingly as non-apical or apical. The success of intra-operative defibrillation testing and of subsequent clinical shocks were compared. Propensity scoring was used to adjust for the impact of differences in baseline variables between these groups. There were 541 leads that were implanted at a non-apical position (21.9%). Patients implanted with a non-apical lead had a higher rate of secondary prevention indication. Non-apical location resulted in a lower mean R-wave amplitude (14.0 vs. 15.2, P < 0.001), lower mean pacing impedance (662 ohm vs. 728 ohm, P < 0.001), and higher mean pacing threshold (0.70 V vs. 0.66 V, P = 0.01). Single-coil leads and cardiac resynchronization devices were used more often in non-apical implants. The success of intra-operative defibrillation was similar between propensity score matched groups (89%). Over a mean follow-up of 3 years, there were no significant differences in the yearly rates of appropriate shock (5.5% vs. 5.4%, P = 0.98), failed appropriate first shock (0.9% vs. 1.0%, P = 0.66), or the composite of failed shock or arrhythmic death (2.8% vs. 2.3% P = 0.35) according to lead location.

CONCLUSION

We did not detect any reduction in the ICD efficacy at the time of implant or during follow-up in patients receiving a non-apical RV lead.

[ICD leads]

Implantable cardioverter-defibrillator (ICD) leads have to fulfill particular requirements: safe pacing and sensing, detection, and termination of ventricular tachyarrhythmias, if necessary by (multiple) high-energy shocks. At the same time, their implantation has to be simple, they need to provide excellent long-term stability and they must be completely and safely extractable. Numerous technical developments have enabled currently available ICD leads to fulfill these expectations to a high extent. However, some changes of lead design, materials, and manufacturing processes have led to increased lead failure, especially in two lead models (Medtronic Sprint Fidelis®, St. Jude Medical Riata®). The high rate of lead failure was identified only several years after market release, in part because there are no appropriate registries of ICD leads. This review presents background and developments of ICD lead technology and their association with the clinical usage of ICD therapy. To also benefit patients with only slightly-to-moderately increased risk of ventricular tachyarrhythmia, optimum ICD therapy requires optimal leads and sufficiently experienced implanters.

Pacing the right ventricular outflow tract septum: time to embrace the future

Transvenous pacing has revolutionized the management of patients with potentially life-threatening bradycardias and at its most basic level ensures rate support to maintain cardiac output. However, we have known for at least a decade that pacing from the right ventricle (RV) apex can induce left ventricle (LV) dysfunction, atrial fibrillation, heart failure, and maybe an increased mortality. Although pacemaker manufacturers have developed successful pacing algorithms designed to minimize unnecessary ventricular pacing, it cannot be avoided in a substantial proportion of pacemaker-dependent patients. Just as there is undoubted evidence that RV apical pacing is injurious, there is emerging evidence that pacing from the RV septum is associated with a shorter duration of activation, improved haemodynamics, and less LV remodelling. The move from traditional RV apical pacing to RV septal pacing requires a change in mindset for many practitioners. The anatomical landmarks and electrocardiograph features of RV septal pacing are well described and easily recognized. While active fixation is required to place the lead on the septum, shaped stylets are now available to assist the implanter. In addition, concerns about the stability and longevity of steroid-eluting active fixation leads have proven to be unfounded. We therefore encourage all implanters to adopt RV septal pacing to minimize the potential of harm to their patients.

An observational registry on efficacy and safety of the right ventricular outflow tract as a site for ICD leads: results of the EFFORT (EFFicacy Of Right ventricular outflow Tract as site for ICD leads) registry

BACKGROUND

Although pacing from the right ventricular outflow tract (RVOT) has been shown to be safe and feasible in terms of sensing and pacing thresholds, its use as a site for implantable cardioverter defibrillator (ICD) leads is not common. This is probably due to physicians' concerns about defibrillation efficacy. To date, only one randomized trial, involving 87 enrolled patients, has evaluated this issue.

OBJECTIVE

The aim of this observational study has been to compare safety (primary combined end point: efficacy of a 14-J shock in restoring sinus rhythm, R wave amplitude >4 mV and pacing threshold <1 V at 0.5 ms) and efficacy (in terms of effectiveness of a 14-J shock in restoring sinus rhythm after induction of VF, secondary end point) of two different sites for ICD lead positioning: RVOT and right ventricular apex (RVA).

METHODS

The study involved 185 patients (153 males; aged 67 ± 10 years; range, 28-82 years). Site of implant was left to physician's decision. After implant, VF was induced with a 1-J shock over the T wave or--if this method was ineffective--with a 50-Hz burst, and a 14-J shock was tested in order to restore sinus rhythm. If this energy was ineffective, a second shock at 21 J was administered and--eventually--a 31-J shock followed--in case of inefficacy--by a 360-J biphasic external DC shock. Sensing and pacing thresholds were recorded in the database at implant, together with acute (within 3 days of implant) dislodgement rate.

RESULTS

The combined primary end point was reached in 57 patients in the RVOT group (0.70%) and in 81 patients in the RVA group (0.79%). The 14-J shock was effective in 159 patients, 63 in the RVOT group (77%) and 86 in the RVA group (83%). Both the primary and the secondary end points are not statistically different. R wave amplitude was significantly lower in the RVOT group (10.9 ± 5.2 mV vs. 15.6 ± 6.4 mV, p < 0.0001), and pacing threshold at 0.5 ms was significantly higher (0.64 ± 0.25 V vs. 0.52 ± 0.20 V, p < 0.01), but these differences do not seem to have a clinical meaning, given that the lower values are well above the accepted limits in clinical practice.

CONCLUSIONS

Efficacy and safety of ICD lead positioning in RVOT is comparable to RVA. Even if we observed statistically significant differences in sensing and pacing threshold, the clinical meaning of these differences is--in our opinion--irrelevant.

