Optimal CRT With a Net Reduction of 3 Leads With Use of Novel CRT-DX System

The concept of single-lead VDD pacing was developed in part to reduce hardware in the body without compromising device therapy or patient safety. Yet, VDD devices have historically been underutilized in the United States, primarily due to suboptimal performance and questionable long-term reliability.¹ A meta-analysis comparing VDD to conventional systems with an atrial lead found VDD devices were associated with a lower risk of pneumothorax as well as shorter implant time, resulting in less fluoroscopic exposure.² The omission of the atrial lead decreases associated complications such as atrial lead dislodgement by 40%, reducing the risk of complications that can add hospital days and increase costs.³

In other words, less hardware means less risk and fewer complications. The benefits of eliminating the atrial lead in primary prevention ICDs have been well documented in recent studies such as the SENSE trial⁴ and THINGS registry,⁵ in which the DX system (BIOTRONIK) was leveraged to enhance diagnostic capabilities while eliminating risk associated with additional leads. The proprietary signal amplification and filtration offered in the DX ensures atrial sensing stability and P-wave visibility,^4,5 as reported by several investigators, in addition to reduction of inappropriate therapies.^4,6 This would also apply to patients indicated for a cardiac resynchronization therapy defibrillator (CRT-D) who have a healthy sinus node or suffer from atrial fibrillation (and therefore, do not benefit from atrial pacing support).

Case Presentation

A 74-year-old female was referred for management of RV lead noise on a CRT-D system. Her chest x-ray revealed she had 5 endocardial leads implanted. She was a small-framed woman with a body mass index <20. In 2003, she underwent CRT-P system implantation with a diagnosis of third-degree heart block, mildly reduced ejection fraction, congestive heart failure NYHA Class II-III, and paroxysmal atrial fibrillation. The first system implanted in 2003 was a CRT-P device with 3 Medtronic leads: 5076-52 (RV), 4193-88 (LV), and 5076-45 (RA). In 2005, the patient had complaints of palpitations, pre-syncope, lightheadedness, and dizziness. IEGM recordings from her existing biventricular pacemaker revealed sustained ventricular tachycardia (VT) and paroxysmal atrial fibrillation. In June 2005, the patient was then upgraded to a CRT-D system with a dual-coil DF-1 right ventricular (RV) ICD lead model 0158 (Guidant). The patient now had 4 indwelling leads, as the original RV pace/sense lead was capped.

In 2010, her device reached elective replacement and it was replaced with a BIOTRONIK CRT-D system programmed to DDDR 70/130 PPM. During the generator replacement, the leads could not be removed from the Guidant CRT-D header. Special tools were used to crack the header, and in so doing, the right atrial (RA) lead and the pace/sense portion of the ICD lead were damaged. The damaged RA lead was replaced with a Setrox S 53 active-fixation RA lead (BIOTRONIK). The indwelling atrial lead from 2003 was capped and left in situ. Because the pace/sense portion of the ICD lead was damaged, the original RV pacing lead from 2003 was uncapped and plugged into the new BIOTRONIK CRT-D device.

In 2020, BIOTRONIK Home Monitoring reported a red alert that the patient had experienced an episode of ventricular fibrillation, but further investigation determined it was noise on the RV lead. By the time she arrived at the clinic in 2020 for RV lead management, this patient had 5 indwelling leads. The noise on the RV lead compromised its performance and necessitated a new lead. The old approach of simply capping leads and abandoning them in place would not be appropriate for this patient, as vessel occlusion is often a concern with elderly patients in whom abandoned leads begin to accumulate. After options were explained to the patient, she agreed to lead extractions. However, a strategy had to be devised to allow for an optimal therapeutic configuration while reducing the patient’s risk. It was determined to extract the leads in order of ease of extraction, with the easiest leads to be removed first. Using laser sheath extraction, the first lead to be removed was the damaged RA 5076-45 lead (from 2003). The next lead to be removed was the fractured RV pace/sense lead (from 2003). A BIOTRONIK RA lead from 2010 was in place, but when a firm straight stylet was inserted into the lead, it dislodged. This compelled a decision, since at this point, the patient had no RA lead. An evaluation of device diagnostic histograms showed that she was BiV pacing nearly 100% of the time, which is optimal and appropriate for a CRT patient, but she did not have sick sinus syndrome or chronotropic incompetence. Therefore, it was clear that she did not need atrial pacing support. A CRT-DX system was now considered, which would allow atrial sensing via the floating atrial dipoles of the DX lead. The atrial lead was relatively easy to extract. At this point, the dual-coil RV ICD lead (from 2005) was successfully extracted. A Plexa ProMRI S DX ICD lead (BIOTRONIK) with floating dipoles for atrial sensing was then implanted. Thus, 4 indwelling leads were removed and 1 new lead was implanted, for a net reduction of 3 leads.

