DISCUSSION
This study documents the long-term outcomes of a C-ABL strategy in a
population of IHD and NICM patients. In our multicentric real-world
analysis, a C-ABL in patients undergoing a redo ablation was associated
with increased overall survival and VT-free survival. Direct comparison
of clinical outcomes between a NC-ABL and a C-ABL strategy for VT
ablation has been limited by heterogeneous patient characteristics and
lack of abundant comparative randomized trials4,5. ES
at presentation, LVEF, NYHA class III/IV, IHD and C-ABL have been
identified as independent predictors of VT-free survival, cardiovascular
and all-cause mortality in our study. IHD patients with previous
myocardial infarction and low ejection fraction are at an increased risk
of VT and sudden cardiac death1,3, and international
guidelines recommend ICD implantation1. However,
recurrent VT and ES are associated with increased mortality even in
patients with an ICD2. This may be related to a
progressive deterioration of cardiac function resulting from frequent
shocks, chronic low-cardiac output, and AAD therapy
toxicity8. Several studies have shown catheter
ablation superiority compared to AADs for VT treatment, with a success
rate of 51% to 67%9. The VANISH randomized
controlled trial10 showed that in patients with IHD
and an ICD with VT despite AAD therapy, VT ablation had a lower rate of
the composite primary outcome of death, ventricular tachycardia storm,
or appropriate ICD compared to AAD therapy escalation. An
endocardial-only ablation frequently does not eliminate all the
re-entrant circuits in IHD, which may lead to
relapse11. Also, the development and widespread use of
reperfusion therapies in the last decades led to a higher number of
patients with nontransmural necrosis and heterogeneous infarcted
tissues. These scars may have multiple slow conduction channels with
epicardial exit sites12, providing the rationale for a
C-ABL approach. Current guidelines have an IIB class recommendation for
the epicardial ablation in IHD after a failed endocardial
ablation3. However, there is an important knowledge
gap. Regarding this cardiomyopathy, Di Biase et all4showed that extensive scar homogenization with a combined endocardial
and epicardial approach in a first ablation procedure was linked to
increased VT-freedom in patients with ES. One possible explanation for
their findings is a greater amount and complexity of the arrhythmic
substrate in IHD with ES presentation, which can justify an initial
combined approach. Izquierdo et al13 showed that a
first combined endo-epicardial procedural was linked to fewer
hospitalizations but failed to show an increase in survival free of VT.
Sarkozy et all14 showed that two-thirds of the
patients selected for epicardial mapping after a failed endocardial
ablation had epicardial arrhythmic substrate and Acosta et
all15 showed that an endocardial ablation in patients
with transmural MI was associated with an increased risk of recurrence.
Tung et all16 showed better VT-free survival for IHD
patients after a combined endo-epi ablation vs. endocardial only, partly
explained by the high number of previous endocardial ablation (80%) in
their series. In our study, the arrhythmic relapse reduction was only
verified in the population that underwent more than one procedure. Our
analysis showed an increase in VT-free survival and a decrease in
all-cause death with a C-ABL in IHD patients with multiple ablations,
and to the best of our knowledge, this is the first individual study to
show this survival benefit. A recent meta-analysis17was also consistent with our findings, showing a reduction in all-cause
mortality and VT-recurrence in IHD. These combined findings suggest that
an epicardial ablation is probably the most effective strategy for VT
elimination and survival improvement after an initial failed endocardial
ablation in IHD. VT arrhythmogenic substrate differs from NICM and IHD
patients. An analysis of 445 patients undergoing VT ablation showed that
some NICM VT’s critical isthmi can’t be identified in either endo and
epicardium, possibly due to mid myocardial location18.
Current guidelines suggest an initial endocardial ablation, or possibly
a first epicardial ablation if the arrhythmia has characteristics
pointing to an epicardial origin18, and NICM patients
have shown VT-free survival from 41% to 70% at 1-year after the
procedure19. The worse outcomes of VT ablation in NICM
patients appear to be related to an intramural or epicardial
localization of the myocardial isthmus20. The acute
success and VT-freedom after catheter ablation in NICM patients are
associated with a reduction in mortality and heart
transplantation19. To the best of our knowledge, this
is the first study to show an improvement in VT-free survival and
reduction of all-cause death with a C-ABL compared to a NC-ABL in NICM
patients undergoing a redo procedure. The fundamental PS matching
principle is the homogenization of a chosen set of covariates according
to a dependent variable, in a pseudo-randomized controlled
design7. This statistic technique is of particular
interest in this setting since we are presented with 2 heterogeneous
groups with several potential confounding variables. PS matching allows
the reduction of the impact of other independent variables in the
outcome analysis, strengthing the findings of the initial analysis and
allowing a more accurate assessment of the safety outcomes. Serious and
potentially life-threating complications can be associated with the
epicardial ablation technique11,14,17. Common
procedure-related complications are right ventricular puncture,
subxiphoid bleeding, pericardial effusion, cardiac tamponade, coronary
arteries lesion, acute myocardial infarction, thoracic artery lesion,
complete heart block, phrenic nerve lesion, abdominal organ puncture,
and stroke. Our population has a high burden of traditional
cardiovascular risk factors (Table 1), and there was a considerable
amount of ES at presentation. Although this was a high-risk population,
our complication rate was comparable to the current reports in the
literature. In this real-world population analysis, the C-ABL strategy
had a similar safety profile when compared to the NC-ABL approach,
despite that the combined strategy featured a much higher number of
epicardial ablations. While we can not completely exclude the influence
of underpowering in the procedural complication rate analysis, the
potential benefit of this combined ablation appears to outweigh the
potential risks.