I an very deconditioned. i have a biventricular pacemaker. would it be better to walk at a slow pace for a longtime or short time fast paced?

Walking: Start out slowly and over time slowly increase your time and distance as tolerated.

Slow: Conditioning should start at a slow pace for a period that will not cause exhaustion or fatigue. This may take a while before increasing the time duration. In patients with significant cardiac impairment duration of exercise rather than intensity is better in improving functional status