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I-CRT: Challenging the Conventional Approach to LV Lead Placement, Literally and Figuratively

Seth Worley, MD

MedStar Heart & Vascular Institute

Washington, DC

Seth Worley, MD

MedStar Heart & Vascular Institute

Washington, DC

Suboptimal left ventricular (LV) lead placement in cardiac resynchronization therapy (CRT) has long been understood to be a risk factor for clinical non-response.1 There is evidence to suggest that LV lead placement influences hemodynamic response2 and that placement at the site of latest activation portends more favorable outcomes.3 More specifically, placement in the basal or midportion of the lateral or posterolateral region reduces risk of death and hospitalization for heart failure patients.4 While the rate of failure to place the LV lead has decreased over time,5 presumably due to improvements in placement technique, the conventional wisdom around CRT is that it is not successful in about 40% of cases.6 There are numerous reasons why CRT may fail, although complicated anatomy is an oft-cited factor.5 

However, a willingness to challenge some of the traditional conventions in LV lead placement may offer opportunities to improve outcomes with CRT while equipping clinicians with a more robust toolkit for managing challenging cases. Interventional CRT (I-CRT), as the name would imply, describes the use of techniques employed by interventional cardiologists and radiologists for cannulation of the coronary sinus (CS) and LV lead placement. I-CRT is intentionally disruptive in the sense that it forces the operator to think differently about approaching the CS anatomy and lead placement, and equips him or her with a set of tools that make doing so more accurate, efficient, and effective.

Ultimately, I-CRT is a process, an entirely different approach to a time-tested intervention. Not only does it facilitate greater accuracy of LV lead placement, I-CRT imbues a mindset to examine each step from a problem-solving perspective. That is, I-CRT offers a better way to place the lead while giving the operator tools to improve upon his or her technique.

What is I-CRT?

Myriad studies demonstrate that CRT can be highly effective in resolving symptoms of congestive heart failure while conferring functional improvement, yet the field continues to be beset by concerns over a technically challenging procedure that is often prone to failure for reasons thought to be beyond the control of the implanting electrophysiologist. Improvements in schemas for patient selection have led to incremental improvements in outcomes associated with CRT. It seems intuitive, then, to improve upon the actual implantation technique in an attempt to maximize the potential benefits of CRT.

In traditional “over-the-wire” approaches to lead placement, the CS ostium is discovered by probing the CS with a soft-tipped wire through a preformed sheath. The pacing lead is then introduced over an angioplasty wire. These steps introduce a couple of challenges to the operator. First, anomalous CS entry to the atrium and/or existing pathology might make it difficult to localize the CS. While this can be overcome by incorporating a selective coronary angiogram with placement to a tributary vessel,7 I-CRT facilitates more rapid and accurate identification of the CS ostium and target vessel, even in difficult anatomic situations.

A second challenge is that tortuous vessels may present an obstacle for advancement of the sheath or LV lead over the wire, which may simply be inadequate to support the most crucial aspects of the procedure. When confronted with such challenges, the operator is often forced to seek an alternate route, implant in a non-target vessel (that may culminate in suboptimal placement), abandon the procedure entirely, or resort to another backup strategy. In any case, these situations are likely to extend procedure time and function, as well as increase anxiety in the operator.

I-CRT offers a fundamentally different approach that seems to answer some of the mechanistic challenges of over-the-wire lead placement while providing access to novel techniques that allow the operator to adjust the approach more easily during challenging cases. The steps for performing I-CRT have been described previously.8,9 Briefly, when performing I-CRT, the CS ostium is localized using contrast introduced via a guide catheter, and it is then cannulated with a sheath advanced over a guide catheter. Finally, the target branch is cannulated with a telescoping lead delivery system consisting of a target vein selector connected to the contrast injection system and a delivery guide shaped to fit into the target vein.8 

