This paper presents a novel multichannel level-crossing (MLC) ADC architecture aimed at recording atrial electrograms from multiple channels. The proposed architecture combines synchronous sampling with level-crossing (LC) quantisation to achieve activity dependent operation while recording from multiple channels simultaneously. In the proposed architecture the number of comparisons performed by the quantiser to reach a decision is dependent on the activity of the input signal and is 2-3.3 times lower than that in a conventional SAR ADC. The architecture uses one comparator and one reference level instead of two comparators and two reference levels as in conventional LC ADCs. The proposed architecture is modeled in VerilogA and is designed to be implemented in a standard 0.18 um CMOS process. The MLC ADC converts signals from 4 channels simultaneously and achieves an SFDR of 53.33 dB and an SNDR of 48.96 dB while consuming 9.32 μW of power from a 1.8 V power supply.