In this feature interview, EP Lab Digest® speaks with Dr. George Mark from the Heart House of New Jersey about his use of Boston Scientific’s S-ICD System. This is the experience of Dr. Mark. Please refer to the Directions For Use for the full implant instructions.
How do you talk to your patients about the S-ICD System as an option?
When I see a patient who needs a defibrillator, before I even enter the room I try to gauge whether they need pacing or if he or she would be a candidate for the subcutaneous defibrillator. I think it’s important to have a sense of whether someone is a good candidate prior to offering the device to them, because once you offer a patient this option, that is what they want — they don’t want to have a device with a lot of wires in the heart, and they would rather have a device that is purely under the skin and no deeper. When I tell patients about the subcutaneous ICD, I explain that it is a device that has been shown to be equal in terms of protection, and that the nature of it being just under the skin offers some distinct advantages, such as reducing the risk of procedural complications at the time of implant, and — although it’s probably still too early to tell — with long-term complications with leads. I describe the ways in which they are inferior to standard defibrillators, including that they are not pacemakers and do not offer that kind of protection. However, as I’ve already subselected a population of patients who are without the need for pacing to begin with, that is usually not an issue.
What percentage of your patients do you find meet the criteria for an S-ICD?
Of all my defibrillator cases, it’s probably about a third. The reason that this percentage is not higher is because there is a good number of the total ICD population that requires resynchronization. There are also a number of elderly patients who have slower resting heart rates, are on beta blocker therapy or amiodarone, or are on medications that keep their resting heart rates slower. Therefore, when given the option, I always err on giving patients who need pacing that capability.
Do you perform or directly supervise screening and prep and drape processes?
I no longer personally supervise those parts of the procedure; it’s been about three years now that we’ve been implanting the subcutaneous defibrillator, so it’s no longer a new procedure to us. However, I definitely recommend that when people start to implant these devices that they take an active role in all stages of the procedure. Truthfully, the procedure itself is not complicated — the hard work is done prior to the patient getting the device, during screening, choosing the patient and making sure the prep is appropriate so that the procedure runs smoothly. Those stages of preparation are just as important for achieving good long-term outcomes as the actual implantation of the device. Early on, because it was so new, I personally screened every single one of my patients. Over time, we got a better feel as to which EKGs might be more concerning for possible screen failures and others that might look like an easy screen.
Do you routinely perform exercise testing? Is this done on all patients, or a subset?
I will routinely perform treadmill testing post implant on my most active patients. In my patient population of about 70 devices so far, there is a distinct separation of age groups. There are the older patients who may be on dialysis or have had device infections or reasons why they shouldn’t have a standard ICD, and there is the young patient population in which I often choose the subcutaneous ICD, because I worry about long-term lead issues such as lead fracture, the need for extraction, or lead complications. Since this younger patient population is a much more active group than the older patient population, I definitely recommend exercise screening after implant. If a patient passes screening at rest in the office or hospital, I will put the device in and use exercise testing as a means to fine-tune programming. At elevated heart rates storage of the sinus template and allowing the device to select the lead it believes has the best sensing characteristics, are the best ways to prevent innappropriate shocks for both t wave oversensing and SVT. This is particularly effective for patients who develop rate related bundle branch block.
How do you program the devices before the patient leaves the hospital?
Nominally the device is set for a two-zone setting at heart rates of 200 to 220. Programming a discriminator zone allows the device to utilize the algorithms of the subcutaneous defibrillator in terms of distinguishing SVT from VT, or to avoid t-wave oversensing. The higher rate zone, technically something like a VF zone, nominally set for 220 and above, purely is a beat counter. Personally, I usually set my devices for 190 to 240. I like to broaden that discriminator zone to really use the full advantages of the device’s algorithms to avoid inappropriate shocks, reserving that VF zone for only the fastest of arrhythmias.
Do you recommend a quick fluoro for device placement?
Again, when I started implanting the subcutaneous defibrillator, I typically did not use fluoroscopy at all, and would confirm the appropriate placement of the device by a successful defibrillation threshold test (DFT) at the end of the procedure. I would also confirm appropriate placement with a PA and the lateral chest x-ray post-implant, both to define the position of the device for future reference and to fine-tune my own implant skills to make sure that I’m leaving the device where I expected it to be.
