Abstract

Aims

Left ventricular (LV) lead dislodgement occurs in about 10.6% of patients in the first 12 months after cardiac resynchronization therapy defibrillator implantation, and causes lack of clinical improvement, repeated surgery, and predisposes to infective complications and death. To understand the factors predictive of lead dislodgement, and to investigate whether bipolar LV lead stabilization can reduce the dislodgement rate and improve the clinical outcome.

Methods and results

Predisposing coronary vein anatomy was identified on a retrospective series of 218 patients implanted before August 2009. Lead stabilization guided by vein anatomy was prospectively tested on consecutive patients from October 2009 to December 2010. Among 84 patients, lead stabilization based on vein anatomy was recommended in 19 patients, of which 16 agreed and 3 refused. Two of these latter had lead dislodgement within 1 month, whereas none of the former had adverse events during 23.8 ± 3.1 months follow-up. Only 1 of 58 patients deemed at low risk had lead dislodgement. Seven patients required lead stabilization for severe phrenic stimulation issues that dictated lead placement at specific sites. Patients with stabilized LV leads were more likely to be cardiac resynchronization therapy (CRT) responders than the others: 19 of 26 (73%) vs. 34 of 58 (59%, P= NS), and had a significantly higher proportion of super-responders: 12 of 26 (46%) vs. 12 of 58 (21%, P< 0.005).

Conclusion

Coronary vein anatomy may assist decision making about the need for LV lead stabilization, and the choice of tools during the implanting procedure to ensure effective CRT delivery at long term.

What's new?

  • Left ventricular lead dislodgement is underreported in the literature, being at least 10% at 1-year follow-up. It occurs more frequently in coronary veins close to the coronary sinus (CS) os and an upward course, and in veins with a flat take-off at a >80° angle from the CS.

  • Lead stabilization by stenting, based on coronary vein anatomy, can effectively reduce dislodgement rate from 10 to 1%.

  • Lead performance is unaffected by the stenting procedure, and extraction was possible in a single patient 27 months after implantation.

Introduction

Cardiac resynchronization therapy (CRT) effectiveness is significantly hindered in 30% of recipients for several reasons; beyond the patients' selection issue, loss of left ventricular (LV) stimulation plays an important role. Loss of LV stimulation occurs mainly because of LV lead dislodgement, that is reported to range from 2 to 12% of patients in different reports.1–6 In our centre, the incidence of LV lead dislodgement within 1 year after CRT implantation remained substantially unchanged through the decade 1999–2009, ranging from 8.1 to 9.8%. In this period, we sporadically resorted to LV lead stabilization by stenting inside a coronary vein in very specific situations. Hence, we sought to understand whether some predictors of LV dislodgement could be identified, and whether LV lead stabilization could ensure the retention of effective LV stimulation at the targeted site.

Methods

Patient populations and protocol

The present study was conducted at the Institute of Cardiology of Bologna University in two consecutive groups of patients to identify the conditions requiring coronary sinus (CS) side branch stenting in CRT. The study comprised of two phases: (i) identification of the coronary vein anatomy associated with LV lead dislodgement in a retrospective cohort; (ii) verification of a stabilization strategy based on coronary vein anatomy in a prospective cohort. To identify the predictors of lead dislodgement, we first retrospectively analysed the angiograms of 218 consecutive patients who underwent CRT in our Institute between 1 November 2005 and 31 January 2009 to study the anatomy of the coronary veins chosen as target for LV lead implantation, and to understand possible vein characteristics that might predispose to LV lead dislodgement. Afterwards, a total of 84 consecutive heart failure patients undergoing CRT implantation in the period 1 October 2009 to 31 December 2010 were prospectively observed: LV lead stenting was offered as an opportunity to prevent a possible LV lead dislodgement when a vein anatomy that was found associated with LV dislodgement in the 218 patients series was observed, or in the event of a phrenic nerve stimulation (PNS) pacing threshold issue that dictated an unstable lead placement (acceptable LV pacing threshold: ≤2.5 V@1 ms; minimum accepted difference between phrenic stimulation threshold and LV threshold: 2.5 V). Prior to CRT device implantation, patients gave informed consent to a possible lead-stenting procedure in the event of an anticipated dislodgement risk based on the abovementioned issues. The study was approved by the Hospital Ethics Committee.

