Discussion:
Over the last decade, the utilization rate of catheter ablation (CA) has
steadily increased as an important therapy for ventricular tachycardia
(VT). [7] Despite significant advancements in electroanatomic
mapping systems and imaging technologies, VT ablation is still
associated with a risk of significant complications. A decision to
perform the procedure includes balancing those risks against potential
benefits. [8] Typically, patients with VT have complex underlying
comorbidities that contribute to morbidity and mortality following the
ablation procedure. [9] Previous clinical trials have been conducted
to assess the efficacy and safety of VT ablation. [10] However, many
of these studies have excluded specific populations, such as those with
renal dysfunction. [11] Our study aims to fill this gap by
addressing the association of chronic kidney disease (CKD) with
in-hospital mortality and complications following VT ablation using a
real-world large administrative database. Proper understanding of the
risks of VT ablation in this population will have significant clinical
implications on CKD patients with VT, by identifying therapeutic
strategies that can improve survival and by guiding patient counseling.
In-hospital mortality has been widely used in the literature as an
important outcome measure for invasive cardiology procedures. In this
multi-center registry, in-hospital mortality was our primary outcome,
and it occurred in 3.2% of VT patients undergoing CA, higher than the
mortality rates reported in previous similar studies. A retrospective
study from National Inpatient Sample (NIS) database (2006-2013), have
revealed a 2.8% in-hospital mortality rate among 25,451 patients
undergoing VT ablation. [5] The higher mortality rate in recent
years could be due to the increased number of patients with a higher
burden of comorbidities undergoing VT ablation or due to a rising number
of low-volume centers performing VT ablation with decreased access to
equipment and personnel. [7] Our study adds to the current
literature by highlighting the association between in-hospital mortality
and CKD status (OR=2.24; 95% CI: 1.29-3.88, p=0.004), particularly CKD
stage IV (OR=4.48 95% CI 1.79 – 11.2, p<0.01). These
findings are comparable with Palanismawy et al. who reported a similar
association between CKD and in-hospital mortality following CA (OR=2.15;
95% CI: 1.12-4.14, p=0.022), among 81,539 patients with postinfarct VT
identified through NIS. [7]
Thirty-day readmission is another important indicator for the success of
the VT ablation procedure in high-risk patients. [12] According to
Sharma et al, who used NRD data from 2010 to 2014, 1 in 6 patients was
readmitted within 30 days after undergoing VT ablation. The most common
cause of 30-day readmission after the index hospitalization for VT
ablation was ventricular arrhythmia (39.51%) followed by acute
congestive heart failure (11.83%). Moreover, they investigated the
different predictors of 30-day readmission and found a significant
association with CKD (OR=1.3; 95% CI: 1.1-1.6, p=0.01). [3] Our
study using the same database from 2016 to 2018 did not find a
statistically significant association between CKD status and 30-day
readmission rates due to ventricular arrhythmia after adjusting for
confounders (OR=1.35; 95% CI: 0.78-2.31, p=0.27).
Given the complexity of VT catheter ablation procedure and the high
comorbidity burden among patients undergoing this procedure, the length
of stay and the hospital costs hospitalizations following the procedure
are significant. [13] A study conducted by Cheung et al reported a
median length of stay of the index admission of 4.3 days, while the mean
length of stay in our study was 6.4 days (8.73 in CKD patients).
[12] Moreover, we found that the mean hospital charges in CKD
patients undergoing VT ablation were 226,796 USD, compared with 176,249
USD in patients without CKD. These associations were most significant in
patients with CKD stage V. This remarkable difference in length of stay
and hospital costs could have important implications on resource
allocation in hospitals performing VT ablation.
The association between CKD and worse outcomes in patients undergoing VT
ablation is complex and could be related to structural cardiac
abnormalities caused by CKD, in addition to several triggers in this
population. Firstly, CKD leads to progressive coronary calcification and
coronary artery disease, which is considered the most common etiology of
VT in these patients also CKD can make intra-op volume management more
challenging, thus CKD may be related to less complete ablation. [14]
CKD patients are also at risk for QTc-prolongation due to impairment of
cardiac repolarization mechanisms. [15] In addition, CKD patients
undergoing hemodialysis are affected by electrolyte shifts, such as
sudden potassium and calcium shifts, leading to a mechanical and
electrical imbalance in the cardiac myocytes. [16] Other underlying
mechanisms for this imbalance could be attributed to oxidative stress,
increased levels, and the accumulation of several cardiotoxic substances
such as homocysteine b2-microglobulin, and parathyroid hormone [17]
The present study contributes to a better understanding of this
high-risk subgroup of patients undergoing VT ablation. Development of a
nationally valid risk stratification model and improving post-hospital
care have the potential to offset some of the risks inherent to ablating
VT in CKD patients.