REVIEW URRENT C OPINION

Advanced left-ventricular lead placement techniques for cardiac resynchronization therapy Jaimie Manlucu and Raymond Yee

Purpose of review Due to complex venous anatomy and limitations in lead delivery tools and technology, the incidence of failed left-ventricular lead implants continues to be as high as 10%. Recent findings A move towards an interventional approach to left-ventricular lead implantation has provided viable alternatives to surgical lead implantation. The use of telescoping sheaths, gooseneck snares and percutaneous balloon venoplasty may reduce procedural times by facilitating lead delivery despite challenging venous anatomy. In addition, recent advancements in left-ventricular lead technology now allow implanting physicians to overcome commonly encountered obstacles such as high thresholds and phrenic nerve stimulation, without having to move the lead from a stable position. For those with suboptimal or inaccessible coronary vein targets, a simplified transseptal endocardial implant approach has also been described. Summary These recent advances in implant techniques and left-ventricular lead technology provide promising solutions to commonly encountered procedural obstacles in the implementation of resynchronization therapy. These alternative strategies will hopefully reduce the rate of failed implants and referrals for surgical epicardial leads. Keywords lead technology, left-ventricular lead implant techniques, snare, transseptal, venoplasty

INTRODUCTION One of the central themes of research in this second decade of cardiac resynchronization therapy (CRT) is the development of tools that will maximize the clinical response rate to this treatment. However clinical response is defined, it is clear that the response rate is less than desired. Failure to respond includes situations in which left-ventricular pacing is not possible because the coronary venous anatomy prevents delivery or maintenance of a functional leftventricular lead at the intended site. Where the left-ventricular lead is successfully positioned but causes intolerable side effects such as phrenic nerve or direct diaphragmatic muscle stimulation, resynchronization therapy may also fail to achieve its goal. This review focuses on recent technical advances and developments in lead delivery techniques and left-ventricular lead technology.

INTERVENTIONAL APPROACH TO LEFTVENTRICULAR LEAD IMPLANTS Current standard practice for left-ventricular lead implantation in many institutions includes an overthe-wire technique. The procedure begins with cannulation of the coronary sinus by a long sheath aided by a diagnostic electrophysiology catheter or 0.035-inch introducer wire. This is followed by performance of occlusive coronary sinus venography to identify the appropriate target vein(s). An 0.014-inch angioplasty wire is then advanced through the sheath to probe for the target branches, London Health Sciences Center & University of Western Ontario, London, Ontario, Canada Correspondence to Jaimie Manlucu, MD, FRCP(C), 339 Windermere Road, Room B6-129B, London, ON N6A 5A5, Canada. Tel: +1 519 663 3846; fax: +1 519 663 3782; e-mail: [email protected] Curr Opin Cardiol 2014, 29:53–58 DOI:10.1097/HCO.0000000000000028

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KEY POINTS  An interventional approach to left-ventricular implants, emphasizing a more liberalized use of catheter-based techniques and a more liberal use of contrast, may reduce procedural time and fluoroscopic exposure and increase success rates.  Percutaneous venoplasty and snares are useful techniques to overcome both venous tortuosity and stenosis.

target vein and deliver the left-ventricular lead over an 0.014-inch angioplasty wire. In comparison to the standard over-thewire technique, telescoping sheath techniques may allow more efficient targeted left-ventricular lead placement, resulting in shorter procedure times, less fluoroscopy exposure and increased optimal lead position. This comes at a cost of slightly higher contrast volumes, which does not translate to higher adverse clinical outcomes if patients are properly pretreated [3 ]. &

 New lead technology may allow operators to easily overcome situations with phrenic nerve stimulation, elevated thresholds and lead stability without requiring lead repositioning.  The transseptal endocardial approach to left-ventricular lead implants is a safe alternative for patients without appropriate coronary venous anatomy.

with or without the support of a preshaped subselection sheath. Once the wire reaches a distal and stable point in the vein, the left-ventricular lead is advanced over the wire into the desired position. Although this approach is often successful, anatomic variations exist that can make it challenging. Distortion of cardiac anatomy from heart failure and chamber enlargement can result in unusually situated coronary sinus ostia and/or extreme angulation of the coronary sinus body, which can make coronary sinus cannulation problematic. Tortuous veins and/or obstructive valves can also complicate a procedure by hindering wire and/or lead advancement. In certain circumstances, even if a wire will advance easily into a vein, it may not provide enough support to advance the lead into position. These factors account for a significant portion of failed left-ventricular lead implants [1,2].