Cardiac resynchronization therapy implantation

After the CS venogram was obtained using a balloon catheter, a coronary vein leading to a posterior/lateral pacing site was chosen as the target to deliver the LV pacing lead in all the patients. Anterior LV lead placements were never allowed. All the patients received bipolar LV leads and a CRT device capable of programming any of the two LV electrodes as a cathode, to enable more possibilities to manage a phrenic stimulation and/or a high LV threshold issue.7–9 The assessment of the vein anatomy was made using the 25°–35° right anterior oblique view, caudal if needed, that enables us to display the posterior and lateral veins in full length and the visualization of the angle between the coronary branches and the CS. Confirmation of a posterior–lateral LV ventricular site was made by a 40° left anterior oblique view, cranial if needed. Coronary veins anatomy was classified according to this scheme (see also Figures 1–3): Stabilization by lead stenting could be achieved either by the use of a single delivery sheath inside the CS, employing the 4196 Attain lead (Medtronic Inc.), or by the use of two delivery sheaths when a larger size LV lead (≥5F) was preferred. Indeed, all the CS delivery sheaths available at our centre had an inner lumen of 7F. When a vein subselector was used for cannulation of the coronary veins, two commercially available stiff guidewires were placed in the target vein to support tracking of either the LV lead and the stent wire-delivery system. Bare metal stents, 2.5–5 mm diameter and 8–12 mm in length according to vein size to meet a 1 : 1 ratio, were used. No antiplatelet or drug therapy other than that clinically ongoing before the procedure was specifically used either during or after lead stenting. Balloon inflation occurred proximal to the ring electrode of the LV lead, at a maximum pressure of 18 Atm for no longer than 4 s. All the patients had scheduled device follow-up every 3 months.

Figure 1

Type A veins (origin close to the CS os and an upward course to a posterior/lateral stimulation site) predisposing to LV lead dislodgement (A) vs. not vulnerable to lead dislodgement (B). Note the absence of sizable side branches in the former.

Figure 1

Type A veins (origin close to the CS os and an upward course to a posterior/lateral stimulation site) predisposing to LV lead dislodgement (A) vs. not vulnerable to lead dislodgement (B). Note the absence of sizable side branches in the former.

Figure 2

Type B veins (take-off angle from the CS > 80°) predisposing to LV lead dislodgement (A) vs. not vulnerable to lead dislodgement (two patients, B). Note the absence of sizable side branches in the former, and the guidewire in place for the stabilization procedure.

Figure 2

Type B veins (take-off angle from the CS > 80°) predisposing to LV lead dislodgement (A) vs. not vulnerable to lead dislodgement (two patients, B). Note the absence of sizable side branches in the former, and the guidewire in place for the stabilization procedure.

Figure 3

Type C veins (take-off angle from the CS < 80°) predisposing to LV lead dislodgement (two patients, A) vs. not vulnerable to lead dislodgement (B). An unstable placement related to a PNS avoidance strategy or to a pacing threshold issue mandates lead stabilization.

Figure 3

Type C veins (take-off angle from the CS < 80°) predisposing to LV lead dislodgement (two patients, A) vs. not vulnerable to lead dislodgement (B). An unstable placement related to a PNS avoidance strategy or to a pacing threshold issue mandates lead stabilization.

  • Type A veins: origin between the CS os and the proximal third of the CS, upward course to a lateral or posterior–lateral pacing site (Figure 1);

  • Type B veins: veins with a flat take-off from the CS at an angle >80° (Figure 2);

  • Type C veins: veins with a ≤80° take-off or a gooseneck take-off from the CS (Figure 3).

