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)