Introduction

Cardiogenic shock (CS) is an acute and life-threatening condition defined by a primary cardiac disorder resulting in low cardiac output, global tissue hypoperfusion, and organ dysfunction. Despite advances in treatment and the implementation of novel strategies, including mechanical circulatory supports (MCS), the prognosis of CS patients remains serious with 30-day mortality as high as 50% [1].

Heart rhythm disorders are common in CS patients. Arrhythmias can either represent a CS complication or can be the primary cause [2]. According to the available data, atrial fibrillation (AF) occurs in about 20% of CS cases and the incidence of ventricular fibrillation is reported to be 9–19% [3]. In 12% of patients, CS is triggered by sustained ventricular tachycardia (VT) [4]. Its presence leads to impaired ventricular contraction and diminished time for ventricular filling, both resulting in decreased cardiac output. Supraventricular arrhythmias (SVTs) are generally less dangerous. However, in patients with previous left ventricular dysfunction, even SVT can quickly lead to a deterioration [5]. It is important to remember that a persistent SVT can itself cause a left ventricle dysfunction known as tachycardia induced cardiomyopathy. When unrecognized and untreated, this can eventually present as an acute CS [6].

Immediate sinus rhythm restoration using electrical cardioversion is the first line treatment of arrhythmias in hemodynamically unstable patients, according to the guidelines. The management of recurrent or incessant arrhythmias is more challenging. Beside pharmacotherapy, catheter ablation is an established way of treatment for both supraventricular and ventricular arrhythmias [7–9].

Short-term MCS including VA ECMO and Impella devices should be considered in selected patients to achieve hemodynamic stability until the underlying cause of the CS can be addressed and heart function recovers [10]. In patients with recurrent arrhythmias, MCS removal is usually not feasible until the heart rhythm is stabilized. When pharmacotherapy and cardioversion fail, performing a successful catheter ablation on MCS may be a crucial step for both the successful management and the patient’s outcome (Fig 1).

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Fig 1. Arrhythmias in cardiogenic shock.

Arrhythmias can be the primary cause of CS or they can appear later as a secondary complication. Bail-out catheter ablation in patients on MCS is an option that should be considered when the heart rhythm disorder is causing a significant hemodynamic compromise and is resistant to other treatment modalities. Abbreviations: CS – cardiogenic shock, ggl. – ganglion, MCS – mechanical circulatory support, SVT – supraventricular tachycardia, VT – ventricular tachycardia. (Created in BioRender. Dusik, M. (2025) https://BioRender.com/x36g205).

https://doi.org/10.1371/journal.pone.0332597.g001

In this article, we provide a single-centre experience on the catheter ablation of treatment resistant supraventricular and ventricular arrhythmias in patients with cardiogenic shock treated by MCS.

Methods

We thoroughly screened a dedicated registry of adult patients who underwent catheter ablation in the tertiary cardiac centre (General University Hospital in Prague, Czech Republic) between January 2020 and August 2024 to retrospectively identify all eligible patients for this analysis. The main inclusion criteria were: (1) CS treated by a short-term MCS (VA ECMO, Impella device or their combination), and (2) the presence of a refractory arrhythmia preventing the MCS weaning that was treated by a catheter ablation. Both patients with supraventricular and ventricular arrhythmias were included, but their data were analysed separately. Another registry of all patients treated by MCS was used to validate the collected data (e.g., the patient had to be included in both registries (Ablation registry, MCS registry)) to fit this analysis. Further details were obtained from the patients’ medical records.

For this study, we used a definition of CS which is routinely accepted in our institution, including: (1) blood pressure lower than 90 mmHg or the need for catecholamines, (2) clinical signs of end-organ hypoperfusion, supported by (3) laboratory findings of elevated lactate and a decrease in the oxygen saturation of a mixed venous blood [11].

The patients included in this study were managed according to local standard protocols and current guidelines. The indication of a MCS implantation and choice of the best suitable MCS for each individual patient is based on the decision of a “shock team” consisting of an ICU physician, interventional cardiologist, and a heart failure specialist.