Echocardiography

All the patients underwent a complete cardiological evaluation and trans-thoracic echocardiogram prior to CRT implantation and at 6 months follow-up. Trans-thoracic echocardiography was performed with a commercially available ultrasound transducer and equipment (iE33, Philips Medical Systems).

Left ventricular end-diastolic volume and left ventricular end-systolic volume (LVESV) were calculated using Simpson's biplane method. Left ventricular ejection fraction was calculated and expressed as a percentage. The response to CRT was defined based on LV reverse remodelling at 6 months follow-up, according to the criteria used by Ypenburg et al.10 The reproducibility of echocardiographic measurements in our centre has been previously reported.11

Statistical analysis

All continuous variables are presented as mean and standard deviation. Categorical variables are presented as frequencies and percentages, and were compared using χ2 of Fisher's exact probability test, as appropriate. Student's t-test was used to compare paired and unpaired continuous variables. All statistical tests were two-sided, and a P < 0.05 was considered significant. A statistical software program SPSS 16.0 (SPSS Inc.) was used for all statistical analysis.

Results

Retrospective patient population

Baseline characteristics of the retrospective analysis of 218 CRT patients are reported in Table 1. Of note, LV lead dislodgement requiring surgical revision because of loss of LV stimulation occurred in 21 of 218 (9.6%) of the patients (Table 2). Most LV lead dislodgements (16 of 218, 7.3%) occurred in the first 6 months, the remaining five (2.3%) occurred between 6 and 12 months follow-up. These five ‘late dislodgements’ were observed in CRT responder/super-responders with >20% decrease of LVESV. No LV dislodgement occurred after 12 months follow-up. Only 7 of 21 patients had the target vein still patent after dislodgement, and had lead repositioning with stabilization in the same vein, whereas 14 patients had occluded target veins that could not be targeted again. Dislodgement had occurred within the first month in 6 of 7 patients of the former group, and in 2 of 14 of the latter, respectively (P< 0.005). Although the use of different LV leads from various manufacturers was unevenly distributed according to vein size and length, lead shape, or size were not associated with an enhanced stability (Table 1).

Table 1

Characteristics of the retrospective patient population

 Overall population (n = 218) 
Demographic  
 Age (years) 66 ± 14 
 Male [n, (%)] 159 (73) 
Medical history [n, (%)]  
 Diabetes 46 (21) 
 Ischaemic aetiology 59 (27) 
 Hypertension 103 (47) 
 Dyslipidaemia 107 (49) 
Medications [n, (%)]  
 ACE inhibitor/AGT II blockers 189 (87) 
 Beta-blockers 193 (89) 
 Diuretics 190 (88) 
 Nitrates 13 (6) 
 Statins 82 (38) 
 Oral anticoagulants/aspirin 181 (83) 
Clinical characteristics  
 NYHA functional class III, IV [n, (%)] 201 (92) 
 QRS duration (ms) 158 ± 31 
Echocardiographic characteristics  
 LV end-diastolic volume (mL) 222 ± 82 
 LV end-systolic volume (mL) 163 ± 70 
 LV ejection fraction (%) 27 ± 8 
CRT issues  
 Responders to CRT by ECHO [n, (%)] 135 (62) 
 Super-responders by ECHO [n, (%)] 57 (26) 
 LV lead dislodgements 21 (9.6) 
 Overall population (n = 218) 
Demographic  
 Age (years) 66 ± 14 
 Male [n, (%)] 159 (73) 
Medical history [n, (%)]  
 Diabetes 46 (21) 
 Ischaemic aetiology 59 (27) 
 Hypertension 103 (47) 
 Dyslipidaemia 107 (49) 
Medications [n, (%)]  
 ACE inhibitor/AGT II blockers 189 (87) 
 Beta-blockers 193 (89) 
 Diuretics 190 (88) 
 Nitrates 13 (6) 
 Statins 82 (38) 
 Oral anticoagulants/aspirin 181 (83) 
Clinical characteristics  
 NYHA functional class III, IV [n, (%)] 201 (92) 
 QRS duration (ms) 158 ± 31 
Echocardiographic characteristics  
 LV end-diastolic volume (mL) 222 ± 82 
 LV end-systolic volume (mL) 163 ± 70 
 LV ejection fraction (%) 27 ± 8 
CRT issues  
 Responders to CRT by ECHO [n, (%)] 135 (62) 
 Super-responders by ECHO [n, (%)] 57 (26) 
 LV lead dislodgements 21 (9.6) 

ACE, angiotensin converting enzyme; AGT II, angiotensin II; ECHO, echocardiography; LV, left ventricular; NYHA, New York Heart Association.