The patient was implanted with a BIOTRONIK CRT-DX system that would allow CRT pacing and optimal atrioventricular (AV) synchrony (AsBiVp) without an atrial lead. A CRT-DX system was particularly appropriate for her since she had high-degree heart block,⁷ atrial fibrillation,⁸ and a small frame, meaning that it was best for hardware to be kept to a minimum. The CRT-DX device selected was the Acticor 7 HF-T (BIOTRONIK ), which is available in DF4 IS4 and DF4 IS-1 configurations. With a device longevity of over 11 years, this patient may avoid device replacement for over a decade. A subanalysis of the QP ExCELS registry, which evaluated subjects with a 2-lead CRT-DX system compared to those with a standard 3-lead CRT-D system, found that CRT-DX patients received therapy similar to conventional CRT-D but with significantly fewer complications and fewer inappropriate shocks.⁶

With less pocket bulk, her infection risk was reduced, and the 7.8 French Plexa ProMRI S DX 65/15 single-pass ICD lead was chosen to decrease venous burden. This lead has floating dipoles for atrial sensing, but the DX algorithm’s proprietary amplification and signal filter is key in maintaining stable atrial sensing over time.⁵ The RV lead was placed on the septum. Perioperative P-waves were 3.8 mV and R-waves were 15.2 mV. There was appropriate atrial sensing during implant. The unipolar LV lead had appropriate pacing and sensing thresholds, and she did not need atrial pacing. The exact proportion of CRT patients who require atrial pacing support is not known, but a Swedish registry found 54% of patients with CRT systems had a history of atrial fibrillation,⁹ and another study found that >25% of CRT patients develop AF at some point after device implant.¹⁰ Furthermore, a subset of CRT patients have a healthy sinus node and appropriate atrial function. Thus, it is reasonable to conclude that many, perhaps even most, CRT patients do not require atrial pacing.

The device was programmed to VDD 40 with an upper rate of 130 ppm and a mode-switch rate programmed for +30 ppm. In the event of atrial fibrillation, the device would automatically mode-switch to VDIR with BiV pacing at 70 ppm with rate response, and turn off tracking until the patient converts back to sinus rhythm. In the VDD mode, the device will track the intrinsic atrial rate to 130 bpm.

Shortly after connecting the leads to the generator and confirming appropriate pacing and sensing, the patient had a brief episode of atrial fibrillation, at which point the device mode switched and began to BiV pace the patient at 70 ppm. She remained in atrial fibrillation for a few minutes, then converted back to normal sinus rhythm around 80 bpm without intervention, and her original lower rate limit was restored. This confirmed that the system successfully delivered CRT even during atrial fibrillation, and was able to revert to AV synchronous CRT when sinus rhythm was restored.

Recovery was uneventful, and the patient immediately noticed that there was substantially less pocket bulk, which had troubled her in the past. Chest x-rays show the reduction of patient hardware (Figure 1).

Congruent with her history, this patient has already had an episode of VT since implantation of her Acticor 7 HF-T device, which was captured by BIOTRONIK Home Monitoring (Figure 2).

Discussion

Patients indicated for CRT essentially face a lifetime of device therapy as well as periodic generator and lead revisions. As technology advances and patients’ underlying conditions change, these revisions sometimes involve a system upgrade or the addition of new leads. High-rate atrial activity is a serious consideration for many device patients. Large trials such as ASSERT¹¹ and TRENDS¹² have suggested a higher degree of urgency for the detection and treatment of subclinical atrial arrhythmias. Additionally, the CASTLE AF¹³ clinical trial reported an increased mortality risk associated with atrial fibrillation in heart failure patients.

In this case, it was crucial to reduce the number of leads in this patient’s vasculature while still delivering optimal CRT therapy. Great advances have been made in transvenous lead removal, and 4 leads could be successfully removed in a single procedure. It should be noted in this context that CRT patients who undergo transvenous lead extraction are not at risk of increased 30-day mortality compared to similar patients without a CRT system.¹⁴ The end result was that 4 leads could be extracted, some of which were damaged, and a new CRT-D system that was safe and effective could be implanted. The patient was seen again at 30 days and was doing well. Her mean atrial rate at that time was 74 bpm with reliable AV synchrony and 99% BiV pacing. She is very satisfied with the cosmetic improvement of her implant site. More than that, with a net reduction of 3 leads and use of a CRT-DX system with 11 years of projected longevity, this procedure offers both this patient and the healthcare system excellent care without compromise. 

This article is published with support from BIOTRONIK.

Disclosures: The authors have no conflicts of interest to report regarding the content herein; outside the submitted work, Mr. Bryant reports he is an employee of BIOTRONIK.

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