Now when I’m teaching physicians to perform the procedure, I definitely see the advantages to taking a moment prior to prep to bring a mockup device into the operating room with the patient on the table in the appropriate position, and using fluoroscopy to outline where that device will eventually be placed. This way, when the procedure is being done without fluoro, there is a visual guide to where the device should end up.
I’d also recommend using fluoroscopy in very heavy/overweight patients or for women with large breast tissues where assessing anatomical landmarks are more difficult during the procedure. For the normal-sized patient, I still do not use fluoroscopy before, during, or after the procedure. If I find the defibrillation threshold to be high, at that point I would bring in fluoroscopy to assess device position.
Do you have your patients under general or local anesthesia?
Our institution is lucky enough to have anesthesia services for all of our EP cases, so I’ve always used monitored anesthesia care (MAC) sedation with propofol as the main means of maintaining a comfortable procedure. With that said, generous use of local is important for both the intra-procedural and post-procedural comfort of the patient — appropriately anesthetizing the areas we are working in is a big part of how well people tolerate the procedure. I probably use about twice as much local anesthetic for a subcutaneous device as I would for a standard ICD. I think that fully anesthetizing the axillary pocket area is probably the most important aspect of having good patient comfort, because that is a very tender area and you are making a rather large-sized pocket. Providing a lot of local anesthesia makes the procedure run more smoothly, and postprocedurally, people suffer from less acute pocket discomfort afterward. We tend to use a mixture of short- and long-acting local anesthetic, so that we can provide a little bit of lingering pain relief. Because of these techniques, I’ve been very successful at getting most of my patients home the same day — probably more than 90 percent of my patients go home the same day. It’s not to say that there is not discomfort — they just don’t feel the need to stay in the hospital for stronger pain medicine. I prescribe 4-5 days worth of an analgesic such as Percocet so they’re able to recover in their home environment, which is always preferable.
What areas of the implant process have you gained most efficiencies as it relates to procedure time?
In my experience, there is always an initial hesitancy when doing new procedures that you’re not necessarily familiar with. For me, my initial concerns had a lot to do with the tunneling of the leads through the soft tissues. As a fellow, I did a lot of lead upgrades or extractions for leads that had failed, but didn’t do a lot of tunneling. Therefore, it was novel and a somewhat daunting prospect to tunnel, although truthfully, I later found tunneling to be the easiest part of the procedure and of all the steps, it probably takes the least amount of time. I think developing proficiency with tunneling has a lot to do with initiating the level of the tunneling with blunt dissection, so that you know you’re on the right plane, and then guiding the tunneling tool to your other finger in whichever incision you’re working in; it’s important to make sure that your other finger is on that right tunneling plane so that when the tunneling tool touches your finger, you’ve maintained a very flat tunneling line along the fascia. I think the most time-consuming parts of the procedure are making the pocket and closing the incisions. The making of the pocket is so important because you want to be deep down and right on top of the chest wall, and not have any fat insulate the device from the chest wall. Therefore, good technique for making the pocket is certainly important for procedural time as well as for the success of the procedure. My recommendation is that when making the axillary incision, to work all the way down to the fascia at the position of your incision before then expanding upon that fascial plane up into your axillary pocket, so that you stay deep and you’re not having to worry that there will be fat between the chest wall and the can. Unfortunately I may never break a certain implant time because I haven’t become any faster when stitching. I want the incisions to be strong and to have good cosmesis — you want to put things back together as nice as you found them — so it’s important to take the time to do that stitching.
My first five cases probably all needed one hour, although the first few in that range took an hour and 15 minutes to an hour and a half. This had a lot to do with going through these new steps, working in a new area and being a little cautious, and taking the time to make sure everything went well for the first cases — I think that’s appropriate. You should never do your first case as fast as your last case. Within 10 cases, I had gone under an hour, and at this point, the best I have been able to do is 42 minutes. Each time I think it went so smoothly that it might be a new record, but it’s always 42 minutes. I think it’s due to certain steps, such as the time it takes to DFT test and the time it takes to close. I think with standard ICDs, there is a growing trend to skip DFTs. For the S-ICD, however, I think testing is an important part of the implant, because it confirms a proof of concept that you’ve left the device in a position where it’s going to provide protection.
Do you have any special implant considerations for women with respect to comfort and cosmetic concerns?