Table 2

Implanted leads and dislodgement rates at 1-year follow-up

Implanted leads Total, n (%) Dislodgement, n (%) 
Medtronic 4193 12 (5.6) 1 (8.3) 
Medtronic 4194 34 (16) 3 (8.8) 
Medtronic 4196 80 (37) 6 (7.5) 
Boston Scientific Easytrack 2 14 (6.4) 2 (14) 
Boston Scientific Easytrack 3 16 (7) 1 (6.2) 
Boston Scientific Acuity Steerable 16 (7) 2 (12.5) 
St Jude Medical 1056 T 46 (21) 6 (13) 
Implanted leads Total, n (%) Dislodgement, n (%) 
Medtronic 4193 12 (5.6) 1 (8.3) 
Medtronic 4194 34 (16) 3 (8.8) 
Medtronic 4196 80 (37) 6 (7.5) 
Boston Scientific Easytrack 2 14 (6.4) 2 (14) 
Boston Scientific Easytrack 3 16 (7) 1 (6.2) 
Boston Scientific Acuity Steerable 16 (7) 2 (12.5) 
St Jude Medical 1056 T 46 (21) 6 (13) 

Type A veins were chosen as target in 31 of 218 (14.2%) of patients, Type B veins were targeted in 84 of 218 (38.5%) of patients, whereas Type C were targeted in 103 of 218 (47.2%) of patients. Dislodgement rate requiring repeated surgery was 8 of 31 (25.8%) in Type A vein, 12 of 84 (14.3%) in Type B veins, and 1 of 103 (0.9%) in Type C veins. No dislodgements were observed when the lead was wedged in a side branch of the target vein that hosted the distal LV lead at least 10 mm in length (Figures 1 and 2, Panel B).

In the absence of branches suitable for lead wedging, the dislodgement rates were: 8 of 19 (42%) for Type A veins, 12 of 62 (19%) for Type B veins, and 1 of 47 (2%) for Type C veins.

Based on this evaluation of coronary veins anatomy, we prospectively planned our implantation activity from the period 1 October 2009 to 31 December 2010: LV lead stabilization to prevent lead dislodgement was offered to patients with Type A and Type B veins who did not have side branches suitable for lead wedging, and to those who had an unstable lead placement due to PNS or high pacing threshold management in any vein (Figure 4).

Figure 4

Flowchart used in our prospective observational study on 84 patients from 1 October 2009 to 31 December 2010.

Figure 4

Flowchart used in our prospective observational study on 84 patients from 1 October 2009 to 31 December 2010.

Prospective patient population

Baseline characteristics of the 84 CRT patients prospectively enroled from October 2009 to December 2010 are reported in Table 3. Follow-up ended in December 2012.

Table 3

Characteristics of the prospective study population, according to the strategy of lead placement

