Initially, a series of 309 consecutive patients that underwent catheter ablation of VT between 2012 and 2015 at the Heart Centre of Leipzig were included. The cohort consisted of 186 patients with ICM and 123 with non-ischemic cardiomyopathy (NICM). Patients with no structural heart disease (SHD) were excluded from the study. Classification took place after examining the patients with a combination of echocardiography, stress-test, coronary angiography, MRI or heart-biopsy. NICM was identified as an absence of relevant coronary artery disease and defined according to the criteria of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. Chronic renal failure was present when the patient had a glomerular filter rate (GFR) of < 60 ml/min/1.73 m². All patients gave written informed consent for the procedure, as is in accordance with the institutional guidelines. The study was approved by the ethics committee. The decision on LVAD implantation or heart transplantation was based on clinical and haemodynamic data according to current guidelines. Whether the LVAD device was used as bridge to transplantation, bridge to decision or destination therapy was decided in the current HXT committee. After the initial cohort and their data were gathered, a matched case control study for the 21 patients receiving an LVAD, HTX or both was performed during follow-up. The patients were matched for age, gender, LVEF and LVEDV.

The methodology of the procedure has been described in detail elsewhere [11]. In brief, after deep sedation, femoral vein access was used to place one decapolar catheter in the coronary sinus and one quadripolar catheter in the right ventricular apex. A multichannel recording system (Prucka CardioLab; GE Healthcare, Waukesha, WI, USA) was used for the signal’s recording and ventricular stimulation to induce the VT. Fluoroscopy-guided transseptal puncture was used to access the left atrium (LA) and a long sheath (Agilis® Abbott Medical, St Paul, MN, USA) was introduced into the LA. When an epicardial approach was needed, an epicardial puncture and a long sheath (Agilis-EPI® Abbott Medical, St Paul, MN, USA) were used. Electroanatomic mapping was performed using the CARTO‑3 system (Biosense Webster, Diamond Bar, CA, USA) or the EnSite-Velocity Navigation system (St. Jude Medical, St. Paul, MN, USA). Radiofrequency alternating current was delivered in a unipolar mode between the irrigated tip electrode of the ablation catheter (F-Type, irrigated tip, Thermocool, Biosense Webster, Diamond Bar, CA, USA; Therapy™ Cool Flex™ Ablation Catheter, St Jude Medical, MN, USA) and an external backplate electrode. An upper temperature limit of 42 °C, a power of 40–50 W and a flow rate of up to 30 mL/min comprised the standard ablation settings. The procedure was deemed successful if all VTs were ablated and no more VTs were inducible.

Follow-up included a review of records of all hospital and outpatient clinic visits and discussions with referring cardiologists and primary care physicians from the first ablation to the time of death/last visit or contact. If patients reported VT recurrence, additional examinations were provided. When indicated, the patients were treated with re-do procedures or additional antiarrhythmic drugs during follow-up. If the clinical status of the patients deteriorated, they were evaluated and listed for LVAD/HTX, according to the indications suggested by the existing guidelines. The patients with implanted LVAD or after HTX were routinely examined every 4–6 months in the authors’ outpatient clinic. If the patient had an intracardiac defibrillator/pacemaker, routine device interrogation was also performed to detect asymptomatic arrhythmias.

Case control matching was performed according to patient age, gender, LVEF and LVEDV to create a database of matched patients with or without LVAD/HTX during follow-up using SPSS software (SPSS Inc., Chicago, IL, USA). Continuous variables were reported as mean ± standard deviation and categorical variables as frequencies. Continuous variables were compared using the Student’s t-test, while categorical variables were compared using the χ² test. Univariate and multivariate analyses were performed in order to determine the predictive factors. Variables with a P-value of ≤ 0.2 or important clinical or procedural variables in the univariate analysis were then included in the multivariate regression analysis for the determination of hazard ratio (HR) and its 95% confidence interval (CI). A P-value of ≤ 0.05 was considered to be statistically significant. Survival rates were calculated and depicted with the Kaplan-Meier analysis. All analyses were performed using SPSS v24.0 (SPSS Inc., Chicago, IL, USA).

Table 1 shows the baseline patients characteristics, procedural data and long-term outcome. The mean follow-up duration was 44 ± 33 months. During this time, 15 patients underwent LVAD implantation and nine were transplanted. Three patients were implanted with an LVAD before eventually receiving an HTX. With the exception of more patients in the control group having chronic obstructive pulmonary disease (COPD) (p = 0.014), the other baseline characteristics, as well as the procedural data did not differ significantly between the two groups.

In this matched cohort, 16 deaths occurred in the first 44 months after VT ablation: seven in the control group and nine in the LVAD/HTX group (Table 2). All deaths in the LVAD/HTX group occurred in LVAD recipients, while all patients receiving HTX survived follow-up. Three patients in the control group died of end-stage global heart failure, one after refractory VTs, two of sepsis and one death remained unclear. In the LVAD group, two patients died of right heart failure (one of them resulting from refractory VTs), two suffered lethal endocranial bleeding or stroke postoperatively, two died due to sepsis, one did not survive a postoperative acute abdomen, one died from an LVAD dysfunction and one death remained unclear. Evidently, the cause of death between the groups is different, with end-stage heart failure being the main lethal factor in the control group, whereas in the LVAD group right heart failure and device-associated complications (bleeding, infection, etc.) were the main causes of death.

Using univariate testing, DM, chronic renal impairment, COPD and periprocedural complications were associated with higher mortality (Table 2). Multivariate Cox regression survival analysis revealed that none of these parameters was an independent predictor of mortality.

While HTX patients all survived the follow-up, the LVAD recipients showed a similar survival to the control group (Log-rank: 0.761, Fig. 1). The type of structural heart disease or the presence of recurrence did not differ in mortality rates in this patient cohort (p = 0.715, p = 0.325, respectively). On the same note, a higher PAINESD score was not a predictor of mortality in the present cohort (p = 0.616).