Corresponding Author:
Jackson J. Liang, DO
Electrophysiology Section, Division of Cardiology
Cardiovascular Center, University of Michigan Medical Center
Ann Arbor, MI 48104
Email: liangjac@med.umich.edu
Catheter ablation is an effective treatment option for patients with
ventricular arrhythmias including premature ventricular complexes (PVCs)
and ventricular tachycardia (VT). Ventricular arrhythmias can be a
source of significant morbidity and mortality in patients with mitral
valve (MV) disease, including those who have undergone MV surgery such
as valve repair or replacement. The incidence of sustained VT in this
population tends to be bimodal occurring either in the postoperative
period or years after valve surgery.1,2 VT after MV
surgery can have multiple mechanisms including bundle branch reentry or
may involve circuits related to non-ischemic, operative, or ischemic
scar.1-3 Given the proximity of the mitral annulus to
the left His-Purkinje system, bundle branch reentry predominates in the
immediate postoperative period whereas scar based reentry typically
presents years after operation.1,2 Meanwhile, PVCs
coexisting with MV disease can be idiopathic in nature, result from scar
related to prior myocardial infarction or nonischemic process, or may
also be related to arrhythmic mitral valve prolapse (MVP). In the
lattermost context, PVCs originating from the papillary muscles or basal
left ventricle (LV) may serve as triggers for polymorphic VT and
ventricular fibrillation.3 Catheter ablation in these
patients with prior MV surgery may be associated with higher risk of
procedural complications due to concern for increased risk of
thromboembolism, catheter entrapment in MV prostheses, and possible
increased risk of bleeding complications due to need for uninterrupted
anticoagulation. Furthermore, the underlying arrhythmia substrates in
patients with MV surgery remain poorly defined. While catheter ablation
for VT has been shown to be safe and effective in patients with valvular
heart disease who have undergone aortic valve
replacement,4 there has been limited data describing
the electrophysiologic substrates, mapping and ablation techniques,
safety, and efficacy outcomes of PVC and VT ablation among patients with
prior MV surgery.
In this issue of the Journal of Cardiovascular Electrophysiology ,
Khalil, Killu, et al. report the Mayo Clinic experience of 31 patients
with prior MV surgery (24 with MV repair and 7 MV replacement [4
bioprosthetic, 3 mechanical]) who underwent catheter ablation for PVCs
(n=15) or VT (n=16) over a 6-year period.5 A total of
9 patients had ischemic cardiomyopathy and 9 patients had prior MVP.
Ablation in the LV was performed via a transseptal (n=17) or
retro-aortic (n=13) approach, with one patient treated with combined
transseptal and epicardial approach. Consistent with prior series,
presentation for PVCs and VT typically occurred years after surgery
(median 3.4 years for PVC and 4 years for VT) and ablation was performed
a median of 4 (for PVCs) and 5 (for VT) years after MV surgery. In
nearly two thirds of patients, clinical arrhythmia was targeted at sites
distant from the MV with the perimitral region being involved in only 6
patients with VT and 5 with PVCs, and perimitral scar was seen in 45%
of the PVC group and 50% of the VT group. Ablation was acutely
successful in 94% of the VT group and 93% in the PVC group, with only
2 patients having acute procedure failure (1 VT patient with
hemodynamically unstable VT requiring percutaneous LV assist device with
presumed epicardial isthmus in whom percutaneous epicardial access was
not attempted in the setting of prior sternotomy, and 1 PVC patient with
LV summit PVC which failed due to proximity of site of origin to the
left anterior descending artery). There were no procedural complications
reported (including no catheter entrapment and no significant change in
MV function before versus after ablation). Over a median follow up
duration of 478 days, survival free from recurrent ventricular arrythmia
was achieved in 72% (67% VT, 78% PVC).
This results of this study suggest that when performed by experienced
and skilled operators, catheter ablation for PVCs and VT in patients
with prior MV surgery can be a safe and effective treatment option.