    Patients with stabilized LV leads Patients with non-stabilized LV leads ALL P value 
n = 26 n = 58 n = 84 
Clinical characteristics [n, (%)] 
 Age  65 ± 17 67 ± 13 66 ± 14 0.60 
 Male  18 (69) 37 (64) 55 (65) 0.63 
 NYHA functional class IV  2 (8) 6 (10) 8 (10) 0.91 
 Ischaemic aetiology  5 (19) 21 (36) 26 (30) 0.40 
 Diabetes  2 (8) 14 (24) 16 (19) 0.15 
 Hypertension  13 (50) 21 (36) 34 (40) 0.12 
 Dyslipidaemia  9 (35) 29 (50) 38 (45) 0.30 
 QRS duration (ms)  161 ± 26 158 ± 28 159 ± 27 0.61 
 LV end-diastolic volume (mL) Implant 207 ± 66 202 ± 55 203 ± 45 0.7 
Follow-up 180 ± 73 183 ± 64 185 ± 66 0.84 
 LV end-systolic volume (mL) Implant 153 ± 52 143 ± 42 146 ± 45 0.34 
Follow-up 113 ± 53 118 ± 52 116 ± 52 0.73 
 LV ejection fraction (%) Baseline 26 ± 6 29 ± 7 28 ± 7 0.069 
Follow-up 38 ± 9 37 ± 10 38 ± 10 0.69 
 Responders by ECHO  19 (73) 34 (59) 53 (63) 0.3 
 Super-responders by ECHO  12 (46) 12 (21) 24 (29) 0.041 
 LV pacing threshold (V@0.4 ms) Implant 1.1 ± 0.6 1.0 ± 0.6 1.0 ± 0.6 0.67 
Follow-up 1.2 ± 0.7 1.1 ± 0.7 1.2 ± 0.7 0.44 
 LV pacing impedance (Ω) Implant 634 ± 220 621 ± 164 625 ± 181 0.76 
Follow-up 623 ± 266 584 ± 173 596 ± 205 0.44 
Medications [n, (%)] 
 CE inhibitor/angiotensin receptor blockers  25 (99) 55 (94) 80 (95) 0.65 
 Beta-blockers  25 (99) 55 (95) 80 (95) 0.78 
 Diuretics  22 (85) 49 (84) 71 (84) 0.83 
 Oral anticoagulants/aspirin  23 (88) 51 (88) 74 (88) 0.72 
Implanted leads 
 Medtronic 4196  21 (80) 40 (69) 61 (72) 0.72 
 Medtronic 4296  1 (4) 4 (7) 5 (6) 
 Boston Scientific Easytrack 2  1 (4) 4 (7) 5 (6) 
 Boston Scientific Easytrack 3  1 (4) 4 (7) 5 (6) 
 Boston Scientific Acuity Steerable  1 (4) 3 (5) 4 (5) 
 St Jude Medical 1056 T  1 (4) 3 (5) 4 (5) 
Total procedure time (min) 
 Median (interquartile range)  183 (155–186) 172 (156–180) 175 (156–180) 0.29 
    Patients with stabilized LV leads Patients with non-stabilized LV leads ALL P value 
n = 26 n = 58 n = 84 
Clinical characteristics [n, (%)] 
 Age  65 ± 17 67 ± 13 66 ± 14 0.60 
 Male  18 (69) 37 (64) 55 (65) 0.63 
 NYHA functional class IV  2 (8) 6 (10) 8 (10) 0.91 
 Ischaemic aetiology  5 (19) 21 (36) 26 (30) 0.40 
 Diabetes  2 (8) 14 (24) 16 (19) 0.15 
 Hypertension  13 (50) 21 (36) 34 (40) 0.12 
 Dyslipidaemia  9 (35) 29 (50) 38 (45) 0.30 
 QRS duration (ms)  161 ± 26 158 ± 28 159 ± 27 0.61 
 LV end-diastolic volume (mL) Implant 207 ± 66 202 ± 55 203 ± 45 0.7 
Follow-up 180 ± 73 183 ± 64 185 ± 66 0.84 
 LV end-systolic volume (mL) Implant 153 ± 52 143 ± 42 146 ± 45 0.34 
Follow-up 113 ± 53 118 ± 52 116 ± 52 0.73 
 LV ejection fraction (%) Baseline 26 ± 6 29 ± 7 28 ± 7 0.069 
Follow-up 38 ± 9 37 ± 10 38 ± 10 0.69 
 Responders by ECHO  19 (73) 34 (59) 53 (63) 0.3 
 Super-responders by ECHO  12 (46) 12 (21) 24 (29) 0.041 
 LV pacing threshold (V@0.4 ms) Implant 1.1 ± 0.6 1.0 ± 0.6 1.0 ± 0.6 0.67 
Follow-up 1.2 ± 0.7 1.1 ± 0.7 1.2 ± 0.7 0.44 
 LV pacing impedance (Ω) Implant 634 ± 220 621 ± 164 625 ± 181 0.76 
Follow-up 623 ± 266 584 ± 173 596 ± 205 0.44 
Medications [n, (%)] 
 CE inhibitor/angiotensin receptor blockers  25 (99) 55 (94) 80 (95) 0.65 
 Beta-blockers  25 (99) 55 (95) 80 (95) 0.78 
 Diuretics  22 (85) 49 (84) 71 (84) 0.83 
 Oral anticoagulants/aspirin  23 (88) 51 (88) 74 (88) 0.72 
Implanted leads 
 Medtronic 4196  21 (80) 40 (69) 61 (72) 0.72 
 Medtronic 4296  1 (4) 4 (7) 5 (6) 
 Boston Scientific Easytrack 2  1 (4) 4 (7) 5 (6) 
 Boston Scientific Easytrack 3  1 (4) 4 (7) 5 (6) 
 Boston Scientific Acuity Steerable  1 (4) 3 (5) 4 (5) 
 St Jude Medical 1056 T  1 (4) 3 (5) 4 (5) 
Total procedure time (min) 
 Median (interquartile range)  183 (155–186) 172 (156–180) 175 (156–180) 0.29 