Delayed cardiac perforation by defibrillator lead placed in the right ventricular outflow tract resulting in massive pericardial effusion

A 76-year-old man received a dual-chamber implantable cardioverter defibrillator (ICD), with the defibrillator lead positioned within the right ventricular outflow tract. The lead parameters at the time of implantation were satisfactory and the post-procedure chest X-ray showed the leads were in place. The patient was cardioverted from atrial fibrillation during defibrillation threshold testing and commenced on anticoagulation immediately. One month post implantation, he experienced multiple ventricular tachycardia episodes all successfully treated with antitachycardia pacing and shocks by his ICD, but he fell and hit his chest against a hard surface during one of these attacks. He developed a massive pericardial effusion and computed tomography confirmed cardiac perforation by the defibrillator lead. Pericardiocentesis was performed and the defibrillator lead replaced with a different model positioned at the right ventricular apex. The patient made an uneventful recovery. The management and avoidance of delayed cardiac perforation by transvenous leads were discussed.

Right ventricular outflow tract pacing: practical and beneficial. A 9-year experience of 460 consecutive implants

BACKGROUND

Pacing from the right ventricular apex (RVA) in patients with ventricular dysfunction has been identified as a possible contributor to deterioration of ventricular function. Therefore, alternative pacing sites such as the right ventricular outflow tract (RVOT) are receiving intensified scrutiny. An unresolved question is whether technical, procedural, and stability issues are comparable for the RVA and the RVOT.

METHODS

This report details 460 consecutive ventricular pacing lead implants with the primary intended site in the RVOT. Patients were evaluated for success, complication rates, and followed-up for stability of pacing parameters. The total patient implant population included 300 male and 170 female patients with a mean age of 70.6 years. Ten patients were excluded from the analysis, since there was a primary indication and intention to implant in the RVA, leaving a total of 460 patients for analysis. The indications for pacing were symptomatic bradycardia due to any cause and/or Mobitz II or complete heart block. There was no clinical evidence of heart failure in 420 patients. In 40 patients with heart failure, the indication for pacing was cardiac resynchronization therapy using the RVOT as an alternate site when pacing from a branch vein of the coronary sinus was not possible. Outcome information was obtained from the implanter's clinic.

RESULTS

The overall success rate in the RVOT was 84% over the total 9-year period with a 92% success rate in the last 4(1/2) years, using the RVOT technique described. At 20 months in a subgroup comparison of RVOT and RVA implants, there was no significant difference in pacing threshold, R-wave sensing, or pacing lead impedance. Dislodgment occurred in only 1 of 460 patients. Reasons for failure to implant in the RVOT include inability to find a stable position with adequate pacing and sensing thresholds (related to anatomy, scarred myocardium, pulmonary hypertension, tricuspid regurgitation), hemodynamic instability limiting time for implant, and a learning curve. Long-term stability and lead performance were excellent, and certain acute and chronic complications of RV pacing did not occur.

Lead Interaction: Rare Cause of Oversensing During Implantation Procedure of Implantable Cardioverter-Defibrillator System

A variety of etiologies can cause erroneous detection in patients with implantable cardioverter defibrillator (ICDs). Interaction between two endocardial leads is rare and uncommon in causing electrical noise. During a reimplantation procedure of an ICD system in a 68-year-old man, additional electrical signals could be detected. The interaction between two endocardial defibrillation leads was identified as the cause of sensing problems. When it is not possible to extract the nonfunctional endocardial lead during implantation of the new electrode, it should be implanted away and not in parallel from the old one to avoid interaction between them. A variety of etiologies can cause erroneous detection in patiens with ICD. Interaction between two endocardial leads is rare and uncommon to cause electrical noise.

The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing

BACKGROUND

The purpose of this article is to critically review the data accumulated to date from studies evaluating the hemodynamic and clinical effects of right ventricular apical pacing during conventional permanent cardiac pacing. The data from studies comparing the effects of right ventricular apical pacing and alternate site ventricular pacing are also reviewed.

METHODS

We conducted a MEDLINE and journal search of English-language reports published in the last decade and searched relevant papers.

RESULTS

Although intraventricular conduction delay in the form of left bundle branch block (LBBB) has traditionally been viewed as an electrophysiologic abnormality, it has now become abundantly clear that it has profound hemodynamic effects due to ventricular dyssynchrony, especially in patients with heart failure. These deleterious effects can be significantly ameliorated by cardiac resynchronization therapy effected by biventricular or left ventricular pacing. However, not only is spontaneous LBBB harmful, but the iatrogenic variety produced by right ventricular apical pacing in patients with permanent pacemakers may be equally deleterious. In this review new evidence from recent studies is presented, which strongly suggests a harmful effect of our long-standing practice of producing an iatrogenic LBBB by conventional right ventricular apical pacing in patients receiving permanent pacemakers. This emerging strong new evidence about the adverse hemodynamic and clinical effects of right ventricular apical pacing would dictate a reassessment of our traditional approach to permanent cardiac pacing and direct our attention to alternate sites of pacing, such as the left ventricle and/or the right ventricular outflow tract or septum, if not for all patients, at least for those with left ventricular dysfunction. Indeed, current convincing data on alternate site ventricular pacing are encouraging and this approach should be actively pursued and further investigated in future studies.

CONCLUSIONS

Not only is spontaneous permanent LBBB harmful to our patients, but the iatrogenic variety produced by right ventricular apical pacing during conventional permanent pacing may also be deleterious to some patients. The compelling evidence presented herein cannot be ignored; it may dictate a change of attitude toward right ventricular apical pacing directing our attention to alternate sites of ventricular pacing and avoidance of the right ventricular apex.