When a clinically significant arrhythmia appears, attempts are made to treat all possible underlying causes, including revascularization in coronary artery disease. As a next step, patients are placed on appropriate antiarrhythmic drugs. Furthermore, other measures suggested in the guidelines such as deep sedation, antitachycardic pacing, or stellate ganglion blockade are considered. The indication for a catheter ablation is based on a discussion between the shock team and the interventional electrophysiologists. The course of an ablation procedure then follows the valid guidelines according to the type of arrhythmia.

After discharge, CS patients are followed-up routinely at the outpatient clinic. For this analysis, a 30-day long follow-up period was chosen to reduce the number of patients lost, and to focus on the effect of the single catheter ablation intervention.

The study was performed according to the principles of good clinical practice and in compliance with the Declaration of Helsinki. The analysis of the registry was approved by the local ethical committee (approval No. 149/24 S-IV AP). The complete dataset was accessed for research purposes on the 01/11/2024. Authors had access to medical reports including information that could identify individual participants during or after data collection. Patient’s informed consent was waived given the retrospective and observational character.

The continuous variables are expressed as medians with interquartile range. The categorical variables are expressed as percentages.

Results

Ventricular tachycardias

We identified 9 CS patients (8 males, median age 69 years [IQR 60;74]) ablated for a refractory VT during the study period. Upon admission, 8 patients had a history of heart failure with reduced ejection fraction and 7 had a previously known coronary artery disease. An ICD had already been implanted in 5 patients. Three patients were admitted during the ongoing refractory cardiac arrest and the MCS implantation was performed as an extracorporeal cardiopulmonary resuscitation (ECPR) procedure. The median ejection fraction at the time of catheter ablation was 15% (IQR 10%; 20%) and the NT-proBNP value 6700 ng/l (IQR 4200; 12 100). Impella CP was used in 6 patients, 2 patients were on veno-arterial extracorporeal oxygenation (VA ECMO), and one patient was completely supported by the combination of VA ECMO and Impella CP for the left ventricle unloading (ECPELLA). The summary of patient’s characteristics is listed in Table 1.

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Table 1. Patient’s medical history and characteristics.

https://doi.org/10.1371/journal.pone.0332597.t001

Clinical arrhythmia was recognized as a monomorphic VT in 6 patients, 1 patient had episodes of ventricular fibrillation triggered by monomorphic premature ventricular beats (PVCs), 1 patient was finally diagnosed with bundle branch re-entry VT, and 1 patient was ablated for polymorphic VTs. Before the ablation, all patients were on an antiarrhythmic treatment which included amiodarone.

The ablation procedure was performed on median day 2 (IQR 1; 4) of MCS. The median procedure time was 140 minutes (IQR 125; 180) and the median time of radiofrequency energy application was 34 minutes (IQR 26; 43). Clinical arrhythmia was observed in 5 patients during the ablation. Interestingly, despite the use of MCS, the arrhythmia presence was poorly hemodynamically tolerated in 2 patients (severe pulmonary oedema in 1 patient on the VA ECMO and hypotension in 1 patient on Impella CP). In two patients we failed to induce tachycardia, and in two other patients the tachycardia induction was not even performed because of their overall poor condition. In those cases, the ablation was based solely on the substrate mapping. The location of the ablation lesions, together with other details, is summarized in Table 2.

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Table 2. Patients ablated for ventricular tachycardias—MCS and ablation details and outcomes.

https://doi.org/10.1371/journal.pone.0332597.t002

After the catheter ablation, 7/9 patients (78%) were successfully weaned off the MCS. The median total length of the MCS duration was 5 (IQR 1; 8) days. The one patient on ECPELLA who did not show signs of cardiac recovery was switched directly to a left ventricle assist device (LVAD) on the 8^th day post admission. Overall, 3 of the 9 patients who underwent ablation on MCS for refractory arrhythmia (33%) died during the first 30 days. One patient was consensually indicated to palliative care due to an overall poor state with multiorgan failure and died soon after the Impella weaning. Two other patients died from end-stage heart failure and multiorgan dysfunction several days after MCS removal. Ventricular arrhythmias recurred in 5/9 patients (56%). Two of them were those who subsequently died and one was the patient who underwent an early LVAD implantation as mentioned above. Post-ablation arrhythmias in the remaining two patients were successfully managed pharmacologically.