CE, converting enzyme; ECHO, echocardiography; LV, left ventricular.

During the implant, four patients declined to participate in the study owing to a lengthy procedure (difficult subclavian vein puncture in one, difficult access to the CS in two, and difficult lead trackability in one).

Left ventricular lead dislodgement causing loss of LV stimulation occurred in 3 of 84 patients (3.5%), 2 of which had declined participation and refused lead stabilization as recommended by the target vein anatomy. The third patient had been deemed at low risk of dislodgement based on the vein angiogram (Type C). According to the abovementioned criteria, 26 of 84 (30%) patients underwent lead stabilization in the target vein, 23 at the implant procedure, and 3 at the repositioning procedure after lead dislodgement, respectively. Nineteen lead stabilization procedures were dictated by vein anatomy and seven by PNS management causing lead instability. Out of the 19 of 84 (22%) patients deemed at risk of lead dislodgement based on vein anatomy alone, 16 agreed and 3 declined participation to the study: of these latter, 2 of 3 had lead dislodgement within the first month (1 Type A and 1 Type B vein), and agreed to lead stabilization during the repositioning procedure. Seven patients (8%, two Type B and five Type C veins) had to be managed with stenting because of a severe PNS issue that required LV repositioning at basal-to-mid sites, where the LV lead proved unstable. One patient with a Type C vein, who was not deemed at dislodgement risk, had indeed lead dislodgement after 10 days and underwent reoperation with lead stabilization.

No adverse events like coronary vein dissection/perforation or pericardial effusion occurred in any of the 84 patients.

Patients treated with lead stabilization vs. others

Baseline parameters of patients treated with lead stabilization vs. others are reported in Table 3. Of note, no differences in clinical, electrocardiographic, and echocardiographic parameters were observed between the two groups. The average follow-up was 23.9 ± 3 months in the stabilized-lead group compared with 23.7 ± 3.2 months in the non-stabilized group (P = NS). None of the patients with a stabilized LV lead had lead dislodgement or an LV stimulation threshold increase >0.75 V; one (3.8%) had a phrenic to LV pacing threshold difference = 2.25 V at 1 year and required reprogramming of the pacing output to avoid PNS. On the contrary, 3 of 58 (5.1%) of non-stabilized patients had lead dislodgement that was treated at repositioning. Among these 58 patients, 2 (3.4%) needed pacing vector reprogramming to avoid PNS, and 2 (3.4%) had a >0.75 V increase of LV pacing threshold.

