Patient-Specific Quantification of Cardio-Respiratory Motion for Cardiac Radio-Ablation Treatment Planning

Background Cardiac radioablation is a new treatment for patients with refractory ventricular tachycardia (VT). The target for cardiac radioablation is subject to cardiorespiratory motion, the heart’s movement with breathing and cardiac contraction. Data regarding the magnitude of target cardiorespiratory motion are limited, but highly important for treatment planning. Objectives To assess cardiorespiratory motion amplitude by using ablation catheter geometrical data. Methods Electroanatomic mapping data of patients undergoing catheter ablation for VT at three academic centers were exported. The spatial position of the ablation catheter as a function of time while in contact with endocardium was analyzed and used to quantify cardiorespiratory motion. Results Forty-four patients with ischemic and non-ischemic cardiomyopathy and VT contributed 1,364 ablation lesions to the analysis. Average cardiac and respiratory excursion were 1.62 ±1.21mm and 12.12 ±4.10mm, respectively. Respiratory motion was on average 7.5 times greater than cardiac motion. Cardiorespiratory motion was greatest along the cranio-caudal axis (9.66 ±4.00mm). Regional variations with respect to respiratory and cardiac motion were observed: basal segments had smaller displacements vs. midventricular and apical segments. Patient characteristics (previous cardiac surgery, height, weight, body mass index and LV ejection fraction) had a statistically significant, albeit clinically moderate impact on cardiorespiratory motion. Conclusions Cardiorespiratory motion is primarily determined by respiratory displacement and is modulated by the location of the target and the patient’s biometric characteristics. The patient-specific quantification of cardiorespiratory motion may allow to decrease treatment volume and reduce radiation exposure of surrounding organs at risk while delivering the therapeutic dose to the target.