Clinical Usefulness of the Active Fixation Quadripolar Left Ventricular Lead Compared With the Passive Fixation Quadripolar Lead in Cardiac Resynchronization Therapy

Abstract

Background: This study compared the stability of the Medtronic Attain Stability Quad (ASQ), a novel quadripolar active fixation left ventricular (LV) lead with a side helix, to that of conventional quadripolar leads with passive fixation (non-ASQ) and evaluated their LV lead performance.

Methods and Results: In all, 183 consecutive patients (69 ASQ, 114 non-ASQ) who underwent cardiac resynchronization therapy (CRT) between January 2018 and June 2021 were enrolled. Complications, including elevated pacing capture threshold (PCT) levels, phrenic nerve stimulation (PNS), and LV lead dislodgement, were analyzed during the postimplantation period until the first outpatient visit after discharge. The frequency of LV lead-related complications was significantly lower in the ASQ than non-ASQ group (14% vs. 30%, respectively; P=0.019). Specifically, LV lead dislodgement occurred only in the non-ASQ group, and elevated PCT levels were significantly lower in the ASQ group (7% vs. 23%; P=0.007). Kaplan-Meier analysis confirmed a significantly lower incidence of LV lead-related complications in the ASQ group (log-rank P=0.005). Cox multivariable regression analysis showed a significant reduction in lead-related complications associated with ASQ (hazard ratio 0.44; 95% confidence interval 0.23–0.83; P=0.011).

Conclusions: The ASQ group exhibited fewer LV lead-related complications requiring reintervention and setting changes than the non-ASQ group. Thus, the ASQ may be a favorable choice for CRT device implantation.

Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure with a reduced ejection fraction (≤35%) and electromechanical dyssynchrony. In those patients, CRT improves heart failure symptoms and mortality.^1–3 The optimal location of the left ventricular (LV) lead is an important determinant of CRT success, and improved outcomes have been observed when the LV lead is located lateral and non-apical.⁴ Surgical repositioning due to LV leads to dislodgement, an elevated pacing capture threshold (PCT), or phrenic nerve stimulation (PNS) in up to 7% of CRT device implantations.⁵ The existing LV lead is a passive fixation lead that may shift its position postoperatively. Therefore, LV lead stability may require sacrificing pacing to the optimal position and placing the lead in the apical region. Medtronic developed the Attain Stability Quadripolar (ASQ; Model 4798), which incorporates a new active fixation mechanism to improve coronary vein positioning. The lead has a specially designed side helix that actively fixes its body to the target vessel. Owing to the active fixation of the LV lead, stable lead positioning is facilitated even in various anatomies of the coronary vein.⁶ Initial reports for this lead have shown a high insertion success rate (96.8%) and a low LV lead-related complication rate (2.3%).^7,8 In addition, active fixation of LV leads has been shown to reduce lead displacement 6 months after CRT compared with conventional passive fixation of quadripolar leads.⁹ However, to date, no study has directly compared the complication rates that require intervention between active fixation leads and conventional quadripolar LV leads. The aim of this study was to compare a novel quadripolar LV lead with a side helix for active fixation to conventional quadripolar leads for passive fixation in terms of electrophysiological performance and stability.

Methods

Lead Characteristics

The MRI SureScan^TM Active Fixation LV Lead (Model 4798) is a quadripolar LV lead with an active fixation helix between the third and fourth electrodes. This lead is placed in the coronary vein and is intended for pacing and sensing the left ventricle. The shape of the lead is a single cant, and the second and third electrodes are close together, reducing the possibility of PNS.¹⁰ The main design feature of this lead is a side helix glued to the lead surface, which allows the body to rotate clockwise, firmly fixing the lead to the vein wall. This fixation mechanism is released by rotating the lead body counterclockwise. The side helix is designed to be straightened when a force of approximately 500 g is applied. The average distance between the coronary vein and the nearest artery is 1 mm. The side helix is 0.25 mm away from the lead body, providing a 4-fold safety margin during insertion.¹¹

Study Population

In all, 183 consecutive patients (69 in the ASQ group, 114 in the non-ASQ group) who underwent CRT with passive or active fixation quadripolar LV lead implantation according to the Japanese Circulation Society guideline¹² between January 2018 and June 2021 at the National Cerebral and Cardiovascular Center were enrolled in the present single-center retrospective cohort study. Patients with de novo implantation of a CRT device, those who were upgraded from a permanent pacemaker or implantable cardioverter defibrillator to CRT, or who underwent CRT device reimplantation after removal were included in the study, whereas those with LV bipolar leads were excluded. Informed consent was obtained using the opt-out method, and the study was conducted in accordance with the 1975 Declaration of Helsinki and was approved by the Institutional Review Board of the National Cerebral and Cardiovascular Center (M26-150-12).