Objective response to CRT by 6 months echocardiography, according to the criteria reported by Ypenburg et al.,10 was slightly but not significantly more frequent in patients with stabilized leads, who indeed had a significantly higher proportion of super-responders (Table 3). Seven patients (8.3%) died: three in the stabilized group (one acute renal failure, two cancer), and four in the non-stabilized group (three end-stage heart failure, one cerebral bleeding). Baseline and long-term follow-up LV lead pacing parameters were similar in both groups (Table 3). No patient had an infection of the implanted system during follow-up. One lead has been recently extracted by manual traction in a patient undergoing heart transplantation 27 months after implantation.

Discussion

In this study, we report a strategy based on the coronary veins angiogram to possibly reduce the risk of LV lead dislodgement leading to loss of LV stimulation after the implantation of a CRT device. We observed that veins with an inferior origin close to the CS os and an upward course to a posterior–lateral site, and posterior–lateral veins with a flat take-off at an angle >80° from the CS are at the highest risk of lead dislodgement, especially when no sides branches to wedge the LV lead are available. The approach based purely on vein anatomy led us to stabilize 22% of leads, that compares favourably with our historical 9.6% dislodgement rate, although it clearly represents an overestimation of the dislodgement risk. When all patients with LV lead instability due to a placement dictated to manage a phrenic stimulation and/or a high LV pacing threshold issue were added, nearly 30% of patients underwent lead stabilization.

Incidence of lead dislodgement

This complication ranges widely in the literature, depending on several factors such as follow-up duration, placement site of the LV lead (anterior vs postero-lateral), operator experience, and mechanical factors,12 but can be assumed to be 6–8% at 6-months follow-up.1–6,13–15 We observed that the dislodgement rate was similar to the literature at 6 months in our practice (7.3%), but reached 9.6% at 1 year, when reverse remodelling had occurred. In the only other study reporting the 1-year follow-up, it occurred in 10.6% of patients.16 Although this observation can find a reasonable explanation in the change of the LV lead interplay with the targeted vein, owing to the decrease of LV volume that causes a new ‘reciprocal relationship’ with the LV lead, it was never reported before. Coronary vein size, lead slack, and branch angle are key factors for lead stability,12 that can change the interplay lead-to-vessel when reverse remodelling occurs, therefore causing an increased propensity to lead dislodgement. Indeed, our observations in the retrospective cohort found the greatest dislodgement risk being associated with the same vein anatomy as predicted by the mechanical model by Zhao et al.12 Beyond these anatomical/mechanical factors, lead dislodgement is also affected by actions taken to manage PNS/pacing threshold issues, that may also ‘cluster’ together in a minority of patients.17 Indeed, PNS and pacing threshold management are challenging in about 6.5% of patients despite the use of bipolar LV leads and of electronic programmability of LV stimulation.8,18

Effect of left ventricular lead stabilization

Left ventricular lead stabilization at a desired site warrants stability and enables a satisfactory pacing threshold and/or avoidance of PNS. The first experiences with active-fixation LV leads did not ensure avoidance of phrenic stimulation in all the patients,9,19 since the lead was unipolar, thereby not enabling any electronic management of PNS.7–9,17,18 Stabilization of LV leads has been proposed to overcome both the PNS and the cardiac pacing threshold issue in a pioneering study at the Heart Center of Semmelweis University20 over 5 years in 39% of 784 CRT recipients, and has proved effective in terms of treatment and prevention of lead displacement, as well as safe in terms of lead integrity on the long-term follow-up (up to 36 months). In that experience, 296 of 312 lead-stenting procedures were dictated mainly by instability due to the management of phrenic stimulation and sometimes by minor/major intra-operative lead dislocations.20 Our study adds the potential for the implanting physician to foresee a lead stabilization strategy soon after the coronary angiogram is taken, despite the use of multipolar LV leads for PNS avoidance. This knowledge is indeed crucial, as only 30% of target veins were still patent when dislodgement occurred after the first month in our retrospective population; in Burke's experience, complete vein occlusion was observed with indwelling leads for longer than 3 months.21 Moreover, the prediction of a high dislodgement risk mandates the choice of appropriate implantation tools, as it is impossible to accommodate a ≥5F LV lead and the stent-delivery system within the same CS delivery sheath. The use of a 4F bipolar lead is mandatory when dual delivery-sheath placements in the CS and/or dual coronary vein cannulation are not feasible/preferred.

