A system and method for determining the optimum dose of cryotreatment to an area of target tissue to achieve isolation based on the time to effect (TTE). The system may generally include a treatment device, a sensing device, and a processor programmed to calculate the optimum dose of cryotreatment, in seconds, based on TTE. The TTE may be based on electrical signals received by the processor from the sensing device. The processor may be further programmed to automatically terminate a cryoablation procedure when the optimum dose of cryotreatment has elapsed. The optimum dose of cryotreatment may be the time, in seconds, it takes to achieve isolation, which may be the time it takes for an area of tissue to reach approximately - 20 °C.