From a cosmetic standpoint, the subcutaneous device is equally attractive to both men and women because it is almost completely hidden, even in minimal states of dress, compared with a standard ICD. I try to keep the third incision (near the top of the sternum) very small, to as little as a centimeter, in a fashion that will allow a very minimal scar. From a comfort standpoint, the device does sit in and around the area of the bra strap for women, so I sometimes recommend that my female patients wear a sports bra immediately post procedure to avoid some of the more direct pressure that might be uncomfortable during the early wound healing stages. It’s also important to have a good prep, because the breast tissue itself can be in the way of where you want to work, and you certainly don’t want to cut through breast tissue in order to put the device where it’s supposed to go. There are some men who have a lot of breast tissue as well. For these patients with a lot of breast tissue, I make an effort to prep after pulling the breast back towards the left shoulder to expose that inframammary crease and work at or below that level, so that I’m not cutting through breast tissue and making the implant more difficult. It’s very important to prep that chest area in a way that makes it easy to get to the area where you need to work.
What have your patient outcomes been with respect to infection, high DFTs, inappropriate shocks, and complications?
In the last three years, the three physicians in our group have implanted nearly 100 devices, the majority of which are mine. In this group of patients, we have had only one high defibrillation threshold test, and when fluoroscopy was brought in to visualize the can and its position in its relationship to the heart, it became clear that the device was too low. After moving the device into a position more appropriate, the defibrillation threshold testing was normal. So I guess technically we have had no issues with high defibrillation testing. We have had one device that had to be explanted for infection, one device that was explanted because a pacing system was required, and no lead dislodgements. This is very much on par with our experience with standard ICDs — a very similar rate of complication. I'd like to draw attention to the fact that as expected, we’ve had no lead perforations, lead associated endocarditis or pneumothoraces. I unfortunately can’t say the same for our standard ICD population. The absence of these complications is a clear advantage of a purely subcutaneous device.
How do you address pain management?
Before patients enter the operating room, part of my preprocedural discussion is that my intention would be to send them home after the procedure, as long as they’re feeling up to it. We can always change the plan if they were not comfortable and felt like they’d rather stay; however, very few people have asked to stay. When people have stayed overnight, it’s for reasons such as needing dialysis the next day or going to rehab, etc. Most patients know that there will be a little discomfort, but feel like they can manage that at home. Often I’ll write a prescription for four or five days’ worth of a pain medicine such as Percocet. Maybe once or twice have I been asked for more pain medicines after that initial prescription has worn off. At our first post-operative visit which is typically about a month after implant, there certainly are people who still describe discomfort in certain positions or when lying on their side, but my standard ICD patients say that as well. I believe that the discomfort may linger a little longer for the subcutaneous ICD patient than for the standard pacemaker or ICD patient. I just reinforce that over time the device will be less and less noticeable and uncomfortable, and universally by the next visit (three to four months after that), most patients have forgotten all about the device. I’ve certainly had patients who have asked me in the first few days afterward whether they could go play golf or do more active things than I would typically be willing to allow a device patient to do. However, my only real concern about the device is that the wound heals well, so usually that restriction in terms of what I let them do is shorter than with a standard device, where I worry about lead dislodgement. Therefore, my overall restrictions upon people early after the procedure is shorter, because once those wounds have healed, my concern about them doing something to affect the device negatively is minimal.
How has your implant changed or evolved over time?
Probably not by much — I pretty much implant the device the same way every time. I feel like I have had very good success in terms of patient satisfaction and outcomes, and I haven’t made many major changes in my implant technique over the course of three years.
Are there any special implant considerations that you would tell an implanting physician early in their S-ICD experience?
I definitely recommend using fluoroscopy in the beginning to identify where the device is going to sit, so during the procedure when you are focusing on landmarks, you have an additional guide to help you. It doesn’t matter as much whether the incision is horizontal or vertical or curvilinear, as long as the device ends up where it’s supposed to go. Therefore, feeling confident early in your experience that you know where that device needs to end up is going to help make the procedure run smoothly and ensure success. Take time and care in identifying anatomical landmarks pre prep, and draw on the chest with an indelible marker to help guide you during the procedure. Once you find that your approach delivers the same position and the same success, time after time after time, then you may choose to decrease your use of fluoroscopy.
Disclosure: Dr. Mark has no conflicts of interest to report regarding the content herein.
This is a paid placement sponsored by Boston Scientific.