Telescoping sheaths In order to overcome some of these obstacles, many centers have chosen to adopt a more ‘interventional approach’ to left-ventricular lead placement. This method is modeled after the approach used by our colleagues in interventional cardiology, which emphasizes more catheter-based techniques and a more liberal use of contrast. In lieu of the 0.035-inch guidewire, the coronary sinus ostium is identified with puffs of contrast dye through a braided coronary sinus catheter, which is used to guide a longer 9FR sheath into the coronary sinus body. Following an occlusive venogram, the target branch is cannulated with a two-component, telescoping-support delivery sheath system consisting of an inner target vein selector and a delivery guide shaped to fit into the 54

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Venoplasty The need for device upgrades and revisions continues to rise with the increasing life expectancy of those with heart failure and cardiovascular disease. The prevalence of venous stenosis parallels this growth, occurring anywhere from the subclavian (SCV) or axillary vein to the coronary sinus and its tributaries. In patients with pre-existing devices, the incidence of asymptomatic ipsilateral SCV stenosis or occlusion has been reported to be as high as 13–35%. The prevalence of coronary vein stenosis that prevents proper left-ventricular lead placement is estimated at 10–15% [4]. This is about equal to the estimated proportion of CRT patients undergoing surgical epicardial lead implants [5]. A growing interest in percutaneous venoplasty amongst implanting physicians provides an effective alternative to surgery. Facilitation of leftventricular lead implant with percutaneous balloon venoplasty has been described in a number of small case series. In a recent review of the literature, 3.7% of 1561 patients reported vein stenosis. The success rate of venoplasty in this cohort was 95.5%; 0.5% of these underwent venoplasty for obstructive venous valves, which were 100% successful [6]. However, venoplasty can be quite challenging, and is not without risk. Excessive balloon dilatation and/or balloon malpositioning can lead to vein rupture, cardiac tamponade or inadvertent myocardial dilatation, particularly in patients without prior cardiac surgery. The main impediment to the routine use of venoplasty is access to appropriate technical training and supervision. Many have chosen to partner with an experienced interventional cardiologist.

Snares The use of snares is particularly useful in addressing the problem of tortuous coronary veins, where an angioplasty wire is able to advance deep into the vein, but does not provide sufficient support to facilitate lead advancement. The snare technique Volume 29  Number 1  January 2014

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Left-ventricular lead placement techniques Manlucu and Yee

capitalizes on the presence of venous collaterals. The initial angioplasty wire is inserted anterogradely into the tortuous target vessel and advanced distally through distal collateral veins, and emerges retrogradely back into the coronary sinus body. A standard gooseneck snare, advanced through the guide sheath into the coronary sinus body, captures and stabilizes the distal tip of the wire, giving the operator full control of both ends of the wire. The left-ventricular lead can then be advanced antegradely over the wire (‘orthodromically’) (Fig. 1). Alternatively, the snare and captured distal end of the wire can be drawn all the way out of the sheath. The snare is then removed and the leftventricular lead advanced over the soft distal end of the wire (‘antidromically’) into the collateral vein branch. If the collateral vein is of large caliber or if venoplasty is performed, it might even be possible to advance the lead retrogradely all the way into the target vessel. There have been a number of small case series demonstrating the safety and efficacy of the snare technique [7,8]. Unlike venoplasty, the snare technique does not require much extra training and can be easily performed by most implanting physicians. Unfortunately, it is only possible in cases where appropriate collateral veins are present. Applying an interventional approach to device implantation has the potential to safely reduce implant time, reduce the rate of failed procedures, reduce the need for tunneling and extraction procedures, and improve optimal lead positioning. However, as discussed previously, the interventional approach does require a more liberal use of contrast, which has raised some concerns. However, as long as patients are appropriately hydrated and pretreated with N-acetylcysteine and sodium bicarbonate an hour before contrast exposure, it has been shown that contrast nephropathy can be avoided in most high-risk patients without increasing the risk of congestive heart failure [9].

NEW LEFT-VENTRICULAR LEAD TECHNOLOGY There are several challenges to a successful leftventricular lead implant that remain after a lead is advanced into a target vein. Recent advances in left-ventricular lead technology have been directed at overcoming commonly encountered hurdles such as elevated thresholds, lead stability/dislodgement and phrenic nerve stimulation.