CRT Device Implantation Procedure

Standard techniques were used for pectoral-subfascial pocket formation and transvenous lead placement from the subclavian vein. Right atrial leads were implanted in the right atrial appendage or septum, and right ventricular leads were implanted in the right ventricular apex or septum. The LV lead, either quadripolar active fixation (ASQ leads; Medtronic, Minneapolis, MN, USA) or quadripolar passive fixation (non-ASQ leads; Medtronic, Biotronik [Berlin, Germany], Boston Scientific [Marlborough, MA, USA], or Abbot [St. Paul, MN, USA]), was selected at the physician’s discretion. All LV leads were placed under fluoroscopic guidance, and the LV lead position was evaluated using fluoroscopic images. The pacing site was determined by the physician responsible for implantation, considering factors such as PNS avoidance, output threshold, impedance, Q-LV time,^13–15 and S-QRS time.^16,17 The time required for LV lead implantation was not evaluated in the present study.

Definition of a Postoperative LV Lead-Related Complication

Postoperative LV lead-related complications included an elevated PCT, PNS, and LV lead dislodgement. Elevated PCT was defined as a case with PCT ≤2.0 V/0.4 or 0.5 ms at the end of the surgery, increasing to PCT ≥2.1 V/0.4 or 0.5 ms, due to an increase in LV lead output or a change in LV pacing polarity. PNS was defined as an intolerable symptom leading to reprogramming of the device according to the lead and device characteristics, resulting in a change in LV pacing polarity or a decrease in LV pacing output. LV lead dislodgement was defined as dislodgement of the LV leads from the cardiac vein to the coronary sinus, which required surgery for repositioning.

Data Collection

Preoperative baseline clinical and procedural characteristics during CRT device implantation were collected. LV lead performance data were collected during hospitalization and routine outpatient visits (immediately after implantation, a few days after implantation, 1 month later, and thereafter every 3–4 months). Postoperative reoperation for LV lead dislodgement, elevated PCT, and PNS resulting in a change in LV pacing polarity or pacing output, and LV lead-related complications during the follow-up period were assessed. Predictors of LV lead-related complications were also evaluated.

Statistical Analysis

Statistical analyses were performed using Stata/BE (version 17.0; StataCorp, College Station, TX, USA). Continuous variables are presented as the mean±SD and were compared using t-tests. Categorical variables are reported as n (%) and were compared using the χ² test. Kaplan-Meier analysis was performed to evaluate event-free time, and a Cox regression model was used to analyze the effects of event rates over time. Multivariable analysis was performed to correct for demographic variables that differed significantly between active and passive fixation leads. Results were considered significant at two-tailed P values <0.05.

Results

Baseline Clinical Characteristics

The clinical characteristics of the patients are summarized in Table 1. LV lead placement was successful in 183 (100%) patients between January 2018 and June 2021. The mean age of the patients was 68.8 years, and 75% were male. The proportion of patients with heart failure with ischemic etiology was 31%, LV ejection fraction (LVEF) was 26±7%, and the proportion of patients with left bundle branch block (LBBB) was 32%, all of which were not significantly different between the 2 groups. The baseline characteristics, echocardiographic parameters, and electrocardiographic parameters were similar between the 2 groups.

Table 1.

Baseline Clinical Characteristics in the Medtronic ASQ and Non-ASQ Groups

	All patients (n=183)	ASQ (n=69)	Non-ASQ (n=114)	P value
Age (years)	68.8±12.8	71.0±11.7	67.4±13.3	0.071
Male sex	137 (75)	53 (77)	84 (74)	0.639
NYHA functional class				0.352
Class II	112 (61)	44 (64)	68 (58)
Class III	45 (25)	13 (19)	32 (28)
Class IV	26 (14)	12 (17)	14 (12)
Ischemic cardiomyopathy	56 (31)	27 (39)	29 (25)	0.052
Echocardiographic findings
LVDd (ms)	63±10	63±10	63±10	0.963
LVDs (ms)	55±11	56±11	55±11	0.671
LVEF (%)	26±7	25±7	26±7	0.281
LVEDV (mL)	204±90	207±88	202±92	0.741
LVESV (mL)	155±87	160±84	152±89	0.585
Electrocardiographic findings
QRS width (ms)	158±27	160±25	157±28	0.483
QRS waveform				0.838
LBBB	59 (32)	23 (33)	36 (32)
RBBB	22 (12)	10 (14)	12 (11)
IVCD	42 (23)	15 (22)	27 (24)
Pacing waveform	60 (33)	21 (30)	39 (34)
Comorbidities
Hypertension	72 (39)	33 (48)	39 (34)	0.068
Atrial fibrillation	65 (36)	22 (32)	43 (38)	0.424
Diabetes	63 (34)	28 (41)	35 (31)	0.173