As outlined in Geller's experience,20 delivery sheaths with an effective lumen ≥8F are needed to accomplish efficiently this task when a bipolar LV lead other than Attain 4196 (Medtronic Inc.) is employed, whereas a 7F sheath can accommodate either Attain 4196 or unipolar LV leads.

Some differences can be found between the large series by Geller et al.20 and our study, namely the different proportion of patients treated by lead stenting (39.7 vs. 30%), and the primary reason for lead stabilization (management of PNS vs. prevention of lead dislodgement). Both may be largely attributed to the use of unipolar leads in their study (305 of 312 patients), whereas all our patients received bipolar leads, that may offer some advantages in the management of PNS7–9,17,18 with a lower risk to reposition the lead to proximal sites, that endangers lead dislodgement.8,17,20 Theoretically, the use of quadripolar LV leads may offer further advantage in the management of PNS,22 and in the avoidance of repositioning the lead to unstable basal pacing sites due to scarred myocardium in ischaemic heart disease patients, thereby reducing the risk of dislodgement and thus the need for lead stabilization. This expectation has not been proved in clinical practice,23 Quartet™ (St Jude Medical Inc.) dislodgement rate being 3.5% at 3 months.24 Indeed, a clinical trial (More-CRT) comparing bipolar vs. quadripolar LV leads is currently going on to investigate this hypothesis, since LV stimulation from proximal electrodes frequently results in very high pacing thresholds, and is therefore of limited clinical usefulness in a sizeable group of patients.22,24,25

Given the challenges that still hinder LV stimulation, the development of active-fixation LV leads is long-awaited to ensure a stable lead placement at the target site and retain effective CRT delivery at long term, thereby enabling reverse LV remodelling and decreased mortality.26,27 In fact, more patients were super-responders in the stabilized group, whose overall objective responder rate (73%) was similar to the TARGET trial.26 On the other hand, concern about lead extraction feasibility has until now slowed the development of active-fixation LV leads. Such concern should deflate, considering that redo procedures, particularly when a lead revision is involved, are the major predisposing factors to CRT defibrillator system infections.28,29 Moreover, lead dislodgement is associated with clinical adverse events and an increased in-hospital mortality.30

Long-term reliability of left ventricular lead stabilization

The pacing performance of the LV leads in both Geller's series20 and our study was satisfactory and stable at long term; in their experience, they were able to demonstrate only minor surface damage of the stent on the lead insulator. Moreover, a tissue layer between the lead and the stent was observed in explanted hearts,20 that is possibly related to an easy lead extraction up to 4 years after implantation.20 In their study, they were able to remove the stented LV lead in seven patients during follow-up.20 In our single patient, it was possible to remove an indwelling lead for 27 months with simple traction, as the local fixation provided by the stent is far from being firm, owing to the great compliance of the vein wall.

Study limitations

This was not a randomized study, owing to the small size of the population, therefore, it has to be interpreted as a pilot investigation of a lead stabilization strategy. Further study is needed to identify the dislodgement risk in a better manner, and to minimize stabilization procedures. Nonetheless, we believe that our anatomical approach to the dislodgement issue deserves consideration in the view of upcoming new active-fixation LV leads.

Conclusions

Left ventricular lead dislodgement is a threatened complication that may prevent a successful re-implantation in the target vein in nearly 70% of patients, and predisposes to infective complications28,29 and to an adverse clinical outcome.30 Our data clearly suggest that prevention of lead dislodgement by bipolar LV lead stabilization is feasible when guided by coronary vein anatomy. When multipolar active-fixation LV leads will become available, our observation may assist implanters in the choice of the appropriate LV lead, to achieve and retain LV stimulation at the targeted pacing site.

Conflict of interest: none declared.

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