Clinically significant complications of MCS were reported in 6/9 patients (67%). Two patients had serious bleeding and required blood transfusions. Another two patients developed haemolysis leading to their renal function worsening while being on the ImpellaCP. The removal of the ImpellaCP using the Manta vascular closing device (Teleflex Inc., Morrisville, USA) in one patient with previously known peripheral artery disease was complicated by the acute limb ischemia due to the external iliac artery occlusion. This was solved by an acute surgical thrombectomy and endarterectomy, together with Manta device removal. One patient, after the emergent VA ECMO implantation during the ECPR, developed a significant arterio-venous fistula in the groin which required surgical ligation. The ablation procedure was complicated in only one patient by the transient complete heart block that required temporary ventricle pacing.

Supraventricular tachycardias

Overall, 4 CS patients were ablated for SVT while being on a MCS (3 males, median age 73 years [IQR 67; 78]). One patient was on a VA ECMO, 2 patients on Impella CP, and one on Impella 5.5. Three patients had a history of heart failure with reduced ejection fraction. One patient had a known heart failure with preserved ejection fraction. Significant coronary artery disease was found in only one patient. In all four patients, there were repeated efforts to manage the arrhythmias pharmacologically before indicating the ablation procedure.

AF with rapid ventricular response was an indication for catheter ablation in 3 of the patients. All those patients were treated by a non-selective AV node ablation. Prior to the procedure, 2 patients had had a cardiac resynchronization therapy (CRT) device implanted. In one patient, conduction system pacing was used instead. The final patient underwent a radiofrequency ablation of a focal atrial tachycardia originating from the region of the left atrium above the coronary sinus. The ablation procedure in this patient lead to profound bradycardia with the eventual need for a pacemaker implantation. Besides that, there were no other reported complications of the ablation procedure. Pacemaker implantation was complicated in one patient by delayed bleeding, which required surgical revision. No infectious complications related to leads and pacemakers were reported during the 30-day follow-up.

On average, the ablation procedure was performed on median day 7 (IQR 4,75; 7,5) of MCS insertion. The median procedure time was 45 (IQR 44; 71) minutes. All procedures were successful, and there was no arrhythmia recurrence documented during the follow-up. All patients were successfully weaned off the MCS after the ablation. The median duration of MCS support was 13 days (IQR 8,5; 20). No patient died during the 30-day period after the ablation. One patient on Impella CP suffered from considerable haemolysis. No other MCS complications were reported. The data is summarized in Table 3.

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Table 3. Patients ablated for supraventricular tachycardias—MCS and ablation details and outcomes.

https://doi.org/10.1371/journal.pone.0332597.t003

Discussion

This retrospective analysis illustrates the valuable role and feasibility of a catheter ablation procedure in the complex treatment of patients with CS and recurrent heart rhythm disorders.

According to the current guidelines, the implantation of an MCS should be considered in selected patients with CS when urgent hemodynamic stabilization is needed despite ongoing medical therapies [10,12]. The concrete device selection varies and depends on several factors including local availability and expertise as there is a lack of data for direct comparison [13]. Most of our patients (9/13) were treated with the Impella microaxial flow pump device. Recently, this approach has shown mortality benefit for patients with CS in the setting of a randomized trial [14].

Nowadays, the MCS are also being used more often during the catheter ablation, mainly for VTs, to improve the outcome [15]. According to the review by Kautzner et al., the MCS are used during the ablation in three different clinical scenarios: (1) pre-emptive use, (2) rescue mechanical support, and (3) bail-out ablation on MCS [16].

The pre-emptive or prophylactic use of MCS means that the patient is put on an MCS before the ablation because of the high risk of deterioration during the procedure. The MCS also potentially allows activation mapping of haemodynamically not tolerated tachycardias [16–18]. Interestingly, the prophylactic use of MCS in patients with structural heart disease undergoing catheter ablation was also associated with a significant reduction in postprocedural mortality or the need for heart transplantation [19].

