A case report of long-term successful stereotactic arrhythmia radioablation in a cardiac contractility modulation device carrier with giant left atrium, including a detailed dosimetric analysis

A Framework for Assessing the Effect of Cardiac and Respiratory Motion for Stereotactic Arrhythmia Radioablation Using a Digital Phantom With a 17-Segment Model: A STOPSTORM.eu Consortium Study

PURPOSE

The optimal motion management strategy for patients receiving stereotactic arrhythmia radioablation (STAR) for the treatment of ventricular tachycardia (VT) is not fully known. We developed a framework using a digital phantom to simulate cardiorespiratory motion in combination with different motion management strategies to gain insight into the effect of cardiorespiratory motion on STAR.

METHODS AND MATERIALS

The 4-dimensional (4D) extended cardiac-torso (XCAT) phantom was expanded with the 17-segment left ventricular (LV) model, which allowed placement of STAR targets in standardized ventricular regions. Cardiac- and respiratory-binned 4D computed tomography (CT) scans were simulated for free-breathing, reduced free-breathing, respiratory-gating, and breath-hold scenarios. Respiratory motion of the heart was set to population-averaged values of patients with VT: 6, 2, and 1 mm in the superior-inferior, posterior-anterior, and left-right direction, respectively. Cardiac contraction was adjusted by reducing LV ejection fraction to 35%. Target displacement was evaluated for all segments using envelopes encompassing the cardiorespiratory motion. Envelopes incorporating only the diastole plus respiratory motion were created to simulate the scenario where cardiac motion is not fully captured on 4D respiratory CT scans used for radiation therapy planning.

RESULTS

The average volume of the 17 segments was 6 cm3 (1-9 cm3). Cardiac contraction-relaxation resulted in maximum segment (centroid) motion of 4, 6, and 3.5 mm in the superior-inferior, posterior-anterior, and left-right direction, respectively. Cardiac contraction-relaxation resulted in a motion envelope increase of 49% (24%-79%) compared with individual segment volumes, whereas envelopes increased by 126% (79%-167%) if respiratory motion also was considered. Envelopes incorporating only the diastole and respiration motion covered on average 68% to 75% of the motion envelope.

CONCLUSIONS

The developed LV-segmental XCAT framework showed that free-wall regions display the most cardiorespiratory displacement. Our framework supports the optimization of STAR by evaluating the effect of (cardio)respiratory motion and motion management strategies for patients with VT.

Electrical storm management in structural heart disease

Electrical storm (ES) is a life-threatening condition characterized by at least three separate episodes of ventricular arrhythmias (VAs) over 24 h, each requiring therapeutic intervention, including implantable cardioverter defibrillator (ICD) therapies. Patients with ICDs in secondary prevention are at higher risk of ES and the most common presentation is that of scar-related monomorphic VAs. Electrical storm represents a major unfavourable prognostic marker in the history of patients with structural heart disease, with an associated two- to five-fold increase in mortality, heart transplant, and heart failure hospitalization. Early recognition and prompt treatment are crucial to improve the outcome. Yet, ES management is complex and requires a multidisciplinary approach and well-defined protocols and networks to guarantee a proper patient care. Acute phase stabilization should include a comprehensive clinical assessment, resuscitation and sedation management skills, ICD reprogramming, and acute sympathetic modulation, while the sub-acute/chronic phase requires a comprehensive heart team evaluation to define the better treatment option according to the haemodynamic and overall patient's condition and the type of VAs. Advanced anti-arrhythmic strategies, not mutually exclusive, include invasive ablation, cardiac sympathetic denervation, and, for very selected cases, stereotactic ablation. Each of these aspects, as well as the new European Society of Cardiology guidelines recommendations, will be discussed in the present review.