These challenging procedures can be quite time-consuming (mean total
procedure duration and energy delivery time of 299 minutes and 64
minutes for VT; 255 minutes and 21 minutes for PVC) and may require
relatively high amounts of fluoroscopy (mean fluoroscopy time 36 minutes
for VT and 28 minutes for PVC), but ultimately acute and long-term
procedural success can be achieved in the majority of patients.
As has been mentioned by the authors in the manuscript, several issues
can make catheter ablation more complicated and challenging in these
patients. First, in patients with prior valve surgery, percutaneous
epicardial access can be prohibitive due to presence of extensive
pericardial adhesions. As such, one should consider having a cardiac
surgeon readily available on backup support in case complications of
percutaneous epicardial access are encountered, or to permit conversion
to surgical epicardial access if percutaneous access cannot be obtained.
Importantly, mapping via the coronary venous system and its branches
should be considered in all patients with suspected epicardial or
intramural substrates, especially those with perimitral substrate, as
often perivalvular substrates can be targeted with ablation from the
coronary venous system directly, or with ablation from adjacent chambers
via an anatomic approach. Management of pre-, intra-, and
post-procedural anticoagulation is of critical importance particularly
in patients with mechanical MV replacement, in whom procedures should be
performed on uninterrupted anticoagulation. While hemostasis was
achieved using manual compression in all patients in the authors’
series, we have found the use of vascular closure devices (Perclose
ProStyle; Abbott, Chicago, IL) to be especially helpful to achieve
hemostasis for both arterial and venous accesses, negating the need for
protamine reversal, permitting continued uninterrupted anticoagulation,
and facilitating early ambulation. Additionally, pre-procedural imaging
such as transesophageal echocardiogram, cardiac computed tomography
angiography, or intracardiac echocardiography (ICE) should be considered
in all patients with atrial fibrillation to exclude presence of left
atrial thrombus, especially if a transseptal approach is being
considered. While ICE views can be limited due to substantial
echo-artifact from prosthetic material (especially in patients with
mechanical MV replacement), ICE remains an extremely helpful tool to
guide mapping and ablation in these patients, and to avoid complications
particularly when manipulating the ablation catheter near mitral valve
prostheses. Also, color Doppler of the MV should be performed
intraoperatively during periods of acute hypotension as well as at the
end of the procedure to assess MV function. Finally, multipolar
catheters (especially circular multielectrode mapping catheters) should
be avoided near the MV apparatus to avoid catheter entrapment which
could result in catastrophic consequences. The series does not include
all possible scenarios after MV surgery and no patients with dual
mechanic valves in the aortic and mitral position were included. These
are the most challenging patients with prior MV surgery where the
typical access route to the LV is not possible and alternative
strategies such as transapical or trans-ventricular septal (or right
atrial to LV) access may be necessary.6-8 Another
intriguing question that is not answered in this series is the potential
role of surgery in the setting of bileaflet MVP to reduce arrhythmia
burden. While the authors did not report in this series the incidence of
ventricular arrhythmias before versus after MV surgery in those patients
with MVP, prior small retrospective studies (including data from the
authors’ group) have suggested that MV intervention might reduce
incidence of ventricular arrhythmias, both in the setting of bileaflet
MVP as well as in those with mitral regurgitation in the absence of
MVP.9-11 However, this hypothesis remains to be
confirmed in larger prospective studies.
We applaud the authors for sharing their institutional experience
describing techniques and outcomes of VT and PVC ablation in this
challenging patient population with prior MV surgery. This study is a
welcome addition to the literature demonstrating that LV ablation for
both PVCs and VT in patients with prior MV repair and replacement can be
performed both safely and effectively by experienced operators. Their
findings support the notion that catheter ablation should not be
withheld as a possible treatment option solely based on history of prior
MV surgery. Referral to a tertiary ablation center for management can be
considered, especially in more complicated, higher-risk cases.