Unless indicated otherwise, values are presented as n (%), the number of positive findings per number of patients (%), or the mean±SD. ASQ, Attain Stability Quad; IVCD, intraventricular conduction disturbance; LBBB, left bundle branch block; LBBB, left bundle branch block; LVDd, left ventricular diastolic diameter; LVDs, left ventricular systolic diameter; LVEDV, left ventricular end-diastolic volume; LVEF, left ventricular ejection fraction; LVESV, left ventricular end-systolic volume; NYHA, New York Heart Association; RBBB, right bundle branch block.

Procedural Characteristics

The characteristics of the implantation procedures are listed in Table 2. The frequency of CRT defibrillator implantation was 84%, and 66% of all patients underwent de novo implantation of LV leads, neither of which differed significantly between the 2 groups. LV lead tip locations and pacing sites in the 2 groups are shown in Figure 1. The LV lead tip location at implantation was significantly more common in the apical region in the case of the passive fixation lead (36.0% vs. 14.5%; P=0.005). The LV lead pacing threshold at implantation was 1.13±0.68 V/0.43±0.12 ms, and the impedance was 652±206 Ω, which was either similar in both groups. Lead-related complications did not occur during the procedure.

Table 2.

Characteristics of Implantation Procedures in the Medtronic ASQ and Non-ASQ Groups

Characteristics	All patients (n=183)	ASQ (n=69)	Non-ASQ (n=114)	P value
Device type				0.487
CRT-P	30 (16)	13 (19)	17 (15)
CRT-D	153 (84)	56 (81)	97 (85)
De novo implant	121 (66)	48 (70)	73 (64)	0.444
LV lead tip location				0.005
Apical	51 (28)	10 (14)	41 (36)
Middle	125 (68)	55 (80)	70 (61)
Basal	7 (4)	4 (6)	3 (3)
LV lead pacing site				0.144
Apical	24 (13)	5 (7)	19 (17)
Middle	111 (61)	43 (62)	68 (60)
Basal	48 (26)	21 (30)	27 (24)
Electrical parameters
LV threshold (V)	1.13±0.68	1.18±0.83	1.10±0.55	0.488
LV pulse width (ms)	0.43±0.12	0.41±0.08	0.45±0.14	0.132
LV lead impedance (Ω)	652±206	642±219	660±196	0.606

Unless indicated otherwise, values are presented as n (%), the number of positive findings per number of patients (%), or the mean±SD. ASQ, Attain Stability Quad; CRT-D, cardiac resynchronization therapy defibrillator; CRT-P, cardiac resynchronization therapy pacing; LV, left ventricular.

Figure 1.

Left ventricular (LV) lead locations and pacing sites in the Medtronic Attain Stability Quad (ASQ) and non-ASQ groups. MCV, middle cardiac vein.

Occurrence of Postoperative LV Lead-Related Complications

From postimplantation to the first outpatient visit after discharge, the frequency of LV lead-related complications was significantly lower in the ASQ than non-ASQ group (14% [n=10] vs. 30% [n=34], respectively; P=0.019; Table 3A). Only one case of LV lead dislodgement was reported in the non-ASQ group, and elevated PCT levels were significantly lower in the ASQ group (7% vs. 23%; P=0.007). During the follow-up period (median [interquartile range] 382 [287–511] and 849 [525–1,184] days in the ASQ and non-ASQ groups, respectively), 68 patients had postoperative LV lead-related complications (12 [17%] and 56 [49%] patients in the ASQ and non-ASQ groups, respectively), including 54 patients with elevated PCT, 21 with PNS, and 1 with dislodgement (Table 3B). Pericardial effusions and cardiac tamponade associated with the procedure were not observed in either group.

Table 3.