A few important differences should be noted with I-CRT: use of contrast facilitates CS localization and the telescoping lead delivery system, because it functions like a rail, providing greater stability than a guide wire. Fundamentally, though, what the interventional approach offers is a greater chance for optimal and accurate lead placement. Jackson and colleagues reported a lower rate of failed LV lead placement with I-CRT versus over-the-wire placement (1.9% vs 8.1%; P<0.02).10 

One reason why placement may be optimized with I-CRT is that it introduces opportunities to utilize specialized maneuvers and techniques. For instance, if a wire is used in conjunction with the catheter, it can be used to support the advance of a wider sheath beyond the site of tortuous vessels. Smaller catheters can also be used to find side branches of the vein should the initial implant site prove to be inadequate. As well, balloon venoplasty becomes an option for managing a stenotic subclavian or coronary vein. Finally, lead advancement can be performed with a snare technique, where a secondary wire is advanced through the target vein targeting the proximal CS, a gooseneck snare is used to capture the distal end of the wire, and the lead is advanced to its intended implant location.

Obstacles to Adoption

The potential to perform venous angioplasty with I-CRT is a useful example of why interventional techniques differ from other lead placement approaches — and not just mechanistically. When confronted with stenotic or tortuous vessels while using over-the-wire placement, the standard approach is to introduce a dilator, which is what electrophysiologists have been doing for decades. But just because “that’s the way we have always done it” does not necessarily mean it is the best solution. Whereas, adopting an interventional mindset challenges the operator to look at each step of the procedure, think about whether there might be a better way, and then adapt proven techniques that solve the problem.

An unwillingness to adapt to new techniques is, perhaps, the greatest obstacle to wider adoption of I-CRT. At least some of this is attributable to the fear of the unknown. But the truth is, the success of I-CRT is more so attributable to the tools the implanting doctor uses and not necessarily to the skill of the operator. I am not discounting the need to learn the instruments and develop an understanding of the various wires and sheaths on the market. At the same time, I have proctored several cases in which the operator was previously unsuccessful in placing a lead but was then able to place the lead in a similar case using an interventional approach. Because the right tools can make all the difference: one can open a bottle of wine with a screwdriver, but it is a lot easier to use a corkscrew. 

I would contend that I-CRT actually shortens the learning curve for lead placement in addition to helping the implanting doctor become efficient and effective in accurately placing it. Unfortunately, at least from my perspective, I-CRT is not widely taught in electrophysiology training programs. Thus, electrophysiologists interested in adopting I-CRT often have to unlearn certain behaviors required to perform over-the-wire placement. Since I believe so strongly in the benefits of I-CRT for the operator and the patient, I have taken it upon myself to dedicate time each month to proctoring interested electrophysiologists. There are also excellent industry-sponsored courses (of which I am part of the faculty), such as those offered by Merit Medical. As a first step, I would highly recommend a literature search to review the pertinent data. There is a great online resource at (sponsored by Merit Medical). 

Another obstacle to wider adoption of I-CRT is more sensitive in nature and relates to the modern electrophysiology practice. It is hard to argue that electrophysiologists have become somewhat disconnected from direct patient care. Many times, patients with congestive heart failure are referred to our practice for LV lead placement and we may not be involved in the regular care or follow-up of that patient. That dynamic creates a disconnect on both ends of the spectrum. For the electrophysiologist, the “work order” nature of practice provides scant opportunity to witness long-term outcomes, or if there is a clinical failure with CRT, to investigate the cause. For the referring cardiologist, on the other hand, if CRT is unsuccessful, there is not inherent incentive to understand the nature of the failure, which only serves to promulgate the assumption that CRT is simply unsuccessful in about 40% of cases — that it fails so often is just assumed, but the reason why (suboptimal lead placement?) is often not investigated (was the anatomy challenging? Were the best tools and approach for LV lead placement employed?).

The evolution of healthcare delivery is one contributing factor in removing electrophysiologists from meaningful interaction with follow-up care of the patient. These days, most electrophysiologists are under employee contracts with large institutions; the days of independent practice are quickly fading into the rearview mirror. Rather than being a breadwinner who brings revenue to the institution, electrophysiology services mostly function under a cost-containment model. 

