Hi,
i think short term effects will be rather small, while long-term effects will definitely lead to the organisms dead. Arrested mitosis means that tissue regeneration by stem cells will be impaired and this will first affect all tissues with a high cellular turn-over like the mucosal surfaces or the (red) blood cells. So one will be faced with major skin/ intestinal problems or anemia. Later on also other tissues will be damaged by missing renewal. However i don’t know if there are some other immediate effects also for non-dividing cells. Probably from a medial point of view the situation is far more complex. Hope it helped you somehow!