Definitions:
VT storm: ≥ 3 sustained episodes of VT within a 24 hour period,
each requiring termination by an intervention (1).
Refractory VT: Incessant sustained VT that recurred promptly
despite repeated intervention over several hours (15).
Arrhythmia management prior to CSD: All the patients were
put on maximum tolerated antiarrhythmic drugs prior to considering CSD
(table 1). The ICDs were programmed on individual case basis to minimize
shock discharges, such as longer detection duration for first VT zone,
more antitachycardia pacing (ATP) for VT, no shocks for the
1stVT zone, etc. Reversible factors such as myocardial
ischemia and electrolyte disturbances were addressed. Deep sedation or
general anesthesia (GA) with endotracheal intubation was taken on case
to case basis depending upon the clinical status. Radiofrequency
ablation of VT was also performed in suitable patients prior to CSD.
Despite the above measures, arrhythmias persisted in all these patients
and thus were subjected to CSD. TEA was attempted in few patients prior
to CSD.
CSD Operative details: A video assisted thoracoscopic
surgical (VATS) approach under GA was utilized in all patients for CSD.
Three 1.5 cm incisions were made in the sub-axillary area to access the
pleural cavity. The ipsilateral lung was collapsed with single lung
ventilation except in 4 patients where conventional intubation was
performed and CO2 insufflation of the pleural cavity was used. The
thoracic sympathetic chain was identified in the pre-vertebral region.
The lower half of the stellate ganglion along with thoracic sympathetic
ganglia from level T2 to T4 were resected out and cauterized. The chest
drain was removed after confirmation of lung re-expansion. Histological
confirmation of the tissue removed was also obtained.
Definition of response to CSD: Response to CSD was
assessed on the basis of occurrence of sustained VT requiring ICD shocks
or external defibrillator after two weeks of CSD. We did not take into
account anyshocks between CSD till two weeks after CSD and considered
that period as ‘blanking period’. This is because we postulated that CSD
would take atleast two weeks for decreasing the circulating levels of
epinephrine and norepinephrine.
Complete response: Defined as>75%
reduction in the episodes of VT requiring ICD shockor external
defibrillationcompared to before CSD.
Partial response: Defined as 50-75% reduction in the
episodes of VT requiring ICD shock or external defibrillation in the
follow-up period after CSD compared to before CSD.
No response: Defined as < 50% reduction in
the episodes of VT requiring ICD shock or external defibrillation in the
follow-up period after CSD compared to before CSD.
Delayed response: It was observed from our earlier case
results that, patients usually show clinical response to CSD within 2
weeks of surgery. However lateron we also observed some patients
continued to have shocks after CSD till three months but no requirement
of shocks after three months. We considered such patients as delayed
responders.
Statistical methods: Continuous variables were expressed
as mean±SD or median and interquartile ranges [IQRs] and categorical
variables, as percentages. The Kolmogorov-Smirnov test was performed
which showed the data to be not normally distributed. Wilcoxon Signed
Ranks test was used to determine differences between groups.
Kaplan-Meier survival curves were used to estimate freedom from
recurrent ICD shock and death. Log-rank test was used to compare Kaplan-
Meier curves. For Kaplan- Meier analysis of freedom from ICD shock and
death, patients who were lost to follow-up were censored at the time of
last follow-up. A p value of <0.05 was considered significant.
Statistical analysis was performed using SPSS software (Version 26,
Chicago, IL, USA)