Multipolar leads Multipolar leads have been developed by many of the major device companies, with the hope that the

FIGURE 1. Implantation of an left-ventricular lead using a gooseneck snare in a case where only an angioplasty wire would advance beyond the valve of Vieussens. A wire was advanced into an anterolateral branch, through collaterals retrograde into the coronary sinus via a posterolateral branch, where the distal tip was snared. The lead was then easily railed over the wire orthodromically into a stable midventricular anterolateral position. This figure shows a right (a) and left anterior oblique (b) projection of the final leftventricular lead position; the angioplasty wire can be seen exiting the tip of the lead traveling through collaterals back into the coronary sinus sheath.

versatility of these leads will mitigate some of these issues. For example, the larger number of potential pacing vectors allows an operator to overcome unacceptably high thresholds or phrenic nerve stimulation without having to reposition the lead.

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Moreover, the larger number of potential pacing vectors may also enable operators to titrate CRT therapy to optimize an individual’s potential to respond. The Quartet lead (Model 1458Q, St. Jude Medical, St Paul, MN), one of the first quadripolar left-ventricular leads, offers 10 different pacing vectors. The widely spaced four electrodes span a greater distance (47 mm) than conventional bipolar leads. Early reports indicate electrical performance was good, implant success was high, but lead dislodgement still occurred, albeit infrequently. Alternate pacing vectors were able to eliminate phrenic nerve stimulation in the small proportion of patients who were affected [10]. Another quadripolar lead currently under clinical investigation has the added potential to avoid phrenic stimulation using two closely spaced bipoles. This is based on a study that looked at the effect of interelectrode distance on phrenic nerve thresholds using a 5FR decapolar diagnostic catheter with 2-5-2 mm electrode spacing. In this study, the average phrenic nerve threshold increased with shorter electrode spacing (2 mm), without affecting the left-ventricular pacing threshold. When a 2 mm bipole was placed between 5 and 25 mm from the site with the lowest phrenic nerve threshold, phrenic nerve stimulation was avoided in 80–100% of the cases, with no effect on left-ventricular pacing thresholds [11].

Active fixation left-ventricular leads Some coronary veins, particularly those of large caliber with few side branches, are easy to cannulate, but the lead is often unstable. Several strategies have been employed to try to stabilize the lead. The first is to wedge the lead tip distally or into a smaller branch vein. The quadripolar lead would lend itself to such a strategy since pacing from the proximal electrodes would avoid pacing too near the leftventricular apex. Another approach has been the off-label use of a right heart pacing lead with an active fixation helix (retractable or fixed) in the coronary vein. Yet another approach is to retain a delivery stylet in the lumen to stiffen the lead body, but this is not recommended and may result in premature loss of lead integrity and complications. The first active fixation left-ventricular lead was the Medtronic model 4195 (‘Starfix’) unipolar lead with deployable lobes. Unfortunately, the lobes were not effective for veins of larger diameter than the lobes. It has also raised concerns about extractability [12,13]. A novel active fixation left-ventricular lead (Model 20066, Medtronic, Inc.) is currently under 56

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FIGURE 2. Novel active fixation left-ventricular lead (Model 20066, Medtronic, Inc.). This 4FR lead is structurally based on the market released Medtronic Attain 4196. Active fixation of the lead is achieved by clockwise rotation of the lead body, which secures the small side helix to the vein wall (courtesy of Medtronic Canada).

investigation (Fig. 2). This 4FR derivative of a prior market-released lead has a small side helix proximal to the ring electrode that engages the vein wall with a clockwise rotation of the lead body. An abstract detailing the early experience suggests that the lead performance is safe and reliable, but judgment should be reserved until full study data are published (Yee et al., May 2013, Heart Rhythm Society Annual Scientific Meeting abstract; unpublished data).

