This study from China investigated dose uncertainties induced by cardiorespiratory motion in proton therapy for arrhythmia. Twelve patients with refractory treated with photon were replanned using proton. The prescription was 25 Gy in a single fraction with requirements of V25 and D95 reaching 95% and 25 Gy. This study reported the proton plans of 11 patients in 4DCT and 6 in 4D cardiac CT failed to meet the prescription requirements. The mean V25 and D95 were 89.23% and 24.69 Gy in 4DCT and 94.35% and 24.99 Gy in 4DcCT. The authors concluded that complex cardiorespiratory motion could introduce dose uncertainties during IMPT; motion-encompassing techniques may mitigate but cannot entirely compensate for the dose discrepancies.