1Universitätsklinikum Schleswig-Holstein Innere Medizin III mit den Schwerpunkten Kardiologie, Angiologie und internistische Intensivmedizin Kiel, Deutschland; 2Universitätsklinikum Schleswig-Holstein Klinik für Strahlentherapie Kiel, Deutschland; 3Universitätsklinikum Schleswig-Holstein Klinik für angeborene Herzfehler und Kinderkardiologie Kiel, Deutschland
Background
Catheter ablation (CA) is a well-established therapy for ventricular tachycardia (VT). However, in patients with both mechanic aortic and mitral valves, endocardial mapping and CA from the left ventricle (LV) is technically impossible. STereotactic Arrhythmia Radioablation (STAR) of Ventricular Tachycardia has been recently proposed as a novel treatment modality for patients with refractory VT, in whom CA has failed or is infeasible. Here, we report a unique case of STAR as a bailout therapy option for a patient with VT and mitral and aortic mechanical valves.
Case presentation
A 60-year-old woman was referred to our center due to recurrent symptomatic slow VTs with heart rates around 150 bpm (Fig.1A), despite antiarrhythmic therapy with beta blocker and amiodarone and terminated by either anti-tachycardia pacing or implantable cardioverter-defibrillator (ICD) shocks. The patient had a medical history of dilated cardiomyopathy with mild reduced ejection fraction and Marfan syndrome. She underwent aortic replacement (ascending aorta, arch, and descending aorta) due to aortic dissection as well as aortic and mitral valve replacement more than 20 years ago. The ECG morphology of the clinical VT suggested an LV exit site. Therefore, due to no-entry left ventricle endocardial CA was technically impossible. Because of previous cardiac operations, epicardial CA was possible only through thoracotomy, which was dismissed by the patient. The patient was then offered STAR as a bailout procedure within the RAVENTA trial.
For target volume (TV) definition, a contrast-enhanced ECG-gated computer tomography (CT) according to the InHEARTTM protocol was acquired. LV wall thickness calculation on the 3D segmentation revealed a fibrosis area in the inferolateral wall suggesting a slow-conducting re-entry VT isthmus in this region with the exit site to the lateral wall, which we used as TV (Fig.1B). For STAR treatment planning we performed a 4D respiratory CT to encompass residual target motion and transferred the TV to the radiotherapy planning systems, resulting in a TV of 5.5 ccm and a Planning Target Volume (PTV) of 39.9 ccm. A single fraction dose of 25 Gy was prescribed to the surrounding PTV with dose reduction towards esophagus and aorta and dose increase between the scar and the aortic root, to increase the fibrotic effects, according to the RAVENTA protocol (Fig.2). STAR was performed on a Stereotactic Linar Accelerator using Cone-Beam CT for image guidance and treatment time was 24.4 min with a beam-on time of 9.5 min.
In short-term follow-up (3 months), the patient remained free of VT and except mild nausea on the day after STAR, no further possible treatment related side effects were detected.
Conclusion
STAR could be a possible therapeutic approach for symptomatic recurrent ventricular tachycardia, refractory to antiarrhythmic drugs, in patients with a “no entry” left ventricle due to mechanical mitral and aortic valves. Further long-term follow-up is necessary.