TRANSSEPTAL ENDOCARDIAL LEFTVENTRICULAR LEADS Several years ago, it was suggested that leftventricular pacing could be achieved endocardially by delivering the lead across the inter-atrial septum. When first proposed, the goal was simply to allow CRT in patients in whom the conventional coronary venous route was not possible. It has been speculated that endocardial pacing might be more physiologic and superior to epicardial pacing since it mimics the normal transmural activation sequence and pacing on the endocardium might directly access the Purkinje network, resulting in more rapid spread of the electrical activation. Over the past year, there have been several studies examining this issue. Strik et al. [14] compared left-ventricular endocardial to epicardial conventional biventricular pacing in a canine model of left bundle branch block (LBBB) alone, LBBB combined with heart failure, or LBBB and myocardial infarction. They showed that endocardial biventricular pacing was associated with a significantly shorter QRS duration and total left-ventricular activation times than epicardial biventricular pacing, which is indicative of more uniform ventricular depolarization. Left-ventricular positive dP/dtmax was significantly Volume 29  Number 1  January 2014

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Left-ventricular lead placement techniques Manlucu and Yee

higher (1673  382 vs. 1527  320; P ¼ 0.005). Leftventricular stroke work trended higher, but failed to reach statistical significance. This was in keeping with earlier studies in patients. Unfortunately, attempts to show a similar advantage in patients with conventional CRT indications have not been as positive. Ginks et al. [15] conducted an acute hemodynamic study involving invasive leftventricular pressure recording in 10 CRT patient candidates [15,16]. The study objective was to examine whether myocardial activation pattern played a role in response to CRT. While doing so, they compared biventricular endocardial, biventricular epicardial and multisite left-ventricular pacing combining endocardial and epicardial approaches. More patients showed a hemodynamic benefit from endocardial biventricular or multisite leftventricular pacing than pericardial biventricular pacing alone, but endocardial pacing was not uniformly better. The authors suggested that much depends on the underlying pattern of left-ventricular electromechanical dyssynchrony. Padeletti et al. [16] performed a similar acute hemodynamic study that examined left-ventricular pressure–volume loop measurements in patients who were CRT candidates. Left-ventricular endocardial pacing was performed from several prespecified locations and compared to a single epicardial pacing site chosen by the implanting physician based upon coronary vein anatomy and physician discretion. Measurements were made over a range of paced atrioventricular intervals. The investigators reported no significant differences between endocardial and epicardial pacing configurations in terms of left-ventricular systolic or diastolic function measurements and both improved left-ventricular performance compared to baseline. Nonetheless, they reported that the optimal left-ventricular endocardial site yielding the best left-ventricular performance improvement was consistently better than the chosen epicardial pacing location. In other words, like epicardial pacing, the precise endocardial pacing site yielding optimal response likely depends upon the myocardial substrate; that is, the location of any myocardial scar and the characteristics of the depolarization pattern, and whether there are any functional lines of block. Left-ventricular endocardial pacing will certainly have at least a niche role in bringing CRT to patients in whom the coronary venous system is inaccessible or where limitations in venous anatomy cause problems that cannot be overcome. More widespread adoption will require the demonstration of compelling clinical benefits that outweigh the inherent risks and also a set of delivery tools that make the procedures easy, consistently successful,

FIGURE 3. Chest radiograph of a patient with a transseptal endocardial left-ventricular lead seen in a stable basal anterolateral position.

safe, uncomplicated and inexpensive. Several techniques for delivering the left-ventricular lead across the atrial septum have been described, but they share the same step of performing the transseptal puncture from a femoral or inferior approach. Recently, Patel and Worley [17] described another variant wherein the femoral transseptal apparatus is snared by another deflectable sheath assembly introduced from the SCV vein. As the transseptal sheath crosses the interatrial septum, the deflectable sheath is passively advanced into the left atrium. Once the snare is released and the inferior transseptal

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sheath removed, the deflectable sheath delivers the left-ventricular lead across the mitral valve. Unfortunately, all of these techniques necessitate a separate inferior transseptal puncture approach. Eliminating this step would be highly desirable and should be achievable. The first step towards achieving reproducible transseptal punctures from the SCV or axillary vein was recently described at the Heart Rhythm Society Annual Scientific Meeting of May 2012 at an Innovations Session. The ALSYNC (Alternate Site Cardiac Resynchronization) study is a prospective, single-cohort study evaluating the safety and performance of a platform for transseptal puncture and delivery of a left-ventricular endocardial lead all from a superior access (left or right axillary or SCV vein) (Fig. 3). Enrolment of the targeted 40 patients has been completed and results are pending after 6 months of follow-up is completed on all patients. It is seemingly small technological advances such as improvements in catheter design that will eventually pave the way for properly designed and powered studies evaluating the clinical merits of left-ventricular endocardial pacing.