The rescue approach refers to the situation of an acute deterioration during the ablation that requires urgent MCS implantation. In this setting, the VA ECMO is usually preferred. The prognosis of patients after the rescue MCS is generally poor, but this is mainly due to the serious underlying cause. However, data suggest that a modified rescue approach can be successfully used in intermediate-risk patients. Mascia et al. reported a case series of 10 patients undergoing VT ablation, in whom only vascular access with high-support leads was initially established, while the VA ECMO machine was prepared in the cath lab to enable rapid deployment if needed. Ultimately, only one patient required VA ECMO implantation, thereby avoiding unnecessary costs and risks [20].

The bail-out ablation is characterised by a situation when the catheter ablation is used to enable the MCS weaning. Patients analysed in this study therefore fit in this bail-out scenario. The data on bail-out ablation of ventricular arrhythmias in CS was reported by Ballout et al. in 2020. In this analysis of 21 consecutive patients, the aortic balloon pump was used most often. After the ablation, 17 subjects were successfully weaned off the MCS. In total, 6/21 (28,6%) patients died because of the persistent CS [21].

Interestingly, the published data on an SVT ablation in patients on MCS are scarce. In 2014, Cheruvu et al. reported a case of successful accessory pathway ablation in a patient with AV re-entrant tachycardia resulting in severe tachycardia-induced cardiomyopathy that required a VA ECMO implantation [22]. Later, Mantini et al. published a case series of 5 patients with CS who were ablated for SVT while being supported with different MCS [23]. To the best of our knowledge, other studies on this topic have not been published.

In our group, 3 out of 13 patients (23%) died during the 30-day period after the ablation. This is a lower mortality rate than usually reported for CS patients [13]. This can probably be explained by the selection bias. All patients were treated in the tertiary cardiac centre with the most advanced therapies available. It is also very probable that the most severe patients who deteriorated quickly were not included as they were not indicated for the ablation in spite of the presence of arrhythmia.

Despite the observed recurrence of the arrhythmia in 5/9 (56%) patients treated for VT, only two patients could not be successfully weaned off the MCS. This 7/9 (78%) successful weaning rate is comparable to the results published by Ballout el al. (17/21 ≈ 81%) [21].

In the SVT group, there was no recurrence of arrhythmia reported. This is not surprising as 3 out of 4 patients were treated with the AV node ablation – a procedure with a known higher success rate compared to a selective ablation for atrial fibrillation [24,25]. According to our experience, the “pace and ablate” approach seems to be a reasonable option for complicated patients with numerous comorbidities who suffer recurrent AF leading to a haemodynamic compromise.

It is well known that the use of an MCS is outweighed by the increased risk of complications. In our study, clinically significant complications due to the MCS implementation were reported in 7 of the 13 patients (54%). The complication rate of MCS found in the current literature varies substantially because of the non-uniformity of methodology and diverse complication criteria [26]. VA ECMO is usually connected with a higher complication rate than Impella [27]. To illustrate, the already mentioned randomized trials in CS patients reported a composite safety endpoint in 24% treated with Impella [14], and around 60% in patients treated with VA ECMO [28].

The ablation procedure itself seems to be relatively safe, even in this population of critically ill patients, according to both our results and the available data in literature [16,21,23]. The presence of an MCS; however, brings additional challenges to the operator. First, the availability of suitable cannulation sites may be limited. Also, navigating and controlling the catheters could be problematic in areas close to the ECMO cannula in the right atrium and especially in the left ventricle when Impella is used. The retrograde approach to the left ventricle may be another pitfall with Impella occupying the aortic ostium. Impella devices also cause electromagnetic interference that can significantly impair the performance of commonly used electroanatomic mapping systems, especially when higher flow (e.g., higher P-level) is used [29]. However, despite these limitations, all patients from our analysis treated with MCS underwent technically successful ablation.

Conclusion

Catheter ablation of refractory arrhythmias in CS patients treated by an MCS is a feasible approach to facilitate the MCS weaning process. Pace and ablate strategy seems reasonable in severe patients with refractory AF causing hemodynamic compromise when the chances to restore the sinus rhythm are low. The catheter ablation itself appears safe but complications of MCS are common. An individualized approach is necessary for the successful management of complicated CS patients.

Supporting information

Acknowledgments

The authors would like to thank Mgr. Zachary H. K. Kendall B. A. for the language editing.