LV Lead-Related Complications in the Medtronic ASQ and Non-ASQ Groups

	All patients (n=183)	ASQ (n=69)	Non-ASQ (n=114)	P value
A. At the first outpatient visit after implantation; 1 month after implantation
Electrical parameters
LV threshold (V)	1.48±0.87	1.21±0.87	1.64±1.02	0.004
LV pulse width (ms)	0.43±0.14	0.41±0.07	0.44±0.17	0.121
LV lead impedance (Ω)	635±207	624±143	641±237	0.601
LV lead-related complication	44 (24)	10 (14)	34 (30)	0.019
Elevated LV pacing capture threshold	31 (17)	5 (7)	26 (23)	0.007
Phrenic nerve stimulation	15 (8)	5 (7)	10 (9)	0.715
LV lead dislodgement	1 (1)	0 (0)	1 (1)
B. At follow-up
Median [IQR] follow-up period (days)	595 [310–994]	382 [287–511]	849 [525–1,184]
LV lead-related complication	68 (37)	12 (17)	56 (49)
Elevated LV pacing capture threshold	54 (30)	6 (9)	48 (35)
Phrenic nerve stimulation	21 (11)	6 (9)	15 (13)
LV lead dislodgement	1 (1)	0 (0)	1 (1)

Unless indicated otherwise, values are presented as n (%), the number of positive findings per number of patients (%), or the mean±SD. IQR, interquartile range. Other abbreviations as in Tables 1,2.

Figure 2 shows Kaplan-Meier analysis demonstrating a persistently higher rate of freedom from LV lead-related complications after CRT device implantation in patients implanted with an ASQ lead (log-rank P=0.005). The frequency of LV lead-related complications at the 6-month postoperative follow-up was 19.4% in the ASQ group and 36.4% in the non-ASQ group (P=0.020). As shown in Figure 2, the non-ASQ group continued to have LV lead-related complications long after implantation, whereas the ASQ group did not have any complications at 6 months postoperatively.

Figure 2.

Kaplan-Meier curves for left ventricular (LV) lead-related complications during follow-up in the Medtronic Attain Stability Quad (ASQ) and non-ASQ groups. IQR, interquartile range.

The frequency of required reoperations for LV lead dislodgement and LV lead elevated PCT or PNS requiring polarity change at the 6-month postoperative follow-up was lower in the ASQ than non-ASQ group (12.9% vs. 21.7%, respectively), but the difference was not significant (P=0.156). Kaplan-Meier analysis for required reoperation with LV lead dislodgement or required polarity change with LV lead elevated PCT or PNS during follow-up is shown in Figure 3, with a significantly lower event rate in the ASQ group (log-rank P=0.036). Furthermore, Cox multivariable regression analysis showed a significant reduction in lead-related complications associated with ASQ leads (hazard ratio 0.44; 95% confidence interval 0.23–0.83; P=0.011; Table 4).

Figure 3.

Kaplan-Meier curves for required reoperation for left ventricular (LV) lead dislodgement and LV lead-related complications of elevated pacing capture threshold (PCT) or phrenic nerve stimulation (PNS) requiring a polarity change during follow-up in the Medtronic Attain Stability Quad (ASQ) and non-ASQ groups.

Table 4.

Predictors of Occurrence LV Lead-Related Complications According to Cox Proportional Hazards Analysis

Predictors	Univariable model		Multivariable model
	HR (95% CI)	P value	HR (95% CI)	P value
Age, per 1-year increase	1.01 (0.99–1.03)	0.162
Ischemic cardiomyopathy	0.98 (0.58–1.66)	0.946
LVEF, per 1% increase	1.03 (1.00–1.06)	0.097
LVDd, per 1-mm increase	0.98 (0.95–1.00)	0.083
LVDs, per 1-mm increase	0.98 (0.96–1.00)	0.123
LVEDV, per 1-mL increase	1.00 (0.99–1.00)	0.137
LVESV, per 1-mL increase	1.00 (0.99–1.00)	0.118
QRS duration, per 1-ms increase	1.00 (0.99–1.01)	0.613
LBBB	0.44 (0.24–0.79)	0.006	0.51 (0.27–0.96)	0.035
CRT-D	0.78 (0.43–1.43)	0.430
De novo implantation	0.54 (0.33–0.87)	0.011	0.70 (0.42–1.17)	0.172
LV apical pacing	1.46 (0.77–2.79)	0.247
ASQ lead	0.42 (0.22–0.79)	0.007	0.44 (0.23–0.83)	0.011

CI, confidence interval; HR, hazard ratio. Other abbreviations as in Tables 1,2.