One unintended consequence of this is that the electrophysiologist is somewhat beholden to the equipment preferred by the institution. Many of the large operating centers have fixed contracts with the companies that supply CRT devices that bundle in the cost of the delivery system — and by and large, over-the-wire systems are most typically preferred. Therefore, the use of I-CRT necessarily entails extra cost, which becomes a point of contention, almost regardless of whether better outcomes are achievable with I-CRT compared with over-the-wire. I would not suggest that cost should not be considered at the point of care delivery, but I do wonder if a more holistic look at the economics of caring for congestive heart failure patients might reveal cost benefits with I-CRT. It seems at least plausible based on published literature that more optimized lead placement would reduce symptoms and mortality that could, in turn, produce savings on downstream healthcare utilization.


Changing our practices and approaches to patient care has the potential to be unsettling. This is not necessarily a bad thing, as it could be unwise to recklessly change course for no reason. However, in the case of CRT, what we have is a very good intervention that helps reduce morbidity and save lives; yet, CRT is fraught with an unfortunate notion that success is only slightly better than a coin flip. That realization almost demands a rethink in terms of how CRT is utilized and how it is performed to see if outcomes can be optimized.

To this point, the technology utilized in CRT devices has advanced tremendously. Improvements in imaging have steadily increased our ability to see what we are doing during a procedure. Meanwhile, refinements in diagnostics have enhanced patient selection that we can now identify the most appropriate candidates. All of this should suggest higher success rates. However, because success rates are not as high as they should be, there is rationale for improving the actual implantation technique to achieve more accurate lead placement.

Our colleagues in interventional radiology and cardiology have successfully employed percutaneous techniques for decades, and it is time we learn from them. I-CRT offers too many benefits to the operator and patient for us to ignore this much longer. There are obstacles in our way to wider adoption, but for the sake of our patients and our own sanity, we should not let them be a deterrent to adopting a better way forward.

Disclosures: Dr. Worley reports he is on the faculty of courses offered by Merit Medical. He also reports royalties from Merit Medical and Pressure Products. In addition, he discloses he has a patent issued for the Worley Sheath. 


  1. Khan FZ, Virdee MS, Fynn SP, Dutka DP. Left ventricular lead placement in cardiac resynchronization therapy: where and how? Europace. 2009;11(5):554-561.
  2. Saxon LA, Olshansky B, Volosin K, et al. Influence of left ventricular lead location on outcomes in the COMPANION study. J Cardiovasc Electrophysiol. 2009;20(7):764-768.
  3. van Bommel RJ, Ypenburg C, Mollema SA, et al. Site of latest activation in patients eligible for cardiac resynchronization therapy: patterns of dyssynchrony among different QRS configurations and impact of heart failure etiology. Am Heart J. 2011;161(6):1060-1066.
  4. Saba S, Marek J, Schwartzman D, et al. Echocardiography-guided left ventricular lead placement for cardiac resynchronization therapy: results of the Speckle Tracking Assisted Resynchronization Therapy for Electrode Region trial. Circ Heart Fail. 2013;6(3):427-434.
  5. Gamble J, Herring N, Ginks M, Rajappan K, Bashir T, Betts T. Procedural Success of Left Ventricular Lead Placement for Cardiac Resynchronization Therapy: A Meta-Analysis. JACC: Clinical Electrophysiology. 2016;2(1):69-77.
  6. Abraham WT, Fisher WG, Smith AL, et al; MIRACLE Study Group. Cardiac resynchronization in chronic heart failure. N Engl J Med. 2002;346:1845-1853.
  7. Katritsis DG. A novel technique for placement of coronary sinus pacing leads in cardiac resynchronization therapy. Europace. 2007;9:878-879.
  8. Jackson KP. Left Ventricular Lead Placement for Cardiac Resynchronization Therapy. J Innovations in Cardiac Rhythm Management. 2013(4):1284-1291.
  9. Jackson KP, Steen T. Getting the LV lead to the right spot. Neth Heart J. 2016;24(1):82-84. 
  10. 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.
  11. 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.