Discussion
The current approach to chronic symptomatic lead related venous
obstruction is unsatisfactory. Balloon dilation, to relieve the
obstruction, results in symptom recurrence in a short duration and
reintervention is required. Stenting without prior lead extraction is
not considered to be an option. Even when leads are extracted, and
stents deployed the results are not well defined. Given the apparent
similarity between dilating a dialysis fistula and lead related venous
obstruction the addition of a drug coated balloon to high pressure
balloon dilation was considered a favorable option. Subclavian stenosis
has been observed in approximately 15% of patients prior to device
placement and increases up to 50% after transvenous manipulation (5).
Although many factors are involved in the development of vascular
occlusion the two primary processes involved are: thrombus formation and
neointimal hyperplasia with subsequent fibrosis. In the acute settings
thrombus formation around the lead can lead to acute symptoms for which
anticoagulative agents are often used to reduce the risk of embolic
complications while collaterals develop. Lead placement also irritates
the venous endothelium inducing an inflammatory cascade leading to
excessive proliferation of the connective tissue resulting in a fibrotic
occlusion (5).
Multiple strategies have been attempted for patients with chronic
symptomatic lead related venous obstruction. Surgical approaches
predominated in the 1990s until the advent of percutaneous techniques
and subsequent introduction of balloon dilation. Riley et al (6)
conducted the first retrospective pooled analysis of 104 patients with
symptomatic lead associated superior vena cava syndrome and reported
that the most common treatment approach superior with the lowest rate of
restenosis. However stenting results in compression of the lead between
the stent and the wall of the vein referred to as ‘jailing’ of the lead.
‘Jailing’ can compromise lead integrity and/or result in fracture.
Jailing also complicates lead removal in the cases of infection. The
current Heart Rhythm Society expert consensus is to extract transvenous
leads before stenting, to avoid their entrapment (7).
In the Mayo clinic (8) six patients identified with lead associated
symptomatic superior vena syndrome had stent implantation performed
after successful lead removal followed by reimplantation of the leads
however some patients required reintervention. Anticoagulation and
antiplatelet therapy have also been utilized in chronic occlusions but
have produced conflicting results, with majority studies reporting that
anticoagulant or antiplatelet use was not associated with a decreased
incidence of venous stenosis or thrombosis (2)(9) due to their
ineffectiveness on chronic fibrotic lesions, that often exist in these
patients, rather than atherosclerotic lesions (6). In a study done at
Cleveland Clinic (10) 861 device leads were histologically examined
after extraction, in patients with leads for > 1 year, and
examination of tissue demonstrated dense fibrous tissue with the
presence of calcification. From these histological findings the nature
of the tissue involved can help guide further treatment.
Worley et al (11) performed balloon fibroplasty in 371 asymptomatic
patients with significant subclavian stenosis to facilitate lead
revision or upgrade demonstrating the safety and practicality of
subclavian balloon fibroplasty, using non-complaint balloons. Balloon
dilation is the standard treatment in end stage renal disease (ESRD)
patients with stenosis of their arteriovenous fistulas (AVF). Compared
to standard non-compliant balloons (Rate Burst Pressure 20 ATM)
ultra-noncompliant high-pressure balloons (Rate Burst Pressure 30 ATM)
improve fistula patency. However even with high pressure balloons
(12)(13) durability was limited thus stenting was added in an attempt to
prolong patency. However even stents for AVF were associated with a high
risk of restenosis. Due to the meager long terms successes of balloon
angioplasty and vascular stents Kitrou et al (14) and Lookstein et al
(15) studied the effect of PCBs on dysfunctional AVF. Because of their
low rated burst pressure, PCBs, required pre-dilation with high pressure
balloons to dilate the hard stenotic and rigid lesions in the
vasculature. Adding PCB demonstrated superiority to both non-compliant
balloons and high-pressure balloons in maintaining target vessel patency
at 6 months with non-inferior primary safety end points. PCBs also
significantly extended the event-free period for the AVF circuit.
Presumably, deliverance of local drug-delivery device inhibits the
process of neointimal hyperplasia and enabled a longer intervention-free
period.
The stenosis observed in an AVF is due to endothelial irritation leading
to tissue proliferation and subsequent fibrosis. It is likely that the
fibrotic occlusion associated with chronic leads is similar to that
observed in patients with AVF. Our report describes the first addition
of DCB for subclavian fibroplasty in a symptomatic patient with chronic
transvenous leads. Because DCBs have been proven safe and effective in
maintaining patency of stenotic dialysis fistulas (16)(17) they may help
improve long term patency in symptomatic lead related obstruction. When
fibroplasty is performed for access in asymptomatic patients with
chronic leads the vein quickly reocclude. The addition of a PCB balloon
may be useful in maintaining patency.
To know for certain whether PCB improve patency in chronic symptomatic
patients with lead related obstruction requires a randomized trial.
However, given the limited alternatives it is important to consider the
addition of a PCB to balloon dilation as an option for patients with
symptomatic venous obstruction before resorting to extraction and
stenting. PCB may also prove useful in maintaining patency in
asymptomatic patients requiring fibroplasty for lead replacement or
upgrade.