'feedback' function in MATLAB
Convert the impulse responses into z-domain transfer functions first. This can be done by using the tf function and entering a third argument (sampling time) along with the usual num and den. If unspecified, use -1. Then use the z-domain transfer functions in the usual way. Here is the code:

sys1_z = tf(sys1, 1, -1);
sys2_z = tf(sys2, 1, -1);
sys_fb = feedback(sys1_z, sys2_z);