Repeated stereotactic radioablation for recurrent ventricular tachycardia in a patient with lung cancer

STereotactic Arrhythmia Radioablation (STAR) is a novel treatment modality for patients with refractory ventricular tachycardia (VT) who fail standard therapies. This multidisciplinary approach involves cardiologists, electrophysiologists, radiation oncologists, and medical physicists [1]. STAR has been shown to significantly reduce VT burden; however, recurrences are common [2–4]. Longer follow-up and comparative studies are warranted to confirm this approach’s safety and long-term efficacy [5–6].

Presented herein is the case of a 68-year-old man with a history of ischemic heart disease and VT. In 2007 and 2009, he experienced ST-elevation myocardial infarctions treated with coronary angioplasty and drug-eluting stent implantation. In February 2021, after the first occurrence of VT, the patient received a single-chamber cardioverter-defibrillator (ICD), which was upgraded in November 2022 to a biventricular system with an additional subcutaneous electrode. Despite optimal pharmacotherapy, VT recurred, and the patient underwent two catheter ablations (CA) in August 2022 and January 2023.

In February 2023, the patient was admitted due to an electrical storm. Numerous recurrences of VT occurred despite medication with lidocaine, metoprolol, amiodarone, and flecainide. Ultimately, the VT was interrupted by the ICD and external electrical cardioversion. Coronary angiography revealed no changes requiring revascularization. The patient underwent two further CAs (one endocardial and one epicardial), both of which proved ineffective. After a multidisciplinary discussion and approval from the local ethics committee (NKBBN/140/2023), the decision was made to attempt STAR. On computed tomography (CT) performed for the purpose of radiotherapy planning, a suspicious, contrast-enhancing mass in the right pulmonary hilum was detected (Fig. 1A). The patient was diagnosed with squamous cell lung cancer. A ¹⁸fluorodeoxyglucose positron-emission tomography-CT revealed bone and liver metastases (Fig. 1B), and the tumor was staged as cT2aN2M1c (stage IVB). Considering the severity of VT and the ineffectiveness of other therapies, the decision was made to perform the STAR procedure, followed by palliative lung radiotherapy and chemotherapy (carboplatin, paclitaxel). STAR planning was performed using the CARTO^TM electroanatomical mapping system (Biosense Webster, CARTO 3, version 7; Fig. 1C). We used voltage maps, areas of late/fragmented potentials and pace mapping recorded during previous ablation procedures. The patient was able to undergo deep-inspiration breath hold radiotherapy planning, reducing the irradiated volume. STAR was performed with a single 25 Gy fraction (Fig. 1D–E). One week later, the patient underwent palliative radiotherapy to the hilar mass (25 Gy in five fractions).

Figure 1.

A contrast-enhanced CT scan for radiotherapy planning shows pathological mass in the right hilum (A). 18F-FDG PET-CT imaging shows multiple metastases in the bones and liver (B). Radiotherapy planning was performed using the CARTO electroanatomical mapping system (C), which was converted to CT images (D). The 17-segment model is a standardized myocardial segmentation to segment the left ventricle; the segments of LV irradiated during the first STAR (7, 8, 13, 17) are marked in blue, the segments of LV irradiated during the second STAR are marked in red (10, 15), and the segments irradiated during both STAR procedures (9, 14) are marked in violet (E). Healthy and nonirradiated myocardium from segment 6 of the left ventricle (F). Nonirradiated myocardium with pronounced fibrotic post-infarction scar and marked hypertrophy from segment 1 (G). Irradiated myocardium with an irregular fibrotic post-infarction scar and marked hypertrophy from segment 14 (H)

The frequency of VT recurrences declined shortly after STAR and resolved for nine months. In December 2023, the patient developed recurrent VT. An echocardiography revealed a left ventricle (LV) thrombus, precluding electrophysiological examination and another CA (Fig. 2). The local ethics committee approved another STAR attempt (KB/18/2024). The STAR target volume was indirectly determined by the morphology of QRS complexes during VT versus during pacing from the right ventricular and left ventricular (LV) lead, which indicated the substrate origination within the inferior LV wall (Fig. 1E). The treatment was designed as previously but considering the second STAR attempt and partially overlapping the planned target volume (Fig. 1E), the radiotherapy dose was reduced to 20 Gy.

Figure 2.

Thrombus in the apical segments of the left ventricle (arrows) visualized in a three-dimensional transthoracic echocardiography (GE VIVID E95 ultrasound system, Horten, Norway)

The patient was discharged home in good condition. Subsequent ICD controls showed no arrhythmias, and the LV ejection fraction improved from 20% to 30%. However, the patient died shortly after the second STAR due to cancer progression. An autopsy showed the fatal perforation of the bronchial wall by the tumor mass. The heart showed significant remodeling in the segments with arrhythmogenic areas subjected to radiotherapy. Irregular scarification and fibrosis was noted with compensatory cardiomyocyte hypertrophy (most probably reflecting the prior ischemic damage), but without the transmural fibrosis typically seen after CA (Fig. 1E–H). The present case shows the therapeutic potential of STAR even in a critical recurrent VT that does not respond to pharmacotherapy and CA. In this patient, the use of STAR significantly reduced the VT burden and contributed to the improvement of LV systolic function with a positive impact on the patient’s performance and quality of life. The case presented here is particularly significant because data on repeat cardiac radiotherapy for the treatment of arrhythmias is still very limited, with only a few case reports available [7–9]. An important aspect of this case is also the fact that it provides rare data on the histopathological presentation of hearts following radiotherapy, a subject for which available data is exceedingly scarce [10].

Further research is needed to identify optimal candidates for STAR, determine its safety, and identify potential long-term side effects. Although the initial published results are very promising, it is particularly concerning that there have been increasing reports of recurrences during longer follow-up periods [6]. A European consortium and prospective registry, STOPSTORM (https://www.stopstorm.eu/en), was established to address these questions [5]. This European Union funded initiative, aims to gather insights from most patients treated in Europe. Ultimately, this effort should result in the standardization of STAR guidelines.