Intervals don't really build endurance except in the untrained.
Heart rate is too variable for 1min intervals. If you can keep track of your HR and your cadence in a 1 min interval, you aren't going hard enough.
Just go all out 8-12 times with 3-5min of rest between each interval. Since you're just starting with intervals you'd do better in the 6-8, or 12-20min ranges.