CONCLUSION The development of innovative lead delivery techniques and the promise of novel lead technology provide several alternative solutions to the various anatomical hurdles that have previously thwarted attempts at a successful left-ventricular lead implant. This will hopefully translate into more efficient targeted left-ventricular lead placement and improved CRT response rates. Acknowledgements None. Conflicts of interest Dr Yee is a Medtronic consultant, speaker and has received research grant support; and a Sorin consultant and speaker.

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REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Moss AJ, Hall WJ, Cannom DS, et al. Cardiac-resynchronization therapy for the prevention of heart-failure events. N Engl J Med 2009; 361:1329– 1338. 2. Tang AS, Wells GA, Talajic M, et al. Cardiac-resynchronization therapy for mild-to-moderate heart failure. N Engl J Med 2010; 363:2385– 2395. 3. Jackson KP, Hegland DD, Frazier-Mills C, et al. Impact of using a telescoping& support catheter system for left ventricular lead placement on implant success and procedure time of cardiac resynchronization therapy. Pacing Clin Electrophysiol 2013; 36:553–558. Good summary of interventional approach to left-ventricular lead implant. 4. Kowalski O, Lenarczyk R, Prokopczuk J, et al. Effect of percutaneous interventions within the coronary sinus on the success rate of the implantations of resynchronization pacemakers. Pacing Clin Electrophysiol 2006; 29:1075– 1080. 5. Worley SJ. Implant venoplasty: dilation of subclavian and coronary veins to facilitate device implantation: indications, frequency, methods, and complications. J Cardiovasc Electrophysiol 2008; 19:1004–1007. 6. Oto A, Aytemir K, Okutucu S, et al. Percutaneous coronary sinus interventions to facilitate implantation of left ventricular lead: a case series and review of literature. J Card Fail 2012; 18:321–329. 7. Worley SJ, Gohn DC, Pulliam RW. Goose neck snare for LV lead placement in difficult venous anatomy. Pacing Clin Electrophysiol 2009; 32:1577– 1581. 8. Rafael A, West M. Coronary venous floss: a novel technique for left ventricular lead positioning in cardiac resynchronization therapy. J Innovations Cardiac Rhythm Manag 2012; 3:988–991. 9. Worley SJ. CRT delivery systems based on guide support for LV lead placement. Heart Rhythm 2009; 6:1383–1387. 10. Tomassoni G, Baker J, Corbisiero R, et al. Postoperative performance of the Quartet(R) left ventricular heart lead. J Cardiovasc Electrophysiol 2013; 24:449–456. 11. Biffi M, Zanon F, Bertaglia E, et al. Short-spaced dipole for managing phrenic nerve stimulation in patients with CRT: the ‘phrenic nerve mapping and stimulation EP’ catheter study. Heart Rhythm 2013; 10:39–45. 12. Maytin M, Carrillo RG, Baltodano P, et al. Multicenter experience with transvenous lead extraction of active fixation coronary sinus leads. Pacing Clin Electrophysiol 2012; 35:641–647. 13. Cronin EM, Ingelmo CP, Rickard J, et al. Active fixation mechanism complicates coronary sinus lead extraction and limits subsequent reimplantation targets. J Interv Card Electrophysiol 2013; 36:81–86. [discussion, 6] 14. Strik M, Rademakers LM, van Deursen CJ, et al. Endocardial left ventricular pacing improves cardiac resynchronization therapy in chronic asynchronous infarction and heart failure models. Circ Arrhythm Electrophysiol 2012; 5:191–200. 15. Ginks MR, Shetty AK, Lambiase PD, et al. Benefits of endocardial and multisite pacing are dependent on the type of left ventricular electric activation pattern and presence of ischemic heart disease: insights from electroanatomic mapping. Circ Arrhythm Electrophysiol 2012; 5:889–897. 16. Padeletti L, Pieragnoli P, Ricciardi G, et al. Acute hemodynamic effect of left ventricular endocardial pacing in cardiac resynchronization therapy: assessment by pressure-volume loops. Circ Arrhythm Electrophysiol 2012; 5:460– 467. 17. Patel MB, Worley SJ. Snare coupling of the prepectoral pacing lead delivery catheter to the femoral transseptal apparatus for endocardial cardiac resynchronization therapy: mid-term results. J Interv Card Electrophysiol 2013; 36:209–216.

Volume 29  Number 1  January 2014

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Advanced left-ventricular lead placement techniques for cardiac resynchronization therapy.

Due to complex venous anatomy and limitations in lead delivery tools and technology, the incidence of failed left-ventricular lead implants continues ...
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