Discussion

The major finding of this study was that the ASQ group had fewer postoperative LV lead-related complications requiring intervention and setting changes than the conventional non-ASQ group. These findings suggest that active fixation leads may be an acceptable first choice for CRT device implantation. The dislodgement rate of non-ASQ leads requiring reoperation is reported to be 1.4–4.4% at 3–9 months.^9,18,19 To overcome this problem, active LV fixation leads have been developed. De Regibus et al reported that LV lead dislodgement requiring reoperation was less than 1% for both quadripolar and bipolar active fixation leads over 1–2 years.¹⁹ In the present study, LV lead dislodgement was not observed in the ASQ group.

Although there have been reports of postoperative LV lead capture loss in ASQ and non-ASQ leads,¹⁹ no reports have compared ASQ and non-ASQ leads in terms of setting changes due to postoperative elevated PCT. In our study, at 1 month after implantation, 5 (7%) patients in the ASQ group had elevated PCT levels, 4 required polarity changes, and 3 required output increases. 26 (23%) patients in the non-ASQ group had elevated PCT levels; 17 required a polarity change and 13 required an increase in output. Although there were no elevated PCT levels requiring reoperation, a shortening of battery life associated with elevated pacing output was observed. In addition, the change in LV pacing polarity may have affected the effectiveness of CRT because the pacing polarity was changed from the site originally determined to be the appropriate pacing site.

Keilegavlen et al reported that 16% of patients had PNS at 12 months.²⁰ PNS is also generally more common when the tip of the LV lead is placed in the apical and posterolateral middle, with a reported lower risk for placement in the basal or anterior positions.²¹ In the present study, the introduction of the ASQ led to less PNS due to the stability of the postoperative LV lead and its non-apical placement. It has been reported that approximately 30% of heart failure patients are non-responders to CRT.²² Suboptimal LV lead position is considered one of the factors for non-response, and the inability to place the LV lead at the optimal pacing site reduces the effectiveness of CRT.²³ A subanalysis of the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) reported that pacing from the apex of the heart resulted in a worse response to CRT.²⁴ In our study, as shown in Figure 1, the tip of the ASQ lead was located in the middle in most cases and was less often placed at the apex than the non-ASQ lead. When the vessel is large and PCT is high, owing to inadequate fixation of the pacing electrode, the lead may be located on a smaller apical branch, compromising pacing at the preferred site. The ASQ lead, which can be located more basally, has an advantage over the non-ASQ lead. The ASQ lead allows for multiple available electrodes⁸ and may prevent elevated PCT, PNS, and worsening of response to CRT.

In the present study, unlike the non-ASQ group, the ASQ group did not have any complications after 6 months postoperatively. This may be because ASQ leads are firmly fixed to the vessel wall, whereas non-ASQ leads have an unstable fixation. There may be concerns about the removability of the active fixation of the LV leads. In contrast to conventional non-ASQ leads, ASQ leads are anchored to a vessel wall via a side helix. Recent case reports on the safety of LV lead extraction have been limited^25–26 and remain an issue for the future.

Study Limitations

This single-center retrospective cohort study has several limitations. First, it was limited by the sample size and follow-up period. The active fixation LV lead group currently has a follow-up period of approximately 1 year for most patients. Future studies are needed to increase the number of patients and evaluate longer follow-up data. Second, confounding is an issue because LV lead selection according to venous anatomy, LV lead tip location, and LV pacing polarity during surgery are determined at the surgeon’s discretion. Future prospective randomized trials are recommended on this topic. Third, in cases with elevated PCT or PNS levels during follow-up, there were no criteria for changing the output or polarity of the LV lead, which was decided by outpatient physicians at their discretion. In this study, patients with elevated PCT levels were considered for polarity change rather than output change if the increasing LV pacing output resulted in a postimplantation battery life of 5 years. Fourth, no pericardial effusions or cardiac tamponade associated with the procedure were observed in this study, but the presence of pericardial effusions was not routinely confirmed by echocardiography after the procedure, so potentially asymptomatic pericardial effusion may be present.

Conclusions

The ASQ group had fewer LV lead-related complications requiring reintervention and setting changes than the non-ASQ group. These findings suggest that a quadripolar active fixation lead may be an acceptable first-choice treatment for CRT device implantation.

Sources of Funding

This study did not receive any specific funding.

Disclosures

K.K., N.U., and K.I. have received remuneration for lectures from Medtronic Japan Inc. S.N. is affiliated with a department endowed by Medtronic Japan, Inc. The other authors have no conflicts of interest to declare.

IRB Information

This study was approved by the Institutional Review Board of the National Cerebral and Cardiovascular Center (M26-150-12).

Data Availability

The deidentified participant data will not be shared.

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